Summary Residual stress dssess ment by means of the hole drilling techniqae is still regarded by many analysts as a phenomenon whose use is restricted to isotropic and homogeneous materials. The work caFried out in this paper tends to address this 'lack of certainty' through introdacing a verilication approach of experimentally assess ed residual stress values, The components investigated were produced under pure bending conditions and anulysed for their residual stress behaviour using a customized strain gaage rosette. This rosette was employed in order to detect the average and peak maximam strain relaxstion os a result of producing a hole by the high speed drilling technique. It is envisaged that the concept of the verffication method could lead to a better understanding with regard to residual stress analysis.

Summary Historicully, stress analysis used for component design assames "ideal" materials, i.e. with isotropic, homogeneous and uniform metallurgical properties. We know that this is untrue, no matter how good the design. As design cannot provide fo, defect-free materials or components, ok appropriute defect tolerance should be the aim of the designer. Hence the concept of fuil-safe components has been introduced fo, safety-critical purts. Automotive wheels, howeveF, ure not considered fail-safe and fatigue lW prediction techniques fo, these components need to be improved in an endeavour to provide light-weight, attractive, but still safe und durable wheels. This applied approuch, where the proposed lW prediction model employs relutionships given by Gerber und a proposed lW prediction model derived from combining aspects of lW prediction models according to Collins und Juvinall & Marshek. The results show good coruelation with that of uctual wheel fatigue data.

No description available.

No description available.

Residual stresses are “locked-in” within a material, and exist without any external loads. Such stresses are developed during most common manufacturing processes, for example welding, cold working and grinding. These “hidden” stresses can be quite large, and can have profound effects on engineering properties, notably fatigue life and dimensional stability. To obtain reliable and accurate residual stress measurements for uniform and non-uniform stress states, a novel and practical method using crossing-slitting and ESPI is presented here. Cross-slitting releases all three in-plane stress components and leaves nearby deformation areas intact. The ESPI (Electronic Speckle Pattern Interferometry) technique gives an attractive tool for practical use, because measurements provide a large quantity of useful data, require little initial setup and can be completed rapidly and at low per-measurement cost. A new ESPI setup consisting of shutter and double-mirror device is designed to achieve dual-axis measurements to balance the measurement sensitivities of all in-plane stress components. To evaluate data quality, a pixel quality control and correction procedure is also applied. This helps to locate bad data pixels and provides opportunities to correct them. The measurement results show that this procedure plays an important role for the success of residual stress evaluation. Based on the observed displacement data and finite element calculated calibration data, an inverse computation method is developed to recover the residual stresses in a material for both uniform and non-uniform cases. By combining cross-slitting and ESPI, more reliable results for the three in-plane residual stress components can be obtained.

No description available.

No description available.

The practical advantages of thermal spray coatings like high deposition rates, low cost and tribological properties of high wear resistance have enabled these coatings to become an integral part of aircraft and automobile industry. Recent advancements in thermal spraying techniques like high particle speed and temperature call for new applications for these coatings. This experimental study addresses the Rolling Contact Fatigue performance of thermal spray coatings deposited by a variety of techniques like High Velocity Oxy-Fuel (HVOF), Detonation Gun (D-Gun) and Plasma spraying. RCF tests were conducted using a modified four ball machine in conventional steel ball bearing and hybrid ceramic bearing configurations. Tribological conditions during the RCF tests were varied by changing the test lubricant and the lubrication mechanism, contact load and shape of the drive coated rolling element to vary the roll/slip ratio. RCF tests were analyzed on the basis of the performance, coating failures using surface and subsurface observations, and residual stress studies. Experimental and theoretical studies of the ball kinematics have also been included. These tests revealed that the performance of the coated rolling elements was dependent upon the coating and the substrate properties. The coating thickness, substrate hardness, tribological conditions during the test, coating and substrate material as well as the coating process and the substrate preparation significantly affect the coating performance and the failure modes. Three different failure modes of these coatings have been discussed along with the changes in the near surface residual stress behaviour of the coated rolling elements.

Experimental cold modelling of hearth drainage was performed at Bluescope Steel Research Laboratories to understand the impact of variable drainage rate on slag removal. These drainage studies were designed to simulate real operational aspects such as: continuous casting, variable tapping rate and inflow liquid distribution. During the analysis of these drainage experiments it was demonstrated that the residual-flowout correlation in use since the 1970??s may possibly be incomplete or inaccurate. The removal of slag from the blast furnace hearth is the greater concern of the two liquids produced in the iron making process. In the 1970??s operational difficulties arose when large volumes of residual slag remained in the furnace after casting. This prompted research related to the flow of viscous liquids through uniformly packed beds providing fundamental insight on the most effective means of removal of slag from the blast furnace hearth. The core subject of this study, the residual-flowout correlation developed by Fukutake and Okabe that is used to predict cast duration and liquid accumulation in the blast furnace hearth is discussed in detail. The residual-flowout correlation is examined for four different sets of conditions based on constant or increasing slag drainage, with and without liquid dripping. The outcome of this study will improve our understanding of the residual-flowout relationship and develop it further, so that drainage conditions whether for constant or increasing drainage rates, with or without dripping, will hold using the one general Fl equation.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2007. / Committee Chair: Liang, Steven Y.; Committee Member: Garmestani, Hamid; Committee Member: Huang, Yong; Committee Member: Melkote, Shreyes N.; Committee Member: Neu, Richard W. Part of the SMARTech Electronic Thesis and Dissertation Collection.