337 publications from this institution
In this paper, chip formation process during mechanical cutting of rock is simulated by using an explicit finite element code, LS-DYNA. In the simulation, the work-piece material properties have been modeled using the damage constitute material model. This model simulates the separation of the chip from the work-piece and the simultaneous breakage of the chip into multiple fragments. In the simulation, a rigid steel tool was moved at various sliding velocities, namely 1, 4, 10, 50 and 100 mm/s against a stationary rock material. For a given sliding velocity, the simulations were carried out for various cutting depths, namely 1, 2, 3 and 4 mm. The variation of stresses and the amount of chip formation at different depths of cut and velocities have been investigated. Overall, the results indicate that the explicit FEM is a powerful tool for simulating rock cutting and chip formation. More specifically, the separation of chip from the work-piece at different depths of cut was distinctly shown using this numerical model.
There is a critical need for engineers to move away from using conventional petroleum-based oils and lubricants in mechanical systems due to their environmental impact. As the first book dedicated to multifunctional bio-based lubricants, this reference text provides detailed coverage on all aspects of the field, including the need for these lubricants and their performance, the synthesis and design routes, and their valuable multifunctional properties. The environmental benefits and superior properties of these lubricants are covered. With sustainability as a key focus, the book raises awareness of the need to develop bio-based lubricants with a lower environmental footprint than traditional lubricants, covers methods for synthesising lubricants from waste plastics (an emerging technique) and discusses suitable techniques for their eventual disposal. Key features • First research book dedicated to multifunctional bio-based lubricants. • Provides detailed coverage on the performance, synthesis and design of these lubricants. • Covers the environmental benefits and superior properties. • Discusses the future market based on the potential applications. • Covers disposal techniques and methods for synthesising lubricants from waste plastics.
Aluminum metal matrix composites are a class of advanced materials which have been developed for weight-critical applications in the aerospace and automotive industries. In the present investigation, tribological performance of aluminum micro- (100 to 200 μm particle size) and nano- (47 nm particle size) composites was studied using a three pin-on-disk apparatus under dry sliding conditions. As a basis for comparison, the tribological performance of aluminum alloys was also studied. The pins made of these materials were then slid against a steel disk under ambient conditions. Tests were conducted at a sliding velocity of 1.58 m/s for a normal load of 30 N. The worn surfaces of the pins and weardebris were analyzed using a scanning electron microscope. Based on the experiments, it was observed that the nano-composites significantly outperformed all of the other materials with respect to friction levels. It was also discovered that the nano-composites exhibited the best wear performance among the composites...
Abstract In recent years, cold spray additive manufacturing (CSAM) has become an attractive technology for surface modification and protection. However, due to the intrinsic porous nature of CSAM coatings, they suffer from rapid material degradation due to premature brittle fracturing induced by tribological interactions. In this work, laser shock peening (LSP) was utilized as a post-processing technology to mitigate the surface porosity and augment the surface characteristics of CSAM 316L stainless steel (SS). Due to the synergistic influence of severe plastic deformation and rapid surface heating, the surface porosities were effectively healed, thus reducing the surface roughness. Combined with the surface-strengthening effects of LSP, the frictional resistance and transfer layer formation on the CSAM LSP surfaces were reduced. The underlying mechanisms for these findings were discussed by correlating the atomic, microstructural, and physical features of the LSP surfaces. Based on these findings, it can be suggested that LSP is indeed a useful technique to control the surface characteristics of CSAM 316L SS coatings.
Tribological interaction between two contacting surfaces is influenced by many factors such as relative motion, normal load, environment, and lubrication apart from surface characteristics of the mating surfaces. Though surface characteristics such as roughness was dealt by many researchers for decades, the other important characteristic of surfaces, surface topography, has not got its share of attention. In the present investigation, basic studies were conducted using Inclined Scratch Tester to understand the role of surface topography on friction and transfer layer formation. A tribological couple made of copper pin against EN8 flat was used in the tests. Two surface parameters of steel flats — roughness and texture — were varied in tests. Care was taken to ensure that the surface roughness, measured along the scratch direction, had similar values for different textures, namely Unidirectional, 8-ground, and Random. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely adhesion and plowing, are controlled by the nature of surfaces and are independent of surface roughness. The plowing component of friction was highest for the surface that promotes plane strain conditions near the surface and was lowest for the surface that promotes plane stress conditions near the surface.
Surface texture influences friction and transfer layer formation during sliding. In the present investigation, basic studies were conducted using inclined pin-on-plate sliding tester to understand the effect of directionality of surface grinding marks of hard material on friction and transfer layer formation during sliding against soft materials. 080 M40 steel plates were ground to attain different surface roughness with unidirectional grinding marks. Then pins made of soft materials such as pure Al, pure Mg and Al-Mg alloy were slid against the prepared steel plates. Grinding angle (i.e., the angle between direction of sliding and grinding marks) was varied between 0° and 90° in the tests. Experiments were conducted under both dry and lubricated conditions on each plate in ambient environment. It was observed that the transfer layer formation and the coefficient of friction, which has two components — adhesion and plowing — depend primarily on the directionality of grinding marks of the harder mating surface, and independent of surface roughness of the harder mating surface. For the case of pure Mg, stick-slip phenomenon was observed under dry condition for all grinding angles and it was absent upto 20° grinding angles under lubricated condition. However, for the case of Al, it was observed only under lubricated conditions for angles exceeding 20°. As regards the alloy, namely, Al-Mg alloy, it was absent in both conditions. For the case of pure Mg and Al, it was observed that the amplitude of stick-slip motion primarily depends on plowing component of friction. The grinding angle effect on coefficient of friction was attributed to the variation of plowing component of friction with grinding angle.
