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Generally, implants fixations in orthopedic surgery are insured by bone cement; which is generated mainly from polymer polymethylmethacrylate (PMMA). Since, the cement is identified as the weakest part among bone-cement-prosthesis assembly. Hence, the characterization of mechanical behaviour is of a crucial requirement for orthopaedic surgeon’s success. In this study, we investigates the failure behaviour of bone cement, under combined shear and compression loading, for the aim to determine the strengths of bone cement for different mode loading conditions. Therefore, experimental cylindrical specimens has been tested to assess different shear-compression stresses. Based on the mechanical tests, a finite elements model of cylindrical specimens was developed to evaluate stresses distribution in the bone cement under compression, shear and combined shear-compression loading. Results show that, the load which leading to the failure of the cement decreased with increasing of the specimen angle inclination with respect of loading direction.

Friction stir spot welding (FSSW) is a very important part of conventional friction stir welding (FSW) which can be a replacement for riveted assemblies and resistance spot welding. This technique provides high quality joints compared to conventional welding processes. Friction stir spot welding (FSSW) is a new technology adopted to join various types of metals such as titanium, aluminum, magnesium. It is also used for welding polymer materials which are difficult to weld by the conventional welding process. In various industrial applications, high density polyethylene (HDPE) becomes the most used material. The parameters and mechanical properties of the welds are the major problems in the welding processes. In this paper, we have presented a contribution in finite element modeling of the friction stir spot welding process (FSSW) using Abaqus as a finite element solver. The objective of this paper is to study the HDPE plates resistance of stir spot welding joints (FSSW). First, we show the experimental tests results of high-density polyethylene (HDPE) plates assembled by friction stir spot welding (FSSW). Three-dimensional numerical modeling by the finite element method makes it possible to determine the best representation of the weld joint for a good prediction of its behavior. Comparison of the results shows that there is a good agreement between the numerical modeling predictions and the experimental results.

This research paper aims at studying the friction stir spot welding (FSSW) some of thermoplastic polymer materials (HDPE and HDPE-PMMA) using a specifal geometry tool without a pin. The effect of the tool geometry on the welds static resistance was studied via several tool shape, a flat shape below the tool, a shape with concavity angles ranging from 0° to 16° , a flange shape of the sharp-edged tool, a chamfered flange shape and a rounded shape. This work is done to increase the surface area of the weld and further to maximize the static strength of the friction stir spot welding. Experimental tests have been carried out under various operational parameters such as the tool rotation speed, tool plunge depth and dwell time. This later has been carried out to highlight the effect of the tool’s geometry and the operational parameters of the welding on the surface in virtue on static resistance of the friction stir spot welding of thermoplastic polymers. Tests of lap-shear at speed of 5m/s have showed that the tool geometry plays a very important part. This study shows that a FSSW welding tool with 4° concavity angle tool and a rounded flange shape gives the best welding quality for the polymers studied.