Assessing the impact of geometric design intent annotations on parametric model alteration activities

The effective representation and communication of design intent plays a crucial role in CAD model alteration activities. In history-based parametric modeling systems, design intent information is usually expressed implicitly within the model. However, there is evidence that suggests that an explicit representation can increase productivity and quality and facilitate the transferring of design knowledge throughout the different stages of the product lifecycle. In this paper, we assess the effectiveness of 3D annotations as mechanisms for explicit design intent representation and examine their impact in model alteration processes that require a direct interaction with the model's geometry. We present the results of a series of studies aimed at measuring user performance and model quality in two scenarios. First, we hypothesized that annotations are valuable tools to provide design information when inadequate modeling assumptions can be made by designers. Second, we evaluated annotations as tools to communicate design decisions when multiple options are available. In both cases, results show statistically significant benefits of annotated models, suggesting the use of this technique as a valuable approach to improve design intent communication.     

Design and optimization of zirconia functional surfaces for dental implants applications

Zirconia is becoming a promising solution for biomedical applications, namely for dental implants, due to its biocompatibility, and mechanical and aesthetical properties. Despite the constant developments in the dentistry field, strategies to promote an effective vascularization at the implant's surface and consequently improved osseointegration are still not enough.In this sense, with the aim of promoting the vascularization at the implant's surface, zirconia surfaces with micro-channels were designed and evaluated regarding their hydrophilicity and capillarity. A CAD/CAM system was used to design and produce the specimens and different techniques were used to characterize the surfaces. The obtained average surface roughnesses are in accordance with the literature for similar materials. Results revealed that the produced materials present high levels of hydrophilicity, whether in contact with water or FBS - Fetal Bovine Serum. Additionally, micro-channels with 200 μm of width and 100 μm of depth were the ones that presented higher capillarity, thus being promising solutions for the promotion of implants vascularization, and consequently improved osseointegration.     

Calculating the medial axis of a CAD model by multi-CPU based parallel computation

Computational efficiency is still a great challenge for the generation of the Medial Axis (MA) for complicated CAD models. Current research mainly focuses on CPU-based MA generation methods. However, most of the methods emphasize using a single CPU. The highly-efficient methods based on parallel computing are still missing. In this study, a parallel method based on multi-CPU is proposed for the efficient MA generation of CAD models using distance dilation. By dividing the whole model into several parts for which MAs are calculated in parallel and then combined, computational efficiency can be greatly improved in theory and the computation time can be reduced nearly K times if K CPUs are used. Firstly, an adaptive division method is proposed to divide the voxelized model into blocks which have nearly the same number of voxels to balance the computational burden. Secondly, the local Euclidean Distance Transform (EDT) is calculated for each block based on the existing distance dilation method. Thirdly, the complete inter-dilation method is proposed to compute the influence between different blocks to get a global EDT for each block. Finally, each block generates a sub-MA separately and then all the generated MAs are combined to obtain the final MA. The last three processes can be efficiently conducted in parallel by using multiple CPUs. Several groups of experiments are conducted which demonstrate the good performance of the proposed methods in terms of efficiency.     

From regional sensitivity to intra-sensitivity for parametric analysis of free-form shapes: Application to ship design

Robust Parametric Sensitivity Analysis (PSA) is a prerequisite for efficient shape optimisation via parametric modelling. A major challenge PSA has to handle is related to the fact that a parameter can be sensitive in certain local areas of the design space but become insensitive in others. Therefore, setting an applicable space for this analysis becomes a difficult task. In this paper, we introduce the concept of intra-sensitivity to identify parameters whose perturbation has a major impact on the sensitivity index of the remaining parameters. For this purpose, we firstly appeal to Active Subspace Method (ASM) and develop an ASM-based regional sensitivity analysis, which investigates parametric sensitivity in local regions of the design space and aids conducing to parameters’ intra-sensitivity. This regional analysis is applied in conjunction with a Dynamic Propagation Sampling approach, for tackling the computational complexity arising when high-dimensional problems are concerned. Once sensitive and intra-sensitive parameters are identified, then free-form features, correlated to these parameters, are evaluated using a feature saliency map built with the aid of Hausdorff distance. The so resulting methodology has been validated in the area of computer-aided ship design using two parametric modellers: the first one is a Procedural Deformation (PD) modeller which is based on T-splines and involves 24 parameters while the second one is based on Free-Form Deformation (FFD) and involves 104 parameters. The corresponding design spaces have been generated using a parent hull close to the KCS container ship and are analysed against hull’s volume of displacement and total resistance. Finally, the convergence performance of the various components of this approach is compared with state-of-the-art techniques.     

Engineering knowledge formalization and proposition for informatics development towards a CAD-integrated DfX system for product design

Target design methodologies (DfX) were developed to cope with specific engineering design issues such as cost-effectiveness, manufacturability, assemblability, maintainability, among others. However, DfX methodologies are undergoing the lack of real integration with 3D CAD systems. Their principles are currently applied downstream of the 3D modelling by following the well-known rules available from the literature and engineers’ know-how (tacit internal knowledge).This paper provides a method to formalize complex DfX engineering knowledge into explicit knowledge that can be reused for Advanced Engineering Informatics to aid designers and engineers in developing mechanical products. This research work wants to define a general method (ontology) able to couple DfX design guidelines (engineering knowledge) with geometrical product features of a product 3D model (engineering parametric data). A common layer for all DfX methods (horizontal) and dedicated layers for each DfX method (vertical) allow creating the suitable ontology for the systematic collection of the DfX rules considering each target. Moreover, the proposed framework is the first step for developing (future work) a software tool to assist engineers and designers during product development (3D CAD modelling).A design for assembly (DfA) case study shows how to collect assembly rules in the given framework. It demonstrates the applicability of the CAD-integrated DfX system in the mechanical design of a jig-crane. Several benefits are recognized: (i) systematic collection of DfA rules for informatics development, (ii) identification of assembly issues in the product development process, and (iii) reduction of effort and time during the design review.     

Parametric design of garment pattern based on body dimensions

Garment pattern-making is one of the most important parts in fashion design and production. However, the traditional pattern-making is an experience based work and very time-consuming. In this paper, we proposed a parametric design method of garment pattern based on body dimensions. Based on this method, we constructed a jeans' pattern recommendation system. The input items of the proposed system are three geometric constraint parameters (jean silhouette type, length and waist height) and three-dimensional constraint parameters (human body stature, waist girth and hip girth); the output of the proposed system are jeans' patterns. Also, four adjustable parameters (jeans' length, waist height, knee and leg opening) are designed to adjust patterns generated by the proposed system. If the jeans' pattern is not satisfying after virtual or real try-on, the adjustable input parameters of the proposed system can be applied for adjustment until the patterns are acceptable. Our proposed system can combine traditional pattern-making methods to generate jeans’ patterns automatically and rapidly, hence improving pattern-making efficiency significantly.     

动力学参数化可视化仿真软件研究与设计

为解决诸如导弹、多管火箭、火炮等武器系统在方案设计、优化迭代过程中缺少专用的针对动力学参数化仿真软件的问题,研究了多体系统动力学参数化软件理论与技术,开发了多体系统动力学参数化仿真与分析软件.软件集参数化建模、求解、结果可视化功能于一体,通过融合CAD建模方法和多体系统动力学理论,解决了CAD和CAE双向参数驱动,实现了几何模型和动力学模型设计参数无缝传递,为机械系统设计过程中的方案论证、模型优化、方案调整、试验规划、故障诊断等各个阶段提供了一种高精度仿真和方案快速优化设计的手段和数字化工具.     

汽车半轴楔横轧模具计算机辅助设计

针对楔横轧多楔精密成形汽车半轴模具设计计算和制造复杂难题,本文利用VB可视化程序对PRO/E进行二次开发,编制了汽车半轴楔横轧多楔模具的通用计算程序,计算出主楔和侧楔的端面移动量、轧齐曲线等数据,并将所有结果数据存放至Access数据库中,在PRO/E下生成三维实体模型,从而实现汽车半轴楔横轧多楔模具的计算机辅助参数化设计,为汽车半轴的规模化生产提供有效的数值工具.     

汽车保险杠注射模设计与制造

某汽车后保险杠尺寸较大 ,形状复杂 ,常规模具机构不能使用 ,脱模困难 ,最后将部分型芯做成活动型芯与塑件一并顶出 ,解决了问题。在模具的加工上 ,由于塑件形状复杂 ,故本模具的成型部件是在三维中进行实体设计 ,实现了设计、编程、加工一体化。     

冲裁模CAD中冲压力计算的研究与实现

对冲裁模CAD系统的冲压力计算进行了研究，对基于I—DEAS9平台的冲裁模CAD系统中冲压力计算提出了具体设计方案，通过实例说明该方案应用到三维数字化设计平台的冲裁模CAD系统中可以提高其工艺设计效率。