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Powered-two-wheelers (PTWs) are increasingly popular because of their lower cost compared to cars, and therefore the riders’ exposure risk is increasing. Due to their complex dynamics characterized by high non-linearity and inherent instability, PTWs are more difficult to control compared to four-wheeled vehicles. Wobble is a high-frequency instability mode affecting the steering assembly of the PTW, and which often causes the rider to lose control and crash when it occurs. In this paper, we present the design of a new motorcycle semi-active steering damper integrated into the steering column and utilizing a magnetorheological fluid (MRF) for variable damping torque. An analytical model of the concept was first used to perform the preliminary sizing, followed by concept validation using a 3D FE multiphysics magnetic-fluid analysis. The final innovative design offers several advantages compared to traditional steering dampers: (i) a wide range of adjustable damping torque values, with a multiplication factor up to 10 with a maximum electrical current of 2 A; (ii) total integration into the motorcycle steering column enabled by its axial design and limited radius; (iii) a simple chamber geometry that allows for easy manufacture; (iv) longer seal life due to the absence of direct contact between seals and the MRF.

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Low cycle fatigue tests have been performed at 1038 • C on equiaxed MAR-M-247 under a mean compressive strain. Strain ranges assessed were 0.4, 0.6 and 0.8%, with this test program reflecting industrial gas turbine duty cycles. Fractographic analysis demonstrated transgranular crack propagation with intergranular fast fracture. Heavily oxidized secondary cracks were observed throughout. The details of a Lemaitre-Chaboche constitutive model that has been applied to the experimental stress-strain response are described. It was found that this model was capable of capturing both plastic shakedown and kinematic hardening effects with a high degree of accuracy (R 2 up to 0.997 and SSE up to 6E+4). The suitability of extending this model to address different strain histories are detailed.