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Quick Search     Adv Search 2016 Vol. 37, No. 6 Published: 2016-12-28 477 The stresses and cracks in thermal barrier coating system: A review Gas turbine is a class of clean and efficient power and energy machines, which has wide applications to air engine, power generation, chemical and oil engineering, etc. The manufacture of gas turbine is a mark of the manufacturing capability of a nation and is regarded as a pearl on the crown of manufacturing technology. Advanced gas turbines are featured by the high inlet gas temperature, as well as its continuous increase due to its key role in the turbine performance. The current inlet temperature of the advanced gas turbine has reached 1600?C and is expected to be 1700?C and much higher in the future. It is challenging to design and manufacture the high-temperature turbine blades working in such an extreme temperature environment. Thermal barrier coating system (TBCs) is one of a fewthe core technologies for the design and manufacturing of advanced gas turbines and has been playing important roles in the development history of gas turbines. TBCs can increase the inlet temperature and protect the turbine blades from oxidation, corrosion, foreign object impact, particle erosion and so on. Therefore, the thorough investigations of on the failure mechanisms and their influence factors of TBCs are crucial to the design, manufacturing and strength assessment of TBCs and furthermore ensure the safe service of gas turbines. In this review article, we present the more recent advances in studying the studies on the stresses and cracks in TBCs of gas turbine blades, including theoretical, experimental and numerical analyses. This paper covers the failure modes in TBC, the thermal stresses generated in the fabrication of TBC, the thermally grown oxide (TGO) and its resulting growth stress, the surface cracks, interface cracks and their competition in TBCs, the evaluation method of biaxial strength of TBCs, the delamination induced by the penetration of environmental CaO-MgO-Al3O2-SiO2 (CMAS) into coatings, and the sintering effect on the cracking of ceramic layer. Finally, potential directions for further research are concluded. 2016 Vol. 37 (6): 477-517 [Abstract] ( 1267 ) HTML (1 KB)  PDF   (0 KB)  ( 363 ) 518 Mechanical Properties and Mechanism of Shear Thickening Fluid Shear thickening fluid (STF) is a kind of dense suspensions, which is obtained by dispering nano or micro particles in polar dispersed medium. Under applying stress, the mechanical properties of STF will show rapid, significant and reversible changes. Due to the excellent ability of energy absorption, STF has great prospects in many applications, such as shock absorption, soft armor and dampers. In this paper, we firstly introduced the preparation of high performance STF, as well as the mechanical behaviors of STF under different loads. In addition, we discussed the state-of-the art for experimental and theoretical researches of the shear thickening mechanism. Finally, we concluded the practical applications of STF and proposed some future trends in this material developments. 2016 Vol. 37 (6): 518-537 [Abstract] ( 511 ) HTML (1 KB)  PDF   (0 KB)  ( 344 ) 538 Research on the structure design method of Pentamode Materials by considering global stability of structures Pentamode Materials are novel artificial acoustic metamaterials. And they are usually designed by using solid materials, which microstructures are micro truss structures. However, the structures constructed by Pentamode Materials are theoretically unstable. From the perspective of global analysis of the entire structure, this paper proposes a method by employing preloads to insure the stability of the designed structures with Pentamode Materials, and a sufficient condition for the stability of structures with Pentamode Materials is presented. Meanwhile, two numerical examples of typical microstructures of Pentamode Materials are offered to verify the condition. Furthermore, in order to apply and implement the stability condition of structures in the structural design procedure, an optimization model of structures is established to describe the design problem, which views the structure design with Pentamode Materials as the transformation procedure of Pentamode Materials. As a result, if the unit cells of Pentamode Materials are constructed by micro trusses the optimization model is simple, both of the structure stability constraints and the characteristic constraints of Pentamode Materials are linear. 2016 Vol. 37 (6): 538-552 [Abstract] ( 214 ) HTML (1 KB)  PDF   (0 KB)  ( 363 ) 553 Dynamic analysis of vehicle–bridge interaction considering the action of jump impacting force There exist a series of problems when using the traditional Hertz spring model for dynamic analysis of vehicle-bridge coupling vibration. Based on the simple model both for vehicle and bridge, the dynamics of vehicle-bridge coupled and uncoupled equation is derived. Usually, the rail shows some irregularities, such as the periodic and stochastic irregularities. When the vehicle moves on this kind of rail, it will jump if the centrifugal force is greater than the weight of the vehicle. Afterward, the vehicle will fall back to the beam under the action of gravity. During this course, an impact force will produce onto the beam. The paper proposed the role of impact laws and determined the impact parameters by finite element simulation. On the platform of MATLAB, the program code was edited for the single-axel vehicle model moving on the simple supported beam. The numerical results showed that the dynamic model involving vehicle impact force presents some more accurate response for vehicle-bridge coupling vibration characteristics. Furthermore, the model given in this paper can denote jump height about the vehicle. For the cases of periodic and stochastic irregularities with same amplitude, the stochastic irregularities will causes larger response for both bridges and vehicle, which will results in worse effect for comfortable ride as well as the safety. For this reason, we should pay more attention to the stochastic irregularities in vehicle-bridge coupling dynamic analysis. 2016 Vol. 37 (6): 553-558 [Abstract] ( 302 ) HTML (1 KB)  PDF   (0 KB)  ( 334 )

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