LIU Yongning
,
ZHU Jinhua
,
ZHOU Huijiu Xi'an Jiaotong University
,
Xi'an
,
China A.Kildegaard
,
J.A.Kristensen Department of Mechanical Engineering
,
Aalborg University
,
Denmark Dept.of Materials Science and Engineering Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
The dynamic fracture toughness of a mild steel has been studied at different loading rates and temperatures.The material exhibits a transition from tough to brittle fracture with the chang- ing loading rate alone.Analysis of the fracture process by the theory of thermal activation suggests that the fracture activation energy approximates to the bond energy of the{100}of a unit cell.The toughness can be resolved into two parts,J-(fd)=J_a+J_l,where J_a is the athermal part,being independent on temperature and loading rate,while J_l=(K/K_o)~(1/n)exp(Q_f/nkT),which controls the fracture process is temperature and load- ing rate dependent.The transition of fracture mechanism caused by both temperature and loading rate is associated with the thermal movement of atoms.
关键词:
mild steel
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null
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null
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null
CHEN Huangpu DENG Zengjie Xi'an Jiaotong University
,
Xi'an
,
China CHEN Huangpu
,
Lectuer
,
Research Institute for Strength of Metals
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
The resistance to crack propagation at earlier stage for a high strength structural steel with certain ductility and its correlation to microstructures,stress states,deformation history and strain characteristics have been investigated.The resistance to crack propagation is mainly de- termined by the plastic constrain ahead of the crack tip,the elastic energy and plastic work absorbed in the stress-strain field.These are connected with the state function of triaxial stress.The deformation history and strain characteristic during deformation of material are described by the flow line in which the deformation history and strain characteristic restrain the crack initiation at stage Ⅱ and the crack propagation at stage Ⅲ.The strain hardening rate may sensitively reflect the stress distribution and micro-fracture mechanism in the interi- or of material.
关键词:
high strength structural steel
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null
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null
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CHAI Huifen RUAN Zheng FAN Quncheng (Xi'an Jiaotong University
,
Xi'an
,
China CHAI Huifen
,
associate professor
,
Department of Materials
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
The cyclic behaviours of two prestrained materials with different slip modes have been com- pared.From the analysis of hysterisis loops,it is suggested that the decrease in back stress dominates the cyclic process of Cu-Zn alloy with planar slip mode,while the decrease in frictional stress is the main factor affecting the behaviour of Cu with wavy slip mode.The re- lation between the dislocation configuration and internal stress has been also discussed.By means of the relation just mentioned,the variations of dislocation configuration before and after fatigue of the two materials,the differences in their softening mechanism and mechani- cal behaviour could be interpreted.
关键词:
slip mode
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null
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null
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ZHANG Anfeng Xinjiang Engineering College
,
Urumqi
,
ChinaXING Jiandong LU Wenhua Xi'an Jiaotong University
,
Xi'an
,
China associate professor
,
Department of Mechanical Engineering
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
The oxidation behaviour of high Cr Cast iron was investigated at 950 and 800℃ in terms of Cr content in matrix and the amount of carbide.The morphology and types of oxide films and the microstructure of subsurface were also examined.The main conclusions are:1)The original chromium content in the matrix determines the type of oxide film and it is an important factor for the oxidation resistance of high chromium cast iron;2) The oxidation resistance improves with increasing carbide content at 950℃ because of the decomposition of the carbide,while the decompsition of the carbide do not take place at 800℃ so the oxidation resisteance do not improve with increasing carbide volume.
关键词:
high chromium cast iron
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null
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null
HE Jiawen HU Naisai ZHANG Dingquan Xi'an Jiaotong University
,
Xi'an
,
China Professor
,
Research Institute for Strength of Metals
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
Residual stress concentration at a notch depends on both notch geometry and yield strength of the material.It varies through the depth,and its magnitude may be higher than the theoretical one.Compressive residual.stress concentration at the notch of shot-peened specimen of soft material is easily to he relaxed,with the surface damage during shot-peening results in a mi- nor contribution to the fatigue limit.Compressive residual stress increases the crack closure effect at the notch and may lead to a non-propagating crack.
关键词:
residual stress
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null
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null
WANG Huaming JI Jialin ** Institute of Metal Research
,
Academia Sinica
,
Shenyang.110015
,
China.*** Department of Mechanical Engineering
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China.To whom correspondence should be addressed.
材料科学技术（英）
To bring the excellent abrasion-resistant po- tential of carbide into full play,composites of cast tungsten carbide(CTC)grains based on mainly plate martensite and high Cr,W white cast iron are made on substrate of grey iron by cast-in-place hardfacing process.Results of high-stress two-body and three-body abrasion show that:(1) Base alloy microstructures have overwhelming dominating effects on abrasion resistances of the composites in two-body and especially three-body abrasion systems.(2)All composites have very ex- cellent abrasion-resistances which increase drasti- cally with the increase of CTC grain size.In case of the same CTC grain size,composite based on martensite white cast iron is much more wear-resistant than that based on mainly plate martensite although the volume fraction of CTC grains in the latter is considerably larger than that in the former.In three-body abrasion system,load has little effect on wear rate for composites based on martensite white cast iron,but wear rate of conventional wear-resistant materials increases linearly in a very steep slope as the nominal stress increases.
关键词:
abrasion
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null
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null
NI Yushan CHENG Guangxu KUANG Zhenbang Xi'an Jiaotong University
,
China doctorate student
,
Institute of Engineering Mechanics
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
Hausdorff dimension of fracture surface roughness of welded joint,both welding metal and heat-affected zone.of pressure vessel steel 16MnR,tested under strain-controlled low-cycle fatigue,was examined with computer vision srstem and by two-dimensional variation method. Results show that it decreases with the increase of cyclic hysteresis energy.The Hausdorff di- mension variation at heat-affected zone is greater than that of weld metal.It is believed that the greater the fractal dimension is,the longer the fatigue life will be.
关键词:
welded joint
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null
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null
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