Within the aerospace industry, the reduction of costs associated with operation, manufacture and development of gas turbine engines is a primary objective. Component and assembly design optimisations can satisfy weight reductions which correspond to operational and manufacturing cost reductions. Development cost can be reduced by implementing additional numerical validation stages as an alternative to experimental validation alone. Therefore, the overarching purpose of this research is the development of a computationally efficient constitutive modelling tool, which predicts the macroscopic deformation and failure of fan system components and assemblies during dynamic and highly non-linear thermo-mechanical loading. At the macroscopic scale a series of physical deformation and failure phenomena have been identified from the literature which are necessary for accurate representation of the dynamic behaviour of Ti-6Al-4V. Across the surveyed literature these capabilities have not been implemented together within a single constitutive framework prior to the commencement of this research. Experimental support provides validation data for the subsequent constitutive modelling activities, whilst also demonstrating the importance of strain-rate sensitivity, tension-compression asymmetry and anisotropic behaviour associated with texture orientation in Ti-6Al-4V. Numerical studies were also conducted to develop a robust procedure for rapid assimilation of uni-axial experimental data within constitutive benchmarking models, for development purposes. Further parametric studies of sub-component plate impact benchmarks revealed several limitations within the commercially available solutions. These limitations are related to mesh sensitivity and damage evolution. A technique has been proposed which couples damage evolution and imposes a directional length-scale. This provides enhanced mesh insensitivity and damage evolution rate control. However, a single damage evolution mechanism was demonstrated to be insufficient when representing shear damage mechanisms in uni-axial and multi-axial loading regimes. Therefore, an additional damage mechanism has been developed and coupled with the mesh sensitivity and localisation technique. The resulting cumulative and competitive damage evolution and localisation capabilities reflect the localisation characteristics observed in the literature. The variability of alloy manufacture and the subsequent macroscopically observed behaviour remain a limitation within an isotropic framework. This has motivated the development of both asymmetric and anisotropic formulations, integrated within the newly proposed multi-mode damage localisation framework. The ability of the newly implemented non-isotropic framework successfully provides both asymmetric yielding and hardening capabilities and anisotropic evolution. These developments have been demonstrated against experimentally obtained results for validation and calibration purposes. Together these capabilities allow for accurate representation of a wide range of macroscopically observable phenomena based upon micro mechanical mechanisms.

A nonlinear finite element model was developed to study the behaviour of unstiffened steel plate shear walls. The model was validated using the results from quasi-static and dynamic experimental programs. With the validated finite element model, the performance of 4-storey and 8-storey Type D (ductile) and Type LD (limited-ductility) steel plate shear walls with moment-resisting beam-to-column connections was studied under spectrum-compatible seismic records. A design procedure that aims to achieve optimal seismic behaviour for steel plate shear walls was proposed. The proposed method uses the concepts of indirect capacity design principles of CAN/CSA-S16-01 to identify the infill plates that are likely to yield in the design earthquake. The proposed method was used for the design of two 4-storey and one 8-storey shear walls. Design axial forces and moments in the boundary columns for the shear walls were shown to be in good agreement with nonlinear seismic analysis results. Results also showed that some of the other capacity design methods available generally underestimate the maximum design forces in the columns, while others can be overly conservative. The effect of loading rate on the dynamic behaviour of steel plate shear walls was also investigated, as was the P-Delta effect in terms of its influence on seismic demand in shear and flexure. A shear strength model of the infill plate with circular openings at any location was developed based on a strip model where all the strips with perforations were partially discounted. A design method for steel plate shear walls with perforations was introduced. The method was applied for the design of boundary columns of a 4-storey steel plate shear wall with perforations. The predicted design forces in the columns for the 4-storey perforated shear wall agreed well with the forces obtained from nonlinear seismic analysis. Finally, an improved simple formula for estimating the fundamental period of steel plate shear walls was developed by regression analysis of the period data obtained from frequency analysis of series of steel plate shear walls. In addition, the effectiveness of a shearflexure cantilever formulation for determining fundamental periods and P-Delta effects of steel plate shear walls was studied. / Structural Engineering

In an effort to improve the fuel efficiency of automobiles, car designers are investigating new materials to reduce the overall vehicle weight. Magnesium alloys are good candidates to achieve that weight reduction due in part to their low density and high specific strength. To support their introduction into vehicle body structures, the dynamic behavior of magnesium alloys must be determined to assess their performance during a crash event. In this work, the tensile high strain rate behavior of AZ31B magnesium alloy sheets was characterized. Two different temper conditions were considered: AZ31B-O (fully annealed) and AZ31B-H24 (partially hardened). Three different sheet thicknesses were considered for the O temper condition, 1.0, 1.6 and 2.5 mm, while the H24 temper was 1.6 mm in thickness. The sheet condition of the magnesium alloys implies an in-plane anisotropy induced by the rolling process. Therefore, both the rolling and transverse directions were investigated in the current research. In order to characterize the constitutive behaviour of AZ31B-O and AZ31B-H24 magnesium alloy sheets, tensile tests were performed over a large range of strain rates. Quasi-static experiments were performed at nominal strain rates of 0.003s-1, 0.1s-1 and 1s-1 using a servohydraulic tensile machine. Intermediate strain rate experiments were performed at 30s-1 and 100s-1 using an instrumented falling weight impact (IFWI) apparatus, and high strain rate experimental data at 500s-1, 1000s-1 and 1500s-1 was collected using a tensile split Hopkinson bar (TSHB) apparatus. Elevated temperature experiments (up to 300°C) were also performed at high strain rates using a radiative furnace mounted on the TSHB apparatus. The tensile experiments show a significant strain rate sensitivity of the constitutive behavior of both the O and H24 temper conditions. The two tempers exhibit an average increase of stress level of 60-65 MPa over the range of strain rates considered. As the strain rate increases, the strain rate sensitivity of both tempers also increases. The strain rate has a different effect on the ductility of the two material conditions. The ductility of AZ31B-O is significantly improved under high strain rate deformations, whereas the AZ31B-H24 exhibits similar ductility at low and high strain rates. Both material conditions presented a strong in-plane anisotropy, with an average stress level in the transverse direction higher than in the rolling direction by 15 MPa and 35 MPa for the O and H24 tempers, respectively. The thermal sensitivity for both tempers at high strain rates was obtained. The two material conditions exhibit a clear thermal softening. From room temperature to 250°C, the loss in strength at 5% plastic strain was found to be 55 MPa and 125 MPa for the AZ31B-O and AZ31B-H24 materials, respectively. The thickness of the AZ31B-O sheets has a mild effect on the measured constitutive behavior. The flow stress increases with increasing thickness. An average difference of 10-15 MPa was seen between the flow stress of the 1.0mm and 2.5mm sheets. However, similar strain rate sensitivity was seen for the three thicknesses. The experimental data was fit to three constitutive models: the Johnson-Cook model, its modified version with a Cowper-Symonds strain rate sensitivity formulation, and the Zerilli-Armstrong model. The three models were evaluated by numerical simulation of the TSHB experiment under various testing conditions. It was found that the Zerilli-Armstrong model was the most accurate in predicting the flow stress of the different material conditions. However, finite element models incorporating the three constitutive fits failed to predict necking in the specimen.

Shape memory alloys (SMAs) are a class of alloys that display the unique ability to undergo nonlinear deformations and return to their original shape when heat is applied or the stress causing the deformation is removed. This unique shape memory characteristic is a result of a martensitic phase-change, which can be temperature induced (shape memory effect) or stress induced (superelastic effect). In this study, the cyclical behavior of NiTi, a binary shape memory alloy, is compared to the cyclical behavior of NiTiCr, a ternary SMA. The purpose of this study is to compare the behavior of a 0.085-in. diameter NiTiCr wire with the behavior of the same size NiTi wire to determine whether ternary SMAs are more viable ways to take advantage of the unique properties of SMAs for seismic applications. The experimental results showing the superelastic behavior of these alloys under cyclical tensile loading are summarized with attention to the effects of annealing temperature, strain rate, and cyclical training on the stress-strain hysteresis, maximum recoverable strain and equivalent viscous damping.

There are two aspects in this study: cylinder penetrations and XBP (Expendable Bottom Penetrometer) interpretations. The cylinder studies firstly investigate the relationship between the soil resisting force and penetration depth by a series of rateindependent finite element analyses of pre-embedded penetration depths, and validate the results by upper and lower bound solutions from classical plasticity theory. Furthermore, strain rate effects are modeled by finite element simulations within a framework of rate-dependent plasticity. With all forces acting on the cylinder estimated, penetration depths are predicted from simple equations of motion for a single particle. Comparisons to experimental results show reasonable agreement between model predictions and measurements. The XBP studies follow the same methodology in investigating the soil shearing resistance as a function of penetration depth and velocity by finite element analyses. With the measurements of time decelerations during penetration of the XBP, sediment shear strength profile is inferred from a single particle kinetic model. The predictions compare favorably with experimental measurements by vane shear tests.

In an effort to improve the fuel efficiency of automobiles, car designers are investigating new materials to reduce the overall vehicle weight. Magnesium alloys are good candidates to achieve that weight reduction due in part to their low density and high specific strength. To support their introduction into vehicle body structures, the dynamic behavior of magnesium alloys must be determined to assess their performance during a crash event. In this work, the tensile high strain rate behavior of AZ31B magnesium alloy sheets was characterized. Two different temper conditions were considered: AZ31B-O (fully annealed) and AZ31B-H24 (partially hardened). Three different sheet thicknesses were considered for the O temper condition, 1.0, 1.6 and 2.5 mm, while the H24 temper was 1.6 mm in thickness. The sheet condition of the magnesium alloys implies an in-plane anisotropy induced by the rolling process. Therefore, both the rolling and transverse directions were investigated in the current research. In order to characterize the constitutive behaviour of AZ31B-O and AZ31B-H24 magnesium alloy sheets, tensile tests were performed over a large range of strain rates. Quasi-static experiments were performed at nominal strain rates of 0.003s-1, 0.1s-1 and 1s-1 using a servohydraulic tensile machine. Intermediate strain rate experiments were performed at 30s-1 and 100s-1 using an instrumented falling weight impact (IFWI) apparatus, and high strain rate experimental data at 500s-1, 1000s-1 and 1500s-1 was collected using a tensile split Hopkinson bar (TSHB) apparatus. Elevated temperature experiments (up to 300°C) were also performed at high strain rates using a radiative furnace mounted on the TSHB apparatus. The tensile experiments show a significant strain rate sensitivity of the constitutive behavior of both the O and H24 temper conditions. The two tempers exhibit an average increase of stress level of 60-65 MPa over the range of strain rates considered. As the strain rate increases, the strain rate sensitivity of both tempers also increases. The strain rate has a different effect on the ductility of the two material conditions. The ductility of AZ31B-O is significantly improved under high strain rate deformations, whereas the AZ31B-H24 exhibits similar ductility at low and high strain rates. Both material conditions presented a strong in-plane anisotropy, with an average stress level in the transverse direction higher than in the rolling direction by 15 MPa and 35 MPa for the O and H24 tempers, respectively. The thermal sensitivity for both tempers at high strain rates was obtained. The two material conditions exhibit a clear thermal softening. From room temperature to 250°C, the loss in strength at 5% plastic strain was found to be 55 MPa and 125 MPa for the AZ31B-O and AZ31B-H24 materials, respectively. The thickness of the AZ31B-O sheets has a mild effect on the measured constitutive behavior. The flow stress increases with increasing thickness. An average difference of 10-15 MPa was seen between the flow stress of the 1.0mm and 2.5mm sheets. However, similar strain rate sensitivity was seen for the three thicknesses. The experimental data was fit to three constitutive models: the Johnson-Cook model, its modified version with a Cowper-Symonds strain rate sensitivity formulation, and the Zerilli-Armstrong model. The three models were evaluated by numerical simulation of the TSHB experiment under various testing conditions. It was found that the Zerilli-Armstrong model was the most accurate in predicting the flow stress of the different material conditions. However, finite element models incorporating the three constitutive fits failed to predict necking in the specimen.

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This thesis focuses on the high strain rate behavior of Maraging steel 300, High Hardness Armor (HHA) and Aluminum 5083 – H131 Alloy. These materials are used by the Department of National Defense (DND) of Canada as armor plate materials in military applications. The aim of the research is to investigate the dynamic shear-strain response of these armor materials at high strain rate loading to study the occurrence of Adiabatic Shear Bands and the subsequent failure. The effects of impact momentum and strain rates on the dynamic stress-strain curve and on the adiabatic shear failure of these armor materials under impact and torsion loading need to be investigated to evaluate their capability to withstand military conditions.

This thesis focuses on the high strain rate behavior of Maraging steel 300, High Hardness Armor (HHA) and Aluminum 5083 – H131 Alloy. These materials are used by the Department of National Defense (DND) of Canada as armor plate materials in military applications. The aim of the research is to investigate the dynamic shear-strain response of these armor materials at high strain rate loading to study the occurrence of Adiabatic Shear Bands and the subsequent failure. The effects of impact momentum and strain rates on the dynamic stress-strain curve and on the adiabatic shear failure of these armor materials under impact and torsion loading need to be investigated to evaluate their capability to withstand military conditions.

Nanoindentation has brought in many features of research over the past decade. This novel technique is capable of producing insights into the small ranges of deformation. This special point has brought a lot of focus in understanding the deformation behavior under the indenter. Nickel, iron, tungsten and copper-niobium alloy system were considered for a surface deformation study. All the samples exhibited a spectrum of residual deformation. The change in behavior with indentation and the materials responses to deformation at low and high loads is addressed in this study. A study on indenter geometry, which has a huge influence on the contact area and subsequently the hardness and modulus value, has been attempted. Deformation mechanisms that govern the plastic flow in materials at low loads of indentation and their sensitivity to the rate of strain imparted has been studied. A transition to elastic, plastic kind of a tendency to an elasto-plastic tendency was seen with an increase in the strain rate. All samples exhibited the same kind of behavior and a special focus is drawn in comparing the FCC nickel with BCC tungsten and iron where the persistence of the elastic, plastic response was addressed. However there is no absolute reason for the inconsistencies in the mechanical properties observed in preliminary testing, more insights can be provided with advanced microscopy techniques where the study can be focused more to understand the deformation behavior under the indenter. These experiments demonstrate that there is a wealth of information in the initial stages of indentation and has led to much more insights into the incipient stages of plasticity.