Key Engineering Materials Vols. 324-325

Abstract: FBG sensors have excellent compatibility with CFRP sheets. It can be embedded into CFRP sheets to fabricate the “smart” CFRP. This paper conducted 4 pieces of CFRP-strengthened RC beams, and embedded FBG sensors and strain gauges on the steel, concrete and CFRP of RC beams. The simulation program of flexural load effects of RC beams is compiled based on the theory of reinforced concrete and ANSYS. The experimental results show that during the load bearing process: the compatibility is perfect between FBG sensor and CFRP; the linear relationship of FBG sensor and strain gauge is uniform; the numerical simulation results and the measuring results of strains of tensile steel and compressive concrete, the load agree well. So utilizing the smart CFRP strengthened RC structures can realize the dual function of advanced rehabilitation and real-time health monitor and evaluation.

Abstract: The side-gusset plate is connector of the combined-roller, which is the key component of the High-pressure Grinding Roller equipment that is applied in crushing raw iron ore, Fracture occurred at the bottom of the side-gusset plate while the roller’s operation. For exploring the reason of fracture, the stress distribution and corresponding critical location of the side-gusset plate were computed and analyzed according to two working situations based on finite element method. The analysis result illustrates that it is the failure of infant mortality because of overloading, not belongs to fatigue behavior, with the presence of the component operating time and the fracture cross-section’s granular feature as well. This result is a reliable foundation for succeeding redesign and manufacturing of side-gusset plate and other component, the feasible plan was brought forward to improve the component operation’s stability.

Abstract: An explicit dynamic Galerkin meshfree formulation under the updated Lagrangian framework is presented to simulate large deformation damage and failure process in geomaterials. The failure initiation and development are characterized by the pressure sensitive Drucker-Prager plasticity coupled with the isotropic energy-based damage theory. A stabilized conforming nodal integration based on non-local gradient smoothing is employed to improve the computational efficiency and to regularize the material instability arising from strain localization. The capability of the proposed methodology to model the evolution of dynamic failure in geomaterials is demonstrated through a numerical example.

Abstract: In this paper, by adopting the continuous ring model and the perturbation analysis for free vibration, the authors showed the reason and the importance for the modes split phenomena and provided the qualitative relation between modes split and perturbation for the harmonic number of stiffness perturbation. Also through the modal analysis for forced vibration the authors showed possible ways to predict and prevent the worst case when blade will crack. That is, the harmonic number for stiffness distribution should be avoided to be twice the engine order.

Abstract: The aim of the present paper is to evaluate the interfacial fracture toughness of an Al/Epoxy adhesive system with a crack lying at the interface. A cracked lap shear specimen loaded in four point bending is adopted and the fracture toughness is pointed out in terms of the critical complex stress intensity factor. To this aim numerical analyses of the fracture specimen have been carried out using a commercial finite element code. In addition, fracture surfaces are analyzed and the locus of failure is discussed.

Abstract: A uniaxial experimental set-up was developed to evaluate the self-induced stresses, visco-elastic strains and cracking potential of concrete from the time of its placement. The totally restrained condition is achieved by keeping the length change within a threshold of 3μm. The temperature rise of the specimens can be controlled within 1.5
, by which the deformation because of temperature change due to cement hydration could be prevented. The tensile force required to compensate the shrinkage could be monitored and elastic strain and tensile creep can be calibrated without an obvious interference of temperature deformation. The preliminary results testified the workability of the system.

Abstract: A novel approach for crack identification based on jointly time-frequency analysis is presented in the paper. A bilinear stiffness model for the breathing crack was introduced to represent the nonlinear dynamics of a cracked beam. The nonlinearity of the dynamic responses due to the crack opening-closing is used to identify the occurrence of the crack. The Wigner-Wille distribution technique is applied to analyze the response signals and the instantaneous frequency is extracted as damage-sensitive feature. The numerical simulations of a breathing crack model were carried out to validate the possibility and effectiveness of the proposed approach. The effects of crack severity and sampling frequency on crack identification were also studied in the simulations respectively. The results show that the proposed method can effectively identify the crack with slight severity without any baseline model or data, and the better the identification obtains as the larger the sampling frequency. The study demonstrates that the proposed approach by using of jointly time-frequency analysis is a promising technique for crack identification.

Abstract: Liquid corrosion of steam turbine blade has become an important reason for blade failure in supercritical parameter power plant and nuclear power plant. In order to improve the reliability of blades in wet steam stages of steam turbine and prevent blade failure from liquid corrosion, a nonlinear coupling wave model has been developed to investigate the high speed impact between ball liquid droplet and elastic solid, according to a mass of numerical results of impact between liquid droplet and elastic solid made by 1Cr13 which is a typical material for steam turbine blade, the relational expression between dimensionless equivalent peak stress and impact speed mach number is obtained. Then suitable equations to evaluate the fatigue life of crack initiation and nonlinear cumulative damage rule are adopted to develop numerical model for liquid corrosion fatigue life of blade, and the liquid corrosion fatigue life of a wet steam blade is analyzed in detail. It is shown that the nonlinear coupling wave model for impact and the analysis model of liquid corrosion fatigue life for blade can give some quantitative results, it may be helpful to evaluate liquid corrosion fatigue life of blade and prevent blade from liquid corrosion during blade design.