Abstract
Titanium-alloy laminates fabricated by sheet materials using diffusion bonding process have drawn more and more attention in the recent years. Proper placement of nonwelded zones on the diffusion bonding (DB) interface within titanium-alloy laminates as crack arrest zones can improve damage tolerance. To achieve the optimal damage tolerance via designing non-welded zones, it is necessary to study fatigue crack growth characteristics for this type of laminates by adjusting all the relevant parameters such as geometrical sizes, locations, and the number of the nonwelded zones, which is highly time consuming. Therefore it is essential to develop a reliable and quick method to analyze the fatigue crack growth characteristics for titanium-alloy laminates with non-welded zones. In this paper, the extended finite element method (XFEM) which was employed to simulate the fatigue crack growth process and the applicability of this method to capture fatigue crack growth characteristics of titanium-alloy laminates with localized non-welded zones was also studied. The numerical results were compared with the experiment data, and the agreement on numerical and experimental results illustrated that the specific crack growth characteristics can be captured by using XFEM, thereby verifying the applicability of XFEM in the analysis of fatigue crack growth of the laminates with non-welded zones. The influence of non-welded zones on the fatigue crack growth was then discussed.
Highlights
Titanium alloys have over the years proven themselves to be technically superior and cost effective materials for a wide range of applications spanning the industries of aerospace, marine, and even commercial products [1]
There is a disadvantage that the residual life is relatively short once the damage appears in the structure which is made of common titanium alloy. (Damage is inevitable .) the common titanium alloys are ineffective in damage tolerance design [3], and developing the technology that is able to improve the damage tolerance becomes an important issue
Some experimental investigations demonstrate that the DB interfaces in the titanium alloy-laminates which are made by diffusion bonding process have significant inhibitory effect on the growth of the fatigue crack [5, 6]
Summary
Titanium alloys have over the years proven themselves to be technically superior and cost effective materials for a wide range of applications spanning the industries of aerospace, marine, and even commercial products [1]. In order to improve the applicability of titanium alloys to damage-tolerance-design, one traditional method is through microstructural control, and another method is through the use of submacro laminated structures [4]. Some experimental investigations demonstrate that the DB interfaces in the titanium alloy-laminates which are made by diffusion bonding process have significant inhibitory effect on the growth of the fatigue crack [5, 6]. Something more interesting, is that the diffusion bonded laminates of TC4 titanium alloy may have longer fatigue life if the localized nonwelded zone exists in the DB interfaces. This indicates that the defects may achieve significant inhibition of crack growth when the defects lie in the proper position. The results will give the technical support in the damage tolerance design of titanium-alloy laminates
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