In‐Field Measurement of Forces and Deformations at the Rear End of a Motorcycle and Structural Optimisation: Experimental–Numerical Approach Aimed at Structural Optimisation

Abstract: The present study concerns the analysis of the asymmetric displacement behaviour of the rear part of a motorcycle. Stylistic reasons led to the design of a vehicle with only one suspension located on the left‐hand side. Experimental tests performed on a circuit with seven obstacles along a straight line confirmed that the bending displacement is higher on the right‐hand side than on the left. This study aimed to perform a structural optimisation of the components involved at the rear end of the motorcycle, to find a solution to the problem. A hybrid approach is applied: the force acting on the suspension and bending displacements at the rear end were simultaneously measured in working conditions; a finite‐element method model was then set up, validated and applied for design optimisation purposes. Both methodological aspects and applicative results are presented and discussed. Finally, a solution in accordance with design specifics is proposed.     

Numerical Modelling of the Activation Behaviour of SMA‐Actuator Wires – Application in an Innovative Drive System

The activation behaviour of Shape‐Memory‐Alloy actuators (SMA) (and more specifically their dynamic properties) is characterised by the rate of heating and cooling. This paper deals with the development, the validation and the application of a numerical model that simulates the activation behaviour of straight SMA‐wires depending on their geometry, the loading condition and an arbitrary time variant heating current. Taking changing thermal, electrical, geometric and mechanical boundary conditions into consideration, the model supports the design layout process of technical solutions with SMA‐wires. Based on this numerical model for dimensioning and conditioning of SMA‐actuators, an innovative rotatory drive system powered by straight SMA‐wires is presented.     

Modelling Residual Strains During Cycling of Ti–Ni and Ti–Ni–Cu Shape Memory Alloys in a Pseudoelastic Range of Behaviour Conditions

Abstract: Pseudoelastic behaviour of three types of Ti–Ni shape memory alloys in a pseudoelastic state has been studied under conditions of maximum strain‐ and maximum stress‐controlled cycling. Experimental results proved that residual deformation after unloading increases with the number of cycles; however, critical stress for the induction of martensite and the energy dissipated in one cycle decline during cycling. A higher critical stress for slip, and more intense cyclic dislocation hardening promoted by greater maximum deformation and greater maximum applied stresses, generally reduce the rate at which residual elongation grows with the number of cycles, and tend to stabilise the cyclic stress‐elongation diagrams. The small magnitude of critical stress for slip in low‐nickel alloys, and also cyclic strain hardening, induce greater internal stresses and a more marked decrease in critical stress for the induction of martensite as cycling progresses. Detailed analysis of plastic deformation propagation in cyclically loaded specimen helped develop a model of dependence of residual elongation on the number of cycles. This model enables identification of three main factors that govern the magnitude of residual elongation: one residual plastic elongation caused by dislocation hardening after the alloy is heat treated, and two cyclic strain hardening parameters describing how residual elongation grows with number of cycles, and how this residual elongation is reduced, as cycles increase, by the rising critical stress level for slip. The model has proved to yield very close agreement with experimental findings.