Experimental characterization of sheet metal deformation during electro-hydraulic forming

A novel experimental technique, that combines high-speed imaging and digital image correlation techniques, has been developed and applied to investigate the high-rate deformation behavior of aluminum sheet during electro-hydraulic forming (EHF). Aluminum alloy AA5182-O sheets (1 mm thick and ∼152 mm diameter) were EHF deformed by high-energy (up to ∼21 kJ) pressure-pulse and the time-evolution of sheet-displacement, velocity, strain and strain-rate quantified. The data shows that different locations on the sheet undergo unique deformation history that is not apparent from the conventional post-mortem strain measurement (using etched circle/grid pattern) approach. Under the experimental conditions used in this work, the sheets were formed into domes and the maximum strain-rate observed was ∼664/s. Further, this maximum strain-rate was observed at an off-apex location and was ∼2.5 times greater than the maximum strain-rate at the dome apex. The maximum velocity observed was ∼100 m/s and the velocity-time data showed evidence of pressure-wave reverberations during the forming process. We believe that knowledge of such time-evolution of sheet deformation is necessary for a better understanding and accurate modeling of sheet formability that has often been reported to exceed quasi-static forming limits under high-rate forming conditions.     

Digital preservation of a Taiwanese historical settlement: Using 3D post-construction scan to develop an application framework and reference for Beipu Township

The purpose of this study is to build a post-construction 3D computer model of the historical settlement of Beipu Township in Taiwan as an application and reference framework. The cultural assets were digitally preserved in a post-construction and modified form as an attempt to fulfill the life-cycle management of data for culture workers, researchers and architects. The scan process was managed in four hierarchies: the whole region, the seven historical buildings, the four streets and the special features, in different scales. The final digital model integrates research results from all involved parties, integrates local practice needs, represents hypothesis in city development, enhances historical understanding and interpretation, and facilitates remote access.     

DataPlay产品的构成与特性

简单介绍了DataPlay产品的特性、技术规范与适用范围。     

An optical strain measurement system for asphalt mixtures

Knowledge of the conditions governing the initiation and propagation of cracks in hot mix asphalt (HMA) mixtures is a prerequisite for a comprehensive understanding of HMA cracking mechanisms. Traditional strain measurement sensors have proved to be not completely adequate in the sense that they do not provide pointwise measurements, thus not pinpointing the location of crack initiation, and not accounting for non-uniform strain distributions. This paper presents a digital image correlation (DIC) system for non-contact and full strain field measurements, conceived for the purpose of investigating the cracking behavior of HMA mixtures. The whole system was developed so as to account for the special nature of typical HMA testing configurations. An image matching technique (least squares matching) was employed for providing matches with sub-pixel accuracy. The performance of the method was investigated by several tests. The DIC system was shown to overcome the shortcomings of traditional on-specimen strain measurement devices achieving satisfactory accuracy compared to strain gauges.     

Effective packing of 3-dimensional voxel-based arbitrarily shaped particles

In many research areas including medicine and paper coating, packing of particles together with numerical simulation is used for understanding important material functionalities such as optical and mass transfer properties. Computational packing of particles allows for analysing those problems not possible or difficult to approach experimentally, e.g., the influence of various shapes and size distributions of particles. In this paper a voxel-based algorithm by Jia et al. [X. Jia, R.A. Williams, A packing algorithm for particles of arbitrary shapes, Powder Technology 2001, vol. 120, pp. 175-186.] enabling the packing of arbitrarily shaped particles, is memory- and speed-optimised to allow for simulating significantly larger problems than before. Algorithmic optimisation is carried out using particle shell area reduction decreasing the amount of time spent on collision detection, fast rotation routines including lookup tables, and a bit packing algorithm to utilise memory effectively. Presently several hundreds of thousands of complex arbitrarily shaped particles can be simulated on a desktop machine in a simulation box consisting of more than 10⁹ voxels.     

An analysis of safety-critical digital systems for risk-informed design

This paper quantitatively presents the results of a case study which examines the fault tree analysis framework of the safety of digital systems. The case study is performed for the digital reactor protection system of nuclear power plants. The broader usage of digital equipment in nuclear power plants gives rise to the need for assessing safety and reliability because it plays an important role in proving the safety of a designed system in the nuclear industry. We quantitatively explain the relationship between the important characteristics of digital systems and the PSA result using mathematical expressions. We also demonstrate the effect of critical factors on the system safety by sensitivity study and the result which is quantified using the fault tree method shows that some factors remarkably affect the system safety. They are the common cause failure, the coverage of fault tolerant mechanisms and software failure probability.     

在ISDN上建立桌面会议系统

本文对用ISDN作为传输介质的一些标准和多点技术作简要介绍 ,并讨论在ISDN这种介质上 ,部署桌面会议系统时需要注意的问题。     

数字调谐系统在组合音响上的应用

本文介绍了NEC公司大规模专用集成电路μPD1715G——016及其在组合音响上的应用,讨论了设计中的几点关键性问题,并分析了解决问题的方法和途径。     

激光数字波面干涉仪傅里叶变换移相干涉术

讨论了一种新的干涉图处理方法，能实时快速准确地提取干涉图信息，直接测量波面的位相分布，获得较高的位相分辨率和空间分辨率，使光学波面的检测精度达到λ／１００以上，并且实现了波面的的实时显示。     

数码空调在商务办公楼的应用分析

通过工程实例,分析和探讨数码空调在商务办公楼中应用。