Very High Cycle Fatigue Properties of Welded Joints under High Frequency Loading

2013 ◽  
Vol 647 ◽  
pp. 817-821
Author(s):  
Chao He ◽  
Yong Jie Liu ◽  
Qing Yuan Wang
Keyword(s):  
Base Metal ◽  
Welded Joints ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Ambient Air ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High

Very high cycle fatigue (VHCF) properties of welded joints under ultrasonic fatigue loading have been investigated for titanium alloy (TI-6Al-4V) and bridge steel (Q345). Ultrasonic fatigue tests of base metal and welded joints were carried out in ambient air at room temperature at a stress ratio R=-1. It was observed that the fatigue strength of welded joints reduced by 50-60% as compared to the base metal. The S-N fatigue curves in the range of 107~109 cycles of base metal and welded joints for both materials exhibited the characteristic of continually decreasing type. The fatigue failure still occurred after 107 cycles of loading, and the fatigue limit in traditional does not exist. The fatigue facture mainly located in the weld metal region at low cycle fatigue range, but in the fusion area in HCF and VHCF. Analysis of fracture surfaces analyzed by SEM revealed that the fatigue cracks initiated from welding defects such as pores, cracks and inclusions.

scholarly journals Usability of Ultrasonic Frequency Testing for Rapid Generation of High and Very High Cycle Fatigue Data

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2245
Author(s):  
Michael Fitzka ◽  
Bernd M. Schönbauer ◽  
Robert K. Rhein ◽  
Niloofar Sanaei ◽  
Shahab Zekriardehani ◽  
...  
Keyword(s):  
Strain Rate ◽  
High Cycle Fatigue ◽  
Fatigue Properties ◽  
Ultrasonic Frequency ◽  
Cycle Fatigue ◽  
Reinforced Polymer ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Fibre Reinforced Polymer ◽  
Very High

Ultrasonic fatigue testing is an increasingly used method to study the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of materials. Specimens are cycled at an ultrasonic frequency, which leads to a drastic reduction of testing times. This work focused on summarising the current understanding, based on literature data and original work, whether and how fatigue properties measured with ultrasonic and conventional equipment are comparable. Aluminium alloys are not strain-rate sensitive. A weaker influence of air humidity at ultrasonic frequencies may lead to prolonged lifetimes in some alloys, and tests in high humidity or distilled water can better approximate environmental conditions at low frequencies. High-strength steels are insensitive to the cycling frequency. Strain rate sensitivity of ferrite causes prolonged lifetimes in those steels that show crack initiation in the ferritic phase. Austenitic stainless steels are less prone to frequency effects. Fatigue properties of titanium alloys and nickel alloys are insensitive to testing frequency. Limited data for magnesium alloys and graphite suggest no frequency influence. Ultrasonic fatigue tests of a glass fibre-reinforced polymer delivered comparable lifetimes to servo-hydraulic tests, suggesting that high-frequency testing is, in principle, applicable to fibre-reinforced polymer composites. The use of equipment with closed-loop control of vibration amplitude and resonance frequency is strongly advised since this guarantees high accuracy and reproducibility of ultrasonic tests. Pulsed loading and appropriate cooling serve to avoid specimen heating.

Ultrasonic Fatigue of Ti6Al4V in the Very High Cycle Fatigue Regime

2012 ◽  
pp. 831-838
Author(s):  
Stefan Heinz ◽  
Frank Balle ◽  
Guntram Wagner ◽  
Dietmar Eifler
Keyword(s):  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High

scholarly journals Recent Advances in Very High Cycle Fatigue Behavior of Metals and Alloys—A Review

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1200
Author(s):  
Ashutosh Sharma ◽  
Min Chul Oh ◽  
Byungmin Ahn
Keyword(s):  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Simulation Studies ◽  
Cycle Fatigue ◽  
Future Directions ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High

We reviewed the research and developments in the field of fatigue failure, focusing on very-high cycle fatigue (VHCF) of metals, alloys, and steels. We also discussed ultrasonic fatigue testing, historical relevance, major testing principles, and equipment. The VHCF behavior of Al, Mg, Ni, Ti, and various types of steels were analyzed. Furthermore, we highlighted the major defects, crack initiation sites, fatigue models, and simulation studies to understand the crack development in VHCF regimes. Finally, we reviewed the details regarding various issues and challenges in the field of VHCF for engineering metals and identified future directions in this area.

Effect of shot peening on very high cycle fatigue of 2024-T351 aluminium alloy

2020 ◽  
Vol 10 (7) ◽  
pp. 1032-1039
Author(s):  
Renhui Tian ◽  
Jiangfeng Dong ◽  
Yongjie Liu ◽  
Qingyuan Wang ◽  
Yunrong Luo
Keyword(s):  
Fracture Surface ◽  
Crack Initiation ◽  
Shot Peening ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Fatigue Strength Improvement ◽  
Ultrasonic Fatigue ◽  
Very High

To investigate the influence of shot peening (SP) on very high cycle fatigue (VHCF) performance of 2024-T351, the specimens with three surface conditions were performed under ultrasonic fatigue tests: mechanicallypolished without peening (NP), ceramic shot peening (SP1), steel and glass mixed shot peening (SP2). The roughness, microhardness, residual stress, fractography measurement and scanning electron microscopy (SEM) were applied before fatigue test to characterize the effective layer induced by the peening treatment. For the failed specimens, the fracture surface were analysed using SEM to study the mechanisms of fatigue crack propagation. In addition, the fatigue life curve in ultra-high cycle region continuously decreased in the three series of specimens. However, the experimental results revealed that fatigue strength improvement resulting from shot peening treatment was negligible in very high cycle regime. Furthermore, the stress intensity factor for the surface crack initiation (SCI) and interior crack initiation (ICI) was discussed based on quantitative analysis on the fracture surface. The average values of ΔKfish-eye for NP, SP1 and SP2 specimens are about 2.22, 1.48 and 1.61 MPa · m1/2, respectively.

Very High Cycle Fatigue in Pulsed High Power Spallation Neutron Source

2014 ◽  
Vol 891-892 ◽  
pp. 536-541 ◽  
Author(s):  
Zhi Hong Xiong ◽  
Masatoshi Futakawa ◽  
Takashi Naoe ◽  
Katsuhiro Maekawa
Keyword(s):  
Strain Rate ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Air Cooling ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Neutron Spallation Source ◽  
Ultrasonic Fatigue ◽  
Very High

Very high cycle fatigue degradation of type 316L austenitic stainless steel, which is used as the structural material of neutron spallation sources under intensive neutron irradiation environment, is investigated by using an ultrasonic fatigue testing machine. The strain rate imposed on the structure of neutron spallation source is almost equivalent to that produced in the testing machine. The temperature on the surface was controlled by the air-cooling. The effect of strain rate on the fatigue strength is recognized to increase the fatigue limit.

scholarly journals Effect of LCF Pre-Damage on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy

2017 ◽  
Author(s):  
Nie Baohua ◽  
Zhao Zihua ◽  
Ouyang Yongzhong ◽  
Chen Dongchu ◽  
Chen Hong ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Mechanism Analysis ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

The effect of low cycle fatigue (LCF) pre-damage on the subsequent very high cycle fatigue (VHCF) behavior is investigated in TC21 titanium alloy. LCF pre-damage is applied under 1.8% strain amplitude up to various fractions of the expected life and subsequent VHCF properties are determined using ultrasonic fatigue tests. Results show that 5% of LCF pre-damage insignificantly affects the VHCF limit due to the absent of pre-crack, but decreases the subsequent fatigue crack initiation life estimated by Pairs’ law. Pre-cracks introduced by 10% and 20% of LCF pre-damage significantly reduce the subsequent VHCF limits. The crack initiation site shifts from subsurface-induced fracture for undamaged and 5% of LCF pre-damage specimens to surface pre-crack for 10% and 20% of LCF pre-damage specimens in very high cycle region. The fracture mechanism analysis indicate that LCF pre-crack will re-start to propagate under subsequently low stress amplitude when stress intensity factor of pre-crack is larger than its threshold. Furthermore, the predicted fatigue limits based on EI Haddad model for the LCF pre-damage specimens well agree with the experimental results.

scholarly journals Bending Fatigue Behavior of 316L Stainless Steel up to Very High Cycle Fatigue Regime

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4820
Author(s):  
Yongtao Hu ◽  
Yao Chen ◽  
Chao He ◽  
Yongjie Liu ◽  
Qingyuan Wang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Slip Band ◽  
316L Stainless Steel ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Propagation Mechanism ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

Effect of microstructure on the crack initiation and early propagation mechanism in the very high cycle fatigue (VHCF) regime was studied in 316L stainless steel (316L SS) by atomic force microscope (AFM) and electron back scattered diffraction (EBSD). The results show that small fatigue cracks initiate from the slip band near the grain boundaries (GBs) or the twin boundaries (TBs). Early crack propagation along or cross the slip band is strongly influenced by the local microstructure such as grain size, orientation, and boundary. Besides, the gathered slip bands (SBs) are presented side by side with the damage grains of the run-out specimen. Finally, it is found that dislocations can either pass through the TBs, or be arrested at the TBs.

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