摘要: |
At low temperatures, most materials become stiff or brittle or both, including metals, rubber and other elastomers, and many plastics. This problem is exacerbated, especially in equipment with diesel engines, because the engines run rougher and the increased vibration is only slightly damped by shock absorbers and vibration mounts that become stiff and ineffective in the cold. The increased stiffness of the softer elastomers such as those used in seals, tires and belts may cause leakage or other problems. In addition, volume changes with lowering temperatures may cause problems in assemblies with close tolerances, such as bearings. The objective of this digest is to provide a discussion of the general types of problems that will be encountered in automotive and construction equipment when used in the extreme cold and to provide guidelines for overcoming them. The properties and problems of metals are discussed first, followed by a discussion of plastics and elastomers. |