慢走丝电火花线切割加工中恒张力控制系统设计

文章针对慢走丝电火花线切割加工中遇到的诸多难题,提出利用恒张力控制系统的解决方案,给出了完整的系统构成和软硬件平台。该系统以单片机为核心,可自动控制伺服电机对线切割加工过程进行随动响应,实现恒张力控制;实验表明,该系统运行可靠,响应速度快,可以有效解决断丝问题和抑制电极丝的丝振幅值,并提高加工质量。

线切割加工中断丝的原因及对策

在深入研究快走丝线切割加工中断丝故障的基础上 ,分析了断丝的各种原因 ,并针对这些原因分别给出了各自有效的预防及处理方法。

Experimental research on static characteristics of special wire-rope isolator

Based on analysis of the work conditions and structural characteristics of the exterior pipeline of the aero-engine, a kind of cantilever-structure wire-rope isolator fitted to the exterior pipeline of the aero-engine is designed for supporting and damping purposes. By static experiments, the static hysteresis loop, the relationship of stiffness and amplitude, and the relationship between the energy dissipation coefficient and the amplitude are obtained. Analyses show that the wire-rope isolator presents obvious hysteresis characteristics, and the characteristics of the isolator, such as stiffness and damping, behave obviously nonlinearly when the amplitude value of deformation changes. At the same time, by changing the structure parameters of the wire-rope, the wirerope isolators can be made with different functions to satisfy different work conditions. The research results have important reference values for the application of the wire-rope isolator on the exterior pipeline of an aeroengine.

Advanced simulation of die wear caused by wire vibrations during wire-drawing process

An advanced simulation that considers the effect of wire vibrations was proposed for predicting accurately wear profiles of a die used in a wire-drawing process.The effect of wire vibrations,the changes in the wear profiles,and the generation of ringing during die approach were investigated by this simulation.Wire vibrations occurring between the die and the drum are governed by a partial differential equation called the wave equation,which is a function of the wire length,tension,density,and initial wire velocity.The wire-drawing process was simulated by the commercial code Abaqus FEA,and the die wear profiles were predicted by Archard’s wear model.The predicted profiles were compared with measured profiles of a worn drawing die after producing 5 t of AISI 1010 wire;the die was made of tungsten carbide with a Brinell hardness of HB 682.The profiles predicted by considering the effect of wire vibrations are in good agreement with the experimental data,indicating that the advanced simulation can be used to accurately predict the die wear profiles when ringing is observed during die approach.

Effect of fretting amplitudes on fretting wear behavior of steel wires in coal mines

Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.

Dielectrophoretic force distribution of growing microwires

The Dielectropheretic assembly of electrically functional microwires from nanopartical suspensions is introduced. Meanwhile growth mechanism of the microwires is discussed. The agglomeration is based on the polarization and mobility of particles caused by alternating electric fields, commonly referred to as dielectrophoresis (DEP). The spatial distributions of the electric potential, field and dieletrophoretic force are analytically calculated in terms of AC electrokinetics. The calculated results show that the electrophoretic force, very strong near the apex of the microwire, drops abruptly with increasing distance. The electrophoretic force near the apex of the microwire agrees well with the fact that the nanoparticles are highly concentrated at the end of the tip and subsequently aggregate to extend the wire in the direction of the field gradient.

Combined deformation of filament-wound cylinder and application to torsion vibration control

The combined deformation and mechanical properties of filament-wound cylinder of filament reinforced composite materials are investigated. A method of using filament-winding composites to reduce the amplitude of torsion vibration in the case of special stimulated vibration is established. A design formula of anisotropic filament-wound cylinder to reduce the torsion vibration of axle components is obtained. The results indicate that by putting the filament-wound cylinder on an axis, the torsion vibration of the axis can be reduced effectively.