Friction welding has become an accepted method of joining many dissimilar materials and is now being extensively used in industry. Even though it is the single most versatile method of joining similar and dissimilar materials, there are still many more material combinations that cannot be welded by this process or which result in an unsatisfactory brittle weld. There are several applications for these materials in industry. The objective of this work was to overcome these 'no-weld' or 'brittle-weld' limitations. The proposed process involves introduction of a third element into the conventional two-element friction welding process. The third element used is a material which forms a good friction weld with both of the other two elements when welded separately. If the two parent materials are not compatible when they come into direct contact due to the formation of intermetallics and lack of conditions inducive to good bonding, the third element, which forms good welds with both of the parent parts, acts as a buffer between the other two. While keeping them apart, it forms a joint between the two incompatible parent materials. Among several probable candidates for intermediate materials, only a few meet the requirement that they create proper conditions for bonding. After a friction welding machine had been designed and built, it was successfully tested to weld both similar and dissimilar materials by both the conventional and the proposed three-element processes. Welds between compatible materials of high efficiency were obtained by the conventional process. For material combinations normally incompatible, joints were made possible with the aid of the intermediate elements. Various degrees of joint-strength depending upon the material combinations used were observed. The strength of the joints obtained between bronze and steel, for example, was increased by as much as 40% by using a copper interlayer. The welds were subjected to tensile tests. Microstructural examinations were conducted on the separated surfaces to determine the mode of failure. Electron micro-probe analyses were also conducted to determine if there were any diffusion of elements and/or formation of intermetallics. Quantitative analyses were also made on the diffused elements. Some hypotheses were put forward as to the conditions that dictate the joint strength obtained by the three-element process and also the requirements of materials which may perform adequately as intermediate materials. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

This thesis is an experimental investigation of the roughness problem in open channel flow. A literature review is given on the previous research done on friction factors. It is done in chronological order, so that the historical development of the friction equation can be seen.

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The road surface friction is an important characteristic that must be measured accurately to navigate vehicles effectively under different conditions. This parameter is very difficult to estimate correctly as it can take up a value from a broad spectrum of possibilities and the knowledge of this characteristic is of utmost significance in modern day automotive applications. The possible real-time knowledge of friction opens a new range of improvements to the active safety systems such as the Electronic Stability Control (ESC) and Anti-lock Braking Systems (ABS) in addition to providing computerized support to safety applications. The aim of the research is to take an engineering approach to the problem and design a simple and a robust algorithm that can be implemented in any automotive application of choice. After integrating the load transfer model with the four wheel vehicle model, the Dugoff tire models are combined with the aforementioned model to represent the plant model. Using the plant model to design an emulator, the sensor measurements are created and these measurements are then used by a non linear estimator such as the Unscented Kalman Filter to predict the forces at the tires. Friction is then calculated for every iteration and then passed back into the loop.In the end, a comparison of different design methodologies, implementation techniques and performance along with design decisions are discussed so that the current work can be implemented on a real-time controller. In addition to this, a section is dedicated towards highlighting the difference that prior friction information has on the stopping distance of a vehicle. For this purpose, a demonstration is made by creating an ABS control system that uses the predicted friction information and the performance improvement is documented. / Master of Science / The goal of the research is to identify methods in which the road surface friction can be detected by the on board computers present on modern day cars. Drivers have the ability to determine the grip on the road surface through various mechanisms, for instance if a driver sees a patch of ice on the road when driving, their normal response is to take the foot off the gas and drive without giving much steering input to avoid a slide. Another input that the driver can use to assess the grip is through the 'steering feel', which is the ability to differentiate different driving conditions through the force feedback from the steering wheel. There have been numerous approaches to help teach the computer to detect these road conditions so that it can operate other computerized systems such as the ABS(Anti-lock Braking System) and ESC( Electronic Stability Control) programs with better accuracy. This work is an attempt to contribute to this vital area of study. At the end of the study, an algorithm to predict the dynamic estimate of friction has been developed and the improvement in the performance of the Anti-lock braking system using this friction estimate has been demonstrated

A major challenge in tire, as well as in road engineering, is to understand the intricate mechanisms of friction. Pavement texture is a feature of the road surface that determines most tire-road interactions, and can be grouped into two classes: macro-texture, resulting mainly in the hysteretic component of friction, and micro-texture, resulting in adhesion. If both textures are maintained at high levels, they can help provide sufficient resistance to skidding. The ultimate objective of this research is to develop a physics-based multiscale rubber-road friction model that can predict the effectiveness of the tire as it interacts with the vehicle and the pavement. The model is developed based on sound physics and contact mechanics theories and uses road profile measurements and data measured on various tire compounds. To be able to predict road surface characteristics, it is proven that road surfaces are of fractal nature on given ranges of scale. It is shown that while global fractal quantities fail to classify pavement profiles, a local fractal parameter and three other texture parameters can separate road profiles that have different friction characteristics. Through the implementation of various contact theories and by conducting simulation studies, a methodical understanding of contact mechanics and of the effect of the diverse factors that influence friction is attained. To predict the viscoelastic friction between any given tire tread compound and road, the Nanovea JR25 portable optical profilometer is used to measure the road profiles. To characterize the road profile, the one-dimensional pavement measurements are used to obtain the two-dimensional power spectrum, followed by testing and characterizing the tread compounds (this is being carried out by Bridgestone). This data is used to develop a comprehensive analytical methodology to predict friction. To validate this model, a Dynamic Friction Test apparatus is designed and built. The friction tester enables measurement of the friction between tread compound samples and arbitrary surfaces, at different slip ratios. The correlations between the simulations and both indoor and outdoor experimental results are investigated. / Ph. D.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 95-96).

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (leaves 37-39).

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 81-83).

A Dissertation for the Master’s Degree in Mechanical Engineering School of Mechanical, Industrial & Aeronautical Engineering Date: 02/02/2017 / The Friction Stir Welding process is a rotating tool, that consists of a specialy designed shoulder and pin, that is plunged into the joining line of the required material and traverses along this line. The friction is induced by the rotating tool causes the workpiece material to rise to an operating temperature of 70% to 90% of the workpiece material's melting temperature and resulting in, no phase change, nor any defects associated with phase change, occurs in the workpiece. The increased temperature of the material causes the shear yield strength to drastically decrease thus allowing the two pieces to plasticise, easily stir around the tool and subsequently join. As the tool traverses along the workpiece, the softened material cools in the wake of the rotating tool and recrystallises, forming a ne grained microstructure. Attempts to develop an innovative tool to correlate the resulting of thermal models with process parameters are scarce. In this work, 6056-T4 and 6082-T6 Aluminum alloy sheets are friction stir welding at different rotational and translational speeds during the experimental aspect and material 2024-T3 for the analytical calculations. The effects of process parameters on the resulting thermal and mechanical properties are investigated. The results show that the use of coolant during the friction stir weld decrease heat generation substantially, this can also affect the force of the weld. It is also observed that the shear strenght of the processed sheet depends strongly on the rotational and translational speeds as weld as the thermal aspect and varies widely within the processed region, this was shown in this study by evaluating the thermal aspects of different weld types namely the Standard tool, Bobbin tool and the innovative tool. In addition. The proposed approach involves determination of the use of the friction stir welding in different thermal conditions and championing the use of an innovative tool. / MT2017