报告人：Karlicic Nikola，副教授,贝尔格莱德大学

邀请人：李伟

报告时间：2022年5月10日-2022年5月30日

腾讯会议ID：502 7594 2895

报告人简介：Nikola Karličić是塞尔维亚贝尔格莱德大学力学工程学院副教授，是生物技术这门研究生课程的负责人。他的科研方向主要包括：环境保护工程、排放控制与空气污染治理等，是欧洲一些地方市环境保护法的制定专家之一。发表三篇高影响因子的科技论文，出版一本专著，一本教科书，在国际重要学术期刊上发表三十多篇论文，是认证实验室成员，工程学、能量有效性与环境保护实验室的成员，也是塞尔维亚SMEITS协会成员，加工工艺国际大会的组委会成员。

报告题目1：INFLUENCE OF DIFFERENT ANGLES OF ATTACK ON NORMAL FORCE COEFFICIENT IN SUBSONIC FLIGHT REGIMES FOR GRID FINS

Numerical models were made using OpenFOAM software to verify assumed behavior of grid fins in subsonic flight regime. Two models are present, first model is part of grid fin called unit grid fin (UGF) and second model is four grid fins on a rocket. Experimental results of normal force coefficient, that were used for verifying results that were obtained by using OpenFOAM, were obtained by other researchers. In first model, geometry model and structured numerical mesh were made using OpenFOAMblockMeshDict file located in <case>/system folder. Second model was made in open source CAD software and unstructured meshing was done using SnappyHexMesh application implemented in OpenFOAM software. Mach’s number value was 0.7. In UGF model, simulation types were laminar and turbulent. In snappyHexMesh simulations only turbulent type simulations were done due to huge error in results for laminar simulation. Turbulent models that were used are k-ꞷSST and k-Ꜫ. Angle of attack was varied from 0 degrees to 15 degrees with a step of 2.5 degrees. Solver that was used in numerical simulations was sonicFoam, due to its application for compressible flows. After obtainingsatisfying mesh density sonicFoam with adaptive time step was used for reducing the time required for simulation to finish.There is similar case already implemented earlier in the OpenFOAM and within the directory $FOAM_TUTORIALS/ compressible/ sonicFoam/ RAS/nacaAirFoil. The values for boundary values are taken based on that case. Calculations are done on Linux Ubuntu 16.04 LTS operating system.

报告题目2：FATIGUE RESISTANCE ANALYSIS UNDER OVERLOADING Abstract：Abstract：Under service-induced environment, the load history may significantly affect the performances of engineering structures due to appearance of the fatigue-critical effects such as overload, underload and overload followed by an underload. Therefore, it is of great importance the development of computational models in order to ensure reliable durability assessments. The present research proposes fracture mechanics-based computational model to analyze the fatigue response under dynamic loading with constant-amplitude and/or overload. New analytical solutions are examined for generating the detrimental effects of crack-like through flaw coupled with the retardation effects. Further, the fatigue degradation is estimated via new life solutions, taking into account stress ratio effect. Representative failure evaluations for two overload crack growth lengths are shown in Fig. 1. Through several case study applications, it will be verified that the fatigue-design model developed can be successfully used as a modern tool to ensure full bearing capacity of plate-type components with through flaws and implemented in the case of an overload and/or constant-amplitude cyclic load environment. In this context, literature-based experiments will demonstrate that the present research allows a reliable assessment of the fatigue strength from the damage tolerance point of view and provides researchers and experts with insight for improvements in safe-integrity design decision making.

报告题目3：EXPERIMENTAL DYNAMIC ANALYSIS OF A GENERATOR ACOUSTIC BARRIER

Abstract：This paper deals with an experimental analysis of the dynamic characteristics of a structure designed as an acoustic barrier of a power plant generator. The generator is a rotating machine which generates an air and structure-borne sound and vibrations on a certain frequencies, depending on its angular speed of rotation. This excitation energy, generated by the source, is transmitted to the acoustic barrier by the wave motion and can cause the oscillations of the structure. Depending on the frequency of the source excitation, oscillations of the structure may occur at one of its natural frequencies, which depend on the shape, dimensions, materials, grounding conditions, as well as other structural parameters. If the excitation frequencies and the natural frequencies of the structure coincide, a resonant oscillation of the structure will occur, which is not a desirable phenomenon and should be avoided. The resonant oscillation of the acoustic barrier, which is analyzed in this paper, can be avoided if it is designed so that its natural frequencies are not in the operating frequency range of the generator, which acts as a source of noise and vibration. The acoustic barrier was analyzed numerically, and the experimental verification was performed in-situ, by the method of impact modal testing. This paper presents the results of an experimental analysis of an acoustic barrier, performed firstly without acoustic panels and then with installed acoustic panels.