Papers by Keyword: Initial Stress

Abstract: The hole wall crushed and fractured zones length has been derived theoretically,and put forward the calculation formula of blasting crushing circle and radius of the corresponding fracture zone.Corresponding to the deep rock blasting parameters design on the basis of theoretical analysis,then lead to the reasonable parameters.These can provide certain reference design work for coal mine deep rock blasting parameters.

Abstract: Machining induced residual stress is influenced by many factors. Extensive studies on the influence of cutting parameters, tool parameters, as well as basic properties of materials have been carried out during the past decades, while another important factor, initial stress distribution in workpiece, was often ignored. In this paper a relatively complete FEM simulation on the formation mechanism of machining induced residual stress in high speed machining is carried out, illustrating the three stress zones affected by mechanical and thermal loads, and their influence on ultimate residual stress. And the influence of initial compressive stress on stress formation and cutting forces is analyzed. Initial compressive stress weakens the tensile effect caused by the shear deformation, and the residual stress tend to be more compressive with larger initial compressive stress. Cutting force becomes larger with the increase of initial compressive stress. And the results in this FEM study can be used to explain some unaccounted experimental phenomena in former researches.

Abstract: A new approach to reinforce glulam timber beams has been developed by using compressed wood (CW) which is made of a lower grade wood through densification processes. In the reinforcing practice, compressed wood blocks are inserted into pre-cut holes on the top of glulam beams to produce pre-camber and to generate initial tensile and compressive stresses on the top and the bottom extreme fibre of the glulam beam. In order to optimize the size, the number and the location of CW blocks, 3-D finite element models have been developed. 3D non-linear finite element models have been developed to simulate the pre-camber of Glulam beams locally reinforced by compressed wood blocks. The models developed have also produced the initial tensile and compressive stresses at the top and bottom extreme fibres with building-up moisture-dependent swelling on the CW blocks. With the pre-camber and the initial stress state that cancel out proportions of working deflection and stresses.

Abstract: The hot preflex cooling and compound straightening are the last two consecutive deformation processes and determine the straightness, residual stress and cross-sectional size for fabricating hundred-meter heavy rail products. The compound straightening process needs to be adjusted by the preflex cooling status. For studying the straightness, residual stress and cross-sectional size of heavy rail products, the preflex cooling model (including the residual stress) of heavy rail after cooling should be taken as straightening model for studying the compound straightening. In this paper, the results by ANSYS implicit analysis (geometry model and stress state of the cold heavy rail) is fully imported to the compound straightening by ANSYS/LS-DYNA explicit analysis through an implicit-explicit conversion method, which resolved the connection problem of coupling and analysis models for solving complex models in multi-physical fields. It is very significant for solving the similar problems in engineering.

Abstract: Based on the strain-holding test by using GDS stress path triaxial apparatus, the changes of pore water pressure and stress of soil around the pile were simulated during and after pile jacking. Test results show as follows: excess pore water pressure and effective stress increment increase with strain and initial stress rising at the stage of strain applied. And at the stage of strain holding, effective stress increment increases with rising of strain and initial stress. For the total effective stress increment, the proportion of effective stress increment is large at the stage of strain applied. And at the stage of strain holding, the proportion of effective stress increment is small.

Abstract: For frame structure, due to the uneven settlement of foundation, makes the whole framework of system with initial stress caused by uneven displacement, thus produce unfavorable influence on seismic performance of frame structure. By PMCAD modeling software and finite element module SATWE, analyse the initial stress effect on seismic performance of frame structure.Results show that under the influence of initial stress, the frame structure seismic performance declined.

Abstract: To reveal the harm of member initial stress on space frame structure, several models which are different in initial imperfection methods, material computational models and upper optimized stress ratios are employed to do nonlinear finited element analysis. It finds that the initial stress method and Marshall model are more accurate to simulate. When design the space frame structure, it must be avoided to optimize the cross section excessively in pursuit of economic factors.

Abstract: Cylindrical components produced by mecano-welding process are widely used in industries. The mecano-welding process consists of a roll bending sub-process which can produce non-closed cylinders and a welding process which can seam gaps. This paper proposes a numerical model to simulate the process and to get better understanding of the process mechanism. Explicit and implicit solvers are applied to the numerical modeling by using LS-DYNA and ANSYS software. The numerical model can provide a useful tool for design and optimization of the mecano-welding process.

Abstract: Abstract. This article based on the underground workshop region of the Shenzhen pumped storage power station, carrying on back-analysis for the initial geostress field of the region of station with method of this article, and then we can obtained the actual initial ground stress.This article based on the measured ground stress data, a 3D non-linear finite element back analysis numerical model for ground stress is set up and the landforms is simulated. This thesis has used ANSYS to do finite element calculation for rocks and soils, the corresponding sample of neural network have been gained. By setting the parameters, the neural network is optimized, then the network is trained with the optimized result. Finally, the initial ground stress field is back-analyzed with in-situ measured stress values. The result is compared with measured value, which meets the requirement for accuracy, showing the reasonabilily of the rock ground stress field obtained.

Abstract: Dynamic behaviour of a welded structure made from thin metal sheets which has a large flat surface and has been assembled together by a number of scattered spot welds is investigated. An impact hammer and roving accelerometers are used in the modal tests to provide data to update the FE model. NASTRAN Solution 103 is used to compute natural frequencies and modes of interest. The large error of the initial FE model is largely reduced mainly by adjusting a crucial parameter of the bending moment of inertia ratio, 12I/T**3.