Publications

Abstract not provided.

The purpose of this work is to fit a previously developed empirical equation for puncture energy to simulation data. The conservative puncture energy equation could be used to expedite the process of performing calculations in the development of safety measures, avoiding the need to create complex finite element models for specific puncture scenarios. A total of 108 simulations are developed by varying coupon thickness, coupon material, probe shape, and probe diameter. The simulations are comprised of a low-velocity probe puncturing the coupons, from which the probe kinetic energy change is calculated. The empirical equation is fit to the dimensions, material properties, and energy results using a non-linear least-squares regression method within Python, which determines the two constant parameters for each fit. More statistically significant fit results are achieved by separating the data by probe shape and coupon material.

Abstract not provided.

Ductile materials fail through mechanisms of void nucleation and coalescence. A tensile test of a ductile metal begins with reversible elastic deformation, proceeds through permanent plastic deformation, and ends with rupture. Dislocations in the grains of a metal do not slip in the elastic range but begin moving in the plastic range. As the dislocations interact with grain boundaries and each other, they cause increasing resistance to plastic deformation, termed work hardening. The applied load and the true stress rise together during this process. When the dislocations have no room to move, voids open up in the material. As these voids coalesce into cracks, the true stress rises rapidly and the sustained load decreases. Rupture occurs when the cracks propagate through the specimen and it loses all load-carrying capacity. The complexity of the ductile fracture phenomenon continues to attract substantial attention from researchers. Sharp objects in a production environment can puncture fragile components made from ductile metals. Non-linear dynamic simulations help engineers to plan processes such that these components do not fail when an accident happens. The projectile is termed a probe, and the component is the target. The surface of the probe that contacts the target may be sharp, blunt, or flat. Probes are typically cylindrical for simplicity, but other shapes that exist in the production environment are equally applicable.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Sharp tools in a production environment can puncture fragile components. This project analyzes a slender probe as it penetrates a ductile material. Finite element models of probe penetration problems need material models that are accurate through the full range of strain. Elastic properties are frequently derived and are available for most metals with a strong statistical basis. Stress-strain curves including the plastic range are limited and usually stop at the ultimate strength, where void nucleation occurs. Criteria for damage accumulation and rupture are difficult to obtain for many materials. Tests have been performed on coupons of 7075-T651 plate with three probes. The geometry of the coupon and probes are provided, as well as appropriate initial and boundary conditions. The mean energy required for each of the probes to penetrate the coupon is also provided. The objective of this project is to demonstrate three advanced material models for 7075-T651 plate with failure criteria and derive the requisite parameters for each model.

Syntactic foam encapsulation protects sensitive components. The energy mitigated by the foam is calculated with numerical simulations. The properties of a syntactic foam consisting of a mixture of an epoxy-rubber adduct and glass microballoons are obtained from published literature and test results. The conditions and outcomes of the tests are discussed. The method for converting published properties and test results to input for finite element models is described. Simulations of the test conditions are performed to validate the inputs.