The low-cycle fracture strength of austenitic steel

Conclusions

• 1. Preliminary plastic deformation, which is accompanied by an increase of the static mechanical characteristics, leads to a substantial increase of the low-cycle fracture strength of steel 60Kh3G8N8V subjected to sign-constant repeated stress.

  Under conditions of constant stress preliminary deformation increases the fracture strength 35% and under cyclic loading ∼45% (at N=10⁴).

  With stress concentrators the strength is increased ∼70%.

  Surface strengthening by cold working of austenitic steel 60Kh3G8N8V reduces the danger of loweycle fracture for machine parts with stress concentrators.

• 2. The effectiveness of strengthening and the selection of the optimal cold working parameters must be analyzed in connection with the size of the load and the number of loading cycles.

  For highly loaded structures it is advisable to use parts subjected to a limited degree of cold working. Strengthening with high degrees of deformation may impair the operating characteristics despite the inerease of the static mechanical properties.

• 3. Comparison of the results for cold worked plastic steel 60Kh3G8N8V and high-strength steel 5KhNV with a high yield strength shows that, other conditions being equal, the material with the higher plasticity has the better resistance to repeated static loading, particularly in zones with nonuniform stresses, and has less tendency to sudden fracture.

Valid estimates of the operating capacity of a structure must take into consideration the strength characteristics of the material under conditions reflecting the particular operating conditions.