CN111639448B - Linear friction welding numerical simulation method introducing initial defects - Google Patents
Linear friction welding numerical simulation method introducing initial defects Download PDFInfo
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Abstract
The invention relates to a linear friction welding numerical simulation method introducing initial defects, belonging to the technical field of welding numerical simulation; based on the numerical simulation of the linear friction welding of the high-temperature alloy, firstly, a finite element geometric model is established, then material attribute parameters are set, ALE self-adaptive grid parameters and mass scaling parameters are selected, friction heat generation and film layer heat dissipation setting between contact surfaces are carried out, loads and boundaries are set, a predefined temperature field is applied, grid attributes are set, and finally, simulation calculation and post-processing analysis are carried out. The method fully considers the material characteristics, the geometric characteristics and the position characteristics of initial defects existing in high-temperature alloy raw materials in the linear friction welding process, quantitatively characterizes the linear friction welding joint forming, the joint temperature field, the velocity field and the stress strain field which introduce the initial defects by using a numerical simulation method, and reveals the mutation and evolution conditions of each physical field in a defect tip region.
Description
Technical Field
The invention belongs to the technical field of welding numerical simulation, relates to a linear friction welding numerical simulation method for high-temperature-resistant materials for aerospace, and particularly relates to a linear friction welding numerical simulation method for introducing initial defects.
Background
Linear Friction Welding (LFW): the special solid phase connection process and the advantages of precision, high efficiency, energy conservation, environmental protection and the like are used for the important application in the manufacture and maintenance of the integral blade disc of the engine; the high-temperature alloy is an irreplaceable key material for high-temperature parts such as turbine blades, guide blades, high-pressure compressor disks, combustors and the like of gas turbines for aviation, aerospace and industry; when the linear friction welding blisk is in service, extremely severe heat, mechanical load and environmental damage are borne, various failure modes such as high-cycle fatigue, low-cycle fatigue, creep, corrosion, oxidation and ablation and interaction of the failure modes are shown, and the initiation and the expansion of internal cracks of the material are realized completely, so that the joint is finally fractured; the initial defect of the high-temperature alloy material is a main crack initiation source in the service process of a linear friction welding joint and can interact with the defect generated in the service process; the forming quality and the interface oxidation behavior of the high-temperature alloy linear friction welding joint are related to the defects of the joint; the method for researching the linear friction welding of the high-temperature alloy containing the initial defects is an important basis for developing research on the influence of joint damage and is one of important contents for breakthrough of the technical bottleneck of the high-temperature alloy linear friction welding blisk.
The linear friction welding process is as shown in fig. 1, in which the workpieces to be welded are respectively fixed on a fixture, a mechanism drives one of the workpieces to reciprocate linearly, and the other workpiece is clamped and moves linearly along the pressure direction. In the welding process, the friction shearing force and the axial pressure act together, friction heat is generated on a contact surface of the two workpieces, the plastic metal of the interface forms flash after being extruded along with friction movement, and oxide inclusions on the surface are extruded at the same time. When a certain amount of metal is extruded from the friction interface, the friction interface enters a return centering stage, the relative shearing motion between the workpieces is rapidly stopped, and upsetting pressure acts on the two ends of the sample to realize connection. The experimental study of the linear friction welding process of the high-temperature alloy lacks real-time monitoring on the temperature field and the stress strain in the welding process, and the numerical simulation can be used as an important means for studying the linear friction welding process and can carry out visual quantitative analysis on all physical quantities and the evolution rule thereof in the welding process. The method for simulating the linear friction welding numerical value of the nickel-based superalloy is analyzed from the current research situation at home and abroad, the method for simulating the linear friction welding numerical value of the nickel-based superalloy is gradually mature, the transition is gradually carried out from a 2D model to a 3D model, and a nickel-based superalloy thermo-mechanical coupling model (Guiliang Qin, Peihao Geng, Jun Zhou, Zengda Zou, Modeling of thermal-mechanical coupling in linear welding knowledge of Ni-based super alloy, Materials & Design, Volume 172,2019,107766, ISSN 0264-; numerical simulation of evolution of linear friction welding micro-hole defects of Sunpu of Harbin Industrial university and closure law (Sunpu. numerical simulation of evolution of linear friction welding micro-hole defects and closure law research [ D ]. Harbin Industrial university, 2014.) in the text, DEFORM software is used for carrying out linear friction welding numerical simulation on titanium alloy on different process parameters such as temperature, pressure, vibration frequency, amplitude, upsetting pressure and the like respectively, observing size change of the micro-hole defects, summarizing the closure law and guiding welding forming of the titanium alloy and improving welding quality. However, the linear friction welding technology of the high-temperature alloy has few reference technological parameters, the linear welding head has almost no metallurgical defects under excellent technological parameters, the research on the influence of the defects of the raw material of the high-temperature alloy on the linear friction welding technology is less concerned, and the metallurgical defects of the raw material of the high-temperature alloy have important influence on the flash forming, stress distribution, temperature distribution and shortening of the raw material of the high-temperature alloy in the linear friction welding process, so that the construction of the thermal-mechanical coupling force process of the linear friction welding introducing the initial defects and an engineering regulation and control numerical simulation platform have important significance.
Disclosure of Invention
The technical problem to be solved is as follows:
in order to avoid the defects of the prior art, the invention provides a linear friction welding numerical simulation method introducing initial defects, which is based on the linear friction welding numerical simulation of the high-temperature alloy, fully considers the influence rules of the material characteristics, the geometric characteristics, the positions and the dispersion degrees of the defects in the high-temperature alloy raw material and the like on multiple physical fields such as a stress strain field, a temperature field, a speed field and the like in the linear friction welding process, explores the evolution rule of the stress at the tip of the defects in the linear friction welding process and the closing and deformation conditions of the defects, and provides basis and reference for the research of the current high-temperature alloy linear friction welding process.
The technical scheme of the invention is as follows: a linear friction welding numerical simulation method for introducing initial defects is characterized by comprising the following specific steps:
step 1: establishing a finite element geometric model;
firstly, establishing a finite element geometric model of the high-temperature alloy defect-free linear friction welding by using an ABAQUS software Part module, wherein the geometric model comprises a 2D shell element deformation body workpiece and a 2D linear vibration rigid body workpiece, and has initial holes and inclusion defects; then dividing the deformation body workpiece into a welding seam area, a heat affected area and a base metal area, wherein the welding seam area is used as a welding free end, the heat affected area and the base metal area are used as welding clamping ends, and the defect position is arranged in the welding seam area;
step 2: setting material attribute parameters;
setting material Property parameters of the high-temperature alloy by adopting a Property module of ABAQUS software, creating a homogeneous section of a high-temperature alloy entity, and endowing the section Property of the geometric model of the 2D shell unit deformation body workpiece with the initial defect introduced in the step 1;
the material property parameters comprise A, B, n, C, m,
Tr、TmThe relationship between 5 parameters and the rheological stress σ during numerical simulation is as follows:
wherein A, B and n are yield strength, strain hardening coefficient and strain hardening index of the material when the material is subjected to quasi-static deformation at room temperature respectively; c is the strain rate strengthening coefficient; m is the coefficient of thermal softening;
the actual plastic deformation strain rate;
a preset plastic deformation reference rate; epsilon is equivalent plastic strain, T*＝(T-Tr)/(Tm-Tr) For temperature-related dimensions, TrFor reference temperature, TmIs the melting point temperature; (A + B. epsilon.)n)、
[1-(T*)m]Describing the work hardening effect, strain, respectively, of a materialRate effect and temperature softening effect;
and step 3: selecting ALE self-adaptive grid parameters and quality scaling parameters;
under an ABAQUS software Step module, endowing a section attribute to the geometric model based on the steps 1 and 2, and determining ALE self-adaptive grid parameters and quality scaling parameters;
and 4, step 4: friction heat generation between contact surfaces and film layer heat dissipation are carried out;
in the ABAQUS software Interaction module, friction heat generation between contact surfaces of a vibration rigid body workpiece and a deformation body workpiece is set, and the interface friction heat generation is calculated by an equation (5):
q＝[(1-δ)μPv]+(δητyv) (5)
wherein (1-delta) mu Pv is the dry friction heat production quantity, delta eta tauyv is the amount of sticking friction, δ state variable represents the sticking friction ratio, which has a value of 0-1, μ is the coefficient of friction, P is the friction pressure, v is the linear velocity of friction, η is the efficiency of conversion of mechanical energy to thermal energy, τyIs the material shear stress;
performing film layer heat dissipation setting on each part of the deformation body workpiece, and setting the convective heat transfer coefficient of the free end of the linear friction welding joint with the initial defect as 30W/(m)2DEG C.), the heat convection coefficient of the clamping end is set to 1000W/(m)2·℃)；
Then, simulating linear friction welding of the vibration rigid body workpiece and the deformation body workpiece;
and 5: setting load and boundary, and applying a predefined temperature field;
in an ABAQUS Load module, applying upsetting force to a 2D deformation body workpiece clamping end; defining a periodic amplitude curve of the linear vibration of the vibration rigid body, wherein the periodic amplitude curve is characterized by Fourier series equations (8) and (9):
t≥t0the method comprises the following steps: amplitude value
t＜t0The method comprises the following steps: amplitude a ═ A0(9)
Wherein N is the number of Fourier series terms; omega is the circumferential frequency; t is t0Is the starting time; a. the0Is the initial amplitude; a. thenIs a coefficient of cos term, n is 1,2,3, …; beta is anCoefficients that are cos terms;
applying a predefined temperature of 25 ℃ to the deformation body workpiece and the vibration rigid body workpiece;
step 6: setting grid attributes;
in a Mesh module in ABAQUS, dividing and setting the Mesh size of a 2D deformable body workpiece by adopting a mode of integral seed distribution and edge seed distribution; the grids are gradually thinned from the parent metal area to the welding line area, and the initial defect hole and the inclusion adjacent area need to be provided with finer grids;
and 7: analog calculation and post-processing analysis;
in a Job module of ABAQUS software, monitoring an analog calculation process in real time to ensure the convergence of the calculation process; and analyzing a plurality of physical fields of a temperature field, a stress strain field and a speed field of the linear friction welding finite element model introduced with the initial defects.
The further technical scheme of the invention is as follows: the defect types in the step 1 are circular holes and inclusions, and the number of the defects is 1 or 2.
The further technical scheme of the invention is as follows: in the Step 3, Frequency and Mesh Sweeps in the ALE self-adaptive grid parameters are set, wherein the Frequency control is to control the number of times of grid Remesh in the whole Step Time, and the Remesh number n is represented by a formula (2); the Mesh sweet control parameter is iteration times under a Frequency, when the value of the parameter is n, each remesh process carries out sweet for the Mesh for n times, each increment step carries out remesh once, the value of Frequency is set to be 1, and the value of the self-adaptive Mesh parameter is determined based on the above criteria;
n＝Incrementnumber/Frequency (2)
the selection principle of the mass scaling parameters is characterized by an estimation formula (3) showing the stability limit of the dynamic process;
wherein L iseIs the minimum characteristic unit length, cdIs the expansion wave velocity of the material; the expansion wave velocity of the material is characterized by equation (4);
where E is the Young's modulus and ρ is the material density.
The further technical scheme of the invention is as follows: and 3, setting the welding free end of the geometric model as an adaptive grid control area.
The further technical scheme of the invention is as follows: in the simulation process of the vibration rigid body workpiece and the deformation body workpiece in the step 4, the control equation of the deformation body workpiece heat transfer module is represented by a formula (6) and a formula (7);
wherein, cpConstant pressure heat capacity of the high-temperature alloy, and rho is the density of the high-temperature alloy; Δ Q is the amount of heat transferred into the body of the microelement per unit time.
The further technical scheme of the invention is as follows: when the upsetting force is applied to the clamping end of the 2D deformable body workpiece in the step 5, limiting the displacement of the clamping end in the X direction and the rotation of an X-Y plane; and limiting the displacement of the vibration rigid body workpiece in the Y direction and the rotation of the vibration rigid body workpiece in the X-Y direction.
The further technical scheme of the invention is as follows: the control attributes of the grids in the step 6 are a quadrilateral free-stepping algorithm and a quadrilateral-based free-stepping algorithm, the cell type selects an explicit CPE4RT four-node thermally coupled plane strain quadrilateral cell, bilinear displacement and temperature are adopted, and reduction integration and hourglass control are adopted; 1/10 where the grid size near the defect is the grid size of the weld area is selected.
Advantageous effects
The invention has the beneficial effects that: the method fully considers the material characteristics, the geometric characteristics and the position characteristics of initial defects existing in high-temperature alloy raw materials in the linear friction welding process, quantitatively characterizes the linear friction welding joint forming, the joint temperature field, the velocity field and the stress strain field which introduce the initial defects by using a numerical simulation method, and reveals the mutation and evolution conditions of each physical field in a defect tip region.
Examples 1-4 of the specific embodiment, the superalloy linear weld joint that introduced the initial flaw had reduced axial shortening, and the results indicated: shortening of double-hole defect joint (0.2099mm) < shortening of double-inclusion defect joint (0.3354mm) < shortening of single-hole defect joint (0.4221mm) < shortening of single-inclusion defect joint
(0.6587 mm); the initial defects are introduced to change the stress distribution of the high-temperature alloy linear welding head, and a large stress area is enlarged along with the increase of the number of the defects, and the tip stress of the double inclusion defects is more than the tip stress of the double hole defects is more than the tip stress of the single inclusion defects is more than the tip stress of the single hole defects. The introduction of initial defects reduces the shortening of the joint, has poor welding formability, leads welding materials not to be combined among atoms, increases a large stress area, and leads residual stress after welding to be difficult to eliminate, thereby causing the damage of the service process of the joint.
The invention provides a linear friction welding numerical simulation method introducing initial defects, which guides a high-temperature alloy linear friction welding process, reveals the interaction and defect evolution rule of the initial defects of raw materials in the linear friction welding process, and lays the foundation of crack initiation fracture in the service process of a linear friction welding joint; the research of the linear friction welding process of the high-temperature resistant material (containing the initial defect) is improved, the technical support is provided for the linear friction welding of the high-temperature resistant material, the high-temperature resistant material is better served for the high-end manufacturing fields of aerospace and the like, and the method has important significance.
Drawings
FIG. 1 is a schematic view of a linear friction welding process;
FIG. 2 is a finite element geometric model of a high temperature alloy linear friction welding method introducing single hole type initial defects according to embodiment 1 of the present invention;
FIG. 3 is a table of material property parameters for example 1 of the present invention;
FIG. 4 is a finite element geometric model of linear friction welding of a superalloy with a single inclusion type defect introduced in embodiment 2 of the present invention;
FIG. 5 is a finite element geometric model of linear friction welding of a superalloy with double-hole defects introduced in embodiment 3 of the present invention;
FIG. 6 is a finite element geometric model of linear friction welding of high temperature alloy with double inclusion defects introduced in embodiment 4 of the present invention;
FIG. 7 is a stress cloud and defect tip stress evolution curves for 4 embodiments of the present invention; (a) example 1 stress cloud plot; (b) example 2 stress cloud plot; (c) example 3 stress cloud plot; (d) example 4 stress cloud plot; (e) defect tip stress evolution.
Detailed Description
The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The invention relates to a thermal coupling numerical simulation method considering the introduction of initial defects in the process of simulating a linear friction welding finite element based on an ALE self-adaptive grid and a mass scaling technology, which comprises the following steps:
step 1: establishing a finite element geometric model:
establishing a finite element geometric model of the high-temperature alloy defect-free linear friction welding by adopting an ABAQUS software Part module, fully considering the material characteristics, the geometric characteristics and the position characteristics of defects of the high-temperature alloy in the linear friction welding process, setting a geometric model with initial holes and inclusion defects on the finite element geometric model of the defect-free linear friction welding by using the Part module, wherein the geometric model comprises a 2D shell unit deformation body workpiece and a 2D linear vibration rigid body workpiece, and dividing a welding seam area, a heat affected zone and a base metal area on the 2D deformation body workpiece; the defect positions are arranged in the welding seam area, the defect types are circular holes and inclusions, and the defect number is 1 and 2. In the geometric model, a welding seam area in the 2D deformation body workpiece is used as a welding free end, and a heat affected area and a base metal area are used as welding clamping ends.
Step 2: setting material attribute parameters:
and 2, on the basis of establishing the finite element geometric model of the high-temperature alloy linear friction welding with the initial defects in the step 1, setting material Property parameters of the high-temperature alloy by adopting a Property module of ABAQUS software, creating a solid homogeneous section of the high-temperature alloy, and giving the section properties of the geometric model of the 2D deformation body with the initial defects introduced in the step 1. The material property parameters of the high-temperature alloy can be truly characterized by Young modulus, Poisson's ratio, density, thermal conductivity coefficient, specific heat capacity, thermal expansion coefficient and a Johnson-Cook constitutive model taking true stress-true strain data as a calibration basis. The Johnson-Cook constitutive model can accurately describe the work hardening effect, the high-temperature softening effect and the strain rate hardening effect of the metal material, and constitutive parameters A, B, n, C, m and B in the constitutive model are determined by fitting a true stress-strain curve obtained by a high-temperature alloy thermal compression deformation test,
Tr, Tm, the 5 parameters and the rheological stress sigma in the numerical simulation process satisfy the formula (1).
Wherein A, B and n are yield strength, strain hardening coefficient and strain hardening index of the material when the material is subjected to quasi-static deformation at room temperature respectively; c is the strain rate strengthening coefficient; m is the coefficient of thermal softening;
the actual plastic deformation strain rate;
a preset plastic deformation reference rate; epsilon is the equivalent plastic strain of the strain,T*＝(T-Tr)/(Tm-Tr) For temperature-related dimensions, TrFor reference temperature, TmIs the melting point temperature. (A + B. epsilon.)n)、
[1-(T*)m]The work hardening effect, strain rate effect and temperature softening effect of the material are described separately.
When the properties of the high-temperature alloy material are given to the linear friction welding geometric model with the initial defects introduced in the step 1, the material properties of the initial defect holes and the material properties of the inclusions are slightly different according to the material properties of the defects. The defect type of the holes is a circular through hole, the part does not need to be endowed with the property of a high-temperature alloy material, and the phenomena of hole deformation and closing exist in the linear friction welding process; the inclusion defect is round inclusion, the inclusion is only considered as hard inclusion, the part of the inclusion is set as a rigid body, the deformation phenomenon does not occur in the linear friction welding process, but the part needs to be endowed with the section attribute of the high-temperature alloy.
And step 3: selecting ALE adaptive grid parameters and quality scaling parameters:
and (2) performing under an ABAQUS software Step module, endowing the geometric model with section attributes including the frequency of the ALE self-adaptive grid and parameters such as a rescanning grid for each incremental Step based on the steps 1 and 2, fully considering the influence of a quality scaling factor of the whole model on a numerical simulation result under the condition of ensuring the model precision, and determining the ALE self-adaptive grid parameters and the quality scaling parameters. The method mainly sets Frequency and Mesh sweets in ALE self-adaptive grid parameters, wherein the Frequency control mainly controls the number of times of grid Remesh in the whole Step Time, and the Remesh number n can be represented by a formula (2); the invention relates to a linear friction welding numerical simulation method introducing initial defects based on ABAQUS, which is characterized in that Mesh sweet control parameters are iteration times under a Frequency, and when the value of the parameters is n, each Mesh sweet process carries out sweet for n times on a grid. The selection principle of the mass scaling parameters can be characterized by an estimation formula (3) showing the stability limit of the dynamic process;
n＝Incrementnumber/Frequency (2)
wherein L iseIs the minimum characteristic unit length, cdIs the expansion wave velocity of the material; the expansion wave velocity of the material may in turn be characterized by equation (4);
wherein E is Young's modulus and rho is material density;
and 4, step 4: carry out the friction heat production and the setting of rete heat dissipation between the contact surface:
setting is mainly carried out on an ABAQUS software Interaction module based on the steps 1-3; the workpiece which does reciprocating linear motion in the linear friction welding process and the workpiece which applies upsetting pressure move at high speed and rub quickly, and the contact and heat dissipation conditions of the welded workpiece in the actual linear friction welding process are considered; in the numerical simulation process of linear friction welding, friction heat generation between contact surfaces of a vibration rigid body workpiece and a deformation body workpiece is set, and the friction heat generation of the friction welding comprises three stages of a coulomb dry friction stage, a coulomb-adhesion friction stage and an adhesion friction stage. Interfacial friction heat generation during friction welding is characterized by equation (5); meanwhile, the influence of heat conduction between the deformation body workpiece and the clamp and the heat radiation of a welding seam in the air on each physical field of a defect adjacent region is considered in the welding process, film layer heat dissipation is carried out on each part of the deformation body workpiece, the heat dissipation modes in the welding process are multiple, and different welding modes are adoptedUnder the working condition, specific heat dissipation conditions are difficult to determine, so that the heat transfer coefficient adopted in the literature is referred for simplifying calculation, and the heat dissipation of the free end of the linear friction welding joint introducing the initial defects is slow, so that the convective heat transfer coefficient is set to be 30W/(m)2DEG C), and the clamping end can rapidly dissipate heat through the clamp, so the convection heat transfer coefficient is set to 1000W/(m)2C.g. to be prepared into a preparation. And simultaneously, the contact mode between the 2D deformation workpiece and the vibration rigid body workpiece is defined by surface-surface contact. The control equation of the deformation body workpiece heat transfer module is characterized by an equation (6) and an equation (7);
q＝[(1-δ)μPv]+(δητyv) (5)
wherein (1-delta) mu Pv is the dry friction heat production quantity, delta eta tauyv is the amount of sticking friction, δ state variable represents the sticking friction ratio, which has a value of 0-1, μ is the coefficient of friction, P is the friction pressure, v is the linear velocity of friction, η is the efficiency of conversion of mechanical energy to thermal energy, τyIs the material shear stress.
Wherein c ispConstant pressure heat capacity of the high-temperature alloy, and rho is the density of the high-temperature alloy; Δ Q is the amount of heat transferred into the body of the microelement per unit time.
And 5: setting load and boundary, applying predefined temperature field:
a Load module is arranged in the ABAQUS, and mainly used for applying upsetting force to the clamping end of the 2D deformable body workpiece in the step 1 and limiting the displacement of the clamping end in the X direction and the rotation of an X-Y plane; limiting displacement of the vibration rigid workpiece in the Y direction and rotation of the vibration rigid workpiece in the X-Y direction, and defining a periodic amplitude curve of linear vibration of the vibration rigid workpiece, wherein the periodic amplitude curve is represented by Fourier (Fourier) fractional expressions (8) and (9); the actual high-temperature alloy linear friction welding process is carried out at normal temperature, and the predefined temperature of the 2D deformation body workpiece and the vibration rigid body workpiece is determined to be 25 ℃.
t≥t0The method comprises the following steps: amplitude value
t＜t0The method comprises the following steps: amplitude a ═ A0(9)
Wherein N is the number of Fourier series terms; omega is the circumferential frequency; t is t0Is the starting time; a. the0Is the initial amplitude; a. thenA coefficient being a cos term (n ═ 1,2,3, …); beta is anIs the coefficient of the cos term.
Step 6: setting grid attributes:
setting is performed in a Mesh module in the ABAQUS; in the linear friction welding process, metals at different positions are affected differently by heat and force action in the welding process, wherein the metals in a welding seam area and a heat affected area not only have rapid temperature rise and fall, but also have severe plastic deformation, and in order to reflect the evolution of each parameter field and ensure the calculation accuracy, the calculation grids of the welding seam area and the heat affected area are small; and the metal of the base metal area only depends on heat transfer, so the temperature is not very high, and plastic deformation is not generated, and the calculation grid of the area has a larger size for saving the calculation cost and improving the calculation efficiency. Finally, determining the mesh size of the 2D deformation body workpiece in the linear friction welding finite element model introduced with the initial defects, which is set in the step 1, by dividing mainly adopting a mode of integral seed distribution and edge seed distribution; the grids are gradually refined from a base material area to a welding seam area, the initial defect hole and inclusion adjacent area need to be provided with finer grids, the grid control attributes are a quadrilateral free-stepping algorithm and a quadrilateral-based free-stepping algorithm, the unit type selects an explicit CPE4RT four-node thermal coupling plane strain quadrilateral unit, the bilinear displacement and the temperature are adopted, and the reduction integral and the hourglass are adopted to control. The grid size near the defect is selected to be 1/10 of the grid size of the welding seam area, and the accuracy of the numerical simulation calculation process is guaranteed.
And 7: simulation calculation and post-processing analysis:
the steps are correctly set based on the first 6 steps and are carried out in a Job module of ABAQUS software, so that the calculation process is mainly monitored in real time, and the convergence of the calculation process is ensured; analyzing a plurality of physical fields such as a temperature field, a stress strain field, a speed field and the like of the linear friction welding finite element model with the introduced initial defects; the method has the advantages that a plurality of physical field sudden changes and evolution conditions of the defect tip region, such as stress sudden change, temperature sudden change, speed sudden change and the like, in the welding process are explored, the influence rule of introducing the defects on the linear friction welding numerical simulation process is researched, the scientificity and reliability of the research of the high-temperature-resistant material (containing the initial defects) in the linear friction welding process are explored and improved, technical support is provided for the linear friction welding of the high-temperature-resistant material, and the method is better served in the high-end manufacturing fields of aerospace and the like.
Example 1:
the specific method of the embodiment comprises the following steps:
(1) establishing a geometric model:
establishing a two-dimensional geometric model by using a Part module in ABAQUS, wherein the two-dimensional geometric model comprises a deformable body workpiece and a vibration rigid body workpiece, and the geometric model of the deformable body workpiece is rectangular, 40mm in length and 18mm in width; the vibration rigid body workpiece is a two-dimensional analysis rigid body with the length of 60 mm. And dividing the deformation body workpiece into areas, wherein the clamping end area is a rectangular geometric model of 18mm x 30mm, and the welding free end area is a rectangular geometric model of 18mm x 10 mm. In the invention, the case introduces the initial defect of a single hole, the hole is positioned in a welding seam area and is 3.5mm away from a welding interface, the distance from the boundary of a sample is 9mm, the radius of the hole is 30um, and the finite element model in the embodiment is shown in the figure 2.
(2) Defining mechanical parameters, thermodynamic parameters and Johnson-Cook constitutive parameters of the high-temperature alloy:
defining material attribute parameters by adopting a Property module in ABAQUS, creating an entity homogeneous section, and assigning the section attribute to a high-temperature alloy deformation body workpiece with initial defects introduced; the material property parameters of this example are shown in figure description 3.
(3) Selecting ALE self-adaptive grid parameters and quality scaling factors:
setting a welding free area in the Step of establishing a geometric model as a self-adaptive grid control area by adopting a Step module in ABAQUS, selecting the frequency to be 1 by adopting an ALE self-adaptive grid control mode of a curvature refinement volume algorithm with an improved length-width ratio, and selecting the number of the grid to be 100 for each incremental Step rescanning; setting a whole model semi-automatic mass scaling technology in the steps of power, temperature-displacement and display analysis, wherein the scaling coefficient is 30000;
(4) a contact and heat exchange step:
the method comprises the steps that an Interaction module in ABAQUS is arranged, the contact area of a deformable body workpiece and a vibration rigid body workpiece is provided with a surface of a motion contact method to be in contact with the surface, a limited slip formula is adopted, and contact action attributes are tangential friction behavior of friction coefficient changing along with temperature and normal behavior of hard contact by using a penalty friction formula.
(5) And setting a load and a boundary:
the step is that a Load module is arranged in ABAQUS, and 160MPa of upsetting pressure is applied to the 2D deformation body workpiece; limiting the displacement of the clamping end in the X direction and the rotation of the X-Y plane; limiting the displacement of the vibration rigid workpiece in the Y direction and the rotation of the vibration rigid workpiece in the X-Y direction, defining a linear vibration periodic amplitude curve of the vibration rigid workpiece, setting the amplitude of the linear vibration periodic amplitude curve to be 3mm and the vibration frequency to be 25 Hz; the predefined temperature of 25 ℃ is applied to the deformation body workpiece and the vibration rigid body workpiece.
(6) Grid attribute and control step:
the steps are set in a Mesh module in ABAQUS, and the approximate size of a grid around a hole defect is 1.25 multiplied by 10-5The mesh approximate size of the rest area of the welding seam area is 0.0006, and the mesh approximate size of the clamping end is 0.003. And (3) dividing the whole deformation body workpiece into grids, wherein the unit type is CPE4RT four-node thermally coupled plane strain quadrilateral unit, bilinear displacement and temperature are adopted, the integral is reduced, and hourglass control is performed.
(7) Calculating and post-processing analysis steps:
the steps are set in a Job module in the ABAQUS, and calculation refers to creating operation, submitting the operation for analysis and monitoring the convergence condition of the simulation process in real time; the post-processing analysis refers to the result analysis of the multi-physical fields such as temperature, stress strain and the like of the successfully calculated model, and the evolution rule of the stress strain, the temperature and the speed of the characteristic points of the area adjacent to the hole in the linear friction welding process is explored; the stress profile of the area adjacent to the hole as a result of the post-treatment analysis of this example is shown in FIG. 4.
The results show that: compared with the numerical simulation post-treatment analysis result of linear friction welding without introduced defects, the method obtains that the geometrical characteristics of the circular hole defects change, the circular hole defects are transited from a circle to an ellipse, and the hole closing rate reaches 20.349%; the highest temperature in the linear friction welding process after the defect of a single hole is introduced is slightly lower than that in the linear welding process without the defect; the maximum Mises stress is concentrated at the clamping position of the clamp, but the distribution trend of the maximum stress is changed, the extrusion amount of the flash is obviously reduced under the action of the hole defects, and the axial shortening is reduced to 0.4221 mm.
Example 2:
the specific method of the embodiment comprises the following steps:
(1) establishing a geometric model:
the dimension of the deformation body workpiece and the dimension of the vibration rigid body are the same as those in the step (1) in the embodiment 1, the deformation body workpiece is partitioned after being established, an inclusion region with the position and the dimension the same as those of the hole defect in the step (1) in the embodiment 1 is partitioned, the inclusion region with the diameter of 60mm is set as the rigid body by the subsequent interaction module, and the part is not deformed in the linear friction welding process.
(2) Defining mechanical parameters, thermodynamic parameters and Johnson-Cook constitutive parameters of the high-temperature alloy:
same as in step (2) of example 1.
(3) Selecting ALE self-adaptive grid parameters and quality scaling factors:
the same procedure as in step (3) of example 1.
(4) A contact and heat exchange step:
the same procedure as in step (4) of example 1.
(5) And setting a load and a boundary:
the same as in (5) in example 1.
(6) Grid attribute and control step:
the mesh division method and the cell attributes are the same as in step (6) in embodiment 1.
(7) Calculating and post-processing analysis steps:
same as in step (7) in example 1.
The results show that: compared with the numerical simulation post-treatment analysis result of linear friction welding without introducing defects and the example 1, the geometric characteristics of the circular inclusion defects are not changed, and the phenomena of deformation and closure are avoided; the highest temperature in the linear friction welding process after introducing a single inclusion defect is slightly higher than that in the linear welding process without defects; the maximum Mises stress is concentrated at the clamping position of the clamp, but the distribution trend of the maximum stress is changed, and the adjacent area of the circular inclusions is also a large Mises stress concentration area. Compared with a defect-free linear welding finite element model, the extrusion amount of the flash is obviously reduced under the action of the inclusion defect, and the axial shortening is reduced; compared with a finite element model with a single hole defect, the size of the flash is slightly larger, and the axial shortening is slightly larger.
Example 3:
the specific method of the embodiment comprises the following steps:
(1) establishing a geometric model:
the dimensions of the deformation body workpiece and the vibration rigid body are the same as those of the modeling step (1) in embodiment 1, the embodiment is a linear friction welding geometric model with two initial hole defects, the hole defects have the same diameter and are 60um, the hole center distance is 0.5mm, the distance between the hole defects and a friction interface is 3.5mm, and the distance between the hole defects and a sample boundary is 8.9 mm.
(2) Defining mechanical parameters, thermodynamic parameters and Johnson-Cook constitutive parameters of the high-temperature alloy:
same as in step (2) of example 1.
(3) Selecting ALE self-adaptive grid parameters and quality scaling factors:
the same procedure as in step (3) of example 1.
(4) A contact and heat exchange step:
the same procedure as in step (4) of example 1.
(5) And setting a load and a boundary:
the same as in (5) in example 1.
(6) Grid attribute and control step:
the mesh division method and the cell attributes are the same as in step (6) in embodiment 1.
(7) Calculating and post-processing analysis steps:
same as in step (7) in example 1.
The results show that: the linear bold numerical simulation result of two holes shows that the axial shrinkage after welding is 0.2099mm, and shrinkage and overlap extrusion capacity need be less than single hole far away and the linear bold numerical simulation result of mingling. The stress results show that the maximum Mises stress of this model is still concentrated in the clamping area. The temperature and the strain are distributed in a gradient way. For an actual linear hammer test, if a hole with a certain size exists in a raw material, the forming of a welding joint is deteriorated, the amount of flash foundation is reduced, the welding material is bound to reach the combination between atoms, and the mechanical property and even the service performance of the welding material are affected.
Example 4:
the specific method of the embodiment comprises the following steps:
(1) establishing a geometric model:
the size of the deformation body workpiece and the size of the vibration rigid body are the same as those of the modeling step (1) in the embodiment 1, the embodiment is a linear friction welding finite element model with two initial inclusion defects, the diameters of the inclusion defects are equal to 60um, the distance between the centers of the circular inclusions is 0.5mm, and the distance between the inclusion defects and a friction interface is 3.5mm and 8.9mm from a sample boundary.
(2) Defining mechanical parameters, thermodynamic parameters and Johnson-Cook constitutive parameters of the high-temperature alloy:
same as in step (2) of example 1.
(3) Selecting ALE self-adaptive grid parameters and quality scaling factors:
the same procedure as in step (3) of example 1.
(4) A contact and heat exchange step:
the same procedure as in step (4) of example 1.
(5) And setting a load and a boundary:
the same as in (5) in example 1.
(6) Grid attribute and control step:
the mesh division method and the cell attributes are the same as in step (6) in embodiment 1.
(7) Calculating and post-processing analysis steps:
same as in step (7) in example 1.
The results show that: the two linear hank numerical simulation results that mix with show, weld back axial shrinkage and be 0.3354mm, and shrinkage and overlap extrusion capacity are less than the linear hank numerical simulation result of introducing single hole and mixing with far away, and the deformation resistance that the two models that mix with received in the calculation process is also bigger some, and Mises stress maximum value is also than example 1,2,3 the model is big, and temperature and meeting an emergency are the gradient distribution. For an actual linear Han test, if a GH4169 high-temperature alloy sample contains hard inclusions with a certain large size, the forming and mechanical properties of a joint of the GH4169 high-temperature alloy sample and even the service performance of the GH4169 high-temperature alloy sample are influenced, and the GH4169 high-temperature alloy sample model has important guiding significance for the GH4169 high-temperature alloy sample.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (7)
1. A linear friction welding numerical simulation method for introducing initial defects is characterized by comprising the following specific steps:
step 1: establishing a finite element geometric model;
firstly, establishing a finite element geometric model of the high-temperature alloy defect-free linear friction welding by using an ABAQUS software Part module, wherein the geometric model comprises a 2D shell element deformation body workpiece and a 2D linear vibration rigid body workpiece, and has initial holes and inclusion defects; then dividing the deformation body workpiece into a welding seam area, a heat affected area and a base metal area, wherein the welding seam area is used as a welding free end, the heat affected area and the base metal area are used as welding clamping ends, and the defect position is arranged in the welding seam area;
step 2: setting material attribute parameters;
setting material Property parameters of the high-temperature alloy by adopting a Property module of ABAQUS software, creating a homogeneous section of a high-temperature alloy entity, and endowing the section Property of the geometric model of the 2D shell unit deformation body workpiece with the initial defect introduced in the step 1;
the material property parameters comprise A, B, n, C, m,
Tr、TmThe 8 parameters are related to the rheological stress sigma during the numerical simulation as follows:
wherein A, B and n are yield strength, strain hardening coefficient and strain hardening index of the material when the material is subjected to quasi-static deformation at room temperature respectively; c is the strain rate strengthening coefficient; m is the coefficient of thermal softening;
the actual plastic deformation strain rate;
a preset plastic deformation reference rate; epsilon is equivalent plastic strain, T*＝(T-Tr)/(Tm-Tr) For temperature-related dimensions, TrFor reference temperature, TmIs the melting point temperature; (A + B. epsilon.)n)、
Respectively describing the work hardening effect, the strain rate effect and the temperature softening effect of the material;
and step 3: selecting ALE self-adaptive grid parameters and quality scaling parameters;
under an ABAQUS software Step module, endowing a section attribute to the geometric model based on the steps 1 and 2, and determining ALE self-adaptive grid parameters and quality scaling parameters;
and 4, step 4: friction heat generation between contact surfaces and film layer heat dissipation are carried out;
in the ABAQUS software Interaction module, friction heat generation between contact surfaces of a vibration rigid body workpiece and a deformation body workpiece is set, and the friction heat generation is calculated by the following formula (5):
q＝[(1-δ)μPν]+(δητyν) (5)
wherein (1-delta) μ PV is dry friction heat generation amount, and δ η τyNu is adhesive friction amount, delta state variable represents adhesive friction proportion, the value is 0-1, mu is friction coefficient, P is friction pressure, v is friction linear velocity, eta is conversion efficiency of mechanical energy and heat energy, and tauyIs the material shear stress;
performing film layer heat dissipation setting on each part of the deformation body workpiece, and setting the convective heat transfer coefficient of the free end of the linear friction welding joint with the initial defect as 30W/(m)2DEG C.), the heat convection coefficient of the clamping end is set to 1000W/(m)2·℃)；
Then, simulating linear friction welding of the vibration rigid body workpiece and the deformation body workpiece;
and 5: setting load and boundary, and applying a predefined temperature field;
in an ABAQUS Load module, applying upsetting force to a 2D deformation body workpiece clamping end; defining a periodic amplitude curve of the linear vibration of the vibration rigid body, wherein the periodic amplitude curve is characterized by Fourier series equations (8) and (9):
t≥t0the method comprises the following steps: amplitude value
t＜t0The method comprises the following steps: amplitude a ═ A0 (9)
Wherein N is the number of Fourier series terms; omega is the circumferential frequency; t is t0Is the starting time; a. the0Is the initial amplitude; a. thenIs a coefficient of cos term, n is 1,2,3, …; beta is anIn sin termsA coefficient;
determining the predefined temperature of the deformation body workpiece and the vibration rigid body workpiece to be 25 ℃;
step 6: setting grid attributes;
in a Mesh module in ABAQUS, dividing and setting the Mesh size of a 2D deformable body workpiece by adopting a mode of integral seed distribution and edge seed distribution; the grids are gradually thinned from the parent metal area to the welding line area, and the initial defect hole and the inclusion adjacent area need to be provided with finer grids;
and 7: analog calculation and post-processing analysis;
in a Job module of ABAQUS software, monitoring an analog calculation process in real time to ensure the convergence of the calculation process; and analyzing a plurality of physical fields of a temperature field, a stress strain field and a speed field of the linear friction welding finite element model introduced with the initial defects.
2. The linear friction welding numerical simulation method of introducing initial defects according to claim 1, characterized in that: the defect types in the step 1 are circular holes and inclusions, and the number of the defects is 1 or 2.
3. The linear friction welding numerical simulation method of introducing initial defects according to claim 1, characterized in that: in the Step 3, Frequency and Mesh Sweeps in the ALE self-adaptive grid parameters are set, wherein the Frequency control is to control the number of times of grid Remesh in the whole Step Time, and the Remesh number x is represented by a formula (2); the Mesh sweet control parameter is iteration times under a Frequency, when the value of the parameter is x, each remesh process carries out x times sweet on the grid, one remesh is carried out at each increment step, the value of Frequency is set to be 1, and the value of the self-adaptive grid parameter is determined based on the above criteria;
n＝Incrementnumber/Frequency (2)
the selection principle of the mass scaling parameters is characterized by an estimation formula (3) showing the stability limit of the dynamic process;
wherein L iseIs the minimum characteristic unit length, cdIs the expansion wave velocity of the material; the expansion wave velocity of the material is characterized by equation (4);
where E is the Young's modulus and ρ is the material density.
4. The linear friction welding numerical simulation method of introducing initial defects according to claim 1, characterized in that: and 3, setting the welding free end of the geometric model as an adaptive grid control area.
5. The linear friction welding numerical simulation method of introducing initial defects according to claim 1, characterized in that: in the simulation process of the vibration rigid body workpiece and the deformation body workpiece in the step 4, the control equation of the deformation body workpiece heat transfer module is represented by a formula (6) and a formula (7);
wherein, cpConstant pressure heat capacity of the high-temperature alloy, and rho is the density of the high-temperature alloy; Δ Q is the amount of heat transferred into the body of the microelement per unit time.
6. The linear friction welding numerical simulation method of introducing initial defects according to claim 1, characterized in that: when the upsetting force is applied to the clamping end of the 2D deformable body workpiece in the step 5, limiting the displacement of the clamping end in the X direction and the rotation of an X-Y plane; and limiting the displacement of the vibration rigid body workpiece in the Y direction and the rotation of the vibration rigid body workpiece in the X-Y direction.
7. The linear friction welding numerical simulation method of introducing initial defects according to claim 1, characterized in that: the control attributes of the grids in the step 6 are a quadrilateral free-stepping algorithm and a quadrilateral-based free-stepping algorithm, the cell type selects an explicit CPE4RT four-node thermally coupled plane strain quadrilateral cell, bilinear displacement and temperature are adopted, and reduction integration and hourglass control are adopted; 1/10 where the grid size near the defect is the grid size of the weld area is selected.
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| CN112475659B (en) * | 2020-11-11 | 2022-05-10 | 西北工业大学 | Method for simulating crack behavior sequence of linear friction welding and joint CT sample thereof |
| CN112380752B (en) * | 2020-11-23 | 2022-11-25 | 南京理工大学 | Method for improving welding process of metal sheet by predicting welding heat treatment value of metal sheet |
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| CN112949147B (en) * | 2021-04-01 | 2022-09-06 | 西北工业大学 | Uniaxial tension simulation calculation method for linear friction welding joint |
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