报告人：Aleksandar Sedmak，教授 贝尔格莱德大学

邀请人：李伟

报告时间：2022年5月24日下午15:00-16：00

腾讯会议ID：337-145-620

报告人简介：是塞尔维亚贝尔格莱德大学机械工程学院教授，同时是贝尔格莱德机械工程学院创新中心负责人。2006-2009，担任贝尔格莱德大学副校长。2003-2006年，担任塞尔维亚科技发展部副部长；1999-2002年，担任美国费城Drexel大学客座教授； Sedmak教授既是欧洲的结构完整性学会副会长（ESIS），弹塑性断裂力学技术委员会（TC1）的成员和TC13联席主席，又是塞尔维亚结构力学和社会寿命（DivK）研究所的负责人。在科学研究领域，Sedmak教授在ISI库期刊上发表了100余篇论文，且在国际会议上发表了200多篇论文，内容涉及断裂力学、疲劳、结构可靠性和寿命，数值方法（有限元法），生物材料等多个领域。培养出50多个博士生，其中包括在罗马尼亚，马其顿和斯洛文尼亚的外国大学就读的学生。他也是罗马尼亚布拉索夫大学的名誉教授。

报告题目1：A scaling approach to size effect modeling of Jc CDF for 20MnMoNi55 reactor steel in transition temperature region by using Weibull function

Abstract 1：A scaling approach to size effect modeling of Jc CDF for 20MnMoNi55 reactor steelin transition temperature region by using Weibull function is presented. Ever since the 1980s there is a sustained interest in the size effect, as one of the most pronounced consequences of fracture mechanics. In the present study, the investigation of the size effect is focused on estimation of the Weibull cumulative distribution function (CDF) of the critical value of the J-integral (Jc) in the transition temperature region under constraint of a small statistical sample size. Specifically, the Jc experimental data correspond to the C(T) specimen testing of the reactor pressure-vessel steel 20MnMoNi55 at only two geometrically-similar sizes. Thus, a simple approximate scaling algorithm has been developed to tackle the effect of the C(T) specimen size on the Jc CDF under these circumstances. Due to the specific form of the two-parameter Weibull CDF, F(Jc |β,η), the scaling procedure is applied according to a two-step scheme. First, the Jc-scaling is performed to ensure the approximate overlap of the points that correspond to the CDF value F(Jc =η) = 1–1/e≈0.632 for different C(T) specimen widths (W), which assumes η·Wκ = const. Second, the F-scaling is performed to ensure the equality of the slopes of the CDF in the scaled (F·Wξ vs. Jc·Wκ) space. The objective of the sketched approach is to obtain a size-dependent Jc CDF that encapsulates a reasonably conservative data extrapolation.

报告题目2：Finite Element Method to calculate fatigue life

Abstract: Fatigue life prediction of welded joints in metallic materials is a very important topic since it covers the most frequent failure case and the most critical component of welded structures.There are a number of methods for predicting the fatigue life of metallic welded joints, starting from experimental testing in the laboratory, then using simple engineering formulas based on Paris’ law, and finally applying modern techniques of numerical simulation, such as the extended finite element method. Simple engineering formulas, based on Paris’ law, enable the analytical evaluation of fatigue life, either by direct or numerical integration. Bearing in mind the conservativity of the stress intensity factors evaluated analytically and used in these formulas, it is often necessary to apply numerical methods, such as Extended Finite Element Method (XFEM), to calculate fatigue life more precisely, especially if the geometry of a problem is a complex one. An even more important reason to apply numerical methods is the need to simulate fatigue crack growth through different zones of weld joints since they have significantly different crack growth rates, i.e., coefficients C and m, as determined by experimental testing. The differences between different zones in welded joints under fatigue loading are typically much more expressed than under static loading conditions. Therefore, XFEM is presented here, applied to the fatigue life of metallic welded joints, keeping in mind the significant differences in fatigue crack growth rates in the different zones of welded joints.