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81.
Effect of Rare Earth Elements on Thermal Fatigue Property of Low Chromium Semi-Steel 总被引:3,自引:0,他引:3
The effect of rare earth elements on eutectic carbide‘s morphology of low chromium semi-steel in as-cast state and after heat treatment was investigated, and accordingly, the thermal fatigue property of this material was studied. The results show that RE can improve the eutectic carbide‘s morphology, inhibit the formation and propagation of thermal fatigue cracks, therefore, promote the thermal fatigue property, which is more noticeable in case of the RE modification in combination with heat treatment. The optimal thermal fatigue property can be obtained when treated with 0.2% RE modification as well as normalization at 950℃ for 3h. 相似文献
82.
LOW-CYCLE FATIGUE UNDER NON-PROPORTIONAL LOADING 总被引:4,自引:0,他引:4
X. Chen Q. Gao X.-F. Sun 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(7):839-854
A series of strain-controlled, low-cycle fatigue experiments have been conducted on 42CrMo steel under various loading paths including circular, square, cruciform, and rectangular paths. Present experiments have shown that there is additional hardening under non-proportional cyclic loading. Non-proportional cyclic additional hardening also results in a shorter life for multiaxial low cycle fatigue. A non-proportionality measure of strain path based on both a physical basis and macromechanical phenomena is proposed. The loading path effect on additional hardening is also described well. Low-cycle fatigue damage accumulation and the evolution process under non-proportional loading is analysed via the Continuum Damage Mechanics Model of Chaboche. A non-proportinality measure is introduced in the damage evolution equation and a modified Coffin-Manson type formula is derived. A novel fatigue life prediction approach based on the critical-plane concept of Brown and Miller is proposed. 相似文献
83.
将Willenborg的超载残余应力场模型与裂尖形变动力学、裂尖表面析氢反应电化学动力学以及裂尖材料内部氢的扩散动力学和热力学相结合,建立了氢脆腐蚀疲劳裂纹扩展(CFCG)超载效应的定量描述模型,给出了超载对裂尖表面析氢电化学反应及裂尖氢扩展影响的一系列判据和表达式.用上述模型进行的预测表明,对于超高强度钢,当两次超载周次之间裂纹扩展长度ad远小于超载塑性区尺寸rpOL与恒载塑性区尺寸rpCLA之差,即ad<<rpOL-rpCLA时,CFCG会发生比空气疲劳还强烈的超载迟滞效应.而当ad>rpOL-rpCLA时,可能会发生超载加速效应.这种预测在后文中由试验的宏观规律与断口特征得到充分验证. 相似文献
84.
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86.
From the corrosion fatigue test under intermit-tent wetting condition for offshore structural steelof A537 cl.l and data analysis,some results associ-ated with the role of pits in fatigue process havebeen discussed. 相似文献
87.
Chaosuan Kanchanomai Yukio Miyashita Yoshiharu Mutoh 《Journal of Electronic Materials》2002,31(5):456-465
Low-cycle fatigue (LCF) tests on as-cast Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-1Bi, and Sn-3Ag-0.5Cu-3Bi solders was carried
out using a noncontact strain-controlled system at 20°C with a constant frequency of 0.1 Hz. The addition of Cu does not significantly
affect the fatigue life of eutectic Sn-Ag solder. However, the fatigue life was significantly reduced with the addition of
Bi. The LCF behavior of all solders followed the Coffin-Manson relationship. The fatigue life of the present solders is dominated
by the fracture ductility and can be described by the ductility-modified Coffin-Manson’s relationship. Steps at the boundaries
of dendrite phases were the initiation sites for microcracks for Sn-3.5Ag, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-1Bi solders, while
for Sn-3Ag-0.5Cu-3Bi solder, cracks initiated along both the dendrite boundaries and subgrain boundaries in the dendrite phases.
The linking of these cracks and the propagation of cracks inside the specimen occurred both transgranularly through eutectic
phases and intergranularly along dendrite boundaries or subgrain boundaries. 相似文献
88.
J. Yu R. Brook I. Cole D. Morabito G. Demofonti 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(8):1019-1029
Abstract— Duplicate tests have been performed to determine the effect of cathodic protection potential on corrosion fatigue crack growth rate of a modern offshore structural steel, produced by thermo-mechanically controlled processes. The experiments were carried out using compact tension specimens exposed to artificial seawater at 10°C and subjected to constant amplitude loading at 0.35 Hz. Reproducible results showed that the merits of cathodic protection potentials are strongly dependent on stress intensity ratio R and stress intensity range Δ K . It appears that a specific value of cathodic potential may not give comprehensive protection against corrosion fatigue within the spectrum of variable amplitude loading experienced in service. Fractography showed the initiation of secondary cracks on the fracture surface to be associated with the dissolution of calcium sulphide inclusions, regardless of imposed cathodic potential. 相似文献
89.
C.Y. Tang C.P. Tsui B. Stojanovic M. Kojic 《International Journal of Mechanical Sciences》2007,49(10):1179-1191
In this study, Hill's muscle theory coupled with fatigue was proposed to describe mechanical behaviours of skeletal muscles. The force developed by a fatigued muscle was described by a muscle fatigue formula which was a time function of the activation αa and the stretch λ. The modified Hill's muscle theory was hence incorporated into a three-dimensional (3D) finite element model using the PAK finite element code. In this paper, the theoretical derivation of the 3D muscle model was firstly described. After presenting the method of establishing the finite element programme, a case example of studying the mechanical response of a frog gastrocnemius muscle was used to illustrate the applicability of the proposed methodology. The effects of the muscle fatigue on the deformation as well as the stress and strain distribution of the frog muscle subject to a cyclic activation function have been determined. An experiment capturing the real-time shape change of a frog muscle was also conducted to assess the applicability of the proposed method. A comparison between the deformed shapes of the predictive model and the frog muscles was also made. It was shown that the method is capable of providing a reasonable model for describing the mechanical behaviour of skeletal muscles. 相似文献
90.