Issue 40

Z. Zhang et alii, Frattura ed Integrità Strutturale, 40 (2017) 149-161; DOI: 10.3221/IGF-ESIS.40.13 150 strengthen the structure’s integrity and improve the lateral stiffness. Fortney et al. [3-4] raised the concept of changeable steel coupling beam, namely safety wire, was weakened to dissipate the energy via shear yielding and could be replaced conveniently after damage. Chung et al. [5] proposed a frictional damping device in the middle of coupling beam to decrease the response of shear wall structure under earthquake. Kim et al. [6,7] developed a compound energy-dissipation damper component by combining high-damp rubber material with two U-Shape Steel plate. Mao et al. [8] proposed a new shape memory alloy damper, which was applied as a replaceable coupling beam. However, the existing coupling shear beam dampers are very complicate and are difficult for manufacturing. Besides, there is a lack of analysis on the failure mechanism and dissipation performance. Under this background, we proposed an easy-making shear coupling steel beam damper and also designed corresponding cyclic shear experiments to investigate the bearing capacity and energy dissipation performance. Besides, the infrared camera is used during the fatigue test process in order to record the temperature distribution and temperature change. The temperature signal then is used to analyze and evaluate the energy dissipation related to local fatigue damage. Nondestructive evaluation has been used in many areas for a long time, which includes ultrasonic nondestructive testing [9] and Infrared thermography and so on. Based on the temperature variation, infrared thermographic method is applied to determine the fatigue performance parameters in real time [10]. Temperature variation is a macro behavior of energy dissipation during fatigue process, which could reflect the energy transformation during cumulative fatigue damage process and is closely related with the evolution of interior damage [11]. Todhunter [12] studied the relationship between the temperature change and deformation. In the following 160 years, the thermos-elasticity theory was under intensive study and was improved step by step, which has been developed as a systematic theory [13]. Inglis [14] studied the relationship between fatigue and cyclic hysteresis energy, which motivated scholars to study the inner relationship between the damage evolution and the energy absorbption and dissipation during the fatigue process. As the high-speed and high-sensitivity infrared camera came out during the recent 30 years, more and more people not only paid attention on the application of nondestructive testing, but also studied the energy dissipation and thermal energy during the cyclic fatigue test to evaluate the fatigue response based on fatigue damage model and failure criteria [15-17]. Fan et al. [18,19] built the energy relationship of Miner linear cumulative damage theory based on energy dissipation theory and infrared thermography method, which could well predict the residual life of components in an easy understanding way. Zhang [20] and etc designed the coupling beam damper with Kriging surrogate model and provided a new framework to design the coupling beam dampers. I NFRARED THERMOGRAPHY AND ENERGY BALANCE Introduction to infrared thermography ccording to generalized Hooke’s law, the stress-strain relationship for isotropic elastic material with thermal load is shown below:          1 2 3 ii ii v T E (1) where,         11 22 33 ii is the change of principle strain,         11 22 33 ii is the change of principle stress, α is the linear expanding coefficient, Δ T is the change of temperature, E is Young’s modulus, ν is poisson’s ratio. The change of temperature for elastic material under adiabatic condition follows the following rule:        3 ii v TK T C (2) In which T is the absolute temperature, C v is Constant Volume Specific Heat, ρ is density, K is bulk modulus. By substituting the equation of the relationship between Constant Volume Specific Heat (C v ) and specific heat at constant pressure (C p ): C p -C v =(3Eα2T)/(ρ(1-2ν)), the following equation could be achieved:        3 ii v T T C (3) A