This study aimed at dissimilar metal butt friction stir welding in various types of processing conditions on the welding product hardness, tensile strength, etc. At first, using the AA-5052 as the similar material in FSW(friction stir welding) process. Compare the affected in different working parameter such like tool rotation speed, tool feed rate, etc. During FSW process, using the K-type thermal couple to monitoring the temperature history at different position in the specimen. According the result and finding the best working parameter. As the result shown, the high speed rotating rate or the low feeding rate will cause more heat energy in the specimen. In completed FSW condition, the range of rotating rate is 600-900rpm, the feeding rate is 40-80mm/min, the preheating temperature is suitable in 350¢J. For the aluminum alloy and copper alloy of the dissimilar metal friction stir welding, specimen¡¦s surface has holes and large chip by lacking heat during using the tool diameter of 12mm to weld, use the tool diameter of 15mm to weld can enhance the heat during the welding process and improve the production of surface.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 163).

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Salinas, David. "September 1990." Description based on title screen as viewed on December 17, 2009. DTIC Identifier(s): Vibration, sliding friction, guns barrels, cantilever beams, Euler equations, finite element analysis, transformations (mathematics), theses, frictionless holes, holes (openings), recoil. Author(s) subject terms: Cantilever beam, finite element method, axial motion, vibration, transient behavior. Includes bibliographical references (p. 110). Also available in print.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Leamy, Michael; Committee Member: Costello, Mark; Committee Member: Ferri, Aldo. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The effect of using a boric acid based additive in lubricants and fuel enhancers was investigated in this study. Experiments were performed in a reciprocating and a continuous sliding ball-on-disk test equipment. Different oil types and temperatures were used. The aim of the experiments was to provide information about how these boron containing lubricants work in terms of chemistry and tribology. The surfaces after tribological contact were analyzed with Light Optical Microscopy (LOM), Vertical Scanning Interferometry (VSI), Scanning Electron Spectroscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Secondary Ion Mass Spectroscopy (SIMS). The boric acid based additive and the temperature used affected both the friction and wear. A higher oil temperature resulted in wider wear tracks. Oil with boron additive seemed to lower the friction coefficient at temperatures above 50 °C, compared to the same oil without boric acid; the reference oil. The tests also indicated that friction coefficients as low as 0.05 can be achieved by using a boron additive layer on the disk surface together with PAO-oil. Tribofilms containing Zn, P, S, Mg and O were formed in the wear tracks at high temperatures for both the reference oil and oil with boron additive. Oxidized regions were found in the tracks created from tests at 25 °C. Tests with oil containing boron additive resulted in lower Zn concentrations in the tracks, which is an indication that the boric acid based additive hinders the formation of these Zn rich tribofilms. To summarize, both oils and fuel enhancers with boric acid can obtain lower friction coefficients compared to those without this additive. The role of boric acid in the tests performed, both regarding the tribology and chemistry, is not yet fully understood and more chemical investigations are needed.

The behaviour of gas-liquid foams has been the subject of extensive research in the past century because of the usefulness of liquid foams in industry. In this work we present new experimental and theoretical developments concerning flow and drainage behaviour of surfactant based liquid foams and films. The flow of free films and foam was studied in vertical tubes for different liquid properties. Measurements of the thickness of the lubricating layer on the wall and CFD simulation shows a relationship between the liquid thickness, liquid viscosity and pressure drop for the flow of free films. For foam flow, friction factors were determined for all systems and data lied remarkably on a unique line on the friction factor-Reynolds number plot and has a practical significance in that pressure drop can be calculated using a constant friction factor along a pipe of a constant cross section in any flow regime. An improved ER technique has been developed for accurate measurements of foam resistance, which includes the liquid layer at the wall. Traditional ER-methods for characterising the drainage of a wall-confined static foams do not take into consideration the effects of a substantial liquid layer established on the wall during drainage which transports a substantial amount of liquid. A method is proposed for the estimation of temporal as well axial variations of the wall liquid thickness inferred from the measurements of the local liquid holdup. A theoretical model is proposed for foam drainage based on the analogy of liquid flow through a packed bed of solid particles. A good agreement is obtained between theory and experiment on the basis of judicious estimations of foam cell size and shape factor.

This thesis contains three separate yet closely related topics: fracture, friction and simulation of mechanical response of a confined granular medium. The first two are experimental investigations and the last one is a numerical study. In the fracture part, I will describe how to break a piece of silicon in a controlled way such that the atomic nature of the fracture process can be revealed in a macroscopic experiment. In the friction part, I will present another experiment using almost exactly the same setup as for the low temperature fracture experiment to study the properties of static friction and explore ideas concerning the origin of friction. In the last part, I will construct a confined granular packing and study how pulses and continuous waves propagate through it. All these three topics are relevant to geophysical science. I sincerely hope that my study can ignite some fresh thinking in that area and help other researchers to design models that can make more precise earthquake predictions. / text

This master thesis report evaluatesthe lubricating effect of graphene (G)and graphene oxide (GO). Thesematerials have been added, in particlecondition, in Ag-based slidingcontacts and lubricating greases. Thework focuses on the tribologicalevaluation of these materials,especially friction, wear and contactresistance analyses. The friction andwear behaviors of Ag-based contactscontaining of a wide concentrationrange of graphene and graphene oxideare tested against pure silver using atest load of 2 and 10 N at a constantspeed of 5 cm/s. It was revealed thatsmall amounts of G and GO are able tosignificantly reduce the frictioncoefficient and wear rate. Contactresistance measurements revealed thatresults similar to pure Ag can beachieved with G content up to 10vol%.Possible mechanisms, which maycontribute to this tribologicalbehavior are the Ag-C interactions andthe lubricating nature of graphene.Friction tests with G and GOcontaining lubricating greases showinconsistent results, and both greasesand corresponding test methods forevaluation require furtheroptimization. The overall, promising,tribological behavior of G and GOholds for the implementation invarious industrial applications. Thereis no doubt that these kinds ofmaterials can play an important rolein ABBs future work. This masterthesis report shows yet anotherapplication area for theseextraordinary materials.

No description available.

Internal friction has been known to be a cause of whirl instability in built-up rotors since the early 1900's. This internal damping tends to make the rotor whirl at shaft speeds greater than a critical speed, the whirl speed usually being equal to the critical speed. Over the years of research, though models have been developed to explain instabilities due to internal friction, its complex and unpredictable nature has made it extremely difficult to come up with a set of equations or rules that can be used to predict instabilities accurate enough for design. This thesis deals with suggesting improved methods for predicting the effects of shrink fits on threshold speeds of instability. A supporting objective is to quantify the internal friction in the system by measurements. Experimental methods of determining the internal damping with non-rotating tests are investigated, and the results are correlated with appropriate mathematical models for the system. Rotating experiments were carried out and suggest that subsynchronous vibration in rotating machinery can have numerous sources or causes. Also, subsynchronous whirl due to internal friction is not a highly repeatable phenomenon.