Analysis Of Residual Stress And Microstructure of Pure Titanium During Single Point Incremental Forming For Biomedical Applications

Abstract

Single point incremental forming (SPIF) is a branch of incremental sheet forming where a very small portion of the sheet is deformed plastically at any moment. This incremental highly localized point deformation is done by a simple hemispherical tool, whose path is numerically monitored by a CNC device, performs this progressive extremely localized deformation. Since no die is required during forming, highly customized and user oriented sheet metal products can be manufactured employing the process.deformation occurs at a large level, which leads to the development of non-uniform residual stresses that affects the geometrical dimensions of cranial plate manufactured by SPIF. SPIF can be readly employed in manufacturing of customized orthopaedic implants and braces, e.g, cranial implants, ankle implants , elbow and knee support braces. The forming of these sheets through SPIF would result in generation of residual stress in the sheet metal. With time and other physical factors, these residual stresses would be relieved resulting in dimensional inaccuracy. This inaccuracy is highly detrimental in the case of implants and highly undesirable for supporting braces. The objective of this work was to investigate, experimentally, the state and magnitude of residual stresses on caused by commercial pure titanium grade 2 by in SPIF made parts used in the for biomedical industry applications with respect to important process parameters (forming angle and incremental step depth). The geometry of an inverted cone with a different forming angle at different step depth was studied. The X-ray diffraction technique was used for the experimental measurements of the residual stresses. Microstructural behavior of the final product at each incremental step depth and forming angles are also observed by EBSD and correlated with residual stresses. The experimental findings showed the formation of compressive residual stresses and increased tensile residual stresses with increase in incremental step depth and steepness of forming angles.on the surface of Ti sheet during forming. Significant variation was noted in surface residual stress with variable parameters of forming.