Residual Stress Calculations And Measurements — Review And Assessment Of The Iiw Round Robin Results
Residual Stress Calculations And Measurements — Review And Assessment Of The Iiw Round Robin Results
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残余应力计算和测量 - Iiw 循环结果的审查和评估
DOI：
10.1007/bf03321387
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发表时间：
2012
影响因子：
2.1
通讯作者：
T. Loose
中科院分区：
文献类型：
--
作者：
H. Wohlfahrt;Thomas Nitschkepagel;K. Dilger;D. Siegele;M. Brand;J. Sakkiettibutra;T. Loose
1997年，第十委员会的一个工作组建立了一个循环计划，以评估焊接结构中残余应力和变形预测（RSDP）的可能性，并根据焊接过程的有限元模拟验证和基准预测代码。残余应力的计算已经进行了明确的材料和几何数据，焊接条件和建议使用运动硬化模型的奥氏体钢板。此外，2003年开始了第二个测量该板残余应力的方案。用X射线测量法、中子衍射法和不同种类和变化的钻孔法对三种奥氏体钢板进行了测量。虽然理论上测量结果和计算结果基本一致，但在细节上观察到了明显的差异，特别是纵向残余应力。计算表明，在焊缝和相邻的热影响区（HAZ）的初始屈服强度的顺序几乎恒定的拉伸应力。然而，测量结果显示，热影响区的应力最大值明显高于初始屈服强度。因此，额外的计算已经进行了不同的硬化模型，以调查其对残余应力的结果的影响。事实上，用各向同性硬化模型进行的计算可以相当准确地证实这些应力最大值。在进一步的详细研究中，可以表明，应力最大值的原因是由于焊接过程中的热应力在HAZ中的应变硬化。最后，基本的考虑可以解释，运动硬化模型，包括包辛格效应，不能说明这种硬化效应。文献表明，包辛格效应至少在奥氏体钢的高工作温度下不是完全有效的。总之，计算程序表明，焊接后的残余应力状态的粗略估计是可能的，没有任何特殊的区别硬化模型使用。为了获得更精确和详细的信息，所选择的硬化模型具有重要意义。
A Round Robin Programme was established by a working group of Commission X in 1997 in order to evaluate the possibilities of residual stress and distortion prediction (RSDP) in welded structures and to validate and benchmark prediction codes based on finite element simulation of the welding process. Calculations on residual tresses have been carried out on an austenitic steel plate with well-defined material and geometrical data, welding conditions and with the proposal to use the kinematic hardening model. In addition, a second programme for measurements of residual stresses in this plate has been started in 2003. Measurements have been taken on three austenitic steel plates using the X-ray measuring method as well as neutron diffraction methods and different kinds and variations of the hole drilling method. Although a rough agreement between the measured results and the calculated ones was found in principle, distinct differences have been observed in detail — especially for the longitudinal residual stresses. The calculations indicated nearly constant tensile stresses of the order of the initial yield strength in the weld seam and in the adjacent heat affected zone (HAZ). The measurements however revealed stress maxima in the HAZ with values clearly higher than the initial yield strength. Therefore additional calculations have been carried out with different hardening models in order to investigate their influence on the residual stress results. In fact, calculations performed with the isotropic hardening model could approve these stress maxima quite exactly. In further detailed investigations, it could be shown that the reason for the stress maxima is the strain hardening in the HAZ due to thermal stresses during the welding process. Finally basic considerations could explain that the kinematic hardening model, including the Bauschinger effect, cannot account for this hardening effect. Literature indicates that the Bauschinger effect is at least not fully effective at high working temperatures of austenitic steels. Altogether, the calculation programme has shown that a rough estimation of the residual stress state after welding is possible without any special distinction of the hardening model to be used. For a more precise and detailed information, the chosen hardening model is of significant relevance.