张国栋
,
周昌玉
金属学报
基于大型有限元软件Abaqus及其用户子程序(Umat)功能,
开发了焊接残余应力与蠕变损伤耦合计算程序,
对高温用焊接接头残余应力作用下的蠕变损伤行为进行有限元模拟,
并与无焊接残余应力状态下的蠕变损伤情况 进行比较. 研究结果表明,
在炉管焊接状态下, 焊接残余应力最大值集中在焊缝和热影响区处,
并且轴向与环向 残余应力较高. 在高温环境下,
焊接接头初始态焊接残余应力较高, 虽然在短时间内应力松弛到较低的水平,
但 其蠕变损伤仍较大程度地受焊接残余应力的影响,
蠕变损伤分布与焊接残余应力的分布基本一致.
关键词:
Cr5Mo钢
,
creep damage
,
stress relaxation
陈立佳
,
吴崴
,
P.K.Liaw
金属学报
通过在816和927 ℃下进行总应变控制的不同拉伸应变保持时间的低周疲劳实验，研究了3种高温合金(HAYNES 188, HAYNES 230和HASTELLOY X)的蠕变-疲劳交互作用行为.结果表明，这3种高温合金的应变疲劳寿命主要取决于合金类型、应变保持周期及实验温度. 这些高温合金所表现出的不同应变疲劳寿命行为可归因于蠕变和氧化损伤方面的差异. 此外，应用频率修正的非弹性拉伸应变能作为损伤函数对这3种合金进行了应变疲劳寿命预测，结果显示该寿命预测方法对3种高温合金均表现出较好的寿命预测能力.
关键词:
高温合金
,
creep-fatigue interaction
,
stress relaxation
XIA Yuebo WANG Zhongguang Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China Associate Professor
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China
金属学报(英文版)
Studies of stress relaxation were carried out on commercially pure titanium.It was found that the stress relaxation behaviour relates closely to the level of deformation.The amount of re- laxed stress (?)σ_R is independent of the amplitude of stress dip in a certain range of deformation.However,it depend on the stress level at which stress relaxation begins in a cer- tain relaxation time t_R.Both back(critical)stress σ_c and flow stress σ_o vary with the strain in a similar manner.The effective stress on dislocations σ~* increases with increasing strain under low strains,but keeps constant under higher strains.
关键词:
stress relaxation
,
null
,
null
,
null
G.F. Zhou
,
M. B. Wen
,
P. H. Li and X. L. He 1) National Enterprise Technology Center
,
Wuhan Iron & Steel Group Co.
,
Wuhan 430080
,
China 2) University of Science and Technology Beijing
,
Beijing 100083
,
China
金属学报(英文版)
The stress relaxation curves of Ultra-Low Carbon Bainitic(ULCB) steels with different Cu and B contents were measured by using Gleeble-1500 dynamic thermal-mechanical simulator. The results show that Cu and B added can accelerate the strain-induced precipitation reaction, and the effect of Cu and B is even more obvious with Cu and B combined addition or Cu content increased. The TEM analysis of precipitate engendered at the temperature of 850℃ C indicate that Nb(C,N) precipitate nucleates dominantly on the dislocation line, and grows with holding time extended while the precipitate particle size increases from 5 nm to 17 nm.
关键词:
stress relaxation
,
null
,
null
Y.W.Bao
,
Y.F.Han
,
F.T.Gong
金属学报(英文版)
Stress relaxation of glass is a dualism effect, it often lead to strength degradation in strengthened glass, but on the other hand, it improves the reliability and stressuniformity of glasses. In this work, stress relaxation of soda-lime glass was investigated using three-point bending tests at 400-560℃ which is near the brittle to ductile transition temperature, for enhancing the safety of glass productions and exploring the most economic anneal process. The experimental results show that the speed of stress relaxation increases but the ultimate stress decreases with increasing temperature. The stress uniformity of the glass samples before and after anneal was examined using spherical indentation at arranged testing points. It indicates that the scatter of the local strength measured by the Hertzian indentation is smaller in the anneal glass than in initial specimen, so that the estimated Weibull modulus for the anneal specimen is higher. Furthermore, the strength evaluation by Hertzian indentation and statistical analysis was presented.
关键词:
glass
,
null
,
null
肖翔鹏
,
柳瑞清
,
陈辉明
,
易志勇
,
陈婷婷
材料导报
doi:10.11896/j.issn.1005-023X.2015.10.034
采用悬臂梁弯曲应力松弛测试方法对CuNiSiCo合金的应力松弛性能进行了测试,利用TEM探究Co对CuNiSi合金应力松弛组织的影响,并建立了应力松弛模型.结果表明,应力松弛过程可动位错密度是降低的经验公式σ*=[K'ln(t+-ao)+C]-n的模拟结果,与实验结果基本相符;合金松弛分为2个阶段,第一阶段应力松弛速率较大,由于在应力松弛的初期阶段,可动位错数量很多,位错移动的阻力比较小,位错移动的驱动力比较大;第二阶段,应力松弛速率较小,处于缓慢松弛阶段,这一阶段位错与杂质原子以及位错与第二相粒子发生交互作用,使位错增殖;Co在Cu中的固溶度较小且易于与空位结合,从而抑制了调幅分解形成所需的空位移动,致使含Co元素的Cu-Ni-Co-Si铜合金空位大量减少,抑制了可动位错的滑移;另一方面,促进了基体中析出相的析出,析出相弥散均匀地分布在合金基体中,在发生应力松弛过程中,移动的可动位错在遇到弥散分布的第二相之后,会被第二相所钉扎,故Co替代部分Ni形成的CuNiSiCo合金的应力松弛性能要优于CuNiSi合金.
关键词:
CuNiSiCo合金
,
应力松弛
,
组织
,
模型
杨香莲
,
韦春
,
吕建
,
龚永洋
,
熊雪梅
高分子材料科学与工程
分别采用碱、硅烷偶联剂(A-1120)及阻燃剂(硼砂-HCHO-NaHSO_3)对剑麻纤维进行表面处理,通过模压成型工艺制备了剑麻纤维/酚醛树脂(SF/PF)共混复合材料.采用动态力学性能测试(DMA)研究了SF表面处理方法对SF/PF共混复合材料动态力学性能、蠕变及应力松弛性能的影响,采用扫描电镜(SEM)观察了SF/PF共混复合材料冲击断面的形态.结果表明,SF经偶联剂处理后,SF/PF共混复合材料的储能模量达到6310MPa,玻璃化转变温度(T_g)达到216℃,其储能模量和T_g分别比未处理复合材料提高2倍和15℃;SF经阻燃剂处理后,SF/PF共混复合材料的蠕变和应力松弛性能得到提高,SEM观察表明,SF表面处理对提高材料的界面粘接性具有一定的作用.
关键词:
复合材料
,
动态力学性能
,
蠕变
,
应力松弛
陈超
,
陈天宁
,
王小鹏
高分子材料科学与工程
针对基于生物可降解材料聚乳酸-羟基乙酸共聚物（PLGA）的热压成型工艺仿真研究中,粘弹性材料模型参数缺乏的问题,通过单轴拉伸应力松弛试验,研究了生物可降解材料PLGA在5种温度状态下的应力松弛性能。基于时间-温度等效原理,平移得到60℃的松弛模量主曲线,并采用广义Maxwell模型对此主曲线进行拟合。结果表明：随着温度的升高,PLGA材料的松弛时间明显缩短,且拟合曲线与原数据误差较小,说明广义Maxwell模型能较理想地模拟PLGA材料的应力松弛行为。这些数据的获得为后续仿真研究提供了参考。
关键词:
应力松弛
,
聚乳酸-羟基乙酸共聚物
,
广义Maxwell模型
,
时间-温度等效原理
