Papers by Author: Gian Luca Rossi

Abstract: Thermolastic Stress Analysis (TSA) has been recently developed as a direct investigating method for the study of the stress field around the crack tip of a cyclically loaded structure. The advantage of using measurement techniques based on the thermoelastic effect lays in the fact that stress intensity factors may be determined based on the effective stress distribution around the crack tip rather than calculated from the crack length and amplitude of cyclic loads. This paper reports results related to fatigue tests on Friction Stir Welded alluminium alloys sheets. Fatigue crack propagation experiments were performed by employing single-edge notched specimens, in tensiontension condition with R=0.1, up to failure. The application of TSA allowed the monitoring of crack formation and growth in real time, providing the actual stress distribution around the crack tip for the different technological parameters used in the welding process. Stress intensity factors were determined based on the TSA data and compared to those calculated using an ABAQUS FE model.

Abstract: Motorcycle frames are mechanical components that need to be optimised in terms of performance and costs but with a limited amount of resources compared to, for example, car frames. Fatigue testing of the component is required for qualification and this is typically performed by using rotating drums with steps or servo-controlled hydraulic actuator based test benches. Therefore a fast and simple measurement and testing technique that operates during the fatigue tests will be a very useful tool. In this paper the possibility of analysing these components by measuring the stress levels and stress concentration in critical parts by thermoelasticity is investigated. The development of a multibody model, useful to simulate the typical working conditions of the motorcycle frame, is also described.

Abstract: In this paper a new measurement technique to perform thermoelastic stress analysis on rotating mechanical component is proposed. The idea is to use a particular realization of the Dove prism optical system, optimized to work width infrared radiation, able to give a fixed output image of a rotating surface on where a normal thermoelastic measurement system can be applied. The realization of a first prototype of this optical system is described. First results on a test case are illustrated.