CN105160066A - Impact-resistant part simulation design method in view of forming damage - Google Patents

Abstract

The invention discloses an impact-resistant part simulation design method in view of forming damage to solve the problems in the prior art that subsequent simulation calculation precision is insufficient and part structure design is unreasonable due to neglecting of inherit properties of forming damage of different positions of a part during simulation design of the high-strength impact-resistant part of a vehicle body. The method comprises the steps of: establishing a thermal forming damage criterion of the high-strength impact-resistant part of the vehicle body; performing thermal forming simulation on the high-strength impact-resistant part of the vehicle body; and performing impact resistance evaluation on the high-strength impact-resistant part of the vehicle body. According to the method, factors such as forming temperature, forming rate, friction and the like are comprehensively considered and a forming damage value of the part after simulated forming serves as a factor considered in impact resistance evaluation of the part, so that the subsequent simulation calculation precision is remarkably improved, the repeated modification frequency is reduced, the reasonability of part structure design is ensured, and the difficulty in simulation design of the impact-resistant part and the requirements on designers are greatly lowered.

Description

Consider the crashworthiness part emulation design method damaged that is shaped

Technical field

The present invention relates to vehicle body high strength crashworthiness part, or rather, the present invention relates to a kind of vehicle body high strength crashworthiness part emulation design method considering shaping damage.

Background technology

In recent years, energy crisis and environmental problem make Lightweight Technology become the focus of automobile industry.How under the prerequisite ensureing vehicle body minibus, realize the hot issue that body lightening becomes lightweight field.Superhigh intensity boron steel is with advantages such as its high loss of weight potentiality, high collision energy-absorbing, high-fatigue strength and low degree anisotropy, become the main material of auto industry, be widely used in vehicle body crashworthiness part, as: on A/B/C post, sill strip, side girders, door anti-collision joist.But along with the raising of armor plate strength, its forming property is corresponding deterioration also, employing conventional ones forming technology can produce the problems such as resilience is serious, forming difficulty, easily cracking.For overcoming the problems referred to above, plow-steel hot forming techniques arises at the historic moment, its detailed process is: boron steel is heated to about 900 DEG C, microstructure is made to be converted into uniform austenite by ferrite+pearlite, then with drawing in the mould of cooling system, pressurize rapid quenching cooling simultaneously, makes austenite change martensite into completely, increases substantially part strength.

Along with computer simulation technique reaches its maturity, people start the method design vehicle body high strength crashworthiness part utilizing numerical simulation, and its design process is mainly divided into two steps: the assessment of part crashworthiness after the heat forming processes of simulation vehicle body high strength crashworthiness part and forming simulation.Present stage, emulation technology can the coupling of stress-phase transformation-temperature three suffered by plate in the actual forming process of simulate, can obtain the part model after forming simulation, it can dope the stress distribution, phase composition, Temperature Distribution, thickness distribution etc. of the rear part of actual shaping more exactly.But actual heat forming processes Dislocations density changes with shaping, cause material to produce microlesion (Micro-v oid and micro-crack), it develops and expansion produces fracture failure, can produce a very large impact part usability.And after forming simulation part crashworthiness evaluation stage, often because have ignored the otherness of shaping " damage " and the different parts degree of injury produced in part heat forming processes, think that whole part is desirable martensitic phase material, and affect the precision of subsequent simulation calculating, even because excessively high have estimated the crashworthiness of the rear part that is shaped in emulation, the generation of unreasonable structural design in actual production can be caused.

Therefore, a kind of method is needed thermoforming damage to be taken into account evaluation stage by the crashworthiness after vehicle body high strength crashworthiness part forming simulation, improve the Evaluation accuracy of its crashworthiness, strengthen vehicle body high strength crashworthiness part design of Simulation to the directive significance of actual design, the vehicle body high strength crashworthiness part of actual design is made more easily to reach design object requirement, thus minimizing test number (TN), shorten the construction cycle, reduce cost of development.

Summary of the invention

Ignore part different parts when technical matters to be solved by this invention is and overcomes vehicle body high strength crashworthiness part design of Simulation that prior art exists to be shaped the not enough and irrational problem of structural design of fittings of the subsequent simulation computational accuracy that causes of damage inherited characteristics, provide a kind of crashworthiness part emulation design method considering shaping damage, concrete technical scheme is as follows:

Consider the crashworthiness part emulation design method damaged that is shaped, it is characterized in that step is as follows:

Step one, set up vehicle body high strength crashworthiness part thermoforming damage criterion, detailed process is:

1) material at high temperature one directional tensile test

Hot modeling test machine is utilized to carry out a series of high temperature one directional tensile test to boron steel test specimen, utilize spot welder that one end of K type thermocouple wire (1) is welded in the central authorities of each test specimen (2) upper surface before test, K type thermocouple wire (1) other end keeps freely discharging, first test specimen (2) is clamped in the fixture of hot modeling test machine in test, one end that K type thermocouple wire (1) freely discharges is connected with hot modeling test machine simultaneously, subsequently, process is vacuumized to hot modeling test machine inner space, resistance heating manner is utilized to realize the heating process of test specimen (2), then by regulating the cooling velocity of compressed-air actuated flow control test specimen (2) in cooling procedure, concrete testing program is as follows:

(1) test specimen (2) is incubated 3min with after the heating rate to 925 of 5 DEG C/s DEG C, guarantees the microstructure complete austenitizing of test specimen (2);

(2) with the cooldown rate of 50 DEG C/s make test specimen (2) be down to successively deformation temperature 600 DEG C, 700 DEG C, 800 DEG C, and be incubated under each deformation temperature 5s make test specimen (2) homogeneous temperature stablize;

(3) at deformation temperature 600 DEG C, 700 DEG C, 800 DEG C and the deformation strain rate 0.01s of setting ^-1, 0.1s ^-1, 1s ^-1, 10s ^-1under test specimen (2) is stretched, until rupture failure, after fracture, air cooling is carried out to test specimen (8) after the stretching obtained, in whole drawing process, hot modeling test machine can record that load changes in time, the time dependent curve of temperature simultaneously, whole high temperature one directional tensile test comprises 12 groups of test conditions that 3 deformation temperatures and 4 deformation strain rates are combined into, and is respectively: deformation temperature 600 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 600 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 600 DEG C and deformation strain rate 1s ^-1, deformation temperature 600 DEG C and deformation strain rate 10s ^-1, deformation temperature 700 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 700 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 700 DEG C and deformation strain rate 1s ^-1, deformation temperature 700 DEG C and deformation strain rate 10s ^-1, deformation temperature 800 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 800 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 800 DEG C and deformation strain rate 1s ^-1, deformation temperature 800 DEG C and deformation strain rate 10s ^-1carry out a high temperature tension test under often organizing test condition, time dependent curve F (t) of load recorded by hot modeling test machine in test is scaled the time dependent curve σ of nominal stress of test specimen (2) according to formula (1) _nomt (), time dependent curve Δ L (t) of gauge length segment length of the test specimen (2) recorded by ccd video camera (3) is scaled the time dependent curve ε of gauge length section apparent strain of test specimen (2) according to formula (2) _nomt (), according to formula (3) by time dependent for the nominal stress of test specimen (2) curve σ _nomt () is scaled the time dependent curve σ of true stress of test specimen (2) _truet (), according to the gauge length section apparent strain time dependent curve ε of formula (4) by test specimen (2) _nomt () is scaled the time dependent curve ε of gauge length section logarithmic strain of test specimen (2) _truet (), and the time variable t in cancellation two curve, with logarithmic strain ε _truefor independent variable, true stress σ _truefor dependent variable, obtain the true stress and strain curve σ under each test condition _true(ε _true):

${\mathrm{\σ}}_{nom}\left(t\right)=\frac{F\left(t\right)}{A_0}---\left(1\right)$

In formula: F (t) is the time dependent curve of load; A ₀for specimen equidistance line marking section original cross-sectional area; σ _nomthe time dependent curve of t nominal stress that () is test specimen.

${\mathrm{\ϵ}}_{nom}\left(t\right)=\frac{\mathrm{\Δ}L\left(t\right)}{L_0}---\left(2\right)$

In formula: the time dependent curve of gauge length segment length that Δ L (t) is test specimen; L ₀for specimen equidistance line marking section original length; ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen.

σ _true(t)＝σ _nom(t)(1+ε _nom(t))(3)

In formula: σ _nomthe time dependent curve of t nominal stress that () is test specimen; ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen; σ _truethe time dependent curve of t true stress that () is test specimen.

ε _true(t)＝ln(1+ε _nom(t))(4)

In formula: ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen; ε _truethe t time dependent curve of gauge length section logarithmic strain that () is test specimen.

2) constitutive equation based on the damage that is shaped is set up:

(1) set up the constitutive equation based on the damage that is shaped, the damage of material during to consider thermoforming, expression is as follows:

${\stackrel{\·}{\mathrm{\ϵ}}}_e^P={\left(\frac{{\mathrm{\σ}}_e/(1-f_{d1})-H-k}{K}\right)}^{n_1}{(1-f_{d1})}^{-{\mathrm{\γ}}_1}---\left(5\right)$

${\stackrel{\·}{\mathrm{\ϵ}}}_{ij}^P=\frac{3S_{ij}}{2{\mathrm{\σ}}_e}{\stackrel{\·}{\mathrm{\ϵ}}}_e^P---\left(6\right)$

$\stackrel{\·}{\stackrel{\‾}{\mathrm{\ρ}}}=A(1-\stackrel{\‾}{\mathrm{\ρ}})\left|{\stackrel{\·}{\mathrm{\ϵ}}}_e^P\right|-C{\stackrel{\‾}{\mathrm{\ρ}}}^{n_2}---\left(7\right)$

$H=B{\stackrel{\‾}{\mathrm{\ρ}}}^{n_0}---\left(8\right)$

${\stackrel{\·}{f}}_{d1}={\mathrm{D\σ}}_e\left|{\stackrel{\·}{\mathrm{\ϵ}}}_e^P\right|/{(1-f_{d1})}^{{\mathrm{\γ}}_2}---\left(9\right)$

${\mathrm{\σ}}_{ij}=D_{ijkl}(1-f_{d1})({\mathrm{\ϵ}}_{kl}^T-{\mathrm{\ϵ}}_{kl}^P)---\left(10\right)$

$D_{ijkl}=\frac{E}{2(1+v)}({\mathrm{\δ}}_{il}{\mathrm{\δ}}_{jk}+{\mathrm{\δ}}_{ik}{\mathrm{\δ}}_{jl})+\frac{Ev}{(1+v)(1-2v)}{\mathrm{\δ}}_{ij}{\mathrm{\δ}}_{kl}---\left(11\right)$

In formula: it is equivalent plastic strain rate during shaping; σ _eit is equivalent stress during shaping; The strain hardening that H is caused by dislocation when being and being shaped; Shaping damage variable f _d1, its variation range is 0 ~ 1, f _d1when representing shaping when=0, material does not damage, f _d1material complete failure when representing shaping when=1; plastic strain rate component during for being shaped; S _ijdeviatoric stress component during for being shaped; ρ _ifor the dislocation desity under material original state, ρ _mmaterial accessible dominant bit dislocation density during for being shaped, and ρ _i≤ ρ≤ρ _m, namely σ _ijit is stress tensor component during shaping; it is overall strain component of tensor during shaping; it is plastic strain component of tensor during shaping; D _ijklit is quadravalence Stiffness Tensor component; E is Young modulus; υ is Poisson ratio; δ _ijfor the Kronecker factor, subscript i, j, k, l variation range are 1 ~ 3, repeat subscript and follow Einstein's summation convention.

Parameter k, K, n ₁, B, C, D, E be the material parameter with temperature correlation, be defined as follows:

k＝k ₀exp(Q _k/RT)(12)

K＝K ₀exp(Q _K/RT)(13)

n ₁＝n ₁₀exp(Q _n/RT)(14)

B＝B ₀exp(Q _B/RT)(15)

C＝C ₀exp(-Q _C/RT)(16)

D＝D ₀exp(Q _D/RT)(17)

E＝E ₀exp(Q _E/RT)(18)

In formula: R is universal gas constant; T is temperature; Q is activation energy.

(2) material parameter in constitutive equation is determined:

First, set up the objective function of Solve problems, then objective function application Evolutionary Programming Algorithm is optimized, finally determines the material parameter in constitutive equation, here, need the material parameter determined always to have 20, be followed successively by: A, n ₂, γ ₁, γ ₂, k ₀, n ₀, K ₀, n ₁₀, B ₀, C ₀, D ₀, E ₀, Q _k, Q _k, Q _n, Q _b, Q _c, Q _d, Q _e, R.

Objective function is set up according to the distance between matched curve and test figure:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{w}_i{r}_i^2=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{w}_i({\mathrm{\Δ\σ}}^2+{\mathrm{\Δ\ϵ}}^2)=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{w}_i({({\mathrm{\σ}}_i^c-{\mathrm{\σ}}_i^e)}^2+{({\mathrm{\ϵ}}_i^c-{\mathrm{\ϵ}}_i^e)}^2)---\left(19\right)$

In formula: f (x) forms vector x=(A, n about 20 unknown material parameters ₂..., Q _e, R) real-valued function; N is the total volume of test figure; w _iit is the weighted value of the i-th data point; be respectively the stress and strain value that i-th test figure is corresponding; be respectively the stress and strain value in the matched curve corresponding with i-th test figure for making to test figure convergence between matched curve strain regions, will add f (x) to obtain:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{w}_i({({\mathrm{\σ}}_i^c-{\mathrm{\σ}}_i^e)}^2+{({\mathrm{\ϵ}}_i^c-{\mathrm{\ϵ}}_i^e)}^2)+W{({\mathrm{\ϵ}}_n^c-{\mathrm{\ϵ}}_n^e)}^2---\left(20\right)$

In formula: W is weight coefficient;

For reducing the difficulty of determining weighted value in actual use procedure and overcoming the inconsistent problem of ess-strain unit, the final objective function set up is as follows:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}(w{1}_i{\left(\ln \right(\frac{{\mathrm{\σ}}_i^c({\mathrm{\ϵ}}_i^e{\mathrm{\ϵ}}_n^c/{\mathrm{\ϵ}}_n^e)}{{\mathrm{\σ}}_i^e}\left)\right)}^2+w{2}_i{\left(\ln \right(\frac{{\mathrm{\ϵ}}_i^c({\mathrm{\ϵ}}_i^e{\mathrm{\ϵ}}_n^c/{\mathrm{\ϵ}}_n^e)}{{\mathrm{\ϵ}}_i^e}\left)\right)}^2)+{({\mathrm{\ϵ}}_n^c-{\mathrm{\ϵ}}_n^e)}^2---\left(21\right)$

In formula:

$w{1}_i={\mathrm{n\ϵ}}_i^e/\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\ϵ}}_i^e(w{1}_1+w{1}_2+...+w{1}_n=n)---\left(22\right)$

$w{1}_2={\mathrm{n\ϵ}}_i^e/\underset{i=1}{\overset{n}{\Σ}}{\mathrm{\ϵ}}_i^e(w{2}_1+w{2}_2+...+w{2}_n=n)---\left(23\right)$

Adopt the tachytelic evolution planning algorithm improved to be optimized the objective function set up, determine all material parameter, Evolutionary Programming Algorithm as biotic population, by sudden change, is selected objective function to produce population of new generation; Repeat this process, until obtain the evolution time limit of population or the regulation meeted the requirements, detailed evolutional programming is the process of an iteration:

[1] get iteration count k=1, a stochastic generation μ population, namely stochastic inputs μ group vector is to (x _i, η _i), wherein η _ifor evolutional programming adaptive strategy parameter, i=1,2,3 ..., μ;

[2] for each voxel vector to (x _i, η _i), calculate f (x _i);

[3] for each parent vector to (x _i, η _i), generate two filial generation vectors pair with wherein:

$\left\{\begin{array}{c}{x}_i^1\left(j\right)=x_i\left(j\right)+{\mathrm{\η}}_i\left(j\right)N_j(0,1)\\ x_i^2\left(j\right)=x_i\left(j\right)+{\mathrm{\η}}_i\left(j\right){\mathrm{\δ}}_j\\ {\mathrm{\η}}_i^1\left(j\right)={\mathrm{\η}}_i\left(j\right)\exp \left({\mathrm{\τ}}^{1}N\right(0,1)+{\mathrm{\τN}}_j(0,1))\end{array}\right.---\left(24\right)$

Calculate and compare with size, get both vectors pair corresponding to smaller, be designated as (x _i', η _i'), wherein x _i(j), x _i' (j), η _i(j), η _i' (j) be respectively vector x _i, x _i', η _i, η _i' a jth component (j=1,2 ..., n, n are the number of material parameter to be optimized); N (0,1) is the random number of obeying one dimension standardized normal distribution; N _j(0,1) corresponds to the random number of a jth component for obeying one dimension standardized normal distribution; δ _jthe random number of a jth component is corresponded to for obeying Cauchy's distribution; Parameter τ ¹get respectively with τ with the density function of standardized normal distribution and Cauchy's distribution is respectively:

$\begin{array}{cc}{f}_N\left(x\right)=\frac{1}{\sqrt{2n}}{e}^{-x^2/2},& -\mathrm{\&infin;}<x<+\mathrm{\&infin;}\end{array}---\left(25\right)$

$\begin{array}{cc}{f}_{\mathrm{\&delta;}}\left(x\right)=\frac{1}{\mathrm{\&pi;}}\frac{1}{1+x^2},& -\mathrm{\&infin;}<x<+\mathrm{\&infin;}\end{array}---\left(26\right)$

[4] for all i=1,2,3 ..., μ, by all parent vectors to (x _i, η _i) and filial generation vector to (x _i', η _i') integrally, take out q vector pair, then, by any one vector of all parents and filial generation vector centering pair with q the vector taken out to making comparisons, relatively vector is to corresponding target function value, if this vector is to being less than the some of q vector centering, then this vector adds 1 to score, the right top score of all vectors is q, so minimum that to be divided into 0;

[5] the highest μ of a score vector pair is selected, as the parent vector pair of next iteration from 2 μ vector centerings;

[6] judge whether iteration termination condition meets; If do not met, then k=k+1, and repeat said process.

(3) software simulating of damage Constitutive Equation

Utilizing Fortran language by determining that the shaping damage Constitutive Equation of material parameter is written as Ls-dyna User Defined material subprogram, being embedded in finite element software Ls-dyna by User Defined material subprogram interface.

Step 2, vehicle body high strength crashworthiness part thermoforming simulation, detailed process is:

1) utilize Hypermesh finite element software to set up vehicle body high strength crashworthiness part thermoforming realistic model, the object in model comprises plate (6), punch (4), die (7) and blank holder (5);

2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute, and define the thickness t of each object wherein, and punch (4), die (7) and blank holder (5) adopt rigid body physical material, and define the density p of each object, elastic modulus E and Poisson ratio υ wherein, plate (6) then adopts the above-mentioned User Defined physical material based on the damage that is shaped, and all objects all adopt isotropy hot material, and define specific heat capacity HC and the heat-conduction coefficient TC of each object wherein;

3) contact relation between each object in model is set, define temperature field that each object has, kinetic characteristic, constraint condition and model calculate needed for control card;

4) utilize Ls-dyna software to solve vehicle body high strength crashworthiness part thermoforming realistic model, obtain the part model after being shaped and be shaped damage cloud atlas and thickness distribution cloud atlas.

Step 3: vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation:

1) mechanics operating characteristic database

(1) material at high temperature damage test

Ls-dyna software is utilized to carry out virtual test to test specimen (2), whole test specimen (2) adopts shell unit cross section attribute, and define its thickness t wherein, adopt User Defined physical material and isotropy hot material that considering is shaped damages, and define its specific heat capacity HC and heat-conduction coefficient TC wherein, meanwhile, at test specimen (2) zone line definition l ₀the samming section that=25mm is long, steady temperature field is applied in this section, in region, this section of left and right sides is then according to actual tests, test specimen (2) Temperature Distribution applies corresponding temperature field, during virtual test, whole 6 degree of freedom of constraint test specimen (2) left end node, time dependent forced displacement is vertically applied at right-hand member, guarantee that samming section is out of shape with constant rate of strain, samming section is made to get typical test condition in test: forming temperature 750 DEG C, deformation strain rate 0.1s ^-1.Under this condition, carry out a series of virtual test, make the shaping impairment value of unit in samming section reach target shaping impairment value 0, α respectively ₁, α ₂..., α _n, namely obtain a series of samming section and there is test specimen (8) after the stretching of differing formed impairment value, and measure the changing value of each test specimen (2) samming segment length respectively

Testing machine is utilized to carry out actual tests to test specimen (2), actual test conditions is identical with virtual test, ccd video camera (3) is utilized to take in test, and pass through the deflection of ARAMIS optical skew system Real-time Feedback test specimen (2) samming section, when the change of each test specimen (2) samming segment length reaches respectively time, stop stretching, now, in actual tests, samming section place material reaches and equal degree of injury in virtual test, same samming segment length changing value Repeated m time test in test.Subsequently, room temperature is cooled to each test specimen (2) samming section rapid quenching, namely obtains a series of samming section and there is test specimen (8) after the stretching of martensitic phase after the quenching of differing formed impairment value.

(2) test specimen processing

Linear cutter is carried out to test specimen (8) after the stretching after a series of quenchings obtained in material at high temperature damage test, obtain for material room temperature one directional tensile test test specimen (9) used, subsequently, with fine sandpaper, slightly polished in each surface of all sub-test specimens (9), remove oxide skin above, and the minimum sectional area of rear each sub-test specimen (9) the gauge length section of record polishing, as the original cross-sectional area A of following material room temperature one directional tensile test neutron test specimen (9) gauge length section ₀.

(3) material room temperature one directional tensile test

Electronic universal tester is utilized to carry out the one directional tensile test of the different military service rate of strain of m kind to the sub-test specimen (9) that the samming section obtained in material at high temperature damage test has a different impairment value, all sub-test specimens (9) all at room temperature stretch until rupture, test time dependent curve F (t) of chance record load in whole drawing process, and it is scaled the time dependent curve σ of nominal stress of sub-test specimen (9) according to formula (1) _nom(t), and adopt stretching extensometer to measure time dependent curve Δ L (t) of gauge length segment length of sub-test specimen (9), and it is scaled the time dependent curve ε of gauge length section apparent strain of sub-test specimen (9) according to formula (2) _nomt (), according to formula (3) by time dependent for the nominal stress of sub-test specimen (9) curve σ _nomt () is scaled the time dependent curve σ of true stress of sub-test specimen (9) _truet (), according to the gauge length section apparent strain time dependent curve ε of formula (4) by sub-test specimen (9) _nomt () is scaled the time dependent curve ε of gauge length section logarithmic strain of sub-test specimen (9) _truet (), and the time variable t in cancellation two curve, with logarithmic strain ε _truefor independent variable, true stress σ _truefor dependent variable, obtain the true stress and strain curve σ of each test specimen (9) _true(ε _true).Finally, the true stress and strain curve σ of test specimen (9) of differing formed impairment value, different military service rate of strain must be had _true(ε _true), for setting up the following military service constitutive equation considering shaping damage.

2) the military service constitutive equation considering shaping damage is set up

Set up and consider the military service constitutive equation damaged that is shaped, expression is as follows:

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p={\left(\frac{\mathrm{\&sigma;}/(1-f_{d2})-F{{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s}^{n_a}-y}{Y}\right)}^{n_c}{\left(\frac{1}{1-f_{d2}}\right)}^{{\mathrm{\&gamma;}}_3}---\left(27\right)$

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_{ij}^p=\frac{3S_{s-ij}}{2\mathrm{\&sigma;}}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p---\left(28\right)$

${\stackrel{\&CenterDot;}{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}}_s=Z(1-{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s)\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right|-C{{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s}^{{\mathrm{\&gamma;}}_4}---\left(29\right)$

${\stackrel{\&CenterDot;}{f}}_{d2}={\mathrm{\&beta;}}_1\left(\mathrm{\&sigma;}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right){f_{d2}}^{{\mathrm{\&gamma;}}_5}+\frac{{\mathrm{\&beta;}}_2{\left({\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right)}^{{\mathrm{\&gamma;}}_6}\cosh \left({\mathrm{\&beta;}}_3{\mathrm{\&epsiv;}}^p\right)}{{(1-f_{d2})}^{{\mathrm{\&gamma;}}_7}}---\left(30\right)$

${\mathrm{\&sigma;}}_{s-ij}=D_{s-ijkl}(1-f_{d2})({\mathrm{\&epsiv;}}_{kl}^t-{\mathrm{\&epsiv;}}_{kl}^p)---\left(31\right)$

$D_{s-ijkl}=\frac{L}{2(1+v)}({\mathrm{\&delta;}}_{il}{\mathrm{\&delta;}}_{jk}+{\mathrm{\&delta;}}_{ik}{\mathrm{\&delta;}}_{jl})+\frac{Lv}{(1+v)(1-2v)}{\mathrm{\&delta;}}_{ij}{\mathrm{\&delta;}}_{kl}---\left(32\right)$

In formula: it is equivalent plastic strain rate during military service; Equivalent stress when σ is military service; Military service damage variable f _d2, its variation range is 0 ~ 1, f _d2when representing military service when=0, material is not on active service damage, f _d2material complete failure when representing military service when=1; plastic strain rate component during for being on active service; S _s-ijdeviatoric stress component during for being on active service; ρ _sifor the dislocation desity of front material of being on active service, ρ _smmaterial accessible dominant bit dislocation density during for being on active service, and ρ _si≤ ρ _s≤ ρ _sm, namely σ _s-ijit is stress tensor component during military service; it is overall strain component of tensor during military service; it is plastic strain component of tensor during military service; D _s-ijklit is quadravalence Stiffness Tensor component; L is Young modulus; υ is Poisson ratio; δ _ijfor the Kronecker factor, subscript i, j, k, l variation range are 1 ~ 3, repeat subscript and follow Einstein's summation convention.

Parameter y, Y, F, G, L, β ₁, β ₂, β ₃, γ ₅, γ ₆be damage relevant material parameter to shaping, be defined as follows:

y＝y ₀exp(W _y/f _d1)(33)

Y＝Y ₀exp(W _Y/f _d1)(34)

F＝F ₀exp(W _F/f _d1)(35)

G＝G ₀exp(-W _G/f _d1)(36)

L＝L ₀exp(W _L/f _d1)(37)

${\mathrm{\&beta;}}_1={\mathrm{\&beta;}}_{10}\exp (W_{{\mathrm{\&beta;}}_1}/f_{d1})---\left(38\right)$

${\mathrm{\&beta;}}_2={\mathrm{\&beta;}}_{20}\exp (W_{{\mathrm{\&beta;}}_2}/f_{d1})---\left(39\right)$

${\mathrm{\&beta;}}_3={\mathrm{\&beta;}}_{30}\exp (W_{{\mathrm{\&beta;}}_3}/f_{d1})---\left(40\right)$

${\mathrm{\&gamma;}}_5={\mathrm{\&gamma;}}_{50}\exp (W_{{\mathrm{\&gamma;}}_5}/f_{d1})---\left(41\right)$

${\mathrm{\&gamma;}}_6={\mathrm{\&gamma;}}_{60}\exp (W_{{\mathrm{\&gamma;}}_6}/f_{d1})---\left(42\right)$

Determine to consider to be shaped the military service Material Parameter in Constitutive Equation of damage and military service constitutive equation software simulating method used with set up identical based on method used during shaping damage Constitutive Equation, and here, need the material parameter determined always to have 25, be followed successively by: Z, γ ₃, γ ₄, γ ₇, n _c, y ₀, Y ₀, F ₀, G ₀, L ₀, β ₁₀, β ₂₀, β ₃₀, γ ₅₀, γ ₆₀, W _y, W _y, W _f, W _g, W _l,

3) vehicle body high strength crashworthiness part virtual test

(1) utilize Hypermesh software to set up vehicle body high strength crashworthiness part virtual test model, the object in virtual crushing test model comprises: rigidity obstacle (10), conquassation thin-walled crashworthiness part (11); Object in virtual bending test model comprises: No. 1 rigidity circle rolls (12), bending thin-walled crashworthiness part (13), No. 2 rigidity circles roll (14), No. 3 rigidity circles roll (15);

(2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute, the thickness distribution of part after the thickness distribution succession thermoforming of crashworthiness part, rigidity obstacle (10) and all rigidity circle roll and all adopt rigid body physical material, and defining the density p of each object, elastic modulus E and Poisson ratio υ wherein, conquassation thin-walled crashworthiness part (13) and bending thin-walled crashworthiness part (13) then adopt the User Defined of damage of considering to be shaped to be on active service this structure physical material;

(3) contact relation between each object in model is set, defines the control card needed for the calculating of the kinetic characteristic of each object, constraint condition and model;

(4) Ls-dyna software is utilized to solve vehicle body high strength crashworthiness part virtual test model, export the time dependent deformation tendency cloud atlas of crashworthiness part, contact force curve and energy absorption curve, and contrast with design object value, to confirm whether this crashworthiness part meets designing requirement.

Compared with prior art the beneficial effect of this method is:

1. when the crashworthiness part emulation design method considering that shaping damages of the present invention overcomes the vehicle body high strength crashworthiness part design of Simulation of prior art existence, to be shaped the not enough and irrational problem of structural design of fittings of the subsequent simulation computational accuracy that causes of damage inherited characteristics because ignoring part different parts, forming temperature will have been considered, shaping rate, the factor considered when " shaping impairment value " after the part forming simulation of the factors such as friction is assessed as part crashworthiness, significantly improve the precision that subsequent simulation calculates, decrease the number of times repeatedly revised, ensure that the rationality of structural design of fittings.

2. the crashworthiness part emulation design method that consideration shaping of the present invention damages establishes the mechanics operating characteristic database under the differing formed impairment value of boron steel, different military service rate of strain, apply this mechanics operating characteristic database and can set up the constitutive equation considering differing formed damage and military service rate of strain, the military service performance of material after this constitutive equation accurately can show and be shaped.

3. the consideration shaping damage of setting up in the crashworthiness part emulation design method that consideration shaping of the present invention damages and the constitutive equation of military service rate of strain can be embedded in simulation analysis software, are convenient to designer and call when crashworthiness part design of Simulation.The change procedure of complexity when making designer without the need to understanding actual parts thermoforming, just can carry out the distribution of military service performance based on the shaping impairment value at each position of part after thermoforming simulation analysis, ensure the confidence level of part subsequent simulation analysis result, greatly reduce the difficulty of crashworthiness part design of Simulation and the requirement to designer.

Accompanying drawing explanation

Fig. 1 is the process flow diagram considering the crashworthiness part emulation design method of shaping damage of the present invention;

Fig. 2 be in the crashworthiness part emulation design method of damage of considering to be shaped of the present invention step one carry out when setting up vehicle body high strength crashworthiness part thermoforming damage criterion material at high temperature one directional tensile test adopt the schematic diagram of device;

The test specimen schematic diagram that material at high temperature one directional tensile test adopts is carried out when step one sets up vehicle body high strength crashworthiness part thermoforming damage criterion in the crashworthiness part emulation design method that Fig. 3 is consideration shaping damage of the present invention;

The schematic diagram of the knearest neighbour method adopted when step one sets up vehicle body high strength crashworthiness part thermoforming damage criterion in the crashworthiness part emulation design method that Fig. 4 is consideration shaping damage of the present invention;

The schematic diagram of model used when Fig. 5 is step 2 vehicle body high strength crashworthiness part thermoforming simulation in the crashworthiness part emulation design method of consideration shaping damage of the present invention;

When Fig. 6 a is step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention, material at high temperature damages the schematic diagram of test specimen in virtual test;

When Fig. 6 b is step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention, material at high temperature damages in virtual test the schematic diagram of the rear test specimen that stretches;

When Fig. 7 a is step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention, material at high temperature damages the schematic diagram of test specimen in actual tests;

When Fig. 7 b is step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention, material at high temperature damages in actual tests the schematic diagram of the rear test specimen that stretches;

The process flow diagram of material at high temperature damage test when Fig. 8 is step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention;

The schematic diagram of material room temperature one directional tensile test neutron test specimen when Fig. 9 is step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention;

The virtual crushing test schematic diagram that Figure 10 utilizes Hypermesh software to set up when being step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention;

The virtual bending test schematic diagram that Figure 11 utilizes Hypermesh software to set up when being step 3 vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation in the crashworthiness part emulation design method of consideration shaping damage of the present invention;

Figure 12 is the structural representation considering U-shaped cross section high-strength vehicle door collision prevention girders in the crashworthiness part emulation design method embodiment of shaping damage of the present invention;

Figure 13 considers the comparison diagram with the high-strength vehicle door collision prevention girders emulation design method in U-shaped cross section when damaging of not considering to be shaped in embodiment;

Figure 14 a is the true stress and strain curve figure of Ovshinsky figure boron steel when temperature is 700 DEG C under different strain rate in the crashworthiness part emulation design method embodiment of consideration shaping damage of the present invention;

Figure 14 b is that in the crashworthiness part emulation design method embodiment of consideration shaping damage of the present invention, Ovshinsky figure boron steel is 0.1s in rate of strain ^-1time different temperatures under true stress and strain curve figure;

The temperature variant specific heat capacity that in the crashworthiness part emulation design method embodiment that Figure 15 is consideration shaping damage of the present invention, boron steel plate adopts and the curve map of heat-conduction coefficient;

Figure 16 is the geneva figure boron steel having a different thermoforming impairment value in the crashworthiness part emulation design method embodiment of damage of considering to be shaped of the present invention is 0.01s in rate of strain ^-1time true stress and strain curve figure;

Figure 17 is the schematic diagram of the U-shaped cross section high-strength vehicle door collision prevention girders adopting Ls-dyna software to obtain in the crashworthiness part emulation design method embodiment of damage of considering to be shaped of the present invention when producing 60 ° of flexural deformation;

Figure 18 considers the comparison diagram with contact force curve when the U-shaped cross section high-strength vehicle door collision prevention girders damaged of not considering to be shaped is virtual and actual flexion is tested in embodiment;

Figure 19 considers the comparison diagram with energy absorption curve when the U-shaped cross section high-strength vehicle door collision prevention girders damaged of not considering to be shaped is virtual and actual flexion is tested in embodiment.

In figure: 1.K type thermocouple wire, 2. test specimen, 3.CCD video camera, 4. punch, 5. blank holder, 6. plate, 7. die, the sub-test specimen of test specimen 9., 10. rigidity obstacle after 8. stretching, 11. conquassation thin-walled crashworthiness parts; No. 12.1 rigidity circles roll, 13. bending thin-walled crashworthiness parts, and No. 14.2 rigidity circles roll, and No. 15.3 rigidity circles roll, 16.U tee section high-strength vehicle door collision prevention girders.

Embodiment

Below in conjunction with accompanying drawing, the present invention is explained in detail:

Consult Figure 12, the crashworthiness part emulation design method of consideration shaping damage of the present invention and tradition is utilized not to consider that the crashworthiness part emulation design method that shaping damages carries out design of Simulation to certain U-shaped cross section high-strength vehicle door collision prevention girders respectively, by by two kinds of situations, virtual test result during collision prevention girders crashworthiness Simulation Evaluation and actual tests result contrast, and verify the validity considering the crashworthiness part emulation design method of shaping damage of the present invention.Wherein, adopt the nominal size of collision prevention girders to consult Figure 13, wherein a=70mm, b=40mm, c=20mm, beam length is 800mm, section thickness is 2mm.

The particular content of situation one (considering the damage that is shaped) is as follows:

Consult Fig. 1, the crashworthiness part emulation design method of consideration shaping damage of the present invention comprises sets up vehicle body high strength crashworthiness part thermoforming damage criterion, the part thermoforming simulation of vehicle body high strength crashworthiness and vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation three steps.

Step one, set up vehicle body high strength crashworthiness part thermoforming damage criterion:

1) material at high temperature one directional tensile test

For the high-temperature material characteristic of boron steel used during understanding actual production vehicle body high strength crashworthiness part, the hot modeling test machine utilizing model to be Gleeble3500 carries out a series of high temperature one directional tensile test to boron steel test specimen, consult Fig. 2, for ease of the deformation process of test specimen 2 in shooting test, the holder part of this hot modeling test machine is finely tuned, make its relative original position half-twist, the concrete shape of test specimen 2 consults Fig. 3, spot welder is utilized one end of K type thermocouple wire 1 to be welded in the central authorities of each test specimen 2 upper surface before test, K type thermocouple wire 1 other end keeps freely discharging, for the temperature of Real-time Feedback test specimen 2 in testing.First test specimen 2 is clamped in the fixture of hot modeling test machine in test, one end that K type thermocouple wire 1 freely discharges is connected with hot modeling test machine simultaneously.Subsequently, vacuumize process to hot modeling test machine inner space, utilize resistance heating manner to realize the heating process of test specimen 2, then by regulating the cooling velocity of compressed-air actuated flow control test specimen 2 in cooling procedure, concrete testing program is as follows:

(1) test specimen 2 is incubated 3min with after the heating rate to 925 of 5 DEG C/s DEG C, guarantees the microstructure complete austenitizing of test specimen 2;

(2) with the cooldown rate of 50 DEG C/s make test specimen 2 be down to successively deformation temperature 600 DEG C, 700 DEG C, 800 DEG C, and be incubated under each deformation temperature 5s make test specimen 2 homogeneous temperature stablize;

(3) at deformation temperature 600 DEG C, 700 DEG C, 800 DEG C and the deformation strain rate 0.01s of setting ^-1, 0.1s ^-1, 1s ^-1, 10s ^-1under test specimen 2 is stretched, until rupture failure, after fracture, air cooling is carried out to test specimen after the stretching obtained 8, in whole drawing process, hot modeling test machine can record that load changes in time, the time dependent curve of temperature simultaneously, whole high temperature one directional tensile test comprises 12 groups of test conditions that 3 deformation temperatures and 4 deformation strain rates are combined into, and is respectively: deformation temperature 600 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 600 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 600 DEG C and deformation strain rate 1s ^-1, deformation temperature 600 DEG C and deformation strain rate 10s ^-1, deformation temperature 700 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 700 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 700 DEG C and deformation strain rate 1s ^-1, deformation temperature 700 DEG C and deformation strain rate 10s ^-1, deformation temperature 800 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 800 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 800 DEG C and deformation strain rate 1s ^-1, deformation temperature 800 DEG C and deformation strain rate 10s ^-1, carry out a high temperature tension test under often organizing test condition, time dependent curve F (t) of load recorded by hot modeling test machine in test is scaled the time dependent curve σ of nominal stress of test specimen 2 according to formula (1) _nomt (), time dependent curve Δ L (t) of gauge length segment length of the test specimen 2 recorded by ccd video camera 3 is scaled the time dependent curve ε of gauge length section apparent strain of test specimen 2 according to formula (2) _nomt (), according to formula (3) by time dependent for the nominal stress of test specimen 2 curve σ _nomt () is scaled the time dependent curve σ of true stress of test specimen 2 _truet (), according to the gauge length section apparent strain time dependent curve ε of formula (4) by test specimen 2 _nomt () is scaled the time dependent curve ε of gauge length section logarithmic strain of test specimen 2 _truet (), and the time variable t in cancellation two curve, with logarithmic strain ε _truefor independent variable, true stress σ _truefor dependent variable, obtain the true stress and strain curve σ under each test condition _true(ε _true):

${\mathrm{\&sigma;}}_{nom}\left(t\right)=\frac{F\left(t\right)}{A_0}---\left(1\right)$

In formula: F (t) is the time dependent curve of load; A ₀for specimen equidistance line marking section original cross-sectional area; σ _nomthe time dependent curve of t nominal stress that () is test specimen.

${\mathrm{\&epsiv;}}_{nom}\left(t\right)=\frac{\mathrm{\&Delta;}L\left(t\right)}{L_0}---\left(2\right)$

In formula: the time dependent curve of gauge length segment length that Δ L (t) is test specimen; L ₀for specimen equidistance line marking section original length; ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen.

σ _true(t)＝σ _nom(t)(1+ε _nom(t))(3)

In formula: σ _nomthe time dependent curve of t nominal stress that () is test specimen; ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen; σ _truethe time dependent curve of t true stress that () is test specimen.

ε _true(t)＝ln(1+ε _nom(t))(4)

In formula: ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen; ε _truethe t time dependent curve of gauge length section logarithmic strain that () is test specimen.

2) constitutive equation based on the damage that is shaped is set up

(1) failure procedure of metal material be material internal defect (Micro-v oid and micro-crack) forming core, grow up, connect formed macroscopic cracking.Usually be the damage of material by this procedure definition, when damage reaches certain level, namely material cannot continue carrying.The degeneration of material microcosmic during in order to consider to be shaped in simulation analysis, many scholars establish a series of visco-plasticity damage Constitutive Equation, by introducing damage factor, simulate phenomenon that is many and time correlation, as: creep, recrystallization, reply etc.According to the scholars such as Lin derive the deformation of creep constitutive equation time method, set up the constitutive equation based on the damage that is shaped in the present invention, the damage of material during to consider thermoforming, expression is as follows:

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P={\left(\frac{{\mathrm{\&sigma;}}_e/(1-f_{d1})-H-k}{K}\right)}^{n_1}{(1-f_{d1})}^{-{\mathrm{\&gamma;}}_1}---\left(5\right)$

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_{ij}^P=\frac{3S_{ij}}{2{\mathrm{\&sigma;}}_e}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P---\left(6\right)$

$\stackrel{\&CenterDot;}{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}=A(1-\stackrel{\&OverBar;}{\mathrm{\&rho;}})\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P\right|-C{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}^{n_2}---\left(7\right)$

$H=B{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}^{n_0}---\left(8\right)$

${\stackrel{\&CenterDot;}{f}}_{d1}={\mathrm{D\&sigma;}}_e\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P\right|/{(1-f_{d1})}^{{\mathrm{\&gamma;}}_2}---\left(9\right)$

${\mathrm{\&sigma;}}_{ij}=D_{ijkl}(1-f_{d1})({\mathrm{\&epsiv;}}_{kl}^T-{\mathrm{\&epsiv;}}_{kl}^P)---\left(10\right)$

$D_{ijkl}=\frac{E}{2(1+v)}({\mathrm{\&delta;}}_{il}{\mathrm{\&delta;}}_{jk}+{\mathrm{\&delta;}}_{ik}{\mathrm{\&delta;}}_{jl})+\frac{Ev}{(1+v)(1-2v)}{\mathrm{\&delta;}}_{ij}{\mathrm{\&delta;}}_{kl}---\left(11\right)$

In formula: it is equivalent plastic strain rate during shaping; σ _eit is equivalent stress during shaping; The strain hardening that H is caused by dislocation when being and being shaped; Shaping damage variable f _d1, its variation range is 0 ~ 1, f _d1when representing shaping when=0, material does not damage, f _d1material complete failure when representing shaping when=1; plastic strain rate component during for being shaped; S _ijdeviatoric stress component during for being shaped; ρ _ifor the dislocation desity under material original state, ρ _mmaterial accessible dominant bit dislocation density during for being shaped, and ρ _i≤ ρ≤ρ _m, namely σ _ijit is stress tensor component during shaping; it is overall strain component of tensor during shaping; it is plastic strain component of tensor during shaping; D _ijklit is quadravalence Stiffness Tensor component; E is Young modulus; υ is Poisson ratio; δ _ijfor the Kronecker factor, subscript i, j, k, l variation range are 1 ~ 3, repeat subscript and follow Einstein's summation convention.

Parameter k, K, n ₁, B, C, D, E be the material parameter with temperature correlation, be defined as follows:

k＝k ₀exp(Q _k/RT)(12)

K＝K ₀exp(Q _K/RT)(13)

n ₁＝n ₁₀exp(Q _n/RT)(14)

B＝B ₀exp(Q _B/RT)(15)

C＝C ₀exp(-Q _C/RT)(16)

D＝D ₀exp(Q _D/RT)(17)

E＝E ₀exp(Q _E/RT)(18)

In formula: R is universal gas constant; T is temperature; Q is activation energy.

(2) material parameter in constitutive equation is determined

For describing the relation under material at high temperature between stress-strain definitely, need to determine the material parameter in shaping damage Constitutive Equation, adopt advanced planning algorithm to carry out matching to the true stress and strain curve under each test condition obtained in material at high temperature one directional tensile test for this reason.First, set up the objective function of Solve problems, then objective function application Evolutionary Programming Algorithm is optimized, thus finally determines the material parameter in constitutive equation.Here, need the material parameter determined always to have 20, be followed successively by: A, n ₂, γ ₁, γ ₂, k ₀, n ₀, K ₀, n ₁₀, B ₀, C ₀, D ₀, E ₀, Q _k, Q _k, Q _n, Q _b, Q _c, Q _d, Q _e, R.

Be similar to the knearest neighbour method (consulting Fig. 4) that the people such as Li propose, set up objective function according to the distance between matched curve and test figure:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i{r}_i^2=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i({\mathrm{\&Delta;\&sigma;}}^2+{\mathrm{\&Delta;\&epsiv;}}^2)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i({({\mathrm{\&sigma;}}_i^c-{\mathrm{\&sigma;}}_i^e)}^2+{({\mathrm{\&epsiv;}}_i^c-{\mathrm{\&epsiv;}}_i^e)}^2)---\left(19\right)$

In formula: f (x) forms vector x=(A, n about 20 unknown material parameters ₂..., Q _e, R) real-valued function; N is the total volume of test figure; w _iit is the weighted value of the i-th data point; be respectively the stress and strain value that i-th test figure is corresponding; be respectively the stress and strain value in the matched curve corresponding with i-th test figure for making to test figure convergence between matched curve strain regions, will add f (x) to obtain:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i({({\mathrm{\&sigma;}}_i^c-{\mathrm{\&sigma;}}_i^e)}^2+{({\mathrm{\&epsiv;}}_i^c-{\mathrm{\&epsiv;}}_i^e)}^2)+W{({\mathrm{\&epsiv;}}_n^c-{\mathrm{\&epsiv;}}_n^e)}^2---\left(20\right)$

In formula: W is weight coefficient.

For reducing the difficulty of determining weighted value in actual use procedure and overcoming the inconsistent problem of ess-strain unit, with reference to the optimal speed improving objective function with logarithm method proposed without unit distance method and the people such as adaptive weighting factorization method and Cao that the people such as Lin propose, the final objective function set up is as follows:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}(w{1}_i{\left(\ln \right(\frac{{\mathrm{\&sigma;}}_i^c({\mathrm{\&epsiv;}}_i^e{\mathrm{\&epsiv;}}_n^c/{\mathrm{\&epsiv;}}_n^e)}{{\mathrm{\&sigma;}}_i^e}\left)\right)}^2+w{2}_i{\left(\ln \right(\frac{{\mathrm{\&epsiv;}}_i^c({\mathrm{\&epsiv;}}_i^e{\mathrm{\&epsiv;}}_n^c/{\mathrm{\&epsiv;}}_n^e)}{{\mathrm{\&epsiv;}}_i^e}\left)\right)}^2)+{({\mathrm{\&epsiv;}}_n^c-{\mathrm{\&epsiv;}}_n^e)}^2---\left(21\right)$

In formula:

$w{1}_i={\mathrm{n\&epsiv;}}_i^e/\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&epsiv;}}_i^e(w{1}_1+w{1}_2+...+w{1}_n=n)---\left(22\right)$

$w{1}_2={\mathrm{n\&epsiv;}}_i^e/\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&epsiv;}}_i^e(w{2}_1+w{2}_2+...+w{2}_n=n)---\left(23\right)$

The tachytelic evolution planning algorithm of the improvement adopting the people such as Yao to propose is optimized the objective function set up, and determines all material parameter.This algorithm is according to Darwinian natural selection and Mendelian hereditary variation theory, and biological evolution is by breeding, variation, competition, selection 4 citation forms realizations.Similarly, Evolutionary Programming Algorithm as biotic population, by sudden change, is selected objective function to produce population of new generation; Repeat this process, until obtain the evolution time limit of population or the regulation meeted the requirements.Detailed evolutional programming is the process of an iteration:

[1] get iteration count k=1, a stochastic generation μ population, namely stochastic inputs μ group vector is to (x _i, η _i), wherein η _ifor evolutional programming adaptive strategy parameter, i=1,2,3 ..., μ;

[2] for each voxel vector to (x _i, η _i), calculate f (x _i);

[3] for each parent vector to (x _i, η _i), generate two filial generation vectors pair with wherein:

$\left\{\begin{array}{c}{x}_i^1\left(j\right)=x_i\left(j\right)+{\mathrm{\&eta;}}_i\left(j\right)N_j(0,1)\\ x_i^2\left(j\right)=x_i\left(j\right)+{\mathrm{\&eta;}}_i\left(j\right){\mathrm{\&delta;}}_j\\ {\mathrm{\&eta;}}_i^1\left(j\right)={\mathrm{\&eta;}}_i\left(j\right)\exp \left({\mathrm{\&tau;}}^{1}N\right(0,1)+{\mathrm{\&tau;N}}_j(0,1))\end{array}\right.---\left(24\right)$

Calculate and compare with size, get both vectors pair corresponding to smaller, be designated as (x _i', η _i').Wherein x _i(j), x _i' (j), η _i(j), η _i' (j) be respectively vector x _i, x _i', η _i, η _i' a jth component (j=1,2 ..., n, n are the number of material parameter to be optimized); N (0,1) is the random number of obeying one dimension standardized normal distribution; N _j(0,1) corresponds to the random number of a jth component for obeying one dimension standardized normal distribution; δ _jthe random number of a jth component is corresponded to for obeying Cauchy's distribution; Parameter τ ¹get respectively with τ with the density function of standardized normal distribution and Cauchy's distribution is respectively:

$\begin{array}{cc}{f}_N\left(x\right)=\frac{1}{\sqrt{2n}}{e}^{-x^2/2},& -\mathrm{\&infin;}<x<+\mathrm{\&infin;}\end{array}---\left(25\right)$

$\begin{array}{cc}{f}_{\mathrm{\&delta;}}\left(x\right)=\frac{1}{\mathrm{\&pi;}}\frac{1}{1+x^2},& -\mathrm{\&infin;}<x<+\mathrm{\&infin;}\end{array}---\left(26\right)$

[4] for all i=1,2,3 ..., μ, by all parent vectors to (x _i, η _i) and filial generation vector to (x _i', η _i') integrally, take out q vector pair.Then, by any one vector of all parents and filial generation vector centering pair with q the vector taken out to making comparisons, relatively vector is to corresponding target function value, if this vector is to being less than the some of q vector centering, then this vector adds 1 (the right top score of all vectors is q, so minimum that to be divided into 0) to score;

[5] the highest μ of a score vector pair is selected, as the parent vector pair of next iteration from 2 μ vector centerings;

[6] judge whether iteration termination condition meets; If do not met, then k=k+1, and repeat said process.

Finally, the material parameter determined is: A=5.223, n ₂=1.54, γ ₁=3.1, γ ₂=17.4, k ₀=12.4MPa, n ₀=0.4, K ₀=30MPa, n ₁₀=0.0067, B ₀=80MPa, C ₀=55500, D ₀=1.38e ^-4, E ₀=1100MPa, Q _k=8400J/mol, Q _k=8400J/mol, Q _n=50000J/mol, Q _b=8400J/mol, Q _c=99900J/mol, Q _d=10648J/mol, Q _e=17500J/mol, R=8.3J/mol.

(3) software simulating of damage Constitutive Equation

Utilizing Fortran language by determining that the shaping damage Constitutive Equation of material parameter is written as Ls-dyna User Defined material subprogram, being embedded in finite element software Ls-dyna by User Defined material subprogram interface.Figure 14-a is the true stress and strain curve of Ovshinsky figure boron steel 700 DEG C time under different strain rate, and comprising rate of strain is 0.01s ^-1time test figure and matched curve and rate of strain be 1s ^-1time test figure and matched curve, and Figure 14-b is that Ovshinsky figure boron steel is at 0.1s ^-1time different temperatures under true stress and strain curve, test figure when to comprise test figure when temperature is 800 DEG C and matched curve and temperature be 600 DEG C and matched curve.

Step 2, U-shaped cross section high-strength vehicle door collision prevention girders thermoforming simulation:

1) consult Fig. 5, utilize Hypermesh finite element software to set up U-shaped cross section high-strength vehicle door collision prevention girders thermoforming realistic model, the object in model comprises plate 6, punch 4, die 7 and blank holder 5;

2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute * SECTION_SHELL, and the thickness t of each object is followed successively by: t1=2mm, t2=t3=t4=5mm, and wherein t1 is the thickness of plate; T2 is the thickness of punch; T3 is the thickness of die; T4 is the thickness of blank holder.And punch 4, die 7 and blank holder 5 adopt rigid body physical material * MAT_RIGID, the density p of each object is followed successively by: ρ 2=ρ 3=ρ 4=7830kg/m ³, wherein ρ 2 is the density of punch; ρ 3 is the density of die; ρ 4 is the density of blank holder.Elastic modulus E is followed successively by: E2=E3=E4=210GPa, and wherein E2 is the elastic modulus of punch; E3 is the elastic modulus of die; E4 is the elastic modulus of blank holder.Poisson ratio υ is followed successively by: υ 2=υ 3=υ 4=0.3, and wherein υ 2 is the Poisson ratio of punch; υ 3 is the Poisson ratio of die; υ 4 is the Poisson ratio of blank holder.Plate 6 then adopts the above-mentioned User Defined physical material based on the damage that is shaped, and all objects all adopt isotropy hot material * MAT_THERMAL_ISOTROPIC, the specific heat capacity HC of each object is followed successively by: HC2=HC3=HC4=500J/ (kgK), and wherein HC2 is the specific heat capacity of punch; HC3 is the specific heat capacity of die; HC4 is the specific heat capacity of blank holder.Heat-conduction coefficient TC is followed successively by: TC2=TC3=TC4=50W/ (mK), and wherein TC2 is the heat-conduction coefficient of punch; HC3 is the heat-conduction coefficient of die; HC4 is the heat-conduction coefficient of blank holder.And the specific heat capacity HC of plate 6 and heat-conduction coefficient TC consults Figure 15;

3) contact relation between each object in model is set, defines the boundary condition (temperature field had, kinetic characteristic, constraint condition) of each object and the control card needed for model calculating;

4) utilize Ls-dyna software to solve U-shaped cross section high-strength vehicle door collision prevention girders thermoforming realistic model, obtain the part model after being shaped and be shaped damage cloud atlas and thickness distribution cloud atlas.

Step 3, U-shaped cross section high-strength vehicle door collision prevention girders crashworthiness Simulation Evaluation

1) mechanics operating characteristic database

(1) material at high temperature damage test

Consult Fig. 6, Ls-dyna software is utilized to carry out virtual test to the test specimen 2 shown in Fig. 3, whole test specimen 2 adopts shell unit cross section attribute * SECTION_SHELL, its thickness is t=2mm, adopt and consider the User Defined physical material damaged that is shaped, and adopting isotropy hot material * MAT_THERMAL_ISOTROPIC, its specific heat capacity HC and heat-conduction coefficient TC consults Figure 15.Meanwhile, at test specimen 2 zone line definition l ₀the samming section that=25mm is long, in this section, apply steady temperature field, in region, this section of left and right sides is then according to actual tests, test specimen 2 Temperature Distribution applies corresponding temperature field.During virtual test, whole 6 degree of freedom of constraint test specimen 2 left end node, apply time dependent forced displacement vertically at right-hand member, guarantee that samming section is out of shape with constant rate of strain.Samming section is made to get typical test condition in test: forming temperature 750 DEG C, deformation strain rate 0.1s ^-1.Under this condition, carry out a series of virtual test, the shaping impairment value of unit in samming section is made to reach target shaping impairment value 0 respectively, 0.05,0.1,0.2,0.6, namely obtain a series of samming section and there is test specimen 8 after the stretching of differing formed impairment value, and measure the changing value 0 of each test specimen 2 samming segment length respectively, Δ l _0.05, Δ l _0.1, Δ l _0.2, Δ l _0.6.

Consult Fig. 7, utilize Gleeble hot modeling test machine to carry out actual tests to test specimen 2 shown in Fig. 3, test condition is identical with virtual test.Utilize ccd video camera 3 to take in test, and pass through the deflection of ARAMIS optical skew system Real-time Feedback test specimen 2 samming section, when each test specimen 2 samming segment length change reaches 0, Δ l respectively _0.05, Δ l _0.1, Δ l _0.2, Δ l _0.6time, stop stretch (same samming segment length changing value repeats 3 tests), now, in actual tests, samming section place material reaches and equal degree of injury in virtual test.Subsequently, be cooled to room temperature to each test specimen 2 samming section rapid quenching, namely obtain a series of samming section and have test specimen 8 after the stretching of martensitic phase after the quenching of differing formed impairment value, the flow process of whole material at high temperature damage test consults Fig. 8.

(2) test specimen processing

Linear cutter is carried out to test specimen 8 after the stretching after a series of quenchings obtained in material at high temperature damage test, obtains, for material room temperature one directional tensile test test specimen 9 used, consulting Fig. 9 bold portion.Subsequently, with fine sandpaper, slightly polished in all sub-each surfaces of test specimen 9, remove oxide skin above, and the minimum sectional area of the rear each sub-test specimen 9 gauge length section of record polishing, as the original cross-sectional area A of following material room temperature one directional tensile test neutron test specimen 9 gauge length section ₀.

(3) material room temperature one directional tensile test

Utilize electronic universal tester to carry out 3 kinds of different military service rate of strain to the sub-test specimen 9 that the samming section obtained in material at high temperature damage test has a different impairment value and (be followed successively by 0.01s ^-1, 1s ^-1, 10s ^-1) one directional tensile test, all sub-test specimens 9 all at room temperature stretch until rupture.Test time dependent curve F (t) of chance record load in whole drawing process, and it is scaled the time dependent curve σ of nominal stress of sub-test specimen 9 according to formula (1) _nom(t), and adopt stretching extensometer can measure time dependent curve Δ L (t) of gauge length segment length of sub-test specimen 9, and it is scaled the time dependent curve ε of gauge length section apparent strain of sub-test specimen 9 according to formula (2) _nomt (), according to formula (3) by time dependent for the nominal stress of sub-test specimen 9 curve σ _nomt () is scaled the time dependent curve σ of true stress of sub-test specimen 9 _truet (), according to the gauge length section apparent strain time dependent curve ε of formula (4) by sub-test specimen 9 _nomt () is scaled the time dependent curve ε of gauge length section logarithmic strain of sub-test specimen 9 _truet (), and the time variable t in cancellation two curve, with logarithmic strain ε _truefor independent variable, true stress σ _truefor dependent variable, obtain the true stress and strain curve σ of each sub-test specimen 9 _true(ε _true).Finally, the true stress and strain curve σ of sub-test specimen 9 of 5 kinds of differing formed impairment values, 3 kinds of different military service rate of strain must be had _true(ε _true), for setting up the following military service constitutive equation considering shaping damage.

2) the military service constitutive equation considering shaping damage is set up

For in vehicle body crashworthiness part virtual test, the damage of consideration part forming and military service rate of strain are on the impact of its military service performance, and the military service constitutive equation of shaping damage is considered in existing foundation, and expression is as follows:

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p={\left(\frac{\mathrm{\&sigma;}/(1-f_{d2})-F{{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s}^{n_a}-y}{Y}\right)}^{n_c}{\left(\frac{1}{1-f_{d2}}\right)}^{{\mathrm{\&gamma;}}_3}---\left(27\right)$

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_{ij}^p=\frac{3S_{s-ij}}{2\mathrm{\&sigma;}}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p---\left(28\right)$

${\stackrel{\&CenterDot;}{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}}_s=Z(1-{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s)\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right|-C{{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s}^{{\mathrm{\&gamma;}}_4}---\left(29\right)$

${\stackrel{\&CenterDot;}{f}}_{d2}={\mathrm{\&beta;}}_1\left(\mathrm{\&sigma;}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right){f_{d2}}^{{\mathrm{\&gamma;}}_5}+\frac{{\mathrm{\&beta;}}_2{\left({\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right)}^{{\mathrm{\&gamma;}}_6}\cosh \left({\mathrm{\&beta;}}_3{\mathrm{\&epsiv;}}^p\right)}{{(1-f_{d2})}^{{\mathrm{\&gamma;}}_7}}---\left(30\right)$

${\mathrm{\&sigma;}}_{s-ij}=D_{s-ijkl}(1-f_{d2})({\mathrm{\&epsiv;}}_{kl}^t-{\mathrm{\&epsiv;}}_{kl}^p)---\left(31\right)$

$D_{s-ijkl}=\frac{L}{2(1+v)}({\mathrm{\&delta;}}_{il}{\mathrm{\&delta;}}_{jk}+{\mathrm{\&delta;}}_{ik}{\mathrm{\&delta;}}_{jl})+\frac{Lv}{(1+v)(1-2v)}{\mathrm{\&delta;}}_{ij}{\mathrm{\&delta;}}_{kl}---\left(32\right)$

In formula: it is equivalent plastic strain rate during military service; Equivalent stress when σ is military service; Military service damage variable f _d2, its variation range is 0 ~ 1, f _d2when representing military service when=0, material is not on active service damage, f _d2material complete failure when representing military service when=1; plastic strain rate component during for being on active service; S _s-ijdeviatoric stress component during for being on active service; ρ _sifor the dislocation desity of front material of being on active service, ρ _smmaterial accessible dominant bit dislocation density during for being on active service, and ρ _si≤ ρ _s≤ ρ _sm, namely σ _s-ijit is stress tensor component during military service; it is overall strain component of tensor during military service; it is plastic strain component of tensor during military service; D _s-ijklit is quadravalence Stiffness Tensor component; L is Young modulus; υ is Poisson ratio; δ _ijfor the Kronecker factor, subscript i, j, k, l variation range are 1 ~ 3, repeat subscript and follow Einstein's summation convention.

Parameter y, Y, F, G, L, β ₁, β ₂, β ₃, γ ₅, γ ₆be damage relevant material parameter to shaping, be defined as follows:

y＝y ₀exp(W _y/f _d1)(33)

Y＝Y ₀exp(W _Y/f _d1)(34)

F＝F ₀exp(W _F/f _d1)(35)

G＝G ₀exp(-W _G/f _d1)(36)

L＝L ₀exp(W _L/f _d1)(37)

${\mathrm{\&beta;}}_1={\mathrm{\&beta;}}_{10}\exp (W_{{\mathrm{\&beta;}}_1}/f_{d1})---\left(38\right)$

${\mathrm{\&beta;}}_2={\mathrm{\&beta;}}_{20}\exp (W_{{\mathrm{\&beta;}}_2}/f_{d1})---\left(39\right)$

${\mathrm{\&beta;}}_3={\mathrm{\&beta;}}_{30}\exp (W_{{\mathrm{\&beta;}}_3}/f_{d1})---\left(40\right)$

${\mathrm{\&gamma;}}_5={\mathrm{\&gamma;}}_{50}\exp (W_{{\mathrm{\&gamma;}}_5}/f_{d1})---\left(41\right)$

${\mathrm{\&gamma;}}_6={\mathrm{\&gamma;}}_{60}\exp (W_{{\mathrm{\&gamma;}}_6}/f_{d1})---\left(42\right)$

Determine to consider to be shaped the military service Material Parameter in Constitutive Equation of damage and military service constitutive equation software simulating method used with set up identical based on method used during shaping damage Constitutive Equation, and here, the material parameter determined is needed always to have 25, and finally determine 25 material parameters, be followed successively by: Z=6.32, γ ₃=4.6, γ ₄=2.67, γ ₇=30.4, n _c=0.4, y ₀=30.3MPa, Y ₀=60MPa, F ₀=40MPa, G ₀=4000, L ₀=4800MPa, β ₁₀=1.2, β ₂₀=3.5, β ₃₀=1.4, γ ₅₀=0.6, γ ₆₀=5.9, W _y=740, W _y=600, W _f=1200, W _g=990, W _l=670, figure 16 is the geneva figure boron steel with different thermoforming impairment value is 0.01s in rate of strain ^-1time true stress and strain curve figure, test figure when to comprise test figure when thermoforming impairment value is 0.05 and matched curve and thermoforming impairment value be 0.2 and matched curve.

3) U-shaped cross section high-strength vehicle door collision prevention girders virtual test

With reference to standard GB/T/T7314-2005 and GB/T232-2010, according to vehicle body high strength crashworthiness part role when colliding, virtual crushing test or virtual bending test (consulting Figure 10 and Figure 11) are carried out to it.Consult Figure 17, because door anti-collision joist mainly bears bending load in side impact, therefore carry out virtual bending test to it, virtual test process is as follows:

(1) utilize Hypermesh software to set up U-shaped cross section high-strength vehicle door collision prevention girders virtual test model, the object in model comprises: No. 1 rigidity circle rolls 12, high-strength vehicle door collision prevention girders 16, No. 2 rigidity circles in U-shaped cross section roll 14, No. 3 rigidity circles and roll 15;

(2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute * SECTION_SHELL, the thickness that all rigidity circles roll is t=5mm, the thickness distribution of part after the thickness distribution succession thermoforming of collision prevention girders.All rigidity circles roll and all adopt rigid body physical material * MAT_RIGID, its density p=7830kg/m ³, elastic modulus E=210GPa and Poisson ratio υ=0.3, collision prevention girders then adopts the User Defined of damage of considering to be shaped to be on active service this structure physical material;

(3) contact relation between each object in model is set, defines the boundary condition (kinetic characteristic, constraint condition) of each object and the control card needed for model calculating;

(4) Ls-dyna software is utilized to solve U-shaped cross section high-strength vehicle door collision prevention girders virtual test model, export the time dependent deformation tendency cloud atlas of collision prevention girders, contact force curve and energy absorption curve, and contrast with design object value, to confirm whether this U-shaped cross section high-strength vehicle door collision prevention girders 16 meets designing requirement.

The particular content of situation two (not considering the damage that is shaped) is as follows:

Tradition does not consider that the crashworthiness part emulation design method of shaping damage only includes the part thermoforming simulation of vehicle body high strength crashworthiness and vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation two steps.

The first step, U-shaped cross section high-strength vehicle door collision prevention girders thermoforming simulation

1) consult Fig. 5, utilize Hypermesh finite element software to set up U-shaped cross section high-strength vehicle door collision prevention girders thermoforming realistic model, the object in model comprises plate 6, punch 4, die 7 and blank holder 5;

2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute * SECTION_SHELL, and the thickness t of each object is followed successively by: t1=2mm, t2=t3=t4=5mm, and wherein t1 is the thickness of plate; T2 is the thickness of punch; T3 is the thickness of die; T4 is the thickness of blank holder.And punch 4, die 7 and blank holder 5 adopt rigid body physical material * MAT_RIGID, the density p of each object is followed successively by: ρ 2=ρ 3=ρ 4=7830kg/m ³, wherein ρ 2 is the density of punch; ρ 3 is the density of die; ρ 4 is the density of blank holder.Elastic modulus E is followed successively by: E2=E3=E4=210GPa, and wherein E2 is the elastic modulus of punch; E3 is the elastic modulus of die; E4 is the elastic modulus of blank holder.Poisson ratio υ is followed successively by: υ 2=υ 3=υ 4=0.3, and wherein υ 2 is the Poisson ratio of punch; υ 3 is the Poisson ratio of die; υ 4 is the Poisson ratio of blank holder.Plate 6 then adopts bullet-sticky-plasticity physical material * MAT_ELASTIC_VISCOPLASTIC_THERMAL, its density p=7830kg/m of temperature influence ³, elastic modulus E=210GPa, Poisson ratio υ=0.3, yield strength SIGY=700MPa and thermal expansivity ALPHA=1.3e ^-5/ K, and all objects all adopt isotropy hot material * MAT_THERMAL_ISOTROPIC, the specific heat capacity HC of each object is followed successively by: HC2=HC3=HC4=500J/ (kgK), and wherein HC2 is the specific heat capacity of punch; HC3 is the specific heat capacity of die; HC4 is the specific heat capacity of blank holder.Heat-conduction coefficient TC is followed successively by: TC2=TC3=TC4=50W/ (mK), and wherein TC2 is the heat-conduction coefficient of punch; HC3 is the heat-conduction coefficient of die; HC4 is the heat-conduction coefficient of blank holder.And the specific heat capacity HC of plate 6 and heat-conduction coefficient TC consults Figure 15;

3) contact relation between each object in model is set, defines the boundary condition (temperature field had, kinetic characteristic, constraint condition) of each object and the control card needed for model calculating;

4) utilize Ls-dyna software to solve U-shaped cross section high-strength vehicle door collision prevention girders thermoforming realistic model, obtain the part model after being shaped and thickness distribution cloud atlas thereof.

Second step, U-shaped cross section high-strength vehicle door collision prevention girders crashworthiness Simulation Evaluation

Consult Figure 17, because door anti-collision joist mainly bears bending load in side impact, therefore carry out virtual bending test to it, virtual test process is as follows:

(1) utilize Hypermesh software to set up U-shaped cross section high-strength vehicle door collision prevention girders virtual test model, the object in model comprises: No. 1 rigidity circle rolls 12, high-strength vehicle door collision prevention girders 16, No. 2 rigidity circles in U-shaped cross section roll 14, No. 3 rigidity circles and roll 15;

(2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute * SECTION_SHELL, the thickness that all rigidity circles roll is t=5mm, the thickness distribution of part after the thickness distribution succession thermoforming of collision prevention girders.All rigidity circles roll and all adopt rigid body physical material * MAT_RIGID, its density p=7830kg/m ³, elastic modulus E=210GPa and Poisson ratio υ=0.3, collision prevention girders then adopts the desirable martensitic phase material under the difference military service rate of strain of not considering to be shaped damage;

(3) contact relation between each object in model is set, defines the boundary condition (kinetic characteristic, constraint condition) of each object and the control card needed for model calculating;

(4) Ls-dyna software is utilized to solve U-shaped cross section high-strength vehicle door collision prevention girders virtual test model, export the time dependent deformation tendency cloud atlas of collision prevention girders, contact force curve and energy absorption curve, and contrast with design object value, to confirm whether this U-shaped cross section high-strength vehicle door collision prevention girders 16 meets design object requirement.

Experimental test

Actual thermoforming processing is carried out according to the contact relation between each object that this U-shaped cross section high-strength vehicle door collision prevention girders 16 thermoforming simulation part defines, the temperature field of each object, kinetic characteristic, constraint condition, and actual flexion test is carried out to the U-shaped cross section high-strength vehicle door collision prevention girders 16 after being shaped, obtain its time dependent contact force and energy absorption curve.

All include in Figure 18 and Figure 19 and do not consider shaping damage simulation result, consideration shaping damage simulation result and test findings, test by this U-shaped cross section high-strength vehicle door collision prevention girders 16 contact force of virtual bending test in two kinds of situations being obtained and energy absorption curve and actual flexion this U-shaped cross section high-strength vehicle door collision prevention girders 16 contact force of obtaining and energy absorption curve contrasts, find this U-shaped cross section high-strength vehicle door collision prevention girders 16 contact force that consideration shaping damages and energy absorption curve and actual flexion test the result that obtains closer to.

Therefore, crashworthiness assessment after the crashworthiness part emulation design method considering that shaping damages of the present invention can be utilized to carry out vehicle body high strength crashworthiness part forming simulation, thermoforming damage is taken into account, improve the Evaluation accuracy of its crashworthiness, strengthen vehicle body high strength crashworthiness part design of Simulation to the directive significance of actual design, the vehicle body high strength crashworthiness part of actual design is made more easily to reach design object requirement, thus minimizing test number (TN), shorten the construction cycle, reduce cost of development.

Claims (1)

1. consider the crashworthiness part emulation design method damaged that is shaped, it is characterized in that step is as follows:

Step one, set up vehicle body high strength crashworthiness part thermoforming damage criterion, detailed process is:

1) material at high temperature one directional tensile test

Hot modeling test machine is utilized to carry out a series of high temperature one directional tensile test to boron steel test specimen, utilize spot welder that one end of K type thermocouple wire (1) is welded in the central authorities of each test specimen (2) upper surface before test, K type thermocouple wire (1) other end keeps freely discharging, first test specimen (2) is clamped in the fixture of hot modeling test machine in test, one end that K type thermocouple wire (1) freely discharges is connected with hot modeling test machine simultaneously, subsequently, process is vacuumized to hot modeling test machine inner space, resistance heating manner is utilized to realize the heating process of test specimen (2), then by regulating the cooling velocity of compressed-air actuated flow control test specimen (2) in cooling procedure, concrete testing program is as follows:

(1) test specimen (2) is incubated 3min with after the heating rate to 925 of 5 DEG C/s DEG C, guarantees the microstructure complete austenitizing of test specimen (2);

(2) with the cooldown rate of 50 DEG C/s make test specimen (2) be down to successively deformation temperature 600 DEG C, 700 DEG C, 800 DEG C, and be incubated under each deformation temperature 5s make test specimen (2) homogeneous temperature stablize;

(3) at deformation temperature 600 DEG C, 700 DEG C, 800 DEG C and the deformation strain rate 0.01s of setting ^-1, 0.1s ^-1, 1s ^-1, 10s ^-1under test specimen (2) is stretched, until rupture failure, after fracture, air cooling is carried out to test specimen (8) after the stretching obtained, in whole drawing process, hot modeling test machine can record that load changes in time, the time dependent curve of temperature simultaneously, whole high temperature one directional tensile test comprises 12 groups of test conditions that 3 deformation temperatures and 4 deformation strain rates are combined into, and is respectively: deformation temperature 600 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 600 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 600 DEG C and deformation strain rate 1s ^-1, deformation temperature 600 DEG C and deformation strain rate 10s ^-1, deformation temperature 700 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 700 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 700 DEG C and deformation strain rate 1s ^-1, deformation temperature 700 DEG C and deformation strain rate 10s ^-1, deformation temperature 800 DEG C and deformation strain rate 0.01s ^-1, deformation temperature 800 DEG C and deformation strain rate 0.1s ^-1, deformation temperature 800 DEG C and deformation strain rate 1s ^-1, deformation temperature 800 DEG C and deformation strain rate 10s ^-1, carry out a high temperature tension test under often organizing test condition, time dependent curve F (t) of load recorded by hot modeling test machine in test is scaled the time dependent curve σ of nominal stress of test specimen (2) according to formula (1) _nomt (), time dependent curve Δ L (t) of gauge length segment length of the test specimen (2) recorded by ccd video camera (3) is scaled the time dependent curve ε of gauge length section apparent strain of test specimen (2) according to formula (2) _nomt (), according to formula (3) by time dependent for the nominal stress of test specimen (2) curve σ _nomt () is scaled the time dependent curve σ of true stress of test specimen (2) _truet (), according to the gauge length section apparent strain time dependent curve ε of formula (4) by test specimen (2) _nomt () is scaled the time dependent curve ε of gauge length section logarithmic strain of test specimen (2) _truet (), and the time variable t in cancellation two curve, with logarithmic strain ε _truefor independent variable, true stress σ _truefor dependent variable, obtain the true stress and strain curve σ under each test condition _true(ε _true):

${\mathrm{\&sigma;}}_{nom}\left(t\right)=\frac{F\left(t\right)}{A_0}---\left(1\right)$

In formula: F (t) is the time dependent curve of load; A ₀for specimen equidistance line marking section original cross-sectional area; σ _nomthe time dependent curve of t nominal stress that () is test specimen.

${\mathrm{\&epsiv;}}_{nom}\left(t\right)=\frac{\mathrm{\&Delta;}L\left(t\right)}{L_0}---\left(2\right)$

In formula: the time dependent curve of gauge length segment length that Δ L (t) is test specimen; L ₀for specimen equidistance line marking section original length; ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen.

σ _true(t)=σ _nom(t)(1+ε _nom(t))(3)

In formula: σ _nomthe time dependent curve of t nominal stress that () is test specimen; ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen; σ _truethe time dependent curve of t true stress that () is test specimen.

ε _true(t)=ln(1+ε _nom(t))(4)

In formula: ε _nomthe t time dependent curve of gauge length section apparent strain that () is test specimen; ε _truethe t time dependent curve of gauge length section logarithmic strain that () is test specimen.

2) constitutive equation based on the damage that is shaped is set up:

(1) set up the constitutive equation based on the damage that is shaped, the damage of material during to consider thermoforming, expression is as follows:

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P={\left(\frac{{\mathrm{\&sigma;}}_e/(1-f_{d1})-H-k}{K}\right)}^{n_1}{(1-f_{d1})}^{-{\mathrm{\&gamma;}}_1}---\left(5\right)$

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_{ij}^P=\frac{3S_{ij}}{2{\mathrm{\&sigma;}}_e}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P---\left(6\right)$

$\stackrel{\&CenterDot;}{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}=A(1-\stackrel{\&OverBar;}{\mathrm{\&rho;}})\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P\right|-C{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}^{n_2}---\left(7\right)$

$H=B{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}^{n_0}---\left(8\right)$

${\stackrel{\&CenterDot;}{f}}_{d1}={\mathrm{D\&sigma;}}_e\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_e^P\right|/{(1-f_{d1})}^{{\mathrm{\&gamma;}}_2}---\left(9\right)$

${\mathrm{\&sigma;}}_{ij}=D_{ijkl}(1-f_{d1})({\mathrm{\&epsiv;}}_{kl}^T-{\mathrm{\&epsiv;}}_{kl}^P)---\left(10\right)$

$D_{ijkl}=\frac{E}{2(1+v)}({\mathrm{\&delta;}}_{il}{\mathrm{\&delta;}}_{jk}+{\mathrm{\&delta;}}_{ik}{\mathrm{\&delta;}}_{jl})+\frac{Ev}{(1+v)(1-2v)}{\mathrm{\&delta;}}_{ij}{\mathrm{\&delta;}}_{kl}---\left(11\right)$

In formula: it is equivalent plastic strain rate during shaping; σ _eit is equivalent stress during shaping; The strain hardening that H is caused by dislocation when being and being shaped; Shaping damage variable f _d1, its variation range is 0 ~ 1, f _d1when representing shaping when=0, material does not damage, f _d1material complete failure when representing shaping when=1; plastic strain rate component during for being shaped; S _ijdeviatoric stress component during for being shaped; ρ _ifor the dislocation desity under material original state, ρ _mmaterial accessible dominant bit dislocation density during for being shaped, and ρ _i≤ ρ≤ρ _m, namely σ _ijit is stress tensor component during shaping; it is overall strain component of tensor during shaping; it is plastic strain component of tensor during shaping; D _ijklit is quadravalence Stiffness Tensor component; E is Young modulus; υ is Poisson ratio; δ _ijfor the Kronecker factor, subscript i, j, k, l variation range are 1 ~ 3, repeat subscript and follow Einstein's summation convention.

Parameter k, K, n ₁, B, C, D, E be the material parameter with temperature correlation, be defined as follows:

k＝k ₀exp(Q _k/RT)(12)

K＝K ₀exp(Q _K/RT)(13)

n ₁＝n ₁₀exp(Q _n/RT)(14)

B＝B ₀exp(Q _B/RT)(15)

C＝C ₀exp(-Q _C/RT)(16)

D＝D ₀exp(Q _D/RT)(17)

E＝E ₀exp(Q _E/RT)(18)

In formula: R is universal gas constant; T is temperature; Q is activation energy.

(2) material parameter in constitutive equation is determined:

First, set up the objective function of Solve problems, then objective function application Evolutionary Programming Algorithm is optimized, finally determines the material parameter in constitutive equation, here, need the material parameter determined always to have 20, be followed successively by: A, n ₂, γ ₁, γ ₂, k ₀, n ₀, K ₀, n ₁₀, B ₀, C ₀, D ₀, E ₀, Q _k, Q _k, Q _n, Q _b, Q _c, Q _d, Q _e, R.

Objective function is set up according to the distance between matched curve and test figure:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i{r}_i^2=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i({\mathrm{\&Delta;\&sigma;}}^2+{\mathrm{\&Delta;\&epsiv;}}^2)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i({({\mathrm{\&sigma;}}_i^c-{\mathrm{\&sigma;}}_i^e)}^2+{({\mathrm{\&epsiv;}}_i^c-{\mathrm{\&epsiv;}}_i^e)}^2)---\left(19\right)$

In formula: f (x) forms vector x=(A, n about 20 unknown material parameters ₂..., Q _e, R) real-valued function; N is the total volume of test figure; w _iit is the weighted value of the i-th data point; be respectively the stress and strain value that i-th test figure is corresponding; be respectively the stress and strain value in the matched curve corresponding with i-th test figure for making to test figure convergence between matched curve strain regions, will add f (x) to obtain:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}{w}_i({({\mathrm{\&sigma;}}_i^c-{\mathrm{\&sigma;}}_i^e)}^2+{({\mathrm{\&epsiv;}}_i^c-{\mathrm{\&epsiv;}}_i^e)}^2)+W{({\mathrm{\&epsiv;}}_n^c-{\mathrm{\&epsiv;}}_n^e)}^2---\left(20\right)$

In formula: W is weight coefficient;

For reducing the difficulty of determining weighted value in actual use procedure and overcoming the inconsistent problem of ess-strain unit, the final objective function set up is as follows:

$f\left(x\right)=\frac{1}{n}\underset{i=1}{\overset{n}{\&Sigma;}}(w{1}_i{\left(\ln \right(\frac{{\mathrm{\&sigma;}}_i^c({\mathrm{\&epsiv;}}_i^e{\mathrm{\&epsiv;}}_n^c/{\mathrm{\&epsiv;}}_n^e)}{{\mathrm{\&sigma;}}_i^e}\left)\right)}^2+w{2}_i{\left(\ln \right(\frac{{\mathrm{\&epsiv;}}_i^c({\mathrm{\&epsiv;}}_i^e{\mathrm{\&epsiv;}}_n^c/{\mathrm{\&epsiv;}}_n^e)}{{\mathrm{\&epsiv;}}_i^e}\left)\right)}^2)+{({\mathrm{\&epsiv;}}_n^c-{\mathrm{\&epsiv;}}_n^e)}^2---\left(21\right)$

In formula:

$w{1}_i={\mathrm{n\&epsiv;}}_i^e/\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&epsiv;}}_i^e(w{1}_1+w{1}_2+...+w{1}_n=n)---\left(22\right)$

$w{1}_2={\mathrm{n\&epsiv;}}_i^e/\underset{i=1}{\overset{n}{\&Sigma;}}{\mathrm{\&epsiv;}}_i^e(w{2}_1+w{2}_2+...+w{2}_n=n)---\left(23\right)$

Adopt the tachytelic evolution planning algorithm improved to be optimized the objective function set up, determine all material parameter, Evolutionary Programming Algorithm as biotic population, by sudden change, is selected objective function to produce population of new generation; Repeat this process, until obtain the evolution time limit of population or the regulation meeted the requirements, detailed evolutional programming is the process of an iteration:

[1] get iteration count k=1, a stochastic generation μ population, namely stochastic inputs μ group vector is to (x _i, η _i), wherein η _ifor evolutional programming adaptive strategy parameter, i=1,2,3 ..., μ;

[2] for each voxel vector to (x _i, η _i), calculate f (x _i);

[3] for each parent vector to (x _i, η _i), generate two filial generation vectors pair with wherein:

$\left\{\begin{array}{c}{x}_i^1\left(j\right)=x_i\left(j\right)+{\mathrm{\&eta;}}_i\left(j\right)N_j(0,1)\\ x_i^2\left(j\right)=x_i\left(j\right)+{\mathrm{\&eta;}}_i\left(j\right){\mathrm{\&delta;}}_j\\ {\mathrm{\&eta;}}_i^1\left(j\right)={\mathrm{\&eta;}}_i\left(j\right)\exp \left({\mathrm{\&tau;}}^{1}N\right(0,1)+{\mathrm{\&tau;N}}_j(0,1))\end{array}\right.---\left(24\right)$

Calculate and compare with size, get both vectors pair corresponding to smaller, be designated as (x ' _i, η ' _i), wherein x _i(j), x ' _i(j), η _i(j), η ' _ij () is respectively vector x _i, x ' _i, η _i, η ' _ia jth component (j=1,2 ..., n, n are the number of material parameter to be optimized); N (0,1) is the random number of obeying one dimension standardized normal distribution; N _j(0,1) corresponds to the random number of a jth component for obeying one dimension standardized normal distribution; δ _jthe random number of a jth component is corresponded to for obeying Cauchy's distribution; Parameter τ ¹get respectively with τ with the density function of standardized normal distribution and Cauchy's distribution is respectively:

$\begin{array}{cc}{f}_N\left(x\right)=\frac{1}{\sqrt{2n}}{e}^{-x^2/2},& -\mathrm{\&infin;}<x<+\mathrm{\&infin;}\end{array}---\left(25\right)$

$\begin{array}{cc}{f}_{\mathrm{\&delta;}}\left(x\right)=\frac{1}{\mathrm{\&pi;}}\frac{1}{1+x^2},& -\mathrm{\&infin;}<x<+\mathrm{\&infin;}\end{array}---\left(26\right)$

[4] for all i=1,2,3 ..., μ, by all parent vectors to (x _i, η _i) and filial generation vector to (x ' _i, η ' _i) integrally, take out q vector pair, then, by any one vector of all parents and filial generation vector centering pair with q the vector taken out to making comparisons, relatively vector is to corresponding target function value, if this vector is to being less than the some of q vector centering, then this vector adds 1 to score, the right top score of all vectors is q, so minimum that to be divided into 0;

[5] the highest μ of a score vector pair is selected, as the parent vector pair of next iteration from 2 μ vector centerings;

[6] judge whether iteration termination condition meets; If do not met, then k=k+1, and repeat said process.

(3) software simulating of damage Constitutive Equation

Utilizing Fortran language by determining that the shaping damage Constitutive Equation of material parameter is written as Ls-dyna User Defined material subprogram, being embedded in finite element software Ls-dyna by User Defined material subprogram interface.

Step 2, vehicle body high strength crashworthiness part thermoforming simulation, detailed process is:

1) utilize Hypermesh finite element software to set up vehicle body high strength crashworthiness part thermoforming realistic model, the object in model comprises plate (6), punch (4), die (7) and blank holder (5);

2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute, and define the thickness t of each object wherein, and punch (4), die (7) and blank holder (5) adopt rigid body physical material, and define the density p of each object, elastic modulus E and Poisson ratio υ wherein, plate (6) then adopts the above-mentioned User Defined physical material based on the damage that is shaped, and all objects all adopt isotropy hot material, and define specific heat capacity HC and the heat-conduction coefficient TC of each object wherein;

3) contact relation between each object in model is set, define temperature field that each object has, kinetic characteristic, constraint condition and model calculate needed for control card;

4) utilize Ls-dyna software to solve vehicle body high strength crashworthiness part thermoforming realistic model, obtain the part model after being shaped and be shaped damage cloud atlas and thickness distribution cloud atlas.

Step 3: vehicle body high strength crashworthiness part crashworthiness Simulation Evaluation:

1) mechanics operating characteristic database

(1) material at high temperature damage test

Ls-dyna software is utilized to carry out virtual test to test specimen (2), whole test specimen (2) adopts shell unit cross section attribute, and define its thickness t wherein, adopt User Defined physical material and isotropy hot material that considering is shaped damages, and define its specific heat capacity HC and heat-conduction coefficient TC wherein, meanwhile, at test specimen (2) zone line definition l ₀the samming section that=25mm is long, steady temperature field is applied in this section, in region, this section of left and right sides is then according to actual tests, test specimen (2) Temperature Distribution applies corresponding temperature field, during virtual test, whole 6 degree of freedom of constraint test specimen (2) left end node, apply time dependent forced displacement vertically at right-hand member, guarantee that samming section is out of shape with constant rate of strain, samming section is made to get typical test condition in test: forming temperature 750 DEG C, deformation strain rate 0.1s ^-1.Under this condition, carry out a series of virtual test, make the shaping impairment value of unit in samming section reach target shaping impairment value 0, α respectively ₁, α ₂..., α _n, namely obtain a series of samming section and there is test specimen (8) after the stretching of differing formed impairment value, and measure the changing value 0 of each test specimen (2) samming segment length respectively,

Testing machine is utilized to carry out actual tests to test specimen (2), actual test conditions is identical with virtual test, ccd video camera (3) is utilized to take in test, and pass through the deflection of ARAMIS optical skew system Real-time Feedback test specimen (2) samming section, when the change of each test specimen (2) samming segment length reaches 0 respectively time, stop stretching, now, in actual tests, samming section place material reaches and equal degree of injury in virtual test, same samming segment length changing value Repeated m time test in test.Subsequently, room temperature is cooled to each test specimen (2) samming section rapid quenching, namely obtains a series of samming section and there is test specimen (8) after the stretching of martensitic phase after the quenching of differing formed impairment value.

(2) test specimen processing

Linear cutter is carried out to test specimen (8) after the stretching after a series of quenchings obtained in material at high temperature damage test, obtain for material room temperature one directional tensile test test specimen (9) used, subsequently, with fine sandpaper, slightly polished in each surface of all sub-test specimens (9), remove oxide skin above, and the minimum sectional area of rear each sub-test specimen (9) the gauge length section of record polishing, as the original cross-sectional area A of following material room temperature one directional tensile test neutron test specimen (9) gauge length section ₀.

(3) material room temperature one directional tensile test

Electronic universal tester is utilized to carry out the one directional tensile test of the different military service rate of strain of m kind to the sub-test specimen (9) that the samming section obtained in material at high temperature damage test has a different impairment value, all sub-test specimens (9) all at room temperature stretch until rupture, test time dependent curve F (t) of chance record load in whole drawing process, and it is scaled the time dependent curve σ of nominal stress of sub-test specimen (9) according to formula (1) _nom(t), and adopt stretching extensometer to measure time dependent curve Δ L (t) of gauge length segment length of sub-test specimen (9), and it is scaled the time dependent curve ε of gauge length section apparent strain of sub-test specimen (9) according to formula (2) _nomt (), according to formula (3) by time dependent for the nominal stress of sub-test specimen (9) curve σ _nomt () is scaled the time dependent curve σ of true stress of sub-test specimen (9) _truet (), according to the gauge length section apparent strain time dependent curve ε of formula (4) by sub-test specimen (9) _nomt () is scaled the time dependent curve ε of gauge length section logarithmic strain of sub-test specimen (9) _truet (), and the time variable t in cancellation two curve, with logarithmic strain ε _truefor independent variable, true stress σ _truefor dependent variable, obtain the true stress and strain curve σ of each test specimen (9) _true(ε _true).Finally, the true stress and strain curve σ of test specimen (9) of differing formed impairment value, different military service rate of strain must be had _true(ε _true), for setting up the following military service constitutive equation considering shaping damage.

2) the military service constitutive equation considering shaping damage is set up

Set up and consider the military service constitutive equation damaged that is shaped, expression is as follows:

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p={\left(\frac{\mathrm{\&sigma;}/(1-f_{d2})-F{{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s}^{n_a}-y}{Y}\right)}^{n_c}{\left(\frac{1}{1-f_{d2}}\right)}^{{\mathrm{\&gamma;}}_3}---\left(27\right)$

${\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}_{ij}^p=\frac{3S_{s-ij}}{2\mathrm{\&sigma;}}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p---\left(28\right)$

${\stackrel{\&CenterDot;}{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}}_s=Z(1-{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s)\left|{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right|-C{{\stackrel{\&OverBar;}{\mathrm{\&rho;}}}_s}^{{\mathrm{\&gamma;}}_4}---\left(29\right)$

${\stackrel{\&CenterDot;}{f}}_{d2}={\mathrm{\&beta;}}_1\left(\mathrm{\&sigma;}{\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right){f_{d2}}^{{\mathrm{\&gamma;}}_5}+\frac{{\mathrm{\&beta;}}_2{\left({\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}}^p\right)}^{{\mathrm{\&gamma;}}_6}\cosh \left({\mathrm{\&beta;}}_3{\mathrm{\&epsiv;}}^p\right)}{{(1-f_{d2})}^{{\mathrm{\&gamma;}}_7}}---\left(30\right)$

${\mathrm{\&sigma;}}_{s-ij}=D_{s-ijkl}(1-f_{d2})({\mathrm{\&epsiv;}}_{kl}^t-{\mathrm{\&epsiv;}}_{kl}^p)---\left(31\right)$

$D_{s-ijkl}=\frac{L}{2(1+v)}({\mathrm{\&delta;}}_{il}{\mathrm{\&delta;}}_{jk}+{\mathrm{\&delta;}}_{ik}{\mathrm{\&delta;}}_{jl})+\frac{Lv}{(1+v)(1-2v)}{\mathrm{\&delta;}}_{ij}{\mathrm{\&delta;}}_{kl}---\left(32\right)$

In formula: it is equivalent plastic strain rate during military service; Equivalent stress when σ is military service; Military service damage variable f _d2, its variation range is 0 ~ 1, f _d2when representing military service when=0, material is not on active service damage, f _d2material complete failure when representing military service when=1; plastic strain rate component during for being on active service; S _s-ijdeviatoric stress component during for being on active service; ρ _sifor the dislocation desity of front material of being on active service, ρ _smmaterial accessible dominant bit dislocation density during for being on active service, and ρ _si≤ ρ _s≤ ρ _sm, namely σ _s-ijit is stress tensor component during military service; it is overall strain component of tensor during military service; it is plastic strain component of tensor during military service; D _s-ijklit is quadravalence Stiffness Tensor component; L is Young modulus; υ is Poisson ratio; δ _ijfor the Kronecker factor, subscript i, j, k, l variation range are 1 ~ 3, repeat subscript and follow Einstein's summation convention.

Parameter y, Y, F, G, L, β ₁, β ₂, β ₃, γ ₅, γ ₆be damage relevant material parameter to shaping, be defined as follows:

y＝y ₀exp(W _y/f _d1)(33)

Y＝Y ₀exp(W _Y/f _d1)(34)

F＝F ₀exp(W _F/f _d1)(35)

G＝G ₀exp(-W _G/f _d1)(36)

L＝L ₀exp(W _L/f _d1)(37)

${\mathrm{\&beta;}}_1={\mathrm{\&beta;}}_{10}\exp (W_{{\mathrm{\&beta;}}_1}/f_{d1})---\left(38\right)$

${\mathrm{\&beta;}}_2={\mathrm{\&beta;}}_{20}\exp (W_{{\mathrm{\&beta;}}_2}/f_{d1})---\left(39\right)$

${\mathrm{\&beta;}}_3={\mathrm{\&beta;}}_{30}\exp (W_{{\mathrm{\&beta;}}_3}/f_{d1})---\left(40\right)$

${\mathrm{\&gamma;}}_5={\mathrm{\&gamma;}}_{50}\exp (W_{{\mathrm{\&gamma;}}_5}/f_{d1})---\left(41\right)$

${\mathrm{\&gamma;}}_6={\mathrm{\&gamma;}}_{60}\exp (W_{{\mathrm{\&gamma;}}_6}/f_{d1})---\left(42\right)$

Determine to consider to be shaped the military service Material Parameter in Constitutive Equation of damage and military service constitutive equation software simulating method used with set up identical based on method used during shaping damage Constitutive Equation, and here, need the material parameter determined always to have 25, be followed successively by: Z, γ ₃, γ ₄, γ ₇, n _c, y ₀, Y ₀, F ₀, G ₀, L ₀, β ₁₀, β ₂₀, β ₃₀, γ ₅₀, γ ₆₀, W _y, W _y, W _f, W _g, W _l,

3) vehicle body high strength crashworthiness part virtual test

(1) utilize Hypermesh software to set up vehicle body high strength crashworthiness part virtual test model, the object in virtual crushing test model comprises: rigidity obstacle (10), conquassation thin-walled crashworthiness part (11); Object in virtual bending test model comprises: No. 1 rigidity circle rolls (12), bending thin-walled crashworthiness part (13), No. 2 rigidity circles roll (14), No. 3 rigidity circles roll (15);

(2) be respectively each object in model and give cross section attribute and material behavior, all objects all adopt shell unit cross section attribute, the thickness distribution of part after the thickness distribution succession thermoforming of crashworthiness part, rigidity obstacle (10) and all rigidity circle roll and all adopt rigid body physical material, and defining the density p of each object, elastic modulus E and Poisson ratio υ wherein, conquassation thin-walled crashworthiness part (13) and bending thin-walled crashworthiness part (13) then adopt the User Defined of damage of considering to be shaped to be on active service this structure physical material;

(3) contact relation between each object in model is set, defines the control card needed for the calculating of the kinetic characteristic of each object, constraint condition and model;

(4) Ls-dyna software is utilized to solve vehicle body high strength crashworthiness part virtual test model, export the time dependent deformation tendency cloud atlas of crashworthiness part, contact force curve and energy absorption curve, and contrast with design object value, to confirm whether this crashworthiness part meets designing requirement.