Guozheng KANG
,
Chuan YANG
,
Jixi ZHANG
材料科学技术（英文）
Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of Al2O3 short fiber reinforced Al-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally, the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideratio of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300°C) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.
关键词:
Fracture
,
null
,
null
,
null
叶威
物理测试
本文通过研究热处理工艺对金属TiC陶瓷刀具基体3Cr13组织的影响，提出了改善组织韧性的热处理工艺。该工艺下，基体原马氏体组织中沿晶界呈网状分布有脆性碳化物被消除，获得了晶粒细小的全马氏体组织，从而极大地提高了刀具基体的韧性，有效地提高了刀具抗断裂的能力，降低了断刀率。
关键词:
TiC
,
Cutter
,
Fracture
,
Heat treatment
叶威
物理测试
本文从金相组织及断口形貌分析两个方面对切割硬质材料的某金属陶瓷刀具断裂的原因进行了分析。结果表明，刀刃部位的镍铬基金属TiC陶瓷存在严重未烧结缺陷，成为起裂源；不合理的热处理工艺造成了刀具基体3Cr13晶粒粗大，并且沿晶界呈网状分布有脆性碳化物，导致基体脆性增加，在使用过程中发生沿晶断裂。
关键词:
刀具
,
Fracture
,
failure analysis
新型炭材料
doi:10.1016/S1872-5805(11)60091-7
采用分子动力学模拟研究了单壁碳纳米管的力学特性与其长度、直径及手性的关系.在施加拉伸或压缩载荷时,不同直径的单壁碳纳米管表现出明确的力学性能变化.锯齿型和扶手椅型碳纳米管的拉伸性能与其长度无关,而对于手性碳纳米管来说则稍有变化.所有类型碳纳米管的压缩特性,主要是刚度和临界压应力均随碳纳米管长度的变化而改变.断裂模式因结构不同而异,屈服过程产生纽结、波浪状结构、柱状屈曲、弯曲和扭曲等.
关键词:
单壁碳纳米管
,
手性
,
力学性能
,
断裂
,
屈曲
苏维国
,
穆志韬
,
刘涛
,
马晓乐
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2014.02.005
金属韧性断裂是损伤累积的结果,以孔洞演化理论和细现损伤力学模型为基础,将韧性断裂机制分为拉伸型和剪切型两种类型,提出了一个适用于不同变形路径的统一形式的韧性断裂准则.通过编写用户材料子程序VUMAT,将韧性断裂准则嵌入到ABAQUS有限元软件的准静态算法主程序中,模拟了航空铝合金LY12CZ(Kt=1和3)单向拉伸时材料损伤累积、裂纹萌生、扩展直至韧性断裂的物理全过程,并通过拉伸试验验证了模型的有效性.韧性金属材料孔洞断裂机制研究表明,单调加载过程中宏观裂纹的形成是孔洞在夹杂物和第二相微粒周围形核、长大直至聚合的结果.
关键词:
韧性金属材料
,
断裂
,
损伤累积
,
有限元分析
Zhongbing LUO
金属学报(英文版)
The tensile behavior of Sn-0.7Cu and Sn-0.7Cu-1Zn was compared at various deformation temperatures. Refined microstructure and γ-CuZn particles were discovered with Zn addition. The strengths of Zn-containing solder were higher than that of Sn-0.7Cu at room and subzero temperatures. With the elevation of deformation temperature, they both decreased and they were nearly the same at 80℃. The works of fracture exhibited the similar evolution law. For Sn-0.7Cu solder, the elongation after fracture was smaller and the reduction of area was bigger than those of Sn-0.7Cu-1Zn. This shows that Zn addition improved the deformation stability, which is attributed to the modification of the microstructure. Dimples in fracture surface became smaller and shallower with the decreasing temperature. Ductile fracture was discovered in all the samples.
关键词:
Sn-0.7Cu
E.Bayraktar
,
F.Montembault
,
C.Bathias
材料科学技术（英文）
The study of microstructural network and damage mechanism of polymer and rubber, although deceptively simple, involves a complex interplay between material properties and service conditions. So, the study of the texture, deformation and the failure of rubber specimens are of considerable practical interest. In fact, the occurrence of defects such as the initiation and the growth of cavitations in rubber specimens in working conditions is an important problem. These deal with the improvement of microstructure (for delaying instability) in order to obtain a higher service capacity. The scope of the present paper is, therefore, to evaluate principal mechanisms, in-situ observation of damage at mesoscopic, microscopic and macroscopic levels by using X-ray computed tomography (CT) installed in the ITMA research centre for confirming the behaviour of natural rubber (NR) and styrene butyl rubber (SBR) specimens used in automotive and aeronautical fields.
关键词:
X-ray computed tomography
,
null
,
null
,
null
Gang FANG
,
Pan ZENG
材料科学技术（英文）
Based on rigid-plastic finite element method, a skew rolling process of stepped part is simulated. Considering nodesaving and effective remeshing, the tetrahedron solid elements are used to discrete workpiece. The workpiece material adopts rigid-plastic model, where the flow stress is function of effective strain, effective strain rate and temperature. The thermomechanical coupling is considered in the simulation. To model the spinning workpiece undergoing plastic deformation, a novel solution is presented and applied in this paper. The stress state in the workpiece and forming characteristic of skew rolling are analyzed. The forming load, including roller torque and forces in three directions are predicted. The above analyses are helpful to understanding of forming mechanisms and improving of process and die design.
关键词:
FEM
,
null
,
null
,
null
,
null
