Katsuya Setoguchi

Simplified creep analysis of perforated plates under steady creep condition

Abstract A study is performed on the creep analysis of perforated plates based on the equivalent solid plate concept. A series of creep analyses by FEM for various materials, ligament efficiencies and loading conditions is performed on a perforated plate with a triangular penetration pattern of circular holes. Based on the results of the analysis, prediction methods for both the equivalent solid plate property and the stress-strain concentration around the hole are proposed. The prediction method for the equivalent solid plate property is compatible with the elastic property shown in the ASME B&PV Code Sec. III A-8000. The prediction method for the stress—strain concentration is based on Neubers rule together with Hoffs analogy, and is compatible with the elastic peak stress multiplier in the ASME B&PV Code Sec. III A-8000.

Prediction of Macroscopic and Local Creep Behavior of Perforated Plates

Prediction methods of both macroscopic and local creep behavior of perforated plates in a general case involving both primary and secondary creep are proposed in this paper. Predicted results are compared with both experimental results and numerical ones by FEM. Macroscopic creep behavior is predictable by use of the effective stress of perforated plates which is concretely defined by the predictive equation. As for stress-strain concentration around a hole, predictive equations which are basically based on Neuber’s rule and which consider the effect of exponent of stress in creep equation give good results.

Comparison of creep-fatigue Life prediction by Life Fraction Rule and Strainrange Partitioning methods

A comparison of two kinds of creep-fatigue life prediction methods, Life Fraction Rule and Strainrange Partitioning, was performed for the cases of creep-fatigue tests under uniaxial strain-controlled conditions at 500 to600°C in air, using a normalized and tempered 2 1/4 Cr-1Mo steel. The main focus was on the influence of stress-strain behavior on life prediction. Two kinds of stress-strain values (i.e., experimental values and calculated values by inelastic analysis) were used for the life prediction of creep-fatigue tests. The results show that life prediction by the Life Fraction Rule was very sensitive to the stress-strain values, indicating a large discrepancy between predicted and observed lives in some cases, and that life prediction by the Strainrange Partitioning method was not so sensitive to the stress-strain values, indicating a good agreement between predicted and observed lives in all cases.

Prediction of Fatigue Life of Rolled Bolt-Nut Joints under Three-Step Loading and Three-Level Multi-Step Loading

Based on the previously proposed damage rule and life prediction method for rolled bolt-nut joints under two-step loading, life prediction method for three-step loading and three-level multi-step loading was investigated. The effect of load histories and change of material properties with damage accumulation was taken into account in the prediction method. Required material properties were obtained from fatigue tests under constant stress amplitude and two-step loading. In order to investigate applicability of the life prediction method, axial load controlled fatigue tests of rolled bolt-nut joints were carried out. Experiments indicated that the predicted results were in good agreement with the experimental results.