An efficient method utilizing the concept of inverse heat conduction is presented for the thermal analysis of pistons based on application to a liquid-petroleum-liquid injection (LPLI) engine piston. An inverse heat conduction problem is established in the form of an optimization problem. In the optimization problem, the convection heat transfer coefficient (HTC) on the combustion-side surface of the piston is defined as the design variable, while the error between the measured and analysed temperatures is defined as the objective function. For the optimization, two consecutive steps consisting of an axisymmetric and a three-dimensional problem are presented in order to reduce computation time and to obtain stable convergence. The optimum distribution of the HTC at the top surface of the piston is successfully determined through a numerical implementation. The temperature obtained via an analysis using the optimum HTC is compared with the measured temperature, and reasonable agreement is obtained. The present method can be effectively utilized to analyse the temperature distribution of engine pistons.
A new method linking experimental and theoretical approaches is proposed to precisely analyse the failure of liquid crystal display (LCD) panels under mechanical drop. Generally, the thickness of a glass plate for LCD panel is less than 0.7 mm, and thus requires sufficient strength to withstand mechanical shock. In the present work, the fracture toughness (K IC ) of panel glass obtained experimentally is compared with the stress-intensity factor (K I ) calculated using the maximum stress at weak points via a finite-element drop simulation in order to evaluate crack growth on the panel. It is demonstrated that this approach is simple but effective to determine the specification of components at the design level, including the roughness of glass panel edges. Furthermore, from a dynamic simulation, important information related to the shockproof design of an LCD panel is gathered.
A systematic method as applied to an air circuit breaker (ACB) system is proposed to analyse the links of the spring-actuated linkage under repetitive impact loading. A fatigue life equation applicable to the links is presented on the basis of the fatigue test. The result obtained from the multi-body dynamic analysis is compared with that from the experiment. For the explicit finite element analysis of the links, the impact loading obtained from the dynamic analysis of the ACB system is used as the initial conditions. To enhance the fatigue life of a weak link, two modified designs are proposed and their maximum stresses are reduced very much compared with that of the original design. Considering a safety margin, one modified design satisfies the required specification of the fatigue life. The proposed approach in this work can be efficiently used in designing stable and reliable links of the ACB and in analysing a similar spring-actuated linkage system.
The responses of a cabinet for a reactor protection system under seismic loadings are analysed by using the finite-element method, and its dynamic characteristics are evaluated. Analysed modes are compared with the measured data from a resonance search test. The structural safety of the cabinet is evaluated considering the required response spectrums of the operation-base and safe-shutdown earthquakes. The transient response of the cabinet is analysed by utilizing the measured acceleration of the vibration table representing the seismic motion of the ground. Time histories of accelerations at the locations of major internal parts are extracted. The transient responses are compared with those from the seismic test and the results were found to closely represent the system.
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