Applied Mechanics and Materials Vols. 152-154

Abstract: Axial flow compressors work as an indispensable device in industry fields. Surge is a phenomenon of aerodynamic instability, which characterized by disruption of flow. When a compressor works in surge state, the vibration is so intense that it may causes accidents. Detecting surge timely and accurately not only insure safety of compressors but also is a key of active control of aerodynamic instability. Support vector data description (SVDD) is a one-class classification method developed based on the theory of support vector machine (SVM). In this paper, we introduce SVDD into the field of compressor surge detection. It demonstrates that SVDD method can give a warning far ahead of surge.

Abstract: The reflection spectrum from the Fiber Bragg Grating (FBG) sensors embedded in the composite was disturbed because of the thermal residual stress. In this study, two types of the FBG sensors, uncoated and UV-cured resin coated FBG sensors, were embedded in the triangle area of the T-stiffened composite panels. The strains during the curing process were measured by these two kinds of FBG sensors. Through the comparison of the results, it was found that the effect of thermal residual stress on the reflection spectrum could be attenuated when the FBG sensor was coated with UV-cured resin. Furthermore, the strain responses during the low-velocity impact test were observed by both two FBG sensors. The maximum-strain measured by the coated FBG sensors was more accurately than that measured by the uncoated one.

Abstract: The theoretical and computational aspects of interval methodology based on Chebyshev polynomials for modeling multibody dynamic systems in the presence of parametric uncertainties are proposed, where the uncertain parameters are modeled by uncertain-but-bounded interval variables which only need the bounds of uncertain parameters, not necessarily knowing the probabilistic distribution. The Chebyshev inclusion function which employs the truncated Chevbyshev series expansion to approximate the original function is proposed. Based on Chebyshev inclusion function, the algorithm for solving the nonlinear equations with interval parameters is proposed. Combining the HHT-I3 method, this algorithm is used to calculate the multibody systems dynamic response which is governed by differential algebraic equations (DAEs). A numerical example that is a slider-crank with uncertain parameters is presented, which shows that the novel methodology can control the overestimation effectively and is computationally faster than the scanning method.

Abstract: In order to enhance productivity of the biomass press molding machine, some structure improvement designs are made based on the revolving molding machine. Using the optimization theory to model with the parameters of the improved machine when the input power is constant, the optimization result of the model is obtained using MATLAB software. The results show that producing time of the improved machine can reduce 28% compared with the revolving molding machine.

Abstract: The full flow field numerical simulation of the axial-flow pump model is carried out to predict the pump performance based on RNG k-ε model and SIMPLE algorithm and the method of calculating head and efficiency. The numerical results show that the head and efficiency prediction curves have a good agreement with the experimental results. In the optimal operating condition, the prediction error of head is 0.04% and the efficiency error is 0.39% which could meet the requirements of engineering applications. The prediction error based on RNG k-ε turbulence model is larger in the off-design condition owing to the complex flow field of axial-flow pump. The predicted head is lower than the experimental results in the small flow rate conditions and its maximum error is 5.12%, while is higher than the experimental data in the large flow rate conditions and its maximum error is 17.39%. The conclusions will provide the basis and reference for the performance prediction of axial-flow pumps based on CFD.

Abstract: The performance curves of a submersible axial flow pump were predicted based on mixture multiphase flow model, RNG k-ε turbulence model and SIMPLEC algorithm, and the solid-liquid two-phase flow in the impeller was simulated. The numerical results show that the performance prediction of the head and efficiency curves show good agreement with the experimental data in the whole flow rate range, and the solid particles in the impeller are mainly distributed on pressure side of blades, while less on the suction side.The solid particles are mainly concentrated in the blade inlet and region near the hub of the pressure side. The experimental results also show that the blade pressure sides have serious erosion, particularly near the hub, but less wear and tear on the suction side.The accuracy of the numerical simulation results are verified by the experiments.

Abstract: Concurrent design requires that the following activities of manufacturing and assembly should be considered during the stage of product design. Ship manufacturability evaluation is one of the most important works in concurrent engineering researches. In this paper, the characteristic of shipbuilding is analyzed firstly, and the architecture of knowledge-based manufacturability evaluation system for ship product is presented, and the key technologies to realize the said system are researched.

Abstract: In order to satisfy the flexible rolling schedule of hot steel production, principles and theory for choice of roll contour configuration were described. Additionally, the several typical roll contour configurations which are popular in the world nowadays, and their shape control capability for “rolling of large quantities of strips in same width” and “rolling by strip width increase in sequence” were analyzed with established finite element model of roll stacks. Then, the optimum roll contour configuration for SFR (schedule free rolling) was obtained.

Abstract: The traditional PID control effect is not ideal when the controlled object is nonlinear and contains variable parameters. In order to adapt marine diesel engines to variable working conditions, the fuzzy-PID control method was proposed to be used in the speed control system of marine diesel engine to realize online adjustment of PID parameters. The composition of marine diesel engine speed control system was introduced, and the design of fuzzy–PID controller was analyzed in detail. The fuzzy-PID diesel engine speed governor was simulated through MATLAB. The simulation results show that fuzzy-PID can improve the system dynamic performance, reduce system oscillation and improve the response speed. The results also show that the fuzzy-PID marine diesel engine speed governor has high anti-interference ability and strong robustness.

Abstract: The two gears of the double circular-arc helical gear is a mesh of a concave/convex combination. Because the curvature is close to each other, the strength also increased and thus, it is often used in heavily-loaded workplaces. The national standard for double circular-arc helical gear (ex., GB12759-91) is based on the size of the gear module to design its tooth profile. This shows that tooth geometric-related designs are quite complicated. If the effect of the different pressure angle parameter is considered, we would be unable to conduct relevant studies for the original standard formula with a double circular-arc helical gear set at a pressure angle of 24°. Firstly, this paper would redefine a new double circular-arc helical gear according to the discontinuousness tooth profile molded line of the double circular-arc helical gear and unchangeable pressure angle and explain the improvements in the design and stress analysis of the tooth especially since the double circular-arc helical gear has no limitation in the minimum number of teeth. Thus, the decrease in the driving gears’ number of module and can further increase the reduction gear ratio. For heavily-loaded planetary gear reducer, it’s quite obvious in the miniaturizing and high torque superiority. This paper also used certain winch’s speed reducer as example to explain that the change of the pressure angle can reduce contact stress by 3%~40% and also enhances the torque ability by 3%~40%.