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3D mode discrete element method with the elastoplastic model

Wei HU, Feng JIN, Chong ZHANG, Jinting WANG

《结构与土木工程前沿（英文）》 2012年第6卷第1期页码 57-68 doi: 10.1007/s11709-012-0139-9

摘要： The three-dimensional mode-deformable discrete element method (3MDEM) is an extended distinct element approach under the assumptions of small strain, finite displacement, and finite rotation of blocks. The deformation of blocks is expressed by the combination of the deformation modes in 3MDEM. In this paper, the elastoplastic constitutive relationship of blocks is implemented on the 3MDEM platform to simulate the integrated process from elasticity to plasticity and finally to fracture. To overcome the shortcomings of the conventional criterion for contact fracturing, a new criterion based on plastic strain is introduced. This approach is verified by two numerical examples. Finally, a cantilever beam is simulated as a comprehensive case study, which went through elastic, elastoplastic, and discontinuous fracture stages.

关键词： mode discrete element method elastoplastic numerical method discontinuum contact

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Elastoplastic frictional contact problem study on interference fits of compressor

ZHANG Hongwu, WU Changhua, LIAO Aihua

《能源前沿（英文）》 2008年第2卷第3期页码 313-319 doi: 10.1007/s11708-008-0026-1

摘要： The FE parametric quadratic programming (PQP) method developed from the parametric variational principle (PVP) was used for the analysis of the stress distribution of the 3D elastoplastic frictional contact of an impeller-shaft sleeve-shaft. A locomotive-type turbocharger compressor with 24 blades under combined centrifugal and interference-fit loading was considered in the numerical analysis. The solution of elastoplastic frictional contact problems belongs to unspecified boundary problems where the interaction between two kinds of nonlinearities should occur. To save time in the numerical computation, a multi-substructure technique was adopted in the structural modeling. The effect of fit tolerance, wall thickness of the shaft sleeve, and rotational speed on the contact stress was discussed in detail in the numerical computation. To decrease the difficulty of the assembly process and ensure the safety of the working state, the amount of interference between the shaft sleeve and shaft by press-fitting should be controlled strictly to avoid the rapid increase of contact stress. The numerical results show that the algorithm has high accuracy and good convergence. The study can be referred to in deciding the proper fit tolerance and improving the design and manufacturing technology of compressor impellers.

关键词： computation thickness interference-fit interference unspecified

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An improved algorithm for McDowell’s analytical model of residual stress

null

《机械工程前沿（英文）》 2014年第9卷第2期页码 150-155 doi: 10.1007/s11465-014-0295-9

摘要：

The analytical model for two-dimensional elastoplastic rolling/sliding contact proposed by McDowell is an important tool for predicting residual stress in rolling/sliding processes. In application of the model, a problem of low predicting precision near the surface layer of the component is found. According to the volume-constancy of plastic deformation, an improved algorithm for McDowell’s model is proposed in order to improve its predicting accuracy of the surface residual stress. In the algorithm, a relationship between three normal stresses perpendicular to each other at any point within the component is derived, and the relationship is applied to McDowell’s model. Meanwhile, an unnecessary hypothesis proposed by McDowell can be eliminated to make the model more reasonable. The simulation results show that the surface residual stress predicted by modified method is much closer to the FEM results than the results predicted by McDowell’s model under the same simulation conditions.

关键词： residual stress McDowell’s model volume-constancy of plastic deformation FEM elastoplastic rolling/sliding contact

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Centrifuge model test on dynamic behavior of group-pile foundation with inclined piles and its numerical simulation

ZHANG Feng, OKAWA Katsunori, KIMURA Makoto

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 233-241 doi: 10.1007/s11709-008-0033-7

摘要： In this paper, dynamic behavior of a group-pile foundation with inclined piles in loose sand has been investigated with centrifuge model tests. The test results are also simulated with elastoplastic dynamic finite element method, in which, not only sectional force of piles, stress of ground, but also deformation of piles are calculated using a three-dimensional elastoplastic dynamic finite element analysis (Code name: DGPILE-3D). The numerical analyses are conducted with a full system in which a superstructure, a pile foundation and surrounding ground are considered together so that interaction between pile foundation and soils can be properly simulated because the nonlinearities of both the pile and the ground are described with suitable constitutive models. Different types of piles, vertical pile or inclined pile, are considered in order to verify the different characteristics of a group pile foundation with inclined piles. The validity of the calculation is verified by the model tests.

关键词： centrifuge Different three-dimensional elastoplastic calculation inclined