Development of a releasable snap-fit connector based on shape memory alloy actuators

Shape Memory Alloy (SMA) based actuator systems provide many advantages compared to conventional actuators and have already successfully established themselves on the market in various applications. The state of the art shows a large number of SMA applications in the field of joining technology. However, these are almost exclusively aimed at providing a reliable, robust but non-detachable connection using the shape memory one-way effect. Approaches to realize a releasable connection for disassembly purposes do not or hardly exist so far. In the present paper it is investigated how shape memory alloys can be used to design releasable snap-fit connectors. Therefore, the state of the art in the field of snap-fit connectors, particularly the systems used in the automotive sector is discussed in order to find potential applications. Beyond that, the functional structure of snap-fit connectors is analyzed to determine which SMA semi-finished products are particularly suitable for this purpose. Different concepts are evaluated and a preferred variant is derived. For detail development, a numerical study will be carried out to determine the influences of various geometric parameters on the performance of the actuator. This is realized using an SMA Finite Element Analysis (FEA) model based on Auricchio's approach, which is described in detail. Based on these results appropriately preconditioned SMA semifinished products are produced and experimentally investigated in order to validate the model. Furthermore, several functional models of releasable snap-fit connectors are produced using additive manufacturing processes thus verifying the approach in experiments.