本试验的目的是确定零件在极端高温和低温条件下的耐暴露性，以及在这些极端条件下的交替暴露冲击性，例如设备或零件在北极地区的加热庇护所之间的转移。在低温区域或运输过程中不连续运行的设备也可能遇到这些情况。尽管试样最好在规定的暴露时间内达到热稳定性，但为了节省时间，可在规定的最小暴露时间内对零件进行测试，这将不会确保热稳定性，而只是一种接近热稳定性的方法。热冲击过程中产生的操作特性和物理损伤的永久性变化主要由尺寸和其他物理特性的变化引起。热冲击的影响包括饰面开裂和分层，嵌入和封装化合物开裂和开裂，热密封和外壳接缝打开，填充材料泄漏，密封件和真空玻璃到金属密封件破裂或开裂，以及由于导体或绝缘材料的机械位移或断裂而引起的电气特性变化。

This test is conducted for the purpose of determining the resistance of a part to exposures at extremes of high and low temperatures, and to the shock of alternate exposures to these extremes, such as would be experienced when equipment or parts are transferred to and from heated shelters in arctic areas. These conditions may also be encountered in equipment operated noncontinuously in low-temperature areas or during transportation. Although it is preferred that the specimen reach thermal stability during the exposure specified, in the interest of saving time, parts may be tested at the minimum exposure durations specified, which will not insure thermal stability but only an approach thereto. Permanent changes in operating characteristics and physical damage produced during thermal shock result principally from variations in dimensions and other physical properties. Effects of thermal shock include cracking and delamination of finishes, cracking and crazing of embedding and encapsulating compounds, opening of thermal seals and case seams, leakage of filling materials, rupturing, or cracking of hermetic seals and vacuum glass to metal seals, and changes in electrical characteristics due to mechanical displacement or rupture of conductors or of insulating materials.