Papers by Author: Hui Chen Yu

Abstract: In the present research, the influence of the adhesive thickness on the cohesive properties and the overall strength of metallic adhesive bonding structures were investigated with the cohesive zone model to equivalently simulate the adhesive layers with various thicknesses. A theoretical approach was developed to determine the cohesive parameters for the present model when the adhesive thickness varied. And then some numerical examples were given to explore the adhesive thickness-dependence overall strength of the adhesive joints, followed by the comparison with the existing experimental results. Furthermore, the variations of both the cohesive parameters and the overall strength with the various thicknesses were influenced by the ductility of adhesives, which were investigated finally. The results showed that both the cohesive parameters and overall strength of metallic adhesive bonding structures were dependent on the adhesive thickness. Moreover, the variation of overall strength corresponding to brittle adhesive was more remarkable compared to that of ductile adhesive, especially in the comparatively small thickness range.

Abstract: The material properties of single crystal (SC) superalloys are orientation-dependent. To fully exploit the material capacity, the life modeling needs to consider the anisotropy. In the present study the life modeling of SC nickel-base superalloys is considered by employing the modified Mücker's anisotropic theory in which a Hill type function is utilized for describing the anisotropic failure. Strain-controlled low cycle fatigue (LCF) experiments of SC nickel-base superalloys at different crystallographic orientations (i.e. [00, [01 and [11) under high temperatures (i.e. 760°C) are carried out to verify the modeling availability for the modified Mücker's anisotropic theory. Further, based on the stress-strain field obtained by the anisotropic elastoplastic constitutive model coupled with the finite element method (FEM), the modified Mücker's anisotropic theory is employed to predict the fatigue life for SC flat plate with a hole.

Abstract: Strain-controlled low cycle fatigue (LCF) and creep-fatigue interaction (CFI) tests of an equiaxed crystal nicke-base superalloy were conducted at 850oC in order to investigate the effects of different dwell times and strain ratios on the fatigue behavior and life distribution. The cyclic damage accumulation (CDA) method and modified CDA method were employed to predict the fatigue life for the superalloy under complex loading condition, respectively. CDA method is employed to predict the fatigue life for the superalloy and the predicted fatigue life is within the scatter band of±6X. The fatigue life predicted by the modified CDA method agrees very well with the experimental fatigue life and the predicted fatigue life is well within the scatter band of±3X, which means that the modified CDA method is able to consider the influences of dwell time and strain ratio on the fatigue life for the superalloy.