Papers by Author: Kai Ming Yu

Abstract: This paper aims at presenting an experimental investigation to obtain the optimum formability of light-weight alloys under the multi-stage forming process. Titanium alloy sheets (Ti-6Al-4V) and aluminium alloy sheets (AA5052) are selected as forming specimens. The special fixture with heating device is applied in order to carry out the prestraining process. The swift forming test at warm-forming condition is performed for measuring the limit dome heights after the multi-stage formign process. The outcomes of this investigation are valuable for engineers to design and fabricate high-quality light-weight components efficiently.

Abstract: The cooling system of a plastic injection mould is important as it affects the quality and productivity of the polymeric components or assemblies. Contemporary cooling channel design is confined to simple configurations of straight-drilled coolant passageway around the mould insert. Undesirable defects resulted during injection moulding, such as warpage, are inevitable. The application of rapid tool (RT) based on solid freeform fabrication (SFF) technologies with conformal cooling channel (CCC) design has provided a profound opportunity in quality improvement of polymeric components. In this study, a novel design of variable radius conformal cooling channel (VRCCC) is proposed to achieve better uniform cooling performance. Thermal-FEA and melt flow analysis are used to validate the method.

Abstract: Nowadays’ optical frames are the result of a collaboration between designers and engineers; it is a combination of high technology and art. Around 250 technical operations are performed in order to make a high-quality metal frame, and there are 120 to 180 operations to make a plastic frame. Although the Asian manufacturers of optical frames are prevailing in the world market, a relatively rudimentary trial-and-error method is being used. A more systematic and analytic approach is thus needed for them to grasp the evolution trends in the competitive market. This paper discusses how Gabriel Tarde’s diffusion S-curve and the TRIZ theory can be employed to analyze the evolution trends in optical frame design and manufacturing.

Abstract: Nowadays more and more aesthetic product developments, assemblage and decoration designs are taking aesthetically appealing forms of natural objects such as rough terrain, ripples on lakes, coastline and seafloor topography. They are mathematical definable via fractal geometry theory and emerge to attract a lot of attention. However, not many methods for manufacturing of fractal objects have been reported in the literature and no previous research papers concern the manufacturability of fractal geometry. The paper will, thus, give a tentative classification and nomenclature of fractal geometry. Then, a state-of-the-art overview of manufacturing techniques is presented. By bridging the gap between fractal geometry and manufacturing, those processes that are promising to manufacture the three dimensional (3D) fractal objects will be highlighted. Afterward, a brief overview of limitation of those processes will be discussed.

Abstract: Nowadays, with the advances of Finite Element Analysis (FEA) packages, some of the engineering and design problems such as stress or thermal deformation can be successfully solved. These are convenient for better incorporating the design constraints of various tasks such as injection molded parts, or rapid prototyping and tooling. Mesh generation is the major step of finite element method for numerical computation. Common types of mesh include triangulation or tetrahedralization. During the mesh generation process, we always find difficulty in the formation of a uniform, non-conformal mesh. The undesirable mesh will adversely influence the accuracy and meshing time of the model. This paper will, thus, propose an effective approach to extend to threedimensional (3D) mesh generation by octree balancing method so as to adjust the mesh pattern. In this paper, the implementation of octree balancing will be explained and illustrated with real life example. The proposed method includes three main steps. Problematic unbalanced octants will be detected and Steiner points will be added as appropriate before the tetrahedral mesh generation. The balanced octree will form good tetrahedral meshes for further analysis. Then the balanced and unbalanced meshes will be compared for efficiency and accuracy for mesh generation.

Abstract: Cathodic Arc Physical Vapor deposition (CAPVD) uses a high current, low and negative voltage arc to vaporize a cathodic electrode (cathodic arc) and deposit the vaporized material on a substrate. The vaporized material is ionized in a vacuum chamber and the substrates are usually biased so as to accelerate the ions to the substrate surface. CAPVD provides a very dense film with excellent adhesion to the substrates. Therefore, this technique is mainly used to deposit on cutting tools such as end mills, drills, inserts, plastics and metal molds and high wear resistance tribology components. However, this coating technique will produce unwanted micro particles (droplets) [1] which usually are the target materials that cannot be reacted in coating process. These particles will affect the coating roughness and the surface morphology. To optimize this condition, Taguchi method is introduced to obtain the best experimental parameter settings. In this study, Atomic Force Microscope (AFM) is used to analyze the roughness of the coating for the following factors: bias voltage, arc current, nitrogen pressure and coating thickness.