Proceedings

ICAF 2023
Delft, The Netherlands, 2023
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Low-cycle fatigue property and life prediction model of TC18 titanium alloy material


Go-down icaf2023 Tracking Number 86

Presentation:
Session: Session 7: Fatigue crack growth and life prediction methodsĀ  III
Room: Theatre room: plenary
Session start: 13:30 Tue 27 Jun 2023

Shaopu Su   shaopu_su@sina.com
Affifliation: Aircraft Atrength Research Institute

Binwen Wang   asriwbw@vip.163.com
Affifliation: Aircraft Atrength Research Institute

Xianmin Chen   chenxianmin@cae.ac.cn
Affifliation: Aircraft Atrength Research Institute

Lei Li   lilei623@avic.com
Affifliation: Aircraft Atrength Research Institute

Dengke Dong   dengke623@sina.com
Affifliation: Aircraft Atrength Research Institute


Topics: - Fatigue crack growth and life prediction methods (Genral Topics), - Fatigue life enhancement methods and repair solutions (Genral Topics)

Abstract:

As alpha+ beta type titanium alloy, TC18 is widely applied in the landing gear and flap slides with the advantages of high strength, excellent plasticity and weldability. Yet more service datum show that low-cycle fatigue failure sometimes occurs in the blocking hook of carrier-based aircraft due to its serious servicing environment. Consequently low-cycle fatigue performance plays an important role in the fatigue life evaluation of aircraft load-bearing structural parts. Through the low-cycle fatigue experiments of standard fatigue coupons, the static and low-cycle fatigue behaviours of TC18 titanium alloy were obtained, such as the stress-strain constitutive relationship, the cyclic stress-strain curve and the strain-life curve. In order to meet the engineering fatigue life evaluation for TC18, on the one hand, based on Manson-Coffin and reliability analysis theory, the strain life model was built and the low-cycle fatigue life curve under a certain survival rate was observed to investigate the life at certain confidence and reliability; on the other hand, combined with the damage mechanical theory, the gradual degradation process of the mechanical properties of TC18 titanium alloy with the increase of load times was described by the Lemaitre plastic damage model, and the fatigue damage accumulation parameters were determined based on experimental results. We obtain the conclusion as following:1) the cyclic behaviour of TC18 titanium alloy material is a strain cycle softening relationship under different strain-rate loading;2) its low-cycle fatigue fracture form is described that: the crack initiated in the form of quasi-cleavage fracture, and propagated by quasi-cleavage fracture or mixed-type fracture of quasi-cleavage and dimple, finally sheared at the edge of the specimen to form a shear dimple fracture ;3) Based on the experimental results, the engineering Manson-Coffin strain life model and macro-cyclic plastic damage theory model in the paper can be used for the low-cycle fatigue life evaluation of TC18 titanium alloy material.