Determination of waviness decrease rate by measuring the frequency characteristics of the grinding force in centerless grinding

In centerless grinding, it is difficult to optimize the grinding conditions for minimizing the workpiece roundness error because of the high number of process parameters such as center height angle, blade angle, and stock removal rate. We had previously proposed a function for evaluating grinding conditions, i.e., the waviness decrease rate, in order to automatically select the optimum process parameters. In order to build a closed-loop control system for the process parameters, however, it is necessary to find a practical way to determine the waviness decrease rate. In this paper, the relationship between the waviness decrease rate and the dynamic components of the grinding force was investigated analytically. It was found that the frequency characteristics of the waviness decrease rate show a similar tendency to those of the grinding force. A grinding force measurement system was built and experiments for measuring the frequency characteristics of the grinding force were carried out. As a result, it was confirmed that the waviness decrease rate can be determined by measuring the frequency characteristics of the grinding force.     

Low cost high sensitivity dynamometer

This paper concerns the dynamometer with magnetoelectric actuator. Its construction and functionality were described. The conducted tests allow to estimate a number of metrological parameters of the dynamometer. Several practical applications together with their results were shown.     

异步测功机组的设计、制作及使用

随着电动工具行业的发展,对电动工具功率测试精度的要求也在提高,针对电动工具性能测试的需要,设计、制造了异步测功机组,使我单位的电器检测室的电动工具的检测能力得到了提高,保证了监督检验任务的完成。     

基于Windows的测功器试验台半实物仿真优化技术

在设计和优化测功器试验台测控系统过程中,开发基于Windows平台的试验台半实物仿真优化技术,对监控组态软件的不同算法进行仿真与优化。文中设计了试验台半实物仿真方案,介绍了测控系统的组成,论述了Windows平台组态软件和仿真软件MATLAB的DDE数据传送方式,完成了测功器及发动机系统特性的模型辨识。最后给出了所提仿真技术应用于电涡流测功器仿真和PID控制算法优化的实例。     

加速度传感器在示功仪中的应用

文中介绍了加速度传感器ＡＤＸＬ０５的特性和工作原理,给出了用加速度传感器测量相对位移的原理和计算方法,这种算法的关键是觖了加速度零点校正和积分边界条件确定两上问题。现场试验表明：示功仪中采用加速度传感器测量相对位移是切实可行的。     

汽车动力性检测中路试与台试的差异性分析

本文针对目前在用汽车检测站在同一底盘测功机上对多种车型车辆进行动力性检测，造成测试结果可信度低、数据重复性差的现象。从研究道路试验和台架试验检测方法差异出发，分析了造成不同车型台试和路试检测结果差异的原因，为汽车动力性的台架试验提供理论分析依据。     

Development and Characterization of C/C-SiC Brake Disc

A new process was developed to produce full-size carbon/carbon-SiC brake discs consisting of two friction layers and a structural layer. Different lengths of chopped carbon fibers were used for the friction layers and structural layer. A preform of each layer was produced by hot-pressing a mixture of resin and carbon fibers. After pyrolyzing the preforms, the layers were joined by hot-pressing. Finally, liquid Si infiltration was performed to obtain a C/C-SiC brake disc. The tensile strength, compressive strength, and bending strength were 40, 46, and 61 MPa, respectively. The density of the disc was 2.1 g/Cm³. The heat transfer coefficient in the vertical direction was 16.5 W/m-°C, and it was 45.9 in the horizontal direction. The friction coefficients obtained under various braking conditions showed stable and suitable values, 0.2–0.6.     

Dynamic cutting force measuring

Piezoelectric dynamometer are generally used for force measuring. Delivered signals are distorted due to their self dynamic behaviour. Their dynamic characteristics are identified under normal machining operation. The proposed method is based on the interrupted cutting of a specially designed workpiece that provides a strong broadband excitation. The three components of the exciting force and the acceleration of the gravity centre of the dynamometer cover plate are measured simultaneously. Although the input acceleration components are correlated in the frequency bandwidth of interest, a method is presented to determine the nine terms of the dynamometer transfer matrix from only one cutting experiment. Series of different pulse excitations are carried out to validate the proposed method. Then, the determined transfer matrix is used for dynamic cutting force compensation under some milling operations.     

Monitoring Strategy of Thermal-Induced Convex Deformation of Workpiece in Surface Grinding

In surface grinding, the presence within the workpiece of a high temperature gradient causes a large thermal bending moment, which can cause over-grinding due to the induced convex deformation of the workpiece by the bending moment. The average grinding forces and acoustic emission (AE) are used to predict the over-grinding, based on the facts that the up-grinding force is larger than the down-grinding force, and the AE is larger in up-grinding. Hence, over-grinding can be detected between passes from the mean values of the grinding forces and AE during grinding. Because of the positional separation between the bottom of the workpiece and the dynamometer, the signal transmission from the contact zone to the transducer is reduced, and so the AE does not satisfactorily indicate the amount of over-grinding. The strategy for monitoring the over-grinding by measuring the grinding force is satisfactorily verified in this study.     

A lower upper-bound solution for shear spinning of cones

The shear spinning process, where the plastic deformation zone is localized in a very small portion of the work piece, is introduced for the manufacturing of large conical shapes. This process seemingly shows a promise for increasingly broader application to the production of axially symmetric parts. This study is to gain a better understanding of the process of shear spinning and to propose a lower upper-bound solution for shear spinning cones. Velocity fields and strain rates are derived from considering the adequate deformation mode and the contact factor is introduced to obtain the lower upper-bound power. The theoretical values are compared with the experimental results of various materials. Al-1100-0, Al-1100-H14, and Al-6061-0. A comparison shows that theoretical prediction is reasonably in good agreement with experimental results.