C. Barile, C. Casavola, G. Pappalettera, C. Pappalettere
PRELIMINARY ANALYSIS FOR A NEW APPROACH TO RELIEVE RESIDUAL STRESSES BY LASER HEATING

Stress relief heat treatment is used to reduce the residual stresses in a structure produced from manufacturing processes. There are many sources of residual stresses, and in particular those due to welding process could be of a magnitude roughly equal to the yield strength of the base material. Uniformly heating a structure to a sufficiently high temperature, but below the lower transformation temperature range, and then uniformly cooling it, can relax these residual stresses. In this paper the attention is focused on the possibility to use a high power laser source that local heats a component in order to relieve the residual stresses. An experimental set up is carried out on aluminum specimen and the preliminary results reported in this paper.

J. Vogel, H.-J. Feige, J. Saupe, S. Schubert, J. Grimm
EXPERIMENTAL ANALYSIS OF THERMO-MECHANICAL MATERIAL PROPERTIES OF PHOTOSENSITIVE POLYMERS

Micro tensile test and Dynamic Mechanical Analysis (DMA) are used to evaluate the material behaviour and several process steps of photosensitive polymers. DMA allows the determination of storage modulus, loss tangent or glass transition region as function of time, temperature and frequency. Furthermore, a sensitive loading device has been developed to carry out tensile tests at polymer micro samples. Stress-strain-curves, YOUNG’s modulus or POISSON’s ratio are analysed by Digital Image Correlation. The results are suitable to modify the process parameters, to characterise thermal and mechanical properties and to develop new application fields.

Martin Stockmann, Ingolf Mönch
DIFFERENTIAL STRAIN GAGE – A NEW SENSOR DEVICE FOR MICROSYSTEMS

The paper describes an operating principle for the electrical measurement of mechanical strain states. This principle gives up the idea of measuring the strain-induced resistance change of single wire conductors and passes on to determining the strain-induced deformation of the electrical field in area conductors. The basic operating principle, sensitivity considerations and the design of a functional prototype are described. Several experimental results in the application fields of transducer technology demonstrate the high capability of this method.

M. Živkovic
EXPERIMENTAL AND NUMERICAL ANALYSIS OF SPOT WELDED JOINTS AND CONSTRUCTIONS

In this paper, experimental and numerical research of spot welded joints is presented. The most important mechanical properties of the base sheet are determined using specimens cut in different directions with reference to the rolling direction. Welding parameters are adopted with respect to the recommendations. The quality of the spot-welded joint is evaluated by experimental and numerical methods. The tensile test was used in choosing the most suitable spot welding regime. Several examples are analyzed. Force-displacement diagrams with fields of effective stress and strain show that implemented large strain theory gives good prediction of the joints behavior.

Carmine Pappalettere
EXPERIMENTAL AND NUMERICAL MODELS IN ORTHOPAEDIC BIOMECHANICS

The article outlines the main results of different research activities, in the field of Orthopaedic Biomechanics, recently conducted at the Experimental Mechanics Laboratory, Politecnico di Bari.