Extensive Internal Damage Research Articles

Comparative evaluation of 4-cylinder CI engine camshaft based on FEA using different composition of metal matrix composite

The Camshaft is a vital part of the Internal Combustion engine of automobiles. It functions as a timing mechanism that controls the opening and closing of the inlet and exhaust valves, as well as the valve overlap that occurs at the TDC of the exhaust stroke. The camshaft is made up of several journals that run on bearings within an engine. The camshaft is bound to rotate with the crankshaft by either a set timing gear, timing belt, or timing chain. As the camshaft drive fails, the valves and piston crowns come into contact, causing extensive internal damage. For high-speed diesel engines (Compression Ignition), power impulses have a greater value than spark-ignition engines in multi-cylinder configurations. In this study, a comparative analysis of an existing automobile camshaft of four-stroke, a four-cylinder Compression Ignition (CI) engine made of Cast Iron was carried out with different compositions of metal matrix composites. For this condition, the outcomes were taken as Von-Mises stresses and displacement values for the static state of the camshaft. The modal analysis (Free vibration) was performed using ANSYS after the static analysis results were obtained. Finally, comparing all the results obtained for different materials, the AlSiC 20% metal matrix composite has been recommended as the most suitable material for the production of camshafts which can replace cast iron because of its similar behavior as to cast iron. This will aid in the development of more precise camshafts, which will be useful for larger displacement engines.

Effect of Baltic Seawater and Binder Type on Frost Durability of Concrete

AbstractThe effects of Baltic seawater on frost durability of PC concretes using sulfate resistant portland cement and combination of rapid hardening portland cement with silica fume were studied. The freeze-thaw cycles were performed on specimens exposed to the Baltic seawater, 3% sodium chloride solution and deionized water. The freeze-thaw cycles appeared to cause the most extensive internal damage in specimens based on sulfate resistant cement (SR) and exposed to seawater. The most extensive surface scaling was observed in the case of concretes containing silica fume and exposed to deicing salts. Based on the thermo gravimetric and X-ray diffraction analyses it was concluded that extensive internal damage of concrete based on SR was caused by changes of the microstructure due to secondary formation of ettringite, carbonation, and formation of calcite. The results showed also that low C3A content of the SR did not fully mitigate formation of secondary ettringite during freeze-thaw cycles. A combination...

X‐ray scattering study on the damage in fibers used in soft body armor after folding

AbstractThe goals of the research effort described in this article are to develop a framework to evaluate improvements in next‐generation fibers used in soft body armor and to anticipate long‐term performance and potential fiber deterioration. This effort to date has included the effect of folding on the fibers and exploring the interaction between the specific fiber strain energy and their sound velocity. Previous work in this lab noted a severe drop‐off of tensile strength and strain‐to‐failure in poly(p‐phenylene benzobisoxazole) (PBO) fibers when subjected to repeated folding. Subsequent work on poly(p‐phenylene terephthalamide) (PPTA) fibers showed at most a slight drop‐off in these mechanical properties. Results from wide angle X‐ray diffraction indicated that both PPTA and PBO fibers showed no significant changes in the d‐spacing and the apparent crystal size. However, with small angle X‐ray scattering, it was found that the void and fibril sizes within PBO fibers may decrease after folding. Environmental scanning electron microscopy showed no damage to the fiber surfaces upon folding, and confocal microscopy revealed extensive internal damage to the PBO fibers that tracks well with the SAXS and mechanical testing results. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Moisture intrusion in viscoelastic porous media: Induced-stress and deformation

Porous media exposed to humid air absorb moisture which can lead to extensive internal damage and failure. In this paper, we analyze numerically the influence of the moisture intrusion in a two-layer viscoelastic porous media. The relationship between air humidity and moisture content inside the porous media was examined. It was also found that the local stress increases with the exposure time to humid air but decreases with initial moisture content of the porous medium. Furthermore, the stress components were tensile at the centre of the medium and compressive near the medium surface. The ultimate strength of the medium was only exceeded for the stresses in axial and tangential directions.

Full-Scale Testing and Analysis for Blast-Resistant Design

A full-scale blast test was conducted on a structure representing a mailroom, constructed with unreinforced masonry walls. The four walls were retrofitted with different quantities of glass fiber-reinforced polymers (GFRP) on the outside face to increase their resistance to the blast load. In addition, shotcrete was added to the inside face of the two long walls. The objective of this test was to validate a method of analysis that can be used to design effective retrofit techniques to contain blast loads. A blast load was produced by the detonation of a 0.91 kg (2 lb) equivalent TNT charge placed near the center of the room. Instrumentation on individual walls monitored the blast pressure and the consequent displacement and velocity of the walls. Although the walls sustained extensive internal damage and plastic deformation, the retrofit was able to withstand the blast load. It was observed through the postmortem analysis of the test that the stiffness of the walls is completely lost at an early stage and...

Stress—strain behaviour of laterally confined concrete columns

An empirical formulation of the stress–strain relationship of laterally confined concrete columns is derived from axial compression tests on short concrete columns, reinforced only with lateral layers of orthogonally placed HTS (high–tensile steel) bolts. Several factors considered likely to influence the behaviour of the columns were studied. It was found that the longitudinal tangent stiffnesses of the columns degraded as the columns were loaded, with the relationship between stiffness degradation and axial strain of a bilinear form, with gradients governed by the type of confinement. Empirical relationships were developed which allowed the stress–strain relationship for each column to be predicted. For the set of data analysed, the predicted curves fitted well with the experimental curves. The two–stage stiffness degradation in the columns demonstrated a general two–stage deformation in the concrete—the first at low loads when the concrete was relatively intact, and the second at higher loads and up to ultimate, when the concrete had suffered extensive internal damage with confinement from mobilization of the lateral reinforcement.