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发表于 2017-5-9 21:41:05
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本帖最后由 lyklzy 于 2017-5-10 13:25 编辑
仔细阅读 ASME BPVC Section II,PartD 中的:
MANDATORY APPENDIX 1
BASIS FOR ESTABLISHING STRESS VALUES IN TABLES 1A AND 1B
(a) At temperatures below the range where creep and stress rupture strength govern the selection of stresses, the maximum allowable stress value is the lowest of the following: -------。
(b) At temperatures in the range where creep and stress rupture strength govern the selection of stresses, the maximum allowable stress value for all materials is established by the Committee not to exceed the lowest of the following:
-------。
就可以很容易地理解你画的红圈内的含意了。随时间变化的性能就是持久强度和蠕变率。
总之,许用应力是由材料在室温下的{抗拉强度,屈服强度},高温下的{(抗拉强度,屈服强度),持久强度(stress rupture strength 温度/应力/断裂时间),蠕变率(creep rate 温度/应力/变形率)}决定的。
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