Jian Ping Liu

Heating Current Control in Electric Hot Machining Based on Conservation Law of Optimum Cutting Temperature

In this paper, we investigate the relationship of heating current in Electric Hot Machining with tool life, cutting parameters and machined surface roughness. Experimental results indicate that there is an optimal heating current in EMH in which the effect of hot machining is the best. A method of rapid determining the optimal heating current under various cutting conditions in EHM is proposed according to the conservation law of optimum cutting temperature. That is, for a certain combination of tool and workpiece, the heating current relative to optimal cutting temperature in different conditions can be found by changing heating current and measuring cutting temperature to meet the control object of temperature in EHM. The PID control principle and effect of computer monitoring system for realizing optimal heating current control in EHM is also introduced.

Study on Pre-Stress Hard Cutting of Bearing Races

The analysis on load characteristics and stress state of bearing races shows that the roll path and outside layer of a bearing race are the main part to bear the load, and that residual tensile stress is often found on workpiece surface. For the purpose of improving residual stress state on machined surface of a bearing race, a method of pre-stress hard cutting is put forward. In this paper, the principle of pre-stress cutting is introduced, and method of loading stress on bearing races, together with the calculation for pre-stress, is analyzed. A set of device with expanding mandrel for realizing the process is designed too and an experiment of pre-stress cutting is carried out on a lathe with PCBN tool. The experimental results show that, by using this method, we can get residual compressive stress on machined surface layer of a bearing race and increase the quality and contact fatigue life of bearing.

Experimental Study on Pre-Stress Hard Cutting of Aero-Screw and its Machined Surface Residual Stress State

Pre-stress Hard Cutting, known as a new machining technology, is the combination of hard cutting and pre-stress cutting. Some reports show pre-stress machining can improve residual stress state of machined surface and prolong fatigue life of mechanical part, such as drive shaft, bearing and engine vane etc. Based on the principle of this technology, this paper take aero-screw shaft machining as object, investigated the pre-stress loading method, experimental device and implementation process of pre-stress hard cutting. Experiment is carried out for aero-screw shaft with PCBN tool, cutting force, machined surface residual stress state and distribution are measured. The experimental results show that by using this method, residual compressive stress is got on machined surface and good surface finish is gained, hence it can control machined surface residual stress state actively and improve the fatigue life of aero-screw shaft..

Study on Pre-Stress Cutting of Bearing Race and Its Machined Surface State

Theoretical analysis and experiments on bearing race show that a suitable residual compressive stress on roll path of bearing race can prolong its contact fatigue life. However, residual tensile stress is often found on workpiece surface of bearing race. To actively control the residual stress state and improve fatigue life of bearing part, a new method of pre-stress hard cutting is applied. In this paper, the principle of pre-stress hard cutting for bearing race is introduced as well as the experiments on it. In the experiments, residual stress, hardness and roughness of machined surface are measured and analyzed. Moreover, micro-topography and texture characteristics of machined surface are investigated and experimental results are compared with that by grinding. It is found that we can get residual compressive stress and fine quality on machined surface of bearing race by pre-stress hard cutting and increase its productivity as well.

Vibration Characteristic of Violin Bowstring and Experimental Research on Helmholtz Motion of String

The sound source of violin is string vibration. By the stick–slip friction action between bow and string of violin, string and bridge form a complicated vibration system. The interaction mechanism of bowstring is very intricacy. In this paper, through theoretical analysis and experiment, the vibration behavior of violin string is investigated. We measured the vibration images of bowing and plucking violin string on a high-speed photography optical platform and got two different character of string vibration, including vibration displacement, velocity and space trajectory of the mark point on string. By comparing the displacement curves of the different points among on string, the variety of the ratio of positive process time to negative one of vibration sawtooth waveform are studied, and also the formation process of string vibration enveloping curve. On this basis, the Helmholtz motion of string vibration which is presented at 1862 is studied.

Mechanical Analysis and Structural Optimization of the Parabolic Trough Solar Collector

Parabolic trough solar thermal power generation system is always restricted by high drive torque, low thermal efficiency and high investment cost. In this paper, the parabolic trough solar collector in a solar energy application base is taken as the research object and FEM was used to realizing its structural light-weighting design. The structural overall performance is improved to lay a foundation for innovating drive mode and expanding the rotation scope. Beginning of the paper, the wind load characteristic was analyzed and its computational formula was provided the magnitude of wind load was computed; then, the static performance of the solar collector was analyzed by using ANSYS Workbench and the worst working condition of each static characteristic was confirmed to service for the later structural optimization; last, the overall optimization scheme of the solar collector was put forward, the position of the reflectors supporting point and the structure of the solar collectors cantilever was optimized.

New Method of Pre-Stress Hard Cutting for Screw Shaft

The import mechanical components and burden part in aeronautic and automobile industry, such as screw shaft, aero-bearing and engine vane etc. are often found fatigue failure cased by their residual stress state on machined surface. Aiming at the problem, this paper presents a new green machining technology by integrating pre-stress cutting and hard machining method. The principle of pre-stress hard cutting of shaft part is introduced together with its implementary process in this paper. Pre-stress loading method on screw shaft is investigated and device for actualizing the process is designed. Experiment of pre-stress hard cutting is carried out for screw shaft with PCBN tool. The experimental results show that by using this method, residual compressive stress is got on machined surface and hence increase the quality and fatigue life of screw shaft.

View Loops Separation from Engineering Drawings Based on Multi-Granularity Information Acquisition

To improve the validity and efficiency of feature recognition for 3D reconstruction from engineering drawings, this paper presents a new method of view loops separation based on multi-granularity information acquisition. By analyzing the line-frames of combined primitive views and hidden semantics in engineering drawing, combined relationship of graphics primitives can be identified, then applies line-frames partition method of figuration analysis, view loop separation of individual primitive is realized by inertial loop search with pre-set priority. This algorithm is actualized in AutoCAD 2008 platform with development tools of Object ARX2008 and Visual C#2.0. With this algorithm, an application module of 3D intelligent reconstruction system is developed and finally the validity of this research is verified by examples.

New Method of Primitive Feature Recognition Based on Graphics Comparability

For improving validity and efficiency of 3D reconstruction from 2D engineering drawings, this paper presents a new method of primitive feature recognition based on graphics comparability determining of view loop. Main steps of this method are as follows: Firstly separate three views of single or combined primitive bodies by loop search, and then code view loops of primitive body and calculate graphics similarity measure of two view loops, further determine type of primitive body by projection rules and extract different information of modeling feature for different primitive bodies. Based on the mentioned above, different reconstruction algorithms are applied for different primitive bodies. Application module of 3D intelligent reconstruction system is developed together with the tools of Object ARX 2008 and Visual C# 2.0 in AutoCAD 2008 environment and this algorithm is actualized. The validity of feature recognition is verified by examples.

New Method of Feature Recognition from Engineering Drawings Based on Multi-granularity Information Acquisition

For improving the validity and efficiency of 3D reconstruction of engineering drawings, this paper presents a new method of feature recognition based on multi-granularity information acquisition. In this method, by analyzing the line-frames of combined primitive views and hidden semantics in engineering drawing, combined relationship of graphics primitives can be identified, then imitating line-frames partition method of figuration analysis, view loop separation of individual primitive is realized by inertial loop search with some priority. This algorithm is actualized in AutoCAD 2008 environment with development tools of Object ARX2008 and Visual C#2.0. With this algorithm, an application module of 3D intelligent reconstruction system is developed and finally the validity of this research is verified by examples.