In this study, an ultrasonic technique was applied for the measurement of vertical and axial load acting on implemented hub-bearing having two races, operating under non-rotation condition. Estimation of those loads was performed by the observation of echo height reflected from the interface between an outer ring and a ball. Reflection echo height at upper side of hub-bearing decreases since the supporting load of the ball is increased at upper side, when only vertical load WV is applied to the bearing through the tire. Meanwhile, the echo height at lower side of the bearing is increased up to the same quantity of variation observed at upper side, because the supporting load of the ball at lower side is decreased in contrast to upper side. When only axial load acts to this bearing, the relationship of load and echo height for upper, lower, front and rear sides shows quite opposite behavior for the ball existing at the wheel or body side. From these observed relations, individual estimation of the vertical and axial load becomes possible even if those loads affect to a bearing simultaneously. For instance, in case of the balls in upper side of bearing, the vertical load can be estimated from the averaged value of echo height for two balls locating at upper side, and the axial load can be estimated from the difference between echo height for each balls and average value mentioned above.
This paper presents a robustness analysis of an enhanced adaptive feed-forward cancellation (AFC) function for a control system. The AFC is known as an adaptive control method, and the adaptive algorithm can estimate a periodic disturbance. In a previous study, an enhanced AFC was developed to compensate for non-periodic disturbances. The effectiveness of the enhanced AFC there was shown with only simulation results. In this study, the stable robustness of the enhanced AFC is analyzed for a one degree of freedom system. When the enhanced AFC is implemented to around a resonant frequency, the variations in the mechanical characteristics may cause instabilities in the control system, because the performance of the enhanced AFC depends on the phase condition of the mechanical characteristics. The experimental results show that variations in the resonant frequency may cause oscillation when the enhanced AFC design does not consider this kind of variation. The study confirms that the enhanced AFC must be designed considering variations in the resonant frequency.
The thermoelastic behavior of sheet glass during laser irradiation was clarified using a one-dimensional model. A thermoelastic equation based on an equation of motion with the damping force proportional to the deformation velocity was applied. The thermal and thermoelastic equations were numerically solved by the finite difference method based on an implicit method for the time evolution. A proportional damping coefficient (PDC) was adopted for the calculation. In the case of a stationary heat source, compressive stress on the heated region changed into tensile stress 0.1 s after the end of heating. In the case of a moving heat source, the highest tensile stress was induced when the PDC was less than 0.1. An optimal combination of velocity and the PDC that induced the maximum tensile stress was obtained.
This paper aims to establish the wear mechanisms of tungsten carbide (WC) tools coated with TiAlN and coated with diamond respectively when helical milling Ti-6Al-4V. During the helical milling experiments, cutting forces were measured using a dynamometer. In addition, a scanning electron microscope (SEM), a digital microscope and Energy-dispersive X-ray (EDX) were periodically used to measure the wear progression of tool surface and to analyze tool wear mechanisms. In the analysis of cutting force of two types of coating tools, cutting process of TiAlN-coated tool is more stable and cutting force of it is lower. TiAlN-coated tool showed a better cutting performance than diamond-coated tool. Tool wear mechanisms mainly include adhesive wear, oxidation wear, coating flaking and chipping and are combined effects of various wear forms. In view of flank wear analysis, diamond-coated tool has shorter life than TiAlN-coated tool, and it has undergone a relative severe wear.
To cope with extremely large-scale logistic optimization for strategic planning and real time operational optimizations as well, in this paper, we have proposed an extended algorithm of our hybrid method so that it becomes available for parallel computing. We have also developed a novel algorithm of particle swarm optimization (PSO) associated with binary decision variables. It is quite effective for finding the optimum opening distribution centers in three-echelon logistic network by parallel computing. Eventually, we have implemented the procedure in the parallel algorithm deployed as a multi-population based approach using multi-thread programming technique. Taking two topologies belonging to a coarse grain parallelism, we compared their effects on the performance of the algorithm through large scale logistics optimization. Finally, we confirmed that the proposed method can bring about high performance for the parallel computing that is suitable for the present goal and circumstance through numerical experiments.
A miniature mechanical seal with the cooling water circulating system has been developed as a solution of the shaft seal problems in rotary blood pumps. The present paper describes the effect of the surface roughness in the sealing gap on the shaft seal problems under blood sealing. The sealing surface roughness of tested three seat rings were designed to be Ra=0.009, 0.088 and 0.170µm. The frictional loss torque in the sealing gap and the leakage of the blood and the cooling water were measured in this work. Results show that the maximum frictional loss torque measured in the seat ring of Ra=0.009µm, and the frictional loss torque decreased as the surface roughness increased. The leakage rate of the cooling water is larger than that of the blood in all seat rings, even though the blood chamber has higher pressure. The sealing characteristics between under the blood and water sealing were different. Moreover, the best surface roughness in the torque and the leakage characteristics were also different. Thus, it is important to study under blood sealing in the design of the surface roughness of the mechanical seals for rotary blood pumps.
Spherical mechanisms are widely used in engineering applications. Minimizing their motion error is critical for high performance of such mechanisms. The motion error is significantly affected by uncertainties in spherical mechanisms. The impact of the uncertainties on the motion error, however, is rarely considered in mechanism analysis and synthesis. In this work, we quantify the effects of randomness in the major mechanism dimension variables on the motion error through kinematic reliability with a probabilistic approach. Two types of reliability, the point kinematic reliability and the interval kinematic reliability, are discussed. For the former the First Order Second Moment (FOSM) method is employed while for the latter a multiple-extreme-value method is proposed to maintain high accuracy. The Monte Carlo simulation (MCS) is performed as a benchmark for the accuracy comparison. The effectiveness of the proposed method is demonstrated with two examples.
This paper details the architecture, hardware and software of a platform for testing electric motors over the Internet that enables users to test multiple physical motors remotely under the specific loading conditions of the real-world application for which a motor is required. The system is divided into three major modules: the Server Software Application, the Target Software Application and the Motor Test Platform. The system is unique as it combines modularity, scalability and deliverability. It is modular, as it is capable of readily testing a variety of electric motors, scalable, as new motors can be quickly added to the system for testing, and is turn-key, easily deployed and installed. The proof-of-concept prototype was developed and examined against benchmark tests to determine its capabilities. The platform was effective as a remote access emulation and evaluation tool.
Selective Laser Sintering/Selective Laser Melting (SLS/SLM) is one of the most promising additive manufacturing (AM) techniques that are widely accepted by the industrial community. This is due to its high flexibility in processing different types of material under various conditions. However, the capability of the end product to have a desirable quality comparable to traditional processing techniques is still not achievable. Consolidation characteristics and the influence of processing parameters are important in determining the SLS/SLM part quality. In this paper, the consolidation process of ferrous-based metal powder is examined by monitoring the real-time consolidation process. A high-speed camera was utilized with telescopic lenses in order to monitor the interaction of laser and material within the powder fusion zone (PFZ). Based on the study, the line consolidation can be classified into five different consolidation types. The line consolidation characteristics were analyzed according to the line consolidation width, PFZ, consolidated agglomerate diameter and metal particle splattering behavior. The influence of laser power and scan speed on these characteristics was analyzed. It was also found that the line consolidation width, PFZ, consolidated agglomerate diameter and splattering were increasing with the increase of laser power. In contrast, with the increase of scan speed the result was vice versa. These phenomena can be explained with respect to the heat transfer behavior that took place during the interaction between the laser beam, metal powder and substrate surface. The consolidation mechanism that occurred during consolidation is also reported.