scholarly journals Multiaxial fatigue strength under non-proportional loading of additively manufactured notched components of Ti-6Al-4V

2019 ◽  
Vol 300 ◽  
pp. 03005 ◽  
Author(s):  
Stefano Bressan ◽  
Javad Razavi ◽  
Fumio Ogawa ◽  
Takamoto Itoh ◽  
Filippo Berto
Keyword(s):  
Heat Treatment ◽  
Strain Path ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Plastic Behavior ◽  
Proportional Loading ◽  
Material Microstructure ◽  
Powder Bed ◽  
Layer Orientation ◽  
Number Of Cycles

In this study fatigue tests have been conducted on additively manufactured notched specimens made of titanium alloy Ti-6Al-4V under uniaxial loading and multiaxial non-proportional loading. Laser powder bed fusion technique has been employed to fabricate cylindrical specimens which have been successively machined to obtain a circumferential notch. Four varieties of specimens were fabricated depending on the build orientation and the application of a post-fabrication stress-relief heat treatment. The influence of layer orientation and heat treatment on the material microstructure has been analyzed. Strain controlled tests were performed with both proportional loading represented by a push-pull strain path and non-proportional loading represented by a circle strain path. The number of cycles to failure under both proportional and non-proportional loadings seemed not depending on layer orientation and heat-treatment. The cyclic plastic behavior of the material has been verified through the observation of the softening and hardening curves. The surface of the crack has been finally analyzed to verify the crack initiation position which has been detected on voids or defects located in the vicinity of the notch tip.

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.

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 Initiation Under Low-Cycle Multiaxial Fatigue in Type 316L Stainless Steel

1983 ◽  
Vol 105 (2) ◽  
pp. 138-143 ◽  
Author(s):  
B. Jacquelin ◽  
F. Hourlier ◽  
A. Pineau
Keyword(s):  
Stainless Steel ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Stage I ◽  
Type B ◽  
Strain Behavior ◽  
Number Of Cycles

Low-cycle fatigue tests corresponding to fatigue life range between 103 and 105 cycles were carried out at room temperature on one heat of 316 L austenitic stainless steel. These tests included: (i) reversed tension-compression, (ii) reversed tension-compression with a superimposed steady torque, (iii) pulsated tension-compression with a stress ratio (Rσ) such that −0.5<Rσ<0, (iv) reversed and pulsated tension-compression with a superimposed steady internal pressure. In tests (ii), the torsional ratcheting effect was measured. SEM observations were used to determine the number of cycles corresponding to Stage I crack initiation and the orientation of Stage I microcracks. It was observed that the in-depth growing Type B shear microcracks were most damaging. A simple criterion is proposed Ni=No(Δγp B)α•(σnB)β where Ni is the number of cycles to crack initiation, Δγp B is the range of plastic shear strain on Type B planes, σnB is the maximum normal stress acting on these planes, No,α and β are parameters adjusted from the Manson-Coffin law and reversed cyclic stress-strain behavior.

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.

In-Phase and Out-of-Phase Multiaxial Fatigue

1991 ◽  
Vol 113 (1) ◽  
pp. 112-118 ◽  
Author(s):  
F. Ellyin ◽  
K. Golos ◽  
Z. Xia
Keyword(s):  
External Pressure ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Pressure Vessel Steel ◽  
Proportional Loading ◽  
Vessel Steel ◽  
Total Strain Energy Density ◽  
Number Of Cycles ◽  
Life Predictions ◽  
Cycles To Failure

In this investigation, thin-walled circular cylindrical specimens fabricated from a low alloy pressure vessel steel (ASTM A-516 Gr. 70) were subjected to various multiaxial loading conditions. The tests were conducted under strain-controlled condition, and loading was provided through an axial actuator and internal and external pressure across the specimen wall. Four in-plane strain ratios (ρ = Δεt/Δεa) were tested, and the most damaging case was the equi-biaxial in-plane straining, ρ = 1. For the latter condition, 90 deg out-of-phase loading was also investigated. These tests indicated a dramatic decrease in the number of cycles to failure, Nf, as a result of out-of-phase loading. The influence of the plastic strain path on life is thus clearly demonstrated. It is shown that the total strain energy density, ΔWt = ΔWe+ + ΔWp, correlates with both the in-phase and out-of-phase cyclic tests, and therefore is a proper damage parameter to be used for life predictions. A brief description of how ΔWt can be calculated is given for the case of proportional loading. The predicted results are compared with the experimental data, and the agreement is found to be very good indeed.

Low Cycle Fatigue Behaviour of GX12CrMoVNbN9 -1 Cast Steel at Room Temperature

2011 ◽  
Vol 291-294 ◽  
pp. 1106-1109 ◽  
Author(s):  
Grzegorz Golański ◽  
Krzysztof Werner ◽  
Stanisław Mroziński
Keyword(s):  
Heat Treatment ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Cast Steel ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Number Of Cycles ◽  
Stabilization Period

The report treats of the low cycle fatigue (LCF) behaviour of GX12CrMoVNbN9-1 (GP91) cast steel after heat treatment (1040°C/12h/oil + 760°C/12h/air + 750°C/8h/furnace). Fatigue tests were carried out at room temperature for five levels of the controlled total strain amplitude εac = 0.25, 0.30, 0.35, 0.50 and 0.60 %. The research performed within the scope of LCF has shown in general that the investigated cast steel was subject to strong cyclic weakening, revealing no stabilization period at the same time. At the final stage of fatigue there was quick weakening of the material which proceeded till its destruction. The growth of amplitude εac resulted in reducing the number of cycles till the destruction stage.

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.

The Influence of Multiaxial Superimposed Static Mean Stress on High-Cycle Fatigue Life of Cu-ETP Copper

2016 ◽  
Vol 250 ◽  
pp. 157-162
Author(s):  
Lukasz Pejkowski ◽  
Dariusz Skibicki ◽  
Mateusz Wirwicki
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Mean Stress ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Proportional Loading ◽  
Mean Stresses

High–cycle multiaxial fatigue tests under proportional and non-proportional loading conditions with various combinations of superimposed static mean stresses was carried out on Cu-ETP copper. The results show differences in fatigue life between various ratios of mean stresses. These results are similar to others described in the literature.

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.

On the Influence of Strain-Path in Multiaxial Fatigue Failure

1987 ◽  
Vol 109 (2) ◽  
pp. 107-113 ◽  
Author(s):  
Han C. Wu ◽  
C. C. Yang
Keyword(s):  
Crack Initiation ◽  
Strain Path ◽  
Path Dependence ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Crack Initiation And Propagation ◽  
Torsional Fatigue ◽  
Initiation And Propagation ◽  
Strain Paths ◽  
Tubular Specimens

A set of strain-controlled experiments has been performed on tubular specimens of annealed stainless steel. The strain-paths are designed to highlight the characteristics of path-dependence in the axial-torsional fatigue tests. Fatigue life, directions of crack initiation, and propagation are the subjects of interest in this investigation. They have been observed to be strongly influenced by the strain-path. For all the specimens tested, crack initiation was in the tensile mode.

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