The Method To Obtain Creep Parameters By Single Curve Of Small Punch Creep Test

Many equipments and components worked under high-temperature in power, petrochemical industry. The creep properties of these equipments and components needs to be assessed. When assess those pressure vessels in-service, the traditional uniaxial creep experiments sampling method has great impact defective equipment overall structural integrity. The traditional method for creep performance testing for in-service equipments, need larger volume from the equipments and components, which will affect the economic efficiency of enterprises at a certain extent. In order to have no affect on the normal production and business activities, testing creep properties of equipment and components in-service has more concerned in current study. In order to assess the equipments and components in-service, many researchers have proposed a variety of micro-sample creep experimental methods, such as indentation creep test, small punch creep test, small creep experiments and other micro-micro creep tests.Base on the advantages of small punch creep test has the ability to assess the creep properties of the equipments in-service, this paper implement further study on the small punch creep test. First of all, carried out on conventional mechanical analysis to CrMo steel which used in the plants with high temperature, then, base on the date of the conventional mechanical properties, implemented further study on the device of small punch creep test and the method to obtain the creep properties of small punch creep test. The main achievements of this thesis and research results are as follows:1) Through the research of small punch creep test device analysis by researchers of domestic and foreign, this thesis developed a new type device of small punch creep test. Compared with the existing small punch creep test device, the device possesses advantages of convenient operation, small occupation area, accurate data, simple structure etc.. Repeated and reliability experiments had carried out by the small punch creep test device, results show that, the small punch creep experiment device could meet the needs of small punch creep experiment. The successful development of the small punch creep device had provided facility of equipment for analyzing data of small punch in this thesis.2) This thesis proposed a new method to obtain creep properties of small punch creep test, that is use only one curve of small punch creep test together with finite element analysis to obtain creep properties of small punch creep test. The method is convenient and effective, long time of small punch creep test could be eliminated. Different loads of small punch creep tests had carried out to verify the reliability of the proposed method, the method has certain advantage in obtaining creep property parameters of small punch creep test. By this proposed method, creep properties could be obtained by only one curve of small punch creep test, without transformation by experience correlation.3) Under the premise of above method to obtain creep property parameters, further study on the relationship of load and equivalent stress. Through the analysis of small punch creep experiment and the corresponding data processing simulation, the relationship of load and equivalent stress could be obtained by only one curve of small punch creep test together with the finite element. The relationship is similar with the small punch test method for metallic materials which drafted by European standardization committee. Results of analyze show that, the method could obtain relationship of load and equivalent stress more convenient and directly, at the same time, the method could avoid the transformation of load and equivalent with experience relationship. The proposed method could save experimental time and avoid the errors of transformation.4) Life of small punch creep had been analyzed, based on the research of reverse method and relationship between load and stress, a novel method for obtaining life of small punch creep test had been put forward. The results were verified by the Dorn and Monkman-Grant equation, which was usually used for analyzing creep life of smll punch creep test. The verified results show that, the novel method was proposed is simple and effective, and has certain rationality, the most important is, the proposed method could obtain creep life for engineering application rapidly and accurately.