An apparatus for constant stress creep testing in vacuum

Some experimental difficulties encountered when carrying out creep tests in vacuum are discussed. The principle and performance analysis of a simple device which circumvents these difficulties whilst maintaining approximately constant stress at the specimen is presented. The device maintains a stress accuracy such that the creep strain rate can be kept within +or-5% of the rate which could be observed under truly constant stress conditions for strains up to about 20% and creep exponents as high as 9.