CN113935205A - Method for optimizing parameters of plastic physical properties by utilizing finite element simulation - Google Patents

Method for optimizing parameters of plastic physical properties by utilizing finite element simulation Download PDF

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CN113935205A
CN113935205A CN202011543659.3A CN202011543659A CN113935205A CN 113935205 A CN113935205 A CN 113935205A CN 202011543659 A CN202011543659 A CN 202011543659A CN 113935205 A CN113935205 A CN 113935205A
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周宝泉
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Suzhou Bangkesi Information Technology Co ltd
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Abstract

The invention discloses a method for optimizing parameters of plastic physical properties by utilizing finite element simulation, which comprises the following steps of: judging whether the material belongs to 'new materials which are not measured' or 'materials with known partial property measurement', if the material belongs to 'new materials which are not measured', disclosing a database in finite element software to search plastics with similar properties for the 'new materials which are not measured', and acquiring the physical properties of the materials related to finite elements; respectively obtaining the physical properties of the materials, searching the model and the database thereof in finite element software, substituting finite element analysis to obtain a product quality result if the model and the database thereof are complete, and carrying out relevance test if the model and the database are incomplete. By adopting the method, the analysis result error caused by wrong use of the substitute materials with different properties and further the loss caused by the need of mold opening again can be avoided, the test time is short, the cost is reduced, and the accuracy of the analysis result is improved.

Description

Method for optimizing parameters of plastic physical properties by utilizing finite element simulation
Technical Field
The invention relates to the field of finite element simulation, in particular to a parameter optimization method for plastic physical properties by utilizing finite element simulation.
Background
Plastic articles are typically injection molded. The quality of injection molded products requires that the accuracy of appearance and size is emphasized, and the factors influencing the molding quality mainly include: materials, plastic part structures, mold structures and process parameters. Due to the high complexity of the injection molding process, the injection molding process is a nonlinear system, and besides the process parameters are adjusted on the production site to optimize the molding quality, the injection molding process generally relies on the finite element simulation before production to predict the molding quality. In the finite element simulation calculation, various mechanical, flow, heat and other physical properties used need to establish mathematical models which are different from materials; different materials need to be tested, specific parameters in a mathematical model of the materials are determined according to test results in a curve fitting mode, and each group of parameters corresponds to the property of a brand/model plastic. The user of the finite element simulation can select the correct material to perform the finite element simulation analysis according to the production requirement.
However, there are many types of plastics on the market, and the database built in the simulation software has the material parameters less than half of the maximum, and the new material comes out quickly, so that the user must spend a lot of money and time to measure the new material for use, but the data does not include the material parameters of the database included in the simulation software. Furthermore, some measurement items are limited by the mathematical model of materials not disclosed in the simulation software, so that the measurement can only be performed by the simulation software, which is relatively expensive, and the average waiting time is one month, which is not suitable for the development time of the current product, and lacks of security, so that the user is forced to abandon the use of the correct material parameters and only can search for the close alternative materials.
To address the dilemma of having no simulation software or having no appropriate parameters available, past attempts have included:
CN 103093062-parametric analysis method for influence of injection molding process on warping deformation of plastic parts, firstly, systematically using experimental design method, inputting different process conditions into finite element software to obtain a series of quality prediction results, then, using simple linear relationship to find out correlation between process conditions and corresponding quality, then, when the process conditions are to be known to the quality, only the linear relationship is needed to be solved, and without going through finite element analysis, the accuracy of the method depends on correctness of parameters of used materials, so that material measurement is still needed.
Literature "tan anping, lujing. unmodflow-based uncims material shrinkage optimization analysis. 10.19491/j.issn.1001-9278.2019.08.009 ", for material models not disclosed by the finite element software, it is impossible to perform a measurement fitting to find material parameters, and therefore there is no direct mass prediction-volume shrinkage comparison, and only the closest other mass results, such as product size change, can be found except for the mass result item. In addition, because the actual dimensional deformation of the product and the dimensional deformation predicted by the finite element cannot be ensured due to the lack of accurate parameters due to the incapability of measurement, the correlation between the actual dimensional deformation of the product and the dimensional deformation predicted by the finite element can be found by repeated experiments to prove that the properties of the used material can be used, but the first mold opening failure in the comparison process can only ensure the correctness of mold opening again, and the finite element prediction cannot play a role before production.
Int J Mater Form (2010) vol.3suppl 1: 37-40 Cellere discloses a quality result of a series of plastic part buckling deformation obtained by an experimental design method aiming at a residual stress modification material model and parameters thereof which are not disclosed by a finite element software, and by means of a neural network analysis method, the quality result of actual production quality is compared with a quality result predicted by finite element software using assumed material model parameters, and the residual stress modification material model parameters are reversely pushed.
In addition, the injection molding finite element simulation calculation technology was developed in the 1970 s, because of the limitation of the computer computing capability at the moment, the three-dimensional mold structure needs to be simplified into two-dimensional analysis, because many three-dimensional plastic physical characteristics and product quality cannot be analyzed and reproduced in two-dimensional simplification, a plurality of phenomenological descriptions which need to utilize actual mold testing are generated in complex behaviors in the mold cavity, and the phenomenological two-dimensional model parameters are insufficient in physical significance, the model is still undisclosed in software, the measurement method and parameter fitting are not completely disclosed, and finally, a user cannot obtain parameters by himself, measurement needs to be performed through a software supplier, and the software supplier obtains benefits in a business model accumulated in 40 years, but the software purchasing and the payment measurement are not equal.
Therefore, the present inventors have aimed to invent a method for optimizing the parameters of physical properties of plastics by finite element simulation, aiming at the above technical problems.
Disclosure of Invention
To overcome the above disadvantages, the present invention aims to provide a method for optimizing parameters of physical properties of plastics by finite element simulation.
In order to achieve the above purposes, the invention adopts the technical scheme that: a method for optimizing parameters of physical properties of plastics by finite element simulation, comprising the steps of:
s1, judging the material property, judging whether the material belongs to the new material which is not measured or the material which is known to be partially measured, if the material belongs to the new material which is not measured, selecting S2, and if the material belongs to the material which is known to be partially measured, selecting S3;
s2, for the new material without measurement, determining what the basic properties of the material unrelated to the finite element should be compared according to the requirement of the required product quality result;
s21, according to the relevance between the basic material properties irrelevant to the finite elements and the physical properties relevant to the finite elements, disclosing a database in the finite element software to search for proper plastics and obtaining the physical properties of the materials relevant to the finite elements;
s3, for the material with known partial property measurement, according to the requirement of the required product quality result and the measured partial finite element related material physical property, through the relationship between the partial physical property and the finite element related material physical property, disclosing the database in the finite element software to find the proper plastic and obtaining the material physical property related to the finite element;
and S4, searching the model and the database thereof in the finite element software according to the physical properties of the material obtained by the two methods S2 or S3, and substituting the model and the database thereof into finite element analysis to obtain a product quality result if the model and the database are complete.
Preferably, if the model obtained in S4 and the database thereof are not complete, a correlation test between the physical properties of the material and the product quality results is performed, and the correlation test includes the following steps:
s41, producing sample strips by using the standard test mould, and measuring the real product quality result items;
s42, substituting the incomplete model and the database thereof, and the residual parameters deduced by the incomplete model and the database through the public database in the finite element software into the finite element analysis to obtain the estimated product quality result;
and S43, comparing the difference between the real product quality result item and the estimated product quality result, and substituting finite element analysis to obtain the product quality result if the difference is within the set acceptable range.
Preferably, if the difference of S43 is not within the acceptable range, the public database searching method in the finite element software is changed, the model and its database are retrieved, and the correlation test alignment is repeated again until the difference value is within the acceptable range.
The method for optimizing the parameters of the plastic physical properties by using the finite element simulation has the advantages that by adopting the method, the problem that the analysis result is wrong and further the loss caused by re-opening the die is caused due to wrong substitute materials with different use properties can be avoided, the test time is short, the cost is reduced, and meanwhile, the accuracy of the analysis result is improved.
Drawings
FIG. 1 is a flow chart of a method for optimizing parameters of physical properties of plastics using finite element modeling.
FIG. 2 is a graph showing the correlation between A6 in the residual stress correction model parameters and the vertical shrinkage value in the mold.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will make the advantages and features of the invention easier to understand by those skilled in the art, and thus will clearly and clearly define the scope of the invention.
Referring to fig. 1, in the present embodiment, a method for optimizing parameters of physical properties of plastics by using finite element simulation includes the following steps:
s1, judging the material property, judging whether the material belongs to the new material which is not measured or the material which is known to be partially measured, if the material belongs to the new material which is not measured, selecting S2, and if the material belongs to the material which is known to be partially measured, selecting S3;
s2, for the new material without measurement, determining what the basic properties of the material unrelated to the finite element should be compared according to the requirement of the required product quality result;
s21, according to the relevance between the basic material properties irrelevant to the finite elements and the physical properties relevant to the finite elements, disclosing a database in the finite element software to search for proper plastics and obtaining the physical properties of the materials relevant to the finite elements; the basic material properties are related to the physical properties of the finite elements, because the same basic properties, including the similar molecular structure of plastics such as type, density, etc., the viscosity properties related to the movement of plastic molecular chains and the volume shrinkage properties related to the free volume caused by the structural shape change of the plastic molecular chains due to the temperature rise should also be similar.
S3, for the material with known partial property measurement, according to the requirement of the required product quality result and the measured partial finite element related material physical property, through the relationship between the partial physical property and the finite element related material physical property, disclosing the database in the finite element software to find the proper plastic and obtaining the material physical property related to the finite element;
and S4, searching the model and the database thereof in the finite element software according to the physical properties of the material obtained by the two methods S2 or S3, and substituting the model and the database thereof into finite element analysis to obtain a product quality result if the model and the database are complete.
If the model and the database obtained in S4 are not complete, a correlation test between the physical properties of the material and the product quality results is performed, and the correlation test includes the following steps:
s41, producing sample strips by using the standard test mould, and measuring the real product quality result items;
s42, substituting the incomplete model and the database thereof, and the residual parameters deduced by the incomplete model and the database through the public database in the finite element software into the finite element analysis to obtain the estimated product quality result;
and S43, comparing the difference between the real product quality result item and the estimated product quality result, and substituting finite element analysis to obtain the product quality result if the difference is within the set acceptable range.
If the difference of S43 is not within the acceptable range, the public database searching method in the finite element software is changed, the model and its database are retrieved, and the correlation test comparison is repeated again until the difference value is within the acceptable range.
By adopting the method, the analysis result error caused by wrong use of the substitute materials with different properties and further the loss caused by the need of mold opening again can be avoided, the test time is short, the cost is reduced, and the accuracy of the analysis result is improved.
The preferred embodiment of the method is applied by combining the method as follows:
the aim of this example was to find the Residual Stress modification (CRIMS) parameter for a polypropylene material without filler.
Figure BDA0002855204040000061
This is a list of properties of the examples.
(1) Because the purpose of finite element simulation is to predict the dimensional change of a product caused by shrinkage during forming, the residual stress correction model parameters related to the dimensional quality result item of the polypropylene material need to be obtained;
(2) the same material types are found in the finite element software database in sequence: and the density is similar to that of polypropylene: 0.92 plus or minus 0.02g/cc, the filler content is 0, and the melting index value is 12 plus or minus 6, which is used as the data base for the residual stress correction model parameters, 210 materials meeting the above conditions can be found in the finite element software database;
(3) the measured physical property of the finite element most relevant to the residual stress modification model is the shrinkage of the product in the mold, so the correlation test between the physical property of the material used in the present invention and the product quality result is required, i.e. the shrinkage of the product in the mold is tested under different process conditions, and the experimental conditions and results are shown in the following table.
Figure BDA0002855204040000071
(4) Analyzing the average value of the experimental results of the shrinkage of all the materials obtained in the step (2) in the die under different process conditions and the parameter relationship of the residual stress correction model of the materials. FIG. 2 is a graph illustrating the correlation between A6 in the residual stress correction model parameters and the shrinkage value in the vertical direction of the mold and the linear regression equation thereof.
(5) An optimal relation formula capable of describing six parameters in the residual stress correction model and shrinkage values (vertical and flowing) in two directions in the mold is obtained by using a mode of including a Convolutional Neural network (Convolutional Neural Networks) or a Multivariate Adaptive Regression (Multivariate Adaptive Regression) and the like.
(6) Estimating a set of initial parameters of the residual stress correction model according to the relation obtained in step (5) for the shrinkage of the unknown material in the mold in both vertical and flow directions.
(7) And (4) substituting the parameters obtained in the step (6) into finite element calculation to analyze the shrinkage of the product in the mold under different process conditions, so as to obtain quality result prediction of the shrinkage in the mold under different process conditions.
(8) Comparing the prediction result of the step (7) with the real experiment result of the step (3), if the error is in an acceptable range, finishing the parameter optimization process of the residual stress correction model, if the error is not in the acceptable range, slightly adjusting the parameters, and then carrying out finite element analysis and comparison.
The advantages of the above-described method are,
1. applying to the history database: the prior art does not analyze historical databases.
2. Even if the model parameters are not disclosed, the initial value of the iterative process can be obtained: the prior art does not use the historical database induction results as the starting value for the iterative analysis.
3. The physical properties are given weights according to a relationship with the quality result for use in the iterative process: the prior art does not refer to a relationship with product quality results and therefore gives weights.
The above embodiments are merely illustrative of the technical concept and features of the present invention, and the present invention is not limited thereto, and any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of the present invention.

Claims (3)

1. A method for optimizing parameters of plastic physical properties by using finite element simulation is characterized in that: the method comprises the following steps:
s1, judging the material property, judging whether the material belongs to the new material which is not measured or the material which is known to be partially measured, if the material belongs to the new material which is not measured, selecting S2, and if the material belongs to the material which is known to be partially measured, selecting S3;
s2, for the new material without measurement, determining what the basic properties of the material unrelated to the finite element should be compared according to the requirement of the required product quality result;
s21, according to the relevance between the basic material properties irrelevant to the finite elements and the physical properties relevant to the finite elements, disclosing a database in the finite element software to search for proper plastics and obtaining the physical properties of the materials relevant to the finite elements;
s3, for the material with known partial property measurement, according to the requirement of the required product quality result and the measured partial finite element related material physical property, through the relationship between the partial physical property and the finite element related material physical property, disclosing the database in the finite element software to find the proper plastic and obtaining the material physical property related to the finite element;
and S4, searching the model and the database thereof in the finite element software according to the physical properties of the material obtained by the two methods S2 or S3, and substituting the model and the database thereof into finite element analysis to obtain a product quality result if the model and the database are complete.
2. The method of claim 1, wherein the method comprises the steps of: if the model and the database obtained in S4 are not complete, a correlation test between the physical properties of the material and the product quality results is performed, and the correlation test includes the following steps:
s41, producing sample strips by using the standard test mould, and measuring the real product quality result items;
s42, substituting the incomplete model and the database thereof, and the residual parameters deduced by the incomplete model and the database through the public database in the finite element software into the finite element analysis to obtain the estimated product quality result;
and S43, comparing the difference between the real product quality result item and the estimated product quality result, and substituting finite element analysis to obtain the product quality result if the difference is within the set acceptable range.
3. A method of parametric optimization of physical properties of plastics using finite element modeling as claimed in claim 2, wherein: if the difference of S43 is not within the acceptable range, the public database searching method in the finite element software is changed, the model and its database are retrieved, and the correlation test comparison is repeated again until the difference value is within the acceptable range.
CN202011543659.3A 2020-12-24 2020-12-24 Method for optimizing parameters of plastic physical properties by utilizing finite element simulation Pending CN113935205A (en)

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