CN103926152B - A kind of high temperature multiaxis spectrum is low all creep-fatigue lifetime estimation methods under carrying - Google Patents

Abstract

A kind of high temperature multiaxis spectrum is low all creep fatigue life appraisal procedures under carrying, and steps of the method are: read multiaxial loading modal data block internal stress strain history, seek equivalent strain, carry out load history arrangement；Relative equivalent strain multiaxis method of counting is used to extract repeatedly；Unified Multiaxial Fatigue Damage Life Prediction Model is used to seek each fatigue damage repeatedly；Fatigue damage adds up, and seeks total fatigue damage；Former load history is utilized to seek equivalence creep stress；In conjunction with creep rupture equation, seek creep impairment Dc according to equivalence creep stress and stress course；Ask this multiaxial loading spectrum block under high temperature to cause and always damage D；Estimation multi-axial creep fatigue life.Fatigue damage under Multiaxial stress and the creep impairment under Multiaxial stress are calculated in whole loading spectrum data block by the method respectively, Fatigue Damage Calculation uses the tired material constant under room temperature, creep impairment calculates the stress rupture equati$ material constant that code requirement is recommended, and obtains preferable prediction effect by verification experimental verification.

Description

A kind of high temperature multiaxis spectrum is low all creep-fatigue lifetime estimation methods under carrying

Technical field

The present invention relates to fatigue strength field, refer in particular to multiaxis block under hot conditions and carry the low creep-fatigue life-span in week Appraisal procedure.

Background technology

High-temerature creep fatigue design is the design of the high temperature strength of parts such as aero-engine, combustion gas turbine Important content.The loading that actual in commission pieces of equipment is born is complicated and diversified, is setting The meter stage can not reproduce the military service load history of reality completely, and uses loading spectrum block to parts load Being simulated just becoming the indispensable means of part fatigue design, creep fatigue is that restriction aviation is sent out The major reason of the high temperature parts such as motivation, combustion gas turbine, thus low all multi-axial creep-fatigue under block load Damage estimation and biometry obtain in these high-temperature components design and are widely applied.

High-temerature creep fatigue damage and Life Prediction Model are more common in the fatigue under simple stress and creep at present Intensity Design, and the actual high-temperature component being on active service is often to be on active service under multiaxial loading effect, traditional list Tired and single shaft creep the theory of axle tends not to well meet the need of these high-temperature component Intensity Design Want.Therefore under the conditions of high temperature multiaxis block carries, the research of creep fatigue damage and biometry has important grinding Study carefully value.

Summary of the invention

Present invention aim at the requirement for high temperature low-cycle fatigue Intensity Design, propose high temperature multiaxis spectrum and carry Under low week creep-fatigue lifetime estimation method.

Low all creep-fatigue lifetime estimation methods under a kind of high temperature multiaxis spectrum load provided by the present invention, its step Suddenly it is:

1, low all creep-fatigue lifetime estimation methods under a kind of high temperature multiaxis spectrum load, this step includes as follows,

Step 1): read multiaxis spectrum and carry data block internal stress strain history data, utilize Mises criterion to ask Go out equivalent strain ε of each point_eq, loading spectrum is disconnected at maximum equivalent strain, and load before this point is gone through Number of passes is last according to moving to load history, obtains new load history；

Mises equivalent strain is ${\mathrm{\ϵ}}_{\mathrm{eq}}=\frac{\sqrt{2}}{3}\sqrt{{({\mathrm{\ϵ}}_x-{\mathrm{\ϵ}}_y)}^2+{({\mathrm{\ϵ}}_y-{\mathrm{\ϵ}}_z)}^2+{({\mathrm{\ϵ}}_z-{\mathrm{\ϵ}}_x)}^2+\frac{3}{2}({\mathrm{\γ}}_{\mathrm{xy}}^2+{\mathrm{\γ}}_{\mathrm{yz}}^2+{\mathrm{\γ}}_{\mathrm{zx}}^2)}$

Wherein ε_x,ε_y,ε_zIt is respectively x, y, z direction direct stress γ_xy,γ_yz,γ_zxIt is respectively xy, yz, zx plane On shear stress, ε_x,ε_y,ε_zAnd γ_xy,γ_yz,γ_zxCarry in data block from multiaxis spectrum and read, ε_eqFor effects such as Mises Power；

Step 2): utilize relative strain multiaxis method of counting, load history is counted, counts out load In course all repeatedly；

Step 3): according to unified Multiaxial Fatigue Life Prediction model, repeatedly calculate what it caused to each Fatigue damage；

Unified Multiaxial Fatigue Life Prediction model is:

$\frac{{\mathrm{\Δ\ϵ}}_{\mathrm{eq}}^{\mathrm{cr}}}{2}={[{\mathrm{\ϵ}}_n^{*2}+\frac{1}{3}{({\mathrm{\Δ\γ}}_{\max }/2)}^2]}^{1/2}$

$\frac{{\mathrm{\Δ\ϵ}}_{\mathrm{eq}}^{\mathrm{cr}}}{2}=\frac{{\mathrm{\σ}\text{'}}_f}{E}{\left({2N}_f\right)}^b+{\mathrm{\ϵ}\text{'}}_f{\left({2N}_f\right)}^c$

Obtain damage ${\stackrel{\·}{D}}_f=1/N_f$

Wherein Δ γ_maxFor this repeatedly in maximum shear strain scope on maximum shear strain range plane,For Δγ_maxInstitute on the whole this repeatedly in normal strain amplitude,For the equivalent strain width under multiaxial loading,Draw according to course data, σ '_fFor fatigue strength coefficient, E is elastic modelling quantity, and b is tired Labor intensity index, ε '_fFor tired plastic coefficient, c is tired plasticity index, σ '_f、E、b、c、ε'_fFor material Material underlying parameter, can obtain from Materials Handbook, N_fThe life-span of this course repeatedly is experienced for material,For Material experiences this damage repeatedly caused；

Step 4): cumulative each repeatedly cause fatigue damage, obtains total fatigue damage Df；

$D_f=\mathrm{\Σ}{\stackrel{\·}{D}}_f$

Wherein D_fDamage material caused for one loading spectrum block of experience,For each repeatedly to material The damage caused；

Step 5): utilize former load history data and each point equivalent stress obtained, with this point and adjacent under The half of the average equivalent stress of any is as creep stress σ；

$\mathrm{\σ}=\frac{{\mathrm{\σ}}_{\mathrm{eq}}{|}_{n=n0}+{\mathrm{\σ}}_{\mathrm{eq}}{|}_{n=n0+1}}{4}$

Wherein n=n0 represents the n-th 0 points, and n0+1 is its consecutive points,

${\mathrm{\&sigma;}}_{\mathrm{eq}}=\frac{1}{\sqrt{2}}\sqrt{{(<{\mathrm{\&sigma;}}_x>-<{\mathrm{\&sigma;}}_y>)}^2+{(<{\mathrm{\&sigma;}}_y>-<{\mathrm{\&sigma;}}_z>)}^2+{(<{\mathrm{\&sigma;}}_z>-<{\mathrm{\&sigma;}}_x>)}^2+6({\mathrm{\&tau;}}_{\mathrm{xy}}^2+{\mathrm{\&tau;}}_{\mathrm{yz}}^2+{\mathrm{\&tau;}}_{\mathrm{zx}}^2)}$

Wherein<>is MacCauley symbol, represents when in bracket, number, more than or equal to zero, takes former numerical value, little 0 is taken in zero；σ_x,σ_y,σ_zIt is respectively x, the direct stress in y, z direction；τ_xy,τ_yz,τ_zxIt is respectively xy, yz, Shear stress in zx plane, σ_x,σ_y,σ_z,τ_xy,τ_yz,τ_zxObtain in load history block；σ_eqFor equivalent stress；

Step 6): be this creep time t' with the time interval of adjacent two data points, according to creep rupture The creep impairment of all each points of Equation for Calculating, and cumulative seek creep impairment Dc；

Stress rupture equati$ lgt=b₁+b₂T+b₃x/T+b₄x²/T+b₅x³/T

Wherein t is the persistent period that material can stand under this stress effect of this temperature, intermediate variable T Computational methods be T=(9 θ/5+32)+460, intermediate variable x=lg σ, σ are the creep that step 5) is obtained Stress, b1, b2, b3, b4, b5 are material constant, obtain from Materials Handbook, and θ is temperature,

Thus can calculate this creep impairmentWherein t' is to the time of consecutive points from this Every,For the creep impairment that under this stress, this persistent period causes

The damage of whole load block is

D_cIt it is the total creep damage caused under a load block effect；

Step 7): fatigue damage D that step 4) is obtained_fThe creep impairment D obtained with step 6)_cPhase Add, obtain this load block apply once cause always damage D；

D=D_c+D_f

D is the total creep-fatigue damage of hot conditions next one multiaxial loading spectrum block effect；

Step 8): estimation creep-fatigue life-span；

N=1/D

N is the creep-fatigue life-span, i.e. until material damage can experience under this load block repeat function Block number.

The determination of creep stress in described step 5), uses the half of consecutive points equivalent stress average, i.e.

$\mathrm{\&sigma;}=\frac{{\mathrm{\&sigma;}}_{\mathrm{eq}}{|}_{n=n0}+{\mathrm{\&sigma;}}_{\mathrm{eq}}{|}_{n=n0+1}}{4}$

In described step 6), the time interval using adjacent two data points calculates the time as creep impairment, cumulative In whole load history data block, each point creep impairment calculates the creep impairment that whole load block is caused

${\stackrel{\&CenterDot;}{D}}_c=t\text{'}/t$

$D_c=\mathrm{\&Sigma;}{\stackrel{\&CenterDot;}{D}}_c$

For moment point creep impairments all in load history block.

Compared with prior art, the present invention has the advantages that.

The present invention proposes low all creep-fatigue lifetime estimation methods under a kind of high temperature multiaxis spectrum carries.The method The damage that tired and creep cause being calculated respectively, fatigue damage estimates that drawn materials constant is the material of room temperature Material constant, it is not necessary to be measured material under high temperature constant, high-temperature creep injury estimation code requirement is recommended Stress rupture equati$, above constant is convenient to be obtained from Materials Handbook, saves experimentation cost.By verification experimental verification, Use the method to carry out low week creep-fatigue life estimate acquirement under high temperature multiaxis spectrum carries and preferably predict effect Really.

Accompanying drawing explanation

Fig. 1 is low all creep-fatigue lifetime estimation method flow charts under high temperature multiaxis spectrum carries.

Detailed description of the invention

In conjunction with accompanying drawing and the detailed description of the invention of the calculating example explanation present invention.

Present invention damage to be performed estimation includes that Multiaxial Fatigue Damage estimation and creep impairment are estimated, depends on According to damage measurement result, N is that the block that part can stand carries the load history number of times described, and is prediction Fatigue life.

Step 1): read load block internal stress strain history, utilize Mises criterion to obtain the equivalence of each point Strain stress_eq, loading spectrum is disconnected at maximum equivalent strain, and moves to load history data before this point carry Lotus course is last, completes load and arranges；

Assume load fast course such as following table:

Form 1 load history data

The equivalent strain of each point can be obtained according to load history, and strain is carried out course arrange, Former 15 is maximum point, only arranges strain in the strain history after can being arranged such as following table 2(table): Strain history after form 2 arrangement

ε in table_eqFor ${\mathrm{\&epsiv;}}_{\mathrm{eq}}=\frac{\sqrt{2}}{3}\sqrt{{({\mathrm{\&epsiv;}}_x-{\mathrm{\&epsiv;}}_y)}^2+{({\mathrm{\&epsiv;}}_y-{\mathrm{\&epsiv;}}_z)}^2+{({\mathrm{\&epsiv;}}_z-{\mathrm{\&epsiv;}}_x)}^2+\frac{3}{2}({\mathrm{\&gamma;}}_{\mathrm{xy}}^2+{\mathrm{\&gamma;}}_{\mathrm{yz}}^2+{\mathrm{\&gamma;}}_{\mathrm{zx}}^2)}$

Step 2): strain multiaxis method of counting according to relative equivalent, load history is counted, counts out In load history all repeatedly；

Strain multiaxis method of counting according to relative equivalent, this loading spectrum block can be taken out 1-12 point and 12-20 Point two is repeatedly；

Step 3): use unified Multiaxial Fatigue Damage model, calculates each fatigue damage repeatedly caused；

Unified Multiaxial Fatigue Life Prediction model:

$\frac{{\mathrm{\&Delta;\&epsiv;}}_{\mathrm{eq}}^{\mathrm{cr}}}{2}={[{\mathrm{\&epsiv;}}_n^{*2}+\frac{1}{3}{({\mathrm{\&Delta;\&gamma;}}_{\max }/2)}^2]}^{1/2}$

$\frac{{\mathrm{\&Delta;\&epsiv;}}_{\mathrm{eq}}^{\mathrm{cr}}}{2}=\frac{{\mathrm{\&sigma;}\text{'}}_f}{E}{\left({2N}_f\right)}^b+{\mathrm{\&epsiv;}\text{'}}_f{\left({2N}_f\right)}^c$

Obtain damage ${\stackrel{\&CenterDot;}{D}}_f=1/N_f$

Assume tired material constant such as table 3:

The tired material constant of form 3

E(MPa)	σf(MPa)	εf	b	c
					205000	1114	0.259	-0.097	-0.515

Use unified Multiaxial Fatigue Life Prediction model to calculate fatigue damage, two repeatedly fatigue damage divide It is not 0.00020971,0.00010127

Step 4): linear superposition is each causes fatigue damage repeatedly, obtains total fatigue damage Df；

$D_f=\mathrm{\&Sigma;}{\stackrel{\&CenterDot;}{D}}_f$

Df=0.00020971+0.00010127=0.00031098

Step 5): utilize former load history data and each point equivalent stress obtained is adjacent with it with this point The half of some average equivalent stress is as creep stress σ；

${\mathrm{\&sigma;}}_{\mathrm{eq}}=\frac{1}{\sqrt{2}}\sqrt{{(<{\mathrm{\&sigma;}}_x>-<{\mathrm{\&sigma;}}_y>)}^2+{(<{\mathrm{\&sigma;}}_y>-<{\mathrm{\&sigma;}}_z>)}^2+{(<{\mathrm{\&sigma;}}_z>-<{\mathrm{\&sigma;}}_x>)}^2+6({\mathrm{\&tau;}}_{\mathrm{xy}}^2+{\mathrm{\&tau;}}_{\mathrm{yz}}^2+{\mathrm{\&tau;}}_{\mathrm{zx}}^2)}$

$\mathrm{\&sigma;}=\frac{{\mathrm{\&sigma;}}_{\mathrm{eq}}{|}_{n=n0}+{\mathrm{\&sigma;}}_{\mathrm{eq}}{|}_{n=n0+1}}{4}$

Wherein<>is MacCauley symbol, represents when in bracket, number, more than or equal to zero, takes former numerical value, little 0 is taken in zero；σ_x,σ_y,σ_zFor x, the direct stress in y, z direction；τ_xy,τ_yz,τ_zxBeing respectively xy, yz, zx are flat Shear stress on face, data above obtains in load history block；σ_eqFor equivalent stress；

Its result of calculation see table 5, σ_eq, in σ two arranges；

Step 6): be this creep time t' with the time interval of adjacent two data points, according to creep rupture The creep impairment of all each points of Equation for Calculating, and cumulative seek creep impairment Dc；

Stress rupture equati$ lgt=b₁+b₂T+b₃x/T+b₄x²/T+b₅x³/T

Wherein t is the persistent period that material can stand under this stress effect of this temperature, intermediate variable T Computational methods be T=(9 θ/5+32)+460, intermediate variable x=lg σ, σ are the creep that step 5) is obtained Stress, b1, b2, b3, b4, b5 are material constant, obtain from Materials Handbook, and θ is temperature, and example is 700℃；

Thus can calculate this creep impairmentWherein t' is to the time of consecutive points from this Every,For the creep impairment that under this stress, this persistent period causes

The damage of whole load block is

D_cIt it is the total creep damage caused under a load block effect；

Under assuming that creep material constant enters:

Form 4 stress rupture equati$ parameter

b1	b2	b3	b4	b5
					-25.3186	-113623	285893.1	-151989	25370.15

Result of calculation such as table 5 below arranges

Form 5 creep impairment computational chart

Step 7): fatigue damage Df obtained and creep impairment Dc are added, obtains this load block and applies That once causes always damages D

D=D_c+D_f

D=0.0004596+0.0002744134=0.0007340134

Step 8): estimation creep-fatigue life-span N is the creep-fatigue life-span

N=1/D

N=1/0.0007340134=1362.4(block)

Through above 8 steps, creep-fatigue damage D in this load history block can be estimated, it was predicted that its Life-span N is 1362.4 loading spectrum blocks.

Claims (1)

1. low all creep-fatigue lifetime estimation methods under a high temperature multiaxis spectrum load, it is characterised in that: step As follows:

Step 1): read multiaxis spectrum and carry data block internal stress strain history data, utilize Mises criterion to ask Go out equivalent strain ε of each point_eq, loading spectrum is disconnected at maximum equivalent strain, and load before this point is gone through Number of passes is last according to moving to load history, obtains new load history；

Mises equivalent strain is

Wherein ε_x,ε_y,ε_zIt is respectively x, y, z direction normal strain, γ_xy,γ_yz,γ_zxIt is respectively xy, yz, zx flat Shearing strain on face, ε_x,ε_y,ε_zAnd γ_xy,γ_yz,γ_zxCarry in data block from multiaxis spectrum and read, ε_eqFor Mises equivalence Strain；

Step 2): utilize relative strain multiaxis method of counting, load history is counted, counts out load In course all repeatedly；

Step 3): according to unified Multiaxial Fatigue Life Prediction model, repeatedly calculate what it caused to each Fatigue damage；

Unified Multiaxial Fatigue Life Prediction model is:

$\frac{{\mathrm{\&Delta;\&epsiv;}}_{eq}^{cr}}{2}={\&lsqb;{\mathrm{\&epsiv;}}_n^{*2}+\frac{1}{3}{({\mathrm{\&Delta;\&gamma;}}_{max}/2)}^2\&rsqb;}^{1/2}$

$\frac{{\mathrm{\&Delta;\&epsiv;}}_{eq}^{cr}}{2}=\frac{{{\mathrm{\&sigma;}}^{\&prime;}}_f}{E}{\left(2N_f\right)}^b+{{\mathrm{\&epsiv;}}^{\&prime;}}_f{\left(2N_f\right)}^c$

Obtain damage

Wherein Δ γ_maxFor this repeatedly in maximum shear strain scope on maximum shear strain range plane,For Δγ_maxInstitute on the whole this repeatedly in normal strain amplitude,For the equivalent strain width under multiaxial loading,Draw according to course data, σ '_fFor fatigue strength coefficient, E is elastic modelling quantity, and b is tired Labor intensity index, ε '_fFor tired plastic coefficient, c is tired plasticity index, σ '_f、E、b、c、ε'_fFor material Material underlying parameter, it is possible to obtain from Materials Handbook, N_fThe life-span of this course repeatedly is experienced for material,For Material experiences this damage repeatedly caused；

Step 4): cumulative each repeatedly cause fatigue damage, obtain total fatigue damage D_f；

$D_f=\mathrm{\&Sigma;}{\stackrel{\&CenterDot;}{D}}_f$

Wherein D_fDamage material caused for one loading spectrum block of experience,Repeatedly material is made for each The damage become；

Step 5): calculating creep stress σ of micro-of each time_cjBy utilizing stress data in former loading spectrum Determine；

Determine calculating creep stress, calculating creep stress σ of loading spectrum n-th micro-time period_cj|_nUse following formula Determine:

${\mathrm{\&sigma;}}_{cj}{|}_n=\frac{{\mathrm{\&sigma;}}_{ceq}{|}_{n=n0}+{\mathrm{\&sigma;}}_{ceq}{|}_{n=n0+1}}{4}$

Wherein n0 is the starting point numbering of micro-section of loading spectrum n-th, and n0+1 is micro-section of loading spectrum n-th Terminal is numbered；

Equivalence creep stress calculates and uses:

${\mathrm{\&sigma;}}_{ceq}=\frac{1}{\sqrt{2}}\sqrt{{(<{\mathrm{\&sigma;}}_x>-<{\mathrm{\&sigma;}}_y>)}^2+{(<{\mathrm{\&sigma;}}_y>-<{\mathrm{\&sigma;}}_z>)}^2+{(<{\mathrm{\&sigma;}}_z>-<{\mathrm{\&sigma;}}_x>)}^2+6({\mathrm{\&tau;}}_{xy}^2+{\mathrm{\&tau;}}_{yz}^2+{\mathrm{\&tau;}}_{zx}^2)}$

Wherein<>is MacCauley symbol, represents when in bracket, number, more than or equal to zero, takes former numerical value, little 0 is taken in zero；σ_x,σ_y,σ_zIt is respectively x, the direct stress in y, z direction；τ_xy,τ_yz,τ_zxIt is respectively xy, yz, zx Shear stress in plane, σ_x,σ_y,σ_z,τ_xy,τ_yz,τ_zxObtain in load history block；

Step 6): with micro-of the time of adjacent two data points for this creep time t', according to creep rupture The creep impairment of all each points of Equation for Calculating, and cumulative obtain creep impairment Dc；

Stress rupture equati$ lgt=b₁+b₂T+b₃x/T+b₄x²/T+b₅x³/T

Wherein t is the persistent period that material can stand under this stress effect of this temperature, intermediate variable T Computational methods be T=(9 θ/5+32)+460, intermediate variable x=lg σ_cj, σ_cjFor step 5) meter that determines Calculating creep stress, b1, b2, b3, b4, b5 are material constant, obtain from Materials Handbook, and θ is temperature,

It is possible to calculate this time creep impairment of micro-sectionWherein t' is to consecutive points from this point Time interval,For the creep impairment that under this calculating creep stress, this persistent period causes；

The damage of whole load block is

D_cIt it is the total creep damage caused under a load block effect；

Step 7): by step 4) fatigue damage D that obtains_fWith step 6) the creep impairment D that obtains_cPhase Add, obtain this load block apply once cause always damage D；

D=D_c+D_f

D is the total creep-fatigue damage of hot conditions next one multiaxial loading spectrum block effect；

Step 8): the estimation creep-fatigue life-span；

N=1/D

N is the creep-fatigue life-span, i.e. until material damage can experience under this load block repeat function Block number.