Key Engineering Materials Vols. 340-341

Abstract: Because customers are requiring front-loaded washing machine to handle big capacity laundry and have faster rotation speed to increase drying ability, there are being a lot of studies for achievement of high speed dehydration, high-strength and lightweight of washing machine in the latest washing machine business. It is essential that strength of Drum Assembly which is composed of spin drum, shaft, flange is improved to attain that target. In term of spin drum, it is difficult to realize joint strength required at high speed operation because joint strength of mechanical press-joining method is low remarkably in comparison with welding. Also in case of shaft system, stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. The results of this study show optimal joining condition for mechanical press-joining by performing lots of tensile joining strength test with various specimen under multi-change of important design factor such as seaming width, bead area and bead depth etc. and the optimal design of shafting system for big capacity, high-rotation drying through strength analysis, experiment and evaluation.

Abstract: The buckling behavior of locally supported cylinders is a topic that is still the subject of many investigations. Adequate design rules have yet to be incorporated into the codes. In this contribution, the plastic buckling behavior of a stiffened cylinder on local supports is studied. Our research consists of two principal components, i.e. experiments on scale models and numerical simulations. Here the numerical simulations are discussed. Firstly the effect of the yield stress is investigated. In order to find a design rule, a large parametrical study has to be performed. In this contribution, the characteristics and the results of this study are described. The simulations show that for a radius to thickness ratio of the cylinder equal to 250, the optimal stiffener dimensions correspond with a plastic buckling phenomenon and a failure stress that is larger than the yield stress. For larger values of the ratio, the elastic instability of the stiffeners precedes the plastic buckling and this shows that the stiffener configuration is not suitable for these values of the radius to thickness ratio.

Abstract: In this paper, the formulas of elasto-plastic deformation and stresses of a multilayer pressure vessel were deduced in consideration of the linear hardening elasto-plasticity of the material, and the relations between plastic zone and interior pressure and between equivalent stress and interior pressure were obtained for a monolayer vessel. Then, treating the strength problem of a pressure vessel with a fuzzy or random one and based on the principle of the information entropy theory that the information of a variable does not change with its expressed type, the fuzzy variables in the problem were transformed into random ones or the random variables into fuzzy ones. At last, the strength reliability degree of the pressure vessel was solved out by use of the random reliability method and the fuzzy one, respectively. The relative error between the fuzzy and random reliability degrees is 4.08% and the fuzzy reliability degree is closer to the determined one than the random one.

Abstract: This paper studies the dam foundation stability of the representative no. 3 powerhouse-dam section of the Three Gorges Dam (TGD), China, using elastic-plastic finite element shear strength reduction technique. In the no. 3 powerhouse-dam section area, the low-angle discontinuities, such as joints and faults, are mostly developed in the dam foundation rock mass, and constitute deep foundation stability problems. These weak structure planes affecting the dam foundation stability are modeled as continuum bodies in the finite element modeling according to their respective spatial geometrical characteristics including inclination and dip angle. Three-dimensional elastic-plastic finite element analyses are performed to obtain the stress and deformation distributions of TGD foundation and concrete structures. The factor of safety (FOS) of TGD foundation stability against sliding and its failure mechanics are comprehensively evaluated with the following criteria: (a) The maximum of the trial factors of shear strength reduction can be reached by which the dam foundation is brought to the critical equilibrium state; (b) The inflection points of the curves of the displacements of dam heel, dam toe and dam top, vs. the trial factors of shear strength reduction are located; and (c) Plastic zones develop along the potential sliding paths consisting of the dam heel, long and large joints, and other weak structure planes as the trial factors increase. The results obtained show that the dam foundation of the no. 3 powerhouse-dam section is stable under the designed normal load combinations. The evaluations of the FOS of dam foundation stability presented may provide a significant reference for the safety assessment of TGD in the Three Gorges Project, China.

Abstract: A new differential quadrature element model is presented for the second-order elasto-plastic analysis of frames in this study. The new model is based on the differential quadrature method (DQM) and the finite-cut technique. Firstly the basic equilibrium differential equations of members, the compatibility conditions of joints and the equilibrium equations of joints for the second-order analysis of frames are established. The differential quadrature method is used to discretize the basic equations and then the stiffness equations of the whole structure can be derived. While the corresponding boundary conditions are considered, the mechanical behavior of frames can be obtained. The yielding development along the axis of the member can be taken into consideration by selecting several discrete points and simultaneously the yielding development across the section can be considered using the layered approach. The full historical second-order elasto-plastic analysis is achieved by the incremental iterative algorithm. According to the new model derived in this paper, the interrelated structural calculating program is worked out. The results of numerical examples demonstrate the validity of the differential quadrature element model (DQEM). The new model can be used in the second-order elasto-plastic analysis of arbitrary frames.

Abstract: This paper is mainly concerned with the saturated-unsaturated seepage analysis of embankment dams based on unsaturated soil theory and the reliability analysis of embankment dam based on conception of reliability. The transient seepage due to change of the water level is calculated using the finite element method based on unifying saturated-unsaturated seepage governing equations. The transient pore water pressures are then used for stability analyses of embankment dam considering the effects of suction on shear strength of unsaturated soils. Meanwhile, combined with reliability computation, the Monte-Carlo stimulation method is used to calculate the corresponding reliability index dealing with the stochastic features of soil parameters. The reliability of different water level condition of embankment dams has been analyzed. The effects of different reservoir water level drawdown and raise speeds on reliability of embankment dam are discussed.

Abstract: Pattern shift is one of the main failures of micro-electronics. In this paper, the influence of plastic deformation values of micro-structures of IC packages on the pattern shift of metal lines is studied by maximum plastic strain theory using a certain 2D FEM model with different design parameters, “d”, “w”, “t_epo”, “t_Teos”, “t_glue” “sy_glue” and “sy_al”. For different critical process step, the final process temperature is acted as a representative parameter to analyze its impact. Furthermore, Response Surface Model (RSM) of plastic strains is established using any two design parameters. Results show that “w”, “t_epo”, “t_Teos”, “t_glue” “sy_glue” and “sy_al” will have different influence on pattern shifting while “d” have little impact.

Abstract: Fick's laws were used to model the hydrogen diffusion in notched high-strength steel wires loaded in tension under elastic-plastic conditions. The plastic deformation at the notch tip has an effect on the peak distribution of the hydrostatic stress ( h σ ). So, in stress-assisted diffusion analysis, elastic-plastic material behavior should be considered. Coupled diffusion elastic-plastic finite element analysis was implemented in the finite element program ABAQUS using the user element subroutine (UEL) and the coupled temperature-displacement solver routine to solve the variational form of the diffusion equation in order to obtain the hydrogen concentration distribution ahead of the notch tip in high-strength steel wires under plane strain conditions. The analysis results are compared with those obtained from elastic analysis, which shows that, if a critical hydrogen concentration is regarded as a local fracture criterion, the elastic-plastic analysis results can be used to evaluate the hydrogen embrittlement of high-strength steel wires.

Abstract: It is difficult to determine straightening stroke precisely for automatic straightening machines. The existing calculation method of straightening stroke is based on straightening curvature equation. Because the initial curvature is obtained by curve fitting method, the method is inconvenient to use and its accuracy is not well. In this paper, a method to calculate straightening stroke based on straightening process model is put forward. So the mathematic load-deflection model of straightening process must be established at first. The straightening process model for shafts is developed according to the elastic-plastic mechanics theory. By using the model, the straightening stroke can be calculated directly according to the initial deflection of the bent part. It is advantageous to use and to decrease errors. Comparing with FEM results and experimental results, the calculation results by the model are exact and the errors are small. So the validity and the accuracy of the method are verified. It will be helpful to the development of automatic straightening machines.

Abstract: Multiple-cable single borehole anchorages are widely used in China, accepted and regarded as a very effective method for slope protection, landslide remediation and foundation ditch support. This paper presents a new method for testing tensional stresses of individual steel strands within anchor cables in single boreholes. A rig has been designed to permit testing of cables within a single borehole, including two special features: a metal plate that distributes tension between strands of a cable and a sensing device that measures the stress in each individual strand. The feasibility of the method has been demonstrated by an in situ tensional stress test on anchor cables at a landslide remediation site that successfully measured the forces on individual steel strands fastened to different anchorage segments within a borehole. The steel cable strands displayed nonlinear extension characteristics; and the length of anchorage segments and grout strength met design criteria. The results confirm that this design of anchorage is satisfactory and can provide valuable data for future design and construction.