The mechanical properties of guidewires
Stiffness is always one of two factors that determine frictional resistance. The other factor, the coefficient of friction, depends on the surface characteristics. Teflon coating reduces the sliding friction to one-half, and a hydrophilic plastic coat to about one-sixth compared with steel.
The mechanical properties of guidewires. Part I: Stiffness and torsional strength
The stiffness of guidewires varies in accordance with the fourth power of the core diameter. Titanium wires with the same core diameters have one-quarter the stiffness of steel wires. The torsional strength shows the same correlation with the 4th power of the diameter of the core in solid wires. With a few exceptions, spring wires do not have a usable torsional strength. The differences in the stiffness of the wire tips, and the different kinds of transition to the stiff shaft can be explained by differences in the construction of the wires and their tips.
Prediction of a representative point for rail temperature measurement by considering longitudinal deformation
Monitoring rail temperature is very important for determining the safe running speed of trains and to prevent buckling. In general, the maximum variation of the internal rail temperature can be >7 ℃ depending on the point of measurement. However, there is as yet no sufficient information about how to predict the measurement point to represent the thermal deformation due to temperature distribution. In this study, the authors report a new point, called the representative measurement point, at which the rail temperature can be measured. This point considers the average deformation of the rail through structural analysis by adopting experimental and actual rail temperature data. The authors designed and installed a measurement system similar to an actual rail environment. Using the system, various data were acquired (internal/surface rail temperature and weather data) for 10 months. On the basis of these data, an analysis was done to calculate the average deformation point through thermal analysis. Finally, the representative measurement point was proposed as the position at which the average deformation point converges regardless of weather or seasons. The authors believe that the method described herein is advantageous in that it could be used in a high-accuracy temperature-monitoring system and for predicting thermal deformation and buckling.