Experimental and simulation study on Ⅰ-Ⅱ mixed-mode fatigue crack growth of TC4-DT welded joint

Abstract

The crack growth in the structure shows the complex Ⅰ-Ⅱ mixed-mode under the combined tensile and shear fatigue loading. It is of great significance to understand its growth law for evaluating the fatigue life of structures accurately. In order to study the fatigue crack growth law of Ⅰ-Ⅱ mixed-mode welded joint of TC4-DT alloy, compact tension-shear (CTS) specimens were designed and machined, fatigue crack growth tests of welded joints under different loading angles were carried out, curves and fatigue crack growth paths of welded joints under Ⅰ-Ⅱ mixed-mode crack propagation were obtained. Based on the above situation, the equivalent stress intensity factor of Ⅰ-Ⅱ mixed-mode was introduced and the Paris law was employed to deduce the Ⅰ-Ⅱ mixed-mode crack growth rate equation of TC4-DT welded joint. In addition, the extended finite element method (XFEM) was adopted to simulate the fatigue crack growth progress of Ⅰ-Ⅱ mixed-mode crack, and the growth law under different loading modes were obtained and compared with test results. The research shows that the error values of the cracking angle under different loading modes are less than 10% compared simulation with experiment. What's more, the simulated growth paths are agree with the experimental results well. XFEM shows its advantages in simulating crack problems. XFEM can predict mixed-mode fatigue crack growth paths effectively.

Keywords

• tc4-dt titanium alloy
• ⅰ-ⅱ mixed-mode fatigue crack
• crack growth paths
• cts specimen
• extended finite element method