Browsing by Author "Jin, Xiaochao"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Crystal plasticity constitutive model and thermodynamics informed creep-fatigue life prediction model for Ni-based single crystal superalloy
    (Elsevier, 2023-07-23) Lu, Pin; Jin, Xiaochao; Li, Pan; Sun, Yongle; Fan, Xueling
    Ni-based single crystal superalloys are the main constituent materials for aeroengine turbine blades. They are subjected to extensive in-service plastic deformation and creep-fatigue interaction, which can cause damage and failure and hence limit the turbine blade durability. In this study, a novel crystal plasticity-based constitutive model is proposed to predict the cyclic inelastic deformation of Ni-based single crystal superalloy under creep-fatigue loads, and the key aspects examined include cyclic strain hardening, ratcheting and stress relaxation behavior. The novelty of the model lies in the introduction of a dislocation density parameter in the kinematic hardening rule to describe the evolutionary characteristics of hysteresis loops. The constitutive model is implemented via the crystal plasticity finite element method and the predictions are in good agreement with experimental results. Furthermore, thermodynamic entropy generation is innovatively adopted as an indicator parameter for analysis of Ni-based single crystal creep-fatigue failure, and the corresponding creep and fatigue damage models are developed to evaluate the degree of damage. The half-life concept associated with the steady-state hysteresis loop is employed in the failure model to predict the creep-fatigue life without being limited by the computational efficiency of the crystal plasticity finite element method. The proposed model can well capture the characteristics of Ni-based single crystal creep-fatigue life, and the prediction falls within a scatter band of factor 2.0 compared to experimental results. The proposed creep-fatigue life prediction model is underpinned by deformation and failure mechanisms, which would provide a basis for accurate analysis and robust assessment of Ni-based single crystal superalloy performance and life.
  • Thumbnail Image
    ItemOpen Access
    Fabrication and characterisation of high-performance joints made of ZrB2-SiC ultra-high temperature ceramics
    (Elsevier, 2021-08-16) Jin, Xiaochao; Yang, Jingjing; Sun, Yongle; Li, Pan; Hou, Cheng; Zhao, Yuxiang; Fan, Xueling
    Joining is crucial for ultra-high temperature ceramics (UHTCs) to be used in demanding environments due to the difficulty in manufacturing large and complex ceramic components. In this study, ZrB2-SiC composite UHTCs parts were joined via Ni foil as filler, and the mechanical properties and oxidation behaviour of the fabricated ZrB2-SiC/Ni/ZrB2-SiC (ZS/Ni/ZS) joint were investigated. Firstly, dense ZrB2-SiC composites were prepared from nano-sized powders by spark plasma sintering (SPS). The ZrB2-SiC parts were then joined using SPS. Furthermore, the elastic modulus, hardness, shear strength and high temperature oxidation behaviour of the ZS/Ni/ZS joint were examined to evaluate its properties and performance. The experimental results showed that the ZrB2-SiC parts were effectively joined via Ni foil using SPS and the resultant microstructures were free from any marked defects or residual metallic layers in the joint. Although the elastic modulus and hardness in the joining zone were lower than those in the base ZrB2-SiC ceramics, the shear strength of the joint reached ∼161 MPa, demonstrating satisfactory mechanical properties. Oxidation tests revealed that the ZS/Ni/ZS joint possesses good oxidation resistance for a wide range of elevated temperatures (800–1600 oC), paving the way for its employment in extreme environments.