ASTM E1457-15
金属蠕变裂纹扩展时间测量的标准试验方法

Standard Test Method for Measurement of Creep Crack Growth Times in Metals

被代替

标准号

ASTM E1457-15

发布

2015年

发布单位

美国材料与试验协会

替代标准

ASTM E1457-19

当前最新

ASTM E1457-23

 

 

适用范围

6.1 Creep crack growth rate expressed as a function of the steady state C* or K characterizes the resistance of a material to crack growth under conditions of extensive creep deformation or under brittle creep conditions. Background information on the rationale for employing the fracture mechanics approach in the analyses of creep crack growth data is given in (11, 13, 30-35).

6.2 Aggressive environments at high temperatures can significantly affect the creep crack growth behavior. Attention must be given to the proper selection and control of temperature and environment in research studies and in generation of design data.

6.2.1 Expressing CCI time, t_0.2 and CCG rate, da/dt as a function of an appropriate fracture mechanics related parameter generally provides results that are independent of specimen size and planar geometry for the same stress state at the crack tip for the range of geometries and sizes presented in this document (see Annex A1). Thus, the appropriate correlation will enable exchange and comparison of data obtained from a variety of specimen configurations and loading conditions. Moreover, this feature enables creep crack growth data to be utilized in the design and evaluation of engineering structures operated at elevated temperatures where creep deformation is a concern. The concept of similitude is assumed, implying that cracks of differing sizes subjected to the same nominal C*(t), C_t, or K will advance by equal increments of crack extension per unit time, provided the conditions for the validity for the specific crack growth rate relating parameter are met. See 11.7 for details.

6.2.2 The effects of crack tip constraint arising from variations in specimen size, geometry and material ductility can influence t_0.2 and da/dt. For example, crack growth rates at the same value of C*(t), C_t in creep-ductile materials generally increases with increasing thickness. It is therefore ne......

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