Approach to assess a fast welding simulation in an industrial environment — Application for an automotive welded part

Fusion welding processes are widely used for joining metal structures, such as pipes, ships, and cars. In general, these joining processes offer a very good compromise between reliability, safety, cost and maintenance which are important issues in the current economical context. The negative heat effects of welding, i.e. distortions and residual stresses of the welded parts, are well known and many researches in this field have already been done in the last decades in order to minimize them. On the experimental side, many sophisticated procedures have become state of the art to deal with this problem. On the computational side, the improvement of the simulation algorithms and the computing power enables the simulations of many physical phenomena occurring during the welding process. The implementation of welding simulation techniques is nevertheless not an easy task and often associated with expert knowledge which hinders their global application in an industrial environment. This paper is focused on the industrial requirements of a welding simulation software with special respect to the needs of the automotive industry. The necessary information to run a welding simulation and the expectations of a weld specialist without deep knowledge in numerical methods are investigated. These expectations are tested on an automotive welded assembly with a commercially available welding simulation software designed especially for the needs of the automotive industry. A welding experiment is done and the measured temperature distributions and distortions serve as reference to validate the simulation results. The result quality of the simulations of temperature fields and distortions is in best agreement with experimental data. The workflow is well adapted for the considered industrial requirements and the time-tosolution as well as the computational costs are acceptable, whereas the efficient calibration of the heat input model is still a point which will be further investigated in current and future research works.     

Book reviews

R. S. Farrow, with J. M. Broadus, T. A. Grigalunas, P. Hoagland III, and J. J. Opaluch. 1990. Managing the Outer Continental Shelf Lands: Oceans of Controversy. New York: Taylor & Francis New York, 168 pp., paper.

Richard A. Kenchington. 1990. Managing Marine Environments. New York: Taylor & Francis, 248 pp.     

Surface intersection in geometric modeling of ship hulls

In this work a methodology is presented for the computation of the intersection of parametric surfaces, namely Non Uniform Rational B-Splines (NURBS), with special attention to some specific requirements for applications to ship hull modeling. The algorithm adopted and the steps of the proposed method are described, namely checking whether the surfaces intersect, preprocessing of linear surfaces with strong discontinuities, computation of starting points, marching along intersection curves, and approximation of the intersections with NURBS curves. Finally, the results of some intersection tests are presented and discussed. The results are validated by comparison with results of commercial codes.     

Almost disturbance decoupling control of mimo nonlinear system subject to feedback linearization and a feedforward neural network: Application to half-car active suspension system

A novel tracking and almost disturbance decoupling problem of multi-input, multi-output (MIMO) nonlinear systems based on feedback linearization and a multi-layered feedforward neural network approach has been proposed. The feedback linearization and neural network controller guarantees exponentially global uniform ultimate bounded stability and almost disturbance decoupling performance without using any learning or adaptive algorithms. The new approach renders the system to be stable with the almost disturbance decoupling property at each step when selecting weights to enhance the performance if the proposed sufficient conditions are maintained. One example, which cannot be solved by the existing approach of the almost disturbance decoupling problem because it requires the sufficient conditions that the nonlinearities that multiply the disturbances satisfy structural triangular conditions, is proposed to exploit the fact that the tracking and the almost disturbance decoupling performances are easily achieved by the proposed approach. In order to demonstrate the practical applicability, a famous half-car active suspension system is investigated.     

论香港地下空间开发的规划、立法与发展经验

 海滨城市香港山多平地少,土地是极为稀少的资源,但山岭地貌和坚硬晶质火成岩岩体很适合开发地下洞室和隧道。20世纪70年代、80年代起,就开始考虑发展地下空间,以满足都市发展的需求。为此,政府开始有计划地进行工程可行性研究,并进行相关的立法工作,为规范地下空间的开发,建立了一套完整的地下空间开发体系。结合工程实例,就香港地下空间开发的研究、规划、开发、管理和立法作简要介绍。     

Effects of gasoline, diesel, LPG, and low-carbon fuels and various certification modes on nanoparticle emission characteristics in light-duty vehicles

This study was focused on experimental comparisons of the effects of various vehicle certification modes on particle emission characteristics of light-duty vehicles with gasoline, diesel, LPG, and low-carbon fuels such as bio-diesel, bioethanol, and compressed natural gas, respectively. The particulate matter from various fueled vehicles was analyzed with the golden particle measurement system recommended by the particle measurement programme, which consists of CVS, a particle number counter, and particle number diluters. To verify particle number and size distribution characteristics, various vehicle emission certification modes such as NEDC, FTP-75, and HWFET were compared to evaluate particle formation with both CPC and DMS500. The formation of particles was highly dependent on vehicle speed and load conditions for each mode. In particular, the particle numbers of conventional fuels and low-carbon fuels sharply increased during cold start, fast transient acceleration, and high-load operation phases of the vehicle emission tests. A diesel vehicle fitted with a particulate filter showed substantial reduction of particulate matter with a number concentration equivalent to gasoline and LPG fuel. Moreover, bio-fuels and natural gas have the potential to reduce the particulate emissions with the help of clean combustion and low-carbon fuel quality compared to non-DPF diesel-fueled vehicles.     

Partial range scaling method based washout algorithm for a vehicle driving simulator and its evaluation

Unlike an actual vehicle, a vehicle driving simulator (VDS) has limited kinematics, workspace, and bounded dynamic characteristics making it very difficult to simulate dynamic motions of an actual vehicle. To solve these problems, a washout algorithm was developed. The developed algorithm restricts the workspace of the VDS to within the kinematic limit and makes the person driving the VDS perceive movement of an actual vehicle. However, the classic washout algorithm contains several problems, such as time delay and the generation of a wrong motion signal caused by characteristics of the filters. So the driver feels “simulator sickness,” such as fatigue, nausea, headache and so on because of differences between the sense of movement of the VDS and that of a real vehicle. In this paper, a partial range scaling method based washout algorithm, including a tilt coordination system, is developed to enhance the perception of motion and reduce simulator sickness. It is verified by a simulation, a survey, and a bio signal analysis using an electrocardiogram (ECG).     

Experimental investigation on the efficiency of the pulley-drive CVT

Because of their outstanding advantages over other transmissions, rubber V-belt pulley drive CVTs have been extensively used in low-power vehicles, such as scooters and snowmobiles. A rubber V-belt CVT installed on a snowmobile is used here to research transmission efficiency. The power loss of CVTs, including torque loss and speed loss, is studied based on an analysis of the transmission mechanism of CVTs. Experiments on CVT efficiency are conducted on a specific CVT test bench, on which the values of torque, speed, and displacement, etc., are measured. Results show that the variation trend of the efficiency is close to the operating conditions of CVTs and optimal structural parameters are given that can serve as a beneficial references for designing and tuning CVTs.