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Han Y.,Hefei University of Technology | Han Y.,National Technology Research Center on Pressure Vessel and Pipeline Safety Engineering | Chen X.,Hefei University of Technology | Chen X.,National Technology Research Center on Pressure Vessel and Pipeline Safety Engineering | And 3 more authors.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2012

Cold stretching technique is proposed in order to overcome the shortcomings of low yield strength of austenitic stainless steels. The key parameters for cold stretching are strain rate and strain level, their influence on material properties is analyzed. It is pointed out that excessively small strain rate will lead to occurrence of serrated yielding and plastic instability will be caused, thus the appropriate strain rate is very important for cold stretching. The strength of stretched steels can be improved significantly while its toughness still maintains a high level. Metallographic structure analysis and content of α' martensite test show that when select reasonable strain level, only a little α' martensite can be transformed but has no detrimental effect on material properties, and microstructure of pre and post cold stretched steels do not change obviously as well. The results show that the yield stress of austenitic stainless steels can be greatly increased when using cold stretching technique and other mechanical properties are not obviously influenced to guarantee safe running for pressure equipment. With this technique the weight of vessel can be lighten, which can bring remarkable economic benefit and with wide prospect of application. ©2012 Journal of Mechanical Engineering.


Dong J.,National Technology Research Center on Pressure Vessel and Pipeline Safety Engineering | Dong J.,Hefei University of Technology | Chen X.,National Technology Research Center on Pressure Vessel and Pipeline Safety Engineering | Fan Z.,National Technology Research Center on Pressure Vessel and Pipeline Safety Engineering | And 4 more authors.
Jixie Qiangdu/Journal of Mechanical Strength | Year: 2011

In order to investigate high temperature 2-step and multi-step fatigue creep life prediction method considering the load history effect, a nonlinear fatigue creep damage evolution model was presented based on the toughness exhaustion theory. The damage exponent was obtained by the high temperature 1-step stress and temperature fatigue creep test of 316L stainless steel. High temperature fatigue creep life under 2-step stress and temperature load was predicted by the damage evolution model and the failure rule under multi-step load. The predicted results were in good agreement with the experimental ones.

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