scholarly journals Evaluation of Multiaxial Creep-fatigue Strength for High Chromium Steel under Non-proportional Loading

2019 ◽  
Vol 300 ◽  
pp. 07002
Author(s):  
Yuuki Kasamuta ◽  
Fumio Ogawa ◽  
Takamoto Itoh ◽  
Hiroyasu Tanigawa
Keyword(s):  
Chromium Steel ◽  
Fatigue Tests ◽  
Proportional Loading ◽  
High Chromium ◽  
Nuclear Fusion Reactor ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Strain Paths ◽  
Multiaxial Creep ◽  
Failure Life

This study discusses the result of creep-fatigue tests of a high-chromium steel, F82H which was designed as blanket structural materials of nuclear fusion reactor, carried out at room temperature to 823K in air. Strain paths applied were a push-pull loading and a circle loading in which normal and shear strain have 90 degree phase difference. The holding times used were 180 s and 600 s. Moreover, an evaluation of failure life by taking into account intensities of creep and non-proportionality is discussed based on both the life evaluation proposed by Itoh, et al and method of modified universal slopes. Availability of the equation for the life evaluation was confirmed by comparison with conventional universal slope method.

Assessment of Failure Life Evaluation Methods for Structural Discontinuities with Fatigue and Creep-Fatigue Tests on Multi-Perforated Plate Made of Mod.9Cr-1Mo Steel

2021 ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Takano Masahito
Keyword(s):  
Fatigue Life ◽  
Perforated Plate ◽  
Estimation Method ◽  
Evaluation Methods ◽  
Fatigue Tests ◽  
Reduction Factor ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Number Of Cycles ◽  
Failure Life

Abstract This study compares and assesses the different fatgue and creep-fatigue life eveluation methods by performing tests of perforated plate made of Mod.9Cr-1Mo steel. Multi-perforated plate was subjected to mechanical cyclic loading at 550°C, and crack initiation and propagation on the surfaces of the holes were observed. A series of finite element analyses (FEA) were carried out to predict the number of cycles to failure by the several failure life evaluation methods, and these predictions were then compared with the test results. Several types of evaluation methods that use the elastic FEA were applied, namely the stress redistribution locus (SRL) method, simple elastic follow-up method. In addition to these, evaluation was also carried out using the results of inelastic FEA to compare these elastic FEA based estimation method. The comparisons indicate that, for all conditions tested, the SRL method provided a rational prediction of the fatigue and creep-fatigue life when ? = 1.6 was applied, where ? = 1.6 is the recommended reduction factor for this method in general use. A comparison of the SRL method and the results of the inelastic FEA indicated that the applicability of the value of factor ? in the SRL method depends on the elastic region remaining in the cross-section including the evaluated point and the spread in the plastically deformed region in the specimen.

scholarly journals Fatigue Testing and Evaluation of Fatigue Strength under Multiaxial Stress State; Why do we need fatigue testing?

2018 ◽  
Vol 159 ◽  
pp. 01050
Author(s):  
Takamoto Itoh ◽  
Fumio Ogawa ◽  
Takahiro Morishita
Keyword(s):  
Hollow Cylinder ◽  
Compression Test ◽  
Fatigue Testing ◽  
Biaxial Tension ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Proportional Loading ◽  
Loading Test ◽  
Inner Pressure ◽  
Failure Life

Types of multiaxial fatigue tests and their experimental results are presented in this paper. There are typical three types in multiaxial fatigue tests: the combining push-pull and reversed torsion loading test using hollow cylinder specimen, the biaxial tension-compression test using cruciform specimen and the inner pressure applied the push-pull loading test using the hollow cylinder specimen. In the combining a push-pull loading and a reversed torsion loading test, failure life under non-proportional loading in which principal directions of stress and strain were changed in a cycle was shortened compared to proportional loading in which those are fixed. Fatigue lives were well-correlated using a non-proportional strain range considering the effect of strain path and material dependence. In the biaxial tension-compression test, the failure life decreased with increase of the principal strain ratio. In the inner pressure applied the push-pull loading test, cyclic deformation behaviour due to complex loading paths of multiaxial fatigue tests with the inner pressure associated with push-pull and rev. torsion acted to reduce the failure lives. Experimental investigation of multiaxial failure life and elucidation of their governing mechanism is essential and it can broaden the applicability of structural components.

1118 Life Evaluation of 63Sn-37Pb Solder Under Multiaxial Creep-Fatigue

2001 ◽  
Vol 2001.76 (0) ◽  
pp. _11-35_-_11-36_ ◽  
Author(s):  
Takeshi SHIRATSUCHI ◽  
Masao SAKANE ◽  
Yutaka TSUKADA ◽  
Hideo NISHIMURA
Keyword(s):  
Life Evaluation ◽  
Creep Fatigue ◽  
Multiaxial Creep

Fatigue Failure Life of SS400 Steel under Non-Proportional Loading in High Cycle Region

2014 ◽  
Vol 891-892 ◽  
pp. 1385-1390
Author(s):  
Takahiro Morishita ◽  
Shu Li Liu ◽  
Takamoto Itoh ◽  
Masao Sakane ◽  
Hideyuki Kanayama ◽  
...  
Keyword(s):  
Low Carbon Steel ◽  
Stress Path ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Fatigue Properties ◽  
Low Carbon ◽  
Random Loading ◽  
Proportional Loading ◽  
Strain Stress ◽  
Failure Life

This study discusses fatigue properties of low carbon steel under multiaxial non-proportional loading and an evaluation of failure life. Multiaxial fatigue tests under non-proportional loading with various stress amplitudes were carried out using a hollow cylinder specimen in low and high cycle regions at room temperature. In the test, three types of strain/stress path were employed. They are a push-pull, a reversed torsion and a combined push-pull and reversed torsion loadings in which stress amplitudes used were constant and random. This study evaluates an effect of non-proportional loading on fatigue life in the high cycle fatigue region to discuss the applicability of ΔεNP proposed by Itoh et al. on life evaluations in the high cycle region and under random loading.

Study on Creep-Fatigue Damage Evaluation for Boiler Weldment Parts

2000 ◽  
Vol 123 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Takashi Ogata ◽  
Masatsugu Yaguchi
Keyword(s):  
Weld Joint ◽  
Creep Damage ◽  
Fem Analysis ◽  
Fatigue Tests ◽  
Type Iv ◽  
Fine Grain ◽  
Creep Fatigue ◽  
Damage Accumulation Model ◽  
Type Iv Cracking ◽  
Failure Life

Creep-fatigue tests on the heat-affected zone(HAZ) simulated materials, base metal, weld metal and weld joint of 2.25Cr-1Mo steel, and elastic-plastic and creep FEM analysis for the weld joint were conducted. It was found from the comparison between experimental evidences and the analytical results that “Type IV” cracking was caused by two major reasons. One is accumulation of creep strain during strain hold in the fine-grain region is larger than that in other regions, suggesting progress of creep damage in the fine-grain region prior to other regions. The other is existence of triaxial tensile stress field within the fine-grain region caused reduction of failure ductility. Crack initiation portion and failure life under the creep-fatigue test could be well predicted by the nonlinear damage accumulation model based on the FEM analysis results.

scholarly journals Fatigue Property of Additively Manufactured Ti-6Al-4V under Non-proportional Multiaxial Loading

2021 ◽  
Author(s):  
Yuya Kimura ◽  
Fumio Ogawa ◽  
Takamoto Itoh
Keyword(s):  
Fatigue Strength ◽  
Crack Propagation ◽  
Strain Path ◽  
Low Cycle Fatigue ◽  
Fatigue Property ◽  
Strength Properties ◽  
Fatigue Tests ◽  
Multiaxial Loading ◽  
Proportional Loading ◽  
Strain Paths

Abstract Low cycle fatigue strength properties of additively manufactured Ti-6Al-4V alloy were experimentally investigated under proportional and non-proportional multiaxial loading. Fatigue tests have been conducted by means of hollow cylinder specimens with and without heat treatments, at room temperature in air. Fatigue tests with proportional loading represented by a push-pull strain path and non-proportional loading represented by a circle strain path were conducted, respectively. The fatigue lives of additively manufactured specimens were drastically reduced obviously by internal voids and defects in comparison with the specimens used in the previous study [1]. In addition, the defect size is measured, and the defect does not cause fatigue strength reduction above some size. The fracture surface was observed using SEM to investigate fracture mechanism of additively manufactured specimens under two types of strain path. Different fracture patterns are recognized for the two strain paths; however, both showed the retention of the crack propagation in spite of the presence of numerous defects. The crack propagation properties of the materials with numerous defects under non-proportional multiaxial loading were elucidated to increase the reliability of additive manufactured components.

Comparison of Creep-Fatigue Evaluation Methods With Notched Specimens Made of Mod.9Cr-1Mo Steel

2011 ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Takanori Karato ◽  
Sota Watanabe ◽  
Osamu Inoue ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fast Reactor ◽  
Evaluation Methods ◽  
Fatigue Tests ◽  
Test Results ◽  
Notched Specimens ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fatigue Life Evaluation

In a component design at elevated temperature, creep-fatigue is one of the most important failure modes, and assessment of creep-fatigue life in structural discontinuity is important issue to evaluate structural integrity of the components. Therefore a lot of creep-fatigue life evaluation methods were proposed until now. To compare and assess these evaluation methods, a series of creep-fatigue tests was carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo steel, which it is a candidate material for a primary and secondary heat transport system components of JSFR (Japan Sodium-cooled Fast Reactor). Mechanical creep-fatigue tests and thermal creep-fatigue tests were performed by using conventional uni-axial push-pull fatigue test machine and thermal gradient generating system with an induction heating coil. Stress concentration levels were adjusted by varying the diameters of notch roots in the both tests. In the test, creep-fatigue lives, crack initiation and propagation processes were observed by digital micro-scope and replica method. Besides those, a series of elastic Finite Element Analysis (FEA) were carried out to predict the number of cycles to failure by several creep-fatigue life evaluation methods. Then these predictions were compared with test results. Several types of evaluation methods which are stress redistribution locus (SRL) method, simple elastic follow-up method and the methods described in JSME FR (Fast Reactor) code were applied. The applicability and conservativeness of these methods were discussed. It was appeared that SRL method gave rational prediction of creep-fatigue life with conservativeness when the factor of κ = 1.6 was applied for all the conditions tested in this study. Comparison of SRL method and simple elastic follow-up method indicated that SRL method applied factor of κ = 1.6 gave the smallest creep-fatigue life in practicable stress level. JSME FR code gave an evaluation 70∼100 times conservative lives comparing with the test results.

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