"For industrial explosion protection, residual risk analysis determines the likelihood that a given protection scheme will fail to mitigate an explosion occurrence, where one or more points of a system are subject to failure. Current design practice for providing explosion protection measures for industrial hazards follows a process where, although the designer satisfies accepted industry codes and standards, the result is a system where the risk of failure remains unknown. This thesis proposes and demonstrates the use of a methodology to assist design engineers in constructing an explosion protection system that meets a specified quantifiable level of risk. This new methodology can assist building owners and decision makers in selecting a design that best meets their risk-based goals and objectives."

"Residual stresses are a common and often undesired result of material processing, introduced through non-linear deformation and/or phase transformation of material under mechanical or thermo-mechanical loading. These macro stresses alter mechanical properties and the intrinsic fatigue crack growth characteristics of the material. Residual stress artifacts can introduce inconsistencies and significant errors when the true material behavior is needed for material development and optimization and for structural component design. The effects of quenching residual stresses on fatigue crack propagation behavior of various materials were investigated. In parallel, residual stresses similar in magnitude and distribution with the quenching residual stresses were generated using mechanical processes to decouple the effects of residual stresses from microstructural effects. Mechanical residual stress distributions predicted by 3D elastic-plastic finite element analysis showed good agreement with the stresses measured on fatigue crack growth testing specimens using fracture mechanics approaches. Crack propagation characteristics in fields with low and high residual stresses were studied using optical and scanning electron microscopy, and the effects of residual stress on crack path behavior were assessed. An original residual stress analytical correction to fatigue crack growth data was developed, compared to existing corrective methodologies, and validated using residual stress free data. Overall, the work provides tools to understand, control, and correct the effects of processing residual stresses on fatigue crack growth for accurate fatigue critical design and life predictions."

The manufacturing of nickel-base superalloy forging for aero-engine applications requires a number of thermo-mechanical processing steps, which generate significant residual stresses that can result in distortion, uncontrolled deformation of the component during machining, or, when added to the in-service stresses, they will increase the crack initiation probability and hence reduce component life. Ageing treatments are applied to nickel-base superalloys in order to precipitate the strengthening phases that give to the alloys their remarkable strength over a wide temperature range. These isothermal treatments also result in a reduction of the residual stress level by means of thermal stress relaxation. In this work, the focus has been on the study of the thermal residual stress relaxation induced by the ageing treatment of wrought nickel-base superalloys. The aim of this work is to improve the understanding of the residual stress relaxation process and the different deformation mechanisms involved in the stress relaxation during isothermal treatments. This has been achieved by combining neutron diffraction with a new in-situ heating setup in order to track the elastic strain evolution in the centre of quenched disc shaped forgings of Inconel 718 and Udimet 720LI. This research has resulted in the implementation of an induction heating setup which was designed in order to serve in-situ residual stress analysis during isothermal treatments of large components at temperatures up to 1000°C. The in-situ analysis of residual stresses required the development of a standardised method which consists of monitoring the d-spacing evolution in stressed samples and in stress-free samples during isothermal treatments in order to determine the time dependent stress evolution. Stress calculations were performed using temperature dependent diffraction elastic constants which were determined experimentally for Inconel 718 and Udimet 720LI at high temperatures. The in-situ neutron diffraction measurements in water quenched disc shaped forgings of Inconel 718 of different thickness during isothermal treatments at 720°C revealed that the stress relaxation amplitude does not vary significantly with the initial stress distribution. However, the stress relaxation rate is strongly affected by the annealing temperature as stress relaxation through creep was observed to evolve at a diminishing rate during the isothermal treatment of Inconel 718 at 720°C and 750°C while no further stress relaxation occurred at 650°C. Most of the stress relaxation was found to occur during the heating stage as a result of a combination of plasticity and early stage creep relaxation. In-situ and ex-situ measurements exhibited good agreement on the amplitude of residual stress relaxation. It was found that a heat treatment at 750°C for 8h reduced the stresses by approximately 70% in Inconel 718 and only 20% in Udimet 720LI. For all in-situ experiments it was possible to fit the stress relaxation data by using logarithmic functions, which can now be used for validating and/or improving process models.

O presente trabalho tem como objetivo estudar o comportamento de um solo residual melhorado através do uso de técnicas mecânicas de compactação e da adição de cimento. Complementarmente foram realizadas análises numéricas destes materiais tratados quando utilizados como base de fundações superficiais. O programa experimental incluiu a retirada de amostras intactas e de material amolgado para a execução de ensaios triaxiais saturados drenados com medida interna de deformações, a fim de estudar o comportamento do solo natural e do solo tratado, quer por compactação, quer por adição de cimento e compactação. Além disto, tais ensaios são determinantes na obtenção de parâmetros constitutivos para a realização de simulações numéricas. O Método dos Elementos Finitos foi utilizado para simular o comportamento carga versus recalque de placas assentes sobre o solo natural e sobre camadas de solo melhorado. O modelo Hiperbólico foi empregado na análise numérica para modelar o comportamento tensãodeformação dos materiais. Os resultados das simulações dos ensaios de placa sobre camadas de solo melhorado demonstraram que houve um aumento significativo da capacidade de suporte, além de uma redução considerável dos recalques, quando comparados ao comportamento do solo natural. / The aim of this research is to study the behavior of a residual soil improved through compaction and cement addiction. The experimental programme comprises sampling of residual soil in the field and laboratory drained triaxial tests Mth interna1 measurement of deformation. These tests were valuable for examining severa1 aspects of the behavior of the naturally structured residual soil and the improved material. Besides that, results were interpreted for the assessment of constitutive parameters for performing numerical simulations. The Finite Element Method was used to predict the load-settlement behavior of plates in which the Hyperbolic model was employed to describe the stress-strain behavior of the materials. The results of the simulated plate load tests resting on layers of treated soil have shown that there was a significant improvement in bearing capacity and a reduction in settlements when compared to the behavior of the natural residual soil deposits.

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.

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.

The goal of this research was to investigate an experimental infrared transmission technique and associated analysis tools that extract the in-plane residual stresses in thin single and poly-crystalline silicon sheet, and try to relate the residual stresses to physical parameters associated with silicon growth and cell processing. Previous research has suggested this concept, but many engineering and analytical details had not been addressed. In this research, a system has been designed and built. A fringe multiplier was incorporated into the system to increase the sensitivity. The error was analyzed and the resolution of the system was found to be 1.2~MPa. To convert the experimental results to residual stresses, the stress-optic coefficients of (001), (011) and (111) silicon were analyzed analytically and calibrated using a four-point bending fixture. Anisotropy in (001) and (011) silicon was found to be 33%, and the coefficient of EFG silicon is 1.7 times larger than that of (001) silicon. The polariscope together with other techniques was applied to silicon wafers after various processing steps in the manufacture of photovoltaic cells. The influence of the processing on residual stress was investigated and positive correlations between residual stresses, PL and efficiency were obtained.

The first objective was to estimate total internal fat in beef cattle based on a technique that measures kidney fat (uKFd) using real-time ultrasound (RTU). Data were obtained from 109 cattle from four studies, and animals were scanned 7 d preslaughter for uKFd and ultrasound backfat thickness. At slaughter carcass kidney fat depth (cKFd), KPH weight, and total internal fat were measured. The second objective was to characterize residual feed intake (RFI) in finishing cattle fed high grain diets and to examine the relationships with growth, ultrasound, carcass, non-carcass, and tenderness traits in two studies involving Santa Gertrudis (n = 114) steers, and Angus bulls (n = 16) and heifers (n = 16). In both experiments, RFI was calculated as the difference between actual DMI and predicted DMI. Results for the first objective indicated that RTU can be used to estimate cKFd, KPH weight and total internal fat (IFAT). Prediction equations developed to predict IFAT had R2 that ranged from 0.65 to 0.97 (P < 0.05). Results for the second objective indicate that RFI was not correlated with ADG, but was positively correlated with DMI and feed conversion ratio. Carcass 12th-rib fat depth was positively correlated with RFI in Santa Gertudis steers, such that steers with low RFI were leaner than steers with high RFI. Residual feed intake was not correlated with carcass or non-carcass composition traits in Angus bulls and heifers. Marbling and tenderness traits were not associated with RFI. Results from these studies indicate that we are able to measure IFAT with RTU, and that beef cattle producers can utilize RFI to identify animals that are more efficient with minimal impacts on growth, carcass composition and tenderness.

The residual stress distribution, growth of Intermetallic Compound (IMC) layer and the equivalent strength in the Laser diode package are investigated in this thesis. The redistribution of residual stress in the solder layer is calculated by employing the MARC finite element package. The effects of residual stresses and IMC layer on the bonding strength of Laser diode under taken different thermal load cycles are studied. Numerical results are compared with the results measured experimentally. Results indicate the effect of residual stresses introduced in the solder solidification is so important in the stress analysis of a solder joint. The effects of different solder parameters, i.e, solder alloy, solder layer thickness and the number of thermal load cycles, are also analyzed in this work.. A better understanding about the solder bond strength is expected from this analysis.

Thesis (Ph. D.)--Open University. BLDSC no. DX237328.