Volume 8 (2008): Issue 2 (June 2008)

Mechanical surface treatments such as shot peening or ball-burnishing induce high dislocation densities and residual compressive stresses in near-surface regions. In addition, the surface roughness is changed. Micro-hardness and residual stress-depth profiles are evaluated in Ti-6Al-4V as a function of the Almen intensity being the main process parameter in shot peening. In the finite life regime, residual compressive stresses are shown to drastically increase the fatigue life by retarding crack growth from the surface into the interior. However, in the HCF regime a shift in crack nucleation site occurs from the surface to subsurface regions where residual tensile stresses balance the outer compressive stress field. Therefore, the tensile mean stress sensitivity of the fatigue strength which can largely vary in Ti-6Al-4V needs to be taken into account in order to understand the observed differences in HCF responds to shot peening.

The weldability aspects of the some advances materials, such as Titanium and its alloys: Titanium Aluminide - Intermetallics, still require further research and development. The power beam welding processes are considered in this work since these processes are capable of joining a wide range of new materials of interest in aerospace industry as well as in the many other industrial applications and offer remarkable advantages over conventional fusion welding processes. In this paper have been defined the following questions: - the weldability of Ti and its alloys, a new class of titanium alloys and their weldability, welding metallurgy and processes for joining.

The Gamma nail (fixator) made of stainless steel, which has broken in the body, was subjected to examination. The fixator was removed from the patient femur. The fracture occurred in the area of the nail hole after two months' stay in the organism. The research included chemical composition, hardness of the Gamma nail material and the observation and analysis of the type of fracture. The research showed the fatigue failure of the Gamma nail.

The problems concerning re-operations after joint implantation, as well as the occurrence of postoperation complications with trauma-orthopedics patients, who were given metal implants are constantly considered from medical and economical point of view. The most frequent reason for the re-operation is so called: aseptic loosening arthroplasty. The article presents the analysis of various clinical postoperation complications after the long-bone treatment by means of osteosynthesis with the use of metal implants and hip arthroplasty.

The characteristic features of surface cracking observed after laser melting with CO₂ and Nd:YAG laser were described. The cracks were always present, their length approaching some part of melted zone and scarcely dependent on laser melting conditions. The appearance of cracks was attributed mainly to martensitic transformation within the surface layer. The possible contribution of developed thermal stresses cannot be also excluded. The existence of cracks may be utilized for the enhancement of bone - implant strength.

This paper presents verification of the numerical model of a cracked beam against the experimental results. Presented investigation assesses the adequacy of a crack model incorporated in the ABAQUS commercial FEM package. Structure under investigation is a square hollow steel section. Experimental and numerical modal model parameters like mode shapes and natural frequencies were compared. Obtained results confirm the high level of confidence for the numerical model of the crack. This observation constitutes application of crack model in the computations of more complex structures.