Adiabatic Plasticity of Nanostructured Ductile Materials under Micro-Ballistic Loading
ORAL · Invited
Abstract
Understanding high-strain-rate (HSR) plastic deformation in ductile materials, including polymers and metals, is essential for advancing structure–property relationships under temporally confined loading conditions. As the loading duration approaches the nanosecond regime, the spatial extent of deformation contracts to the microscale due to the finite speed of sound. These extreme conditions generate complex, highly localized mechanical responses, which become even more pronounced when the material contains nanoscale heterogeneities in its physical and chemical structures.
Recent advances in Laser-Induced Projectile Impact Testing (LIPIT) enable well-controlled microscopic HSR loading by accelerating a rigid microsphere as a supersonic ballistic indenter toward a selected region of a specimen. In this talk, I will introduce our efforts to understand material behavior under such extreme conditions through LIPIT-based micro-ballistic experiments. Compositionally and structurally complex metals, such as eutectic high-entropy alloys, are of particular interest, especially as they are increasingly manufactured via additive processes that introduce substantial non-equilibrium states. Their HSR plastic deformation, closely linked to nanoscale physical and chemical heterogeneities, is examined using coefficients of restitution and micro-ballistic hardness measured at representative strain rates on the order of 10⁷ s⁻¹. To provide a multiscale perspective on rate-dependent plasticity, quasi-static and medium-strain-rate responses are also characterized through nanoindentation and split-Hopkinson pressure bar testing. Al-Ni bimetallic nano-lamellar structures are then presented as a model system for the effects of chemically unstable and structurally anisotropic morphologies.
The insights gained from our LIPIT studies on the adiabatic plasticity of complex metals are expected to play a critical role in the design and advancement of additively manufactured alloys, opening new opportunities for creating materials with unprecedented performance attributes.
Recent advances in Laser-Induced Projectile Impact Testing (LIPIT) enable well-controlled microscopic HSR loading by accelerating a rigid microsphere as a supersonic ballistic indenter toward a selected region of a specimen. In this talk, I will introduce our efforts to understand material behavior under such extreme conditions through LIPIT-based micro-ballistic experiments. Compositionally and structurally complex metals, such as eutectic high-entropy alloys, are of particular interest, especially as they are increasingly manufactured via additive processes that introduce substantial non-equilibrium states. Their HSR plastic deformation, closely linked to nanoscale physical and chemical heterogeneities, is examined using coefficients of restitution and micro-ballistic hardness measured at representative strain rates on the order of 10⁷ s⁻¹. To provide a multiscale perspective on rate-dependent plasticity, quasi-static and medium-strain-rate responses are also characterized through nanoindentation and split-Hopkinson pressure bar testing. Al-Ni bimetallic nano-lamellar structures are then presented as a model system for the effects of chemically unstable and structurally anisotropic morphologies.
The insights gained from our LIPIT studies on the adiabatic plasticity of complex metals are expected to play a critical role in the design and advancement of additively manufactured alloys, opening new opportunities for creating materials with unprecedented performance attributes.
*This material is based upon work supported by the Department of Energy-National Nuclear Security Administration Center of Excellence CAMCSE under Award No. DE-NA0004154.
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Presenters
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Jae-Hwang Lee
- Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA 01003, US