第1部分:18个具有九种不同几何形状且由两种不同钢材制成的压力容器封头承受单调增加的外部压力，直到发生坍塌。作为压力的函数，记录牙冠的偏转和牙冠凹侧最高度应变区域的应变。所有头部都经历了永久性变形。观察到四种失效模式:（i）牙冠的对称屈曲，（ii）关节和过渡区的不对称屈曲，（iii）圆柱壁的不对称屈曲，以及（iv）无屈曲的渐进变形。 这些试验结果与Slember和Washington提出的公式、ASME规范以及“第一屈服”标准的预测进行了比较。开发了四个新公式，并与试验结果和Bart的选定数据进行了比较。 建议使用一个公式作为ASME规范预测的改进，以及使用第一屈服标准。 建议进一步努力确定压力容器封头在外部压力下坍塌的更严格理论基础。第2部分:本文所考虑的概念提出，在给定荷载下，结构的蠕变行为可能与单轴蠕变试验的结果有关，单轴蠕变试验的结果称为该荷载下结构的参考应力。在这篇综述中，我们讨论了该方法的发展和蠕变结构在稳定和可变载荷、应力松弛、蠕变断裂和蠕变屈曲下参考应力的确定。通过与简单结构和复杂结构的实验结果的比较，表明了该方法的准确性。对今后的工作提出了建议，并对该方法在高温设计分析中的适用性进行了评估。

Part 1:Eighteen pressure vessel heads having nine different geometries and made from two different steels have been subjected to monotonically increasing external pressure until collapse occurred. Deflection of the crown and strains in the most highly strained regions of the concave side of the heads were recorded as functions of pressure. All heads underwent permanent deformations. Four modes of failure were observed: (i) symmetrical buckling of the crown, (ii) asymmetrical buckling in the knuckle and transition region, (iii) asymmetrical buckling of the cylindrical wall, and (iv) progressive deformation without buckling. These test results were compared with predictions by formulas proposed by Slember and Washington, the ASME Code, and by the "first yield" criteria. Four new formulas were developed and compared with the test results and selected data from Bart. One formula was recommended as an improvement to the ASME Code predictions as was the use of the first yield criteria. It was recommended that further effort be made to determine a more rigorous theoretical basis for the collapse of pressure vessel closure heads under external pressure.Part 2:The concept that is considered here proposes that the creep behavior of a structure under a given loading can be related to the results of a single uniaxial creep test at what is called the reference stress of the structure for that loading. In this review we discuss the evolution of the method and the determination of reference stresses for creeping structures under steady and variable loadings, stress relaxation, creep rupture and creep buckling. The accuracy of the method is shown by means of comparisons to experimental results for both simple and complicated structures. Recommendations for future effort are given and an assessment of the applicability of the method to elevated temperature design analysis is discussed.