Key Engineering Materials Vols. 462-463

Abstract: Corrosion simulation of rebar in concrete structures using BEM 3D have been developed. However, pre processing procedure such as geometry development and meshing is still performed manually. In addition, the visualization of BEM simulation results is still illustrated using the simple chart and graph. Nowadays, many softwares have been developed under open source platform that can be used freely. There is open source softwares for CAE purposes such as Salome and VisIt. The aim of this study is to implement the open source software as pre- and post-processing for the developed BEM 3D code in order to simulate corrosion of reinforced concrete. Salome 2.3.9 is used for developing geometry and meshing the model. The visualization of the simulation results are conducted using VisIt 1.8. The study shows that the open source software i.e. Salome and VisIt, perform well as pre and post processing of developed code for simulating the corrosion of reinforced concrete. It shows that the meshing procedure and the interpretation of results become simpler and easier.

Abstract: This paper presents a methodology to determine the durability of Quad Flat No-Lead (QFN) package. The QFN package is useful for improving the reliability of the package. A mechanical fatigue test namely three points bending cyclic test and signal analysis were proposed in this paper. The three points bending cyclic test method is a test assembly that supports a specimen on two anvils or rollers, and symmetrically loads the specimen on the opposite surface with an anvil or roller using micro-tester machine. For strain signal collection, a strain gauge was connected to the dynamic data acquisition system, and it was used for each tested QFN package for determining the response of the captured cyclic strain signal. It was found that the sinusoidal amplitude pattern of signal response has been obtained during the constant three points bending cyclic test. The obtained response signals were then analysed using the Power Spectral Density.

Abstract: Conventional buildings are mainly designed based on elastic analysis of structures subjected to moderate earthquakes. In this case, the seismic forces are much smaller than the forces introduced by strong ground motions with the considered structural behavior going to nonlinear response during these severe earthquakes. Improving the earthquake resistance of reinforced concrete buildings using a variety of earthquake energy dissipation systems has received considerable attention in recent years by civil engineers. In the present study, a nonlinear computational scheme was developed to predict the complete nonlinear dynamic response of reinforced concrete framed buildings equipped with viscous damper device subjected to earthquake excitation. A finite element program code is developed based on the nonlinear analysis procedure of reinforced concrete buildings equipped with viscous damper devices and a two dimensional, five story models of RC buildings subjected to earthquake were analyzed. Result of nonlinear analysis of RC buildings which furnished by viscous dampers indicated that using of viscous dampers effectively reduced the damages occurring in the building and structural motion during severe earthquakes.

Abstract: Sn-Ag-Cu-Ni-Ge solder alloy has been developed to improve the mechanical properties of the Sn-Ag-Cu base solders and prevent oxidation of those solders. In this paper, an interfacial reaction and microstructure between the solder and a Cu electrode were investigated under heat exposure conditions. It was found that intermetallic compounds growth at the interface of the solder and the Cu electrode was greatly affected by amounts of added elements. Adding Ni in the solder can suppress the formation and growth of intermetallic compounds (IMCs) such as Cu-Sn and decreasing the amount of adding Ag in the solder can prevent the formation and growth of Ag3Sn. Moreover, it was found that there was an effect of suppress the growth of the Cu3Sn formed on the interface of Cu and (Cu,Ni)6Sn5 by adding Ni from analysis results of EDX and TEM.

Abstract: When HMA (hot mixture asphalt) is used to remedy functional or structural deficiencies of existing JPCP (joint plain concrete pavement), reflection cracking is a major distress mode in HMA overlay. The basic mechanism of reflection cracking is the propagation of cracks through the overlay due to deflection difference in the joints vicinity of the existing pavements. In this paper the model of JPCP is created by three finite element method and the relationship between joint deflection difference and effects such as base modulus, elastic coefficient of spring elements is discussed. Based on the model of JPCP, the finite element model of asphalt overlay is created then and shear stress concentration phenomenon is found at the bottom of HMA where is just above the joint of JPCP. So, the rule of the shear stress at the bottom of HMA with deflection difference at the joint of JPCP is studied.

Abstract: The procedure of beam subjected to transverse impact by bar is simulated using numerical method. The method considers the propagation of the expansion wave and shear wave in beam. The effect of beam height on elastic impact loads with different bar lengths and beam heights are investigated. With condition that the length of beam is longer than or equal to that of bar, the numerical solution shows that: when the bar length is constant, if the length of bar is shorter than the height of beam, the longer the bar, the bigger the peak value of impact force; the impact load curve consists of ascending and descending part basically; When the bar length is longer than or equal to beam height, the peak value of impact force is not related to the bar length and equal to that of bar with the same length as the beam height; the impact load curve is trapezium. The contact time is proportional to bar length and equal to the duration time of stress wave propagation in the bar for once return. If the bar length is constant, when bar length is shorter than beam height, the impact load is not related to beam height; when bar length longer than or equal to beam height, the peak value of impact force increases along with the beam height and approach to that of bar with the same length as the beam height.

Abstract: The performance of the casing-plug joint, including load carrying capacity, stiffness, failure modes, and its influence factors of the casing tubes set inside and outside of the main tubes are analyzed by simulating square steel tube casing-plug joints structures with ANSYS software in this paper. The formulas of the optimum l/L for the joints with the size of the main tube cross-section 200mm× 200mm are given in this paper.

Abstract: The out-of-plane secondary bifurcation buckling load-displacement equilibrium paths of the elastic circle pipe arch with and without out-of-plane brace at the top of the arch are traced using a new numerical tracing strategy. The out-of-plane secondary bifurcation buckling loads of the arch with the same sections and different rise-span ratios are obtained under the concentrated load at the top of the arch and the full span uniformly distributed load, which are compared with out-of-plane linear buckling load and in-plane primary buckling load. The calculation results show: for the same section circle pipe arches without the out-of-plane brace and under the concentrated load at the top the arch, the out-of-plane secondary buckling load is always less than the in-plane primary buckling load and the out-of-plane buckling will occur before the in-plane primary buckling. The out-of-plane secondary bifurcation buckling load of the arch with 0.2 rise-span ratio is the biggest. The bigger the rise-span ratio is, the bigger the difference between out-of-plane and in-plane buckling load. When the arch is subjected to full span uniformly distributed load, the out-of-plane buckling will also occur before the in-plane primary buckling and the out-of-plane secondary bifurcation buckling load of the arch with 0.4 rise-span ratio is the biggest. The difference between out-of-plane and in-plane buckling load of the arch with 0.2 rise-span ratio is the biggest. For the circle pipe arch with the out-of-plane brace at the top of the arch, the out-of-plane buckling load of the arch with 0.4 rise-span ratio is the biggest under the two load conditions. The brace can raise the out-of-plane buckling load significantly especially for the arch with big rise-span ratio and under full span load. The out-of-plane buckling will occur before the in-plane primary buckling when the arch is under full span uniformly distributed load. The out-of-plane buckling will occur before the in-plane primary buckling only when the arch is under concentrated load and the rise-span ratio of the arch is less than 0.3. No matter there is or not brace for the arch, the ultimate load carry capacity of the arches increase a little bit after the out-of-plane secondary buckling occurs.

Abstract: By employing the Stroh formalism for two-dimensional anisotropic thermoelasticity, fracture analyses of interface corners between two dissimilar anisotropic elastic materials under thermal loadings are considered in this paper. It was proved that the consideration of thermal effects will not influence the stress singularity but will induce heat flux singularity if the singularity of the temperature field is not permissible. To calculate the stress intensity factors via path independent H-integral, it was found that the one proposed previously for the mechanical loading conditions should be modified by adding an additional surface integral accounting for the thermal effects. Two examples considering cracks and corners in isotropic plates are presented to show the correctness and validity of the modified H-integral.

Abstract: Path-independent stress based forming limit diagrams for anisotropic materials along with the Hill 48 yield function; power law strain hardening and isotropic hardening are derived. Bifurcation analyses via solving equilibrium equations of a pointed vertex on subsequent yield loci are utilized. The presented practical forming limit diagrams (FLSDs) show more acceptable agreements with experimental data compared with those obtained by other methods. A typical neck detection macro in APDL is developed by FEA simulation for a free bulge tube hydroforming to confirm the significant simplicity and straightforwardness of the mentioned FLSD.