A rapid prediction method for the entire fatigue life of additive metals based on damage and fracture

Abstract

This invention relates to the field of metal fatigue prediction technology, and particularly to a method, apparatus, device, and computer-readable storage medium for rapid prediction of the entire fatigue life of additive metals based on damage and fracture. The method includes: acquiring the three-dimensional geometric parameters of internal void defects; calculating the porosity of each critical defect edge to obtain the critical load of the void defect; introducing an equivalent crack surface at the original defect location and calculating the equivalent initial crack length using a damage constitutive model; employing a semi-analytical crack propagation algorithm to calculate the propagation process of surface cracks, embedded cracks, and corner cracks in the component, obtaining the crack propagation life, and defining the shortest crack propagation life as the final structural fatigue life. The damage constitutive model fully considers the damage evolution and load coupling effect of defects, and the semi-analytical crack propagation calculation method, combined with an acceleration algorithm and crack conversion mechanism, significantly improves computational efficiency, meeting the rapid assessment needs in practical engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal fatigue prediction, and particularly relates to a damage and fracture based rapid prediction method and device for additive metal fatigue life, an electronic device and a computer readable storage medium. BACKGROUND

[0002] As a disruptive rapid prototyping technology, additive manufacturing has shown great potential in the field of material science and engineering. Compared with traditional metal forming methods, it has significant advantages in design and manufacturing integration, near-net shaping and coping with complex configurations, and gradually becomes the preferred path to solve many technical bottlenecks and challenges in the field of high-end equipment manufacturing. This technology can flexibly build components with highly complex geometric features, greatly widening the degree of freedom of product design and significantly shortening the cycle from design to prototype and finally to product, so its application prospect is broad and increasingly valued in the industrial fields such as aerospace, biomedicine, automobile and energy which have extremely strict requirements on structural performance and reliability.

[0003] However, the inherent characteristics of additive manufacturing process, such as layer-by-layer accumulation, rapid cooling and solidification and complex thermal history, make the final formed metal components inevitably have internal defects. These defects, of which porosity, un-melted area or inclusions are the most typical, have complex and variable geometric shapes, and the spatial distribution and orientation have high randomness, which directly and significantly adversely affect the macro-mechanical properties of the material, especially the fatigue performance. Under cyclic loading, fatigue failure often initiates from these defects and forms stress concentration at these places, eventually leading to structural failure. In order to ensure the service safety and reliability of additive manufacturing components, accurate assessment and prediction of their full life under fatigue load have become a key problem to be solved. SUMMARY

[0004] The present application aims to at least partially solve one of the technical problems in the related art.

[0005] To this end, the first object of the present application is to provide a damage and fracture based rapid prediction method for additive metal fatigue life, to solve the problem that the prior art cannot accurately assess and predict the full life of metal components under fatigue load.

[0006] The second object of the present application is to provide a device.

[0007] The third object of the present application is to provide an electronic device.

[0008] The fourth object of the present application is to provide a computer readable storage medium.

[0009] To achieve the above object, the first aspect of the present application proposes a method for rapid prediction of fatigue life of additive metal based on damage and fracture, comprising:

[0010] Performing non-destructive testing on the additive manufacturing metal component to obtain three-dimensional geometric parameters of internal hole defects;

[0011] Based on the three-dimensional geometric parameters, screening a plurality of defects with the largest defect size as dangerous defects;

[0012] Using a damage constitutive model to calculate the porosity of the edge of each dangerous defect to obtain the critical load of the hole defect;

[0013] Introducing an equivalent crack surface at the original position of the defect, and based on the critical load of the hole defect, using the damage constitutive model to calculate the equivalent initial crack length;

[0014] Based on the equivalent initial crack length, using a semi-analytical crack propagation algorithm to calculate the propagation process of surface cracks, internal cracks and corner cracks in the component to obtain the crack propagation life, and the shortest crack propagation life is determined as the final structure fatigue life.

[0015] Preferably, the non-destructive testing of the additive manufacturing metal component to obtain the three-dimensional geometric parameters of the internal hole defects comprises:

[0016] Using an industrial computed tomography system to perform three-dimensional non-destructive testing on the additive manufacturing metal component to obtain three-dimensional geometric information of internal defects of the additive manufacturing metal component;

[0017] Based on the three-dimensional geometric information, using a cone beam CT three-dimensional reconstruction algorithm to reconstruct the image, and performing image processing on the reconstructed image to generate three-dimensional geometric parameters of internal hole defects.

[0018] Preferably, the image processing includes gray threshold segmentation, connected domain analysis and morphological operation.

[0019] Preferably, the screening of a plurality of defects with the largest defect size as dangerous defects based on the three-dimensional geometric parameters comprises:

[0020] Based on the size of the three-dimensional geometric parameters, sorting the defects from large to small according to the defect size, and selecting a plurality of defects with the largest size as dangerous defects for fatigue life calculation.

[0021] Preferably, the use of a damage constitutive model to calculate the porosity of the edge of each dangerous defect to obtain the critical load of the hole defect comprises:

[0022] Constructing a three-dimensional finite model containing an ellipsoidal hole, and the outside of the hole is a nearly infinite or finite solid;

[0023] applying a tensile load consistent with the actual load direction to the three-dimensional finite model;

[0024] calculating the porosity of each point on the hole edge in real time using the damage constitutive model;

[0025] gradually increasing the load until the porosity of a certain place on the hole edge first reaches the pre-set critical porosity of the material, at which time the external load is the critical load of the hole defect.

[0026] Preferably, the introduction of an equivalent crack surface at the original position of the defect, based on the critical load of the hole defect, includes:

[0027] reconstructing a three-dimensional finite model, removing the ellipsoidal hole space, and placing a crack surface at its original position;

[0028] applying a tensile load to the reconstructed three-dimensional finite model in the same direction as the actual mechanical load, calculating the porosity of the crack tip using the damage constitutive model, and adjusting the crack length, when the porosity of the crack tip reaches the critical porosity, the corresponding crack length at this time is the equivalent initial crack length of the defect.

[0029] Preferably, based on the equivalent initial crack length, a semi-analytical crack propagation algorithm is used to calculate the propagation process of surface cracks, internal cracks and corner cracks in the component, obtain the crack propagation life, and the shortest crack propagation life is determined as the final structure fatigue life, which includes:

[0030] Based on the equivalent initial crack length, a semi-analytical crack propagation algorithm is used to calculate the propagation rate and direction of surface cracks, internal cracks and corner cracks, wherein the stress intensity factor is quickly calculated using an analytical formula;

[0031] Based on the stress intensity factor, the crack propagation amount is calculated using a crack propagation rate equation;

[0032] A crack form conversion rule is introduced, when the crack front reaches the free surface or the boundary of the component, the crack type is immediately changed according to the pre-set rule, and the life consumed by the crack conversion itself is ignored;

[0033] When the crack penetrates the entire cross section, it is determined to be invalid, and the cumulative cycle number is the crack propagation life corresponding to the dangerous defect, which is the final structure fatigue life.

[0034] To achieve the above purpose, the second aspect of the embodiment of the application proposes a kind of based on damage and fracture of metal fatigue life quick prediction device of addition, comprising:

[0035] The data acquisition module is configured to perform nondestructive testing on the metal component manufactured by additive manufacturing, and to acquire three-dimensional geometric parameters of internal hole defects;

[0036] The dangerous defect selection module is configured to select a plurality of defects with the largest defect size as dangerous defects based on the three-dimensional geometric parameters;

[0037] The critical load calculation module is configured to calculate the porosity of the edge of each dangerous defect by using a damage constitutive model, and to acquire the critical load of the hole defect;

[0038] The equivalent crack calculation module is configured to introduce an equivalent crack surface at the original position of the defect, to calculate the equivalent initial crack length by using the damage constitutive model based on the critical load of the hole defect;

[0039] The fatigue full life acquisition module is configured to calculate the propagation process of surface cracks, internal cracks and corner cracks in the component by using a semi-analytical crack propagation algorithm based on the equivalent initial crack length, to obtain crack propagation life, and to determine the shortest crack propagation life as the final structural fatigue full life.

[0040] To achieve the above purpose, a third aspect of the present application provides an electronic device, comprising: a processor, and a memory connected with the processor in communication;

[0041] The memory stores computer execution instructions;

[0042] The processor executes the computer execution instructions stored in the memory to implement the method of any one of the above.

[0043] To achieve the above purpose, a fourth aspect of the present application provides a computer readable storage medium, comprising computer execution instructions stored in the computer readable storage medium, the computer execution instructions being executed by a processor to implement the method of any one of the above.

[0044] The method provided by the present application is a rapid prediction method for additive metal fatigue full life based on damage and fracture, which aims to overcome the limitations of the prior art in additive metal fatigue life prediction. The damage constitutive model is used to fully consider the coupling effect of defect damage evolution and load, so as to determine the equivalent initial crack length with more physical meaning. The semi-analytical crack propagation calculation method combined with the acceleration algorithm and the crack conversion mechanism significantly improves the calculation efficiency, so that it can meet the rapid evaluation demand in engineering practice. The method provides more reliable and conservative fatigue life prediction results by comprehensively analyzing a plurality of potential dangerous defects and using the shortest life as the total life of the component, which has important guiding significance for the design, certification and service safety of the additive manufacturing metal component.

[0045] Additional aspects and advantages of the present application will be made apparent by the following description and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0046] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the accompanying drawings.

[0047] Figure 1 A flow chart of a first specific embodiment of a damage and fracture based rapid fatigue life prediction method for additive metal provided by the present application;

[0048] Figure 2 A flow chart of a second specific embodiment of a damage and fracture based rapid fatigue life prediction method for additive metal provided by the present application;

[0049] Figure 3 A GTN model parameter diagram for IN718 alloy;

[0050] Figure 4 A real stress-strain curve and a stress-strain curve schematic diagram of a material under a Ramberg-Osgood model;

[0051] Figure 5 A surface semi-elliptical crack schematic diagram;

[0052] Figure 6 A schematic diagram of an internal embedded elliptical crack;

[0053] Figure 7 A corner crack schematic diagram;

[0054] Figure 8 A crack conversion schematic diagram, wherein the dashed line is the original crack and the solid line is the new crack;

[0055] Figure 9 A structural block diagram of a damage and fracture based rapid fatigue life prediction device for additive metal provided by an embodiment of the present application. DETAILED DESCRIPTION

[0056] The core of the present application is to provide a damage and fracture based rapid fatigue life prediction method, device, electronic equipment and computer readable storage medium for additive metal, which integrates the principles of damage mechanics and fracture mechanics to accurately model and analyze the complex defects inside the additive manufacturing metal components, and realizes accurate and rapid prediction of the fatigue life of the components.

[0057] For those skilled in the technical field, the present application will be further described in detail below in combination with the drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0058] Please refer to Figure 1 , Figure 1 A flow chart of a first specific embodiment of a damage and fracture based additive metal fatigue life prediction method provided by the present application; the specific operation steps are as follows:

[0059] Step S101: Non-destructive testing of additive manufacturing metal components to obtain three-dimensional geometric parameters of internal hole defects;

[0060] Step S102: Based on the three-dimensional geometric parameters, multiple defects with the largest defect size are selected as dangerous defects;

[0061] Step S103: Calculate the porosity of the edge of each dangerous defect using the damage constitutive model to obtain the critical load of the hole defect;

[0062] Step S104: Introduce an equivalent crack surface at the original position of the defect, and based on the critical load of the hole defect, calculate the equivalent initial crack length using the damage constitutive model;

[0063] Step S105: Based on the equivalent initial crack length, use the semi-analytical crack propagation algorithm to calculate the propagation process of surface cracks, internal cracks and corner cracks in the component, obtain the crack propagation life, and the shortest crack propagation life is defined as the final structure fatigue life.

[0064] Based on the above embodiments, step S101 is described in detail in this embodiment:

[0065] In one embodiment, an industrial computed tomography system is used to perform three-dimensional non-destructive testing on the additive manufacturing metal component to obtain three-dimensional geometric information of internal defects of the additive manufacturing metal component;

[0066] Based on the three-dimensional geometric information, a cone beam CT three-dimensional reconstruction algorithm is used for image reconstruction, and the reconstructed image is processed to generate three-dimensional geometric parameters of internal hole defects, wherein the image processing includes gray threshold segmentation, connected domain analysis and morphological operation.

[0067] Specifically, a three-dimensional non-destructive testing is performed on the additive manufacturing metal component by using an industrial computed tomography (CT) system to obtain three-dimensional geometric information of internal defects of the component, wherein the industrial CT scanning system is configured with an X-ray tube and a flat panel detector.

[0068] The original projection data obtained by the CT scanning is subjected to image reconstruction by using a cone beam CT three-dimensional reconstruction algorithm to generate three-dimensional voxel data of the component.

[0069] The three-dimensional voxel data is subjected to image processing, wherein the image processing includes gray threshold segmentation, connected domain analysis and morphological operation to accurately identify and separate defects such as pores, unfused areas or inclusions inside the component.

[0070] For each identified defect, specific geometric parameters are extracted, wherein the geometric parameters include an equivalent ellipsoid long axis, a central axis, a short axis length of the defect, a spatial direction vector of the ellipsoid, a centroid coordinate of the defect, a volume of the defect, a surface area of the defect and a shape factor; and based on a preset defect size threshold or in combination with preliminary local stress concentration analysis, a plurality of potential dangerous defects having a significant influence on the fatigue life of the component are selected from all the identified defects as key objects for subsequent accurate analysis, and for a defect with a complex shape, the geometric shape is simplified to an approximate ellipsoid shape or a shape composed of multiple simple geometric bodies.

[0071] Based on the above embodiment, step S102 is described in detail in this embodiment.

[0072] In one embodiment, the defects are sorted in descending order of size based on the size of the three-dimensional geometric parameters, and a plurality of defects with the largest size are selected as dangerous defects for fatigue life calculation.

[0073] Based on the above embodiment, step S103 is described in detail in this embodiment.

[0074] In one embodiment, a three-dimensional finite model containing an ellipsoidal hole is constructed, and outside the hole is a near-infinite or finite solid entity.

[0075] A tensile load consistent with the actual load direction is applied to the three-dimensional finite model.

[0076] The porosity of each point on the hole edge is calculated in real time by using a damage constitutive model.

[0077] The load is gradually increased until the porosity of a certain place on the hole edge first reaches a preset critical porosity of the material, at which time the external load is the critical load of the hole defect.

[0078] Specifically, a local three-dimensional finite element model is constructed, which contains a solid region embedded with a defect geometry, wherein the boundary size of the solid region is 10 to 20 times the characteristic size of the defect;

[0079] In the finite element model, a damage constitutive model (GTN) is integrated through a user subroutine or a built-in material model interface;

[0080] The finite element model is meshed, and a refined meshing strategy is adopted at the defect edge and the vicinity thereof, so as to ensure that the local mesh size is less than 1 / 10 of the characteristic size of the defect, and the mesh element type is an eight-node hexahedral reduced integration element (C3D8R); and a coarse mesh is adopted in a far-field region;

[0081] A cyclic tensile load matching the actual service condition of the component is applied, the load can be uniaxial tension or complex multiaxial tension load, the load direction fully considers the relative orientation relationship with the long axis of the defect, and the boundary condition of the model is set to avoid rigid body displacement and simulate the far-field infinite body effect;

[0082] Numerical iteration calculation is performed to gradually increase the external load in an incremental step manner, in each load incremental step, the evolution of the stress, strain and porosity of each point of the defect edge is calculated through the GTN model; and the macroscopic failure of the defect is determined by using a critical porosity criterion, the evolution of the porosity of the defect edge is continuously monitored, when the porosity of any point of the defect edge reaches the critical porosity, the external load value at this time is recorded, which is defined as the critical load of the macroscopic failure of the defect.

[0083] Based on the above embodiment, step S104 is described in detail in this embodiment:

[0084] In one embodiment, a three-dimensional finite model is reconstructed, the ellipsoidal hole space is removed, and a crack surface is placed at the original position; a tensile load same as the actual mechanical load direction is applied to the reconstructed three-dimensional finite model, the porosity of the crack tip is calculated by using the damage constitutive model, and the crack length is adjusted; when the porosity of the crack tip reaches the critical porosity, the crack length corresponding to this time is the equivalent initial crack length of the defect.

[0085] Specifically, a three-dimensional finite element model is reconstructed, an ellipsoidal hole space is removed, and a crack surface is placed at the original position of the ellipsoidal hole. The shape of the crack surface is determined according to the position of the ellipsoidal hole in the structure, for example, the crack surface of an internal defect is an ellipse, and the crack surface of a surface defect is a semi-ellipse. The normal of the crack surface should be perpendicular to the long axis direction of the ellipsoidal hole, and the long axis of the crack surface is in the same direction as the long axis of the ellipsoidal hole. A tensile load is applied in the same direction as the actual mechanical load, and the load size is the critical load. The porosity at the crack tip is calculated by the GTN model, and the crack length is adjusted. When the porosity at the crack tip reaches the critical porosity, the crack length is determined as the equivalent crack length.

[0086] Based on the above embodiment, step S104 is described in detail in this embodiment:

[0087] In one embodiment, based on the equivalent initial crack length, a semi-analytical crack propagation algorithm is used to calculate the propagation rate and direction of surface cracks, internal cracks and corner cracks. The stress intensity factor is quickly calculated using an analytical formula;

[0088] Based on the stress intensity factor, the crack propagation amount is calculated using a crack propagation rate equation;

[0089] A crack form conversion rule is introduced. When the crack front reaches the free surface or the component boundary, the crack type is immediately changed according to the preset rule, and the life consumed by the crack conversion itself is ignored;

[0090] When the crack penetrates the entire cross section, it is determined to be invalid, and the cumulative cycle number is the crack propagation life of the dangerous defect, that is, the final structure fatigue life.

[0091] Specifically, the equivalent crack is set as the initial crack, and the crack propagation rapid calculation is carried out. The surface crack still expands in a semi-elliptical shape, the internal crack expands in an elliptical shape, and the corner crack expands in a quarter elliptical shape, and the aspect ratio of the crack is allowed to change. For a surface semi-elliptical crack, the crack shape change is calculated by calculating the crack front expansion amount of the surface point and the deepest point respectively. The crack stress intensity factor formula is queried and searched, and the crack propagation amount in two directions is calculated, including the direction parallel to the surface of the thin-walled structure and the thickness direction of the thin-walled structure. The crack propagation rate is determined by the Paris equation. In order to accelerate the calculation, the maximum crack propagation amount of the same length is taken as an interval, and it is assumed that the crack is in the mth interval, and the length of the crack in the mth interval is to During the process, the stress intensity factor remains unchanged, and the crack propagation life in the mth interval satisfies the equation When the crack front encounters the specimen boundary during the propagation process, the crack form will be converted. In order to accelerate the simulation of the crack propagation process, the crack conversion mode needs to be simplified. In the method, it is assumed that the crack is immediately converted into a new crack when it propagates to the specimen boundary, and the crack propagation life consumed by the crack conversion process is ignored.

[0092] The rapid calculation of crack propagation is carried out for the 10 largest defects respectively, and the crack propagation life obtained based on the foregoing method is the fatigue full life when the defect is the main dangerous point. By comparing the fatigue full lives caused by each defect as the main one, the shortest life is determined as the final structure fatigue full life.

[0093] The embodiment provides a rapid prediction method for additive metal fatigue full life based on damage and fracture, and aims to overcome the limitations of the prior art in additive metal fatigue life prediction. The damage constitutive model is used to fully consider the coupling effect of defect damage evolution and load, so that a more physically meaningful equivalent initial crack length is determined. The semi-analytical crack propagation calculation method combined with the acceleration algorithm and the crack conversion mechanism significantly improves the calculation efficiency, so that it can meet the rapid evaluation demand in engineering practice. The method provides more reliable and conservative fatigue life prediction results by comprehensively analyzing multiple potential dangerous defects and adopting the shortest life as the total life of the component, so that it has important guiding significance for the design, certification and service safety of the additive manufacturing metal component.

[0094] Based on the foregoing embodiment, the model structure of the rapid prediction method for additive metal fatigue full life based on damage and fracture is described, as shown in Figure 2 , and specifically as follows:

[0095] Firstly, the hole defects in the additive structure are characterized by the industrial CT scanning technology, and the size, shape, direction and the like of the defects are obtained. Then, the defects with larger size are focused, which are usually more dangerous defects. For example, the 10 largest defects can be taken as the main analysis objects.

[0096] Finite element simulation calculation is carried out, and the critical load of each of the 10 largest hole defects is determined, including: constructing an ellipsoidal hole space, setting a nearly infinite three-dimensional entity with a size much larger than the hole outside, or setting a finite three-dimensional entity according to the distribution position (such as the near surface) of the hole defect in the structure. The mesh is divided, the tensile load same as the actual mechanical load direction is applied, the porosity of the ellipsoidal hole edge is calculated through the GTN model, and the size of the tensile load is adjusted. When the porosity of any place at the ellipsoidal hole edge reaches the critical porosity, the load is recorded as the critical load, that is, at this time, the bearing capacity of the hole edge decreases and damage begins to occur.

[0097] Carry out finite element simulation to determine the equivalent crack length of the largest 10 hole defects, including: build a three-dimensional finite element model, remove the ellipsoidal hole space, and place a crack surface at its original position. The crack surface shape is determined according to the position of the ellipsoidal hole in the structure, for example, for internal defects, the crack surface is elliptical, and for surface defects, the crack surface is semi-elliptical. The normal of the crack surface should be perpendicular to the long axis direction of the ellipsoidal hole, and the long axis of the crack surface is in the same direction as the long axis of the ellipsoidal hole. Apply the same tensile load as the actual mechanical load direction, and the load size is the critical load. Calculate the porosity at the crack tip by the GTN model, and adjust the crack length. When the porosity at the crack tip reaches the critical porosity, the crack length is determined as the equivalent crack length.

[0098] Set the equivalent crack as the initial crack and carry out rapid crack propagation calculation. Surface cracks still expand in the shape of semi-elliptical cracks, internal cracks expand in the shape of elliptical cracks, and corner cracks expand in the shape of quarter-elliptical cracks, and the aspect ratio of the cracks is allowed to change. For surface semi-elliptical cracks, the crack shape change is calculated by calculating the crack front expansion amount of the surface points and the deepest points respectively. Query the crack stress intensity factor formula, mainly to calculate the crack propagation amount in two directions, including the direction parallel to the surface of the thin-walled structure and the thickness direction of the thin-walled structure. The crack propagation rate is determined by the Paris equation. In order to speed up the calculation, the maximum crack propagation amount of the same length is taken as an interval, and it is assumed that the crack is in the mth interval, and the length of the crack in the mth interval is During the process, the stress intensity factor remains unchanged, and the crack propagation life in the mth interval satisfies the equation. When the crack front encounters the specimen boundary during the expansion process, crack conversion will occur. In order to speed up the simulation of the crack propagation process, the crack conversion mode needs to be simplified. In this method, it is assumed that the crack is immediately converted to a new crack when it expands to the specimen boundary, and the crack propagation life consumed by the crack conversion process is ignored.

[0099] Carry out rapid crack propagation calculation for the largest 10 defects respectively, and the crack propagation life obtained based on the foregoing method is the fatigue full life when the defect is the main dangerous point. Compare the fatigue full life caused by each defect as the main one, and the shortest life is determined as the final structure fatigue full life.

[0100] Based on the above embodiment, the damage constitutive model (GTN) is described as follows:

[0101] The GTN damage model considers the initiation, growth and combination of void defects in the yield function. The modified yield function F is written as

[0102]

[0103] In the formula,​ is the macroscopic von-Mises stress, is the yield stress of the matrix material, is the hydrostatic pressure, are model parameters, is the effective porosity, describing the significant reduction of the matrix material's load carrying capacity due to the coalescence of pores, expressed as:

[0104]

[0105] where , is the porosity at which pores start to coalesce, macroscopically manifested as the onset of the descending part of the stress-strain curve; is the porosity at the final failure. The increase of the total porosity can be divided into two parts, the nucleation and the growth , i.e.:

[0106]

[0107] where the growth part is related to the accumulation of plastic deformation, and the plastic incompressibility of the matrix material is assumed, expressed as

[0108]

[0109] is the volumetric part of the plastic strain rate tensor, the nucleation of pores is also controlled by the plastic strain, and its nucleation process obeys a normal distribution, expressed as

[0110]

[0111] where, is the volume fraction of the two-phase particles that can nucleate pores, and are the average strain and its standard deviation at the nucleation of pores, respectively, is the equivalent plastic strain, which can be calculated by the plastic work equivalence as

[0112]

[0113] In the above equations, there are 7 model parameters in total: . Some of the parameters have empirical values, for example , and the other 5 parameters can be obtained by fitting the monotonic tensile curve of the material: for example, simulate the monotonic tensile process in the commercial software ABAQUS, and adjust the parameter values to fit the engineering stress-strain curve obtained from the test by means of the optimization algorithm. For example, for IN718 alloy, the model parameters at room temperature are obtained as shown in Figure 3 , in which For fitting parameters or empirical parameters, both are constants, if the test results are sufficient, can be obtained by fitting test results, if the test data is less, can refer to the experience value, is the porosity when the pores begin to join, is the porosity when the final damage, is the volume fraction of two-phase particles that can occur pore germination, and respectively, the average strain and its standard deviation when the pore germination.

[0114] If the test results of the engineering stress-strain curve are not good, the Ramberg-Osgood model can also be used to give the material stress-strain relationship:

[0115]

[0116] Wherein are the Young's modulus and the plasticity-related parameters of the material, are the strain and stress, respectively. The stress-strain curves under different parameters are as follows Figure 4 Then the GTN model parameters are determined by fitting.

[0117] Based on the above embodiment, the equivalent initial crack length calculation method of the hole defect is described, as follows:

[0118] In order to calculate the equivalent crack length later, the critical load of the hole defect damage needs to be determined first. For this purpose, the hole defect in the additive structure is characterized by industrial CT scanning technology, and the size, shape, direction and other information of the defect are obtained. Then, the defects with larger size are focused on, which are usually more dangerous defects. Generally, the shape of the hole defect in additive manufacturing is similar to that of an ellipsoid. In order to facilitate calculation, we take the ellipsoid as a typical object to carry out finite element simulation calculation, as follows.

[0119] Construct an ellipsoidal hole space, and set a nearly infinite three-dimensional entity outside the size much larger than the hole, or set a finite three-dimensional entity according to the distribution position of the hole defect in the structure (such as near the surface).

[0120] Divide the mesh, apply the same tensile load as the actual mechanical load direction, and consider the orientation of the tensile load and the long axis of the ellipsoidal hole. Calculate the porosity of the edge of the ellipsoidal hole by the GTN model, adjust the size of the tensile load, and when the porosity of any point on the edge of the ellipsoidal hole reaches the critical porosity, the load is recorded as the critical load, that is, at this time the bearing capacity of the hole edge decreases and begins to damage.

[0121] Reconstruct the three-dimensional finite element model, remove the ellipsoidal hole space, and place a crack surface at its original position. The shape of the crack surface is determined according to the position of the ellipsoidal hole in the structure, for example, the crack surface of an internal defect is elliptical, and the crack surface of a surface defect is semi-elliptical. The normal of the crack surface should be perpendicular to the long axis direction of the ellipsoidal hole, and the long axis of the crack surface should be in the same direction as the long axis of the ellipsoidal hole.

[0122] Apply a tensile load in the same direction as the actual mechanical load, with a load size of the critical load. Calculate the porosity at the crack tip using the GTN model, and adjust the crack length. When the porosity at the crack tip reaches the critical porosity, the crack length is determined as the equivalent crack length.

[0123] Based on the above embodiment, the crack propagation rapid calculation method is described as follows:

[0124] In the process of engineering design, fatigue crack propagation life analysis is one of the important means to determine the safety of parts. The commonly used crack propagation life calculation can be carried out in two ways, numerical calculation method and semi-analytical method. Numerical calculation method needs to establish model, divide elements, and calculate stress intensity factor distribution and crack propagation amount at crack tip week by week. During the calculation process, mesh division is needed week by week, and finite element software needs to be called for calculation, which requires a large amount of computing resources and computing time, and cannot be used for rapid crack propagation life estimation.

[0125] In order to carry out rapid crack propagation life analysis, semi-analytical method can be used for crack propagation life analysis. This process can simplify the specimen into simple shapes such as plate, cylindrical, pipe specimen, etc. The crack can also be simplified into surface semi-elliptical crack, internal elliptical crack, corner crack and edge crack, etc. After simplification, the stress intensity factor distribution at the crack tip can be calculated by empirical formula, so the crack propagation process can be calculated quickly. In the analysis of surface single crack propagation, the crack is usually simplified as a surface semi-elliptical crack. When using analytical method and finite element method to analyze crack propagation, different ways such as single degree of freedom, double degree of freedom and multi-degree of freedom can be used. The double degree of freedom method is widely used because of its accuracy and rapidity.

[0126] In the double degree of freedom assumption, the surface crack still expands in the form of semi-elliptical crack, the internal crack expands in the form of elliptical crack, the corner crack expands in the form of quarter elliptical crack, and the aspect ratio of the crack is allowed to change. For surface semi-elliptical crack, the crack shape change is calculated by calculating the crack front expansion amount of surface point and deepest point respectively.

[0127] According to the location of the crack in the plate, the plane crack can be divided into three types: corner crack, edge crack and embedded crack. The initial crack front shape is complex and cannot be used in the calculation of the two-degree-of-freedom fatigue crack propagation. Even if the finite element method is used, the initial shape of the crack cannot be completely guaranteed after meshing. Therefore, the shape of the plane crack needs to be simplified in the calculation.

[0128] The stress intensity factor of the elliptical crack in the plate exists, and the stress intensity factor formula can be used to calculate the crack propagation in two directions. As shown in Figure 5 、 Figure 6 、 Figure 7 , the size of the simplified crack parallel to the length direction of the plate (i.e. parallel to the surface direction of the thin-walled structure) is or , and the size perpendicular to the length direction of the plate (i.e. the thickness direction of the thin-walled structure) is or , the length of the plate is defined as , and the thickness is defined as . The distance of the crack surface center from the surface of the plate is , and in the figure is the angle between the crack front point and the length direction of the plate. Points A and C represent the two vertices of the elliptical crack front. When the simplified crack in a certain direction contains the complete elliptical shape in that direction, the size needs to be multiplied by 2.

[0129] Under the framework of linear elastic fracture mechanics, the crack propagation rate can be expressed by the Paris equation:

[0130]

[0131] where is the crack propagation amount when the cycle number is , and is the stress intensity factor range, is the fitting parameter. It should be noted that the stress intensity factor range is a function of the crack length, i.e. .

[0132] Although the use of stress intensity factor empirical formula to calculate the stress intensity factor and crack propagation is much more efficient than the use of finite element method, when the crack propagation life is long enough, the calculation time is still relatively long. Therefore, the algorithm needs to be accelerated, specifically the fixed crack length change , and the life of the calculation interval is . The maximum crack propagation amount with equal length is taken as an interval, and it is assumed that the crack propagates from length to during the mth interval, and the stress intensity factor remains unchanged. The crack propagation life in the mth interval satisfies the following equation,

[0133]

[0134] Since we simplify all the crack surfaces as ellipses or half-ellipses, 1 / 4-ellipses, we need to consider both the long axis direction and the short axis direction of the ellipse crack when calculating the crack propagation. After determining the crack propagation amount of these two main directions, we get the new crack surface based on the new long axis and short axis length.

[0135] In three-dimensional structures, the crack front will encounter the specimen boundary during the propagation process, and crack conversion will occur. To simulate the crack propagation process, the crack conversion mode needs to be simplified. There are several forms of crack conversion, such as Figure 8 as shown: internal crack conversion to surface crack (EC-SC); surface crack conversion to corner crack (SC-CC); surface crack conversion to through crack (SC-TC); corner crack conversion to side crack (CC-BC). The dashed line in the figure represents the crack front before conversion, and the corresponding crack size is represented by and . The crack size after conversion is represented by and .

[0136] In this method, it is assumed that the crack is immediately converted to a new crack when it propagates to the specimen boundary, and the crack propagation life consumed by the crack conversion process is ignored. Failure occurs when the crack propagates through the entire structure. Thus, the crack propagation life can be quickly calculated based on the equivalent initial crack, and the fatigue full life is ultimately obtained.

[0137] Please refer to Figure 9 , Figure 9 a structural block diagram of a device for quickly predicting the fatigue full life of additive metal based on damage and fracture provided by an embodiment of the present application; the specific device can include:

[0138] The data acquisition module 100 performs non-destructive testing on the additive manufacturing metal component to obtain the three-dimensional geometric parameters of the internal hole defects.

[0139] The dangerous defect selection module 200 selects a plurality of defects with the largest defect size as dangerous defects based on the three-dimensional geometric parameters.

[0140] The critical load calculation module 300 calculates the porosity of the edge of each dangerous defect using a damage constitutive model to obtain the critical load of the hole defect.

[0141] The equivalent crack calculation module 400 introduces an equivalent crack surface at the original position of the defect, and calculates the equivalent initial crack length based on the critical load of the hole defect using the damage constitutive model.

[0142] The fatigue life acquisition module 500 calculates the propagation process of surface cracks, internal embedded cracks and corner cracks in the component based on the equivalent initial crack length by using a semi-analytical crack propagation algorithm, obtains the crack propagation life, and determines the shortest crack propagation life as the final structural fatigue life.

[0143] The damage and fracture based rapid prediction device for additive metal fatigue life is used to realize the damage and fracture based rapid prediction method for additive metal fatigue life, and the specific embodiments of the damage and fracture based rapid prediction device for additive metal fatigue life can be seen from the foregoing embodiment part of the damage and fracture based rapid prediction method for additive metal fatigue life, for example, the data acquisition module 100, the dangerous defect selection module 200, the critical load calculation module 300, the equivalent crack calculation module 400, and the fatigue life acquisition module 500 are respectively used to realize steps S101, S102, S103, S104 and S105 in the damage and fracture based rapid prediction method for additive metal fatigue life, and therefore, the specific embodiments can refer to the description of the respective embodiments, and details are not repeated here.

[0144] In order to realize the foregoing embodiments, the present application further provides an electronic device, including a processor and a memory connected with the processor; the memory stores computer execution instructions; the processor executes the computer execution instructions stored in the memory to realize the method provided in the foregoing embodiments.

[0145] In order to realize the foregoing embodiments, the present application further provides a computer readable storage medium, and the computer readable storage medium stores computer execution instructions; the computer execution instructions are executed by a processor to realize the method provided in the foregoing embodiments.

[0146] In order to realize the foregoing embodiments, the present application further provides a computer program product, including a computer program, and the computer program is executed by a processor to realize the method provided in the foregoing embodiments.

[0147] The collection, storage, use, processing, transmission, provision and disclosure of user personal information involved in the present application comply with relevant laws and regulations and do not violate public order and good customs.

[0148] It is important to note that user's personal information should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection / sharing should occur after the user is made aware of and has consented to such collection / sharing, including being informed of the uses of their personal information as well as who will have access to their personal information as described above in the user agreement / user notification. Additionally, any steps necessary by the entity to safeguard and ensure the access to and / or revision of personal information data must be taken.

[0149] The present application contemplates that the embodiments can provide a user the ability to disable the collection, storage, and / or use of personal information data at the user's option. That is, the present disclosure contemplates providing each user with control over whether programs or features collect personal information data about them and to provide notice of the collection and the ability to opt-in or opt-out of the collection of the personal information data. In an embodiment, any use of personal information data will require the user's permission and user's may

[0150] In the preceding embodiment descriptions, reference has been made to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. It is to be understood that the specific features, structures, materials or characteristics that are described in relation to an embodiment or example are included in at least one embodiment or example of the present application. Illustrative expressions of the above terms are not necessarily directed at the same embodiment or example in the present specification. Furthermore, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Moreover, the person skilled in the art can combine and combine the features of different embodiments or examples and the features of different embodiments or examples described in the present specification, without contradiction.

[0151] In addition, the terms "first", "second", etc. are used herein only to describe all possible different combinations. These terms are in no way intended to imply or imply relative importance or imply the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one feature. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise explicitly specified.

[0152] Any process or method descriptions or descriptions of the flow diagrams described herein or otherwise described in this application can be understood as representing code modules, segments, or portions of code that include one or more executable instructions for implementing specific logic functions (or steps) in the process, and that the various embodiments of the application can include other implementations of hardware or software performing the same functions or process steps, in the same or a different order. In addition, the processes and methods described in this application can be implemented as code means or portions of code means that include one or more executable instructions for implementing specific logic functions (or steps) or as hardware or as some combination thereof.

[0153] The logic and / or steps represented in flow diagrams or otherwise described herein, for example, can be considered as a sequence of instructions to implement logic functions, and can be embodied in any computer-readable medium for use by an instruction execution system, apparatus, or device, such as a computer-based system, processor- containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this specification, a "computer-readable medium" can be any means that can contain, store, communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be a machine-readable storage device (e.g., magnetic, optical or other) a machine-readable storage diskette (e.g., floppy disk, optical disk, etc.), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), optical fibers, and a portable compact disc read-only memory (CDROM). Further, the computer-readable medium can even be paper or other suitable medium upon which the program is printed, as the program can be electronically captured, for example via the optical scanner of a device or other electronic capture device, and then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and stored in a computer memory.

[0154] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the above embodiments, various steps or methods can be implemented in software or firmware that is stored in memory and executed by a suitable instruction execution system. As such, in some embodiments, the steps or methods can be implemented in a combination of hardware and software. If implemented in hardware, as in another embodiment, any of the above techniques can be implemented with or without accompanying software or in software / firmware alone. The techniques can be implemented in one or more of discrete hardware components, application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, a combination thereof, or the like.

[0155] Those skilled in the art can understand that all or part of the steps involved in the above-mentioned embodiment methods can be completed by programs instructing related hardware, and the programs can be stored in a computer-readable storage medium. When the programs are executed, one or a combination of the steps of the method embodiments is included.

[0156] In addition, each of the functional units in the various embodiments of the present application can be integrated in one processing module, or each of the units can be physically present separately, or two or more units can be integrated in one module. The integrated module can be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer readable storage medium.

[0157] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for rapid prediction of full life fatigue of additive metal based on damage and fracture, characterized in that, The method comprises the following steps: Nondestructive testing is performed on the metal component manufactured by additive manufacturing to obtain three-dimensional geometric parameters of internal hole defects; Based on the three-dimensional geometric parameters, a plurality of defects with the largest defect size are screened as dangerous defects; The porosity of the edge of each dangerous defect is calculated using a damage constitutive model to obtain the critical load of the hole defect; An equivalent crack surface is introduced at the original position of the defect, and the equivalent initial crack length is calculated based on the critical load of the hole defect using the damage constitutive model; Based on the equivalent initial crack length, a semi-analytical crack propagation algorithm is used to calculate the propagation process of surface cracks, internal cracks and corner cracks in the component to obtain crack propagation life, and the shortest crack propagation life is determined as the final structural fatigue life; wherein, The calculation of the propagation process of surface cracks, internal cracks and corner cracks in the component based on the equivalent initial crack length using the semi-analytical crack propagation algorithm to obtain the crack propagation life, and the determination of the shortest crack propagation life as the final structural fatigue life comprise: Based on the equivalent initial crack length, a semi-analytical crack propagation algorithm is used to calculate the propagation rate and propagation direction of surface cracks, internal cracks and corner cracks, wherein the stress intensity factor is quickly calculated using an analytical formula; Based on the stress intensity factor, the crack propagation amount is calculated using a crack propagation rate equation; A crack form conversion rule is introduced, when the crack front reaches the free surface or the component boundary, the crack type is immediately changed according to the preset rule, and the life consumed by the crack conversion itself is ignored; When the crack penetrates through the entire cross section, it is determined to be failed, and the cumulative cycle number is the crack propagation life corresponding to the dangerous defect, which is the final structural fatigue life.

2. The damage and fracture based rapid prediction method of full life of additive metal fatigue according to claim 1, characterized in that, The nondestructive testing of the metal component manufactured by additive manufacturing to obtain three-dimensional geometric parameters of internal hole defects comprises: Three-dimensional nondestructive testing of the metal component manufactured by additive manufacturing is performed using an industrial computed tomography system to obtain three-dimensional geometric information of internal defects of the metal component manufactured by additive manufacturing; Based on the three-dimensional geometric information, a cone beam CT three-dimensional reconstruction algorithm is used for image reconstruction, and the reconstructed image is processed to generate three-dimensional geometric parameters of internal hole defects.

3. The damage and fracture based rapid prediction method of full life of additive metal fatigue according to claim 2, characterized in that, The image processing comprises: gray threshold segmentation, connected domain analysis and morphological operation.

4. The damage and fracture based rapid prediction method of full life of additive metal fatigue according to claim 1, characterized in that, The screening of a plurality of defects with the largest defect size as dangerous defects based on the three-dimensional geometric parameters comprises: Based on the size of the three-dimensional geometric parameters, the defects are sorted in descending order of defect size, and a plurality of defects with the largest size are selected as dangerous defects for fatigue life calculation.

5. The damage and fracture based rapid prediction method of full life of additive metal fatigue according to claim 1, characterized in that, The calculation of the porosity of the edge of each dangerous defect using a damage constitutive model to obtain the critical load of the hole defect comprises: A three-dimensional finite model containing an ellipsoidal hole is constructed, and the outside of the hole is a nearly infinite or finite solid; A tensile load consistent with the actual load direction is applied to the three-dimensional finite model; The porosity of each point on the hole edge is calculated in real time using a damage constitutive model; The load is gradually increased until the porosity of a certain point on the hole edge first reaches the preset critical porosity of the material, at which time the external load is the critical load of the hole defect.

6. The damage and fracture based rapid prediction method of full life of additive metal fatigue according to claim 1, characterized in that, The equivalent crack face is introduced at the original position of the defect, and the equivalent initial crack length is calculated based on the critical load of the hole defect by using the damage constitutive model, which comprises: A three-dimensional finite model is reconstructed, an ellipsoidal hole space is removed, and a crack face is placed at the original position thereof; A tensile load in the same direction as the actual mechanical load is applied to the reconstructed three-dimensional finite model, the porosity at the crack tip is calculated by using the damage constitutive model, and the crack length is adjusted, and when the porosity at the crack tip reaches the critical porosity, the crack length corresponding thereto is the equivalent initial crack length of the defect.

7. A device for rapid prediction of full life of additive metal fatigue based on damage and fracture, characterized by, It comprises: A data acquisition module for non-destructive testing of an additive manufacturing metal component to obtain three-dimensional geometric parameters of internal hole defects; A dangerous defect selection module for screening a plurality of defects with the largest defect size as dangerous defects based on the three-dimensional geometric parameters; A critical load calculation module for calculating the porosity of the edge of each dangerous defect by using the damage constitutive model to obtain the critical load of the hole defect; An equivalent crack calculation module for introducing an equivalent crack face at the original position of the defect, and calculating the equivalent initial crack length based on the critical load of the hole defect by using the damage constitutive model; A fatigue full life acquisition module for calculating the propagation process of surface cracks, internal cracks and corner cracks in the component based on the equivalent initial crack length by using a semi-analytical crack propagation algorithm to obtain crack propagation life, and determining the shortest crack propagation life as the final structure fatigue full life; wherein The fatigue full life acquisition module is further configured to: Based on the equivalent initial crack length, the semi-analytical crack propagation algorithm is used to calculate the propagation rate and direction of surface cracks, internal cracks and corner cracks, wherein the stress intensity factor is quickly obtained by using an analytical formula; Based on the stress intensity factor, the crack propagation amount is calculated by using a crack propagation rate equation; A crack form conversion rule is introduced, when the crack front reaches the free surface or the component boundary, the crack type is immediately changed according to the preset rule, and the life consumed by the crack conversion itself is ignored; When the crack penetrates through the entire cross section, it is determined to be failed, and the cumulative cycle number is the crack propagation life corresponding to the dangerous defect, which is the final structure fatigue full life.

8. An electronic device, comprising: It comprises: A processor and a memory in communication connection with the processor; The memory stores computer execution instructions; The processor executes the computer execution instructions stored in the memory to realize the method in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer execution instructions, and the computer execution instructions are executed by the processor to realize the method in any one of claims 1-6.

Images