Preprint Article Version 1 This version is not peer-reviewed

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

Version 1 : Received: 30 October 2017 / Approved: 30 October 2017 / Online: 30 October 2017 (10:22:24 CET)

How to cite: Baohua, N.; Zihua, Z.; Yongzhong, O.; Dongchu, C.; Hong, C.; Haibo, S.; Shu, L. Effect of LCF Pre-Damage on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy. Preprints 2017, 2017100182 (doi: 10.20944/preprints201710.0182.v1). Baohua, N.; Zihua, Z.; Yongzhong, O.; Dongchu, C.; Hong, C.; Haibo, S.; Shu, L. Effect of LCF Pre-Damage on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy. Preprints 2017, 2017100182 (doi: 10.20944/preprints201710.0182.v1).

Abstract

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.

Subject Areas

very high cycle fatigue; fatigue pre-damage; titanium alloy; LCF

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