Materials Science Forum Vols. 505-507

Abstract: Recently, there has been a rapid development in computer technology, which has in turn led to develop the automated welding system using Artificial Intelligence (AI). However, the automated welding system has not been achieved duo to difficulties of the control and sensor technologies. In this paper, the classification of the optimized bead geometry such as bead width, height, penetration and bead area in the Gas Metal Arc (GMA) welding with fuzzy logic is presented. The Fuzzy C-Means (FCM) algorithm, which is best known an unsupervised fuzzy clustering algorithm is employed here to analysis the specimen of the bead geometry. Then the quality of the GMA welding can be classified by this fuzzy clustering technique, and the optimal bead geometry can also be achieved.

Abstract: This paper proposed a polishing path planning method of super accuracy mirror mold with free-form surface by curvature analysis. First, IGES files of free-form surfaces are read and the mold geometry is regenerated as B-spline surface by the Automatic Mold Polishing System (AMPS). By using the derivative properties of B-spline surface, normal vector and principal curvatures at any point of the surface are calculated. In addition, the effective contact width between polishing tool and mold surface based on the grain size and the principal radii of curvature is also determined. The minimum contact width in 3-D is mapped onto the (u, v) parameters of B-spline surface. Then a modified Peano fractal path with weaving function is calculated based on the effective contact width in the (u, v) coordinate. This Peano-weaving path was tested on an optical mold with free-form surface. The polishing result shows the method is very effective and achieves the level of mirror surface with roughness Ra 29nm.

Abstract: The objective of this paper is to develop a nonlinear recursive formulation for the dynamic analysis of robotic manufacturing systems. The nonlinear recursive equations are used for open-loop flexible manipulators that undergo large translational and rotational displacements. These equations are formulated in terms of a set of time invariant scalars, vectors and matrices that depend on the spatial coordinates as well as the assumed displacement fields, and these time invariant quantities represent the dynamic manufacturing couplings between the rigid body motion and elastic deformation. This formulation applies recursive procedures with the nonlinear equations for flexible manipulators to obtain a large, loosely coupled system equation of motion in robotic manufacturing systems. The numerical techniques used to solve for the system equations of motion can be more efficiently implemented in any computer systems. The algorithms presented in this investigation are illustrated by using standard mechanical joints for robotic manufacturing systems that can be easily extended to other special joints. The nonlinear recursive formulation developed in this paper is illustrated by a robotic manufacturing system using standard revolute mechanical joints.

Abstract: This paper studies the residual stress distributions and tip deflections of microfabricated bilayer cantilevers of varying beam thickness and platinum electrode length. The bilayer cantilevers discussed here are composed of low-stress silicon nitride films deposited on silicon beams. Platinum electrodes are deposited and patterned on the low-stress silicon nitride layers. A thermal elastic-plastic finite element model is utilized to calculate the residual stress distribution across the cantilever cross-section and to determine the cantilever tip deflection following heat treatment. A contact model is introduced to simulate the influence of contact on the residual stress distribution. The influences of the beam thickness and the platinum electrode length on the residual stress distribution and tip deflections are thoroughly investigated. The numerical results indicate that a smaller beam thickness leads to a larger compressive residual stress within the platinum electrode and delivers a larger tip deflection. The results also indicate that a larger platinum electrode length delivers a smaller tip deflection.

Abstract: This paper proposes a stress analysis model for the cracked PVC pipe. The cracked PVC pipe is rehabilitated with an inner composite epoxy material by a dig-free method. The optimal thickness which can get the maximal flow rate after rehabilitated will be found by the finite element model. When the crack width of the pipe with 324 degree crack angle is 30 mm, the optimal thicknesses will be obtained with the compression ratio of 5%. The optimal thicknesses of theφ 300 ,φ 400 , φ 500 and φ 600 PVC pipes are 0.6, 0.8, 1.1 and 2.5 mm respectively. With these optimal thicknesses, the flow rates of rehabilitated pipes are lager than 98% the flow rates of original pipes.

Abstract: The compensation of tool wear is the important topics for numerical control machining. The lower-hand controller has the basic G code function (G41/G42) to obtain the compensated cutter location for planar contour machining. However, the advanced controller with cutter compensation vector function should be employed in order to process the three dimensional compensated tool path. The purpose of this paper is to establish the algorithm for calculating the 3D cutter compensation vector and develop a generalized postprocessor system to obtain the NC code. Through the verification by the solid cutting simulation software, it confirmed the effectiveness of the proposed algorithm.

Abstract: Nodal displacements are referred to the initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian formulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid for structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One closed loop structure undergoing large deformations is analyzed to demonstrate the efficiency and validity of the proposed method.

Abstract: One of the most effective methods for enhancing edge quality is to prevent the tool from exiting the work part in a machining operation. Exit here refers specifically to the tool cutting edges moving out of the part at an edge while removing material. Only entrance burrs are allowed to occur in this condition, resulting in less serious edge defects. This study presents a two-stage geometric algorithm for avoiding tool exits in planar milling of 2D free form contours. The cutter positions causing the tool to exit the part are first detected; then a heuristic scheme is applied to generate new cutter locations with no tool exits. Experimental results show that edge quality is significantly improved. This work provides a feasible method for reducing edge defect in an automatic manner without the need of edge finishing, which is highly advantageous in meso-scale machining.

Abstract: Computer-aided analysis of rigid-body mechanisms is combined with the finite element analysis of flexible structures to develop a computer model and derive the equation of motion, incorporating the Lagrange multiplier, to be used in the dynamic analysis of multi-rigid-body mechanisms mounted on flexible support structures. The resulting equations are solved by numerical integration. Predicting and analyzing the performance of the full system, including the motion of the system components and the forcing condition, during the engineering design process will promote the success of the entire system. Finally, a machine gun system with a flexible mount is given as a numerical example. The results reveal that the interaction between the rigid-body mechanisms and its flexible support structures importantly determines the performance of whole system. This study considers only the planar case. Our future work will propose a more complicated fully three-dimensional model.

Abstract: This study presents a concept to fabricate micro-lens devices using high-aspect-ratio lithography, extra-hardness electroplating, and hot embossing processes. A bath of electroplating electrolyte will be formulated to fabricate micro-optics mold inserts with extra-hardness Ni-Co alloy. It is a novel method to increase the life of the mold insert during fabricating micro-lens devices. With this high hardness, the mold inserts can resist high abrasiveness and wearness so as to extend the mold cycle life and reduce the idle time of replacing mold plates during fabrications. Therefore, the process of fabrications of micro-lens can be more cost-effective. In this study, parametric effects of reflow time, and temperature on micro-lens profiles will be characterized and discussed. Finally, the optical properties such as focal length of developed micro-lens will be measured and tested.