After a careful study of the article by Hull and Rimmer, we found that there existed some contradictions between the facts and theory put forward. Basing on the experimental data from related references and those obtained in our own laboratory, and retaining the rational basis of the above mentioned work, we suggest a new mechanism of creep rupture and derive a formula for the rupture time. The theoretical values agree fairly well with those measured. From these results, it seems that our treatment has improved some what the theory of Hull and Rimmer.