O. I. Németh, Gy. Farkas
EFFECT OF PRODUCTION TEMPERATURE ON STRENGTH OF POLYMER CONCRETE

In our long-term research, the strength and physical characteristics of concretes with unsaturated polyester binder and their influencing factors are specified. This study is intended to determine how the values of compression strength and flexural strength are affected by the mixing temperature. Our experiments show, that the compression strength of polymer concrete is significantly decreased just by low temperatures (close to the melting point of catalyst). Flexural strength is not affected significantly by temperature. The reasons for this discrepancy should be further examined later on, by taking into consideration the factors influencing polyester polymerization.

K. Vogel, D. Wuensch, S. Uhlig, J. Froemel, F. Naumann, M. Wiemer, T. Gessner
MECHANICAL CHARACTERIZATION OF GLASS FRIT BONDED WAFERS

Wafer bonding is a key technology in the manufacturing of microelectronic and micromechanical systems on industrial scale. Especially glass frit bonding is often used for the encapsulation of MEMS devices on wafer level. To ensure the reliability of these bonds and to prevent critical failure of the systems, characteristic mechanical properties of the bonded interface are required. The fracture toughness and the shear strength are suitable values to characterize the bonding strength and can be determined by micro chevron and shear testing. They depend on the bonding parameters as well as the test speed. Due to the correlation between measured bonding strength and test speed a maximum test speed has to be identified to obtain reliable failure criteria regarding the fracture toughness and the shear strength.

A. I. Botean, I. Takacs, M. Hardau
THE STUDY OF STRESS DISTRIBUTION FOR THE FEMORAL BONE IN BIPODAL SUPPORT – 3D MODELING

Considering bipodal position, each of the two femoral bones take over half the body weight, the main load that they are subject to beeing the eccentric compression.
The purpose of this paper is the qualitative evaluation of the femoral bone in the proximal area. The experimental method used is photoelasticimetry through transparency, while for the numerical analisys we used the finite element method (ANSYS).

D. Károly, Z. Kakasi, E. Bognár, P. Szabadíts
INVESTIGATION OF FUNCTIONAL PROPERTIES OF CORONARY STENT SYSTEMS

This article introduces five measurement methods for investigation of functional properties of coronary stent systems. The properties were analysed in theory, and then several stents were measured and evaluated. Crossing profile, flexibility of the stent system, foreshortening, metallic surface area, the largest and the smallest cell sizes, the maximum achievable cell diameter and side branch access were measured. Four types of coronary stents were examined, two pieces from each type. The results show that the properties mostly depend on geometry, stent pattern and material. These investigations can help the physics to select the appropriate stent.

C. Dudescu, J. Naumann, M. Stockmann
OPTICAL MEASUREMENT OF THE STRAINSTRESS RESPONSE DURING UNLOADING OF METAL SHEETS UNDERGOING LARGE PLASTIC DEFORMATIONS

The optical measurement techniques have shown more precise results about the mechanical behaviour of materials. They enjoy the advantages of being non-contact, full-field, with a high spatial resolution and offer the possibility to observe the local mechanical behaviour. The paper presents the analysis by Electronic Speckle Pattern Interferometry (ESPI) of the unloading behaviour of metal sheets that undergone large plastic deformations. The springback of the sheet metals after large deformations during deep drawing is not a strongly linear process with a constant Young’s modulus but, the stress-strain behaviour during the unloading phases, shows considerably non-linear and inelastic effects. Unloading of two types of steel sheets for cold forming, a cold-rolled high strength micro-alloyed steel and a low carbon steel sheet, and an aluminium alloy sheet have been analysed using the ESPI method. The experimental measurements showed that the stress-strain curve during unloading is non-linear and the secant moduli of unloading curves decrease with increasing of prestrain.