Advanced Materials Research Vol. 664

Abstract: A generic heat generation equation with the heat transfer has been developed for pure mechanical loading. Frequency dependent temperature field can be obtained on a specimen subjected to pure mechanical, cyclic or non-cyclic loading. Results have been compared with the literature and a good agreement has been found with the experimental results. Applications and effectiveness of the equation is highlighted in predicting the fatigue damage in case of high cyclic or vibration fatigue.

Abstract: In this paper, we base on the simulation analysis of the electro-hydraulic servo system about dual hydraulic cylinders parallel driving Multi-Stud Tensioning Machine, focus on the dynamic characteristics of a single hydraulic cylinder (asymmetric hydraulic cylinder), make use of Matlab Simulink module to carry on to imitate, and design a PID controller to correct the system. The results of simulation prove correctness of the system mathematic model, and the stability of the system is obviously improved.

Abstract: The purpose of present study is to identify the possibility of predicting the physical features of circular cylinder in two dimensional for a wide range of Reynolds number using a modified turbulence model. The modification is focused on the turbulence length and intensity. The drag coefficient and the Strouhal number were calculated and compared with the existing experimental data. The contour of vorticity and pressure gradient were also presented. Although variation up to 159% was noted in the drag coefficient, it was just on a particular Reynolds number.The simulated outputs of Strouhal number, pressure coefficient and vorticity contour indicated reasonable agreement with the experimental data. The modified turbulence model has showed potential in simulating the flow around the circular cylinder.

Abstract: This work is carried principally by simulation efforts using computer-modeling software (COMSOL). The developed 2D model includes the coupling between electromagnetic and thermal fields, and takes account of the nonlinear behaviour of material properties versus temperature. Several steps were followed to reach this goal. First, a 2D finite element model of a gear was developed in order to simulate the induced currents density and temperature distributions for various frequencies and external currents applied in the coil. Second, the temperature profiles were compared using the ratio between the skin depth and the teeth height. In geometry cases, it was possible to dose the power level of the medium (MF) and high (HF) frequencies to reach a desired uniform case depth. The MF and HF powers are simulated sequentially in order to better concentrate heat in the tooth tip and root of gear. The obtained results help process developers to select the proper parameters for the induction machine in order to achieve the desired hardness profile.

Abstract: An embedded particle swarm optimization (PSO) technique combined with virtual pheromones deposition and rules for artificial bird flocking is proposed to handle an area coverage problem using a swarm of mobile robots. A simulation tool VERA that was developed to simulate a swarm behavior of a group of mobile agents is described. Results of simulation experiments and tests on Lego robots that prove the concept are presented. Results are discussed and future development is suggested in the end of the paper.

Abstract: In this paper, an exoskeleton mechanical finger for rehabilitation has been designed. It has two finger knuckles which are driven by two cylinders separately. In the simulation process of ADAMS, the two cylinder driving stems are set different movement speeds and then the two finger-knuckles can be tracked as specific trajectories. The joint force and the torque curve of the exoskeleton mechanical finger at the point of the two knuckles can be got at different cylinder driving speeds.

Abstract: Nowadays the method based on demodulation by envelope finds wide application in industry as a technique for evaluation of bearings and other components in rotating machinery. In recent years the application of Wavelets for fault diagnosis in machinery has also obtained good development. This article demonstrates the effectiveness of the combined application of Wavelets and envelope technique (also known as HFRT High-Frequency Resonance Technique) to remove background noise from signals collected from defect bearings and identification of the characteristic frequencies of defects. A comparison of the results obtained with the isolated application of only one method against the combined technique is performed showing the increased capacity in detection of faults in rolling bearings.

Abstract: Thermally induced errors play a critical role in controlling the level of machining accuracy. They can represent a significant proportion of dimensional errors in produced parts. Since thermal errors cannot totally be eliminated at the design stage, active errors compensation appears to be the most economical and realistic solution. Accurate and efficient modeling of the thermally induced errors is an indispensable part of the error compensation process. This paper presents an integrated and comprehensive modeling approach for real-time thermal error compensation. The modeling process is based on multiple temperature measurements, Taguchi’s orthogonal arrays, artificial neural networks and various statistical tools to provide cost effective selection of appropriate temperature variables and modeling conditions as well as to achieve robust and accurate thermal error models. The experimental results on a CNC turning center confirm the feasibility and efficiency of the proposed approach and show that the resultant model can accurately predict the time-variant spindle thermal drift errors under various operating conditions. After compensation, the thermally induced spindle errors were reduced from 19m to less than 1 m. The proposed modeling optimization strategy can be effectively and advantageously used for real-time error compensation since it presents the benefit of straightforward application, reduced modeling time and uncertainty.

Abstract: The working process of a lean burn natural gas spark ignition engine was simulated with a 3-D CFD software package AVL-FIRE. Such simulations were made to analyze and understand the flow field, fuel/air mixture distribution, ignition and flame propagation. The simulations provide basis for the optimization of the combustion system of the engine. Two injection strategies for the pre-chamber enrichment were established and compared. The results indicate that with enrichment injection in the pre-chamber, the fuel/air equivalence ratio is precisely controlled in the range of 1.0 to 1.1, stable ignition in the pre-chamber is ensured, and fast initial flame propagation in main combustion chamber is realized.

Abstract: The current situation of air supply pressure product verification of the air-to-air missile equipment is analyzed in air force, the existing problems of the mode operation, the actual implementation and other aspects are pointed out, suggestion for improvement is put forward, and a preliminary scheme of the calibration equipment is given.