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德克萨斯大学奥斯汀分校Stelios Kyriakides教授报告会

发布时间:2016/06/09   作者:   点击:[]



Stelios Kyriakides

John Webb Jennings Chair in Engineering

Professor of Aerospace Engineering and Engineering Mechanics

Director of the Center for Mechanics of Solids, Structures and Materials



Stelios Kyriakides德克萨斯大学奥斯汀分校航空工程和工程力学系教授,美国国家工程院院士。现任John Webb Jennings(工程部)主席,奥斯汀分校固体力学、结构力学和材料力学中心主任。以一等奖学金获得英国布里斯托大学航空工程学士学位,在加州理工学院获得航空学硕士、博士学位。在多个重要学术组织任职,包括美国机械工程师协会应用力学分会主席、美国力学学会主席、美国国家理论与应用力学委员会主席、理论与应用力学国际联合会(大会学术委员会)成员。现任固体力学领域重要期刊IJSS主编,同时在多个知名期刊编辑部任职。曾获2009年美国机械工程师协会颁发的Warner T. Koiter奖章,是德克萨斯医学工程科学科学院院士、西班牙杰出力学讲座学者、法国里昂国立应用科学学院荣誉博士。



报告题目:Crushing and Energy Absorption of Open-Cell Foams

        Abstract:Lightweight cellular materials such as foams exhibit excellent energy absorption characteristics and are widely used for impact mitigation in a variety of applications. The crushing behavior of an Al-alloy open-cell foam under quasi-static and dynamic loadings is studied through a combination of experiment and analysis. X-ray tomography is used to establish the irregular polyhedral cell microstructure. Quasi-static crushing is performed under displacement control and the evolution of deformation in the specimen is monitored using X-ray tomography. The response exhibits a relatively stiff linearly elastic regime that terminates into a load maximum, followed by an extended load plateau during which localized cell crushing initiates and gradually propagates throughout the specimen. This general behavior is repeated when the foam is impacted at lower speeds, whereas for higher impact speeds the specimen is crushed by planar shocks with increasingly higher stress and deformation behind the shock. The shock-impact speed Hugoniot now becomes the underlying constitutive behavior of the foam.

        The experiments are simulated using micromechanically accurate foam models developed using the Surface Evolver software. The linear sides of the skeletal microstructure are “dressed” with appropriate distributions of solid, modeled as shear-deformable elastic-plastic beams in LS-DYNA. Such models are shown to reproduce quasi-static crushing faithfully from the initial elastic behavior, to the localization and propagation of crushing responsible for the extended stress-plateau. Modeling of dynamic crushing confirms limited inertial effects below a critical speed and shock formation above it. In the shock regime the models reproduce the stress enhancement behind the shock, the shock front velocity, and the energy absorbed. The implications of the results on the design of energy absorbing structures that incorporate foams will be discussed.


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