A number of aspects of the coining process are investigated, both through experimentation using several types of tooling using blanks made of copper 110 or brass 260, and by developing and using a FEA model. Several relationships have been found which describe the effects of changing the type of coin blank or the geometry of the coining tooling on how much volume of the coin is formed at different forces. The open-die bulk upsetting test was used to find the true stress and strain curves of both materials, and the ring test was used to determine the coefficient of friction. Coins were made over a large range of forces in order to test the general nature of how the diameter and design of a coin are formed. While the diameter begins to increase, the thickness of the coin reduces and material is pushed into the punch cavity, filling the design’s volume up rather linearly. Tests on the effects of changes in the wall angle were inconclusive. As the punch design depth increased the force requirement went down in a manner roughly inverse to the ratio of the increase in depth. Effects of coining with a punch on one side versus two sides were tested. Effects of the perimeter of the punch design showed that a longer perimeter actually reduced the forces required for thinner coins, a difference that got smaller as the coin blanks got thicker. Blanks required 1.4 times the force to form than a coin half its thickness. A direct correlation of forming force to the yield stress of the material was expected but rather appeared to be related to the full nature of the true stress-strain curves. The FEA model was able to match experimental results relatively closely, but only up to about 333.3 kN, the lowest force used for the bulk of the experimental samples. The FEA model provided a good look into what happens to the coin while it is under load and the mysteries of ghost coining were unveiled. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-03-01 06:28:50.729

The structural integrity of a welded structure depends mainly on the performance of the welded joints. Due to the welding process, the mechanical properties of the structure change and different regions are created in the weldment. The mechanical properties of welded joints change significantly around the heat affected zone (HAZ). So to predict stress distribution around the weld, these changes should be considered in the finite element model (FEM) of the welded structure. In this research, the changes of mechanical properties around the welded joint were experimentally tested and used to develop a FEM model of a welded joint which can predict the stress behavior around the weld. First, an experimental analysis was carried out on an ASTM standard arc welded joint of stainless steel specimen to observe the microstructural change in the HAZ. This enables to find out the HAZ width using an optical microscope. Moreover, a tensile testing was performed to investigate the change of Young’s modulus of the HAZ compared to the base metal (BM). Another experimental analysis was also performed on a real arc welded structure of the same material to observe its’ strain distribution around the HAZ. The HAZ width and Young’s modulus obtained from the experimental testing were then applied to generate the FEM model of an ASTM standard arc welded joint as well as a real arc welded structure of stainless steel. The finite element analysis (FEA) results of stress distribution around the weld joint in both cases show a good agreement with the experimental results. Therefore, the developed material property based FEM model can predict the stress behavior of similar type of structures with the same welding process on the same material studied in this research. / February 2017

This thesis presents the detailed mathematical model developments, operational analysis, and speed field oriented control (FOC) implementation of a Disc-type Surface-mounted Permanent Magnet Synchronous Motor (DSPMSM). According to magnetic circuit concepts, system model was established systematically and simulated by three-dimensional finite element analysis (FEA) in order to verify the analytical model. The operational results and nominal settings were obtained by means of dynamic simulation of DSPMSM. Based on the system model, simulation results, and design specifications, the proposed machine and a DSP-based drive system were implemented. Finally, with application of the designed FOC scheme to regulate the electromagnetic torque production, the objective of rotor speed control was achieved successfully.

In modern automotive engines, the vast majority of light vehicle diesel (LVD) pistons are made from gravity die cast monolithic AlSi based alloy systems. Presently, the market drivers for reduced emissions, more efficient fuel consumption and increased specific power output are providing cyclic thermal and mechanical fatigue loading above the safe life durability threshold for the current AlSi based alloy systems. Peak temperatures in the diesel piston’s fatigue critical combustion bowl region are presently 420 °C for the AlSi based alloys, which represents a homologous TH value in excess of 0.8. In combination with peak temperatures of 420 C, the pistons are subject to cylinder pressures up to 220 bar, inducing mechanical stress amplitudes 15-20% greater than the allowable component fatigue strength for 1x108 cycles, in some applications. This durability deficit naturally leads to a requirement for new material and process solutions aimed at improving thermal and mechanical fatigue resistance at temperatures in excess of 420 C.One solution to this problem is to locally reinforce the pistons combustion bowl edge with a metal matrix composite (MMC) system. In this study, an aluminium based metal matrix composite (AlMMC) has been investigated and has shown some promise with increases in iso-thermal high cycle (1x 107) fatigue strength of 50 % compared to standard monolithic piston alloys. The AlMMC consists of a premium AlSi based LVD piston alloy matrix reinforced with 0.15 Vf of an interconnected network of 2-4 mm long Fe based fibres. The AlMMC is manufactured by pressure assisted infiltration of a sintered metallic fibre preform with as cast materials having a pore density of 0.2 %. In contrast to the use of ceramic fibre reinforcement systems generally requiring high pressure infiltration techniques, preform infiltration is considered possible with a comparably inexpensive manufacturing route. The Fe based fibre preforms can be infiltrated at lower pressure due to the reactivity between the Fe based fibres and the AlSi based matrix alloy. Unfortunately, this increased reactivity, although an advantage for preform infiltration, can result in (FeAlXX)Si(+X) interfacial reaction products forming between the fibre and matrix at operating temperatures of greater than 440 °C. These interfacial reactions result in a 15-20 m interfacial intermetallic layer after prolonged periods of exposure (>500 hrs), resulting in depleted fibre Vf and void formations on the matrix side of the interface.

This paper will seek to evaluate results obtained from mechanical testing and computational analysis to determine the efficacy of new thread designs for bone screws in their various applications and uses in surgical treatments. These new thread designs will be tested against the market standard buttress thread and any resulting trends will be analyzed. Four different thread designs were tested in 90 degree cyclic loading and then subsequently an axial pullout test. The parameters of interest from these tests such as peak to peak displacement over cycle and axial load versus axial displacement were recorded. These four designs were the Osteocentric A and C designs, the Synthes buttress screw, and a buttress screw with a matching major diameter to the Osteocentric A and C threads

This dissertation studies the feedback control of the dynamic response of multi-story structures to seismic excitations. The seismic excitations are represented by arbitrary unknown stochastic disturbances. The research consists of modeling of the structure with a control system and a control design in the state space. A combination of the extended Hamilton's principle and the Hierarchical Finite Element Method (HFEM) was used to derive the discrete differential equations of motion. This method exhibits superior accuracy with fewer degrees of freedom (DOF). The discrete equation were realized in the state space, where the Multiple Channel Control (MCC) model, the Single Channel Control (SCC) model and the Special Single Channel Control (SSCC) model were proposed. The MCC model is a general multiple input/multiple output (MIMO) dynamic system; the SSCC model is a single input/multiple output (SIMO) dynamic system; which requires only one actuator acting on the base; the SCC model has duality. On one hand, the system can be classified as MIMO when control actuators are regarded as the input. On the other hand, it can be regarded as a SIMO system when control signal as the input. Moreover, three different types of control methodologies, the Linear Quadratic Gaussian (LQG) control, the Disturbance Accommodating Control (DAC), and the hybrid LQG/DAC approaches, were successfully developed to actively mitigate the vibration of the multi-story structures subjected to the seismic disturbance. In addition, the Kalman filter was used as an optimal observer to estimate the state of the system in the LQG and the LQG/DAC design. Finally a numerical simulation of a four-story structure was carried out under nine cases. The cases covered various combinations of the three models and the three control designs to verify the effectiveness of control technique developed in this study. The simulation results found were quite encouraging. The results show each combination has its preponderance corresponding to special priority. In general, the hybrid LQG/DAC control in conjunction with the SSCC model is the best choice. / Ph. D.

Guided wave inspection is a form of ultrasonic testing used for non-destructive testing (NDT). Guided waves are capable of propagating long distances bounded by the geometries of the specimen, such as pipes and plates. The technique is commercially used to detect defects in pipelines and is capable of a full volumetric screening many metres (often up to around 100m) from one location. Fundamental axisymmetric wave modes are used to inspect pipelines and are used to quantify defects and features. However, as the technology has progressed, a demand for improving defect sensitivity, spatial resolution and developing the technology into new fields has been recognised. Operating at medium range frequencies is one possibility that could provide the increase in defect sensitivity and spatial resolution required that may not be achieved at low range frequencies. The use of higher order wave modes could also provide additional information useful for defect sizing. Guided wave inspection is a complex ultrasonic technique due to the many wave modes that exist and testing at medium range frequencies requires some challenges to be overcome. The research presented here investigates the potential of using the second order torsional wave mode at medium range frequencies and provides a new sizing technique that for some applications is likely to offer advancement in guided wave inspection and monitoring. The approach firstly included the design and implementation of a setup for analysing the complex signal responses in order to access the higher order torsional wave mode T(0,2) for defect sizing. An efficient method of using FEA has been presented using segmented models to provide the capability of analysing defects with small increment changes that could not be achieved using a full 3D model of the pipe. Using a pipe segment to virtually represent the full pipe also allowed small changes in defect size to be investigated, which would otherwise be extremely difficult to accurately machine experimentally. The FEA modelling technique is also based on broadband signals in comparison to the conventional approach of using narrowband signals and is capable of obtaining a wide frequency spectrum from one model, which significantly reduces the number of models needed to conduct a frequency analysis. Following on from this work, a high density transducer array was developed and compared against a conventional transducer array used in guided wave inspection for the purpose of medium range frequency inspection, which can also be applied to conventional low range frequency inspection. Finally, a new defect sizing method using T(0,2) is presented, which is capable of predicting the depth using peak amplitude responses from spectral analysis and by comparing this to the cut-off frequency of the remaining wall thickness of the defect. The technique has the potential to improve defect sizing, defect sensitivity, increase spatial resolution, and increase the performance of medium range inspection.

For the finite element (FE) simulation of relatively thin organs under complex dynamic loadings that are relevant in the biomedical engineering field, shell elements, compared to volume elements, have the potential to capture the whole thickness of the organ at once. Shell elements, are also known to feature efficiently large critical time steps, ensuring competitive computational times in dynamic structural analysis projects. As an improvement to the tools available for modelling and analysis, a new general nonlinear thick continuum-based (CB) shell FE embedded in an updated Lagrangian formulation and an explicit time integration scheme was recently developed. It can account for irregular and complex geometries, and hyper-elastic, large, nearly incompressible anisotropic 3D deformations characteristic of soft tissues. The original proof of concept was developed in MATLAB, which despite known advantages, is very slow. As a result, computational times, even for simple problems, have not been competitive. Therefore, the present work focused on re-writing the code in an efficient programming language with execution speed in mind in order to compete with the available elements which, in spite of having inferior capabilities, have better running times. In addition, a programming algorithm was needed to improve running time. Once it was implemented, the running time was reduced in half on a benchmark problem. Optimization was then exploited to introduce workarounds and design improvements that reduced running time further to 95% of its original value. The new version of the code was implemented in C++ and reached the goal of reducing running time while maintaining the expected functionality.

In this study, one of the plastic automotive parts, Air Duct, manufactured through blow moulding process is reviewed and investigated with a practical process point of view using structural mechanics approach. First, current blow moulding process was examined to find governing factors of the process which can be improved or adjusted for better quality control of finished product. Secondly, numerical analysis was conducted on the post-mould process in order to predict the deformation in the final products with properly assumed initial and boundary conditions. The simulation results showed that the degree of warpage under current blow moulding process could be predicted at a reasonable accuracy. It was also discovered that the distortions of the holes are strongly dependent on it location and surrounding, and the current cooling method should be improved to improve the quality. Based on the simulation results and literature survey, a better post-mould cooling method was suggested. In addition, the problem in cooling system was identified, and redesigning scheme was recommended.

Detailed knowledge of tissue mechanical properties is widely required by medical applications, such as disease diagnostics, surgery operation, simulation, planning, and training. A new two degrees of freedom portable device, called Tissue Resonator Indenter Device (TRID), has been developed for measurement of regional viscoelastic properties of soft tissues at the Bio-instrument and Biomechanics Lab of the University of Toronto. As a device for clinical application, the accuracy and reliability of TRID is crucial. This thesis thus investigates the tissue samples’ mechanical properties through finite element analysis method after reviewing the experimental results of the same tissue samples using TRID. The accuracy of TRID is verified through comparing its experimental results with finite element simulation results of tissue mechanical properties. This thesis also investigates the reliability of TRID through experimental study of its indenter misalignment effect on the measurement results of tissue static stiffness, dynamic stiffness, and damping respectively.