A COMPARATIVE-STUDY OF THE ELBOW JOINTS IN 5 SPECIES OF CHINESE MACAQUES

In this paper, we report the findings of a comparative study of the elbow joints of five species of macaque that inhabit China: Macaca assamensis, M. arctoides, M. mulatta, M. thibetana and M. nemestrina. Results of multivariate analyses of size-related variables and indices of the elbow joint suggested that the breadths of the ventral aspect of the trochlea and of the medial epicondyle of the humerus as well as indices describing the head of the radius are important factors for discriminating these species. The elbow joint of M. arctoides was most similar to that of M. thibetana, no doubt reflecting recency of common ancestry and similarity in terrestrial locomotion. The structures of the elbow joints in M. nemestrina and assamensis seemed more adapted to arboreal quadrupedalism. The elbow joint of M. mulatta, however, appears intermediate between the most terrestrial and the most arboreal forms.

Corrosion fatigue of welded joints of steel for marine platform

Experiments on the corrosion fatigue behaviour of welded joints of the steel for marine platform in air and seawater, and of the joints in seawater with cathodic protection, yielded data for linear regression to obtain fatigue life curves (Delta S-N-f). The laws of corrosion fatigue in welded joints of test steel are discussed with reference to those of A(587) and A(131) steel. In these experiments, the fatigue damage occurring at all welded joints around the weld interface resulted in the cracks and fractures. The fatigue life of the specimens in seawater with cathodic protection is longer than that in seawater Without protection.

Effect of Rock Mass Structure and Block Size on the Slope Stability-Physical Modeling and Discrete Element Simulation

This paper studies the stability of jointed rock slopes by using our improved three-dimensional discrete element methods (DEM) and physical modeling. Results show that the DEM can simulate all failure modes of rock slopes with different joint configurations. The stress in each rock block is not homogeneous and blocks rotate in failure development. Failure modes depend on the configuration of joints. Toppling failure is observed for the slope with straight joints and sliding failure is observed for the slope with staged joints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considering the joints in rock masses, the LEM predicts much higher factor of safety than physical modeling and DEM. The failure mode and factor of safety predicted by the DEM are in good agreement with laboratory tests for any jointed rock slope.

计及轴向压力的方管节点塑性铰线模型

塑性铰线分析模型已成功用于估计由弦杆表面屈服控制的各种管节点的强度；然而弦杆自身的轴向压力对节点承载力的影响仍然是用一个经验折减系数来考虑的．为了计算在轴向压力作用下沿倾斜塑性铰线的极限弯矩，研究者们提出了各种理论模型．该文对这些模型进行了分析和对比．结果表明，采用简化假设的阶梯形塑性铰线模型用于评价T形方管市点的慢度与试验结果和有限元计算结果符合得最好．

Determination Ofinterfacial Mechanical Parameters For An Al/Epoxy/Al2O3 System Byusing Peel Test Simulations

Peel test measurements and simulations of the interfacial mechanical parameters for the Al/Epoxy/Al2O3 system are performed in the present investigation. A series of Al film thicknesses between 20 and 250 microns and three peel angles of 90, 135 and 180 degrees are considered. Two types of epoxy adhesives are adopted to obtain both strong and weak interface adhesions. A finite element model with cohesive zone elements is used to identify the interfacial parameters and simulate the peel test process. By simulating and recording normal stress near the crack tip, the separation strength is obtained. Furthermore, the cohesive energy is identified by comparing the simulated steady-state peel force and the experimental result. It is found from the research that both the cohesive energy and the separation strength can be taken as the intrinsic interfacial parameters which are dependent on the thickness of the adhesive layer and independent of the film thickness and peel angle.

Inverse Analysis Determining Interfacial Properties Between Metal Film And Ceramic Substrate With An Adhesive Layer

In the present study, peel tests and inverse analysis were performed to determine the interfacial mechanical parameters for the metal film/ceramic system with an epoxy interface layer between film and ceramic. Al films with a series of thicknesses between 20 and 250 mu m and three peel angles of 90 degrees, 135 degrees and 180 degrees were considered. A finite element model with the cohesive zone elements was used to simulate the peeling process. The finite element results were taken as the training data of a neural network in the inverse analysis. The interfacial cohesive energy and the separation strength can be determined based on the inverse analysis and peel experimental result.

Analysis of critical excavation depth for a jointed rock slope using a face-to-face discrete element method

The critical excavation depth of a jointed rock slope is an important problem in rock engineering. This paper studies the critical excavation depth for two idealized jointed rock slopes by employing a face-to-face discrete element method (DEM). The DEM is based on the discontinuity analysis which can consider anisotropic and discontinuous deformations due to joints and their orientations. It uses four lump-points at each surface of rock blocks to describe their interactions. The relationship between the critical excavation depth D-s and the natural slope angle alpha, the joint inclination angle theta as well as the strength parameters of the joints c(r) ,phi(r) is analyzed, and the critical excavation depth obtained with this DEM and the limit equilibrium method (LEM) is compared. Furthermore, effects of joints on the failure modes are compared between DEM simulations and experimental observations. It is found that the DEM predicts a lower critical excavation depth than the LEM if the joint structures in the rock mass are not ignored.

Dissimilar autogenous full penetration welding of superalloy K418 and 42CrMo steel by a high power CWNd : YAG laser

Experiments of autogenous laser full penetration welding between dissimilar cast Ni-based superalloy K418 and alloy steel 42CrMo flat plates with 3.5 mm thickness were conducted using a 3 kW continuous wave (CW) Nd:YAG laser. The influences of laser welding velocity, flow rate of side-blow shielding gas, defocusing distance were investigated. Microstructure of the welded seam was characterized by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Mechanical properties of the welded seam were evaluated by microhardness and tensile strength testing. Results show that high quality full penetration laser-welded joint can be obtained by optimizing the welding velocity, flow rate of shielding gas and defocusing distance. The laser-welded seam have non-equilibrium solidified microstructures consisting of gamma-FeCr0.29Ni0.16C0.06 austenite solid solution dendrites as the dominant and very small amount of super-fine dispersed Ni3Al gamma' phase and Laves particles as well as MC needle-like carbides distributed in the interdendritic regions. Although the microhardness of the laser-welded seam was lower than that of the base metal, the strength of the joint was equal to that of the base metal and the fracture mechanism showed fine ductility. (c) 2007 Elsevier B.V. All rights reserved.

Determination of interface properties between micron-thick metal film and ceramic substrate using peel test

Peel test measurements have been performed to estimate both the interface toughness and the separation strength between copper thin film and Al2O3 substrate with film thicknesses ranging between 1 and 15 mu m. An inverse analysis based on the artificial neural network method is adopted to determine the interface parameters. The interface parameters are characterized by the cohesive zone (CZ) model. The results of finite element simulations based on the strain gradient plasticity theory are used to train the artificial neural network. Using both the trained neural network and the experimental measurements for one test result, both the interface toughness and the separation strength are determined. Finally, the finite element predictions adopting the determined interface parameters are performed for the other film thickness cases, and are in agreement with the experimental results.

Microstructures of explosively consolidated rapidly solidified aluminum and Al-Li alloy powders

The microstructures and the characteristics of water-atomized, nitrogen gas-atomized Al powders and ultrasonic argon gas-atomized Al-Li alloy powder were investigated by means of metallography, SEM, Auger electron spectroscopy and X-ray diffraction techniques. Rapidly solidified powders were explosively consolidated into different sized cylinders under various explosive parameters. The explosively consolidated compacts have been tested and analysed for density microhardness, retention of rapidly solidified microstructures, interparticle bonding, fractography and lattice distortion. It is shown that the explosive consolidation technique is an effective method for compacting rapidly solidified powders. The characteristics of surface layers play a very important role in determining the effectiveness of the joints sintered, and the Al-Li alloy explosive compacts present an abnormal softening appearance compared to the original powder.

BONDING OF ALUMINA AND METAL USING BULK METALLIC GLASS FORMING ALLOY

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al2O3 ceramic using Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

电子封装中的不流动芯下材料力学性能和封装可靠性的研究

可控坍塌芯片互连（C4）技术可以实现高速、高密度、小外形的封装，因此日渐得到关注和发展。本文针对发展新一代c4技术所面临的不流动芯下材料的机械性能问题，采用具有不同填充颗粒含量的不流动芯下材料，通过对材料的机械性能的测试和分析以及有限元模拟，初步揭示了不流动芯下材料变形行为的特点，填充颗粒含量对芯下材料机械性能的影响，以及芯下材料机械性能和芯下材料工艺导致的颗粒沉积对封装可靠性的影响。首先在差示扫描量热仪（DSC）、热一力学分析仪（TMA）上对材料的固条件、热膨胀系数、玻璃化转变温度进行了测试，接着又在六轴微型试验机上对材料在不同温度和应变率下的应力一应变行为进行了测试。测试结果表明，所用材料的固化条件和玻璃化转变温度可以满足不流动芯下材料的性能要求，材料的热膨胀系数高于芯下材料理想的热膨胀系数值，材料中填充颗粒含量、温度、应变率等对材料的应力一应变行为有重要的影响。为了解芯下材料中填充颗粒含量对机械性能的影响，对不同颗粒含量材料在各测试温度和应变率下的杨氏模量、屈服强度和流动应力进行了对比和分析。结果表明，在各测试条件下，芯下材料的杨氏模量基本随着颗粒含量的增加而升高；温度较低时，材料的屈服强度随颗粒含量的增加而升高，但是，较高温度时，材料的屈服强度和流动应力随着颗粒含量的增加呈现先升高后降低再升高的变化趋势。为理解芯下材料的屈服强度和流动应力随着颗粒含量非单调变化的行为，采用广义Eshelby等效夹杂法对含颗粒试样在单轴拉伸时试样内的应力分布进行了分析，并用纳米硬度计对材料纳米尺度的性能进行了测量。应力分析的结果表明，不流动芯下材料的SiO2填充颗粒的加入会在基体里引起应力集中，应力集中系数随着颗粒含量的增加先升高后降低，试样内的应力集中有使材料屈服强度降低的趋势。纳米硬度计的测试结果表明，芯～卜材料内形成了性能介于颗粒Z基体之间的界面相，界面相的形成有使芯下材料屈服强度提高的趋势。芯下材料屈服强度随着填充颗粒含量的非单调的变化是应力集中和界面效应藕合作用的结果。温度和应变率是影响芯下材料机械性能的重要因素。为刻画温度和应变率的效应，采用Pe化yna模型描述材料的应力一应变行为。结果表明，Per叮na模型可以拟合材料应变率相关的应力一应变行为，描述不流动芯下材料应力一应变曲线的基本趋势，对材料在测试范围外的行为给出较合理的预测，并且Perzyna模型可以很方便地用于ABAQUS中，这将易于工业应用。最后，采用商用有限元程序AB AQus分析了芯下材料机械性能和芯下材料工艺导致的填充颗粒沉积对C4封装可靠性的影响。结果表明，在芯片／基板的缝隙中填入芯下材料可以显著延长可控坍塌倒装封装焊点的热疲劳寿命，提高封装可靠性，可控坍塌倒装封装焊点的热疲劳寿命随着芯下材料中填充颗粒含量的增加而增长；芯下材料中填充颗粒在C4封装基板侧的沉积将导致封装焊点的热疲劳寿命缩短，而颗粒在芯片侧的沉积则可使焊点的热疲劳寿命稍稍延长。

Determination Of Interfacial Properties Between Metal Film And Ceramic Substrate With An Adhesive Layer

Peel test measurements and inverse analysis to determine the interfacial mechanical parameters for the metal film/ceramic system are performed, considering that there exist an epoxy interface layer between film and ceramic. In the present investigation, Al films with a series of thicknesses between 20 and 250 mu m and three peel angles of 90, 135 and 180 degrees are considered. A finite element model with the cohesive zone elements is used to simulate the peel test process. The finite element results are taken as the training data of a neural network in the inverse analysis. The interfacial cohesive energy and the separation strength can be determined based on the inverse analysis and peel experimental result. (C) 2008 Elsevier Ltd. All rights reserved.

Bonding Of Alumina And Metal Using Bulk Metallic Glass Forming Alloy

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al2O3 ceramic using Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

含环路布局和运动副轴线方位特征的运动链拓扑结构描述

构造一种含环路布局、构件类型、运动副类型和运动副轴线方位信息的运动链的拓扑特征矩阵。构件的类型构成特定的环路布局,运动副的类型及其轴线的方位配置决定运动的状态特征,多副构件是联系环路间的桥梁。以运动链构成的独立环路为基础构建特征矩阵的行数,运动链的构件数目构建特征矩阵的列数;以独立环路的旋向确定构件及其排序;以代表运动副类型的符号或数字表达构件及环路间的连接关系;以同一构件上两个运动副的相对轴线方位描述运动副的方位特征。构造的运动链特征矩阵为(2l+2)×n,而单环运动链为3×n矩阵。实例表明,该特征矩阵可以描述各类运动链,与传统n×n拓扑矩阵相比,结构大大简化,而且拓扑信息量多。该矩阵特别便于由特征矩阵构造对应的机构简图,同时也为计算机辅助运动学和动力学建模提供了一种便捷途径。