Recently, high strength steel is used increasingly for plates which constitute the frame structures of vehicles. Since these plates become thinner, the buckling on the plates has been recognized as an important issue for automotive industries. For this issue, various methods have been proposed and are currently in practical use. In this paper, regarding bending buckling of box beams which have the rectangular cross-section with four thin plates, we try to derive the buckling stress based on the energy method. The main target of box beams has the aspect ratio of cross-section accompanied with compression buckling in the compressed plate. The bending buckling stress of box beams is derived in two cases of prescribed buckling modes. In first case, it is supposed that the buckling occurs at three sides subjected to compression and bending stresses. In second case, it is supposed that the buckling occurs only at the compression side and forced displacement at two adjacent plates is induced by the compression buckling. And the obtained results of accuracy are compared with the results of buckling eigenvalue analysis using the finite element method (FEM). The results of buckling stress in first case are observed a large difference from FEM results. The reason for this difference is that the buckling deformation assumed for the two surfaces subjected to the bending is much different from FEM results. In second case, the sufficiently practical expression as compared with the FEM results is derived for the buckling stress. So that, the approach shown in this paper is thought to have validity.
In order to investigate the fatigue properties of the fillet welded joint for non-load carrying type using hot-wire laser welding process, fatigue tests were carried out in comparison with the fillet welded joint using CO2 arc welding process to be widely used as a conventional welding method. Furthermore, the welding method to achieve the hot-wire laser welded joints with superior fatigue properties was suggested based on the experimental knowledge on the fatigue properties. It is clear that hot-wire laser welding process can remove the primer coating at steel plate surface during the welding process. From the results of the fatigue tests, CO2 arc welded joints indicated the higher fatigue strength compared with hot-wire laser welded joints because the hardness of HAZ was higher than that of the welded metal in hot-wire laser welded joints whereas the hardness of the welded metal and HAZ indicated the same value in CO2 arc welded joints in the case of using the same welding wire JIS:Z3312YGW11. Therefore, it can be improved the difference of the fatigue strength by selecting the welding wire as to achieve the same hardness in both of the welded metal and HAZ. Furthermore, it can be possible to achieve the hot-wire laser welded joints with higher fatigue strength compared with the CO2 arc welded joints by adjusting the wire feed speed and controlling the weld toe shape. From the experimental results, it was concluded that hot-wire laser welding process can be applied with high safety and reliability as alternative welding process to CO2 arc welding process.
In the framework of mechanics of plasticity plastic instability has been taken up as the onset of ductile fracture. The occurrence of ductile fracture begins from the appearance of necking phenomena. Hill established a sufficient criterion for uniqueness of boundary-value problem set by given velocities on a part of surface of a body and given nominal traction-rates on the remainder without any restriction placed on changes on geometry. Hill also introduced eigenstates intrinsic to the material wherein the strain can change while the conjugate stress is either stationary or coupled differentially with the strain. The former eigenstate is said to be active, and the latter one is latent. But, identical eigenstate can be obtained under either the latent or the active condition. The latent condition demands work done in second order to vanish, and the active condition corresponds to simultaneous stationary in loads. We adopted the latent condition as the concept of instability, and discussed the onset of plastic instability in several kinds of deformation under hydrostatic pressure. We showed that the eigenstate does not realize simultaneous stationary on loads except for some special cases.
The determination of energy losses caused by flow division at T-junctions is important in the design and analysis of industrial fluid transport systems. This experimental study addresses flow division through a 90° T-junction with a square cross section. On the basis of mean velocity at the main duct and the hydraulic diameter, the Reynolds number ranges from 1.3 × 103 to 2.0 × 104. The flow rate ratio (i.e., the ratio between the branch and main duct flow rates) is set between 0.2 to 0.8. Duct widths and heights are fixed at 10 mm in the main and branch ducts. Wall static pressure and loss coefficient are measured to quantify the energy loss. In order to investigate the relationship between fluid flow and pressure loss, velocity profiles are measured by particle image velocimetry. For laminar flow, the loss coefficient of the branch increases rapidly with increasing flow rate ratio because of a reverse flow from the main duct to the branch. For turbulent flow, the recirculation length in the main duct decreases compared to laminar flow. These experimental data provide empirical loss coefficient equations for T-junctions, which constitute useful tools for the determination of loss coefficients for T-junction.
The flow around a two-dimensional permeable porous plate placed normal to a horizontal flat wall was investigated with the aid of a laser Doppler velocimetry (LDV). The experiment was performed in a circuit-type wind tunnel having a test section of 200 mm in width and 200 mm in height. Three kinds of porous metal plate of different porosity and permeability were considered in the present work. Mean velocity vector fields in a streamwise wall-normal plane indicated that a recirculation region behind the porous plate moved to downstream with increasing in porosity. At the highest porosity,the recirculation region disappeared and a forward (streamwise) flow occupied in the whole region downstream of the porous plate due to the air flow permeation. These velocity profiles were compared to the theoretical analysis from Görtler, and it was found that the present results agreed with theoretical ones in the region where the forward flow dominated. A streamwise component of root-mean-square velocity fluctuation was enhanced just behind the porous plate with highest porosity. However, at farther downstream, it was weaker than that observed downstream of impermeable plate. Furthermore, a wall-normal fluctuating velocity decreased over the porous plate, although it rapidly increased immediately above the impermeable plate. To estimate a drag force acting on the porous plate, a simple technique based on a momentum balance of the flow was applied. The net body force was determined from the conservative form of the momentum equations by using the measurements of the velocity and pressure profiles. The results of the analysis showed a decrease in the drag force increasing permeability of the porous plate. The behavior of velocity field suggested that the permeable porous plate led to stable windbreak effect.
It is necessary to evaluate the geometry factor for predicting the flow accelerated corrosion (FAC) of carbon steel piping in a complicated flow field. Geometry factor is defined as the ratio of wall mass transfer coefficient in the piping systems such as orifice to that in a straight pipe. The mass transfer coefficient behind the orifice is computed by large eddy simulation (LES) and is also measured by electrochemical method. The experimental measurement is conducted with the pipe of the test section made of Ni, in which the whole pipe surface acts as electrode (referred as ’overall electrode condition’). The obtained results are compared with the previous experiments, in order to clarify the effect of the area of the electrode, with a point electrode embedded in an insulated pipe (referred as ‘point electrode condition’). Geometry factor obtained from the overall electrode condition is larger than that of a point electrode measurement. In order to simulate the mass transfer coefficient in pipe flow, we adopt the analogy between mass transfer and heat transfer, and calculate the unsteady temperature field using the numerical data of LES. Geometry factor predicted by heat transfer coefficient agrees well with that measured in overall electrode condition. The large scale motions with vortex structure of separated flow from the orifice influence the instantaneous scalar fields. Analyses of turbulent scalar transport and space-time correlation between wall scalar transfer and flow fields reveal that the mean wall scalar transfer is affected by not only near the wall region but also the coherent scalar fields away from the wall.
The complexity or randomness of the laminar-turbulent transition process of an inlet boundary layer in a circular pipe was analyzed by use of Kolmogorov complexity which is a very important measure of the randomness of various events. In the inlet region of the circular pipe, a jet that triggered a turbulent patch in the flow was periodically injected radially, and then propagated downstream periodically. Periodic velocity data which satisfies the phase constancy obtained from a hot-wire anemometer were compressed using a compression program running on a Windows PC. From the compressed data, the approximated Kolmogorov complexity, named AK, and normalized compression distance NCD were obtained. Although the distribution of AK of irregularly fluctuating velocity in the flow showed a slight discrepancy from the profile of fluctuating velocity intensity and intermittency factor, they exhibited qualitative consistency. Therefore, the objective judgment of the laminar-turbulent transition process based on the approximated Kolmogorov complexity mostly supports the conventional judgment. In conclusion, our study established the validity and usefulness of Kolmogorov complexity or algorithmic complexity to describe objectively the laminar-turbulent transition process in the mixing layer, flat plate boundary layer and pipe flow. With the aid of the AK we can distinguish the complexity within the turbulent region; on the other hand, the intermittency factor cannot.
Effects of vortex generators (VGs) on velocity field in an axisymmetric jet are experimentally investigated through hotwire measurements. The VGs have a shape of a half delta-wing and they are installed around the jet exit. In addition to the case without the VGs insertion, three control modes of the VGs are tested: static mode, in which all the VGs are kept inserted, axisymmetric mode, in which all the VGs are inserted at an operation frequency of 3.0 Hz, and alternating mode, in which 3 adjacent VGs are inserted at an opposite phase. The jet Reynolds number is set to 20,000. The results show that the VGs promote jet diffusion and entrainment of the ambient fluid near the jet exit. However, this results in gentler velocity gradient in the radial direction, leading to smaller velocity fluctuation and Reynolds shear stress. Consequently, such promotion effect becomes weak as the jet proceeds in the downstream direction and the entrainment rate in the cases with the VGs insertion becomes smaller than that in the case without the VGs insertion. The active motion of the VGs does not contribute to jet control and the effectiveness of the VGs mainly depends on the insertion time in the present study because the frequency of the VGs operation and the shedding frequency of coherent eddies of the jet are different by two order of magnitude.
The object of this study is to investigate experimentally effects of EGR gas on the ignition delay and the combustion, in a diesel spray using a rapid compression-expansion machine. EGR gas has CO2, H2O and N2. Therefore, we also research the influence of each gas on the ignition and the combustion individually. The results show that changes of ignition delay are few until the EGR rate of 20 %. When the EGR rate reaches 25 %, ignition delay increases drastically. The gradient of temperature against the ignition delay in arrhenius plot changes at 900 K. That phenomenon is independent of an ambient gas composition. Additions of CO2 and H2O to air prevent to lengthen ignition delay because of a low oxygen condition. Additions of N2 to air have longer ignition delay than EGR condition. And the reduction in the ambient gas oxygen concentration tends to make the two-stage combustion vigorous.
This paper proposes an obstacle detection method using reflective intensity of the Laser Imaging Detection and Ranging (LIDAR) for a mowing robot. In order to safely operate a mowing robot, obstacles around the brush cutter should be avoided. The 3D-LIDAR consisting of the 2D-LIDAR and a tilting-mechanism was used to collect the surface texture information around the brush cutter. However, collecting scanned data using the 3D-LIDAR included some small noises other than vegetation by soil or trash. If the brush cutter's auto operation was controlled using raw scan data, work efficiency is reduced by frequent stop instruction. For smooth control and efficiency suitable for mowing, it is necessary to assess the risk of obstacles. This study evaluated the size of the obstacles by clustering LIDAR intensity data. When LIDAR intensity data clustering using a grid of 10 mm resolution, it could detect about 40 mm stone obstacles within a 1ms processing time.
The objective of this study is to evaluate the compliance characteristics of a vertical multi articulated manipulator PA-10. The compliance characteristics of the PA-10, which is the flexible robot rather than other vertical robots, are derived from non-geometric errors such as flexibility of motors, strain wave gearings (harmonic drive transmissions) and joint links. The compliance model, which is comprised a simple kinematic modeling and the identified joint compliance, can estimate the tip deformation by applying the load in various postures. In this research, the compliance model is developed by considering the variation of compliance characteristics derived from the influence of the non-geometric errors and measurement errors. To confirm the usefulness of the compliance model, the verification experiments in which the tip compliance is measured are conducted under the various conditions and compared with the tip compliance ellipses which are computed from the compliance model. Furthermore, sensitivity analysis is carried out to reveal the influence of variety of the joint compliance for the compliance model. The experiments and the analysis results show that the compliance model can provide an estimated range which is within the experimental values and reveal the variation of compliance characteristics. In addition, usefulness of the compliance model is revealed by analyzing the variation of the compliance characteristics.
A bellows is a type of flexible joint. It has sufficient strength to withstand increases in internal pressure and flexibility so that it can expand and contract because it has an accordion-like structure with many-plates. In the hydraulic excavator, the bellows exhaust pipe connects the engine and the muffler. It is heated by high-temperature exhaust gas and also exposed to thumping vibration from the engine and the body. To ensure pipe reliability in these harsh conditions, we have to develop a technique to evaluate the bellows strength accurately in the design phase. In this study, on the basis of theoretical formulas listed in the Japanese Industrial Standards (JIS), we developed a bellows analytical model by using single shell elements with equivalent stiffness. Also, we modified the model by considering the contact effect to achieve higher accuracy. Then we evaluated the bellows exhaust pipe model which contains modified bellows models by comparing calculation results and measurements in the modal testing and the tensile shear test. From the results, we confirmed that the developed model can imitate the vibration characteristics and stress distribution accurately. In the next step, we will develop a prediction technique for dynamic stress on the bellows that occurs when the excavator is operating.
With the development of box structure like a car or plane, noise reduction technology is required. For interior noise reduction, it is necessary to identify a resonance mode which is affected by the acoustic characteristics. Meanwhile, noise problem with structural vibration has been studied as coupled structural-acoustic system. In case of coupled system, it is useful to understand a resonance mode as an acoustic dominant coupled mode for noise reduction. Hence, it is necessary to develop a method to identify the acoustic dominant coupled mode. The purpose of this study is ”identifying the acoustic dominant coupled mode by proposing the coupled structural-acoustic transmissibility”. The dominant characteristics of system in the coupled system and the coupled transmissibility are mentioned in a theory section. The proposed theory is verified by FEM simulation. It is possible to classify the dominant characteristics by analysing single system using the coupled transmissibility. For verifying the practicality of the method, experiments using a car are carried out. The coupled modes are identified by modal property identification experiment. Two coupled modes having an acoustic longitudinal 1st mode shape are identified. The acoustic dominant coupled mode is identified by measuring the coupled transmissibility. Hence, it is concluded that the acoustic dominant coupled mode can be identified by the coupled transmissibility.
We develop compact and broad spectrum coil for application of the current sensor. We propose the laminated substrates type coil using PALAP (Patterned prepreg Lay up Process) substrates excellent in high frequency characteristics and miniaturization, and we verify that frequency band of 1.2GHz and thickness of 0.7mm could achieve with a prototype.
The growth and the deformation of the solidifying steel shell in the continuous casting process were calculated considering the taper of the mold's narrow face. The mechanism of uneven shell growth in the mold was discussed by using computational method and observations of the shell at various operating conditions such as taper and slab width. It was found that the shell at the bottom of the mold becomes uneven when the narrow face taper is insufficient. The increase of taper is effective to even shell growth， but excessive taper causes wear of mold's copper plate and breakout of the shell. To solve these problems， various kinds of mold taper design such as multiple and parabolic have been developed and adopted to molds' narrow faces. At the actual operation of continuous casting， many kinds of steel grades are cast in various casting speed and width at the same mold. So， the online change of the tilt of the narrow face is done according to the operating condition. When applying multiple taper design to this width changing type mold for slab， the problem is that the rate of upper or lower taper changes in different slab width. In this paper， the relationship between multiple taper and the uniformity of the shell growth was discussed considering slab width quantitatively by using computational model and observed shell thickness of slab. By using the developed calculation models, the multiple taper designs were optimized and applied to the actual continuous casting molds’ narrow faces.
The present paper describes an application of non-parametric shape optimization to disc brake squeal phenomena. The disk brake squeal is known as self-excited vibration; the real and imaginary parts of the complex eigenvalue indicate the damping coefficient and natural angular frequency, respectively. The modes that have a negative damping coefficient cause disk brake squeal. Therefore, a main problem is defined as complex eigen value problem and a real part of the complex eigenvalue causing the brake squeal is chosen as an objective cost function for the shape optimization problem. For the solution to main problem which has a large number of DOF, component mode synthesis method adapting residual stiffness (CMS-R) is used in order to improve the accuracy of eigenpairs by conventional component mode synthesis method (CMS). The Fre´chet derivative of the objective cost function with respect to the domain variation, which we call the shape derivative of the objective cost function, is evaluated using the solution of the main problem and the adjoint problem. A scheme to solve the shape optimization problem is presented using an iterative algorithm based on the H1 gradient method for reshaping. For an application of the shape optimization method, a numerical example by using a practical disc brake model is presented. From the numerical result, the real part of the target complex eigenvalue monotonously decreases until it reach zero and effectiveness of CMS-R with regard to the shape optimization problem is presented.
Although the advantage of using arbitrarily-shaped polyhedral meshes for the industrial flow applications is clear, their employment to two-phase flows is rather limited due to difficulty in deriving and implementing algorithms without overwhelming complexity on such meshes. We present a numerical method based on the VOF (Volume of Fluid) method which works on arbitrarily-shaped three-dimensional polyhedral meshes with comparable accuracy to the methods for structured meshes. We extend the THINC (Tangent of Hyperbola Interface Capturing) method and the RDF (Reconstructed Distance Function) method respectively, to solve the advection equation of the color function and to estimate the interface curvature on polyhedral meshes without laborious geometric arithmetics.
The authors have been proposing a new method of color universal design without restricting usage of colors and their combinations named “lightness contrast dithering”. A key idea is that a solid color and a dithering of darker and lighter colors which approximate the solid color may look almost similar for people with normal color vision, while they could be distinguishable for people with color vision deficiencies since one is solid and the other is a pattern of dark and light colors. This paper reports the results of investigations on distinguishability of dither patterns (vertical, horizontal and oblique stripes) and lighting (illuminance and color temperature) robustness of lightness constrast dithering.
This paper deals with process design for mix-production line. First, we discuss issues of process line for mix-production and propose a method of process design for mix production to enhance productivity. The process design is treated as multi-objective problem in the method. Combination method of multi-objective genetic algorithm and clustering method is developed to design process line. Clustering method is utilized to generate groups of similar works with regard to connection relationship of parts in BOM and precedence relationship between works. We consider that quality of operation can be promoted and operation time can be reduced by assigning the groups of works to work centers. The developed method is performed on simple model to evaluate the performance of the method. The numerical experiments show that the number of clusters predetermined in the process of clustering is significantly affected to productivity of the line.
To reduce weight and improve efficiency of the power transmission, the gears must be miniaturized and lubricant viscosity must be lower. However, these changes will bring about augment of contact pressure and severe lubricating condition. These conditions might occur micro pitting. Accordingly, designing method for micro pitting is required to reduce weight and improve efficiency of the transmission. For designing micro pitting, the calculated flash temperature is used. On the other hand according to ISO/TR, micro pitting can be designed using ratio of sum of arithmetic average roughness and elastic hydraulic lubrication (EHL) minimum oil film thickness. However, in the designing method using flash temperature, it cannot take into account surface roughness and EHL oil film thickness. And if using designing method shown ISO/TR, the limit of each gear has to be measured. So, new theory about gear surface failure was focused. This theory says that false mode of the gear tooth surface is influenced by the frictional force. Based on this theory coefficient of friction was calculated using Matsumoto's formulae and frictional force was compared with micro pitting pattern on gear tooth surface. Results obtained are shown as follows. (1) The pattern of the area micro pitting was occurred is corresponded with the pattern of the area calculated frictional force is higher. (2) The result shown (1) gives that the occurrence of micro pitting has correlation with the frictional force on the tooth surface. (3) The reason why micro pitting is not necessarily grown into pitting is expected that caused load distribution change due to wear of tooth surface.
Honeycomb panel is widely applied into various structures such as lightweight and high stiffness panel. The glued honeycomb panel may catch fire. That's why some new high stiffness technologies have been developed. As a result of that, Truss Core Panel (TCP) has recently been developed. TCP has equivalent bending stiffness as honeycomb panel, and stronger in shear and more fire resistant than honeycomb panel. However, it is difficult in general to form TCPs compared to honeycomb panel. Therefore, multi-stage press forming process was investigated, but it cannot manufacture its structure with high aspect ratio for the limit of press forming process. The main aim of our research is to develop a new manufacturing process for Assembled Truss Core Panel (ATCP) by using bending method, suggesting the possibility to make much wider range of structures than before. In this paper, firstly we show the results of the trial product to confirm the ability of manufacturing ATCP. Then we evaluate the bending stiffness of the trial product of ATCP by measurements and FEM analysis. Finally, we conclude ATCP can be manufactured with high aspect ratio and the bending stiffness of ATCP can be estimated at the design-planning stage by FEM analysis. Some tasks on the development of ATCP will be presented by us in the near future.
Cooling structures require sufficient thermal conductivity. However, structure with thermal conducting could suffer high temperature, and thermal deformation could become serious. Thus, designing structures suppressing thermal deformation is an important task for designing cooling structures. Structural characteristics like stiffness and thermal conductivity are affected by structural shape. Thus, we intend to design structure with sufficient thermal conductivity, small thermal deformation, and light weight. Since these design factors have a trade off relationship, this research aims to develop design method achieving these characteristics with high levels. Structural optimization methods are able to be utilized designing structure satisfying contradicting design factors. Topology optimization (TO) is one of the most flexible optimization methodology. Thus, TO is selected as structural optimization in this research. Since we intend to design structures have sufficient thermal conductivity and minimum thermal deformation, the target of optimization is maximization of stiffness for thermal stress and thermal conductivity is introduced as a constraint. As criteria of stiffness and thermal conductivity, the structural compliance and thermal compliance are used. The structural optimization is implemented using solid isotropic material with penalization (SIMP) method of TO. Design variables are updated by sequential linear programming (SLP) in the early stage. In the latter stage, phase field method is applied to update design variables. To clarify the validity and the utility of the proposed methodology, some numerical examples are studied. Through these numerical examples, optimal shapes with high thermal conductivity and high stiffness for thermal deformation are clarified.
Hip replacement arthroplasties have been increasing in number as the number of patients with coxarthrosis is increasing. Prosthetic hip joints used for surface replacement with metal-metal contact are considered to be an effective choice for bone preservation. However, it has been shown that the metal-metal contact type of prosthetic hip joint could be toxic to human cells when powder from the abrasion of the Co-Cr alloy, a component of the joint, is ionized. We examined abrasion resistance and the elution of the metal ions about ceramic-coated metal pieces of the Co-Cr alloy using the Pin-On-Disk abrasion test method with a pseudo body fluid. As a result, the metal pieces with DLC coating showed the best performance in terms of their friction coefficient, abrasion resistance, and elution property of the ions.
This study examines a driver assistance system to predict driving behavior considering the pre-preceding vehicle behavior. The authors have defined an anticipation index called PRE3 and proposed a driving assistance system that indicates the PRE3 to the driver in real-time during a car-following. The proposed system indicates the evaluation index considering the relations not only between the preceding and following vehicles, but also between the pre-preceding and following vehicles. This paper aims to evaluate the performance of PRE3 by a test track field experiment that employs three passenger cars as the test vehicles. The test cars are equipped with various sensors and communication system including the camera and the target for headway distance measurement and the CAN data of the vehicles. Five drivers which participated in the experiment are instructed to follow the preceding and the visible pre-preceding vehicles with and without the driving assistance system. The field test showed that the proposed system is succeeded in reducing the relative velocity with the pre-preceding vehicle. Also, the positive high acceleration rate is infrequent when installing the PRE3 assistant system. It was concluded that the proposed assistance system is helpful to reduce the relative velocity with the pre-preceding vehicle, unnecessary positive acceleration and the variance of collision risk to the preceding vehicle.