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.

Crack mode and life of Ti-6Al-4V under multiaxial low cycle fatigue

2015 ◽  
Author(s):  
Takamoto Itoh ◽  
Masao Sakane ◽  
Takahiro Morishita ◽  
Hiroshi Nakamura ◽  
Masahiro Takanashi
Keyword(s):  
Hollow Cylinder ◽  
Stress Ratio ◽  
Biaxial Loading ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Testing Machine ◽  
Multiaxial Fatigue ◽  
Cycle Fatigue ◽  
Loading Test ◽  
Failure Life

This paper studies multiaxial low cycle fatigue crack mode and failure life of Ti-6Al-4V. Stress controlled fatigue tests were carried out using a hollow cylinder specimen under multiaxial loadings of ?=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. ? is a principal stress ratio and is defined as ?=sigmaII/sigmaI, where sigmaI and sigmaII are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at ?=0 is a uniaxial loading test and that at ?=1 an equi-biaxial loading test. A testing machine employed is a newly developed multiaxial fatigue testing machine which can apply push-pull and reversed torsion loadings with inner pressure onto the hollow cylinder specimen. Based on the obtained results, this study discusses evaluation of the biaxial low cycle fatigue life and crack mode. Failure life is reduced with increasing ? induced by cyclic ratcheting. The crack mode is affected by the surface condition of cut-machining and the failure life depends on the crack mode in the multiaxial loading largely.

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.

scholarly journals Bending and Torsion Fatigue-Testing Machine Developed for Multiaxial Non-Proportional Loading

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1115 ◽  
Author(s):  
Fumio Ogawa ◽  
Yusuke Shimizu ◽  
Stefano Bressan ◽  
Takahiro Morishita ◽  
Takamoto Itoh
Keyword(s):  
Fatigue Life ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
304 Stainless Steel ◽  
Testing Time ◽  
Loading Conditions ◽  
Proportional Loading ◽  
Bending Loading

A new fatigue-testing machine was developed to perform high-cycle multiaxial fatigue tests at 50 Hz, in order to reduce testing time. The developed machine can combine bending and torsion loading and perform fatigue tests at a high frequency, under proportional and non-proportional loading conditions, where the principal stress direction changes during a cycle. The proportional loading is cyclic bending loading, and the non-proportional loading is cyclic, combining bending and reversed torsion loading. In this study, the effectiveness of the testing machine was verified by conducting tests under these loading conditions, using specimens of type 490A hot-rolled steel and type 304 stainless steel. The fatigue life linked to bending loading obtained using the new testing machine was slightly extended compared with that obtained using the conventional fatigue-testing machine. The fatigue life derived as a result of a combination of bending and torsion was comparable to that obtained using the conventional fatigue-testing machine, although a fatigue limit reduction of 100 MPa was observed compared to the former study. The feasibility of tests using the developed multiaxial fatigue-testing machine was confirmed.

scholarly journals Multiaxial fatigue study on steel transversal attachments under constant amplitude proportional and non-proportional loadings

2018 ◽  
Vol 165 ◽  
pp. 16007
Author(s):  
Martin Garcia ◽  
Claudio A. Pereira Baptista ◽  
Alain Nussbaumer
Keyword(s):  
Fatigue Life ◽  
High Strength ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Life Assessment ◽  
Experimental Program ◽  
Proportional Loading ◽  
Load Carrying ◽  
Stress States ◽  
Experimental Values

In this study, the multiaxial fatigue strength of full-scale transversal attachment is assessed and compared to original experimental results and others found in the literature. Mild strength S235JR steel is used and an exploratory investigation on the use of high strength S690QL steel and the effect of non-proportional loading is presented. The study focuses on non-load carrying fillet welds as commonly used in bridge design and more generally between main girders and struts. The experimental program includes 33 uniaxial and multiaxial fatigue tests and was partially carried out on a new multiaxial setup that allows proportional and non-proportional tests in a typical welded detail. The fatigue life is then compared with estimations obtained from local approaches with the help of 3D finite element models. The multiaxial fatigue life assessment with some of the well-known local approaches is shown to be suited to the analysis under multiaxial stress states. The accuracy of each models and approaches is compared to the experimental values considering all the previously cited parameters.

Multiaxial Fatigue Failure Criterion Considering Formation and Growth of Small Cracks

2010 ◽  
Author(s):  
Yukio Takahashi
Keyword(s):  
Life Prediction ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Fatigue Life Prediction ◽  
New Approach ◽  
Small Cracks ◽  
Failure Life ◽  
Parameter Approach ◽  
Realistic Prediction ◽  
Two Parameter

Treatment of stress multiaxiality in fatigue assessment is practically important in many components subjected to cyclic loading during their operation. Based on the results of fatigue tests on hollow and solid bar specimens of SUS316NG and SGV410 under various combinations of axial and torsional stresses, accuracy of fatigue life prediction based on the conventional parameters as well as a two parameter approach newly proposed here was studied. The conventional parameters tended to provide conservative prediction of the failure life for shear-dominated cases especially for SUS316NG while the new approach was able to give more realistic prediction of failure lives.

Development of Bending and Torsion Fatigue Testing Machine for Multiaxial Non-Proportional Loading

2016 ◽  
Vol 853 ◽  
pp. 534-538
Author(s):  
Takahiro Morishita ◽  
Takamoto Itoh ◽  
Masao Sakane
Keyword(s):  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Tests ◽  
304 Stainless Steel ◽  
Loading Conditions ◽  
Proportional Loading ◽  
Cyclic Bending ◽  
Principal Directions ◽  
Type 304 ◽  
Bending Loading

This study presents a newly developed multiaxial high cycle fatigue testing machine which can load a cyclic bending loading and a reversed torsion loading onto an hour-glass shaped solid bar specimen. This testing machine can perform the fatigue tests with a high frequency under a proportional and a non-proportional loading conditions. In the non-proportional loading, principal directions of stress and strain are changed in a cycle. In the testing machine, the loading is generated by centrifugal force caused by the revolving weights attached to rotational wheels. The maximum frequency of the testing machine is 50Hz. A material tested was a type 304 stainless steel. In the test, two types of loading paths are employed, a proportional loading and a non-proportional loading. The former is a cyclic bending loading and the latter a combining cyclic bending and reversed torsion loading in the developed testing machine. In this study, an applicability of the testing machine is evaluated by carrying out the tests under these loading conditions.

Reprint of “Multiaxial fatigue property of Ti–6Al–4V using hollow cylinder specimen under push-pull and cyclic inner pressure loading”

2016 ◽  
Vol 92 ◽  
pp. 395-405
Author(s):  
Takahiro Morishita ◽  
Takamoto Itoh ◽  
Masao Sakane ◽  
Hiroshi Nakamura ◽  
Masahiro Takanashi
Keyword(s):  
Hollow Cylinder ◽  
Fatigue Property ◽  
Multiaxial Fatigue ◽  
Pressure Loading ◽  
Inner Pressure

Fatigue Life Properties of Stainless Steels in Wide Ranged Biaxial Stress State

2019 ◽  
Vol 795 ◽  
pp. 60-65
Author(s):  
Shunsuke Saito ◽  
Fumio Ogawa ◽  
Takamoto Itoh
Keyword(s):  
Fatigue Life ◽  
Stress State ◽  
Stainless Steels ◽  
Equivalent Stress ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Biaxial Stress ◽  
Loading Path ◽  
Inner Pressure ◽  
Biaxial Stress State

Multiaxial fatigue tests consisting of push-pull loading and cyclic inner pressure were carried out using hollow cylinder specimens of type 430 stainless and type 316 stainless steels at room temperature. 7 types of cyclic loading paths were employed by combining axial and hoop stresses: a Pull, an Inner-pressure, a Push-pull, an Equi-biaxial, a Square-shape, a LT-shape and a LC-shape. Fatigue lives vary depending on the loading path when those were evaluated by the maximum Mises’ equivalent stress on inner surface of the specimen. The fatigue lives of both the steels showed a similar tendency although some Pull tests take longer fatigue life when cracks initiated from inside surface of the specimen. This study investigated the crack initiation and propagation behaviors as well as the initiation of oil leakage to prove the behavior and discusses life evaluation for two steels under wide ranged biaxial stress state, too.

Considerations on the Necessity of Determining Principal Stresses and Directions for Analysis of Material Durability under Multiaxial Fatigue

2014 ◽  
Vol 601 ◽  
pp. 17-20 ◽  
Author(s):  
Ion Dumitru ◽  
Lorand Kun ◽  
Marcela Sava ◽  
Mihai Hluscu
Keyword(s):  
Principal Stress ◽  
Fatigue Testing ◽  
Principal Direction ◽  
Load Cycle ◽  
Multiaxial Fatigue ◽  
Principal Plane ◽  
Principal Stresses ◽  
Proportional Loading ◽  
Material Durability ◽  
Original Experimental Data

A special situation arises when multiaxial fatigue loadings are present, given not only the time-dependency of extreme principal stress values, but also the fact that principal plane positions change during one load cycle (non-proportional loading). Thus, the analysis of principal stress and principal direction variation becomes a very important step, necessary to be carried out before starting any multiaxial fatigue testing. Based on the above, the authors present a generalized method for computing principal stresses and determining principal plane positions, applicable for cyclic tension-torsion loadings with zero mean stresses but with different phase shifts and amplitude ratios. Based on original experimental data and data collected from the literature, the authors point out in the final part of the paper that the maximum principal shear stress can be considered as the main parameter for plotting Wöhler curves.

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