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 In order to appraise the state of art, it has been reviewed the experimental and theoretical studies of a solid being withdrawn horizontally from a tank.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.
An innovative transmission mechanism, referred to here as an independently controllable transmission (ICT), for application in variable speed wind turbines is described. This ICT mechanism can transmit rotational output speed that can be independently regulated by a controller and is not affected by the speed of the input shaft. Use of this ICT mechanism would make it possible for a variable speed wind turbine to be unaffected by rotor speed fluctuations and allow the generation of constant frequency electrical output of improved quality. The ICT mechanism is comprised of two planetary gear trains and two transmission-connecting members. The kinematic, static characteristics, and power flow of the ICT mechanism have been analyzed and derived as analytical equations. Demonstration examples and a prototype of the device have been built and tested to examine their kinematic and static characteristics and to verify the validity of the results.
A compact absorptiometer for water quality testing that does not need a special technique to take measurements was studied where the absorbance of a sample solution could be stably measured without decreasing the sensitivity over time. Three types of devices were developed, namely, horizontal straight-line type, vertical straight-line type, and multiple reflection type, that consisted of a light emitting diode (LED), a photodiode (PD), and a glass capillary used as a sample cell. The results from our experiments conducted to detect the nitrite nitrogen in water, which is a factor in water pollution, were used to evaluate how these three devices perform. The shapes of the liquid surfaces at the end of the capillaries in the horizontal and vertical straight-line types, which had the LED, PD, and the glass capillary in line horizontally and vertically, respectively, significantly influenced the output voltage of the PD and this output significantly changed over time, so it was difficult to precisely measure the absorbance. The change in the shape of the liquid surface at the end of the capillary was particularly considerable in the horizontal straight-line type. On the other hand, in the multiple reflection type, which had reflective plates surrounding the glass capillary, the absorbance was measured quite stably because the light emitted by the LED did not transmit through the liquid surface at the end of the capillary and the output voltage of the PD was uninfluenced by the change in the shape of the liquid surface. Additionally, controlling the sensitivity of the absorbance was possible by adjusting the length of the reflective plates, i.e., adjusting the light path. The sample solution in this device did not come into direct contact with the reflective plate, so the device can suppress the decrease in the sensitivity caused by materials becoming directly attached to the reflection plate. The compact multiple reflection type device that was developed could be used in a manually operated portable absorptiometer and also in an automated water quality analysis system that incorporates mixing and flow devices.
Multi-tasking machine is capable of performing both milling and turning operations, it contributes to highly efficient machining and space conservation. However, prior to machining a lot of lead time is consumed in deciding efficient process plan, and generating machining tool path. Although the current CAM systems are highly integrated, the efficiency of the generated tool path is highly relied on the experience of the CAM programmer. In this research, an automatic process planning system for multi-tasking machine was developed. It is capable of recognizing manufacturing features and deciding efficient process plan from CAD model automatically. In this developed system, the CAD model is described as Attributed Adjacency Graph (AAG), and each feature is defined by AAG and its geometrical properties. Totally 8 milling features and 9 turning features can be recognized. The optimal machining plan is calculated based on machining cost evaluation. In addition, in this research a new method based on subfeature combination is proposed in order to recognize intersecting features. Furthermore, in this research the connection relationship of each feature is classified, and machining priority is assigned to adjacent features. It prevents the time consuming evaluation for checking all possible machining sequences. Finally, according to the experiment results, it is confirmed this developed system is capable of obtaining optimal machining plan properly and rapidly.
The effectiveness of the novel micro textured tools developed as an attempt to improve the machinability of Ti6Al4V material is studied. Different types of textures were developed on the rake face of the tools and subsequently coated with a solid lubricant (tungsten disulfide). Square and circular textures are developed for the first time. The textured and coated tools were used for machining Ti6Al4V. Adhesion of the material to the rake face of the tools is observed to be decreased considerably although not eliminated completely. Maximum reduction in the main cutting force was 60% for the square textured tools. Friction at the rake face of the tool is reduced considerably which results in the improvement of tool life. The change in adhesion behaviour and the observed reduction in cutting forces are attributed to the reduction in chip-tool contact area owing to the surface texture on the tool inserts. Further, these textures are acting as reservoirs of solid lubricant. Chip morphology is also found to be favourably altered through the reduction in the segmentation frequency (about 40% for square textured tools and 27% for linear textured tools).
The sit-to-stand (STS) movement is performed throughout the day, and providing handrails is one method of making the STS movement easy. However, designers may have determined the installation position of handrails using intuition and trial and error. The aim of this study is to determine the optimum position and orientation of handrails by minimizing the quantified physical load of the STS movement. Twelve university students participated, and eight electromyograms (EMGs), namely, of the brachioradialis, flexor carpi ulnaris, extensor carpi radialis longus, latissimus dorsi, right and left rectus femoris, and right and left tibialis anterior, were recorded. Observations with handrails at various tilt angles and forward distances from the edge of the seat were analyzed for the optimization. The total physical load (TPL) function was formulated as the weighted sum of the EMGs. The weight coefficients were determined by maximizing the correlation coefficient between the measured subjective scores and the TPL function values. The result shows that the handrail installation position significantly affects all of the EMGs except those of the right and left rectus femoris. The weight coefficients of the TPL function are positive for the upper limb muscles, whereas they are zero for the lower limb muscles. The handrail position for multiple users was formulated to minimize the TPL function, and hence the optimum position was determined.
This paper introduces novel approaches for analysis of the double wishbone suspension mechanism. In the literature, to the best of our knowledge there is no analysis study available for the double wishbone mechanism that is performed “analytically”. Initially kinematic model of the double wishbone mechanism is established. Then, a kinematic analysis methodology is presented. This analysis procedure is carried out analytically. The essential parameters; camber, caster, kingpin, toe angles, and track variation are defined according to the kinematic model. A double wishbone suspension mechanism is synthesized as an example by using the method presented in this study. Variations of the essential parameters with respect to wheel travel are plotted. The synthesized mechanism is established both in Lotus Suspension Analysis and Catia software and same results with the analytical model are obtained. Thus, it is verified that mechanisms of different dimensions can be analyzed and parameters can be optimized precisely and swiftly by using this analytical approach.
The Pre-stressed Hardening Grinding (PSHG) is presented combining with the advantages of Pre-stressed Grinding and Grinding Hardening. In order to study the variation mechanism of metallographic structure and the residual stress within hardening layer under PSHG, the paper took 45 steel as the experimental object and carried on the PSHG experiment. The surface hardening layer with little residual stress was obtained from it. The surface hardness, the wear loss and residual stress were measured and its metallographic structure was observed. Combined with experimental result and the simulation of grinding temperature field, the paper studied the mechanism which the pre-stress influences the metallographic structure and the residual stress. The study shows that parent-phase-hardening and strain-inducing-phase-changing due to applying pre-stress have comprehensive effect on the martensitic phase transformation in the grinding process. And its result indicates that the pre-stress restrains the phase transformation with grinding hardening layer firstly and then promotes it. And then pre-stress affects the residual stress mainly through affecting phase transformation in the typical PSHG. It has the same variation as phase transformation with the increasing of pre-stress in the process.
In this paper, we propose a louver with a simple structure and a high aperture ratio. A louver element with a sound attenuating structure composed of layered two flat rectangular tubes, each of which is wedge-shaped with thickness decreasing toward the closed end, was constructed and experimentally and theoretically analyzed. Samples having more basic structures were also constructed and compared. In the theoretical analysis, the sound attenuation characteristics of a louver element were clarified considering sound attenuation in the clearance between two planes, as is typically observed in the flat rectangular tubes furnished in the louver element. To consider the sound attenuation due to the viscosity of the air in the rectangular tube, the propagation constant and characteristic acoustic impedance were derived using the Navier-Stokes equations, etc. Further, the sound transmission loss was calculated by the transfer matrix method. The tendency of the theoretical values in consideration of the attenuation of sound wave roughly agreed with the experimental values. Note that the attenuation of sound wave is evident in a thin or wedge-shaped tube and has to be considered in the theoretical analysis. The number of flat rectangular tubes was doubled without increasing the thickness of a louver element. The structure is useful as a louver slat because sound attenuation is achieved in a wide frequency range while maintaining a high aperture ratio.
There are engineering benefits if we can predict the acoustic properties such as the sound absorption coefficient of a sound incident on the clearance of such an annular cross-section based on the geometric dimensions of the tubes and the physical properties of the gas. However, a successful theory for the sound absorption coefficient of narrow tubes of the abovementioned shapes has not yet been presented, and the comparison between experimental and theoretical values has not been made. Further, the propagation constant and characteristic impedance in the clearance in a double cylinder have not yet been derived in the cylindrical coordinate system or by other methods. Therefore, in this paper, the propagation constant and characteristic impedance were derived by approximating clearance of an annular cross-section with clearance between two parallel planes. And the sound absorption coefficient was calculated, then compared with experimental results. The theoretical values, according to this method, agreed well with the experimental values, and practically sufficient accuracy was obtained. It was experimentally confirmed that the eccentricity of a round bar in a circular hole does not appreciably influence the sound absorption coefficient. Even when this calculation method is applied to a circular hole, the results agree with the theoretical and experimental values for the circular hole. Therefore, this method is effective even if the diameter of the internal cylinder is considerably smaller than that of the external cylinder.
The purpose of this paper is to achieve machining equal base circle bevel gears with a pot-shaped gear cutter. Based on the theory, the feasibility is analyzed, the coordinate systems of cutting, on both convex and concave surfaces, are established, and the mutual transformation matrices of these cutting coordinate systems are obtained. With the pot-shaped cutter coordinate system, the unit tangential vector and normal vector of the curved surface are calculated. Then, the tool surface point velocity vector under the fixed coordinate system is worked out through solving the instantaneous angular velocity of the points on the wheel billet and vector of the cutter curved surface. Finally, after establishing and solving of the meshing equations on the conjugate contact point between the cutter curved surface and tooth surface, the target machining expression is presented. The three dimensional tooth surface is modeled by Matlab, solving the contact line family at different locations on the cutter, and then comparison between the resulted tooth surface and the theoretical one is conducted. The tooth cutting experiment verified the feasibility of the proposed machining processes, which may lay a solid foundation for the industrial application of this new method.