Acousto-Plastic Deformation of Metal by Nonlinear Stress Waves

本研究项目致力于了解声塑性效应(APE)的必要性，该效应是当金属试件变形(压缩或拉伸)和超声振动叠加时发生的。当类人猿出现时，观察到显著的一过性软化。这项研究将超越目前文献中提出的现象学描述来处理类人猿。将进行理论和数值研究，以阐明超声振动引起的异常金属形貌。通过引入应变和表观静态应力之间的特殊本构关系，该研究直接解决了过程的动态性质，而不是处理短暂的金属软化效应。关于演化的非线性应力波，一个全面的理论模型正在开发中。模型方程将采用时空守恒元和解元(CESE)方法求解，CESE方法是一种新的高保真求解非线性双曲组的数值框架。理论和建模能力的成功发展将展示一种高保真模拟固体中非线性应力波的新范式。使用并行计算进行超大规模计算可能会为材料模拟的高性能计算指明一个新的方向。随着对APE的深入了解和精确的建模工具，可以实现对各种金属成形/连接过程的高功率超声波的实现。所设想的建模工具还可以应用于各种非线性波动问题，包括地震波在地球上的传播和超声波在生物组织中的传播。该研究项目将促进俄亥俄州立大学的研究人员与福特汽车公司的超声波专家和材料科学家之间有意义的合作。本科生和研究生以及汽车行业的从业人员将通过教育推广和直接培训纳入研究项目。

The present research project addresses the need to understand the Acousto-Plastic Effect (APE), which occurs when metal specimens are deformed (in compression or tension) and ultrasonic vibrations are superimposed. When the APE occurs, a remarkable transitory softening is observed. The research will address APE beyond the phenomenological descriptions presented in the current literature. Theoretical and numerical studies will be conducted to clarify the unusual metal morphology induced by ultrasonic vibrations. The research directly addresses the dynamic nature of the processes rather than treating the transitory metal softening effect by introducing an ad-hoc constitutive relation between strain and the apparent static stress. A comprehensive theoretical model is being developed for the evolving nonlinear stress waves. The model equations will be solved by using the space-time Conservation Element and Solution Element (CESE) method, a novel numerical framework for high-fidelity solution of nonlinear hyperbolic systems. Successful development of the theoretical and modeling capabilities will demonstrate a new paradigm for high-fidelity simulation of nonlinear stress waves in solids. The use of parallel computing for very large-scaled calculations could point to a new direction for high performance computation for material simulations. With in-depth understanding of the APE and the accurate modeling tool, implementation of high-power ultrasounds to various metal forming/joining processes could be achieved. The envisioned modeling tool could also be applied to various nonlinear wave problems, including seismic wave propagation in earth and ultrasonic propagation in biological tissues. The research project will foster a meaningful collaboration between researchers at the Ohio State University, and ultrasound specialists and materials scientists at the Ford Motor Company. Undergraduate and graduate students as well as practicing professions in the automotive industry will be integrated into the research project via educational outreach and direct training.