Strain rate and cold rolling dependence of tensile strength and ductility in high nitrogen nickel-free austenitic stainless steel

The tensile strength and ductility of a high nitrogen nickel-free austenitic stainless steel with solution and cold rolling treatment were investigated by performing tensile tests at different strain rates and at room temperature. The tensile tests demonstrated that this steel exhibits a significant strain rate and cold rolling dependence of the tensile strength and ductility.With the increase of the strain rate from 10~(-4)s~(-1)to 1 s~(-1), the yield strength and ultimate tensile strength increase and the uniform elongation and total elongation decrease. The analysis of the double logarithmic stress–strain curves showed that this steel exhibits a two-stage strain hardening behavior, which can be well examined and analyzed by using the Ludwigson equation. The strain hardening exponents at low and high strain regions(n_2and n_1) and the transition strain(εL) decrease with increasing strain rate and the increase of cold rolling RA. Based on the analysis results of the stress–strain curves, the transmission electron microscopy characterization of the microstructure and the scanning electron microscopy observation of the deformation surfaces, the significant strain rate and cold rolling dependence of the strength and ductility of this steel were discussed and connected with the variation in the work hardening and dislocation activity with strain rate and cold rolling.     

算術習題彙編——举錯及其他

最近,我校对了一部“算術習題汇編”,全書共有1292个題,它的內容根据循序漸進的原則,由淺入深,尤其是題文对地理,自然,和各种日常生活事物的对比,使讀者讀此書时,既加强了演算的技巧,更丰富了对地理,自然及日常生活中的各种常識,的確是一部有意义的算術補充讀物,我國現用的初中算術课本,有的內容是取材此書的,算術教師精讀此書一次,有原窺一般,今覩圣豹之樂,自修者精讀此書一次,比暗中摸索,有事半功倍之效、在此書荒——算術補充讀物——之季,初版三万册,短時間即銷售一空,这是可以想像的,但是这本書也有缺点,印刷錯誤太多,共90餘处,幾佔全書的7％以上,甚至还有演算上的錯誤,为解除讀者的疑惑,和減輕自修者的疑难,現在我將錯誤列举如下,供同志們参考。