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CN-119514334-B - Improved inherent strain loading method based on partition thought

CN119514334BCN 119514334 BCN119514334 BCN 119514334BCN-119514334-B

Abstract

The invention relates to an improved inherent strain loading method based on a partition idea, which comprises the following steps of carrying out clustering partition treatment on extracted inherent strain values unevenly distributed along a scanning path to obtain a set of different inherent strain classes of a small-scale thermal structure standard model component part under specific process parameters, namely a scale model inherent strain cluster analysis result, partitioning a structure to be printed according to the small-scale model inherent strain cluster analysis result, carrying out grid partitioning on the structure to be printed, obtaining centroid coordinates of each unit, judging the partition to which the unit belongs according to the centroid coordinates of the unit, changing the thermal expansion coefficient of each characteristic area unit of the structure to be printed according to the partition result of the structure to be printed to finish giving different inherent strain classes, and carrying out calculation of a layer-by-layer partition inherent strain method according to an actual layer-by-layer printing strategy to obtain deformation and stress distribution of the structure to be printed, so as to realize prediction of residual deformation and stress of the structure to be printed.

Inventors

  • YAN KUN
  • LIU YI
  • YAN JUN

Assignees

  • 大连理工大学

Dates

Publication Date
20260508
Application Date
20241031

Claims (7)

  1. 1. The improved inherent strain loading method based on the partition thought is characterized by comprising the following steps of: s1, designing a small-scale thermal structure standard model of a structure to be printed, extracting inherent strain values of all nodes of the small-scale thermal structure standard model along the scanning path direction under specific process parameters, and determining the distribution rule of the inherent strain values; s2, carrying out clustering partition treatment on the extracted inherent strain values unevenly distributed along the scanning path to obtain a set of different inherent strain classes of the small-scale thermal structure standard model component parts under specific technological parameters, namely an inherent strain cluster analysis result of the small-scale model; s3, partitioning the structure to be printed by taking the inherent strain cluster analysis result of the small-scale model as a basis, performing grid division on the structure to be printed, acquiring the barycenter coordinates of each unit, and judging the partition to which the unit belongs according to the barycenter coordinates of the unit; S4, changing the thermal expansion coefficients of each characteristic area unit of the structure to be printed according to the partitioning result of the structure to be printed so as to finish giving different inherent strains; and S5, completing calculation of a layer-by-layer partition inherent strain method according to an actual layer-by-layer printing strategy, obtaining deformation and stress distribution of the structure to be printed, and realizing prediction of residual deformation and stress of the structure to be printed.
  2. 2. The method for improving inherent strain loading based on the partition thought according to claim 1, wherein the small-scale thermostructural standard model is a three-layer deposition layer finite element model with a substrate.
  3. 3. The method for loading the improved inherent strain based on the partition thought of claim 1, wherein the inherent strain values of all nodes of the small-scale thermal structure standard model along the scanning path direction under the specific process parameter extraction are obtained by obtaining the inherent strain values of all nodes of the model along the scanning direction through unit-by-unit transient thermal coupling calculation.
  4. 4. The improved inherent strain loading method based on the partition thought of claim 1, wherein the clustering partition adopts a K-means method for cluster analysis, and the specific process is as follows: And selecting a proper class center number by taking the magnitude of the intrinsic strain value as a classification basis, classifying the extracted intrinsic strain of each point along the scanning direction to obtain intrinsic strain values of different characteristic areas, wherein the classification result is that the intrinsic strain class of each unit in the area with the length of 6mm at both sides of the scanning direction path is the contour intrinsic strain, and the intrinsic strain class of each unit in the middle area of the scanning direction path is the center intrinsic strain.
  5. 5. The improved inherent strain loading method based on the partitioning thought as set forth in claim 1, wherein the partitioning of the structure to be printed based on the result of the small scale model inherent strain cluster analysis is as follows: Firstly, dividing a structure to be printed into grid units, and then calculating the boundary distance between the centroid coordinates of the units and the structure to be printed, wherein the distance is less than or equal to 6mm, the boundary distance belongs to a contour unit, and otherwise, the boundary distance is a center unit.
  6. 6. The improved inherent strain loading method based on the partition thought according to claim 1 is characterized in that the thermal expansion coefficients of the characteristic area units of the structure to be printed are changed according to the partition result of the structure to be printed, so that the process of giving different inherent strain types is completed as follows: the different intrinsic strain classes are equivalent to the intrinsic properties of the material at a particular process parameter, introducing an intrinsic strain in the form of changing the coefficient of thermal expansion of the material.
  7. 7. The improved inherent strain loading method based on the partition thought of claim 1 is characterized in that the calculation of the inherent strain method of the layer-by-layer partition is completed according to an actual layer-by-layer printing strategy, the deformation and stress distribution of the structure to be printed are obtained, and the prediction process of the residual deformation and stress of the structure to be printed is realized as follows: firstly, after the inherent strain is endowed, inactivating all units of the structure to be printed so as to simulate the state that the material does not exist at the beginning of actual additive manufacturing, and then activating the units of the structure to be printed layer by layer, and carrying out one-time quasi-static mechanical analysis until the printing process is finished, thereby obtaining the residual stress and deformation field distribution of the structure to be printed.

Description

Improved inherent strain loading method based on partition thought Technical field: the invention belongs to the technical field of advanced additive manufacturing, and particularly relates to a method for efficiently predicting residual stress and deformation in additive manufacturing, which comprises an inherent strain distribution clustering method and a loading method based on a partition idea. The background technology is as follows: Additive manufacturing (AdditiveManufacturing, AM), commonly referred to as 3D printing, is a technique for manufacturing objects based on the addition of material layer by layer. The method is an innovative manufacturing technology, and the additive manufacturing greatly changes the production mode of the traditional manufacturing industry by providing design freedom, improving the material utilization rate, flexibly producing, reducing the links of a supply chain, reducing the assembly steps and reducing the weight design. The unique molding characteristics of the material have wide application prospect and research value in the fields of prototype manufacture, consumer electronics, biomedical treatment, automobiles, aerospace and the like. The GE aviation utilizes additive manufacturing technology to produce the fuel nozzle of the gas turbine engine, compared with the traditional manufacturing mode, the weight is reduced by 25 percent, and the strength and the performance of parts are improved. However, additive manufacturing also faces challenges such as product consistency and molding accuracy and quality control. The non-uniform thermal stress distribution during the build-up of each layer causes a series of formation quality problems due to non-uniform print parameters, non-uniform powder distribution, and different coefficients of thermal expansion and cooling shrinkage exhibited by the different materials during heating and cooling. These uneven stress distribution and molding quality problems can lead to part dimensional accuracy that does not meet design requirements, reduce part mechanical properties such as fatigue strength and toughness, and increase the risk of failure during use. Since the problems prevent the high-speed continuous development of additive manufacturing, research on evolution and mechanism of thermal behavior in the process of additive manufacturing has important significance for improving the precision and quality of the final product. However, due to the high cost of advanced additive technology materials, equipment, processes and the like, experimental research is not extensive. The manufacturing process can be simulated in the virtual environment by a simulation means, and the deformation and the residual stress of the part in the manufacturing process are predicted, so that a basis is provided for optimizing the manufacturing process. Simulation of macroscopic thermal problems for additive materials currently has two types, the first is a transient thermal coupling method, which needs to build a unit-by-unit or layer-by-layer thermal sequential coupling finite element model of the whole process, and then predict stress strain distribution through transient thermal coupling analysis. This overall process transient thermal coupling method requires consideration of thermal conduction, material phase change and mechanical response at the same time, resulting in unacceptable computational costs due to its high degree of non-linearity. The second is an inherent strain method, which converts thermal problems into purely mechanical problems, and can realize the prediction of residual stress and deformation in the structure printing process by only performing layer-by-layer quasi-static analysis. The inherent strain concept is first developed in the field of metal welding and then expanded to the field of additive manufacturing to solve the problems of residual stress and deformation prediction in the additive manufacturing process. The inherent strain calculated by the small-scale model under a certain specific process is used as the inherent attribute of the material, the inherent strain is loaded into the large-scale model in a pre-strain mode, and the structural residual stress and deformation field can be obtained by performing layer-by-layer static analysis, so that a large amount of calculation cost is saved. However, the current inherent strain analysis method lacks consideration of the actual distribution situation of the inherent strain, adopts the inherent strain after each point is averaged to carry out full model loading, and does not have good precision. Therefore, in order to efficiently predict the residual stress and deformation of the additive manufacturing, the method of the invention is improved on the basis of the second method so as to consider the actual inherent strain distribution situation to realize accurate prediction of the stress deformation. Disclosure of Invention The invention solves the problems that the prior i