Specimens of Delrin Acetal Resin with different stress-concentration factors were fatigue-tested in tension. Cyclic heat generation affects the strength of the part. Conventional stress-concentration factors may be used for Delrin, provided that the temperature is kept low enough, either through low loads or good heat transfer.
The conditions for the lateral stability at a highway or rail trailer are investigated analytically and experimentally with a laboratory size trailer. The motion of the trailer is expressed in two degrees of freedom, the lateral and angular displacements of the trailer. The oscillation was found to be a self-excited vibration which is very dependent upon the lateral springing at the towing pivot point. The variables are expressed as dimensionless parameters. For conventional trailer loading, the most important variables are the damping ratio as a function of the Strouhal number, sω/V, and as a function of a dimensionless energy term, μGz/V2. As higher values of sω/V and μGz/V2 are reached (for example, lower velocity), less damping is needed for stable operation. Although the relationships have not been established precisely, there is good correlation.
An analytical study of the effect of changing the design parameters of a two mass, six-degree-of-freedom suspension system was made. Rail cars with coil and air springs were analyzed by analog and digital computer. Spring stiffness, spring spacing, damping rates, height of center of gravity, and total mass were varied. The effect on frequency and response were determined.
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