Crack initiation and early growth behavior of TC4 titanium alloy under high cycle fatigue and very high cycle fatigue

2018 ◽  
Vol 33 (8) ◽  
pp. 935-945 ◽  
Author(s):  
Wei Li ◽  
Ning Gao ◽  
Hongqiao Zhao ◽  
Xinxin Xing
Keyword(s):  
Titanium Alloy ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Early Growth ◽  
Growth Behavior ◽  
Cycle Fatigue ◽  
Tc4 Titanium Alloy ◽  
Very High Cycle Fatigue ◽  
Image Position ◽  
Very High

Abstract

Crack initiation in the very high cycle fatigue regime of nitrided 42CrMo4 steel

2017 ◽  
Vol 32 (23) ◽  
pp. 4305-4316 ◽  
Author(s):  
Anja Weidner ◽  
Tim Lippmann ◽  
Horst Biermann
Keyword(s):  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
42Crmo4 Steel ◽  
Image Position ◽  
Very High

Abstract

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 Effect of Surface Mechanical Attrition Treatment on the very high cycle fatigue behavior of TC11

2018 ◽  
Vol 165 ◽  
pp. 09001
Author(s):  
Tao Gao ◽  
Zhidan Sun ◽  
Hongqian Xue ◽  
Delphine Retraint
Keyword(s):  
Titanium Alloy ◽  
Fatigue Strength ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Surface Mechanical Attrition Treatment ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Mechanical Attrition ◽  
Before And After ◽  
Very High

As an important engine component material, TC11 (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) titanium alloy is subjected to high frequency cyclic loading and its failure occurs beyond 109 cycles. It is thus essential to investigate the very high cycle fatigue (VHCF) behavior of this alloy. Surface Mechanical Attrition Treatment (SMAT) is a promising surface treatment technique to improve fatigue strength by modifying the surface microstructure. Therefore, it is important to understand the fatigue damage and failure process of SMATed titanium alloy in the VHCF regime. In this work, VHCF tests of TC11 before and after SMAT under fully reversed loading were conducted at room temperature by using an ultrasonic fatigue testing machine at a frequency of 20 kHz. The preliminary results seem to indicate that SMAT can reduce fatigue strength and fatigue life of TC11. Fracture surface analysis of the specimens before and after SMAT was performed using scanning electron microscope (SEM) to investigate the mechanisms of crack initiation and propagation. Particular attention was paid to fatigue crack initiation sites. The effect of SMAT on damage mechanism of SMATed TC11 in the VHCF regime was discussed.

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