Twin wires submerged arc welding technology is an efficient way for the high-speed welding of heavy workpiece of the low carbon steel. A novel inverter twin wires high effect submerged arc welding equipment is proposed by combination of the inverter welding power source of direct current (DC)1250A and alternate current (AC) square wave 1000A, digital cooperative control and process monitoring technology. Digital cooperative control system are designed by combination of the a computer, TCP/IP based data collection and monitoring module, twin wires submerged arc welding control box and sensor detection system. The TCP/IP based data acquisition and monitoring module consist of Advanced RISC Machines (ARM) controller, A/D module, D/A module, network interface and digital I/O ports. The results of welding experiment demonstrate that the novel developed twin wires submerged arc welding equipment meets the designed requirements with strong adaptability, which achieves the functions of parameters optimization settings, digital timing control of the twin arcs, and real-time monitoring of the welding process. The proposed equipment has good application prospect in twin wires submerged arc welding of steel plate at high welding speed more than 100cm/min due to the strong adaptability in welding process.
In this paper, dynamic reliability models of series mechanical systems in terms of stress parameters and strength parameters are established, in which strength degradation path dependence (SDPD) and failure dependence of components in the system are taken into consideration. Despite the computational convenience for reliability evaluation by using the independent strength distribution at each load application, large errors could be caused due to neglecting the existence of SDPD. In this paper, influences of SDPD on both dynamic system reliability and failure dependence are investigated. Moreover, the impacts of the dispersion of initial strength and the number of components in a system on the influences of SDPD on dynamic system reliability are analyzed. In addition, the clamp band joint system is used as illustrative examples to demonstrate the proposed models. The results show that SDPD have considerable influences, which vary in different operational stage of series mechanical systems, on dynamic system reliability and failure dependence. Besides, the dispersion of initial strength and the number of components have different impacts on the effects of SDPD on system reliability.
The rolling bearing carries a load by placing rolling elements between two bearing rings. It is a key device in the railway vehicles for monitoring work states to ensure high reliability and better performance of rotating machine. The states of rolling bearings can be detected by the measurement of vibration signals with effective process, features extraction and analysis. The propose of this paper is to establish an efficient and robust signal processing technique and classification mechanism to detect the fault of rolling bearing. Firstly Fast Fourier Transform is used to extract features and then these parameters are input into various classification schemes for accurate fault detection. Ensemble Rapid Centroid Estimation is proposed and then compared with Artificial Neural Network, and Principal Components Analysis. The simulation analyses the approaches of fault detection and the accuracy of identification. Then the linear performance of the data is proved by least square regularized regression. Finally various schemes are compared and analyzed to obtained the most efficient method for fault detection.
In the helical milling process, a rotating tool traverses a helical trajectory to generate a hole. In order to investigate the cutting state in helical milling of carbon fiber reinforced polymer(CFRP), experiments were conducted with unidirectional and multidirectional laminates. Cutting forces, tool wear state and hole quality were discussed respectively. The effect of cutting parameters on the cutting forces was first presented, then the influence of different workpiece material on the cutting forces was secondly analyzed. Because of higher abrasion of carbon fiber, tool wear was a major problem without being ignored in the cutting process, so the study on the tool wear state was carried out from the point of wear process, wear form, coated state and change of element etc. Therefore the effect of tool wear on the cutting forces was detailedly analyzed. Next the relation between tool wear and entry delamination of hole-making was discussed. Finally, inner delamination, delamination factor, diameter error, surface roughness and circularity error were also investigated in detail.
Multi-layer protuberant foil bearings uses multi-layers of protuberant foils as the elastic support structure to support the smooth top foil. A numerical model with a computational method is developed in this paper to predict the characteristics of the multi-layer protuberant foil bearing. According to this model, the deflection of each foil has been calculated separately with the consideration of the interactions between contacting layers of foils, and the profile of foil deflections, film pressure and film thickness also have been computed. The results show that these profiles of multi-layer protuberant foil bearings are very different from those of bump foil bearings. And the flexibility of the multi-layer protuberant foil bearing is improved as the layer number of protuberant foils increases. Moreover, the effects of the bearing number and the eccentricity on the static and dynamic characteristics of multi-layer protuberant foil bearings have been analyzed. It is found that the bearing always operates with a small attitude angle when the bearing number is large. In addition, the bearing has quite different dynamic characteristics when operating at the critical condition from those at the synchronous condition, which suggests that dynamic computation at the both conditions is required for dynamic analysis of the foil bearing.
Product appearance has become a more important influence on customers' preference in regards to product purchase. Not only do customers take into account functionality and cost, but also on aesthetic and affection value. Kansei engineering (KE) utilizes a product design methodology which translates a customers' perception regarding feeling and emotion on appearance of a product into a product's design parameters. This study applied KE methodology to determine customer emotion on the shape of wine glasses and the optimal precise design parameters to obtain customer satisfaction. This study was performed using a four-factor and three-level Box-Behnken design under response surface methodology (RSM). The data obtained from the experiments were analyzed by analysis of variance. Furthermore, the data was fitted to a second-order polynomial equation using multiple regression analysis. The effects of four parameters of wine glass, namely the rim's width (A), the bowl's width (B), the bowl's height (C) and the stem's height (D) on the surface potential of five Kansei words, namely modern, quality, durable, ease of drinking and ease of handle were examined. The optimal model of wine glass design was controlled at A=90 mm, B=61.82 mm, C=126.67 mm and D=61.97 mm, respectively. The results of RSM indicate that the proposed shape design models can interpret all of customers' emotion about a product which in this case is a wine glass. Finally, this study provides useful understanding for shape parameter design and this method can be applied to a variety of design cases.
This study presents a new approach, group inching fortification (GIF) method, to deal with multiobjective optimization problems found in various mechanical designs. The GIF method is exemplified by a four-factor porous air bearing design. In the GIF method the initial group of designs in Pareto rank 1 is used as the basis to inch up the formation of Pareto solution set, which is fortified over the search process by uniting superior or non-dominated solutions from base-point exploration moves. In this study, a comparison of the GIF method with genetic algorithm (GA) and hyper-cube dividing method (HDM) for the same air bearing design is presented. The results show that the Pareto solution set obtained by the GIF method has more design selections with a wider coverage (breadth). Equally important, the number of objective-function calls required (179, 736, and 3600 for GIF, HDM, and GA, respectively) in the GIF method is significantly reduced. In this study, the GIF method is suggested to be terminated when all the designs are non-dominated by each other, a criterion which is very difficult to achieve by using the GA and HDM. This study proposes an effective design tool which is easy-to-implement for solving the problems with multiple objectives.
Among the key factors that comprise vacuum glazing panels, pillars are an essential element deposited to maintain the internal vacuum gap against external forces. Deposited pillars may cause cone cracks in glass according to the contact area with glass so pillars have a shape to prevent such crack. Method of depositing pillars include the screen printing method, which is widely used in forming high precision micro-patterns in fields of flat display such as LCD, PDP and organic EL. In this paper, we presented a trapezoidal cross section pillar manufacturing model that can prevent cone crack in screen printing. This paper actually examined relations between screen printing process conditions and cross section shape using the Taguchi method and analysis of variance(ANOVA), and presented process conditions through which trapezoidal cross section shape can be manufactured. Also, We finally obtained formula about the relationships based on process parameters to prevent cone crack on contact area glass and pillar, and found the optimal value of the parameters.
We conducted a study related to sound absorbing materials created by folding thin material in the shape of a Japanese folding fan. In order to conduct a calculation of the shape of a clearance in the folding fan-shaped test sample, we performed an approximation of element decomposition in both the incidence direction of the sound wave and the lateral direction. In a theoretical analysis, we considered sound wave attenuation due to boundary layer friction in the clearance between two surfaces. We compared experimental and calculated values for the sound absorption coefficient. Trends in both matched closely. Errors in the calculated values for large clearances could be attributed mainly to irregularity in the size of the clearances. Frequency shift of the calculated values for small clearances were due to errors in estimating the sound attenuation. Sound absorbing structures shaped like a folding fan possess sound absorption characteristics are similar to the wedge-shaped sound absorbing structures shown in previous reports. This was also shown in calculated values based on theoretical analysis. In cases with an appropriate back air space, sound absorption peak frequencies decreased relative to cases without a back air space, and sound absorption characteristics were superior across a wide frequency range.
Against global warming and environmental degradation, it is essential for modern logistics to make sincere efforts to resolve such environmental issues. However, that will likely degrade the economical efficiency under global competition. In fact, since it seems almost impossible to derive a reasonable solution individually, we need to face with the problem as whole society. Deployment of a green logistics incorporated with community-based action is a new paradigm realizing an infrastructure aligned with sustainable development. Noticing importance of such idea, this study concern a green logistics optimization associated with production methods of manufacturers and green attitude of consumers. Actually, for a three-echelon logistics network, we have developed a novel hierarchical method to optimize the production methods with different structures regarding cost and emission of carbon dioxide (CO2) at production sites, the available collection center, the paths between members of the logistics network and circular routes over consumers. In this problem, first we aim at minimizing either total cost or CO2 emission through controlling prone and aversion behaviors on sustainability of each logistic member. Then, to integrate these individual problems and evaluate them on the same basis, we have introduced an economic mechanism known as emission trading rate on CO2. Moreover, to discuss the sustainability in a broader logistics system, we note the modal shift in transportation. To show the significance of the proposed approach, we provide a case study and explore some prospects for community-based green logistics.
This paper proposes a normalized-constrained approach for the joint clearance design of deployable overconstrained Myard 5R mechanism. Firstly, the overconstrained mobility characteristic of Myard 5R mechanism is analyzed, we show that the dimensional requirements are critical for this mechanisms such that the joint clearance is necessary and inevitable in the design process. Secondary, the normalized-constrained model of Myard mechanism without changing its deployable ability is proposed by attaching two revolute joints along the two short links of the original Myard mechanism, we show that this normalized-constrained mechanism is still deployable/foldable to the appropriate deployed/folded configurations under some possible dimensional errors. Thirdly, the clearance model for revolute joint is created, then we can calculate the optimized joint clearance based on the motion range of the two additional revolute joints in the normalized-constrained model. Finally, a design example is given to show the detailed design procedures of methodology proposed in this paper.
This study estimates the sound-absorption coefficient and transmission loss for the dimensions of clearances among the close-packed cylinders by theoretical analysis and compares these estimates with experimental values. In the analysis, we performed an elemental breakdown of the clearance configuration, and then approached each element as the clearance between two planes. Considering the effects of sound wave attenuation in each element of clearance, we found the propagation constant and characteristic acoustic impedance using three-dimensional analysis. By connecting these elements in parallel, we treated them as a one-dimensional transfer matrix. We then calculated the sound-absorption coefficient and transmission loss through the transfer matrix method. No sound-absorption coefficient could be obtained with calculations that did not account for attenuation. In addition, calculations that approached the clearance as an equivalent circle and a triangle did not match experimental values well. On the other hand, calculations using the method that accounted for clearance shape, that is the method used in this study, closely matched experimental values. Estimations of transmission loss expressed all clearances by connecting their transfer matrices in parallel. In calculations, these estimations did not account for attenuation, and the falling curve for transmission loss greatly diverged from experimental values. In the three calculations that accounted for attenuation, the falling segment of transmission loss showed frequency characteristics that were close to experimental values. Calculations through the methods that accounted for clearance shapes and that analyzed clearance as an equivalent triangle also had peak transmission loss values that closely matched experimental values.
A new type of gear pair consisting of a helical non-circular gear and a curve-face gear is designed, which can transmit the time-varying motion of intersected axes of rotation. Based on the generation mechanism of non-circular gear, the geometric model of helical curve-face gear is considered and the generating method of pitch curve of helical curve-face gear is discussed. According to the meshing theory, the meshing equation of helical curve-face gear is built and the mathematical model of tooth surface is developed. The method used to calculate its minimum inner radius and maximum outer radius is obtained. Furthermore, the method that the helical curve-face gear is generated by a shaper cutter is put forward and the three-dimensional model of helical curve-face gear is completed by modeling software. A phenomenon of transmission stability is discovered through contrast to the transmission ratio curve of experimental and theoretical value, which can illustrate the correctness of the design method and the practicability of the helical curve-face gear.
Planning under uncertainty is one of the important issues in production planning. The development of mathematical models under uncertainty has long been studied in order to avoid the impact of uncertain factors and to maintain stable and excellent performance of manufacturing system. In this paper, we propose a minimax p-robust production planning problem in the presence of parameter uncertainty. Particularly, we apply p-robust measure to a multi-period production planning and inventory control problem considering a set of demand scenarios. A scenario based robust optimization problem is extended to a minimax p-robust optimization problem by combining a p-robustness measure and a minimax objective function. The proposed model is compared with a deterministic model and a minimax model using simulation experiments. The results show that the minimax p-robust solution improves the average cost compared to other approaches while maintaining similar level of worst-case cost from the minimax model.
Owing to the aging of societies, the research and development of power-assist systems that increase human-operational forces have become popular. However, a power-assist system is a typical human-machine system. Therefore, the design and use of such a system should take into account the safety of both the operator and the conveyed objects. Some of the authors have already studied on power-assist systems, using an assist-control system design consisting of an impedance controller, a disturbance-accommodating optimal controller, a disturbance observer, and a reaction-force controller. However, unintentional input forces acting on a power-assist system may cause reckless motion and severe accidents in actual use. Therefore, we discuss the use of a robust control method to prevent this abrupt motion by substituting a frequency-shaped disturbance-accommodating optimal controller (FSDAOC) for the original optimal controller. The FSDAOC enables us to eliminate high-frequency-range motion by its frequency-shaping characteristic. The objective of this study is to assess the effectiveness of the FSDAOC-based method in enabling a power-assist cart to cope with the unexpected input forces caused by crossing a step without its load tumbling. We verified the effectiveness experimentally and found that our method had a tumble-prevention rate of 80%, which was an improvement over the 23% of the previous method.
This study demonstrates optical measurements of a real contact area and tangential contact stiffness in a rough contact interface between a soft adhesive elastomer and a glass plate. A friction tester developed in this study employs a rough contact interface between a rough rubber plate that is made of cross-linked poly-dimethyl siloxane (PDMS) and a smooth optical glass (BK7) hemisphere. This friction tester also equips a transmission optical system that is composed of a white light-emitting diodes (LED) light source, an objective lens system, and a charge coupled device (CCD) camera, for the in situ observation of the space distribution of the real contact area in the apparent contact region. Based on a simplified analysis, in accordance to the measurements of the transmitted light intensity, the amount of the real contact area was determined without any complicated calibrations. As a result, it was found that the amount of the real contact area linearly increased with normal load. Furthermore, using the digital image correlation (DIC) method, the time changes in the surface displacement field within the apparent contact region were visualized from the onset of the sliding motion to the onset of the steady sliding. These results provided a direct estimation of the tangential contact stiffness that resulted from the tangential deformation at the contacting asperity layer.