| Abstract:The hydraulic press machine (HPM), which is common equipment in manufacturing applications, is widely used in many fields of the national economy. The frame structure strength design is of great importance for HPM. In this paper, Uniaxial tension and compression, pure torsion yield strength experiments for four kinds of plastic metal were carried out. Moreover, tensile and torsional strength test for one plastic metal were conducted. The stress distribution of a HPM in a variety of load conditions, displacement variation of upper beam, the change of main stress state, and the calculation results of three strength theory were studied by using ANSYS finite element software Workbench.The main research contents are as follows:(1) On the basis of the testing data of the yield strength of various types of plastic metals under tension, compression, torsion and tension-torsion combined, the relative errors calculated using common strength theory applied in the HPM are analyzed, respectively. The result shows that the errors according to limiting strain energy strength theory (LSEST) are within10%, being the minimum. The errors calculated by Mises strength theory are bigger than LSEST, and Tresca strength theory is the biggest in the three strength theory. Mises strength theory and Tresca strength theory are on the conservative side compared with the LSEST. LSEST could be used to calculate the strength under biaxial and triaxial tensile-compressive combined principal stress.(2) According to the simplified rules of finite element model and research purpose, the three-dimensional finite element model is established by using ANSYS finite element software Workbench. In addition, the key technical problems of unit selection, meshing, loading, boundary condition and contact mode are determined. Four special working conditions are selected with medium-sized load, transverse deflection, vertical deflection and slanting deflection in the HPM. Stress distribution and deformation law of the frame and column are investigated via finite element calculation.(3) Comparison of finite element calculation data reveals that principal stress state at the same position changes while frame’s working condition varies, therefore, principal stress variation should be taken into consideration in structure strength design and calculation. In the principal stress state of tension-compression, Equivalent stress of Mises strength theory is smaller or higher than that of limiting strain energy strength theory (LSEST) in some cases, results in uncertainty in strength design and hidden danger. However, in some principal stress state, the calculation results of Tresca strength theory and Mises strength theory contradicts significantly. Equivalent stress of pure tension and compression in principal stress state for Tresca’s and Mises’s are both smaller than that of LSEST’s, lead to hidden danger in some cases. The calculated equivalent stress of ANSYS finite element software does not distinguish between principal stress states, and the only Mises equivalent stress is inappropriate.(4) LSEST can be used in the structural strength design of construction machinery, e.g., HPM, with practical application value. Full total figures42, tables24, reference72... |
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