CN105930553A - Method for predicting tensile strength of nickel-base superalloy gap - Google Patents

Abstract

The invention discloses a method for predicting tensile strength of nickel-base superalloy gap. The method includes the following steps: acquiring an attribute parameter of a material to be tested through an experiment; performing secondary development on finite element software, and implanting an Hosford yield criterion and a required material hardening constitutive model into the finite element software; defining the material attribute in the finite element software; performing 3-dimensional finite element partition on a gap test model in the finite element software; applying constraint and displacement load on the finite element model; setting a solver; performing solution to acquire a finite element calculation result; extracting the reaction force of each node of an end surface of the finite element model and accumulating the reaction forces in a time postprocessor so as to acquire a load value of each time step; multiplying a Time value by an applied total displacement value to acquire a displacement value of each time step; and turning the result into a load-displacement curve. The method adopts the yield criterion and a failure criterion suitable for nickel-base superalloy, and then the ultimate strength of a gap can be accurately predicted.

Description

Nickel base superalloy notch tensile strength Forecasting Methodology

Technical field

The invention belongs to method of testing materials technical field, be specifically related to a kind of based on Tresca yield criterion And the nickel base superalloy notch tensile strength Forecasting Methodology of plastic instability failure criteria.

Background technology

Nickel base superalloy is a kind of to have higher intensity with nickel as matrix, in the range of 650～1000 DEG C With good antioxidation, the high temperature alloy of resistance to combustion gas corrosion ability.Its preferable structure stability is with common The A that lattice are orderly₃Type B intermetallic compound, as hardening constituent, makes alloy effectively be strengthened, thus nickel Based high-temperature alloy is widely used in aero-engine, the tightest in particular as working environment Severe turbine disk material.

In the high-revolving work process of aero-engine wheel disc, the strength character of material is required more severe Carve, it is desirable to the biggest centrifugal load can be born under high speed conditions, prevent it under excessive rotating speed Exceed strength degree and destroy.It is several why not that breach feature can simulate typical case present in actual wheel disc Continuous structure feature.Therefore, the ultimate strength of the research breach feature prediction to disc burst speed Have great significance.

Although Chinese scholars early has research for alloy material notch tensile strength Forecasting Methodology, but for Predicting the outcome of nickel-bass alloy material is unsatisfactory with the identical situation of actual tests result.The present invention carries Go out a kind of notch tensile strength prediction side based on Tresca yield criterion and plastic instability failure criteria Method, thus prediction nickel base superalloy notch tensile strength exactly.

Summary of the invention

For making up existing Forecasting Methodology deficiency in terms of nickel base superalloy notch tensile strength prediction, It is an object of the invention to provide a kind of nickel base superalloy notch tensile strength Forecasting Methodology, to improve nickel The accuracy that based high-temperature alloy intensity judges..

For achieving the above object, the present invention is by the following technical solutions:

A kind of nickel base superalloy notch tensile strength Forecasting Methodology, comprises the following steps:

(1) obtained the property parameters of detected materials by test, this property parameters is engineering stress strain curve；

(2) finite element software is carried out secondary development, implant Hosford yield criterion and required material is hard Change constitutive model σ_T=σ₀+r(ε_p), wherein, σ₀Represent initial yield stress, r (ε_p) expression should by plasticity Become the hardening item expressed；

(3) at material properties defined in finite element software；

(4) notched test model is carried out 3-dimensional finite element division in finite element software, obtain finite element mould Type；

(5) FEM (finite element) model is applied constraint and displacement load；

(6) solver is set；

(7) solve, it is thus achieved that result of finite element；

(8) in time preprocessor, extract the support reaction of each node of end face of FEM (finite element) model, and add up, Obtain the load value of a time step；Time value is multiplied by the total displacement value of applying, it is thus achieved that the position of each time step Shifting value；

(9) the above results being made load-displacement curves, the maximum on curve is this notched specimen Ultimate strength.

In described step (1), first carry out Specimens tension test, it is thus achieved that the engineering stress of material- Strain curve (σ_E-ε_E), choose the curve before peak, by following transformation for mula be converted into trus stress- Strain curve (σ_T-ε_T)；

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_T=ln({\mathrm{\ϵ}}_E+1)\\ {\mathrm{\σ}}_T={\mathrm{\σ}}_E\·({\mathrm{\ϵ}}_E+1)\end{array}\right.$

In above formula, σ_ERepresent engineering stress, ε_ERepresent engineering strain, σ_TRepresent trus stress, ε_TVery should represent Become；

True stress-true strain curve is converted to trus stress-plastic strain curve (σ by following transformation for mula_T-ε_p)；

${\mathrm{\ϵ}}_p={\mathrm{\ϵ}}_T-\frac{{\mathrm{\σ}}_T}{E}$

In above formula, ε_pRepresenting plastic strain, E represents elastic modelling quantity, and this elastic modelling quantity is oblique by the stretch section tested Rate and obtain；

Hardened material constitutive model σ is obtained by trus stress-plastic strain curve matching_T=σ₀+r(ε_p), in formula σ₀Represent initial yield stress, r (ε_p) the hardening item expressed with plastic strain of expression；Matched curve σ_T=σ₀+r(ε_p) requiring peak, i.e. last point meetsI.e. peak slope is equal to vertical Coordinate figure.

In described step (2), owing to existing finite element analysis software provides only Mises yield criterion one Yield criterion, the committed step needed for the present invention is exactly the implantation of Tresca yield criterion；

The step that finite element software carries out secondary development is: the Hosford of secondary development write subprogram Yield criterion, its complete formula is

$f\left(\mathrm{\σ}\right)={\[\frac{{({\mathrm{\σ}}_1-{\mathrm{\σ}}_2)}^n+{({\mathrm{\σ}}_2-{\mathrm{\σ}}_3)}^n+{({\mathrm{\σ}}_3-{\mathrm{\σ}}_1)}^n}{2}\]}^{1/n}-{\mathrm{\σ}}_y=0$

In formula, f (σ) represents yield function, σ₁、σ₂And σ₃Represent first principal stress, second principal stress respectively And third principal stress, σ_eqFor equivalent stress, n represents coefficient；As coefficient n=1, Hosford surrenders Criterion will deteriorate to Tresca yield criterion, i.e. achieve the implantation of Tresca yield criterion.

In described step (2), the hardened material constitutive model σ that step (1) matching is obtained_T=σ₀+r(ε_p) Write in limited metasubprogram.

In described step (3), the material properties of definition is to be adopted by the property parameters obtained in step (1) It is input in finite element program by command stream or GUI mode.

In described step (4), the breach near zone grid of FEM (finite element) model is done local micronization processes.

In described step (5), the displacement of applying is more than deflection during structural failure.

In described step (6), the step that solver is arranged is: select large deformation static(al) steady-state analysis, Time when specifying load EOS is 1, closes and automatically determines load step option.

The invention has the beneficial effects as follows: the present invention simulates load-deformation curve ascent stage of first drawing materials High point meets the constitutive relation of instability condition, as much as possible ensure that the accuracy of material properties；Again Utilize finite element software, use Tresca yield criterion to replace traditional Mises yield criterion to breach Part is modeled calculating, and has selected the yield criterion for the nickel base superalloy most suitability；Extract The maximum load value of result of calculation is the hot strength of Notched specimen.Present invention employs and be more suitable for nickel The yield criterion of based high-temperature alloy and failure criteria, therefore can dope the intensity of Notched specimen more accurately The limit.

Accompanying drawing explanation

Fig. 1 is notch strength tensile test piece figure；

Fig. 2 is notch strength tensile test piece pictorial diagram；

Fig. 3 is smooth specimen tensile test piece drawing and pictorial diagram；

Fig. 4 is smooth specimen tensile test piece pictorial diagram；

Fig. 5 is smooth specimen engineering stress-strain curve that test obtains；

Fig. 6 is the stretching engineering stress-strain curve under GH4169 room temperature and true stress-true strain curve；

Fig. 7 is gap test piece model 3-dimensional FEM meshing schematic diagram；

Fig. 8 is the finite element predictions figure that the present invention obtains.

Detailed description of the invention

Below in conjunction with the accompanying drawings the present invention is further described.

A kind of nickel base superalloy notch tensile strength Forecasting Methodology of the present invention, comprises the following steps:

(1) obtained the property parameters of detected materials by test, this property parameters is engineering stress strain curve；

First Specimens tension test is carried out, it is thus achieved that the engineering stress of material-strain curve (σ_E-ε_E), Choose the curve before peak, following transformation for mula be converted into true stress-true strain curve (σ_T-ε_T)；

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_T=ln({\mathrm{\ϵ}}_E+1)\\ {\mathrm{\σ}}_T={\mathrm{\σ}}_E\·({\mathrm{\ϵ}}_E+1)\end{array}\right.$

In above formula, σ_ERepresent engineering stress, ε_ERepresent engineering strain, σ_TRepresent trus stress, ε_TVery should represent Become；

True stress-true strain curve is converted to trus stress-plastic strain curve (σ by following transformation for mula_T-ε_p)；

${\mathrm{\ϵ}}_p={\mathrm{\ϵ}}_T-\frac{{\mathrm{\σ}}_T}{E}$

In above formula, ε_pRepresenting plastic strain, E represents elastic modelling quantity, and this elastic modelling quantity is oblique by the stretch section tested Rate and obtain；

Hardened material constitutive model σ is obtained by trus stress-plastic strain curve matching_T=σ₀+r(ε_p), in formula σ₀Represent initial yield stress, r (ε_p) the hardening item expressed with plastic strain of expression；Matched curve σ_T=σ₀+r(ε_p) requiring peak, i.e. last point meetsI.e. peak slope is equal to vertical Coordinate figure.

(2) finite element software is carried out secondary development, implant Hosford yield criterion and required material is hard Change constitutive model σ_T=σ₀+r(ε_p)；

Owing to existing finite element analysis software provides only Mises yield criterion one yield criterion, the present invention Required committed step is exactly the implantation of Tresca yield criterion.

The step that finite element software carries out secondary development is: the Hosford of secondary development write subprogram Yield criterion, its complete formula is

$f\left(\mathrm{\σ}\right)={\[\frac{{({\mathrm{\σ}}_1-{\mathrm{\σ}}_2)}^n+{({\mathrm{\σ}}_2-{\mathrm{\σ}}_3)}^n+{({\mathrm{\σ}}_3-{\mathrm{\σ}}_1)}^n}{2}\]}^{1/n}-{\mathrm{\σ}}_y=0$

In formula, f (σ) represents yield function, σ₁、σ₂And σ₃Represent first principal stress, second principal stress respectively And third principal stress, σ_eqFor equivalent stress, n represents coefficient；As coefficient n=1, Hosford surrenders Criterion will deteriorate to Tresca yield criterion, i.e. achieve the implantation of Tresca yield criterion.

The hardened material constitutive model σ that step (1) matching is obtained_T=σ₀+r(ε_p) the write sub-journey of finite element In sequence.

(3) at material properties defined in finite element software；Will adopt by the middle property parameters obtained of step (1) It is input in finite element program by command stream or GUI mode.

(4) notched test model is carried out 3-dimensional finite element division in finite element software, obtain finite element mould Type；And breach near zone grid is done local micronization processes.

(5) FEM (finite element) model is applied constraint and displacement load；When the displacement load applied is more than structural failure Deflection.

(6) solver is set: select large deformation static(al) steady-state analysis, it is intended that time during load EOS is 1, close and automatically determine load step option.

(7) solve, it is thus achieved that result of finite element；

(8) in time preprocessor, extract the support reaction of each node of end face of FEM (finite element) model, and add up, Obtain the load value of a time step；Time value is multiplied by the total displacement value of applying, it is thus achieved that the position of each time step Shifting value；

(9) the above results being made load-displacement curves, the maximum on curve is this notched specimen Ultimate strength.

Embodiment:

The present invention is as a example by nickel base superalloy GH4169 DEN plane plate specimen, to thickness under room temperature For 0.75mm, root radius is that the notch tensile strength of the notched specimen of 3mm is predicted.Sample Drawing and picture in kind as it is shown in figure 1, in figure a size of: h1=100mm, h2=35mm, h3=3mm, Φ=12mm, R1=10mm, R2=0.75mm, R3=3mm.

(1) for obtaining the engineering stress strain curve of material properties accurately, i.e. material, need to first enter Row Specimens tension test, sample drawing and photo are as shown in Figure 2.

During actual tension test, the deformation of notched specimen is concentrated mainly on root of notch region, leads Cause the apparent strain rate that the actual tensile strain rate of breach regional area material can load much larger than test, 3～10 times can be reached.Additionally, under the conditions of identical name loads strain rate, different notch size examinations The strain rate of the gap regions of sample the most difference.Therefore, according to the practical situation of notch tensile, examine Considering the rate correlation properties to test material, smooth pole uses three kinds of different strain rate loading condition to enter Row test, uses extensometer carry out controlled loading strain rate and obtain extensometer gage length section in process of the test Material basic deformation curve.This test is applied with three kinds of different size of strain rates, is respectively 0.0001S^-1, 0.0005S^-1And 0.001S^-1, the loading speed being converted in extensometer gage length is respectively 0.15mm/min, 0.75mm/min and 1.5mm/min, average with obtain in the range of certain strain rate Engineering stress-strain curve, and then set up material constitutive model more accurately.Test obtains three altogether Plant the four groups of valid data loaded under strain rate, as it is shown on figure 3: h1 '=100mm. in figure a size of H2 '=28.39mm, h3 '=30mm, Φ 1=10 ± 0.02mm, Φ 2=5 ± 0.02mm, R=10mm, Ra=0.8；Sample complete rupture, in gauge length section, is considered as valid data.

Four groups of data are averaged, as setting up the master data of material elasto-plastic Constitutive Model, i.e. material Engineering stress-strain curve (the σ of material_E-ε_E).Choose the curve before peak, by following transformation for mula It is converted into true stress-true strain curve (σ_T-ε_T),

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_T=ln({\mathrm{\ϵ}}_E+1)\\ {\mathrm{\σ}}_T={\mathrm{\σ}}_E\·({\mathrm{\ϵ}}_E+1)\end{array}\right.$

In above formula, σ_ERepresent engineering stress, ε_ERepresent engineering strain, σ_TRepresent trus stress, ε_TRepresent True strain.

Above-mentioned steps obtain GH4169 room temperature under stretching engineering stress-strain curve and trus stress-should Varied curve is as shown in Figure 4.

Further true stress-true strain curve is converted to trus stress-plastic strain just like down conversion formula bent Line (σ_T-ε_p),

${\mathrm{\ϵ}}_p={\mathrm{\ϵ}}_T-\frac{{\mathrm{\σ}}_T}{E}$

In above formula, ε_pRepresenting plastic strain, E represents elastic modelling quantity, and this elastic modelling quantity can be by the bullet tested Property slope over 10 and obtain.

Hardened material constitutive model σ is obtained by trus stress-plastic strain curve matching_T=σ₀+r(ε_p), in formula σ₀Represent initial yield stress, r (ε_p) the hardening item expressed with plastic strain of expression.Matched curve σ_T=σ₀+r(ε_p) requiring peak, i.e. last point meetsI.e. peak slope is equal to vertical Coordinate figure (meets large deformation instability condition).

Here use following non-linear isotropic hardening model rule to describe its simple tension trus stress- The plastic period of strain curve:

${\mathrm{\σ}}_T={\mathrm{\σ}}_0+r_0{\mathrm{\ϵ}}_p+r_1(1-e^{-b_1{\mathrm{\ϵ}}_p})+r_2(1-e^{-b_2{\mathrm{\ϵ}}_p})+r_3(1-e^{-b_3{\mathrm{\ϵ}}_p})$

In formula, σ₀For initial yield stress, Section 2 is linear hardening item, Section 3, Section 4 and Five is nonlinear hardening item, r₀、r₁、r₂、r₃、b₁、b₂And b₃For isotropic hardening parameter. Matching obtains material parameter undetermined therein, and fitting result is shown in Table 1.Wherein b₁、b₂With and b₃It is immeasurable Guiding principle parameter, elastic modulus E, initial yield stress σ_y0、r₀、r₁、r₂、r₃Unit be MPa.

Table 1GH4169 elasto-plastic Constitutive Model material parameter fitting result

(2) this example uses ANSYS to carry out finite element method (fem) analysis, first with UPFs at ANSYS Defined in the material properties model that uses in Hosford yield criterion and step (1)

(3) use command stream or GUI mode defeated the material properties parameter that test in step (1) obtains Enter in Ansys.

(4) notched test model is carried out 3-dimensional finite element and divides mesh refinement near breach, such as Fig. 5 Shown in, this example uses Solid 185 unit.

(5) according to actual loaded situation, all nodes on FEM (finite element) model lower surface are applied all directions On fixed constraint, all nodes on upper surface are applied the displacement of 1.5 on draw direction.

(6) Ansys solver is set, selects large deformation static(al) steady-state analysis, it is intended that load EOS Time time be 1, close automatically determine load step option, arranging load step number is 1000 steps, every 10 Step record one secondary data.

(7) solve, it is thus achieved that result of finite element.

(8) entry time preprocessor, extracts the support reaction of each node in upper surface, accumulates it, obtain Obtain the load value of a time step；Time value is multiplied by the total displacement value of applying, it is thus achieved that the displacement of each time step Value.

(9) result obtained in step (8) is made load-displacement curves, such as Fig. 6, on curve Maximum 29.22KN is the ultimate strength of this notched specimen.

By this Forecasting Methodology result of calculation and traditional prediction method (Mises yield criterion) and experimental result Together to such as table 2, can be seen that the present invention is effectively improved nickel base superalloy and lacks from error contrast Mouth hot strength precision of prediction.

Table 2 Comparative result

Although the present invention is open as above with preferred embodiment, but they are not for limiting the present invention , any it is familiar with this those skilled in the art, without departing from the spirit and scope of the invention, from various when doing Change or retouching, therefore protection scope of the present invention should be defined with the scope of patent protection of the application Be as the criterion.The most detailed description of the present invention be routine techniques content.

Claims (8)

1. a nickel base superalloy notch tensile strength Forecasting Methodology, it is characterised in that: comprise the following steps:

(1) obtained the property parameters of detected materials by test, this property parameters is engineering stress strain curve；

(2) finite element software is carried out secondary development, implant Hosford yield criterion and required material is hard Change constitutive model σ_T=σ₀+r(ε_p), wherein, σ₀Represent initial yield stress, r (ε_p) expression should by plasticity Become the hardening item expressed；

(3) at material properties defined in finite element software；

(4) notched test model is carried out 3-dimensional finite element division in finite element software, obtain finite element mould Type；

(5) FEM (finite element) model is applied constraint and displacement load；

(6) solver is set；

(7) solve, it is thus achieved that result of finite element；

(8) in time preprocessor, extract the support reaction of each node of end face of FEM (finite element) model, and add up, Obtain the load value of a time step；Time value is multiplied by the total displacement value of applying, it is thus achieved that the position of each time step Shifting value；

(9) the above results being made load-displacement curves, the maximum on curve is this notched specimen Ultimate strength.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 1, its feature exists In: in described step (1), first carry out Specimens tension test, it is thus achieved that the engineering stress of material -strain curve (σ_E-ε_E), choose the curve before peak, following transformation for mula be converted into trus stress -strain curve (σ_T-ε_T)；

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_T=ln({\mathrm{\ϵ}}_E+1)\\ {\mathrm{\σ}}_T={\mathrm{\σ}}_E\·({\mathrm{\ϵ}}_E+1)\end{array}\right.$

In above formula, σ_ERepresent engineering stress, ε_ERepresent engineering strain, σ_TRepresent trus stress, ε_TVery should represent Become；

True stress-true strain curve is converted to trus stress-plastic strain curve (σ by following transformation for mula_T-ε_p)；

${\mathrm{\ϵ}}_p={\mathrm{\ϵ}}_T-\frac{{\mathrm{\σ}}_T}{E}$

In above formula, ε_pRepresenting plastic strain, E represents elastic modelling quantity, and this elastic modelling quantity is oblique by the stretch section tested Rate and obtain；

Hardened material constitutive model σ is obtained by trus stress-plastic strain curve matching_T=σ₀+r(ε_p), in formula σ₀Represent initial yield stress, r (ε_p) the hardening item expressed with plastic strain of expression；Matched curve σ_T=σ₀+r(ε_p) requiring peak, i.e. last point meetsI.e. peak slope is equal to vertical Coordinate figure.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 1, its feature exists In: in described step (2), the step that finite element software carries out secondary development is: secondary development is write Entering the Hosford yield criterion of subprogram, its complete formula is

$f\left(\mathrm{\σ}\right)={\[\frac{{({\mathrm{\σ}}_1-{\mathrm{\σ}}_2)}^n+{({\mathrm{\σ}}_2-{\mathrm{\σ}}_3)}^n+{({\mathrm{\σ}}_3-{\mathrm{\σ}}_1)}^n}{2}\]}^{1/n}-{\mathrm{\σ}}_y=0$

In formula, f (σ) represents yield function, σ₁、σ₂And σ₃Represent first principal stress, second principal stress respectively And third principal stress, σ_eqFor equivalent stress, n represents coefficient；As coefficient n=1, Hosford surrenders Criterion will deteriorate to Tresca yield criterion, i.e. achieve the implantation of Tresca yield criterion.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 3, its feature exists In: in described step (2), the hardened material constitutive model σ that step (1) matching is obtained_T=σ₀+r(ε_p) Write in limited metasubprogram.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 1, its feature exists In: in described step (3), the material properties of definition is the property parameters that will obtain in step (1) Command stream or GUI mode is used to be input in finite element program.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 1, its feature exists In: in described step (4), the breach near zone grid of FEM (finite element) model is done local micronization processes.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 1, its feature exists In: in described step (5), the displacement of applying is more than deflection during structural failure.

Nickel base superalloy notch tensile strength Forecasting Methodology the most according to claim 1, its feature exists In: in described step (6), the step that solver is arranged is: select large deformation static(al) steady-state analysis, Time when specifying load EOS is 1, closes and automatically determines load step option.