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Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body. In this work, the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes (20 ∼ 150 MPa) were studied. It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated. The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads. A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established. The corrosion current density (i corr) of Mg alloy and the applied static stress (σ) matches a linear relationship of ln i corr ∼ σ well during the early stage (within 24 hrs) while deviated gradually in the latter period of corrosion. This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads. [ABSTRACT FROM AUTHOR]

Screw micropiles or "ground screws" (diameter less than 200 mm, length less than 5 m) consist of a steel tubular shaft with continuous spiral threads, and a threaded tapered segment; the installation is achieved by rotary driving. Although ground screws are useful in many applications as well as environment-friendly, research on their behaviour is limited. The paper presents an experimental study on the response of screw micropiles subjected to tensile and compressive axial loading. Twenty full-scale load tests were conducted on four types of screws, with diameter 66-114 mm and length 0.8-1.6 m, at a test site in Italy, characterized by the presence of predominantly clayey soils. The micropiles achieved tensile and compressive capacities of 23-60 kN and 20-75 kN respectively, with pile movements in the range 1-9 mm. The results were interpreted in the light of a recently developed method to compute bearing capacity of screw micropiles. [ABSTRACT FROM AUTHOR]

Uniaxial tensile tests were carried out on T2 pure copper plate and H62 copper alloy subjected to identical heat treatment. The influences of different strain states on the damage degree of both materials were analyzed. It is found that the fracture and damage of T2 pure copper and H62 copper alloy are closely related to their microstructure under tensile loading. The shape factor of the studied materials shows a similar variation trend with increasing strain, while shape factor for H62 copper alloy is larger than that for T2 pure copper. Evolution of relative shape factor for the studied materials shows very similar variation. In the present work, a damage variable of shape factor of grains was put forward to quantitatively describe the character of microstructure; its evolution with the plastic deformation was built-up by micro-analytical and mechanical experiments for T2 pure copper plate and H62 copper alloy. By virtue of exponential function, the normalized shape factor curves of the studied materials were fitted and the fitting equations were established, which reveals the relationship between the macroscopic deformation and microstructure of materials. [ABSTRACT FROM AUTHOR]

The paper deals with method for dynamic experiment of parts of car radial tyres. The aim of research work of authors is also propose and evaluate the experimental procedures for cyclic loading of selected parts of tyres with textile reinforcement and rubber matrix. The universal testing device Autograph AG-X plus 5 kN – Schimadzu with video-extensometer with test mode Control of software Trapenzium X was used for experiments. The five cycle loop were used. Every cycle loop consisted of five cycles, every cycle is defined as loading to certain percent of elongation and unloading to certain percent of elongation. The fifth cycle can be used as steady state for comparison of behaviour between specimens with different cord angle. Knowledge about characteristics of dynamic experiment such as cyclic tensile loading is necessary for the verification analysis between experiments and computational modeling of tyres by FEA. Also the determination of material parameters from experimental data will be used as input data to computational modeling of tyres. The results will be also applied in the case of the composites with the woven and nonwoven textile reinforcement and moreover, these results can be used in such conditions where the mentioned composites are exposed to the cyclic loading at unsteady temperature: tyre casing, conveyor belts, etc. [ABSTRACT FROM AUTHOR]

The present work shows the effect of weld penetration levels on the stress level and the fatigue life at the weld joints. Finite element analysis was used to estimate stress pattern of welded joints having different levels of penetration for “Bend Loading” and “Tensile loading” were selected for studies. Specimens with variation in the penetrated throat length between 1.80 mm to 0.60 mm were selected. Study has clearly highlighted the corresponding fluctuations observed in the fatigue life with change in weld penetrations. A side loading will be more detrimental than a tensile loading [ABSTRACT FROM AUTHOR]

Summary: Objective: The cell morphology, gene expression, and matrix synthesis of articular chondrocytes are known to vary with depth from the tissue surface. The objective of this study was to investigate if chondrocytes from different zones respond to in vitro oscillatory tensile loading in distinct ways and whether tensile strain, which is most prevalent near the articular surface, would preferentially stimulate superficial zone chondrocytes. Design: Chondrocytes were separately isolated from the superficial, middle, and deep zones of articular cartilage and seeded into three-dimensional fibrin hydrogel constructs. An intermittent protocol of oscillatory tensile loading was applied for 3 days, and the effects on extracellular matrix (ECM) synthesis were assessed by measuring the incorporation of radiolabed precursors, size exclusion gel chromatography, and western blotting. Results: Tensile loading was found to be a potent stimulus for proteoglycan synthesis only in superficial zone chondrocytes. Although overall biosynthesis rates by deep zone chondrocytes were unaffected by tensile loading, the molecular characteristics of proteins and proteoglycans released to the culture medium were significantly altered so as to resemble those of superficial zone chondrocytes. Conclusions: Oscillatory tensile loading differentially affected subpopulations of articular chondrocytes in three-dimensional fibrin hydrogel constructs. Cells isolated from deeper regions of the tissue developed some characteristics of superficial zone chondrocytes after exposure to tensile loading, which may indicate an adaptive response to the new mechanical environment. Understanding how exogenous mechanical stimuli can differentially influence chondrocytes from distinct tissue zones will yield important insights into mechanobiological processes involved in cartilage tissue development, maintenance, disease, and repair. [Copyright &y& Elsevier]

Countersunk rivets are used to join components to achieve aerodynamic or hydrodynamic surfaces. At countersunk holes, three dimensional stress and strain concentrations occur. Previously, the present authors developed a three dimensional equation for the stress concentration factor Kt through a detailed finite element analysis. This paper extends the study to include an equation for three dimensional strain concentration factor Ktε using a similar approach. The resulting equation was verified by finite element analysis for a wide range of countersunk hole configurations and plate sizes. Results showed that the maximum strain concentration is at the countersunk edge. The developed equation is within 5 per cent of the finite element results for all practical cases. It was also found that the Ktε and Kt expressions are similar and Ktε≤Kt. The maximum difference between the two is 8 per cent (for ν = 0.3) or ν2 for straight shank holes and about ν2/2 for countersunk holes. The proposed equation is a valuable tool for strain based design of structural elements. [ABSTRACT FROM AUTHOR]