Multi-parameter Analysis Method Of Material Mechanical Properties Based On Full-field Deformation Measurement

The analysis of mechanical properties of materials is of great significance to the development of materials science and the practical application of materials.The development of full-field deformation measurement technology represented by digital image correlation provides a new method for testing the mechanical properties of materials.How to make full use of the new test methods,give full play to the advantages of full-field measurement,and analyze the mechanical properties of materials more comprehensively and efficiently has become a new problem.Therefore,this thesis studies the multi-parameter analysis of material mechanical properties based on full-field deformation measurement.The research is carried out from the two perspectives.One is improving and verifying the accuracy of the full-field deformation measurement.The other is multi-parameter analysis method of the mechanical properties of the material based on the full-field deformation data.In order to fully and comprehensively analyze the accuracy of the method,it is necessary to analyze from the two aspects of precision and correctness.The precision reflects the consistency of the method,and the correctness reflects the rightness of the method.In terms of precision verification,in order to ensure the precision of the digital image correlation method,which is the most widely used full-field deformation measurement method,a digital image correlation speckle optimization method based on integer programming is proposed,and the obtained optimized speckle quality is significantly better than the random speckle,it ensures the consistency of the speckle pattern of the digital image correlation method.At the same time,this paper also gives a set of standardized measurement process of general digital image correlation method,which ensures the consistency of test operation,software algorithm and parameter selection.The precision of the digital image correlation method in displacement,strain and material mechanical properties testing was verified by repeated experiments.In terms of accuracy verification,this paper proposes a data fusion method based on camera calibration,using electronic speckle interferometry method,a nano-scale full-field measurement technology traceable to the laser wavelength,to verify the full-field accuracy of digital image correlation.Professional metrology and verification institutions were invited to measure the displacement measurement accuracy of the digital image correlation test system in the three directions of X,Y,and Z,and issued a calibration certificate.This work is the foundation of multi-parameter analysis method of material mechanical properties based on fullfield deformation measurement.The full-field deformation measurement method was used to test the mechanical properties of the negative Poisson’s ratio honeycomb structure material composed of staggered triangular elements and the bone scaffold based on fractal design.The surface of these two new porous materials is difficult to fit completely with the strain gauge,so their mechanical properties are difficult to measure by general electrical measurement methods.The digital image correlation can quickly and accurately measure mechanical properties such as Poisson’s ratio,elastic modulus,and yield strength.Through the experimental analysis of multiple mechanical performance parameters of the honeycomb structure material,the influence of each design parameter on the mechanical performance parameters of the honeycomb structure material was evaluated by combining theory,the test and the finite element simulation methods.Through the experimental measurement of the mechanical properties of the bone scaffold,combined with the finite element results,it is found that there is a good regular relationship between the porosity and the mechanical parameters such as elastic modulus and strength.According to the above test and analysis,the design parameters of such honeycomb materials and bone scaffolds can be optimized to adjust their corresponding mechanical properties and achieve a better use.In the tensile test of orthotropic composite materials,a multi-parameter analysis method of material mechanical properties based on full-field deformation measurement is introduced.In this test,combined with the finite element method updating and mechanical analysis,the display expression of the sensitivity matrix was pushed to make full use of the full-field deformation data,and a 45° off-axis tensile test was successfully performed.Four elastic mechanical properties parameters of the material were extracted from the method,and compared with the parameters extracted in the 0° positive axis stretching to verify the correctness of the method.The analytical result of this method is not sensitive to the change of the initial value.The application of this method can effectively improve the efficiency of mechanical property testing.The research of the full text starts from practical problems and ensures the accuracy of the measurement results of digital image correlation,the most widely used full-field deformation measurement method.Combined with the corresponding mathematical and mechanical methods,the full-field deformation data is used to analyze multiple mechanical properties of the material.The performance parameters make the mechanical properties test of the material more comprehensive and efficient.