Tool Wear in Longitudinal-Torsional Ultrasonic Vibration Assisted Drilling of CFRP/Ti Stacks and Its Influence on Drilling Quality

Chunhao Wang,Pengnan Li,Shujian Li,Xinyi Qiu,Changping Li,Qingquan Jiang,Qiulin Niu,Tae Jo Ko 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.1

Longitudinal-torsional ultrasonic vibration assisted drilling (LTUVD) has received extensive attention as a new machining technology in recent years. Especially for the stacks structure similar to carbon fiber reinforced polymer/titanium alloy material (CFRP/Ti6Al4V), it has more significant machining advantages. However, the effect mechanism of longitudinal-torsional ultrasonic vibration (LTUV) on tool wear, the tool wear condition in LTUVD machining and its influence on machining quality are not clear. In this work, the effect of LTUV on the tool wear of CFRP/Ti stacks was analyzed, and the tool wear of CFRP/Ti stacks and its effect on the entrance, interface and hole wall were investigated by drilling experiments under LTUVD condition. The analysis demonstrated that LTUVD can reduce tool wear by reducing the force and temperature during CFRP/Ti stacks drilling. The typical characteristics of LTUVD drill wear were the reduction of the flank face width, the adhesion of Ti to the tool, the blunting and the fracture of the cutting edge. The worn tool shows different wear characteristics in different parts. Spindle speed is one of the key factors that affect the wear rate of the typical parts, such as chisel edge, outer edge corner and main cutting edge. The mean damage factor of the entrance and interface of the 17–20 holes drilled by LTUVD were 11.5% and 8.7% higher than those of the 1–4 holes respectively. As the tool wear intensifies, the hole wall of CFRP produced more pits and the flatness decreased. The hole wall roughness increased by 30.9% when the 17–20 holes were drilled compared with the 1–4 holes.

Analysis of Influence Factors on AC Breakdown Characteristics of Rod-Barrier Gap and Electric Field Simulation

Hu Kai,Li Guochang,Gu Zhenlu,Zhang Fan,Wei Yanhui,Lei Qingquan 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

The insulation performance of air gap can be improved by inserting insulation barriers into the high voltage box with limited space. The influence of the barrier dimension, barrier thickness, barrier position and surface state of epoxy resin barrier on the AC breakdown characteristics of the “rod electrode-insulation barrier-ground electrode” system are discussed in the work. An equal-size model of the insulation system is established to analyze the influence of the insulation barrier on electric field and the discharge mechanism. The experimental results indicate that the breakdown voltage is improved significantly by enlarging the barrier dimension, up to twice as much. In contrast, the barrier thickness has little effect on the breakdown voltage because the discharge is mainly along the barrier surface. Besides, the breakdown voltage can be increased by reducing the distance between insulation barrier and rod electrode, this is because of the blocking effect of insulation barrier on the corona layer around the electrode, which can hinder the development of charges to the ground electrode, thus delaying the discharge process. The breakdown voltage increases with the barrier surface roughness because of the prolongation of discharge path and the distortion of local electric field. The breakdown voltage decreases with the rise of temperature, it decreases to 37.5 kV when temperature rose to 60 °C. Due to the increase of free charges mobility, the corresponding surface resistivity decreases from 16.2 × 1014 Ω at 20 °C to 3.14 × 1014 Ω at 60 °C. This work can provide support for the reasonable design of insulation barriers in engineering application.

Predictions of the summer monsoon climate by using the dynamic models

Zong-ci Zhao,Qingquan Li,Yong Luo,Xuejie Gao 한국기상학회 1997 한국기상학회 학술대회 논문집 Vol.1997 No.-

Warning Method for Ultimate Thermal Stress of Cable Terminal Based on Tailpipe Temperature Monitoring

He Dongxin,Zang Qingjing,Li Junda,Liu Hongshun,Xu Zhe,Li Qingquan 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.5

The thermal stress at the interface of different materials becomes distorted during the thermal expansion of a cable terminal, leading to cracking and insulation failure. To give a warning of the ultimate thermal stress of cable terminal, this paper presents a warning method for the ultimate thermal stress of the cable terminal based on tailpipe temperature monitoring. Taking a 110 kV gas-insulated switchgear cable terminal as an example, the heat transfer model of the cable terminal is established under the working condition of a through-flow. The relationship between the temperature of the tailpipe, maximum thermal stress of the epoxy casing, and current-carrying capacity of the cable is established based on a data fitting method, the ultimate stress of the epoxy is taken as a threshold value for the detection and calculate the corresponding current-carrying capacity of the cable and temperature of the tailpipe. The results show that the thermal stress concentration in the cable terminal exceeds the limit when the monitoring temperature at the exposed tailpipe reaches 54.25 °C. If the relationship between the external temperature of the cable terminal and maximum thermal stress is known, warning of the ultimate thermal stress of cable terminal by monitoring the temperature of the tailpipe, providing theoretical support for the regulation of the current-carrying capacity of the cable.

Spatial Data Internet Progressive Transmission Control based on the Geometric Shapes Similarity

Luliang Tang,Xia Zhang,Zihan Kan,Bisheng Yang,Qingquan Li 제어·로봇·시스템학회 2014 International Journal of Control, Automation, and Vol.12 No.5

It is very difficult to transmit spatial data over the Internet rapidly because of huge data volume and limited network bandwidth. How to transmit spatial data over the Internet is becoming a big problem. Based on the Distance View and the Characteristic Set View, this paper proposes a Spatial Data Similarity Model (SDSM) and a set of methods to measure the similarity of points, polylines and polygons, then this paper puts forward a spatial data progressive transmission method based on the SDSM, which is prior to transmit the spatial data that is most important for shape from server to clients. The experiments tested the progressive transmission control of the polylines and polygons data by the similarity at different resolutions, The results show that the SDSM is beneficial to progressive transmission of spatial data at different resolutions and is a promising solution to the progressive transmission of spatial data over internet.

Space Charge Accumulation Mechanism Near the Stress Cone of Cable Accessories Under Electrical-Thermal Aging

Dongxin He,Wenjie Gong,Tao Zhang,Wei Wang,Xiaoran Wang,Qingquan Li 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1

Due to the complicated structure composed of diff erent kinds of materials, space charges tend to accumulate within cable accessories, which easily leads to the electrical breakdown. To obtain insights into the space charge accumulation in cable accessories, accelerated aging was performed for 10 kV crosslinked polyethylene (XLPE) insulated cable samples with stress cones, under an AC voltage of 26.1 kV and temperatures of 103 °C and 114 °C. The space charge distribution in the cable insulation was tested at diff erent aging stages. The results show that space charge accumulates in the insulation covered by the stress cones, and the charge density and coaxial distribution region increase during aging. Together with the results for the charge measurement on peeled cable samples, it is concluded that charge accumulation is related to the semiconductor used in the stress cones. It is diffi cult for the space charge generated in the cable insulation to escape through the silicone rubber-based (SR-based) semiconductor in the stress cones, as the ability of this material to conduct charges is lower than that of a cable-shielding ethylene–vinyl acetate-based (EVA-based) semiconductor; therefore, the space charge accumulates near the outer part of the insulation. This research provides insights into the important function of semiconductor on charge accumulation in cable accessories, which will aid in research on optimizing and prolonging the lifetime of cable accessories.