Study On High Temperature Creep Fracture Mechanics Parameter Of Homogeneous Tension Specimen Based On Reference Stress Method

With the development of the equipments which are towards to high temperature, high pressure and large scale in the fields of oil industry, chemical industry, nuclear power industry, electrical power industry and any other industries, higher requirements are raised for the benefit and safe reliability of the equipment in the production process. In such fields, there are lots of high temperature and high pressure equipments, and the welded constructions are used in the equipments manufacturing process worked in bad situation. Though long time working, the crack broken of high temperature creep deformation is one of the main broken forms in welded constructions broken form, and it is the principal factor to harm the equipment worked securely for long time.People use idea of fracture mechanics to research creep crack, and some engineer parameters are proposed to represent and relate the rate of crack creep growth. From such research, high temperature creep fracture mechanics parameter C* is one of the most effective parameter to predict crack creep growth, and this parameter can reflect aging and durative of the material.The finite element method ('FEM'for short) is usually used to evaluate the value of high temperature creep fracture mechanics parameter C*, but it takes long time to get the value. Using reference stress method ('RSM'for short) to evaluate the value of the high temperature creep crack parameter is proposed by Central Electricity Generating Board ('CEGB'for short). This method can overcome the shortcomings of FEM, and it can evaluate the value of C* parameter efficiency.The process of evaluating C* parameter by RSM is evaluation for reference stress and stress intensity factor. Different samples have different stress intensity factors, and the calculated modes of stress intensity factors are introduced in some datum, so the key of calculating the value of C* parameter is solving the value of reference stress. The solution method of reference stress is introduced in a assessment procedure for the high temperature response of structures——Procedure R5 Issue. The key of this method is solving the value of limit load. High temperature creep crack parameter C* is calculated depending on the production of Procedure R5 Issue. Then, every tensile sample is analyzed and calculated by large finite element analysis software——ABAQUS which is used by finite element method. The result analyzed and calculated by FEM compared with the result by RSM to validate the feasibility of the result of high temperature creep crack parameter C* which used by RSM.The result of high temperature creep crack parameter C* which used by RSM as follows:The definition and solution method of limit load and stress intensity factor are imported in the evaluation of high temperature creep crack parameter C* which used by RSM.Using reference stress method and finite element method (using the finite element software ABAQUS) to analyze high temperature creep fracture mechanics parameter C* in Compact tension specimen ('CT specimen'for short), and the same way is used in C-shaped tensile specimen. The influence factor of high temperature creep crack parameterC* such as creep exponentn, creep coefficient A, crack size coefficient a/w and so on can be found, then the feasibility of the result of high temperature creep crack parameter C* which used by RSM can be validated in CT specimen.