An ad-hoc fretting wear tribotester design for thin steel wires

Steel wire ropes experience fretting wear damage when the rope runs over a sheave promoting an oscillatory motion between the wires. Consequently, wear scars appear between the contacting wires leading to an increase of the stress field and the following rupture of the wires due to fatigue. That is why the understanding and prediction of the fretting wear phenomena of thin wires is fundamental in order to improve the performance of steel wire ropes. The present research deals with the design of an ad-hoc fretting wear test machine for thin wires. The test apparatus is designed for testing thin wires with a maximum diameter of 1.0 mm, at slip amplitudes ranging from 5 to 300 μm, crossing angle between 0-90°, and contacting force ranging from 0,5 to 5 N. The working principle of displacement amplitude and contacting force as well as the crossing angle between the wires are described. Preliminary studies for understanding the fretting wear characteristics are presented, analysing 0.45 mm diameter cold-drawn eutectoid carbon steel (0.8% C) wires (tensile strength higher than 3000 MPa).

Analysis and Comparison of Experimental Results Both of Wind Tunnel Test and Running Test for HEMU-400X Pantograph

In this paper, experimental results both of wind tunnel test and running test for HEMU-400X pantograph were compared and were analyzed. In wind tunnel test, 1/4scale pantograph for HEMU-400X which is being developed for the maximum speed of 400km/h in Korea were tested to investigate the vertical lift force of pantograph at the operational speed of 250, 270, 300, 330, 360 and 400km/h using lift estimation from 1/4 scaled model results. In the running test of train, the contacting force of pantograph was measured to current operational speed of 300km/h. Finally, the results of vertical lift force of pantograph in wind tunnel test and contacting force for the running test were compared to analyze the aerodynamic characteristics of the pantograph for HEMU-400X.

Development and Evaluation of a Contacting Force Measurement System in a High Temperature and Pressure Water Condition for Fretting Wear Experiments

New system (load cell) for measuring a contacting force in a high temperature and pressure water condition (i.e. 320, 15 MPa) has been developed. The primary purpose is to apply it to the experiments of a nuclear fuel fretting wear, which occurs on the contacts between the fuel rods and the spacer grid spring/dimples due to a flow-induced vibration of the rods. A bi-axial load cell of a cylindrical shape is specially designed. Strain gages for a special use in a high temperature condition were attached on to the sensitive region of it to accommodate the bi-axial loading condition in fretting. The full scale of this load cell is ±50 N in axial force and ±50 N in bending force, respectively. In order to increase the sensitivity and to compensate for an ambient temperature effect, the load cell consists of two Wheatstone full bridge arrangements. The calibration results of the load cell show that the coupling effects of each force were almost negligible. This paper mainly presents the experimental techniques used during the development of the new load cell system. The techniques are characterized by a design optimization of a jig of a cylindrical type, the application of a metallic sealant for a waterproofing, a free welding fabrication process and a temperature compensation circuit. Details on the development procedure, calibration method and application results are also given in this paper.