Matthew Ming Fai Yuen

A numerical study of the eigenparameters of a damaged cantilever

Abstract When a structure is subjected to damage, its dynamic response changes, characterized by shifts in the eigenvalues and modifications of the eigenvectors. Considerable effort has been put into investigating the relationship between the damage location, the damage size and the corresponding changes in the eigenparameters. In most cases, emphasis has been on using the shift in eigenvalues as a means of determining the damage location, and the information derived from the change in eigenvectors has largely remained obscure. In this paper a systematic study is presented of the relationship between damage location, damage size and the changes in the eigenvalues and eigenvectors of a cantilever when subjected to damage. A finite element model of a uniform cross sectioned cantilever was chosen to provide data for analysis. The changes in the eigenvalues and eigenvectors are shown to follow a definite trend in relation to the location and extent of damage.

From laser-scanned data to feature human model: a system based on fuzzy logic concept

This paper describes the development of a prototype system using fuzzy logic concept for constructing a feature human model, which is to be stored in a 3D digital human model database. In our approach, the feature human model is constructed by unorganized cloud points obtained from 3D laser scanners. Firstly, noisy points are removed, and the orientation of the human model is adjusted; secondly, a feature based mesh generation algorithm is applied on the cloud points to construct the mesh surface of a human model; lastly, semantic features of the human model are extracted from the mesh surface. Compared with earlier approach, our method strongly preserves the topology of a human model; more details can be constructed; and both the robustness and the efficiency of the algorithm are improved. At the end of the paper, in order to demonstrate the functionality of feature human models, potential applications are given.

Feature based 3D garment design through 2D sketches

Abstract This paper presents a new approach for intuitively modeling a three-dimensional (3D) garment around a 3D human model by two-dimensional (2D) sketches input. Our approach is feature based—every human model has pre-defined features, and the constructed garments are related to the features on human models. Firstly, a feature template for creating a customized 3D garment is defined according to the features on a human model; secondly, the profiles of the 3D garment are specified through 2D sketches; finally, a smooth mesh surface interpolating the specified profiles is constructed by a modified variational subdivision scheme. The resulting mesh surface can be cut and flattened into 2D patterns to be manufactured. Our approach provides a 3D design tool to create garment patterns directly in the 3D space through 2D strokes, which is a characteristic not available in other computer aided garment design systems. The constructed garment patterns are related to the features on a human model, so the patterns can be regenerated automatically when creating the same style of garment for other human models. Our technique can greatly improve the efficiency and the quality of pattern making in the garment industry.

Surface flattening based on energy model

Abstract This paper presents a method for three-dimensional surface flattening, which can be efficiently used in three-dimensional computer aided garment design. First, a facet model is used to present a complex surface. Then, a spring–mass model based on energy function is used to flatten the 3D mesh surfaces into 2D patterns. The surface elastic deformation energy distribution is depicted by a color graph, which determines a surface cutting line. The method presented here can efficiently solve flattening problems for complex surfaces. The accuracy of a developed surface can easily be controlled locally. Thus, compared to earlier methods, this method provides more flexibility for solving CAD and CAM problems.

Design automation for customized apparel products

This paper presents solution techniques for a three-dimensional Automatic Made-to-Measure scheme for apparel products. Freeform surface is adopted to represent the complex geometry models of apparel products. When designing the complex surface of an apparel product, abstractions are stored in conjunction with the models using a non-manifold data structure. Apparel products are essentially designed with reference to human body features, and thus share a common set of features as the human model. Therefore, the parametric feature-based modeling enables the automatic generation of fitted garments on differing body shapes. In our approach, different apparel products are each represented by a specific feature template preserving its individual characteristics and styling. When the specific feature template is encoded as the equivalent human body feature template, it automates the generation of made-to-measure apparel products. The encoding process is performed in 3D, which fundamentally solves the fitting problems of the 2D tailoring and pattern-making process. This paper gives an integrated solution scheme all above problems. In detail, a non-manifold data structure, a constructive design method, four freeform modification tools, and a detail template encoding/decoding method are developed for the design automation of customized apparel products.

A survey on CAD methods in 3D garment design

With the advance in virtual reality applications, garment industry has strived for new developments. This paper reviews state-of-the-art CAD methods in 3D garment design. A large range of techniques are selected and organized into several key modules which form the core of a 3D garment design technology platform. In each module, basic techniques are presented first. Then advanced developments are systematically discussed and commented. The selected key modules - digital human modeling, 3D garment design and modification, numerical integration of draping, 2D pattern generation, geometric details modeling, parallel computation and GPU acceleration - are discussed in turn. Major challenges and solutions that have been addressed over the years are discussed. Finally, some of the ensuing challenges in 3D garment CAD technologies are outlined.

Cloth simulation using multilevel meshes

Abstract In this paper, we present a fast cloth simulation method using multilevel meshes. To speed up cloth simulation while achieving realistic simulation results, the process of cloth simulation is divided into several phases. At each phase, the mesh size is smaller than that of the previous phase. In this article, a mass-spring model is developed for triangular meshes, a simple mesh refinement scheme is employed to refine the coarse mesh into the fine mesh, and collision detection methods for multilevel meshes are also described. The multilevel method is suitable for cloth draping simulation.

Reactive 2D/3D garment pattern design modification

This paper presents a new 3D garment simulation result update algorithm for the 2D garment pattern design modification. The proposed algorithm enables the 3D garment fitting simulation result directly to react to the modification in the 2D patterns. The algorithm performs a topological invariant deformation of the 2D pattern mesh after the boundary of the 2D pattern undergoes a topological consistent modification. The length of each of the edges in the mesh defined as the equilibrium state parameter is updated and then directly used in the 3D garment fitting simulation to update the original simulation result. The advantage of the proposed algorithm is that the mesh topology of the 2D garment pattern is preserved and thus simplifies the numerical scheme by maintaining the consistency of the matrix equation. With this approach, the 3D garment fitting simulation does not need to repeat the entire simulation for every modification and can react to the 2D pattern modification efficiently and speedily.

Virtual human modeling from photographs for garment industry

Abstract The research presented in this paper is to develop a technique of virtual human modeling for the garment industry from two photographs of a human body in two orthogonal views. Firstly, an efficient segmentation method is applied on the two photographs to obtain the contours of the human body. After this, a template-based feature extraction algorithm is introduced to determine the feature points on the human contours by human morphology rules. Finally, a view-dependent deformation technique is described to construct the virtual human body by using human contours. Our segmentation algorithm is derived from the Mumford–Shah segmentation technology and the level set formulation, and it is accelerated by applying multi-pyramid levels. The deformation technique is related to axial deformation. With our deformation method, the reference silhouettes (the front-view and right-view silhouettes of the template human model) and the target silhouettes (the front-view and right-view silhouettes of the human body from the photographs) are used to deform the template human model, which is represented by a polygonal mesh with predefined features. The self-intersection problem in the axial deformation is solved in our deformation approach. Compared with other virtual human modeling approaches, the speed of constructing the human model is increased; and our deformation technique has better continuity and local deformation properties. At the end of the paper, some potential applications for the garment industry are given to demonstrate the functionality of virtual human models constructed by our approach.

Investigation of moisture diffusion in electronic packages by molecular dynamics simulation

Moisture-related failure is one of the main concerns in the integrated circuit (IC) package design. To minimize such failure in multi-layered electronic assemblies and packages, it is important to develop a better understanding of the reliability at a molecular level. In this paper, molecular dynamics (MD) simulations were conducted to investigate the respective moisture diffusion into the epoxy molding compound (EMC) and at the EMC/Cu interface. Moisture diffusion coefficients into the bulk EMC material and at the EMC/Cu interface can be derived from the mean-squared displacements calculated from MD simulations. The MD results showed that the seepage along the EMC/Cu interface is more prevalent when compared to moisture diffusion into the bulk EMC and, thus, rendering it a dominant mechanism causing moisture induced interfacial delamination in plastic packages.