The High-Performance Shape Memory Effect (HP-SME) on NiTi Wires and Components
Abstract: A few years ago, a new approach was reported for using shape memory alloys (SMAs) as actuators at higher stress levels and temperatures than those conventionally used [1]. This approach is based on a phenomenon named the high-performance shape memory effect (HP-SME). It consists of the thermal cycling of stress-induced martensite, so it is suitable for those SMAs that show austenitic phase at room temperature to develop new shape memory actuators operating at higher working load (about 1 GPa) and temperatures.
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Self-Heating and Fatigue Assessment of Additively Manufactured NiTi Alloy using Laser Powder Bed Fusion
Abstract: Rapid methods for assessing the fatigue properties of materials have been developed, among which the self-heating method stands out as particularly promising. This approach analyses the thermal signal of the specimen when subjected to cyclic loading. In this research, the self-heating method was utilized for the first time with laser powder bed fusion (LPBF) of NiTi alloys, examining two specific loading conditions: loading ratios of 0.1 and 10. A thorough examination of the material self-heating behaviour was conducted. For comparative purposes, conventional fatigue tests were also conducted, alongside interrupted fatigue tests designed to highlight the underlying mechanisms involved in high cycle fatigue and potentially self-heating behaviour. The investigation revealed several key mechanisms at play, including intra-grain misorientation, the emergence and growth of persistent slip bands, and the formation of stress-induced martensite.
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