Effect Of Surface Roughness On Creep Test Of Small Cantilever Beam Specimens

The traditional standardized uniaxial tensile specimens creep test is a mature method for testing creep properties of materials.However,sampling large-sized standard specimens will lead to the failure of equipment and it is even impossible to sample from special narrow structures such as welds.For creep testing of in-service equipment and special structures,many new methods using small specimens have been developed.However,the sensitivity of small specimens to various influencing factors,such as size,surface state and atmosphere environment,increases due to the specimen size scaling down.Based on the K-R creep constitutive model,this paper analyses the theoretical basis of the correlation between the creep test results of small cantilever beam bending specimens and the traditional uniaxial tensile creep test.According to the creep test of small cantilever beam bending specimens,different surface treatment methods are adopted to realize the processing of different surface roughness specimens.Through the design of special sample fixture and the construction of test platform,under a series of loads,creep tests were carried out to study the effect of surface roughness on the creep test process of specimens.It is found that the creep deformation curves obtained from creep tests of small cantilever beam bending specimens include the first and second stages of creep,but it is difficult to get the third stage.The influence of surface roughness on creep process is obvious,and it is related to the magnitude of load.Under the same load,the larger the surface roughness,the smaller the creep deformation and the smaller the minimum steady-state creep rate.With the increase of test load,the influence of surface roughness on creep deformation of specimens increases.The creep deformation difference of specimens with different surface roughness can reach 0.3-0.4 mm.The creep parameters obtained from the inversion of the test results of different specimens are close to the theoretical values and have little difference.