Advanced Materials Research Vols. 228-229

Abstract: When the hybrid hydraulic excavator worked in a low load and high battery SOC value state, the maintenance of the engine working would cause unnecessary loss during energy conversion, therefore it was required to shut down the engine at this moment. Then a fuzzy logical control algorithm based on the engine on/off state switch was proposed for the hybrid hydraulic excavator. By comprehensively evaluated the current external load level, value of battery SOC and the duration of engine former state, the engine on-off state switch rules and trigger condition were established, also, parallel or pure electric driver system patterns was formed. By using MATLAB/Simulink to establish a dynamic mathematical model, the power system control performance and fuel consumption were analyzed after the application of the algorithm. The results showed that the fuzzy logic control algorithm had strong applicability for the external load changes, and the engine on/off state switch could reduce the redundancy of the energy conversion process, the machine fuel consumption when the excavator is in a low-load condition with high battery SOC.

Abstract: With the development of aviation and aerospace industry, the performance requirement and part accuracy requirement of aviation engines are increasingly enhanced, and it is difficult to ensure machining accuracy and usage requirement by traditional machining technique. Therefore, the cutting performance and cutting parameter of aviation engine thin-walled parts are researched. Based on FEM (Finite Element Method), simulate cutting of titanium alloy thin-walled parts and analyze the cutting process of a three dimensional model under different cutting parameters so as to obtain the rules of the residual stress and deformation of titanium alloy thin-walled parts. The method referred to in this paper can be used to select the machining parameters of real aero-engine thin-walled, which is helpful to control deformation of workpiece and increase the machining efficiency.

Abstract: Isotropic pyrolyric graphite (IPG) is a new kind of brittle material, it not only has the general advantages of ordinal carbonaceous materials such as high temperature resistance, lubrication and abrasion resistance, but also has the advantages of impermeability and machinability that carbon/carbon composite doesn’t have. So it can be used for sealing the aeronautics and astronautics engines turbine shaft and the ethylene high-temperature equipment. The mechanism of this material removal during the precision cutting was analyzed by using the theory of strain gradient. The critical cutting thickness of IPG was calculated for the first time. Furthermore, the cutting process parameters such as cutting depth and feed rate which corresponding to the scale of brittle-ductile transition deformation of IPG was calculated. The prediction model of surface roughness in precision cutting of IPG was developed based on the Genetic algorithm. Using the surface roughness prediction model, the study investigates the influence of the cutting speed, the feed rate and the cutting depth on surface roughness in precision turning process was researched.

Abstract: This paper revisits the problem of stability analysis for discrete-time stochastic neural networks (DSNNs) with mixed time-varying delays in the state. Here the mixed time delays are assumed to be discrete and distributed time delays and the uncertainties are assumed to be time varying norm bounded parameter uncertainties. A new delay-dependent stability criterion is presented by constructing a novel Lyapunov-Krasovskii functional and utilizing the delay partitioning idea and free-weighting matrix approach, Which is less conservative than the existing ones. This criterion can be developed in the frame of convex optimization problems and then solved via standard numerical software. These conditions are formulated in the forms of linear matrix inequalities, which feasibility can be easily checked by using Matlab LMI Toolbox.

Abstract: In this paper, we analyze the stresses around the saw teeth of differently designed circular saw structures. We select a set of critical points around the saw tooth, then we calculate the equivalent stresses of these points and the maximum or minimum stresses of the different saws under different loads and rotational speeds. The saw structure factors that we examine include the diameter of circular saw blades, the depth of the circular saw, the saw tooth rake angel, the saw tooth height and the saw tooth shape. Based on our analytical results, we propose an effective approach to reduce the stress concentration around the saw tooth and thus prevent the saw tooth fracture.

Abstract: We investigate the natural frequency and the amplitude of circular saw blades during idling. We use four blades in the paper: 1) The traditional circular saw blades, 2) The circular saw blade with damping materials which is distributed in the core of blade, and the circular saw blade has a uniform thickness, 3) Similar to the above one but the circular saw blade has a non-uniform thickness, the damping region is thicker than other region of the circular blade, 4) the circular saw blade with damping material which is distributed around the core of blade by four small circular regions. We adopt the Finite Element Method in our numerical analysis. Our analytical results are very useful for a better design of circular saw blades.

Abstract: Thinner saw blades cannot resist large lateral cutting forces due to their lower stiffness. In this paper we propose a composite reinforcement method to improve the mechanical properties of circular saw blades. We analyze and simulate the stress and strain fields of our proposed reinforced circular saws by Finite element method. Our analytical results contain not only influences of reinforcing parameters but also loading conditions on the lateral stiffness and the natural frequency of composite saw blades. Here the reinforcing parameters include: 1) the reinforcement location on circular saw blades, 2) the volume fraction of the reinforcements, 3) the number of the reinforcements; and loading conditions include: 1) the cutting force, 2) the rotational speed. Our composite reinforcement model and simulation results can contribute to a better design of circular saw blades.

Abstract: The porous metal fiber sintered felt (PMFSF), a new catalyst support, was successfully used to construct a methanol steam reforming microreactor for hydrogen production. To study the transport characteristics of PMFSFs, a three-dimensional model with the cubic pore cell structure for PMFSFs was established. Using computational fluid dynamics fluent software, the velocity and pressure distribution when the fluid through the PMFSFs was investigated by changing the porosity of PMFSFs and inlet velocity of the fluid. In addition, fluid temperature distribution was analyzed under different inlet velocities by setting the temperature of fluid and wall. The result shows that the PMFSFs greatly enhance the transport characteristics because of its three-dimensional network structure and microchannel structure, it will become an ideal candidate for catalyst support material.

Abstract: A series of Iron-based complex catalyst were prepared by precipitation and immersion in order to study the effect of Ruthenium on the performance of Iron-based catalyst for CO hydrogenation in FTS. The distribution of products was studied for CO hydrogenation, and the reduction action of Iron-ruthenium complex catalyst was study by TPR. The results showed that the yield of the lower hydrocarbons in the products of CO-hydrogenation could be improved obviously with Ruthenium added, and the reduction action of Iron-based catalyst could be promoted obviously.

Abstract: The experiments of thermal shock damage on piston were conducted by shaped high power laser. Damage mechanism of thermal shock specimen was characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The mechanical properties of thermal shock specimen were evaluated by microhardness. The corresponding mechanisms were discussed in detail. The results show that cracks originated from the interface of Al-matrix and intermetallic phase due to the thermal and mechanical misfit between these brittle components of the microstructure and the surrounding ductile matrix. Oxides of thermal shock crack can accelerate the damage of piston. There is a drop in the hardness of piston at all locations after thermal shock tests.