Fracture and Strength of Solids VI

Volumes 306-308

doi: 10.4028/www.scientific.net/KEM.306-308

Paper Title Page

Authors: Mamtimin Gheni, X.F. Wang, Masanori Kikuchi
Abstract: Three-dimensional finite element method (FEM) is widely used as an effective numerical simulation technique to solve the complex engineering problem. In the FEM simulation technique at first it needs to discrete the problem. However, the almost all of the engineering problem have very complicated structure and shape, so that the mesh generation also have much difficulty. Furthermore, the correct generation of mesh is one of the most significant issues that directly affect to the accuracy of the FEM simulation. Though in extensive commercial software have an excellent automatic mesh generating system, however the problem of hexahedral automatic mesh generation and its adaptation are not enough to solve for practical applications, because for the mesh generation of complex shape is very difficult and still intensive labor work by hand. In this paper we present a new method to generate an appropriate mesh using existing regular hexahedral mesh and hexahedron mesh generation technique. This technique based on the wave transmits theory with damp named Waveform Mesh Generating (WMG) method. The results shown that the complex shaped FEM discrete hexahedral mesh model generated when shape of the side apply to regular mesh side as a waveform constraint.
607
Authors: Chang Hao Park, Chong Du Cho, Chang Boo Kim, Hyeon Gyu Beom
Abstract: This study tries to analyze the torque generated in a micro-electromagnetic clutch by using FEM. For the purpose of design change and optimization of the micro-electromagnetic clutch, the torque prediction is very important. We employ a mathematical approach of the process based on electromagnetic principle. Then real material properties are substituted in the FEM model to obtain the analytical torque. For a test, the predicted torque is compared with the experimental one to discuss the rationality of torque analysis process. The analytical result agrees well with experimental data and hence explaining the validity of the mathematical process and the FEM model.
613
Authors: Jong Il Lee, Young Choi, Kwang Suck Boo, Joon Hong Park
Abstract: Hardness is most likely to mean the resistance to indentation, and to the design engineer it often means an easily measured and specified quantity which indicates something about the strength and heat treatment of the metal. Especially, Vickers hardness is one of the most widely useful methods to obtain mechanical properties of a product. Firstly, in this study, a method to estimate hardness will be presented using FE simulations of Vickers hardness tests from the viewpoint that hardness indicates resistance to plastic deformation. To verify our method, the results of the simulations for several materials such as commercial aluminum alloy and steel will be compared with those of Vickers hardness tests for the materials. Secondly in this study, hardness numbers of the several materials will be obtained as a function of hydrostatic stress. Through the results of this study, the estimation of hardness number of a specific material will be very easy to obtain and access even though the material is under a kind of hydrostatic stress state.
619
Authors: Yong Tae Park, Yoo Kyoung Whang, Joon Ki Hong, Kwang Yoo Byeon
Abstract: In a semiconductor packaging process, the warpage greatly has influenced the reliability of the package as well as the workability. The strip warpage in FBGA package result from the structure of constitutes and the thermal mismatch by the mechanical or thermal properties such as CTE (Coefficient of Thermal Expansion) and Modulus of EMC, substrate, chip and adhesive materials. Therefore, the optimization of material properties and the package structure design has been needed by the numerical analysis. EMC used as one of the package constituents has a decisive effect on the trend of warpage, and the filler content is dominant in the EMC property. In this research, firstly the effect of the filler contents is evaluated in the warpage of FBGA package and the numerical analysis is performed with the high temperature – material properties to deal with the warpage under the actual measurement value.
625
Authors: Young Jae Park, H.K. Kim, Yoon Suk Chang, Jae Boong Choi, Young Jin Kim
Abstract: A seamless analysis of complex geometry is one of greatly interesting topic. However, there are still gaps between the industrial applications and fundamental academic studies owing to time consuming modeling process. To resolve this problem, an auto mesh generation program based on grid-based approach has been developed for IT-product in the present study. At first, base mesh and skin mesh are generated using the information of entities which extracted from IGES file. Secondly the provisional core mesh with rugged boundary geometry is constructed by superimposing the skin mesh as well as the base mesh generated from the CAD model. Finally, the positions of boundary nodes are adjusted to make a qualified mesh by adapting node modification and smoothing techniques. Also, for the sake of verification of mesh quality, the hexahedral auto mesh constructed by the program is compared with the corresponding tetrahedral free mesh and hexahedral mapped mesh through static finite element analyses. Thereby, it is anticipated that the grid-based approach can be used as a promising pre-processor for integrity evaluation of various IT-products.
631
Authors: Jung Ho Hwang, Heung Seob Kim, Young Choi, Seong Beom Lee, Ki Weon Kang
Abstract: In automotive applications, a particular area of concern is the relation between thermoelastically induced hot spots and noise and vibration in brake system. The finite element methods have been extensively used for thermal analysis applied to brake components. The two-dimensional model has been extended to an annular three-dimensional disc model in order to consider more realistic braking condition. In a conventional braking analysis, the interface pressure is assumed either constant or inversely proportional to radius. However, under the dynamic braking conditions, the frictional heat generated during braking causes thermoelastic distortion that modifies the contact pressure distribution. This paper describes the thermo-elastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation under single braking and repeated braking mode.
637
Authors: Chia Lung Chang, Tzu-Jen Lin, Kenny Huang
Abstract: Nonlinear finite element analysis is performed to evaluate the reliability of the solder joint of wafer level chip scale package (WLCSP) under accelerated temperature cycling test. The solder joint is subjected to the inelastic strain that is generated during the temperature cycling test due to the thermal expansion mismatch between the various materials of the package and PCB (printed circuit board). The equivalent stress, equivalent inelastic strain, total shear strain, and hysteresis loop of the solder joint are determined in the simulation. The equivalent inelastic strain and total shear strain range of the joint are obtained as damage criterion to predict the solder fatigue. Both Coffin-Manson and Modified Coffin-Manson fatigue life prediction models are used to estimate the thermal fatigue life of WLCSP solder joints under temperature cycling test. Also, the effects of the material properties of the stress buffer layer (SBL) on the fatigue life of the solder joint are discussed.
643
Authors: Fergyanto E. Gunawan, Hiroomi Homma, Yasuhiro Kanto
Abstract: This paper proposes an application of the inverse analysis to estimate the elastic response ahead of the crack-tip of a one-point bend specimen. The difficulty of the problem lies on determination of the impulse response function that relates the elastic response to a unit applied impact force which is numerically ill-posed. Two iterative numerical regularization schemes are proposed, first is a time-domain regularization based on the conjugate-gradient method and second is a frequency-domain regularization based on an optimal filter approach. Both schemes are evaluated by using the data obtained from an impact experiment. The result shows that the estimation error is about 18.0%.
649
Authors: Yun Jae Kim, Chang Gyun Oh, Jong Sung Kim, Tae Eun Jin
Abstract: Detailed two- and three-dimensional finite element analyses are performed to develop an engineering method to estimate elastic-plastic J for cracked structures under combined primary and secondary stresses, based on the V-factor. Extensive analyses with a wide range of geometry and load combination are considered. The results suggest important factors affecting the value of the V-factor. The most important one is the load magnitude, parameterized by the proximity of plastic yielding. The second one is the relative magnitude of the secondary stress to the primary stress. Although the effect of material, in particular materials with Lüders strain seems to be present, such an effect could be neglected, compared to those of the above two parameters. Based on the present results, an engineering method to estimate J for combined primary and secondary stress can be proposed using bilinear equations in terms of the above two parameters.
655
Authors: J. Purbolaksono, T. Dirgantara, M.H. Aliabadi
Abstract: This paper presents the geometrically nonlinear analysis of cracked plates by the dual boundary element method. Extrapolation of displacements on the crack surfaces is used to compute the stress intensity factors. The normalized stress intensity factors for the cracked square plate with fully clamped and simply supported boundary conditions are presented.
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