Laser forming is an innovative technique that uses a defocused laser beam to form sheet metal by thermal stresses rather than external forces. Promising potential applications of laser forming include rapid prototyping, straightening, aligning and adjusting of macro/micro-metallic components. Research to-date on laser forming has been largely focused, theoretically and experimentally, on the problem of characterization of process parameters on the forming results, and computational simulations of laser forming remain limited only providing the insight into the process. This study investigates the laser forming processes using the finite element analysis with respect to material responses during the processes, including complex processes, process optimization, process reliability and the effects of thermal and mechanical material properties. The first part of this thesis describes a nonlinear transient three-dimensional heat transfer finite element model and a rate dependent three-dimensional deformation model, which are developed for the laser forming simulations. Simulations are performed using an indirect coupled thermal-structural method for the processes of a straight-line heating, a circle-line heating, and a laser micro-adjustment. The thermo-mechanical behaviours during the straight-line heating process are presented in terms of temperature, stress and strain, and displacement distributions. The emphasis in the circle-line heating simulations is placed on the characterization of the quality of the deformed geometry by obtaining the radial and circumferential waviness. The micron size movements induced by laser point heating are focused the simulations of the micro-adjustment process. Simulation results are validated by comparison with published data or correlation to engineering point of view. The second part of this thesis presents the development of an effective method to determine optimum process parameters in laser forming. For the process optimization, design optimisation techniques are introduced into the finite element analysis of the laser forming process. The optimum parameter values to produce a predefined bend angle of 3° in the straight-line heating process are sought by two optimization procedures - one is the procedure involving the non-gradient method and the other is the gradient-based method. Optimum values of laser power, feed rate, beam diameter and number of passes are determined to produce a predefined bend angle in a multiple straight-line heating process using the two optimization procedures. A more suitable optimisation method for laser forming is chosen, which is used for a new optimisation problem to generate a maximum bend angle in a single pass of laser forming. In the third part of this thesis, a strategy to assess the reliability of the laser forming process is established by employing a well-known reliability analysis method, the Monte Carlo simulation. Robustness of the straight-line heating process of producing 3° with the optimum parameters determined by process optimization is evaluated with regard to the uncertain input variables of laser power, feed rate, plate thickness and coefficient of thermal expansion via the Monte Carlo simulations based on the finite element simulations of the process. The final part of this thesis identifies the effects of material properties on the bend angle resulting from laser forming. Process sensitivity to the properties of coefficient of thermal expansion, thermal conductivity, specific heat capacity and elastic modulus is investigated by measuring the Pearson product-moment correlation coefficient between the properties and the bend angle, which are based on the Monte Carlo simulations of laser forming. The conclusion is that the developed finite element models contribute to a better understanding of the laser forming process, and the optimization procedure is able to be used for straightening, aligning and adjusting of components.

Compliant mechanisms are useful for improving existing machines and creating new ones that were not previously possible. They also help us to think of new methods and technologies needed to both improve existing systems as well as manufacture systems that have not been done before. The purpose of this thesis is to show novel implementations of compliant mechanisms into folding systems, and to show new methods for fabricating such mechanisms with nontraditional materials and on difficult scales. Folding systems are shown in furniture applications with chairs, stools, and childcare furniture applications as results of research into how such structures could be created with compliant mechanisms to be deployed from a flat state. Compliant mechanisms are also shown to be folded by a laser into simple mechanisms and into a potentially more complex parabolic reflector. Small-scale flexible (or compliant) mechanisms are valuable in replacing rigid components while retaining comparable motion and behavior. However, fabricating such mechanisms on this scale (from 0.01 to 10 cm thick) proves difficult, especially with thin sheet metals. The manufacturing method of laser forming, which uses a laser to cut and bend metal into desired shapes, could facilitate this fabrication. However, specific methods for designing mechanisms formed by lasers need to be developed. This work presents laser forming as a means for creating compliant mechanisms on this scale with thin sheet metal. The unique challenges for designing mechanisms to be laser-formed are explored, and new adaptations of existing designs are fabricated and discussed. The design of basic "building blocks" and features are developed for several mechanisms: a parallel-guided mechanism, a cross-axis flexural pivot, a LET joint array, a split-tube flexure, and a bi-stable switch. These mechanisms are shown to perform repeatable behavior and motion comparable to existing non-laser-formed versions. The further possibilities for fabricating compliant mechanisms with laser forming are explored, as advanced applications can benefit from using lasers to create compliant mechanisms from thin sheet metal. One such possible system is a parabolic reflector, which is useful for making solar collectors and antennas. Such shapes have been developed in various patterns and typically manufactured out of rigid components. Applications for these systems could benefit from paraboloids that can fold up and be deployed into a final shape. This work presents a conceptual method for designing a flat-foldable paraboloid and a means for its fabrication using laser forming.

Sheet metal forming has found increasing applications in modern industries. To eliminate use of expensive tools during product development, thermal forming, a rapid prototyping process that is flexible enough to decrease costs has been developed. Thermal forming processes use a heat source to perform the required deformation mainly by creating a thermal difference along the thickness of the sheet. Gas flames, lasers and plasma heat sources have been used for sheet metal bending by thermal forming. An alternative to laser and gas flames, plasma-jet forming has been developed that uses a non-transferred plasma arc as a heat source. The plasma-jet forming system uses a highly controllable non-transferred plasma torch as a heat source to create the necessary thermal gradient in the sheet metal that causes the required plastic deformation. Various experiments to produce simple linear bends and other complex shapes have been conducted by using different scanning options and coupling techniques. A computer simulated model using finite element method is being developed to study key parameters affecting this process and also to measure the thermal transient temperature distribution during the process. A predictive model to relate the deformation to the temperature gradient for various materials is being developed. Simulation results that are in accordance to experimental observations will further improve this material forming process to be highly controllable and more accurate