A PROPOSED BIAXIAL-TENSILE DEVICE FOR FATIGUE TESTING

摘要

In this paper, the major experimental techniques used to generate biaxial cyclic stress conditions are briefly reviewed with an emphasis on the advantages and inconveniences associated with each technique. The available techniques are discussed within the framework of two broad categories, depending upon the biaxial stress ratio specification: (1) tests using two or more independent loading systems and (2) tests using a single loading system. Subsequently, a new apparatus is proposed in order to assess fatigue life under in-phase biaxial-tensile loading at elevated temperatures. It makes use of an annular disk-specimen and can be easily mounted onto a standard push-pull machine so that the uniaxial force is converted into radial forces extending the disk-specimen. The ratio between the two principal stresses (tangential and radial stresses) at the reduced section of the disk-specimen can thus be imposed; this ratio depends upon the specimen configuration and may be fixed to a value ranging from 0.5 to 0.9, by varying the inner diameter of the disk. The proposed apparatus may be regarded as a low cost alternative with respect to other available techniques used to simulate such particular loading conditions. The experimental fixture worked properly and preliminary data obtained to date is discussed in this paper.