A large quantity of engineering plastics are used in electric industrial products. It is necessary to estimate the life of the product made of engineering plastics because of its shorter life and lower strength than some of ceramics or metals. New test device was developed for accelerated stress test. It can make the unsaturated environment above 100 oC under atmospheric pressure using superheated water vapor. Then it becomes possible to set wide range condition of temperature and humidity. Polybutylene terephthalate (PBT) is one of the hydrolyzed engineering plastics. Test pieces of PBT were submitted to accelerated stress test under some conditions of elevated temperature and humidity. Then they were provided to three point bending test. The time required for strength degradation has a good relation with water vapor pressure at each temperature. Then it became clear that the time required for strength degradation on each water vapor pressure was accelerated with temperature using the Arrhenius type equation.
Polydimethylsiloxane (PDMS) is used as a flexible cell culture substrate in medical and biological research fields. It has been demonstrated that surface modification by oxygen plasma irradiation was performed to improve cell adhesion, because PDMS has poor cell adhesiveness. However, the surface modification effect was not sufficient due to the flexibility of PDMS. In this study, active oxygen and UV lights were exposed to PDMS surface to improve the cell adhesion. The active oxygen was generated by a UV lamp emitting at wavelengths of 185 nm and 254 nm. The surface modification effect of PDMS before and after exposure of active oxygen and UV lights were evaluated. As a result, although the surface roughness did not change before and after exposure of active oxygen and UV lights, the wettability was improved. In addition, temporal change of PDMS surface after exposure of active oxygen and UV lights was smaller than that after plasma irradiation. Because the formation of silicon oxide layer on the surface was confirmed, it was considered that this layer prevented the penetration of polar groups getting into the PDMS substrate. Furthermore, osteoblast-like cells on the PDMS after exposure of active oxygen and UV lights were adhered and extend well. Therefore, it was demonstrated that a stable surface modification of PDMS surface was achieved by exposure of active oxygen and UV lights.
For the simple friction grip joint consists of two joined parts, one of which is tapped and bolted with the other with a bolt, the load capacity (Here, this is expressed by n described below) of the friction grip joint is analyzed using the strength of materials, and FEM analysis is carried out on 10 cases, which result in the following conclusions. [Here, F:Bolt axial tension, μCS : Friction coefficient on the contact surfaces between joined parts and also on the bolt bearing surface, WSCr : Critical applied shear force without any slip, n : Equivalent number of contact surface (=WSCr /FμCS).] (1) Introducing the shear spring constant of the bolt KBS and that of the joined part KCS, the theoretical equation to calculate the load capacity n, which contains only KBS and KCS, is derived. (2) The load capacity nth, calculated by the theoretical equation substituting KBS and KCS obtained through FEM analysis, coincides very well with nFEM obtained through FEM analysis. Therefore, it is concluded that the theoretical equation to calculate n using KBS and KCS is correct. (3)According to this theoretical equation, to increase the load capacity n, it is necessary to develop the joint structure which gives smaller KCS/KBS. (4) The maximum load capacity n=2 is obtained only under KCS=KBS in the case of the concentrated shear load applied on the upper corner of the joined part. (5) The problem left to predict n is to derive the equation that can accurately calculate KCS. (6) From the results of this analysis, the number “qF”, which is described in VDI 2230 Part 2 and corresponds to n, is judged to be too large from the viewpoint of slip.
In our previous study, it was found that the wear life of the DLC/AlN multilayer hybrid coating could be improved by approximately 80 times of that of a DLC film deposited directly onto an aluminum (Al)-alloy. This was done by controlling the hardness gradient of the AlN intermediate layer film. In this study, the frictional wear characteristics of DLC/AlCrN/AlN multilayer hybrid coating, in which the intermediate layer film was further hardened using the hardness graded AlCrN film, were investigated. This was done to improve the wear life of Al-alloy further and to require for application to machine parts. The frictional wear characteristics of the aluminum alloy-coated DLC/AlCrN/AlN multilayer hybrid film showed a longer life and lower friction coefficient when compared to a DLC/AlN hybrid film. In addition, the DLC/AlCrN/AlN wear life increased when a thicker DLC film was applied. In the wear tracks after the wear test, no cracking or peeling was observed in the DLC/AlCrN/AlN multilayer hybrid film. This was due to the improvement of fracture toughness value of the multilayer hybrid film by increasing the hardness gradient of the intermediate layer. Finite element simulations demonstrated that the DLC/AlCrN/AlN multilayer hybrid coating reduced the stress and strain in the film. Differences in stress and strain at the interface of the DLC film and the intermediate layer film were small. This simulation also demonstrated that a thicker DLC film further reduced the stress and strain in it. As a result, DLC/AlCrN/AlN multilayer hybrid coating is considered to represent a simple and effective means of improving the wear resistance of Al-alloy components.
Carbon fiber reinforced plastics (CFRPs) are widely used as components of marine structures. Thus, it is important to understand the degradation of the mechanical properties and its mechanism under seawater immersion. The object of this study is the influence of seawater immersion on the mechanical properties of plain woven CFRP laminates. Static tensile test and tensile fatigue test were carried out on the CFRP immersed different time under seawater for 300, 2500 and 5400 hours. The mechanical properties immersed for 300 hours was almost the same value compared with those of no immersion. However, the tensile strength immersed for both 2500 and 5400 hours reduced by 22.5% compared with that of no immersion. Then, from the fatigue results, in the low-cycle fatigue region, the fatigue strengths decreased as immersion time was longer, on the other hand, in the high-cycle fatigue region, the fatigue strength did not change significantly regardless of immersion time. As a result, the inclination of S-N curves became gentle as immersion time was longer. From observation of fracture surfaces by scanning electron microscopy (SEM), it was shown that the fiber/matrix interface deteriorated remarkably after seawater immersion. Moreover, the difference of damage growth behaviors due to immersed in seawater under fatigue loading was investigated using soft X-ray photography. On specimen immersed in seawater, the accumulation of damage expanded more widely due to interface degradation compared with that of no immersion. Considering these results, it was suggested that the static tensile strength depended on load transmission efficiency between fiber and matrix, on the other hand, the fatigue strength in high cycle fatigue region depended on the strength of fiber along 0° that had small influences by seawater immersion.
In this study, we intended to predict bearing temperature of oil bath tilting bearings with high degrees of accuracy, and developed a more detailed formula estimating mixing temperature at the inlet of the oil film on the pad. In order to consider the complicated flow in terms of the fluid and heat between pads, we precisely solved the conservation laws of the flow and energy at the control volume adding effects of rise of temperature due to agitation loss and leak between the shaft and the seal, and we got the accurate temperature of the mixing inlet oil. Moreover, we measured the bearing temperature distributions under various conditions with a test bearing bored 280mm in diameter to validate the analysis. Eventually, we got the following conclusions. (1) Compared with the analysis using the conventional model, the proposed model can reduce the errors of the oil film temperature distribution by one third. (2) In terms of prediction of the mixing inlet temperature that affects degrees of precision of the oil film distribution, the proposed model can improve 2 oC of variability and 10 oC of average errors, compared with He's model, and it found the fact that the method can improve the accuracy of the calcuration of bearing temperature. (3) The proposed model can predict temperature at the evaluation point within -8.6~+5.4 oC.
Cycle-to-cycle variation (CCV) of in-cylinder flow occurs in internal combustion engines. It is necessary to analyze CCV of flow to separate averaged-flow (as low frequency / low wave number) from turbulence (as high frequency / high wave number), because an averaged flow varies from cycle to cycle. Two averaging methods are used for the extraction of mean component from instantaneous flow. One is temporal-averaging method, the other is spatial-averaging method. In the temporal -averaging method, a fluctuation of flow is captured at fixed point in Eulerian, turbulence is regarded as the high frequency component, and it is removed by a low pass filtering. In the spatial-averaging method, the turbulence in spatial arrangement of flow velocity is directly averaged by using vortex scale as a threshold (e.g. Moving-averaging filter and Gaussian-averaging filter). However, the temporal-averaging and the spatial-averaging have completely different characteristics. Therefore, it is necessary to clarify the difference of filtering characteristics in each averaging filter. In this study, comparisons of averaged flow patterns of temporal-average and spatial-average are carried out. Moreover, variable sized spatial filter which is based on Taylor's frozen-turbulence hypothesis is proposed. As a result, variable sized filtering is found close to the filter characteristic of the time average method.
The initiation mechanism and its reduction method for combustion driven oscillation of industrial boilers with a center firing gas burner have been investigated experimentally and numerically. Eight fuel injection nozzles are arranged radially at the burner. The burner with two different diameter nozzles, main nozzle and sub nozzle, arranged alternately is proposed. When the burner proposed is set in the burner, the flame base becomes much stable compared with the standard burner in which the diameter of all fuel injection nozzles is the same because the small flame of sub nozzles is formed around the flame base of large flame of main nozzles. The ratio of diameters of main nozzle and sub nozzle and the angles of main nozzle and sub nozzle are important parameters on flame base structure. Numerical simulation confirms the stability mechanism experimentally observed.
In the present study, we have analyzed the flow field around a cube in a Stokes flow regime in order to estimate the diffusion coefficients of cube-like particles that are required for performing Brownian dynamics simulations of a cubic particle suspension. The main results obtained here are summarized as follows. In the situation of a uniform flow field with a Reynolds number sufficiently smaller than unity, the force acts on the cube only in the flow field direction, and the torque does not act on the cube. Therefore, the uniform flow does not induce the rotational motion of the cube. In the situation of a rotational flow field with a sufficiently low Reynolds number, the torque acts on the cube only in the direction of angular velocity of the rotational flow field, and the force does not act on the cube. This implies that the translational motion of the cube is not induced due to the rotational flow field. These characteristics are in good agreement with those for the case of spheres in a Stokes flow situation. From these results, we may conclude that the diffusion coefficients of the cube-like particles can be expressed by applying a correction factor to those of the spherical particles. Moreover, we understand that the translational and the rotational motion of a cube are not coupled in the condition of the flow filed with a low Reynolds number sufficiently smaller than unity. Furthermore, in Brownian dynamics simulations, the equations of translational and rotational motion of cube-like particles can be treated in the same way as the spherical particles by applying the correction factor.
Human errors of train drivers may cause serious damage. Therefore, research on human error prevention has been conducted by many researchers. In this context, brain activity measurement of train drivers using Near-infrared Spectroscopy (NIRS) has been conducted to monitor the condition of train drivers. In this study, we developed a compact wireless wearable NIRS that can be used in natural environments. The wearable NIRS has been used to measure train drivers brain function using a train driving simulator. Experimental results showed that brain activity of DLPFC increased when the driver made braking operation. The experiment for train driving with an accidental event was carried out to evaluate the relation between driver's attention and the brain activity. As a result, there was a difference in brain activity between with and without prior notice. Results showed that the increased attention of the train driver can be appeared in NIRS signal from the outer part of prefrontal cortex.
In preparation for optimal routing of patients to a hospital, this paper presents a traveling model of the ambulance that moves from the scene of an emergency to a hospital. The model is given in the form of a speed diagram along the route and constructed based on some rules: The ambulance moves with either a constant speed, a constant acceleration speed or a constant deceleration speed. The maximum speed changes depending on the legal speed limit for private vehicles. The ambulance decreases its speed to a specified level when it passes through an intersection with traffic lights or turns left or right. The model has eight adjustable parameters. They were optimized in the framework of the multi-objective optimization problem involving three objective functions, which are defined as modeling errors relevant to the traveling time, the fluctuation of blood pressure and the pressing force acting on the back of a patient. The genetic algorithm was used to obtain Pareto solutions to the problem. An optimal set of parameters was selected from among them. The validity of the model was confirmed by checking the objective functions for the validation data set. However, there was a limitation: The model does not match to the actual speed of the ambulance in such a case that it moves on the road where many traffic lights are placed close to each other and controlled synchronously.
In recent years, the use of renewable energy has been dramatically increased all over the world. Especially the photovoltaics power generation system is attracting wide attention, and the scale of market is expanding. In Japan, the introduction of photovoltaic system is beginning to advance, and the number of large-scale solar power plants has been rapidly increasing because the Feed-in Tariff Law (FIT) for renewable electric energy takes effect from July 1, 2012. However, accidents have frequently occurred under the rapid spread of photovoltaic power generation system. The support structures of the system were deformed or destroyed due to strong wind or heavy snow when the support structure was designed improperly. The main cause is considered to be a mistake in the structural calculation model, especially the model for joint parts. In this study, we conducted a full-scale experiment by simulating wind load and snow load on photovoltaic system. Furthermore, it was examined whether the joint parts model proposed by the Authors is valid for safety design of the support structure. In addition, we examined the stress condition and deformation of a member where buckling occurs, then, the buckling load was obtained by using the FEM model.
We implement and perform large-scale LES analysis for running groups of cyclists. The mesh-refined lattice Boltzmann method (LBM) and coherent-structure Smagorinsky model (CSM) are adopted for the simulations to achieve a high performance computing on the recent GPU supercomputer. In the simulation with 16 cyclists, the mesh spacing around cyclists is 4 mm, and the total number of the mesh is up to 8.1×108 and the number of GPUs utilized is up to 64. Each calculation took 4 or 5 days for the 8～11 seconds of physical duration. The flow around 16 cyclists in various arrangement is calculated, and the results show that the in-line arrangement is more effective than the rhomboid arrangement in the viewpoint of the total aerodynamic drag of the group; however, a specific person in rhomboid arrangement can obtain larger drag reduction and save the endurance. Results on two groups also suggest that the frontal group in rhomboid arrangement will be exploited as the wind protection of the backward groups.
In order to improve the efficiency of combustion engines, variable compression ratio (VCR) engine is researched. VCR engine changes the compression ratio according to its mechanical configuration. One of the solutions to construct VCR engine is the multi-link type. Multi-link type has an advantage for reducing high order shaking force which is the source of mechanical vibration. Since piston motion strongly influences shaking force, it is required to make the piston displacement profile close to sine curve. However, conventional combustion engine is designed based on four-link piston crank mechanism. Because of the design constraint due to four-design parameters regarding the four-link piston crank mechanism, piston displacement profile diverges from sine curve. In order to solve this problem, six-link piston crank mechanism is applied to VCR engine. Since six-link piston crank mechanism has six-design parameters, the piston displacement profile becomes closer to sine curve than that of the four-link piston crank mechanism. A Stephenson type six-link piston crank mechanism whose constitute four-bar mechanism is the double-crank mechanism is newly designed. And, this mechanism is applied to VCR engine model. We want to put this VCR engine model to practical use. We show basic characteristic of mechanical vibration. First, we measure frame displacement of VCR engine model when the compression ratio vary high compression ratio. Next, we compare frame displacement of VCR engine model with frame displacement of four-link engine model. As a result, tendency of basic characteristic of mechanical vibration almost equate to tendency of dynamics analysis.
The present paper proposes a shape optimization of the adhesive interface to improve the strength of adhesive structure under a multiaxial stress state. Its strength was evaluated by the failure function based on the first invariant of stress tensor I1 and the second invariant of deviatoric stress tensor J2, which has been discussed in the related previous paper. We defined a sum of squares of the failure function as an objective function in the optimization. Two types of the adhesive material properties, which put the major weights on only I1 and J2, respectively, were numerically examined. As a multi-material structure model bonded by the adhesive, a thin-walled butt-jointed cylinder was employed to avoid stress concentration at free edges in the adhesive layer. Three kinds of loadings were applied: only tension, only torsion, and a tension-torsion combined load. The shape of optimal adhesive layer according to each condition was in good agreement with the simplified theoretical solution. The kinked part of the optimal adhesive interface necessary for the pipe configuration was also reasonable to diminish the stress concentration around the corner. The obtained optimal shapes for the two typical adhesive material properties suggest that the present optimization method would be applicable dependent to the adhesive material parameters under multiaxial stress states.
Tasks using a multi-fingered hand are performed by sequentially applying functional finger actions to an object. We refer to a functional finger action as a “primitive action.” Various manipulations can be realized by coordinating the primitive actions. Multi-fingered hands are expected to realize various tasks, and for this purpose, it is necessary to configure software which has high reusability and efficiently for implementing many tasks. In this paper, we describe primitive actions as highly reusable software modules, and we outline the process of implementing tasks through a coordination of these primitive actions. First, we describe the configuration of a multi-fingered hand system and demonstrate how coordinations of the primitive actions are performed within the system. Then, we provide symbolic descriptions of coordination of primitive actions, and we describe tasks for the multi-fingered hand by an action network of which the nodes show coordination of primitive actions. This facilitates reuse of the task description, and provides efficient implementation of the task. As an example, the task of picking up a towel from a stack is described. Furthermore, we demonstrate that the basic specification of the robotic hand required for the task can be derived by analyzing the primitive action sequence.
This study aims to suggest a method for achieving an autonomous gait transition according to speed for a four-legged robot pacing at medium speeds. Our quadruped robot is simply designed and applies a central pattern generator (CPG) for each leg. Each leg is controlled by a PD controller based on a rhythmic output from the CPG. The four CPGs are coupled, and a hard-wired CPG network is constructed to generate a default pace pattern. In addition, we apply feedback of the body tilt to the CPG as vestibular sensory feedback. As a result, our robot safely locomotes at various speeds by autonomously changing the gait from walking to pacing to rotary galloping according to speed, despite the fact that the walk and rotary gallop are not predefined. A factor that causes the gaits' emergence is considered the body oscillation that changes according to the speed. The body oscillation exhibits a double peak per leg frequency at low speeds, no peak at medium speeds, and a single peak at high speeds. The phase differences between the four legs are adjusted according to the body oscillation by feeding the body tilt back to the CPG. The gait transition is triggered only by the body tilt angle, we expect that the suggested method can be generally used for quadruped robots.
Recently, the use of portable terminals with touch screens such as smartphones has spread rapidly. Many users have used these devices to browse the internet or social networking services (SNS). There are many link texts (hyperlinked texts) to navigate between pages or to download files. However, interacting with link text in a portable terminal with a touch screen can often be difficult because link texts that have low text height and narrow space between lines (set by web designers who wanted to display as much information as possible on a screen of limited size) can cause accidental interactions. Many studies have evaluated usability when using portable terminals with touch screens and most of these studies have focused on Button, which is a basic GUI component. In contrast, GUI design approaches for link text have not been received sufficient attention. This study is aimed at evaluating the influence of two factors, namely the text height and the line spacing of link text, on the error rate and pointing time to overcome the usability problems associated with link texts. User experiments on pointing tasks were conducted for seven text heights (1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 mm) and five ratios of line spacing to text height (0.1, 0.3, 0.5, 0.7, and 1.0). The result shows that when the text height is 4.0 mm and the ratio of line spacing is 1.0 (the height of touch-sensitive area is 8.0 mm), rapid and accurate pointing the link text can occur. We hope that these findings contribute to an easy-to-use design for link texts.
This study presents a method of determining the macroscopic viscoelastic properties as well as the macroscopic coefficients of thermal expansion and cure-shrinkage of fiber-reinforced plastics (FRP) in consideration of the dependence of the viscoelastic properties of the resin used in the matrix phase on the degree of cure (DOC). The DOC-dependent viscoelastic material behavior of the resin is represented by the generalized Maxwell model and is accompanied with non-mechanical strains such as thermal strain and cure shrinkage. Within the framework of computational homogenization, a series of numerical material tests (NMTs) are conducted on a representative volume element (microstructure) with different DOCs to discretely evaluate the macroscopic viscoelastic properties. On the assumption that the macroscopic material behavior can be represented by the anisotropic version of the generalized Maxwell model, we originally propose a method to determine the macroscopic viscoelastic properties and the macroscopic coefficients of thermal expansion and cure-induced shrinkage, both of which are functions of DOC. After numerical examples to determine these properties for a specific unit cell of FRP are presented, a simple numerical verification is carried out to demonstrate that the proposed method is capable of determining the DOC-dependent macroscopic viscoelastic properties associated with mechanical and non-mechanical strains.
This paper addresses the cascading design method of NVH (Noise, Vibration and Harshness) performance between an OEM (Original Equipment Manufacturer) and suppliers. The increasing trend toward electric vehicles requires the exploring of cascading design method, because of the easiness of the assembly of the electric vehicles. However, there are difficulties for the cascading design of NVH performance to overcome the coupling problem among each subsystem. It is generally difficult to divide key evaluation characteristics of a whole structure to individual characteristics of each subsystem because of the coupling resonance. In this paper, cascading design method which utilizes the MMC (Mutual Mean Compliance) was proposed. The MMC is used as an index to meet the final NVH target levels of a whole structure. Then, the MMC is cascaded to each subsystem or component. Finally, the cascaded MMC is achieved by improving individual MMCs of each separate subsystem, while being careful about the resonance of a whole structure caused by strong coupling. In the paper, it is shown that the recalculation of MMCs after subsystem’s structural modification is feasible using FBS (Frequency response function Based Sub-structuring). In addition, MMC based cascading design method using FBS was defined and organized as a procedure. The method was also verified by a numerical case study.
This paper presents theoretical consideration of a travel route and speed profile while turning at an intersection. These two are important for vehicle movement and ride comfort. The curvature distribution of a travel route is an important physical quantity that generates a traveling track. The formulation and characteristics of a transition curve at connection points for a non-interpolation curve, a single clothoid curve, and a multiple clothoid curve are investigated. The physical variable derived from a curvature distribution function is demonstrated, and the features of the three types of transition curves are explained. The integration value of a curvature distribution function represents an azimuthal angle. Therefore, the curvature distribution curve is the velocity of the azimuthal angle. Then, the first-order differential value of the curvature distribution curve is the acceleration of the azimuthal angle, and the second-order differential value of the curvature distribution curve is the jerk of the azimuthal angle. The theoretical equation of a traveling path is derived from the curvature distribution curve of the three types of transition curves, and their characteristics are formulated. Theoretical expressions of a speed profile of a real running vehicle at a traffic intersection are also proposed. Theoretical values agreed well with the measurement results. The validity of the multiple clothoid curve is discussed analytically as compared with the other two cases where it is interpolated by the non-interpolation curve or the single clothoid curve. It was also found that the influence of the multiple clothoid curve on vehicle movement and ride comfort was superior to those of the non-interpolation and single clothoid curve. Some results are presented in the form of parametric plots.
To improve the fuel efficiency of automobiles, the development of lightweight and high-strength material is required. Silicon, as a raw material for this purpose has attracted attention. So as method using silicon, Si alloys have been developed. Combustion synthesized β/O’-SiAlON powders were sintered by the hot pressing. Combustion synthesis is known as a self-propagating high-temperature synthesis (SHS). It is possible to design various materials with different properties by varying the ratio of Si, Al, O, and N because the composition of Si alloys is similar to that of SiAlON. In the present study, we prepared five types of Si alloys (S1, S2, O25, O75 and O100), which are similar to material design concept of β/O’-SiAlON having heat resistance and oxidation resistance, and used Si3N4 as a comparative material. We investigated the surface strength by performing the scratch test. In scratch tests, the load at which the fracture progresses to large-scale brittle fracture becomes larger in the order of O100, S1, O75, Si3N4, O25 and S2. The crystallite size of O25 is the smallest in Si alloys. Then, the composition of Al in S2 is the largest in Si alloys. Therefore, it found that Si alloy, which has small crystallite and contains more Al, shows high critical fracture load.
Recently, crowdsourced manufacturing concept highly attracts attention. In crowdsourced manufacturing, each participant shares their manufacturing resources to improve asset efficiency. To realize this concept, it is important how to make matching between resource requests and resource offers which achieve high efficiency improvement in fair way. Previously, some authors show production efficiency improvement with some resource matching algorithm. But, as shown in market design research field, matching stability is important in resource matching problem not only efficiency. In this research, we propose two stability indices 'number of blocking pairs' and 'loss caused by blocking pairs' for resource matching. The concept of blocking pair is well known, but to utilize it for resource matching problem, there are some obstacles. So, we propose analysis method of resource matching stability. And, we evaluate efficiency of the crowdsourced manufacturing system and matching stability of some representative optimization methods. The computational experiments give the following conclusions. (1) M:n type matching methods improve efficiency of the crowdsourced manufacturing system compared with the conventional dispatch method. (2) Resource matching method should be selected with consideration of features of crowdsourced manufacturing system, because distribution of profit among participants differs according to resource matching method, and matching stability differs according to stability analysis term length. (3) In the case of profit maximization of whole crowdsourced manufacturing system, a polite discussion is necessary, because profit of each participant might be reduced. In the future, we will develop new resource matching method with good balance between management effect and matching stability.
Configure-to-order (CTO) production is introduced for satisfying various individual customer requirements closely while saving various engineering efforts. In CTO, manufacturing companies modularize their products and customize them according to individual customer needs. A variety of modules and options must be provided for meeting various customer needs accurately. However, the more choices of modules and options are provided, the more customers and manufacturers have difficulties in arranging products which meet customer needs with them. In order that a manufacturer arranges optimal products more effectively for customers by means of CTO production paradigm, product architecture and order receiving procedure must be sophisticatedly designed with considering co-occurrence relations originated from customer needs. This paper proposes a novel method for designing product architecture and receiving order procedure with integrating customer needs, physical functions and entity structure through three design structure matrixes (DSMs) and two domain mapping matrixes (DMMs). The evaluation function that optimizes the degree of coherence between DSMs is formulated with a series of DSMs and DMMs. A simulated annealing based method is introduced to explore optimal modular architectures. A case study of an industrial three-axis linear-type robot is demonstrated. The design result by the proposed method is compared with ones that consider only physical functions and entity structure. Its result shows the validity and promises of the proposed method.
The volume of metal hydride packed bed changed by the influence of the expansion during hydrogen absorption and by the contraction during hydrogen desorption was measured by direct observation. The metal hydride used in the experiment are newly developed nano-structured FeTi (n-FeTi) by mechanical alloying. In the authors' previous study of LaNi5, the volume of the packed bed gradually increased according to the hydrogen absorption and desorption cycles because of the influence of particle breakup. On the other hands, in n-FeTi produced by mechanical alloying, particle breakup hardly occurred, and the volume of the whole packed bed decreased according to the hydrogen absorption and desorption cycles. Then, the volume change of the whole packed bed due to hydrogen absorption / desorption was small, and the expansion ratio was 5% or less. The porosity data of the metal hydride packed bed obtained in this experiment is considered to be useful for numerical analysis of n-FeTi and design of practical hydrogen tanks.
The extended subloading surface model is capable of describing cyclic loading behavior accurately. The elastoplastic deformation analysis by the finite element analysis can be executed efficiently by the complete implicit stress integration method with the return-mapping and the consistent tangent modulus tensor. The subloading surface model has been applied to the FEM analysis with the return-mapping method. However, the implicit stress integration procedure with the loading criterion used in the past works is applicable only to the description of monotonic loading process so that it causes the erroneous calculated result in the cyclic loading process. The rigorous loading criterion is adopted in this article. The validity of the implicit stress integration procedure adopting the loading criterion will be verified in forward and inverse loading processes for strain increments to various directions. The implicit calculations by the return-mapping method are performed adopting the past and the rigorous loading criterions in the monotonic and the reverse loadings under the bi-axial loading state in this article. Eventually, it may be stated that the accurate numerical solution can be attained by adopting the rigorous loading criterion for the general loading process in the multi-axial stress and/or strain state.
A parameter Ustar (U*), which is independent of stress or strain, was previously developed by the authors to express load transfer. The connectivity between the loading point and an arbitrary point is represented by U*. The most serious problem encountered while calculating U* using FEM is the high computation time required. For a large-scale model, computation would take several weeks even if a supercomputer is used. To overcome this difficulty, we had previously developed the inspection loading algorithm, which is adopted to several available programs (e.g., Nastran U*Toolkit). However, the previous algorithm is not applicable to structures that have slidable supports due to the complexity of the stiffness modeling contraction. In the present study, the stiffness modeling was exchanged and a new algorithm was introduced. The basic equation was extended to include the previous equation. The computation time reduction is over 90 percent. In usual FEM calculations considering the slidable ends, it is easy to obtain results by removing the degree-of-freedom of the stiffness matrix. Our goal is not there. The purpose of the present study is to develop a fast U* calculation algorithm that can avoid a huge number of iterative FEM calculations. In an actual calculation involving a passenger car body, the results obtained by the new algorithm coincided with the accurate values.
For enhancing the energy efficiency of a manufacturing system as a whole, it is critical to optimize energy consumption including that in the utility systems, which supplies compressed air, and that in each production line. Compressed air is used in the manufacturing domain in a wide variety of systems such as those that fix and hold works through pneumatic equipment. Compressed air systems account for approximately 10% of the industrial electricity consumption in the European Union. Therefore, a method for minimizing the energy used in compressed air systems is sought. From the point of view of energy saving in the operation of a compressed air system, a method is available for reducing the output of the compressed air system. However, if the supply of compressed air becomes insufficient by the reduction in the amount supplied, it can result in extension of the cycle time of the production line or in defective products; thus, it can eventually cause lower productivity. Therefore, businesses ensure adequate supply from compressed air systems in order to prevent the adverse impact of insufficient supply of compressed air on productivity; however, this results in wastage of energy. Therefore, it is necessary to simultaneously evaluate productivity and compressed air feed. However, there has been no progress in the research of methods for evaluation. Hence, in this research, a method, which is a hybrid of a manufacturing system simulation and computational fluid dynamics simulation, is proposed for evaluating the operation of both production lines and compressed air systems simultaneously. The proposed method is used to evaluate the deficiencies and excesses in the supply from a compressed air system and the reliability of the supply of a compressed air system in response to the daily production schedule. Moreover, the energy consumption per unit of production throughput is evaluated.
Nowadays, a monitoring technology has attracted attention in the factory automation fields regarding IoT (Internet of Things). However, it is difficult to monitor the process information from a round tool during rotating operation in machine tools. We therefore develop a novel tool holder equipped with a wireless communication function to monitor tool temperature and vibration. In the present report, we attempt to measure the inner temperature in drill tool and investigate the influence of feed rate and cutting speed on it. Moreover, we attempt to measure the tool vibrations in the rotational and radial direction in countersinking process. As a result, we demonstrated that the developed method with a wireless system is effective to estimate the tool temperature in drilling processes and the tool vibration in countersinking processes.