设计师多年来把材料强度作为设计的重要指标,希望制造的机械零件具有相近的强度,即提出了“等强度设计原则”以期得到理想的使用效果.实际表明:由于强度原因引起断裂的失效事故其几率比磨损和腐蚀造成的要少得多,只不过磨损和腐蚀大多是逐渐发生的“慢性病”,不如骤发性的断裂? Designers for many years the material strength as an important indicator of the design, the hope that the manufacture of mechanical parts with similar strength, that is, “the principle of equal strength design” in order to get the ideal use of the actual shows that: due to the strength of the failure caused by failure The odds are much less than those caused by wear and corrosion, except that wear and corrosion are mostly “chronic diseases” that develop more rapidly than sudden breaks.