Download or read book Effects of Size and Geometry on the Thermomechanical Properties of Additively-manufactured NiTi Shape Memory Alloys written by Nazanin Farjam and published by . This book was released on 2018 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shape memory alloys (SMAs) and especially NiTi as the most common SMA have received much attention due to their distinct properties, including shape memory and superelasticity. However, due to their ductility and high reactivity, the processing and machining of these materials is a challenge. Nevertheless, additive manufacturing techniques, and mostly selective laser melting (SLM) method, have made the fabrication of complicated NiTi parts possible. During SLM process, different factors are important to produce the desired geometry and functionality. In this study, we have investigated the effect of size and shape of the SLM fabricated NiTi samples on their mechanical behavior. Tensile samples with different thicknesses and shapes were fabricated for this investigation. Differential Scanning Calorimetry (DSC) were conducted to measure the transformation temperatures of different samples. A small difference is observed between the transformation temperatures of various sizes and shapes samples. Thicker rectangular samples had a little higher transformation temperatures while the oval and circular ones were very similar in aspect of transformation temperatures. Moreover, tensile tests including loading, unloading, and heating were done for all of the samples and the mechanical responses were compared with each other. Thinner parts, either rectangular cross sections or the oval ones, showed more tensile strength due to their finer microstructure which originated from more area exposing to high cooling rate during the fabrication process. Digital image correlation (DIC) was used for strain measurements to study the of strain distribution along the sample. Using DIC, made us sure that conventional extensometers are not appropriate to measure the strain since SLM NiTi parts have a very uncommon microstructure leading to a completely non-uniform stress distribution. The accuracy of fabrication is also discussed for all of the samples and more error was observed for thinner parts.