The objective of this work is to provide an efficient tool of Reliability-Based Design Optimization (RBDO) for soil tillage machine design process in order to achieve designs with a required reliability (safety) level. An efficient methodology that controls the reliability levels for different statistical distribution cases of random soil properties is developed. This developed strategy is based on design sensitivity concepts in order to determine the influence of each random parameter. The application of this method consists in taking into account the uncertainties on the soil tillage forces. The tillage forces are calculated in accordance with analytical model of McKyes and Ali with some modifications to include the effect of both soil-metal adhesion and tool speed. The different results show the importance of the developed strategy to improve the performance of the soil tillage equipments considering both random geometry and loading parameters.

Plastic pipes are being more widely used in various industries, as they combine both a rather light weight and quite high physical mechanical performance characteristics. The present article materials are devoted to the researches, relating to the determination of the various hydrocarbon compounds effect on some mechanical properties reduction degree of samples cut from HDPE pipes, represented by characteristic values of curves (strength - tensile strain) as an absorption result. In the course of the research, the gasoline presence in material structure of the pipe samples was noted to make the process unstable, and the curves representing a change in the characteristic values under study, depending on the immersion time in diesel fuel, tended to decrease throughout the entire immersion period. The experiments have shown that in the study of samples absorbing capacity a full saturation was obtained when immersed in diesel fuel and, despite large difference in absorbance values, the volume of absorbed hydrocarbons caused decline close to the studied characteristic values. Motor oils produced the most significant effect on the HDPE samples studied characteristics at the relatively low absorption values.

The goal of this research is to carry out a 3-dimensional finite detail approach evaluation of a composite plate cracked under thermal loading. The results of the mechanical properties of the composite, the orientation angle of the fibers, the geometric form of the plate, the thermal loading and the crack length had been studied to show their influence on the variation of the integral J. It is concluded that the integral J increases with the increase of crack size, temperature variation and reduce in fiber orientation perspective (e). To complete the work a probabilistic analysis was carried out.

High and low density polyethylene materials constitute about 48% of total weight of plastics waste in Europe, that depends on the frequent use of these materials in packaging applications. This paper analyze the recycling effect on the mechanical properties of high and low density polyethylene (HDPE and LDPE). A mechanical recycling process was tested for the plastics waste of high and low density polyethylene, then a tensile and impact tests were performed on different mixing ratios for each of the both materials ranging from 100% of the virgin material and up to 100% of the recycled material with a difference of 10% of the sample to the other. This paper discusses the tensile properties of tensile stress at the fracture, elongation and modulus of elasticity and the impact test results for HDPE and LDPE were compared with each other.