Mechanical Testing

It is the objective of this article to investigate the influence of surface preparation on the cold roll bonding (CRB) process. In this context, the effects of surface preparation parameters consisting of surface preparation method, surface roughness, scratch-brushing parameters, and the delay time between surface preparation and rolling are investigated on the bond strength of aluminum strips. The bond strength of two adjacent aluminum strips produced by the CRB process is evaluated by the peeling test. Furthermore, the interface region is investigated by metallographic observations. Our findings indicate that higher surface roughness values and shorter delay times improve the bond strength. It is also found that degreasing followed by scratch-brushing yield the best bonding properties.

Effect of the aqueous chemistry on the mechanical strength of chalk has extensively been studied during the last decade. At high temperatures (~130°C), chalk exposed to seawater is significantly weaker compared to chalk exposed to distilled water when considering the hydrostatic yield strength and the following creep phase. The explanation of these experimental results must be of a chemical nature, as the density and viscosity of the aqueous phase vary little among these different brines. We present the results from simplified aqueous chemistry using MgCl2 brines, and compare these results with seawater. Previous studies show that different ions, e.g. Ca2+, Mg2+, \({{\rm SO}{_{4}}^{2-}}\) in the injected brine, as well as the chalk mineralogy have an impact on the stability of the rock. We performed mechanical tests on chalk cores from Liège and Stevns Klint; it was found that these two outcrop chalks exhibit an unexpected difference in their mechanical responses when comparing cores flooded with NaCl and MgCl2 at 130°C. The results of this study show that the effects of magnesium seem to be governed not only by the differences in mineralogy, but also a time dependency on chalk deformation is additionally observed. Independent of the chalk type tested, the chemical analyses performed show that when MgCl2 is flooded through the core, a significant loss of magnesium and a considerable additional amount of calcium are detected in the effluent. The experimental observations fit very well with the time-dependent chemical changes gained from the mathematical model of this study that accounts for transport effects (convection and molecular diffusion) as well as chemical processes such as precipitation/dissolution. Based on the calculations and chemical analyses, we argue that the loss of magnesium and the production of calcium cannot solely be a consequence of a substitution process. The calculations rather indicate that magnesium is precipitated forming new mineral phases and in this process not only calcite, but also silicates are dissolved. The amount of dissolved calcium and silicon from the rock matrix is significant and could thus cause an additional deformation to take place. Both the retention of magnesium in the chalk core and the formation of newly precipitated magnesium-bearing carbonates and/or magnesium-bearing clay-like minerals after flooding with MgCl2 brine were demonstrated using scanning electron microscopic methods. In addition, precipitation of anhydrite as a result of flooding with seawater-like brine was proven. The water-induced strain not only depends on the ion composition of the injected brine; moreover, the presence of non-carbonate minerals will most likely also have a significant influence on the mechanical behaviour of chalk.

Quantitative strength analysis of first metatarsophalangeal joint arthrodesis was performed using two fixation techniques: a small 6-hole plate with an interfragmentary screw or two crossed lag screws. Twelve matched-pair fresh-frozen cadaveric specimens (24 trials) were used for direct comparison of each of the two fixation techniques. All joint surfaces were prepared with power conical reamers utilizing a standard technique. The fixation construct was stressed to failure on each specimen using a computer-integrated materials tester. Fixation stiffness defined as force (load) over displacement and point of ultimate failure was evaluated. The six-hole plate and interfragmentary screw fixation method was a statistically stiff er form of fixation (p > .01) and displayed a greater point of ultimate failure (p > .002) under the laboratory conditions.

The influence of ionic substituents in calcium phosphates intended for bone and tooth replacement biomedical applications is an important research topic, owing to the essential roles played by trace elements in biological processes. The present study investigates the mechanical and biological evaluation of ionic doped hydroxyapatite/β-tricalcium phosphate mixtures which have been prepared by a simple aqueous precipitation method. Heat treating the resultant calcium phosphates in a carbonated atmosphere led to the formation of ionic doped carbonated hydroxyapatite/β-tricalcium phosphate mixtures containing the essential ions of biological apatite. The structural analysis determined by Rietveld refinement confirmed the presence of hydroxyapatite as the main phase, together with a considerable amount of β-tricalcium phosphate. Such phase assemblage is essentially due to the influence of substituted ions during synthesis. The results from mechanical tests proved that carbonate substitutions are detrimental for the mechanical properties of apatite-based ceramics. In vitro proliferation assays of osteoblastic-like cells (MC3T3-E1 cell line) to powders revealed that carbonate incorporation can either delay or accelerate MC3T3 proliferation, although reaching the same proliferation levels as control cells after 2 weeks in culture. Further, the powders enable pre-osteoblastic differentiation in a similar manner to control cells, as indirectly measured by ALP activity and Type-I collagen medium secretion.

Mechanical loading has been shown to modulate longitudinal bone growth and cellular activity of the growth plate. Nevertheless, limited and controversial results exist regarding the effect of exercise on a physiological level on the growth plate. The present study investigated whether dose-dependent voluntary exercise has an influence on morphological, biochemical, and mechanical factors of the distal femoral growth plate of

To remove the environmental and safety hazards associated with power transformers, the authors have investigated the use of liquid nitrogen as a replacement for transformer oil. This paper details tests performed to determine new design rules and efficiency expectations of liquid nitrogen filled power transformers (Enviro-Transformers). The tests include dielectric strength testing of liquid nitrogen and mechanical strength testing of

The effect of binder properties on torque curves, granule growth kinetics, wet mass consistency and dry granule strength has been investigated in this study. Granulation runs have been performed on a fine cohesive microcrystalline cellulose powder (Avicel 105, d50=20μm) in two types of laboratory high shear mixers: a Mi-Pro high shear mixer using a 1.9L bowl and a 6L Diosna

Shrinkage stress, degree of cure and mechanical properties are contradicting properties, forcing to a compromise between an adequate curing and low stress at the interface tooth-restoration. The purpose of this study was to quantify this relations for a micro-hybrid composite, by analysing in real time the development of degree of cure at depths of 2 and 6 mm, shrinkage stress and curing time until gelation, as well as the variation of micro-mechanical properties with depth, after curing with 13 regimes of one halogen and two light-emitting diode (LED) curing units. A nano-dynamic mechanical test was additionally performed on selected regimes (Ramp, Pulse and Fast Cure) of the same curing unit. The present study showed that the soft-start polymerization concept is still valid for less deep cavities (2 mm), even by curing with high-power LED curing units, since a soft-cure polymerization resulted in a delayed gel point and a lower shrinkage stress, keeping simultaneously the degree of cure and mechanical properties constant. At 6 mm depth, curing with soft-start regimes resulted in a significant decrease in degree of cure, although this decrease was less than 10%, while the mechanical properties were maintained.

Hydroxyapatite (HAp) is a potential material for various biomedical applications. In the present study, an attempt has been made to synthesize this material using simpler and cheaper method of solid-state-reaction process. Samples were prepared by mixing the ingredients and ...