The Micro Topology and Statistical Analysis of the Forces of Walking and Failure of an ITAP in a Femur

This paper studies the forces acting upon the Intraosseous Transcutaneous Amputation Prosthesis, ITAP, that has been designed for use in a quarter amputated femur. To design in a failure feature, utilising a safety notch, which would stop excessive stress, σ, permeating the bone causing damage to the user. To achieve this, the topology of the ITAP was studied using MATLAB and ANSYS models with a wide range of component volumes. The topology analysis identified critical materials and local maximum stresses when modelling the applied loads. This together with additive layer manufacture allows for bespoke prosthetics that can improve patient outcomes. Further research is needed to design a fully functional, failure feature that is operational when extreme loads are applied from any direction. Physical testing is needed for validation of this study. Further research is also recommended on the design so that the σ within the ITAP is less than the yield stress, σs, of bone when other loads are applied from running and other activities.

Mechanical properties of heat-resistant superalloy Inconel 718 obtained by selective laser melting and heat treatment under different load directions

Additive manufacturing is a promising modern direction that allows quickly and with high accuracy layer-by-layer manufacture of complex-shaped products using a computer model from almost any metal powders. This work is devoted to the study of the influence of specimen orientation during 3-D printing and heat treatment modes on the mechanical properties of specimens made of Inconel 718 heat-resistant nickel alloy manufactured using SLM technology. In the study of the position of the specimen during printing, it was found that the strength indicators are slightly higher for vertical specimens (up to 9%), and the plasticity is lower on average by 20%. After standard heat treatment, which consists of two stages (quenching and aging) with cooling in quiet air, the strength values of vertically and horizontally constructed specimens are very close (the difference is up to 3%).The plasticity values for the horizontal position of the specimen when printing are 10% and 30% higher. According to macrogeometry, the specimens under study have cup fracture; according to microfractors, it was established that the fracture mechanism is viscous and quasi-brittle. In the initial state, which is formed by 3-D printing, there were signs of viscous fracture: the crack propagates mainly by separating the metal in planes that do not coincide with the crystallographic planes of the sections, mainly the fracture surface in the form of pits - microdepressions on the fracture surface. representing the exposed surfaces of the microvoids formed during the plastic flow of the metal. In the study of the metal of the test specimens in the polished state, it was found that specimens No. 1-5 had high integrity (low porosity), a small amount of oxide inclusions was observed. The study found that the presence of defects in the form of micropores did not lead to a significant reduction in the mechanical properties of the test samples.

Development of an arthroscopically compatible polymer additive layer manufacture technique

This article describes a proof of concept study designed to evaluate the potential of an in vivo three-dimensional printing route to support minimally invasive repair of the musculoskeletal system. The study uses a photocurable material to additively manufacture in situ a model implant and demonstrates that this can be achieved effectively within a clinically relevant timescale. The approach has the potential to be applied with a wide range of light-curable materials and with development could be applied to create functionally gradient structures in vivo.