Currently, cutting-edge Additive Manufacturing techniques, such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM), offer manufacturers a valuable avenue, especially in biomedical devices. These techniques produce intricate porous structures that draw inspiration from nature, boast biocompatibility, and effectively counter the adverse issues tied to solid implants, including stress shielding, cortical hypertrophy, and micromotions. Within the domain of such porous structures, Triply Periodic Minimal Surface (TPMS) configurations, specifically the Gyroid, Diamond, and Primitive designs, exhibit exceptional performance due to their bioinspired forms and remarkable mechanical and fatigue properties, outshining other porous counterparts. Consequently, they emerge as strong contenders for biomedical implants. However, assessing the mechanical properties and manufacturability of TPMS structures within the appropriate ranges of pore size, unit cell size, and porosity tailored for biomedical applications remains paramount. This study aims to scrutinize the mechanical behavior of Gyroid, Diamond, and Primitive structures in solid and sheet network iterations within the morphological parameter ranges suitable for tasks like cell seeding, vascularization, and osseointegration. A comparison with the mechanical characteristics of host bones is also undertaken. The methodology revolves around Finite Element Method (FEM) analysis. The six structures are originally modeled with unit cell sizes of 1, 1.5, 2, and 2.5 mm, and porosity levels ranging from 50% to 85%. Subsequently, mechanical properties, such as elasticity modulus and yield strength, are quantified through numerical analysis. The results underscore that implementing TPMS designs enables unit cell sizes between 1 and 2.5 mm, facilitating pore sizes within the suitable range of approximately 300-1500 μm for biomedical implants. Elasticity modulus spans from 1.5 to 33.8 GPa, while yield strength ranges around 20-304.5 MPa across the 50%-85% porosity spectrum. Generally, altering the unit cell size exhibits minimal impact on mechanical properties within the range above; however, it's noteworthy that smaller porosities correspond to heightened defects in additively manufactured structures. Thus, for an acceptable pore size range of 500-1000 μm and a minimum wall thickness of 150 μm, a prudent choice would involve adopting a 2.5 mm unit cell size.

In contemporary orthopaedic practice, total hip arthroplasty (THA) is a reliable surgical technique for hip joint replacement. However, introducing solid implants into human bone tissue can lead to complications, notably stress shielding and cortical hypertrophy. These issues often stem from mechanical mismatches, particularly stiffness disparities, between the solid implants and the bone tissue. A potential solution lies in adopting porous implant structures with lower stiffness and tuneable mechanical properties based on morphological parameters such as porosity, relative density, and unit cell sizes. This study, which is of significant importance to orthopaedic implant development, aims to develop porous implants that meet biological and manufacturing requirements, employing topology optimization methods to address the challenges associated with conventional solid implants. To achieve this objective, we conducted finite element analyses to compare the stress distribution within healthy bones with solid and newly developed porous implants under real-life loading conditions. The porous implants were designed with triply periodic minimal surface structures, featuring uniform relative density and gradient relative density mapping derived from topology optimization results considering additive manufacturing capabilities and biological constraints. Our findings provide critical insights into the impact on the bone's mechanical environment about the choice of implant. Specifically, solid implants significantly decrease applied stress within the cortical bone, leading to stress shielding and subsequent bone resorption, consistent with bone remodelling principles and Wolff's law. However, replacing the solid implant with uniform porosity with maximum compliance and employing gradient porous implants based on topology optimization methods significantly increases the strain energy density ratio. Specifically, the uniform gyroid, uniform diamond, gradient gyroid, and gradient diamond stems exhibited increases of 43%, 39%, 27%, and 25%, respectively, compared to the solid stem, effectively mitigating the stress shielding effect. However, amongst porous stems, only gradient designs could meet the mechanical strength requirements with a safety factor greater than one, rendering them suitable replacements for solid implants aimed at addressing associated complications. These results hold promise, particularly with the advancements in additive manufacturing methods capable of fabricating these porous implants with acceptable precision.

Human and animal footprints found in the Valsequillo Basin were formed on the upper bedding planes surfaces of a volcanic ash (Xalnene Ash) deposited by a subaqueous volcano along the shores of a Pleistocene lake. The footprints were made on lake shorelines and the exposed lake floor during low stands associated, either with water displacement during the volcanic eruption, or due to climatically-driven fluctuations in the water balance. The Xalnene Ash has been dated to at least 40 K BP and consequently the human footprints provide evidence for much earlier colonization of the Americas than is often accepted. The methodology used to record, analyze and conserve these footprints used three-dimensional laser scanning, with sub-millimeter precision. This data were used to reproduce polymer models of individual footprints using the application of rapid-prototyping technology. This technology has wide significance for the study of ichnofacies in general. The characteristics of the human footprints and some problems associated with the volcanic ash as a molding medium for the clarity of these characteristics are given. These human footprints and their dating resolve the controversy related to the age of the archaeological and associated megafaunal remains that were reported in the Valsequillo Gravels in the 1960s and 1970s.

This paper describes a detailed study of tube extrusion by simulation using finite element method (FEM). The finite element model used one-sixth of symmetry. The extrusion load, temperature evolution and metal flow were predicted. Innovative methods, combining both grid and surface tools, were used to define in detail the flow of material. These showed clearly the inner and outer surface formation mechanisms of the tube extrusion. The seam weld, an important quality indicator, was also evaluated by selecting an appropriate criterion.