An investigation of the mechanical strain rate, inelastic behavior, and microstructural evolution under deformation for an as-cast pearlitic gray cast iron (GCI) is presented. A complex network of graphite, pearlite, steadite, and particle inclusions was stereologically quantified using standard techniques to identify the potential constituents that define the structure–property relationships, with the primary focus being strain rate sensitivity (SRS) of the stress–strain behavior. Volume fractions for pearlite, graphite, steadite, and particles were determined as 74%, 16%, 9%, and 1%, respectively. Secondary dendrite arm spacing (SDAS) was quantified as 22.50 μ m ± 6.07 μ m. Graphite flake lengths and widths were averaged as 199 μ m ± 175 μ m and 4.9 μ m ± 2.3 μ m, respectively. Particle inclusions comprised of manganese and sulfur with an average size of 13.5 μ m ± 9.9 μ m. The experimental data showed that as the strain rate increased from 10 −3 to 10 3 s −1 , the averaged strength increased 15–20%. As the stress state changed from torsion to tension to compression at a strain of 0.003 mm/mm, the stress asymmetry increased ∼470% and ∼670% for strain rates of 10 −3 and 10 3 s −1 , respectively. As the strain increased, the stress asymmetry differences increased further. Coalescence of cracks emanating from the graphite flake tips exacerbated the stress asymmetry differences. An internal state variable (ISV) plasticity-damage model that separately accounts for damage nucleation, growth, and coalescence was calibrated and used to give insight into the damage and work hardening relationship.

The present study, through finite element simulations, shows the geometric effects of a bioinspired solid on pressure and impulse mitigation for an elastic, plastic, and viscoelastic material. Because of the bioinspired geometries, stress wave mitigation became apparent in a nonintuitive manner such that potential real-world applications in human protective gear designs are realizable. In nature, there are several toroidal designs that are employed for mitigating stress waves; examples include the hyoid bone on the back of a woodpecker's jaw that extends around the skull to its nose and a ram's horn. This study evaluates four different geometries with the same length and same initial cross-sectional diameter at the impact location in three-dimensional finite element analyses. The geometries in increasing complexity were the following: (1) a round cylinder, (2) a round cylinder that was tapered to a point, (3) a round cylinder that was spiraled in a two dimensional plane, and (4) a round cylinder that was tapered and spiraled in a two-dimensional plane. The results show that the tapered spiral geometry mitigated the greatest amount of pressure and impulse (approximately 98% mitigation) when compared to the cylinder regardless of material type (elastic, plastic, and viscoelastic) and regardless of input pressure signature. The specimen taper effectively mitigated the stress wave as a result of uniaxial deformational processes and an induced shear that arose from its geometry. Due to the decreasing cross-sectional area arising from the taper, the local uniaxial and shear stresses increased along the specimen length. The spiral induced even greater shear stresses that help mitigate the stress wave and also induced transverse displacements at the tip such that minimal wave reflections occurred. This phenomenon arose although only longitudinal waves were introduced as the initial boundary condition (BC). In nature, when shearing occurs within or between materials (friction), dissipation usually results helping the mitigation of the stress wave and is illustrated in this study with the taper and spiral geometries. The combined taper and spiral optimized stress wave mitigation in terms of the pressure and impulse; thus providing insight into the ram's horn design and woodpecker hyoid designs found in nature.

Rollers loaded above their shakedown limit are known to undergo cumulative plastic shearing of their surface layers. An approximate analysis of this deformation by Merwin and Johnson (1963) was in good accord with experiments, but a recent finite-element calculation by Bhargava et al. (1984) predicted much larger deformations. This paper investigates the discrepancy and presents an alternative analysis which supports that by finite-elements.

The performance of traction drives depends to a large extent on the rheological properties of the fluid in the EHL contact. Through the use of the recently proposed J + T constitutive equation, the influence of elastic effects in the fluids is examined. The results were compared with those obtained from conventional analysis. It is shown that essentially three regions of influence exist. For small values of spin and side slip the elastic effects in the fluid dominate and no consideration of the spin and side slip is required. At higher values of spin and side slip the elastic effect still exists but slip is influenced by the spin and slide slip. At still higher values of side slip and spin, the elastic effects in the fluid may be neglected. The various boundaries of the regions of influence depend on the aspect ratio of the contact.