Advances in Fracture and Failure Prevention

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Authors: Woon Tahk Sung, Hyung Taek Lim, Tae Sam Kang, Jang Gyu Lee, Young Jae Lee
Abstract: This paper presents a design and performance tests of in-plane gimbal-structured Z-axis gyroscope. The device is manufactured by conventional surface micro machining process using 15µm-thickness epitaxially grown polysilicon. The total size of the device is 4.8mm x 4.8mm in area including 1mm x 1mm core gyro structure and pads for wire bonding. It is designed as two-gimbaled structure which separates inner and outer gimbals. This leads two nearly identical modes of gyroscope, i.e. driving and sensing mode, to mechanically decoupled ones, resulting in enhanced performance. Experiments are accomplished through frequency analysis and dynamic tests using a detection circuit, a vacuum chamber and a rate table. Through experiments, it is confirmed that the designed gyroscope has 0.003 deg/sec resolution, 0.00095 deg/sec/ Hz noise equivalent density, 0.57 % FSO nonlinearity error and 0.02 deg/sec bias stability.
Authors: H.T. Lee, C.L. Yang, Ming He Chen, C.S. Li
Abstract: The effect of Sb addition on microstructure, intermetallic compound (IMC) and mechanical properties of Sn-Ag solder joints is investigated. The compositions of selected solders are Sn2.58Ag, Sn2.82Ag1.75Sb, Sn2.87Ag4.75Sb and Sn2.7Ag8.78Sb. Experimental results show that most of the added Sb are solved in -Sn matrix, and the rest react with the Ag3Sn to form Ag3(Sb,Sn) phase, which contributes to suppress the coarsening of Ag3Sn phase. SbSn phase can be observed in β-Sn matrix as the Sb addition exceeds 4.75% and remains stable during the thermal storage test. The solder microhardness increases with increasing Sb. And the growth rate of interfacial IMC layer decreases as Sb addition increases. EPMA analysis indicates there are some Sb diffusing into the interfacial IMC layer. Shear strength of solder joints are raised by adding Sb. The shear strength by as-soldered condition are 27.8MPa (0%Sb), 29MPa (1.75%Sb), 30.4MPa (4.75%Sb) and 43.4MPa (8.78%Sb) respectively
Authors: I. Jeon, Yong Bum Park, Hisahiro Inoue, Kikuo Kishimoto
Abstract: The volume-averaged hydrostatic parts of thermo-mechanical stresses in the metal interconnect line determined by XRD method and finite element method are compared with each other. Two typical shapes of passivated Al-0.5%Cu thin film with SiN or FOx(Flowable Oxide) are selected for this study. For the numerical calculation, the stress concentration effect around the edge of Al-Cu thin film and elastic-plastic behavior of the film following its hardening rule are considered. For the stress obtained by XRD, the experimental results of Park and Jeon[Microelectron. Eng., 69 (2003) p.26] are introduced. A good agreement is found between the volume-averaged hydrostatic stresses obtained from each method.
Authors: Constantin Bratianu, Paul Rinderu, Lucian Gruionu
Abstract: A 3D finite element model of a human knee was constructed to study the response of articular tissues to loads applied to the surface of the femur similar to normal and extreme movements of the joint as in sports activities. A solid model of the femoral and tibial cartilages and menisci were built from post mortem MR images of human knee at full extension using the Pro/Engineer software package. The knee kinematics data was registered for this model and successive articular surface positions were obtained as a function of flexion angle. The cartilage and menisci were modeled as nonlinear orthotropic materials and contact elements were used to compose the contact layer between articular surfaces. The model determined average contact areas and stress values, which were then compared with published experimental results for equivalent boundary conditions. The presence of menisci increased the contact area in the knee joint, thus creating lower contact stresses on the cartilage than those measured experimentally. Validation of results allows the utilization of 3D knee model for determining the contact areas and the contact stress field for diverse bones positions simulating sports activities.
Authors: Jae Kyoo Lim, Seok Yoon Han
Abstract: In order to analyze beam structures more accurately and effectively, a two-node orthotropic beam element is proposed. This beam element is formulated using a consistent higher order deformation theory of orthotropic beams of which the transverse normal deformation can be effectively estimated. The stiffness matrix and the vector of equivalent nodal forces of the beam element are derived explicitly by the Galerkin method. In order to examine the reliability and the characteristics of the beam element, the analytical and the finite element solutions of a simple cantilevered beam are compared with each other. As a result, the following conclusions are obtained; (1) the accuracy of the suggested orthotropic beam element is very excellent and so the transverse normal deformation and shear stress of an orthotropic beam can be effectively estimated. (2) It can be used for accurately analyzing the general beam structures regardless of the Euler's or the Timoshenko's beam.
Authors: Dong Yun Ge, Ming Wan Lu, Qiu Hai Lu
Abstract: The compactly supported radial basis functions (RBFs) is modified and used to the wave propagation in the anisotropic materials. An example to simulate the wave propagation in composite material is used in the paper to verify this method. In this example, stress wave propagation histories are obtained. The comparison between results by this method and by finite element method is also made. And the agreement with two results shows that this method can be used to simulate the wave propagation history in anisotropic material efficiently.
Authors: Guang Zhang, Jing Xi Chen, Dong Zi Pan
Abstract: This present paper makes preliminary discussions on the application of Numerical Manifold Method to P- version adaptive analysis and deduces the displacement functions with various orders in elements and the expression of element's stiffness matrix, and codes the program for adaptive analysis with language C. Two numerical examples are studied and their results verity that the method and programs being given on this paper are accurate.
Authors: Shui Lin Wang, Xia Ting Feng, Xiu Run Ge
Abstract: In finite element method, the order of complete polynomial of the interpolation function is related to the number of nodes in the element. This paper presents a four-node quadrilateral element with quadratic function on it. The presented displacement functions maintain C0-continuity. Meanwhile, the element stiffness matrix is derived from the displacement functions. Test problems show that high accuracy can be achieved by the use of the new displacement function on the element.
Authors: Xiang Hua Guo, Dai Ning Fang
Abstract: In this paper, the moving least-square (MLS) method, one of the most promising meshless methods, is modified to construct whole field meshless approximation for coupled electromechanical problems. Based on this method, the crack propagation behavior and the elasto-electric fields near a crack tip in a PZT-5H piezoelectric ceramic under mechanical, electrical and mechanical-electrical mixed loads are investigated. The numerical results show that for a negative applied electric field, the hoop stress will be maximum at a certain angle other than 00 when the ratio of the electric field to tensile stress is relatively high, which makes the crack turn away from its original growth path.
Authors: Chul Su Kim, Jung Kyu Kim
Abstract: In this study, the reliability analysis of the low pressure steam turbine blade was performed using the Monte Carlo simulation considering variations of applied stress and strength. Applied stress under the service condition of steady state was obtained by finite element analysis. The fatigue strength under rotating bending load was evaluated by the staircase method. The most appropriate probabilistic distribution of the fatigue strength is 3-parameter Weibull distribution, which is determined by the comparative analysis. The failure probability under various loading conditions was derived from the strength-stress interference model.

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