AN ABSTRACT OF THE THESIS OF ROHIT JOGINEEDI, for the Master of Science degree in Mechanical Engineering and Processes, presented on 11/06/2017, at Southern Illinois University Carbondale. TITLE: DEVELOPMENT OF COMPARATIVE WEAR TEST FOR ASTM G75 STANDARD MAJOR PROFESSOR: Dr. Peter Filip Industries related to tribology field invest huge amounts in testing products they handle. Most of their budget goes into running tests on corresponding friction, wear or lubrication testing instruments. These tests are observed to be consuming more time with an increase in operational costs. This gained importance among industries for developing economical testing methods designed to run on one or more machines to study tribological conditions. As friction and wear are system properties, change in system variables like distance, velocity, time and area can have notable impact on those properties. This paper discusses about various approaches to develop comparative test on sub scale testers for ASTM G75 standard. Scaling Laws of Physics and comparison of wear mode are two approaches used in this paper to justify the comparative test developed for ASTM G75 on a bench top tester developed by Bruker. Results from the ASTM G75 standard and the UMT are compared and concluded that scaling strategies cannot be used to replicate the standard test methods on sub scale testers but comparison of wear mode could help. This proposed comparative test for ASTM G75 is observed to have lower operational costs thereby decreasing the amount of investment on testing friction or wear products in an industry.

Based on the Lyapunov stability theorem, a model reference adaptive sliding mode control scheme is proposed in this thesis for a class of multi-input multi-output (MIMO) dynamic systems with mismatched model uncertainties and external disturbances in order to solve robust tracking problems. In this method, the adaptive mechanism is employed both in sliding surface function and control effort so that once the dynamics of the controlled system enters the sliding surface, the state trajectories of system can achieve asymptotical stability even if the mismatched perturbations exist. In addition, with an adaptive mechanism embedded in the proposed control scheme, the controller will asymptotically adapt the unknown upper bound of perturbations so that the information of upper bound of perturbations is not required. A numerical example and a practical experiment are given for demonstrating the feasibility of the proposed control scheme.

Based on Lyapunov stability theorem, a design methodology of nth order adaptive integral variable structure derivative estimator (AIVSDE) is proposed in this thesis. The proposed derivative estimator not only is an improved version of the existing AIVSDE, but also can be used to estimate the nth differentiation of a smooth signal which has continuous and bounded derivatives up to n+1. A low pass filter is cascaded with AIVSDE so that the effects of noise can be alleviated by adjusting the designing parameters of filter and AIVSDE. The adaptive algorithm is incorporated in the control scheme for removing the a priori knowledge of the upper bound of the observed signal. The stability of the proposed derivative estimator is guaranteed, and the comparison of upper bound of derivative estimation error between recently proposed nonlinear adaptive variable structure derivative estimator (NAVSDE) and AIVSDE is also demonstrated. An example is given for showing the applicability of the proposed AIVSDE.

Hypervelocity gouging occurs in high speed sliding systems such as rocket sled test tracks, light gas guns, and railguns. Gouging takes the form of teardrop-shaped craters on the rail surface, and usually only occurs above a threshold speed which is dependent on the slider and rail material properties. In this dissertation, the onset of gouging was studied from three perspectives: application of existing modeling techniques developed for gouging and related fields of research, performing new high-speed experiments using a medium-caliber railgun, and analyzing rail microstructural evolution during gouge onset. A previous gouging model based on shock mechanics was extended, while other models based on mechanisms such as Rayleigh waves, bending waves, and shear band formation were ruled out. An effective Reynolds number approach from explosive welding research was applied to gouging with encouraging results. Based on similarities between gouging, explosive welding, and Kelvin-Helmholtz waves, a linear instability analysis was also performed. A total of 22 railgun experiments were performed to explore different aspects of gouging. Through these experiments, the effect of new slider materials, thin aluminum coatings, and macroscopic rail indentations on the gouging of copper alloy rails were examined. Results using new materials matched the existing models well, though galling damage to copper rails was often as severe as gouging. Gouging was delayed using electroplated aluminum coatings as thin as 2 μm, though this is not necessarily a robust solution. Macroscopic indentations were found to have negligible effect on the threshold velocity for gouging onset, though the morphology of the gouges was strongly affected. Both galling and gouging craters were shown to initiate at existing defects. This applied to both microscopic and macroscopic features. A consistent microscopic feature observed prior to galling and gouging were deformation bands that resembled persistent slip bands on the rail surface. Another consistent feature was the transfer of slider material to the rail prior to galling and gouging. This suggests that gouging may not be triggered by micro-impact events, but by instabilities associated with high-speed thermoplastic shear. / text

Thesis (Ph. D.)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xv, 156 p.; also includes graphics (some col.). Includes abstract and vita. Co-advisors: Vadim I. Utkin, Giorgio Rizzoni, Dept. of Electrical Engineering. Includes bibliographical references (p. 153-156).

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 216-235).

Pas de résumé / Friction is scientifically interesting and technologically important. We can characterize friction well, but even the friction force between macroscopic surfaces of known chemistry and topography under known loading conditions cannot yet be predicted from the bottom up. A major obstacle to predicting frictional properties is to link the macroscopic observations to the behavior of the myriad microscopic connections that make up the interaction.The onset of frictional sliding occurs through the breaking of the contacts that were keeping the interface stuck. Recent experiments performed with high spatial and temporal resolution show that rupture nucleates at weak or highly stressed points and propagates outwards from there. Understanding how the rupture travels is an important step towards understanding friction. This thesis presents simulations and theory aimed at improving our understanding of this onset of sliding in dry friction systems. The principal model combines 2D elasticity with an asperity level description of the interface and reproduces and explains many of the experimental results. Analytical calculations provide additional insights.

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