Key Engineering Materials Vols. 579-580

Abstract: A violin bridge kept in place by the pressure of the four strings has a powerful effect on the tone of the instrument. Its dynamic mechanical behaviors are investigated using finite elemental modeling and experiments in this paper. Modal and frequency response analysis of an isolated bridge are carried out. Numerical results show that the frequency responses are related to the vibration modes of the bridge. Particularly, the bridge hill is due to the bridge itself, and linked to the in-plane rocking mode of the bridge near the bridge hill peak. Three-dimensional dynamic forces exerted to the violin plates by the strings and bridge are then experimentally measured using a dynamometer. The experimental results are then analyzed and correlated to the simulation. The frequency response analysis of an isolated bridge is demonstrated to be a potential tool to study the mechanical behaviors of the violin bridge.

Abstract: Based on the embedded flexible clutch mechanism as the breakthrough point, using ADAMS dynamic analysis software and ANSYS simulation analysis software, established the analysis model, the peak impact force between the different conditions of brake wheel and brake claw was obtained, the brake wheel and the brake pawl two allowable angular speed difference. At the same time to brake wheel and brake claw structure impact resistance ability as optimization objective, the different structural forms of brake wheel and brake claw structure peak impact in different conditions and the brake wheel and brake claw two permissible angular speed difference is analyzed and calculated.

Abstract: The flow field characteristics of lubricant liquid film of the laser surface textured micro-pore face mechanical seal were studied by Fluent software, and the effects of geometric parameters of micro pores and operating parameters on the sealing performance were analyzed. The results show that the hydrodynamic effect of the laser surface textured micro-pore face mechanical seal is very obvious, and micro-pores make the friction state between rotating ring and stationary ring change to fluid friction. It can also be found that the rotating speed, the medium pressure, the area density and the liquid film thickness have effect on the sealing performance, among these influence factors, the area density has the greatest effect on the sealing performance, and it should be 0.2-0.3.

Abstract: A kind of measuring device for overlap values is designed and described in this paper, which can be adapted to various types of servo slide valve, especially to the large flow valve. An automatically location of the spool is realized in this equipment, as well as the auto-centering. Also, a micro-drive mechanism structure acting with high precision is fabricated. The operating process is clarified in detail. An improved reliability of the whole testing system is achieved with help of this very configuration, result from which the accuracy of overlap value measurement is enhanced.

Abstract: There are many problems for manual measurement of oil thimble external thread parameters: human error, low efficiency, low precision for measuring instruments and high abrasion for its measuring head, so photology automatic measurement method is adopted. Automatic measurement is finished by the following method: obtaining image by plane Matrix CCD and a two-DOF motion platform, extracting digital image by digital image processing techniques, getting the thread parameters by reasonable algorithms and digital image detection technology. Through field experiment of measuring instrument prototype for TYG type oil thimble external thread parameters, Data error is very small, obtained data is precise, measuring efficiency and precision for measuring instrument are high, there is no equipment abrasion problem for the measurement process, the method is feasible.

Abstract: Hydrostatic vertical guideway is the key component of modern CNC equipments which is a common lubrication form of turret. In order to improve the cutting stiffness during processing, the hydrostatic vertical guideway in sliding seat during westbank ram processing. Take count different cutting force to analysis the thickness changing of hydrostatic oil film, and then the relation between cutting force and the thickness of oil film is obtained. Based on FVM, relation model between them is established and the limited condition including cutting force is T=100KN, flow flux of each inlet is 0.52L/min, pump of constant delivery type is applied, film thickness is 0.023mm and oil cavity depth is 2mm is numerical simulated. The Hydrostatic pressure field and film thickness under different condition of hydrostatic vertical guideway is obtained. The relation model between film thickness and custom forces is validated. Whats more, the regularity of cutting force influence that impacted on film thickness is revealed. The study is of vital theoretical significance for the improvement of machining accuracy of numerical control machine and the entire CNC equipment and provides valuable theoretical basis for the design of hydrostatic guide rail in engineering practice.

Abstract: The structure and composition of the air-cooled high speed motorized spindle for wood-working machine and some features relative to the metal cutting motorized spindle are introduced briefly. Then the main heat sources and heat dissipation mechanism of the air-cooled motorized spindle are thoroughly analyzed, finite element model of the air-cooled motorized spindle is built, the motorized spindles temperature distribution under thermal steady state and the influence of speed are analyzed. The results show that air cooling relative to the water or oil cooling has many advantages and reasonable heat dissipation structure design of air-cooled motorized spindle could meet the requirements of the high-speed motorized spindle for wood-working machine.

Abstract: Aiming at the demand of remanufacturing mechanical parts fatigue life prediction, the main methods of fatigue life prediction are reviewed and summarized. The finite element and dynamics combined simulation method has been widely used at present, whose advantages are that it is suitable for most of the mechanical parts, and the forecast cycle is short, and it can be analyzed combining with the parts actual working condition, but the prediction accuracy depends on the comprehensive degree to the service condition. The experimental method is the most traditional method, and the fatigue life value obtained by the method is reliable, but the method is entirely depend on experience, and the cost of experiments is expensive, so the feasibility is bad. The fatigue life analysis method can lower the dependence on large number of experiments, but there is a great distance between the predicting fatigue life and actual fatigue life in working environment. The metal magnetic memory non-destructive testing method doesnt damage the testing objects, but the method is still in the stage of further research at present. Finally, taking the number of experiments, prediction cycle, prediction accuracy, prediction cost and the complex degree of the principle involved in the prediction process as evaluation indexes, the finite element and dynamics combined simulation method is the best fatigue life prediction method according to the score values of each method calculated by the quantitative scores based on the expert evaluation method.

Abstract: Fast tool servo (FTS) is widely utilized to fabricate optical freeform surfaces with nanometric surface roughness and with sub-micrometric form errors. FTSs dynamics character plays the major part in many factors that influence machining error. In this paper, a dynamic model for FTS is built up to describe its dynamic and to analyze the effects on machining error under different work frequencies. It was found that FTS dynamic mainly affect the Y direction machining accuracy of the workpiece surface, with the increase of the working frequency of FTS, the error caused by FTS dynamic also increases rapidly.

Abstract: Aiming at exploiting the impact of filling rate and pressure difference on thin-wall product during filling stage of differential pressure vacuum casting (DPVC) process and based on Yeoh model, a finite element mathematical structure model of silicon rubber is proposed. Employing nonlinear Finite Element Method (FEM), the impact of soft moulds deformation on products dimensional precision during different pressure difference is studied. Finally, the experiment carried out on a sample machine verifies that the solution of established finite element mathematical structure model of silicon rubber is very close to experiment result and thus provides an effective method for optimizing the pressure difference and mould optimized design.