Applied Mechanics and Materials Vols. 799-800

Abstract: Previous studies on corrugated metal gaskets have established that the contact width, contact stress, and surface roughness are important design parameters for optimizing gasket performance. However, the contact stress and contact width considering the surface roughness when the leakage occur did not defined yet. In this study, we determined the real contact stress and contact width when leakage started on 25A-size metal gasket. The contact width determined through a comparison between simulation and experimental results. The contact stress determined through a simulation analysis. The experiment involves a helium leakage test using new metal gaskets having different surface roughness levels. The result justified that the real contact width and average contact stress when the leakage started occur were 0.195mm and 800MPa, respectively. There is a good agreement for contact width both by simulation and experiment result. The contact width for flange having surface roughness 1.5μm is longest than the others.

Abstract: The refrigeration circle performance of air conditioning comparing analysis and displacement between R1270 and R22 is studied in this paper. In addition, the system performance optimization of R1270 refrigeration circle is discussed.The experimental results show that the smaller tube diameter of heat exchanger for R1270 system is easy to improve the energy efficiency ratio in the unimproved system.These results are important for theory and reality to research this type of air conditioning.

Abstract: In micro-scale flow condition, the flow rate and fluid extrusion expansibility are always affected by the wall slip between the fluid and tube wall. In this research, a wall slip model based on a micro-tube flow was developed, and then the wall slip effect on the viscous fluid micro-extrusion process was explored by computational fluid dynamics (CFD) with different extruding pressures. The results showed that wall slip make the fluid resistance and expansibility decrease, and the fluid mass flow rate increase.

Abstract: At present, we usually obtain the prediction models of hydraulic structure concrete strength through lots of tests or engineering experience. But when we use the models to predict the concrete strength at a certain time , there may be some discrepancies with the actual value, even some unreasonable situations. During the service period of hydraulic structure, we can get some new information about the concrete strength by the means of safety testing, monitoring or experimenting. With reference to these new information, the Bayes dynamic prediction method can update the time-varying model of concrete strength mentioned above. This method can more accurately predict the concrete strength value of the next moment.

Abstract: The main objective of this work is to develop a new approach based on the Lattice Boltzmann method (LBM) to simulate the extrudate swell of an Oldroyd B viscoelatic fluid. Two lattice Boltzmann equations are used to solve the Navier-Stokes equations and constitutive equation simultaneously at each time iteration. The single LBM model is used to track the moving interface in this paper. To validate the accuracy and stability of this new scheme, we study the steady 2D Poiseuille flow firstly, finding the numerical results be in good accord with the analytical solution. Then the die-swell phenomenon is solved, we successfully acquire the different swelling state of an Oldroyd B fluid at different time.

Abstract: Research activities on active repairs and stress control of structures using piezoelectric actuators and adhesive bond have received much attention in recent years. The function of the adhesive bond on active repair is to transmit the induced stresses by the piezoelectric actuator to the host structure in order to reduce the stress intensity on the crack front. Assessment of repair performance of adhesive bonds is done based on the transfer of the shear and peel stress concentration in the adhesive layer. In the present work, three dimensional finite element analyses have been carried to understand the effects of adhesive properties on active repair performance of a cracked aluminium plate under mode I. Adhesive efficiency is evaluated by the stress intensity factor (SIF) as a fracture criterion. The results show that SIF varies inversely with the adhesive layer’s shear modulus.

Abstract: This paper focuses on the optimization of flexural strength and thermal conductivity of mortar reinforced with Alfa fibers. Fibers were manually extracted from Alfa leafs to avoid the risk of degradation of mechanical properties. A first group of samples (300 x 300 x 30 mm) having a fiber volume fraction of 0.5 to 1.5% is prepared to measure the thermal conductivity.The second composite family (40 x 40 x 160 mm) cured in a wet chamber is used for measuring its bending strength. The fiber percentage varies from 0.74 to 1,85%.The results show that the thermal conductivity decreases by increasing the fiber content. While the optimal percentage of fiber for the flexural strength is estimated at 1%, corresponding to an increase of 27% in strength.

Abstract: A 3 DOF lumped mass tracked vehicle model was constructed in Matlab Simulink Environment and used for positioning the vehicle on gradients and missile firing operations. Pitch center, roll center and system parameters such as equivalent stiffness values, equivalent damping values and equivalent mass/inertias of 3 DOF model were obtained from 32+ degrees of freedom tracked vehicle model by simulations. Moments in pitch and roll directions were applied to the vehicle to find the pitch and roll centers. A range of step forces in bounce direction and a range of step moments in pitch and roll directions were applied to the vehicle and responses in the related directions of 32+ degrees of freedom model were used to determine the system parameters of 3-DOF model. Finally attitude of the vehicle on the gradients and missile firing scenario were simulated with both models and the results showed that 3 DOF model reasonably predicts the behavior of the tracked vehicle.

Abstract: Front crash has high probability in tranfic accident, and the front energy absorption part plays a very important role during the crash and is the key point to protect the safety of the occupant. The whole vehicle front crash is simulated in software LS-DYNA. This paper fix out the key steps and parameters in FEMB, and make good advise for finite anlysis. Finite anlysis is used in this paper to study motionstate of the vehicle and the energy absorption. Due to the anlysis, we find out that the front longitudinal beam is the most important component in the crash.

Abstract: Electromagnetic control valve; widely known as ECV, is one of the important components used in variable displacement type compressor for air conditioning control system. It controls the compressor operation on the basis of pulse width modulation (PWM) technique that used to encode the information for transmission. PWM technique allows the control of the power supplied from an external controller to the electrical devices, especially to inertial loads. Different pressure ports in ECV, basically acts as the connecting passages through the ECV for air/refrigerant flow functions. Supply of current and duty control is an important issue that highly concerns to the crankcase flow (P_c flow) through the crankcase pressure port of the ECV. In this research paper, effect of duty control is investigated during the P_c flow at the crankcase pressure port of ECV.