A forklift truck is one of the most important tools in ports, stations, factories, and warehouses. The steering wheel of such a truck is the main contact part between the driver and the truck, and the vibration intensity of this part directly determines the operating comfort of the driver. This paper mainly aims to analyze and optimize steering wheel idle vibration. Experiments are implemented on a group of faulty forklifts to investigate the performance trends and the root causes of the vibration problem. The Hilbert-Huang transform method is used to analyze steering wheel vibration features of faulty forklift trucks at idle. Along with simulation, we learn that resonance vibrations is the main reason that causes the excessive vibration at idle. Thus, we propose an optimization scheme that separates the support plate (referred as part A) from the brake pedal mounting plate (referred as part B) and increases the thickness of the front plate to restrain idle vibration. The results obtained from simulation and comparative experiments indicate that the proposed schemes can effectively suppress the idle vibration of the steering system.
The thin liquid film entrained by a continuous immersed solid pulled through a tank is of the main interest in many industrial processes. In order to appraise the state of art, it has been reviewed the experimental and theoretical studies of a solid being withdrawn horizontally from a tank. This review has revealed that the open literature is scarce. The main objective of this paper is to study the above stated problem. To this end, it has been performed a series of experiences of horizontal withdrawal of wires from a tank of water, and an approximate theoretical model has been developed.
Twin-screw kneader is an efficient polymer processing equipment. The mixing performance is a very important index for the twin-screw kneader. In this paper, the mixing performance of one novel intermeshing counter-rotating twin-screw kneader with different tip angles of the male rotor was simulated using the mesh superimposition technique (MST). Statistical analysis was carried out for the flow field using particle tracking technique, and distributive mixing performance is evaluated using the residence time distribution and segregation scale, while the dispersive mixing performance is estimated using the average of the maximum shear rate and stretching rate as well as the mixing index. The results show that the best distributive mixing performance is achieved when the tip angle is 0°, while the optimal dispersive mixing performance is obtained when the tip angle is 20°. One experimental apparatus of the twin-screw kneader is built up to perform the mixing performance using three color masterbatch materials with the screw rotors. The results in this paper provide a data basis for the selection of parameters and optimization of the mixing performance for the differential twin-screw kneader.
We investigated the effect of magnesium carbonate and rosin powders, conventionally used as anti-slip agents, for the ease of controlling the sliding motion of a stainless steel bar grasped vertically by a hand wearing a rubber glove. Fifteen participants were instructed to slide the stainless steel bar downward with their dominant hand and control the sliding speed to be constant by controlling their grip force, and stop the bar 0.2 m from the starting point within 5.0 s. Sliding control tests were conducted under six conditions of the interface between gloved-hand and the bar: dry without powder, dry with MgCO3 powder, dry with rosin powder, wet without powder, wet with MgCO3 powder, and wet with rosin powder. The bar sliding motion was captured and the time of arrival, total sliding distance of the bar, and standard deviation of the sliding velocity of the bar were calculated. The friction force between sliding bar and gloved-hand was estimated from the bar sliding motion. The controllability of the sliding motion of the bar was evaluated by sensory assessment. The sliding control test indicated that both powders reduced the variation in sliding velocity of the grasped bar and improved the controllability of its sliding motion compared with unpowdered dry and wet conditions. Powder application also decreased variation in the friction force between the rubber-gloved hand and the grasped bar during sliding under dry and wet conditions. These results suggest that both powders stabilize friction, thereby improving the sliding control of a grasped bar.
Colloidal silica slurry has been widely used in mirror finishing of various microelectronic materials, including Si wafer. However, in the last decade, there has been a tendency to replace the polishing slurry with fixed-abrasive pads because of environmental issues related to the use of slurry and poor finishing surface shape accuracy. Unfortunately, the fixed-abrasive pad is still unsatisfactory for both material removal rate and finishing surface quality. Therefore, various silica abrasives added into fixed-silica pads for polishing Si wafer were investigated in this study. Both loose and fixed abrasive polishing experiments were performed. Instead of conventional nanosilica abrasive, the micron spherical particle aggregated by nanosilica (hereafter, aggregate silica) was proposed as an abrasive of fixed-silica pad, and were compared with micron natural crystal silica abrasive and micron spherical fused silica particle. Experimental results demonstrated that the nano-aggregating structure of aggregate silica with a mean diameter of about 5um has approximately 100 times higher specific surface area than the natural and fused silica abrasive, and can easily absorb more [-OH] onto the aggregate silica surface, which is approximately 5 times when each of them is added to the alkaline aqueous solution at pH 12. Thus, a strong chemical removal effect was observed. This condition caused not only higher material removal rate but also better finishing surface roughness, which can be comparable to that of colloidal silica slurry with 10 nm to 20 nm particle size (5 wt%, pH 10.5). The chemical removal effect can also be enhanced by increasing nanopore volume of aggregate silica.
This study focuses on acoustic silencers on indoor-use doors positioned in an array. In this paper, we discuss our studies of side branch silencers which are built in the ventilation door. By designing and fabricating a special attachment, we were able to attach silencers to the measurement tube that had larger cross sections than the impedance measurement tube. Using this attachment, we measured acoustic transmission losses for each of six different prototype silencers. By adding orifice silencer effects, we obtained transmission losses across a wide frequency range. However, attenuation decreased in frequency ranges below the attenuation peak of the side branch tubes. A wedge-shaped longitudinal cross section for the side branch tubes can double the length of the silencer and develop lower-frequency attenuation effects, while maintaining the same volume. This wedge-shaped side branch tube is suitable for a long silencer placed side by side in an array formation. We performed theoretical analyses of acoustic transmission losses of silencers using the transfer matrix method based on a one-dimensional wave equation. We performed element decomposition on the transfer matrix for silencers with side branch tubes with a wedge-shaped longitudinal cross section. We obtained calculated results that were sufficiently valid compared to our experimental measurements.
Using W6Mo5Cr4V2 HSS (High-speed steel) as a sample material, effects of cryogenic treatment on residual surface stress of ground W6Mo5Cr4V2 HSS specimens were investigated. The residual stress in the ground surface and its change caused by cryogenic treatment were analyzed using both X-ray diffraction technique and finite element method. It was demonstrated that the cryogenic treatment reduced the equivalent stress Max Mises from 248.9 MPa to 114.3 MPa, and the principal stress reduced from 124.0 MPa to 91.6 MPa. The residual stress at X direction (S11) parallel to the grinding direction was tensile stress, which was reduced from the Max. 105.8 MPa to 63.48 MPa. However, the residual stress (S22) perpendicular to the grinding direction was compressive stress, which was slightly increased from 272.6 MPa to 287.8 MPa by the cryogenic treatment. The changes in both the tensile and compressive residual stress components are beneficial to material performance, e.g., wear resistance. Results from the computational and experimental analyses are consistent.
Smart manufacturing considered as a new trend of modern manufacturing helps to satisfy objectives associated with the productivity, quality, cost and competiveness. The smart manufacturing system is characterized by decentralized, distributed, networked compositions of autonomous systems. The model of smart manufacturing is inherited from the organization of the living systems in biology and nature such as ant colony, school of fish, bee's foraging behaviors, and so on. In which, the resources of the manufacturing system are considered as biological organisms, which are autonomous entities so that the manufacturing system has the advanced characteristics inspired from biology such as self-adaptation, self-diagnosis, and self-healing. In this paper, a cloud based smart manufacturing system for machining transmission cases is considered as research object in which the advanced information and communication technology such as cognitive agent, swarm intelligence, and cloud computing are used to integrate, organize and allocate the machining resources.
This paper considers the pressure control of air springs used for a pneumatic anti-vibration apparatus (AVA), which isolates vibration transmitted to semiconductor lithography equipment. In the control of the pneumatic AVA, pressure feedback is often employed so as to keep the inner pressure of air springs constant. By expanding the bandwidth of pressure control system, fast response can be obtained, though this bandwidth is restricted due to anti-resonance and resonance in a pneumatic system. To eliminate the anti-resonance and resonance, relative displacement derivative (RDD) positive feedback control has been presented. However, previous RDD positive feedback control cannot be implemented under the condition where the dead time of air springs exists. In order to compensate effects of the dead time, a Smith predictor is utilized. Through experiments, it is shown that in the presence of the dead time, the anti-resonance and resonance can be eliminated by means of the RDD positive feedback control combined with Smith prediction. The bandwidth of the pressure control system increases with the gain of pressure PI compensator. Furthermore, effects of proposed approach on vibration transmissibility are investigated. Although the vibration transmissibility is the performance metric for the development of the pneumatic AVA, the case where the dead time is present was not sufficiently considered. In this paper, it is shown that the vibration transmissibility changes in accordance with the dead time.
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