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This paper studies and compares the effects of pull-pull and 3-point bending cyclic loadings on the mechanical fa- tigue damage behaviors of a solder joint in a surface-mount electronic package. The comparisons are based on experimental investigations using scanning electron microscopy (SEM) in-situ technology and nonlinear finite element modeling, respec- tively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure.  相似文献   
2.
任淮辉  王习术  陈应龙  李旭东 《中国物理 B》2012,21(3):34501-034501
In this paper, the natural structures of a dragonfly wing, including the corrugation of the chordwise cross-section, the sandwich microstructure veins, and the junctions between the vein and the membrane, have been investigated with experimental observations, and the morphological parameters of these structural features are measured. The experimental result indicates that the corrugated angle among the longitudinal veins ranges from 80° to 150°, and the sandwiched microstructure vein mainly consists of chitin and protein layers. Meanwhile, different finite element models, which include models I and I* for the planar forewings, models II and II* for the corrugated forewings, and a submodel with solid veins and membranes, are created to investigate the effects of these structural features on the natural frequency/modal, the dynamical behaviors of the flapping flight, and the deformation mechanism of the forewings. The numerical results indicate that the corrugated forewing has a more reasonable natural frequency/modal, and the first order up-down flapping frequency of the corrugated wing is closer to the experimental result (about 27.00 Hz), which is significantly larger than that of the planar forewing (10.94 Hz). For the dynamical responses, the corrugated forewing has a larger torsional angle than the planar forewing, but a lower flapping angle. In addition, the sandwich microstructure veins can induce larger amplitudes of torsion deformation, because of the decreasing stiffness of the whole forewing. For the submodel of the forewing, the average stress of the chitin layer is much larger than that of the protein layer in the longitudinal veins. These simulative methods assist us to explain the flapping flight mechanism of the dragonfly and to design a micro aerial vehicle by automatically adjusting the corrugated behavior of the wing.  相似文献   
3.
三维材料微结构设计与数值模拟   总被引:2,自引:0,他引:2       下载免费PDF全文
任淮辉  李旭东 《物理学报》2009,58(6):4041-4052
为了研究材料细观尺度的力学性能与失效行为,达到对材料微结构的“性能导向型”设计与性能预测的目的,通过程序设计结合有限元数值模拟的方法实现多元多相异质体材料微观组织结构的计算机仿真、材料微结构的细观力学计算与虚拟失效分析.以材料微观组织结构计算机仿真软件ProDesign构造的多晶体材料与多晶体基复合材料微结构的代表性体积单元为基础,基于对商业有限元软件ABAQUS的二次开发,实现对材料微结构细观力学的数值计算,并根据数值模拟结果预测微结构的材料性能,识别“材料结构弱点”,评估异质体材料微结构内微裂纹的启裂 关键词: 材料微结构 数值模拟 各向异性 虚拟失效  相似文献   
4.
<正>High density packaging is developing toward miniaturization and integration,which causes many difficulties in designing,manufacturing,and reliability testing.Package-on-Package(PoP) is a promising three-dimensional highdensity packaging method that integrates a chip scale package(CSP) in the top package and a fine-pitch ball grid array (FBGA) in the bottom package.In this paper,in-situ scanning electron microscopy(SEM) observation is carried out to detect the deformation and damage of the PoP structure under three-point bending loading.The results indicate that the cracks occur in the die of the top package,then cause the crack deflection and bridging in the die attaching layer.Furthermore,the mechanical principles are used to analyse the cracking process of the PoP structure based on the multi-layer laminating hypothesis and the theoretical analysis results are found to be in good agreement with the experimental results.  相似文献   
5.
In this paper,the natural structures of a dragonfly wing,including the corrugation of the chordwise cross-section,the sandwich microstructure veins,and the junctions between the vein and the membrane,have been investigated with experimental observations,and the morphological parameters of these structural features are measured.The experimental result indicates that the corrugated angle among the longitudinal veins ranges from 80 to 150,and the sandwiched microstructure vein mainly consists of chitin and protein layers.Meanwhile,different finite element models,which include models I and I for the planar forewings,models II and II for the corrugated forewings,and a submodel with solid veins and membranes,are created to investigate the effects of these structural features on the natural frequency/modal,the dynamical behaviors of the flapping flight,and the deformation mechanism of the forewings.The numerical results indicate that the corrugated forewing has a more reasonable natural frequency/modal,and the first order up-down flapping frequency of the corrugated wing is closer to the experimental result(about 27.00 Hz),which is significantly larger than that of the planar forewing(10.94 Hz).For the dynamical responses,the corrugated forewing has a larger torsional angle than the planar forewing,but a lower flapping angle.In addition,the sandwich microstructure veins can induce larger amplitudes of torsion deformation,because of the decreasing stiffness of the whole forewing.For the submodel of the forewing,the average stress of the chitin layer is much larger than that of the protein layer in the longitudinal veins.These simulative methods assist us to explain the flapping flight mechanism of the dragonfly and to design a micro aerial vehicle by automatically adjusting the corrugated behavior of the wing.  相似文献   
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