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This paper presents development of numerical models for simulation of the behaviour of titanium alloy hip implants under static and dynamic loads, which is a part of extensive research involving the structural integrity of such implants under various loading conditions, as well as under exposure to aggressive environments. Numerical models were created in ABAQUS and ANSYS software packages, in order to determine the stress/strain distribution, the number of cycles to failure and stress intensity factors, for two different hip implant geometries. The ABAQUS models were used for static and ANSYS models for dynamic loads. The next stage in this analysis involved comparing these two cases, to determine the one with the better behaviour, depending on the exploitation conditions, which can greatly vary between different groups of patients. The targeted patient weight for all numerical simulations was 90 kg, while failure assessment diagrams were made for both implant geometries, assuming a crack length of 1 mm.

Corrosion effects on structural integrity and life of oil rig welded pipes are analysed by experimental, analytical, and numerical methods. Experiments were performed using standard tensile specimens and CT specimens for static loading, Charpy specimens for impact loading, and 3 Point Bending specimens for fatigue crack growth with amplitude loading. In each case new and old pipes were used to evaluate corrosion effects. Results indicated negligible corrosion effects in the case of tensile properties and impact toughness, and strong effects in the case of fracture toughness and especially fatigue crack growth rates, increasing the risk of static failure and reducing significantly structural life. Analytical expressions are used for oil rig pipe structural integrity and life assessment to quantify these effects. Recently introduced risk-based approach is applied to analyse oil rig drill pipe with a corrosion defect treated as a surface crack.

Welded joints are analysed as critical regions in a pressure vessel in respect to structural failure due to the elastic-plastic fracture/crack growth. To assess structural integrity of pressure vessels used in chemical industry the risk based procedure has been introduced and applied in the case of a large spherical pressure vessel used as a vinyl-chloride monomer (VCM) storage tank in HIP Azotara Pančevo. The risk matrix has been used, taking into account the basic definition of risk, being the product of the probability and consequence, and applied to different regions of welded joints, having different mechanical properties, i.e. crack resistance. To estimate probability, the failure assessment diagram (FAD) has been used, as an engineering tool, defined according to the position of the operating point for different regions of the welded joint, relative to the critical point on the limit curve. Generally speaking, consequence is estimated based on pressure vessel parameters, or by detailed analysis of health, safety, business and security issues, but in the analysed case, the worst case scenario is assumed, with the highest consequence due to potential disaster for environment and fatalities. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 33044 and Grant no. 35017]

In this paper is presented a theoretical-experimental analysis of the aluminum-copper joining by friction welding. Considering that such Al-Cu bimetal joints are widely applied in industrial practice, experimental analysis in this paper was performed on the concrete elements used in electronics. The fact that the joining is done of the two dissimilar materials points to complexity of the problem, since phenomena that appear in the joint zone extremely influence physical, mechanical and structural properties of the welded/base metals. Besides the theoretical analysis of the basic phases and mechanisms of the friction welding process, the research also included experimental analysis of the geometry changes due to the plastic deformation, the change of microstructure and hardness in the joint zone, as well as of the basic mechanical properties of the Al-Cu joint, such as tensile strength. This paper presents some significant results, which point to the possibility for realization of the reliable joints of the two dissimilar metals.

This paper presents different aspects of pressure vessel safety in the scope of industrial safety, focused to the chemical industry. Quality assurance, including application of PED97/23 has been analysed first, followed shortly by the risk assessment and in details by the structural integrity approach, which has been illustrated with three case studies. One important conclusion, following such an approach, is that so-called water proof testing can actually jeopardize integrity of a pressure vessel instead of proving it. [Projekat Ministarstva nauke Republike Srbije, br. TR 174004 i br. TR 33044]

Investigation of risk in complex industrial systems, as well as evaluation of main factors influencing decision making and implementation process using large petrochemical company as an example, has proved the importance of successful project risk management. This is even more emphasized when analyzing systems with complex structure, i.e. with several organizational units. It has been shown that successful risk management requires modern methods, based on adequate application of statistical analysis methods.

New optical stereometric methods are becoming commonplace in investigations of mechanical behaviour of biomaterials. An understanding of the mechanical behaviour of hard and soft tissues is of great importance in the design and investigation of biomaterials. The mechanical behaviour of biomaterials can be evaluated using a number of methods that are based on either contact or non-contact schemes for displacement measurement. The method for full-field measurement of strain is done by using the ARAMIS three-dimensional image correlation system. The system uses two digital cameras that provide a synchronized stereo view of the specimen and the results show the complete strain field during the tests. Several examples are presented that highlight the use of stereometric measuring system for modern biomaterials. It is shown that this measuring methodology can capture the trends of the experiments.

The effect of MIG/MAG shielding gas on the toughness of aluminium alloy AlMg4.5Mn weld metal has been analyzed using the instrumented Charpy pendulum for standard toughness testing. The MIG/MAG welding was performed in the shielded atmosphere of Ar, as well as the mixtures of gases Ar + 0.0307 % O2, Ar + 30 % He + 0.0317 %O2 and Ar + 48 % He + 0.0290 % O2. Metallographic tests have been performed in order to check the appearance and porosity of the weld metal, as well as its toughness testing at different temperatures (20, - 90, - 196 °C), using the instrumental Charpy pendulum, in order to separate the crack initiation and crack growth energy. In this way, a comprehensive insight of the effect of shielding gas on the weld metal toughness has been obtained.

Ductile fracture initiation in high-strength low alloyed welded steel joints is predicted using micromechanical complete Gurson model (CGM). The crack tip constraint and variation of stress triaxiality in ligament are considered on single-edge notch bend SE(B) and compact tension C(T) specimens, including the effect of strength mismatching and different weld metal width. According to the analysis of stress triaxiality in front of the crack tip, transferability of fracture initiation parameter was studied. As a result of the analyses on specimens, fracture initiation parameter determined by using CGM can be transferred from one geometry to another if their triaxial conditions are found to be similar.

Testing were carried out on two steels. The first was microalloyed with Nb and second with Ti, Nb and V. The impact toughness of weld metals of these steels was evaluated using an instrumented Charpy pendulum. Five different gas mixtures (Ar, CO2, O2) were used to determine the optimal gas shielded metal arc process for both steels. The oxygen equivalent was used as a representative parameter of a mixture to follow, in particularly, its effect on the microstructure, toughness and crack propagation energy of the weld metal. For these investigated steels, the optimum gas mixture was established (5%CO2, 0.91%O2, balance Ar), which provided the maximum crack propagation energy, due to the microstructure which consisted dominantly of acicular ferrite.

Fracture behavior of a structure having a crack in the middle of a weld is influenced by the mechanical properties of the welded joint constituents (weld metal, base metal, heat-affected-zone) and their geometry. Therefore, defect assessment procedures have been developed in order to take into account all those affecting parameters. One of the key point for all those defect assessment procedures is to have limit load solutions of the mismatch structure. Such limit load solutions have been obtained by using 3D finite element solutions for different configurations such as plate with surface crack in tension or pressure vessel with axial external surface crack exposed to internal pressure, since those limit load have been obtained for non-hardening material exponent.

Numerical simulation of fatigue crack growth in welded joints is not well represented in the literature, especially from the point of view of material heterogeneity in a welded joint. Thus, several case studies are presented here, including some focusing on fracture, presented by two case studies of mismatched high-strength low-alloyed (HSLA) steel welded joints, with cracks in the heat affected zone (HAZ) or in weld metal (WM). For fatigue crack growth, the extended finite element method FEM (XFEM) was used, built in ABAQUS and ANSYS R19.2, as presented by four case studies, two of them without modelling different properties of the welded joint (WJ). In the first one, fatigue crack growth (FCG) in integral (welded) wing spar was simulated by XFEM to show that its path is partly along welded joints and provides a significantly longer fatigue life than riveted spars of the same geometry. In the second one, an integral skin-stringer panel, produced by means of laser beam welding (LBW), was analysed by XFEM in its usual form with stringers and additional welded clips. It was shown that the effect of the welded joint is not significant. In the remaining two papers, different zones in welded joints (base metal—BM, WM, and HAZ) were represented by different coefficients of the Paris law to simulate different resistances to FCG in the two cases; one welded joint was made of high-strength low-alloyed steel (P460NL1) and the other one of armour steel (Protac 500). Since neither ABAQUS nor ANSYS provide an option for defining different fatigue properties in different zones of the WJ, an innovative procedure was introduced and applied to simulate fatigue crack growth through different zones of the WJ and evaluate fatigue life more precisely than if the WJ is treated as a homogeneous material. [ABSTRACT FROM AUTHOR]