Kuo-Cheng Huang

Fabrication of a double-sided micro-lens array by a glass molding technique

In recent years, micro-lens arrays (MLAs) have become important elements of optical systems. One function of MLAs is to create a uniform intensity of light. Compared with one-sided MLAs, the uniformity of light intensity increases with double-sided MLAs. MLAs fabricated by glass can be used in higher temperature environments or in high-energy systems. Glass-based MLAs can be fabricated by laser machining, photolithography, precision diamond grinding process and precision glass molding (PGM) technologies, but laser machining, photolithography and precision diamond grinding process technologies are not the perfect approach for mass production. Therefore, this paper proposes a method to fabricate a mold by laser micro-machining and a double-sided MLA by a PGM process. First, a micro-hole array was fabricated on the surface of a silicon carbide mold. A double-sided MLA using two molds was then formed by a PGM process. In this paper, the PGM process parameters including molding temperature and molding force are discussed. Moreover, the profile of a double-sided MLA is discussed. Finally, a double-sided MLA with a diameter of 20 mm, and lenses with a height of 52 µm, a radius of 851 µm and a pitch of 700 µm were formed on glass.

Analytical transient analysis of layered composite medium subjected to dynamic inplane impact loadings

In this study, the dynamic transient response of a layered composite with n layers under dynamic inplane impact loading on the surface is investigated in detail. One of the objectives of this study is to develop an effective analytical method for determining transient solutions. Complete solution of the contribution for each wave is expressed in an explicit form. These solutions will provide reliable solutions that can guide the development of numerical methods. In analyzing this problem, the waves reflected and refracted by the interfaces within the composite must be taken into account, which will generate infinite waves on each composite layer and make the problem extremely complicated to analyze. The problem is solved by using the Laplace transform method and the inverse transform is evaluated by means of Cagniards method. The transient responses of stresses and displacement in the transform domain on each layer are expressed in a closed form. The equation for each wave front propagating in the layered composite is determined in this study. For the numerical investigation of the transient response of stress, a two layered composite medium is analyzed in detail.

Exact transient solutions of buried dynamic point forces for elastic bimaterials

The exact transient closed form solutions for applying time dependent point forces at a depth below the interface of dissimilar solids are obtained in this study. The problem is solved by application of Laplace transform methods. The inverse transforms are evaluated by means of Cagniards method. The equations of wave fronts for reflected and refracted waves induced from the bimaterial interface by the incident waves are determined in this study. The corresponding static solutions of stresses and displacements are reduced from the obtained transient solutions. Numerical results of stress fields during the transient process are obtained for different cases and compared with the corresponding static values.

Wave propagation in layered elastic media for antiplane deformation

Abstract In this study, a composite laminate with n layers subjected to dynamic antiplane impact loading on the surface is investigated in detail. The transient responses of stresses and displacement on each layer are expressed in a closed form. For the numerical investigation, a two-layered composite laminate is considered. In analyzing this problem, the reflections and refractions of stress waves must be taken into account, which will generate infinite waves on each composite layer. In some classes of dynamic problem, the ability to find a static field may hinge on waiting for the wave fronts to pass and the transient to die away. The characteristic time after which the transient effect can be neglected is investigated in detail.

The Mixed Processing Models Development Of Thermal Fracture And Laser Ablation On Glass Substrate

As the industries of cell phone and LCD TV were vigorously flourishing and the manufacturing requirements for LCD glass substrate were getting higher, the thermal fracture cutting technology (TFCT) has progressively become the main technology for LCD glass substrate cutting. Due to using laser as the heat source, the TFCT has many advantages, such as uniform heating, small heat effect zone, and high cutting speed, smooth cutting surface and low residual stress, etc. Moreover, a general laser ablation processing or traditional diamond wheel cutting does not have the last two advantages. The article presents a mixed processing of glass substrate, which consists of TFCT and laser ablation mechanisms, and how to enhance the cutting speed with little ablation laser energy. In this study, a 10W Nd:YAG laser and a 40W CO2 laser are used as the heat source of TFCT and laser ablation processing, respectively. The result indicates that the speed of the mixed processing is more than twice the speed of TFCT. Furtherm...

Comparison of flow patterns between plasticine and aluminium alloys in hot-precision forging

Abstract Flow patterns, folding problems and die filling in hot precision forging of aluminium alloys are simulated by physical modelling using plasticine. In order to study the reliability of the simulation, a forged product of complex geometry has been chosen. It is found that only the correct direction of the layers of the stacked plasticine blanks can have a similar folding problem as that in alloy products. The fracture mode caused by temperature rise due to plastic deformation in an aluminium workpiece cannot be found in the compression of plasticine. Because the forgeability of plasticine is much better than that of aluminium alloys, the simulation of die filling cannot provide correct information for the hot precision forging of aluminium alloys. Moreover, the surface finish in hot precision forging cannot be simulated by physical modelling.

Full field analysis of an anti-plane interface crack subjected to dynamic body forces

In this study, the transient full field response of an interface crack between two different media subjected to dynamic body force at one material is investigated. For time t < 0, the bimaterial medium is stress free and at rest. At t = 0, a concentrated anti-plane dynamic point loading is applied at the medium as shown in Fig. 1. The total wave field is due to the effect of this point loading and the scattering of the incident waves by the interface crack. An alternative methodology that is different from the conventional superposition method is used to construct the reflected, refracted and diffracted wave fields. A useful fundamental solution is proposed in this study and the full field solution is determined by superposition of the fundamental solution in the Laplace transform domain. The proposed fundamental problem is the problem of applying an exponentially distributed traction (in the Laplace transform domain) on the interfacial crack faces. The Cagniard–de Hoop method of Laplace inversion is used to obtain the transient solution in time domain. Exact transient closed form solutions for stresses and stress intensity factors are obtained. Numerical results for the time history of stresses and stress intensity factors during the transient process are discussed in detail.

Surface Formation of Nano- / Micro- Structures on Titanium Alloy Composites using Picosecond Laser Scanning Technology

This study reports on the development of picosecond laser system to titanium alloy surface treatment applications. In the picosecond laser-scanning system, that is based on the fiber-optics laser source and integrated with a designed optics / optical machine design and control technology of scanning system. To analyze the laser material interaction, the laser fluence, pulse repetition frequency of laser source, position of focused points, scan speed and pulse duration were adjusted. After laser surface treatment, the surface roughness and surface morphologies of treated surface were evaluated by using a field emission scanning electron microscope. Moreover, the contact angle measurement was used to analyze the hydrophilic and hydrophobic properties of the treatment surface with micro/ nanostructures.

Laser Drilling of a 7-layer Flexible Printed Circuit Board using a Pulsed Ytterbium Fiber Laser System

Recently, laser-processing industry is becoming increasingly popular because of its advantages of low cost, fast and good energy efficiency. The electric circuit board manufacturers also began to import related laser processing technology to improve the productivity. This paper presents the laser drilling process and quality analysis of the 7-layer flexible printed circuit (FPCB). A laser drilling system pulsed Ytterbium fiber laser, expander device, focal lens, galvanometric scanner and XY-axis manual stage was used to perform the hole cutting of the multilayer-layer FPCB. This study succeeded in establishing a comparing procedure, which enabled the characteristic comparison between the various experimental conditions. We believe that this study provides a useful database for FPCB drilling technology.

Parameters optimization of laser electrode patterning on ITO/glass using multi-performance characteristics analysis

The objective of this study was to obtain the optimal parameters for laser electrode patterning of indium-tinoxide (ITO) films coated on soda lime glass substrates; the parameters were determined through grey relational analysis. The electrode patterning parameters affecting the sheet resistance and optical transmittance of the film include the laser power, pulse repetition frequency, pulse duration, and focus point position. Multiple performance characteristics associated with the sheet resistance and optical transmittance were investigated by conducting experiments. An infrared (1064 nm) laser system was used to directly fabricate electrode patterns on ITO films, and the characteristics of the patterned films were systematically analyzed using an ultraviolet-visible-near-infrared spectrophotometer and a four-point probe instrument. The data obtained from the experiments were analyzed to optimize the laser patterning parameters correlated with multiple performance characteristics.