CN108416175B - Long fiber composites rear seat of passenger car skeleton original material design method - Google Patents
Long fiber composites rear seat of passenger car skeleton original material design method Download PDFInfo
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Abstract
The invention belongs to composite material for cars research fields, are related to a kind of long fiber composites rear seat of passenger car skeleton original material design method.The following steps are included: 1, determine rear seat of passenger car minibus requirement；2, LFT plate critical impact energy expression formula is derived；3, research requires lower LFT plate material design method based on impact energy；4, seat back skeleton original material is designed；5, initial designs result finite element and test are verified；The present invention sets up energy absorption capability and material parameter with LFT plate critical impact energy and tests the bridge of constraint condition parameter association, on the one hand estimates LFT plate limit impact energy, on the other hand instructs LFT material initial designs and selection；The application of practical meaning in engineering of the present invention is assumed that in the case where determining impact operating condition, need to absorb the approximate range of impact energy from the angle initialization LFT plate of safety coefficient, LFT material fiber volume fraction and corresponding slab-thickness is calculated, realizes material initial designs.
Description
Technical field
The present invention relates to a kind of rear seat of passenger car skeleton original materials for belonging to composite material for cars research field
Design method, it more particularly relates to which a kind of long fiber composites rear seat of passenger car skeleton original material is set
Meter method.
Background technique
Seat is relatively independent car body component in automotive body structure, has corresponding regulation to its stiffness and strength etc.
Performance claims.Wherein, for rear seat of passenger car, need to carry out luggage case block impact test to investigate its anti-impact
Performance is hit, to ensure that seat will not damage heel row occupant during head-on crash.
Traditional metal armchair structure in order to meet the requirement of performance, most common measure be exactly increase structural thickness, though
It so ensure that performance but consequent be the increase of seat quality.Currently, using fibre reinforced composites as the light weight of representative
Change material and gradually attempt replacement metal material, and has certain light weight effect.However, due to analogue technique and design side
The deficiency of method often needs blindly largely to be manufactured experimently and experimental test at seat design initial stage, increase exploitation at
This.Using long fiber reinforced thermoplastic composites (Long Fiber reinforced Thermoplastics, abbreviation LFT)
Energy absorption analysis model and LFT material initial designs method, can be rapidly completed and want for luggage case block impact test properties
The design of LFT the seat back skeleton initial configuration and material asked.
Summary of the invention
The present invention in order to complete to design rear seat of passenger car skeleton original material, using LFT energy absorption model and
LFT material initial designs method is main means, and proposes a kind of long fiber composites rear seat of passenger car bone with this
Frame original material design method.
In order to solve the above technical problems, the present invention is achieved by the following technical scheme:
A kind of long fiber composites rear seat of passenger car skeleton original material design method, comprising the following steps:
Step 1: rear seat of passenger car minibus requirement is determined；
Step 2: LFT plate critical impact energy expression formula is derived；
Step 3: research requires lower LFT plate material design method based on impact energy；
Step 4: design seat back skeleton original material；
Step 5: verifying initial designs result finite element and test.
Determining rear seat of passenger car minibus described in step 1 require, in particular to:
(1) according to " test method of luggage displacement occupant restraint device " in GB15083-2006, for back row seat of automobile
The certification of chair impact strength provides, the impact test of seat is carried out using sled test platform；
(2) test sample block size is 300mm × 300mm × 300mm, edge chamfering 20mm, quality 18kg, test sample
Block installation is placed on the floor of luggage compartment, longitudinal horizontal distance for having 200mm with skeleton；
(3) test sample block is two pieces, there is the lateral distance of 50mm between two test sample blocks, and what trolley was applied in test subtracts
Rate curve meets " test method of luggage displacement occupant restraint device " and requires；
(4) during testing and after test, if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements；
During test, chair framework and its fastener is allowed to deform, condition be test the front profile of skeleton and head rest cannot be to
Front is beyond a lateral vertical plane, and to head rest, this plane passes through seat R-point, i.e. point in front of R point at 150mm；To seat
Chair skeleton part, this plane is by the point at 100mm in front of seat R point.
The critical impact energy expression formula of derivation LFT plate described in step 2, comprising the following steps:
First, determining LFT plate critical impact energy, there is power function relationships with LFT plate fiber overall thickness:
Using the density value of glass fibre and PP matrix, fiber quality score is scaled fiber volume fraction Vf, then count
Calculation obtains fiber total thickness t × V of form of ownership LFT platef, by critical impact energy UminpWith fiber overall thickness by formula (1) into
As a result row nonlinear fitting is shown in logarithmic coordinates system；
Uminp=K × (t × Vf)β (1)
K and β is the material parameter determining by test in formula；
Second, respectively to the residual speed and initial punching after the drop impact difference fiber quality score plate of different-diameter
Speed is hit, and carries out nonlinear fitting using formula (2), obtains critical speed of dropping hammer；
Wherein: vrFor the rebound velocity that drops hammer, vlFor critical speed of dropping hammer, v0For initial impact speed of dropping hammer, k is fitting ginseng
Number；
Third calculates the critical speed of all plates that fitting obtains according to formula (3), obtains difference and drops hammer diameter
When LFT plate critical impact energy Uminp；
mpExpression is dropped hammer quality；
4th, the critical impact energy of the different diameters that drop hammer is subjected to nonlinear fitting using formula (4), fitting result is drawn
In figure, obtain difference drop hammer diameter impact when, critical impact energy and fiber overall thickness logarithmic plot；
Uminp=K × (t × Vf)β (4)
In formula: K and β is the material parameter determining by test, and t is slab-thickness, VfFor fiber volume fraction；
5th, formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as certainly
Variable, shown in formula (5):
Uminp=K (tVf·Dt)β (5)
DtExpression is dropped hammer diameter；
6th: theoretical calculation and simulation result by comparing LFT plate critical impact energy verify minimal penetration
The accuracy of energy theory expression formula.
Research described in step 3 is based on impact energy and requires lower LFT plate material design method, comprising the following steps:
First: using critical impact energy as bridge, it is established that plate energy-absorbing requires the relationship between material parameter
Formula (8)；
Known LFT energy absorption analysis model are as follows:
Acquire UminpAre as follows:
Wherein UimpFor drop impact energy, UabsEnergy, U are absorbed for plateimpAnd UabsValue range be [0,
Uminp]；
Formula (5) and (7), which are combined, must contact:
Then: on the one hand estimating LFT plate limit impact energy using formula (8), LFT material is on the other hand instructed initially to set
Meter and selection:
Assuming that thickness, the fiber volume fraction of the known LFT plate, and assume impact body diameter, while understanding impact body
The energy-absorbing requirement of plate, i.e. U when reboundabsIt has been determined that from right to left according to formula (8), impact body limit impact energy is calculated
Amount, and then acquire the limit impact initial velocity of impact body；
Assuming that in the case where determining the two impact working conditions of impact energy and impact body diameter, from the angle of safety coefficient,
The approximate range that setting LFT plate needs to absorb impact energy calculates from left to right according to (8), obtains LFT material fiber body
Fraction and corresponding slab-thickness, realize the initial designs of material.
Seat back skeleton original material, including content in detail below are designed described in step 4:
Luggage case block Shock Environmental Condition is simplified, the first of material is carried out to LFT seat back plate structure using formula (8)
The design that begins and selection；
Using single luggage block impact backboard as research object, it is reduced to drop impact LFT slab construction, definition is dropped hammer
Diameter, quality and initial impact speed, wherein the side length of luggage block to be considered as to the diameter to drop hammer；
Be not pierced from plate and safety coefficient from the point of view of, calculate separately, when plate absorb energy Uabs, account for and drop hammer
LFT fiber quality score and corresponding slab-thickness when the ratio of impact energy is 100%, 90%, 80% and 70%, after the completion
Arrange the initial designs of seat back skeleton.
Verifying initial designs result finite element and test described in step 5, comprising the following steps:
(1) a kind of LFT material of mass fraction is selected, the metal material of back seat backboard skeleton is replaced, utilization is limited
Meta analysis software establishes the simulation model of luggage case block impact test, by the finite element model of foundation and sled test result pair
Than verifying the validity of LFT material model；
(2) backboard skeleton thickness is adjusted, carries out calculating the satisfactory seat back thickness value of acquisition, be inhaled with based on energy
It is close to receive the seat back plate structure initial designs method thickness value that analysis model carries out；It is proved with this, is analyzed using energy absorption
Model carries out the feasibility and validity of original material design to LFT seat back plate structure.
Compared with prior art the beneficial effects of the present invention are:
1. long fiber composites rear seat of passenger car skeleton original material design method of the present invention considers multiple
The strain rate effect that condensation material mechanical characteristic is shown, by nonlinear fitting set up critical impact energy and material parameter and
Relationship between parameter of dropping hammer.
2. long fiber composites rear seat of passenger car skeleton original material design method of the present invention is flat with LFT
Plate critical impact energy sets up energy absorption capability and material parameter and tests the bridge of constraint condition parameter association.On the one hand
It can estimate LFT plate limit impact energy, on the other hand can instruct LFT material initial designs and selection.Assuming that known should
The thickness of LFT plate, fiber volume fraction and impact condition, at the same when understanding impact rebound plate energy-absorbing requirement, then can be with
Impact body limit impact energy is calculated, and then acquires the limit initial velocity of impact body.In addition, having more the practical meaning of engineering
The application of justice is assumed that in the case where determining impact operating condition, needs to absorb impact energy from the angle initialization LFT plate of safety coefficient
LFT material fiber volume fraction and corresponding slab-thickness can be calculated in approximate range, realize material initial designs.
Detailed description of the invention
The present invention will be further described below with reference to the drawings:
Fig. 1 is the process of long fiber composites rear seat of passenger car skeleton original material of the present invention design
Figure；
Fig. 2 is the test sample of long fiber composites rear seat of passenger car skeleton original material of the present invention design
Block quality and its layout drawing；
Fig. 3 is that the trolley of long fiber composites rear seat of passenger car skeleton original material of the present invention design subtracts
Speed curve diagram；
Fig. 4 is that the LFT of long fiber composites rear seat of passenger car skeleton original material of the present invention design is flat
Plate critical impact energy and fiber overall thickness logarithmic plot；
Fig. 5-1 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 20%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 24mm；
Fig. 5-2 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 30%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 24mm；
Fig. 5-3 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 40%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 24mm；
Fig. 6-1 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 20%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 16mm；
Fig. 6-2 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 30%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 16mm；
Fig. 6-3 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 40%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 16mm；
Fig. 7-1 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 20%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 8mm；
Fig. 7-2 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 30%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 8mm；
Fig. 7-3 is dropping hammer for long fiber composites rear seat of passenger car skeleton original material of the present invention design
Fiber quality score is that 40%LFT plate drops hammer residual speed and initial impact speed curve diagram when diameter 8mm；
Fig. 8 is that the difference of long fiber composites rear seat of passenger car skeleton original material of the present invention design is fallen
Critical impact energy and fiber overall thickness logarithmic plot when hammering diameter impact into shape；
Fig. 9 is that the minimum of long fiber composites rear seat of passenger car skeleton original material of the present invention design is worn
The logarithmic plot of saturating energy and fiber overall thickness and diameter product of dropping hammer；
Figure 10 is the minimum of long fiber composites rear seat of passenger car skeleton original material of the present invention design
Penetrating capacity theoretical calculation is to simulation result comparison diagram；
Specific embodiment
The present invention is explained in detail with reference to the accompanying drawing:
Long fiber composites rear seat of passenger car skeleton initial designs method flow diagram such as Fig. 1 institute of the present invention
Show, first, in accordance with relevant laws and regulations, the clear minibus requirement for rear seat of passenger car erects limit element artificial module；
Secondly, it is established that the relationship between LFT plate critical impact energy and slab-thickness, fiber volume fraction and drop impact, it is complete
It is derived at critical impact energy expression formula；Then, according to the critical impact energy of LFT plate both with drop impact energy and plate
It is related and related to material fiber overall thickness and the diameter that drops hammer to absorb energy, therefore is built using critical impact energy as bridge
It erects plate energy-absorbing and requires contacting between Material Design；Then, luggage case block Shock Environmental Condition is simplified,
The initial designs and selection of material are carried out to LFT seat back plate structure using LFT plate material design method；Finally, by having
It limits first emulation mode or the fiber quality score of selection and the seat back skeleton of thickness is verified in test trial-production, it was demonstrated that material
Expect the validity of design method.
The long fiber composites rear seat of passenger car skeleton original material design method is as follows:
1. determining the requirement of rear seat of passenger car minibus
" test method of luggage displacement occupant restraint device " impacts automobile rear seat strong in GB15083-2006
The certification regulation of degree carries out the impact test of seat using sled test platform.Test sample block size be 300mm × 300mm ×
300mm, edge chamfering 20mm, quality 18kg.The position of test sample block installation is as shown in Fig. 2, place the ground with luggage compartment
On plate, longitudinal horizontal distance for having 200mm with skeleton；There is the lateral distance of 50mm between two test sample blocks, trolley institute in test
The projectile deceleration history of application is as shown in Figure 3.
During test and test after if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements.It is trying
During testing, chair framework and its fastener is allowed to deform, condition is to test skeleton and the front profile of head rest cannot be forwards
Beyond a lateral vertical plane, to head rest, this plane passes through seat R-point, i.e. point in front of R point at 150mm；To seat bone
Frame part, this plane is by the point at 100mm in front of seat R point.
2.LFT plate critical impact energy expression formula derives
G.Caprino has found that penetrating capacity not only has phase with material parameter when studying composite laminated plate impact characteristics
Close property and also with this loading environment existence function relationship of diameter of dropping hammer.It is not difficult to find out that LFT plate critical impact energy is connection
Energy absorption capability and material parameter and the important bridge for testing constraint condition parameter.
The product of slab-thickness and fiber volume fraction is defined as fiber overall thickness in composite material laminated board, is to influence
The major parameter of penetrating capacity, and there are power function relationships with it.Using the density value of glass fibre and PP matrix by cellulosic
Amount score is scaled fiber volume fraction Vf, then fiber overall thickness (t × V of form of ownership LFT plate has been calculatedf), it will most
Small penetrating capacity UminpNonlinear fitting is carried out by formula (1) with fiber overall thickness, is as a result shown in logarithmic coordinates system.
Uminp=K × (t × Vf)β (1)
K and β is the material parameter determining by test in formula.
Determining LFT plate critical impact energy, there is power function relationships with its fiber overall thickness.
Unquestionably, it is flat that the variation for shape of dropping hammer under the premise of drop impact energy is constant can seriously affect composite material
The penetrating capacity of plate, wherein the diameter that drops hammer is typical geometric parameter.Therefore, that tup quality in drop impact model is certain
Under the premise of, carry out a variety of tup diameter calculations.
Respectively to the residual speed and initial impact speed after the drop impact difference fiber quality score plate of different-diameter
Degree, and nonlinear fitting is carried out using formula (2), obtain critical speed of dropping hammer.
Wherein vrFor the rebound velocity that drops hammer, vlFor critical speed of dropping hammer, v0For initial impact speed of dropping hammer, k is fitting ginseng
Number.
The critical speed of all plates that fitting obtains is calculated according to formula (3), obtain difference drop hammer diameter when LFT
The critical impact energy U of plateminp。
The critical impact energy of the different diameters that drop hammer is subjected to nonlinear fitting using formula (4), fitting result is drawn on figure
In, obtain difference drop hammer diameter impact when critical impact energy and fiber overall thickness logarithmic plot.
Uminp=K (tVf)β (4)
It can be seen that the curve being fitted under the different diameters that drop hammer will not intersect in research range, or even approximate mutually equal
Row.Therefore, formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as independent variable,
As shown in formula (5).
Uminp=K (tVf·Dt)β (5)
The LFT plate critical impact energy obtained under the conditions of different-diameter drop impact is subjected to Nonlinear Quasi with formula (5)
It closes, obtains the expression formula of critical impact energy.
By comparing the theoretical calculation and simulation result of LFT plate critical impact energy, critical impact energy is verified
The accuracy of theoretical expression.
3. requiring lower LFT plate material design method research based on impact energy
The critical impact energy of LFT plate was not only related to drop impact energy and plate absorption energy, but also and material fiber
Overall thickness and diameter correlation of dropping hammer, therefore can establish the requirement of plate energy-absorbing and material using critical impact energy as bridge
Relationship between parameter.
Known LFT energy absorption analysis model are as follows:
It can be in the hope of UminpAre as follows:
Wherein UimpFor drop impact energy, UabsEnergy, U are absorbed for plateimpAnd UabsValue range be [0,
Uminp]。
Formula (5) and (7), which are combined, must contact:
In the case where energy absorption analysis model determines, it on the one hand can estimate that the LFT plate limit is impacted using formula (8)
On the other hand energy can instruct LFT material initial designs and selection.Assuming that the thickness of the known LFT plate, fiber volume fraction
Several and impact body diameter, while understanding the energy-absorbing requirement of plate when impact body is sprung back, i.e. UabsIt has been determined that then according to formula (8) from
Impact body limit impact energy is calculated in right-to-left, and then acquires the limit impact initial velocity of impact body.Furthermore it has more
The application of practical meaning in engineering assumes that under the conditions of determining impact energy and impact body diameter, from the angle initialization of safety coefficient
LFT plate needs to absorb the approximate range of impact energy, then LFT material fiber body can be calculated from left to right according to (8)
Fraction and corresponding slab-thickness, realize the initial designs of material.
4. seat back skeleton original material designs
First luggage case block Shock Environmental Condition is simplified, to carry out material to LFT seat back plate structure using formula (8)
The initial designs and selection of material.Rear seat of passenger car generallys use the structure type of " four or six points " and " five or five points ", in luggage
Block can be approximately considered the seat back plate structure that each luggage block only hits the front when impacting, between there is no reciprocal effect.Cause
This, using single luggage block impact backboard as research object, be reduced to drop impact LFT slab construction, define drop hammer it is straight
Diameter, quality and initial impact speed, wherein the side length of luggage block to be considered as to the diameter to drop hammer.It is not pierced from plate and safety is
From the point of view of number, calculate separately when plate absorbs energy UabsThe ratio for accounting for drop impact energy is 100%, 90%, 80% He
LFT fiber quality score and corresponding slab-thickness when 70% complete the initial designs of heel row seat back skeleton.
5. initial designs result finite element and verification experimental verification
The metal material for selecting a kind of LFT material replacement back seat backboard skeleton of mass fraction, utilizes finite element fraction
Analysis software establishes the simulation model of luggage case block impact test to simulate, by the finite element model of foundation and sled test result pair
Than verifying the validity of LFT material model.
On this basis, the thickness value and be based on energy absorption analysis model that adjustment backboard skeleton thickness is calculated
It is close that original material design thickness is carried out to LFT seat back plate structure, it was demonstrated that using energy absorption analysis model to LFT seat back
Hardened structure carries out the feasibility and validity of original material design.
Embodiment:
Next the present invention combines example introduction to utilize long fiber composites rear seat of passenger car proposed by the present invention
The process of skeleton original material design method.
1. determining the requirement of rear seat of passenger car minibus
" test method of luggage displacement occupant restraint device " impacts automobile rear seat strong in GB15083-2006
The certification regulation of degree carries out the impact test of seat using sled test platform.Test sample block size be 300mm × 300mm ×
300mm, edge chamfering 20mm, quality 18kg.The position of test sample block installation is as shown in Fig. 2, place the ground with luggage compartment
On plate, longitudinal horizontal distance for having 200mm with skeleton；There is the lateral distance of 50mm between two test sample blocks, trolley institute in test
The projectile deceleration history of application is as shown in Figure 3.
During test and test after if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements.It is trying
During testing, chair framework and its fastener is allowed to deform, condition is to test skeleton and the front profile of head rest cannot be forwards
Beyond a lateral vertical plane, to head rest, this plane passes through seat R-point, i.e. point in front of R point at 150mm；To seat bone
Frame part, this plane is by the point at 100mm in front of seat R point.
2.LFT plate critical impact energy expression formula derives
Calculated diameter is the drop impact model of 24mm, and LFT plate critical impact energy is as shown in table 1, utilizes glass fibers
Fiber quality score is scaled fiber volume fraction V by the density value of peacekeeping PP matrixf, then form of ownership LFT is calculated and puts down
Fiber overall thickness (t × V of platef), by critical impact energy UminpNonlinear fitting is carried out by formula (1) with fiber overall thickness, as a result
Fig. 4 is shown in display in logarithmic coordinates system.
Table 1LFT plate critical impact energy
| ω=20% | ω=30% | ω=40% | |
| T=2mm | 8.58 | 11.16 | 15.02 |
| T=3mm | 14.02 | 17.82 | 21.33 |
| T=4mm | 20.43 | 24.93 | 27.98 |
K=30.69 in fitting result, β=0.702, R2=0.914, show that calculate data has with fit correlation curve
Good consistency.LFT plate critical impact energy has been determined, and there is power function relationships with its fiber overall thickness.
Shape of dropping hammer under the premise of drop impact energy is constant can seriously affect the penetrating capacity of composite material flat plate,
In the diameter that drops hammer be typical geometric parameter, guarantee that the quality of tup is 1kg, setting diameter is counted for 24mm, 16mm and 8mm
It calculates.
It is flat that Fig. 5, Fig. 6 and Fig. 7 list the drop impact difference fiber quality score that diameter is 24mm, 16mm and 8mm respectively
Residual speed and initial impact speed after plate, and nonlinear fitting is carried out to data using formula (2).Parameter is shown in fitting result
Table 2, table 3 and table 4.Can clearly be seen that each matched curve and data all has extraordinary consistency.
Table 2 drop hammer diameter be 24mm LFT plate critical speed fitting parameter
| LFT flat type | vl | k | R2 |
| T=2mm, ω=20% | 4.14 | 1.80 | 0.999 |
| T=3mm, ω=20% | 5.30 | 1.81 | 0.999 |
| T=4mm, ω=20% | 6.40 | 1.84 | 0.999 |
| T=2mm, ω=30% | 4.72 | 1.84 | 0.999 |
| T=3mm, ω=30% | 5.97 | 1.90 | 0.999 |
| T=4mm, ω=30% | 7.06 | 1.83 | 0.999 |
| T=2mm, ω=40% | 5.48 | 1.88 | 0.999 |
| T=3mm, ω=40% | 6.53 | 1.87 | 0.999 |
| T=4mm, ω=40% | 7.84 | 1.79 | 0.999 |
Table 3 drop hammer diameter be 16mm LFT plate critical speed fitting parameter
Table 4 drop hammer diameter be 8mm LFT plate critical speed fitting parameter
By the critical speed of all plates that fitting obtains according to formula (3) be calculated difference drop hammer diameter when LFT
Critical impact energy Uminp, calculated result is as shown in table 5.
Table 5 drop hammer diameter 24mm, 16mm and 8mmm when LFT plate critical impact energy
Diameter will be dropped hammer as the critical impact energy progress nonlinear fitting of 24mm, 16mm and 8mm using formula (4), be fitted
As a result be drawn in figure, obtain difference drop hammer diameter impact when critical impact energy and fiber overall thickness logarithmic plot, such as Fig. 8
It is shown.As can be seen from the figure the curve being fitted under three diameters that drop hammer will not intersect in research range, or even approximate mutual
In parallel.Therefore formula (4) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as change certainly
Amount, carries out nonlinear fitting with formula (5) for the LFT plate critical impact energy obtained under the conditions of three kinds of diameter drop impacts, intends
Comparing result such as Fig. 9 of curve and data after conjunction, it can be seen that the two has good consistency.Critical impact energy at this time
Expression formula are as follows:
Uminp=1.72 (tVf·Dt)0.928 (9)
Wherein, it is fitted variance R2=0.901.Figure 10 compares the calculated results of LFT plate critical impact energy, can be with
Find out that most data point is distributed in ± 10% error range, demonstrates the accurate of critical impact energy theoretical expression
Property.
3. requiring lower LFT plate material design method research based on impact energy
The critical impact energy of LFT plate was not only related to drop impact energy and plate absorption energy, but also and material fiber
Overall thickness and diameter correlation of dropping hammer, therefore can establish the requirement of plate energy-absorbing and material using critical impact energy as bridge
Relationship between parameter.
Known LFT energy absorption analysis model is formula (7), can be in the hope of UminpFor formula (8), formula (7) and (9) are combined
It can must contact:
In the case where energy absorption analysis model determines, it on the one hand can estimate that the LFT plate limit is rushed using formula (10)
Energy is hit, LFT material initial designs and selection on the other hand can be instructed.Assuming that the thickness of the known LFT plate, fiber volume
Score and impact body diameter this impact condition, at the same when understanding impact body rebound plate energy-absorbing requirement, i.e. UabsIt has been determined that
Then impact body limit impact energy is calculated according to formula (10) from right to left, and then acquires the initial speed of limit impact of impact body
Degree.Furthermore it assumes that with more the application of practical meaning in engineering in the case where determining impact working condition, i.e. UimpWith impact body diameter
It determines, needs to absorb the approximate range of impact energy from the angle initialization LFT plate of safety coefficient, then it can be according to (10) from a left side
LFT material fiber volume fraction and corresponding slab-thickness is calculated to the right side, realizes the initial designs of material.
4. seat back skeleton original material designs
Luggage case block Shock Environmental Condition is simplified, to carry out material to LFT seat back plate structure using formula (10)
The initial designs and selection of material.The rear seat of passenger car structure type for choosing " four or six points ", can be close in the impact of luggage block
Seemingly think that each luggage block only hits the seat back plate structure of the front, between do not influence.Therefore, with the impact of single luggage block
Backboard is research object, is reduced to drop impact LFT slab construction, and defining the diameter Dt to drop hammer is 300mm, i.e. luggage block
Side length, quality 18kg, initial impact speed be 8.57m/s, so the initial impact energy U to drop hammermin pFor 660J.From
Plate is not hungry penetrate and safety coefficient from the point of view of, calculate separately when plate absorbs energy UabsAccount for the ratio of drop impact energy
LFT fiber quality score and corresponding slab-thickness when example is 100%, 90%, 80% and 70%.
The fiber quality fraction range of usually used LFT is 20% to 50% in automotive body structure.Therefore, formula is utilized
(10) the LFT slab-thickness t for being 20%, 30%, 40% and 50% to mass fraction is calculated, corresponding fiber volume fraction
Are as follows: 9.77%, 15.7%, 22.4% and 30.2%, the results are shown in Table 6.
Material thickness calculates under 6 different quality containing LFT material difference safety coefficient of table
As can be seen from the table with the increase of fiber quality score, each thickness for absorbing LFT plate under energy condition
Also reduce therewith, maximum value is about times of minimum value.When the ratio for absorbing energy and impact energy is gradually reduced, i.e., safety coefficient increases
When big, slab-thickness is also obviously increased, and maximum value is about 8 times of minimum value.
Initial designs can be carried out to back seat backboard skeleton according to data in table, when the best fibre of selection mechanical property
When tieing up the LFT of mass fraction 50%, the minimum thickness of seat back is 12.33mm；As the LFT of selection fiber quality score 40%
When, the minimum thickness of backboard is 16.62mm, and so on.
5. initial designs result finite element and verification experimental verification
Fiber quality score is selected to replace the metal material of back seat backboard skeleton for 50% LFT, armchair structure adopts
With the form of " four or six points ".The top of two parts backboard skeleton passes through center latch and is connected with body construction, during bottom then utilizes
Between and two side stands connect with body construction.
Luggage case block impact test simulation model is established using finite element software Ls-Dyna, wherein LFT is using in software 24
On the one hand the simulation of number elastic-plastic material model considers that the distribution randomness of the fiber when fiber quality score is 50% more greatly may be used
Isotropic material is regarded as with approximation, is on the other hand to improve computational efficiency.Pass through setting failure plasticity in material model
Strain comes whether judgement material is destroyed.
By the finite element model of foundation and sled test Comparative result, the validity of LFT isotropic material model is verified,
The grid of finite element model is exactly to be established according to the geometrical model of preproduction workpiece.
On this basis, adjustment backboard skeleton thickness is calculated, and is found when with a thickness of 15mm, chair framework can expire
Sufficient laws and regulations requirement, this result, which can prove amply, carries out initially LFT seat back plate structure using energy absorption analysis model
The feasibility and validity of design of material.
Claims (1)
1. a kind of long fiber composites rear seat of passenger car skeleton original material design method, which is characterized in that including with
Lower step:
Step 1: rear seat of passenger car minibus requirement is determined；
Step 2: LFT plate critical impact energy expression formula is derived；
Step 3: research requires lower LFT plate material design method based on impact energy；
Step 4: design seat back skeleton original material；
Step 5: initial designs result is verified by test and finite element；
Determining rear seat of passenger car minibus described in step 1 require, in particular to:
(1) according to " test method of luggage displacement occupant restraint device " in GB15083-2006, automobile rear seat is rushed
The certification of hit intensity provides, the impact test of seat is carried out using sled test platform；
(2) test sample block size is 300mm × 300mm × 300mm, edge chamfering 20mm, quality 18kg, test sample block peace
It puts and sets on the floor of luggage compartment, longitudinal horizontal distance for having 200mm with skeleton；
(3) test sample block is two pieces, there is the lateral distance of 50mm, the deceleration that trolley is applied in test between two test sample blocks
Curve meets " test method of luggage displacement occupant restraint device " and requires；
(4) during testing and after test, if seat and backrest lock still keep origin-location, then it is assumed that meet the requirements；It is trying
During testing, chair framework and its fastener is allowed to deform, condition is to test skeleton and the front profile of head rest cannot be forwards
Beyond a lateral vertical plane, to head rest, this plane passes through seat R point, i.e. point in front of R point at 150mm；To chair framework portion
Point, this plane is by the point at 100mm in front of seat R point；
The critical impact energy expression formula of derivation LFT plate described in step 2, comprising the following steps:
First, determining LFT plate critical impact energy, there is power function relationships with LFT plate fiber overall thickness:
Using the density value of glass fibre and PP matrix, fiber quality score is scaled fiber volume fraction Vf, then be calculated
Fiber total thickness t × V of form of ownership LFT platef, by critical impact energy UminpIt is non-thread by formula (1) progress with fiber overall thickness
Property fitting, as a result shown in logarithmic coordinates system；
Uminp=K × (t × Vf)β (1)
K and β is the material parameter determining by test in formula；
T is slab-thickness；
Second, residual speed and initial impact speed after obtaining different-diameter drop impact difference fiber quality score plate,
And nonlinear fitting is carried out using formula (2), obtain critical speed of dropping hammer；
Wherein: vrFor the rebound velocity that drops hammer, vlFor critical speed of dropping hammer, v0For initial impact speed of dropping hammer, k is fitting parameter；
Third calculates the critical speed of all plates that fitting obtains according to formula (3), obtain difference drop hammer diameter when
The critical impact energy U of LFT plateminp；
mpExpression is dropped hammer quality；
4th, the critical impact energy of the different diameters that drop hammer is subjected to nonlinear fitting using formula (1), fitting result is drawn on figure
In, obtain difference drop hammer diameter impact when, critical impact energy and fiber overall thickness logarithmic plot；
5th, formula (1) is modified, using the product of LFT slab-thickness, fiber volume fraction and the diameter that drops hammer as change certainly
Amount, shown in formula (5):
Uminp=K × (t × Vf×Dt)β (5)
DtExpression is dropped hammer diameter；
6th: theoretical calculation and simulation result by comparing LFT plate critical impact energy verify critical impact energy
The accuracy of theoretical expression；
Research described in step 3 is based on impact energy and requires lower LFT plate material design method, comprising the following steps:
First: using critical impact energy as bridge, it is established that plate energy-absorbing requires the relational expression between material parameter
(8)；
Known LFT energy absorption analysis model are as follows:
Acquire UminpAre as follows:
Wherein UimpFor drop impact energy, UabsEnergy, U are absorbed for plateimpAnd UabsValue range be [0, Uminp]；
Formula (5) and (7), which are combined, must contact:
Then: using formula (8) on the one hand estimation LFT plate limit impact energy, on the other hand instruct LFT material initial designs and
Selection:
Assuming that thickness, the fiber volume fraction of the known LFT plate, and assume the diameter of impact body, while understanding impact body and returning
The energy-absorbing requirement of plate, i.e. U when bulletabsIt has been determined that from right to left according to formula (8), impact body limit impact energy is calculated,
And then acquire the limit impact initial velocity of impact body；
Assuming that in the case where determining the two impact working conditions of impact energy and impact body diameter, from the angle of safety coefficient, setting
LFT plate needs to absorb the range of impact energy, according to (8), calculates from left to right, obtain LFT material fiber volume fraction and
Corresponding slab-thickness realizes the initial designs of material；
Seat back skeleton original material, including content in detail below are designed described in step 4:
Luggage case block Shock Environmental Condition is simplified, initially setting for material is carried out to LFT seat back plate structure using formula (8)
Meter and selection；
Using single luggage block impact backboard as research object, be reduced to drop impact LFT slab construction, define drop hammer it is straight
Diameter, quality and initial impact speed, wherein the side length of luggage block to be considered as to the diameter to drop hammer；
Be not pierced from plate and safety coefficient from the point of view of, calculate separately, when plate absorb energy Uabs, account for drop impact
LFT fiber quality score and corresponding slab-thickness when the ratio of energy is 100%, 90%, 80% and 70% complete rear row seat
The initial designs of chair back framework；
Initial designs result is verified by test and finite element described in step 5, comprising the following steps:
(1) a kind of LFT material of mass fraction is selected, the metal material of back seat backboard skeleton is replaced, utilizes finite element fraction
Software is analysed, the simulation model of luggage case block impact test is established, the finite element model of foundation and sled test Comparative result is tested
Demonstrate,prove the validity of LFT material model；
(2) backboard skeleton thickness is adjusted, carries out calculating the satisfactory seat back thickness value of acquisition, divide with based on energy absorption
It is close to analyse the seat back plate structure initial designs method thickness value that model carries out；It is proved with this, using energy absorption analysis model,
The feasibility and validity of original material design are carried out to LFT seat back plate structure.
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