The purpose of this study is to integrate the efficiency of the computer-aided design software Pro Engineer and the finite element analysis software LS-DYNA on the structural design of the golf club head. By means of the parametric design characteristics of Pro Engineer, various thickness and different shapes of the golf club head have been studied. The impact model will extract the ball velocities and spins for a given hit location on the club face which is analyzed by the software LS-DYNA. After that, the factors for influencing the dynamic analysis, such as the thickness and the shape of the hitting face, the off-center hitting, the ball velocity and spin, the stress distribution, and stress propagation in the head are further identified and measured. Finally, the effects of the factors described above have been analyzed quantitatively to investigate the maximum velocity of the ball and the sweet spot of the golf club head.

Modern engineering design tends to use computer simulations such as Finite Element Analysis (FEA) to replace physical experiments when evaluating a quality response, e.g., the stress level in a phone packaging process. The use of computer models has certain advantages over running physical experiments, such as being cost effective, easy to try out different design alternatives, and having greater impact on product design. However, due to the complexity of FEA codes, it could be computationally expensive to calculate the quality response function over a large number of combinations of design and environmental factors. Traditional experimental design and response surface methodology, which were developed for physical experiments with the presence of random errors, are not very effective in dealing with deterministic FEA simulation outputs. In this thesis, we will utilize a spatial statistical method (i.e., Kriging model) for analyzing deterministic computer simulation-based experiments. Subsequently, we will devise a sequential strategy, which allows us to explore the whole response surface in an efficient way. The overall number of computer experiments will be remarkably reduced compared with the traditional response surface methodology. The proposed methodology is illustrated using an electronic packaging example.

Textile composites can be tailored to meet specific thermo-mechanical requirements for structural applications. The focus of this research is on 2x2 biaxial braided composites since they have good stiffness and strength properties. Moreover, they have potentially better impact and fatigue resistance than laminated composites. Along with good properties, they have a reduced manufacturing cost because much of the fabrication can be automated. In order to exploit these benefits, thorough understanding of the effect of various factors on their material behavior is necessary. Obtaining effective mechanical properties is the first order of concern in any structural analysis. This work presents an investigation of the effect of various parameters like braid angle, waviness ratio, stacking sequence and material properties on the effective engineering properties of the 2x2 braids. To achieve this goal, three dimensional finite element micromechanics models were developed first. Extensive parametric studies were conducted for two material systems: 1). Glass (S2) fiber / epoxy (SC-15) matrix and 2). Carbon (AS4) fiber / Vinyl Ester (411-350) matrix. Equivalent laminated materials with angle plies and a resin layer were also analyzed to compare the difference in predictions from the full three dimensional finite element analysis of the 2x2 braided composites. A full three-dimensional stress state exists in braids even for very simple loading. In order to locate the potential damage spots, the stress distributions in both the matrix and the tows were predicted. The effect of braid angle on location and magnitude of peak stresses was determined.

Theoretical formulations, analytical solutions, and finite element solutions for laminated composite plate and shell structures with smart material laminae are presented in the study. A unified third-order shear deformation theory is formulated and used to study vibration/deflection suppression characteristics of plate and shell structures. The von K??rm??n type geometric nonlinearity is included in the formulation. Third-order shear deformation theory based on Donnell and Sanders nonlinear shell theories is chosen for the shell formulation. The smart material used in this study to achieve damping of transverse deflection is the Terfenol-D magnetostrictive material. A negative velocity feedback control is used to control the structural system with the constant control gain. The Navier solutions of laminated composite plates and shells of rectangular planeform are obtained for the simply supported boundary conditions using the linear theories. Displacement finite element models that account for the geometric nonlinearity and dynamic response are developed. The conforming element which has eight degrees of freedom per node is used to develop the finite element model. Newmark's time integration scheme is used to reduce the ordinary differential equations in time to algebraic equations. Newton-Raphson iteration scheme is used to solve the resulting nonlinear finite element equations. A number of parametric studies are carried out to understand the damping characteristics of laminated composites with embedded smart material layers.

Texas Department of Transportation (TxDOT) is currently designing its highway bridge structures using the AASHTO Standard Specifications for Highway Bridges, and it is expected that TxDOT will make transition to the use of the AASHTO LRFD Bridge Design Specifications before 2007. The objectives of this portion of the study are to evaluate the current LRFD Specifications to assess the calibration of the code with respect to typical Texas U54 bridge girders, to perform a critical review of the major changes when transitioning to LRFD design, and to recommend guidelines to assist TxDOT in implementing the LRFD Specifications. This study focused only on the service and ultimate limit states and additional limit states were not evaluated. The available literature was reviewed to document the background research relevant to the development of the LRFD Specifications, such that it can aid in meeting the research objectives. Two detailed design examples, for Texas U54 beams using the LRFD and Standard Specifications, were developed as a reference for TxDOT bridge design engineers. A parametric study was conducted for Texas U54 beams to perform an in-depth analysis of the differences between designs using both specifications. Major parameters considered in the parametric study included span length, girder spacing, strand diameter and skew angle. Based on the parametric study supplemented by the literature review, several conclusions were drawn and recommendations were made. The most crucial design issues were significantly restrictive debonding percentages and the limitations of approximate method of load distribution.The current LRFD provisions of debonding percentage of 25 percent per section and 40 percent per row will pose serious restrictions on the design of Texas U54 bridges. This will limit the span capability for the designs incorporating normal strength concretes. Based on previous research and successful past practice by TxDOT, it was recommended that up to 75% of the strands may be debonded, if certain conditions are met. The provisions given in the LRFD Specifications for the approximate load distribution are subject to certain limitations of span length, edge distance parameter (de) and number of beams. If these limitations are violated, the actual load distribution should be determined by refined analysis methods. During the parametric study, several of these limitations were found to be restrictive for typical Texas U54 beam bridges. Two cases with span lengths of 140 ft. and 150 ft., and a 60 degree skew were investigated by grillage analysis method.

Retroreflective Raised Pavement Markers (RRPMs) supplement other pavement markings to provide guidance to road users. Previous research concerning durability of the RRPMs suggests that their performance has been degrading over the years. One of the main causes for underperformance of the RRPMs is the lack of appropriate laboratory testing standards that can test the adequacy of the RRPMs to perform in field conditions. There is a need to modify the existing standards or develop new testing procedures that can better simulate field conditions. This requires identifying critical locations and magnitudes of stresses inside the markers during the tire-marker impacts that happen on roads. The goal of this research was to identify critical magnitudes and locations of the stresses in RRPMs during the tire-marker impacts by doing the finite element modeling and simulation of the impacts, and use the information to recommend laboratory testing procedures that could simulate real-world conditions. The researcher modeled and simulated the tire-marker impacts using the finite element tools Hypermesh and LS DYNA. He calibrated the material properties of the marker models to improve the tiremarker model. Based on the tire-marker impact simulations, the researcher concluded that the critical compressive stresses during impacts are located at the edge contacts of retroreflective sides with the top surface. The critical stresses may also occur at lower and upper corners of the marker. The other areas, especially the lower half of the marker, had tensile stresses. Angle of impact was found to be a critical external variable that affected the stresses inside the markers and the marker-pavement interface forces. The researcher then modeled and simulated a few laboratory-testing procedures that could simulate the field performance of the RRPMs. Based on these simulations, the researcher recommended that the ASTM compression test for evaluation of RRPMs be continued or a similar test be developed. He suggested development of one new test (named as offset compression test) that could better replicate the field conditions. He also recommended having a review of the ASTM flexural test.

A phenomenological cohesive term is proposed and added to an existing cohesive constitutive law (by Roy and Dodds) to model the crack tip high inertia region proposed by Gao. The new term is attributed to fracture mechanisms that result in high energy dissipation around the crack tip and is assumed to be a function of external energy per volume input into the system. Finite element analysis is performed on PMMA with constant velocity boundary conditions and mesh discretization based on the work of Xu and Needleman. The cohesive model with the proposed dissipative term is only applied in the high inertia zone i.e., to cohesive elements very close to the crack tip and the traditional Roy and Dodds model is applied on cohesive elements in the rest of the domain. It was observed that crack propagated in three phases with a speed of 0.35cR before branching, which are in good agreement with experimental observations. Thus, modeling of high inertia zone is one of the key aspects to understanding brittle fracture.

A non-contacting steel plate conveyance system based on the linear induction motor scheme, which can provide lift and propulsive forces simultaneously, is proposed. It has the features of high power density, direct drive, simple mechanical structure, and being able to reduce the operation noise. A magnetic equivalent circuit method and electromagnetic theory incorporating with 3-D finite element analysis are involved to investigate the static and quasi-dynamic properties and confirm the electrical and mechanical designs. To realize the dynamic behavior and develop the closed-loop control, a proper stationary reference frame transformation of the system voltage equations is also introduced. By considering the practical operational environment, a fuzzy-based control structure integrated with remote optical measurement system has been established and implemented by a DSP-based controller combined with required peripheral circuits. The experimental results show the applicability of such control strategies. With the systematic procedures for design, analysis, and control provided in this dissertation, implementation feasibility of the proposed system can be conveniently demonstrated.

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