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In this paper was synthesized a bioceramic material based on calcium and phosphorus. Also, the effect of synthesis parameters on the structure and properties of the obtained powders has been studied. In this sense, the stirring speed and the aging time of the precipitates, in the case of some hydroxyapatite powders, are studied. The results show products with the desired characteristics, in terms of structure and composition of analyzed powders.

The aim of this paper is to present a handmade laboratory device with data acquisition for estimating the thermomechanical characteristics (caused by dimensional changes in height) of polymeric materials. This experimental device is able to perform penetration tests, monitoring the expansion of the samples and based on experimental tests, the thermal expansivity or coefficient of thermal expansion (CTE) can be determined. A data acquisition instrument, which register (i) the deformation of the specimen, by using two displacement transducers (an inductive proximity transducer and an transmission type photoelectric linear encoder) as well as registers (ii) the temperature (at the base of the specimen and in the vicinity of the point of contact with the penetrator) is used. In order to test the device and to highlight its qualities, preliminary tests were carried out on a thermosetting polymeric material in various stages of polymerization.

The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction in plane friction couplings with sliding movement. On tribometric device (made in our laboratory) we can measure the friction force, friction coefficient and wear, for different loading conditions, speeds, time and material coupling. For the measurement of the frictional force as well as of the coefficients of friction, mainly the method with a resistive tensiometric transducer is used. With a DataQ DI 245 data acquisition board it is possible to record up to 2 kHz frequencies in the range of -10 ÷ +10 mV with a resolution of 13 bits. To test the functionality of the device, a preliminary test was carried out for a steel pin- on- cast iron disc, for different values of the normal pushing force. The device was calibrated and the measurement results were recorded and processed on the computer.

In this paper is presented a comparative study regarding the synthesis of hydroxyapatite powders. The chosen method of synthesis of this biomaterial was chemical co-precipitation. The structure, size and morphology of the obtained powders were analyzed by X-ray diffraction, infrared spectroscopy - FTIR, dynamic light diffusion DLS tehnique and scanning electron microscopy-SEM. The results obtained were compared with those obtained on a commercial hydroxyapatite powder. Investigation methods have confirmed the synthesis of a high purity hydroxyapatite with a optimal degree of crystallization and crystallinity for the reconstruction and regeneration of hard tissue.

With the development of industry have made efforts to improve the performance of braking systems of motor vehicles on public roads. The choice of materials used for coupling brake system involved the development of new materials that meet safety requirements in circulation. During braking of any vehicle, due to the friction created between the disk and pad, temperature rise occurs with negative effects on the process of slowing down the vehicle. Mechanical and thermal stress being put on the brakes is very high. Due to overheating, brake discs and pads may warp or crack, and the material they are made may their change its structure. These defects give rise to vibrations and noise during braking, to reduce the coefficient of friction, reduce the effectiveness of the braking mechanism. This paper proposes a study regarding the thermal stresses effects of brake mechanism on the disc material of a car Dacia Logan. It proposes a theoretical model to calculate the temperature that occurred during the operation of the braking system and experimental analysis on the influence of temperature on the brake disc material.

The strength of materials is a complex function which involve two main components, material nature and the presence of defects. Usually glasses exhibit a fragile behavior due to a numerous flaws and the effect is a large range of data scattering in tensile strength measurement. The Weibull probability density function was applied to describe the scatter of experimental data in tensile test, which emphasize a difference between variance in case of tensile strength of three stainless steel grades and glass epoxy composite. The main goal is mathematical modeling of those distributions and finding of equations which predict the probability of failure for a sample subjected to a specific stress.

For the mathematical modeling of the bending behavior on a microgripper compliant arm it is necessary to estimate the compliance impact on the system. In case of low bending force values, the linear dependence between force and elastic deformation is presumed. After performing bending experiments on full section and, respectively, compliant arms, there was determined an elastic coefficient allowing the mathematical modeling of the compliant beam as a full section beam and a moment of inertia reduced proportionally to the calculated elastic coefficient. The modeling results are consistent with the results of the experiments performed on the prototype.

Bioactive glasses based on SiO2-CaO-P2O5 system have been synthesized by sol – gel process. The powder glass obtained has been characterized by X-ray diffraction, X-ray fluorescence spectroscopy (XRF), and Fourier transform-infrared spectroscopy (FTIR). In vitro study reveals formation of apatite layer at surface of powder glass, after 3 days of soaking in simulated body fluid.