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The deflection behavior of square sandwich panels with corrugated core of trapezoidal cross section at different pitch lengths and heights of trapezoidal pattern was investigated using the FEM analysis, where the panel size was fixed at total height of 13.6 mm and panel side length of 600 mm. FEM analysis was performed under the condition that four sides were fixed and uniformly distributed load was applied. With decreasing the pitch length, the panel deflection decreased. At extremely short pitch length, the panel deflection increased with decreasing the pitch length because the conversion of the external load into the shear force became ineffective by small amount of bonding area. On the other hand, with increasing the pattern height, the panel deflection increased. This behavior of deflection could be approximated by Gompertz curve, and the suppressive factor of deflection was considered to be the inclination angle of trapezoidal pattern. The larger the bonding width, the higher the inclination angle and the lower the pattern height of the inflection point. Moreover, with increasing the pattern height, the weight ratio of the panel decreased. This is because the reduction in the weight of the panel due to the thickness reduction is greater than the effect of increased deflection due to the increased pattern height. The product of panel deflection and weight ratio became minimal at a given pattern height. This suggests adaptability to weight reduction needs or stiffness needs by selecting the appropriate pattern height, and the compatibility for both needs can be met at the minimal point.

The process of a trough stepping into a wrinkle during web transfer is simulated by FEM commercial software. Two models are employed. The first one consists of a web and four cylindrical rollers, while the second one has a curved axis roller instead of a cylindrical roller to prevent wrinkles. After applying tension to the web, a roller is inclined and then the web is transferred by a roller rotation, if necessary, the curved axis roller is bent before tilting. The main outcomes are as follows. (1) As the trough of the web reaches the inclined roller and flattens at the inlet of the roller, a CD compression stress of the web increases due to slippage of the flattening and accumulates there. A wrinkle occurs when the maximum CD compression stress exceeds a critical value. The value increases with MD strain calculated by tension and Young’s modulus. (2) The wrinkle tends to occur when the MD strain is smaller or when the roller tilt angle and coefficient of friction are larger. (3) A boundary of the wrinkle occurring area is shown by a figure with the axes of the MD strain and the roller tilt angle. (4) The wrinkle is prevented from forming when parameters of the curved axis roller are suitably selected. There was a case where the wrinkle doesn’t occur for a large area of a bent direction angle ranging from -90° to +45°. (5) Spreading or shrinking of the web on the curved axis roller can be qualitatively illustrated by considering both the vector distribution of the roller surface velocities and the expansion or contraction of the bent arc of the roller.

Rail corrosion is one of the causes of rail breaks. The relationship between rail corrosion state and fatigue strength is still unclear. Therefore, to accurately estimate the fatigue strength of corroded rails, the prediction method for fatigue strength of corroded rails with pitting corrosion by actual stress and stress gradient was investigated. Bending fatigue tests were performed on the rails with pitting corrosion on the bottom surface. At this time, models based on the shape of the rail bottom surface were created, and actual stresses and stress gradients generated at the rail bottom surface were evaluated by the finite element method. When the fatigue test results were evaluated by the actual stress, the bending fatigue strength appeared to be higher when the fracture origin position was inside of pitting corrosion than when it was outside. This was an apparent phenomenon due to the use of actual stress, which could be explained in terms of stress gradients. Furthermore, using the relationship between the correction factor of time strength q, which expresses the relationship between the fatigue strength of new rails and the apparent fatigue strength of the corroded rails, and the stress gradient χ, it is possible to estimate the number of loading cycles that the corroded rails break in the fatigue tests.

In this paper, the mechanical properties of two-dimensional linked zig-zag structure subjected to in-plane compressive load was investigated. This structure has two counterphase layers consisted of inclined plate. The stiffness and the stored strain energy during the deformation were solved analytically based on the flexible bar theory proposed by Frisch-Fay(1962). In particular, the effects of micro-architecture of the zig-zag model on these mecahnical properties were discussed. The obtained theoretical results agree fairly with FE results. In addition, three cases of the compressive response of a connected zig-zag structure were examined in order to clarify the effective parameters on the equivalent elastic modulus and strain energy stored under certain constraining conditions.

In this paper, the large deflection response of a circular mesh tube under pure bending was investigated by using FE analysis. In the previous study[Nakamura, T., Ushijima, K., Evaluation of large deflection response of circular mesh tubes, Transaction of the JSME (in Japanese), Vol. 88, No. 915 (2022)], the effect of the ovalization across the cross-section on the bending response was neglected, but in this study, the influence of cross-sectional flattening on the nonlinear bending moment versus curvature was taken into consideration. There are three reasons for arising the maximum bending moment, but in this paper, we mainly focused on the two mechanisms (the large flattening response in elastic deformation and the plastic yielding behaviour) to the maximum bending moment. Based on our FE analysis, we proposed theoretical equations for predicting the maximum bending moment as a function of tube geometries and material parameters such as Poisson’s ratio and the plastic yielding stress.

Finite element mesh quality, which affects analysis accuracy and computational cost, is usually determined based on the designer's experience. In this study, we propose a GCN (Graph Convolutional network)-based method for evaluating the quality of 3D meshes composed of shell elements. In the proposed method, a three-layer network is constructed using GENConv with graph adjacency matrix and feature matrix as input. The feature matrix is created based on geometric shapes such as coordinates and the mesh qualities such as aspect ratio. A dual graph is constructed by converting finite elements into graph nodes and their adjacent parts into graph edges, and the created features are given to the graph nodes for learning. The proposed method is applied to a dataset of automotive side-member FE models and the effectiveness of the constructed network and the introduced mesh features is confirmed. We also visualize the attribution of mesh features and important factors in the obtained results by calculating the integrated gradients of the network. This allows us to select the important mesh features both positively and negatively and explains the basis for our predictions.

The computational simulation of the rolling process of the polycrystalline metal plate is performed using the second-order homogenization finite element (FE) method. The dynamically updated boundary condition (BC), which can describe the relative slip displacement under counter-friction force, is introduced to reproduce the progress of nodal displacement and force BCs during the rolling process. To directly solve the displacement under the BC accompanying friction force, the components of the stiffness matrix constructed by the macroscopic FE structure are edited using the friction coefficient and the contact angle. The elasto-viscoplastic mechanical behavior of the microscopic polycrystalline structure is described by the conventional crystalline plasticity FE method, and the relative scale-depended micro- to macroscopic FE model is established using the second-order homogenization method. The computational simulations of the rolling process with different friction coefficients, rolling radii, compression ratios, and grain sizes were performed using the established FE model. The macroscopic computational results could represent the fundamental mechanical behaviors of the rolling process, e.g., reduction of the plate thickness, increase and decrease in the rolling force owing to changes in the contact area, tensile and compression stresses at the inlet and outlet areas of rolling, X-shaped local deformation band beneath the work roll, increase in the rolling load owing to the friction coefficient, work roll radius, and compression ratio. Furthermore, the microscopic computational results clarified that nonuniform deformation in the polycrystalline structure changes depending on the macroscopic position, and the nonuniformity increases with the compression ratio. The microstructure located at the upper area of the rolled material experiences a two-stage deformation characterized by the contact angle while such a two-stage deformation is not observed in the microstructure located inner area of the rolled material.

Press forming is a mass production method that is used to manufacture many machine components such as automobiles, industrial machinery, and various plants. However, there is a limit to the degree of shape freedom that can be applied, so countermeasures against cracks, wrinkles, spring-back, etc., must be taken in the development process. It is well known that it is difficult to apply it economically in the case of small-lot production because of its high capital investment. In a previous report, the author reported that the folding line processing by press method / bending has a high degree of shape freedom, requires little capital investment, and can be expected to be applied for experiments and prototypes from small to mass production. This paper shows that press folding line processing using V-shaped punch can be applied as deformation induction based on experiments and FEM results. To improve the impact energy absorption performance in the event of a collision, notches and uneven surfaces called beads have been formed in the crush boxes and front side members as automobile parts manufactured by press forming. The bead has the function of inducing deformation so as to improve the impact energy absorption performance during the axial crushing process. However, bead setting for inducing deformation by the press forming, in addition to the difficulty of mold design/manufacturing, needs to correct the bead design after impact experiments using prototypes. This paper shows press folding line processing as deformation induction is very convenient and effective.

In this paper, the critical buckling temperature of a lattice sandwich panel was investigated using FE analysis. In the previous study[Sebata, Y., Ushijima, K., Study on thermal buckling temperature of a lattice sandwich panel, Transaction of the JSME (in Japanese), Vol. 88, No. 905 (2022)], a Pyramid-shaped core unit was selected and the effects of unit-cell height and width on the buckling temperature were investigated. In the present study, two kinds of lattice core, BCC and f2BCC were added for investigation, and the effects of the core stiffness and micro-architecture on the buckling temperature were discussed. It was revealed from this study that the constraint of rotational angle at the connection point between the face sheet and the core strands could enhance the local buckling temperature. Also, enlarging the core stiffness could enhance the local buckling temperature. Moreover, the local buckling temperature can be predicted theoretically based on the thick shell theory by considering the effective width of the face sheet for one unit-cell reflected by the cross-sectional area for a strut.

This paper reports the relationship between the length of panel side and the deflection of the sandwich panels with corrugated core. The deflections of the sandwich panels having the lengths of panel side from 100 to 1300 mm and the height of the panel of 13.6 mm were determined by finite element method, where the four sides of the panel were rigidly fixed and a uniformly distributed load was applied to the top surface of the panel. The maximum deflection at the center of the panel increases with increasing the length of panel side, confirming that a power law is established between the length of panel side and the deflection. The scaling exponent of the sandwich panel was about 3.3 and this value was smaller than that of the single plate, i.e., 4. The ratio of the weight of the sandwich panel to that of the single plate having the same length of the panel side and the different thickness, which becomes same deflection compared to the sandwich panel, was found to be smaller as the length of the panel side becomes longer. This effect of weight reduction was possible to be estimated analytically. Smaller value of scaling exponent of the sandwich panel compared to that of single plate was found be related with that the normal force applied to the panel was effectively converted to the shear force at the bonding interface between the core and the bottom plate.

In this paper, the large deflection of a circular mesh tube was investigated by using a finite element method. During this investigation, it is assumed that the tube is deformed elastically, and its structural nonlinearity due to large deflection was considered. In addition, a theoretical model of an arc-shaped beam is proposed in order to predict the equivalent stiffness. The equivalent stiffness can be used to estimate the nonlinear large deflection response of the tube. In particular, the effects of the number of spirals and the number of turns on the prediction accuracy was discussed.

We have developed a small size and high strength spiral bevel gear fabricated by five-axis controlled machining center. In the present report, we propose a novel spiral bevel gear with the rib at the end of face width to reinforce the tooth bending strength, which is machined with a ball-nose end-mill tool. We investigate the influence of the triangular rib on the bending stress both at the tooth root and around the rib and tooth deflection based on 1DCAE model, and demonstrate the effect of rib reinforcement at the proposed spiral bevel gear. Moreover, we compare the calculated stresses by 1DCAE with experimental ones from fabricated spiral bevel gear. As a result, a novel guideline is found to develop the small size and high strength spiral bevel gear with the rib at the end of face width from a view of rib shape.

This study aims to establish a loading test method on test tracks composed of a single rail fastening at rail joints. The authors construct FEM models for railway tracks which represent the rail joint parts accurately and perform the FEM analysis. The FEM results are in good agreements with the results of a loading test on a test track composed of plural rail fastenings. Based on the FEM model, the authors proposed the loading test method on test tracks composed of a single rail fastening and compared the test results of a single rail fastening and plural rail fastenings. As a results, it becomes clear that rail head displacements and rail tilting angles obtained from a single rail fastening are in good agreement with those obtained from the plural rail fastenings. Therefore the proposed method of loading test on a test track composed of a single rail fastening based on the FEM model is available to evaluate the performance of the rail fastenings systems of rail joints.

The purpose of this paper is to clarify the damping mechanism of the wheel that we have developed. In high-speed railway vehicles, noise associated with speed increase is a problem. We have developed a new wheel that can damp the rolling noise radiated from the wheel. This noise damped wheel has a special device attached to the inner circumference of the rim, which consists of steel sandwiched with vibration absorbing rubber. The noise damping effect was confirmed by the wheel rolling test, but the mechanism was unclear. Therefore, we elucidated the vibration damping mechanism using FEM. Using frequency response analysis, the equivalent radiated power (ERP) was calculated based on the response speed and element area when a load was repeatedly applied at a specified frequency. By calculating the modal ERP for a specific frequency, the natural vibration of the wheel, which contributes significantly to that frequency, was clarified. From this result, it became clear that the developed wheel disperses the natural vibration modes. It was also found that the vibration is reduced by damping of the rubber that acts on the dispersed natural vibration. Based on these findings, we concluded that increasing the Young's modulus of the rubber would improve the damping performance.

In this study, the critical buckling temperature of a lattice sandwich panel was investigated by using FEM. In particular, the effects of geometric properties, for example a core height h, a core length L, and the number of cells Nc on the buckling temperature, were discussed. It is confirmed that the lattice sandwich panel also has the global and local buckling modes that are common in a latticed members, and a correction factor which includes the effect of the number of cells Nc is presented for estimating the global buckling temperature of the panel. Multiplying the analytical equation of the buckling temperature which was derived from the conventional homogenization method by the correction factor, the buckling temperature can be estimated with a good accuracy. On the other hand, the local buckling temperature can be estimated by considering the buckling behaviour of a small plate surrounded by the cells and supported by four corners.

This paper reports the deflection behavior of the sandwich panel with corrugated core of trapezoidal cross section. The size of the top and bottom plates were 200 mm square, and the height of the sandwich panel was fixed at 13.6 mm. The models for finite element method were created by taking into account the geometrical limitations of the corrugated core due to the space between both plates and the manufacturing condition. The four sides of the sandwich panel were rigidly fixed, and a uniformly distributed load was applied to the surface of the top plate. The deflection always became maximum at the center of the panel. The analysis was performed by changing the inclination angle of the trapezoidal patterns of the core. It was found that there is an inclination angle of the patterns at which the deflection of the sandwich panel becomes minimal. The deflection of the corrugated core itself increased with decrease in the inclination angle of the trapezoidal patterns. On the other hand, the shear stress developed in the plates and the core increased with decrease in the inclination angle, which had the effect of reducing the deflection of the sandwich panel. It was found that these synergistic effects cause the minimal inclination angle occur. Moreover, the anisotropy of deflection of the sandwich panel, which is the difference in the deflection depending on the selected two sides of the panel when the relative two sides are fixed and loaded, was investigated. It was found that the anisotropy of deflection also became smaller at the inclination angle of the trapezoidal patterns at which the deflection of the panel became minimal.

Distribution and change of roll stresses, slippage, web tension, and friction forces during winding rolls are investigated using commercial FEM software. The model used here is two dimensional and consists of an isotropic web and a rigid winding core. The rolls are wound up to 70 or 80 layers by the center winder with a constant line tension and this winding process is numerically simulated. The results show that the roll stresses decrease when the front part of the web is tapered compared to the non-tapered case and approach the result of Catlow or Hakiel. The roll stresses and slippage increase as the line tension increases or an imaginary coefficient of friction or Young’s modulus decreases. The slippage occurs as the inner layers of the roll move faster than the outer layers. In case of large slippage, the tension of a point on the web gradually increases largely after entry into the roll. The friction forces acting between the web layers change violently in the inner layers of the roll and gradually decrease to zero in the outer layers. The friction forces acting on the inner surface of the web layer mainly direct to the direction of winding. A few local areas with extremely high friction forces occur and disappear abruptly and some concentric circles with relatively large friction force are observed constantly in the inner layers of the roll. The friction forces acting on the inner surface of the previous turn largely change in areas where the friction forces of the new turn are significant.

Wheel cleaving is one of the dividing methods of glass substrates, and is widely used in industrial scenes like manufacturing of flat panel displays. However, the crack generation mechanisms are not fully understood and therefore, the processing conditions are determined empirically. In this study, we observed crack generation behaviors during loading/unloading processes of toothed wheels by using highspeed imaging system. Finite element method (FEM) analysis of stress distribution in glass substrates were also carried out. As a result, two types of vertical cracks (circular and half-penny cracks) were observed just below the scribing wheel. Depending on the wheel shapes and applied load, the generation behavior of these cracks varied. Numerical results suggested that the crack generation behavior was determined by whether the tensile stress field was distributed up to the glass surface where some defects existed formed by wheel contact. This means low-height tooth and high applied load conditions produce a compressive stress field at the vicinity of glass surface, and the vertical crack generation is suppressed. To obtain a smooth cleaved surface, the half-penny crack generation during loading process is essential. For this purpose, precise control of indentation depth by optimizing wheel shape (tooth length, height and span) and applied load is necessary.

Recently bent products are widely applied into various structures. Sharp bending method in bent products has an advantage of fine appearance. On the other hand, it is newly known that origami forming can be applied to freely manufacturing method as fine appearance based on complex folding lines. Sharp bending and origami forming have a common point to require folding lines. Folding lines are produced to make V-groove before bending. At the case V-groove cuttings are carried out for folding lines, it needs machining center plants and working times. So, it is not suitable for mass production. In this paper, we propose new convenient V-shaped punch tools for groove formation in sharp bending and origami forming. So, origami forming can be expected as press method by using V-shaped punch tools. Also this paper reports on the findings of deformation behavior and the mechanism obtained from experiments on groove formation. Some phenomena and necessary punch load in V-groove processing are considered to reveal the mechanism of groove formation based on FEM (Finite Element Method) results and experiments of groove formation by using V-shaped punch tools.

This study aims to establish a new restriction of ballast renewal works at a low temperature in winter. The authors construct a FEM model of railway track which simulates the ballast renewal work at a low temperature and perform the FEM analysis under the various conditions of track radius of curvatures R, length of ballast renewal work L and decrease in rail temperatures Δt. As a results, it becomes clear that the inward rail displacements and changes in axial rail forces increased with the decrease in R, and the increase in L and Δt. Based on FEM results, the authors propose the restriction diagrams of ballast renewal work which provide the allowable decrease in rail temperatures from the neutral temperatures of rail newly welded under the restriction of converted temperature of changes in rail forces, inward rail displacements and alignment defects due to inward displacements. Furthermore the authors propose the flow for users to judge propriety of ballast renewal work at a low temperature by use of the restriction diagrams. Consequently, the ballast renewal work at a low temperatures exceeding the current restriction can be executed.

Palpation is an important medical skill to find bad lumps or tumors in the first medical examination. However, the practical palpation training has not been conducted enough to avoid patient’s risk in medical educational institutions. Hence, a virtual reality training system is useful for reproducing various affected parts. In this paper, the particle method to calculate the deformation of biomaterial with non-uniform elasticity is developed for the VR palpation system, which is based on the moving particle semi-implicit method (MPS). The target biological model is a maxillofacial part for dental palpation, which is discretized with 2 mm in particle intervals. In the analysis, we set a local calculation region near the palpation position to reduce computational time. The local region has a spherical lump of 10 mm in diameter. The accuracy of the present calculation is examined through comparing FEM’s one about deformation and stress. Here, we mention that there is hardly a comparison of MPS’s and FEM’s stress for biological tissues. This is because that the definition of pressure in MPS is different from one in FEM. Evaluating the method of stress on the basis of von Mises stress is newly proposed in order to improve the problem. Consequently, the displacement and stress by the present particle method and FEM are qualitatively the same distributions for an example local model with a lump. Furthermore, large elastic deformation is calculated with large palpation pressure. It is clarified that the palpation pressure is about 500 Pa to deform 5mm on the palpation surface. Finally, the particle method can simulate the deformation and stress of the practical maxillofacial model with a lump by the palpation pressures of 400 Pa and 600 Pa. In addition, computer graphics are made to easily understand the maxillofacial surface deformation for a VR system.

Surface winding processes are simulated up to 49-70 laps by means of a FEM commercial software. The simulation model is composed of a flexible web with linear-isotropic nature, rigid core and rigid drum (or rigid two drums and a rider roll). Stress distributions of wound rolls, tension (tangential stress) change during winding and layer slippage are investigated. The main results are as follows. In case of single-drum surface winding, the roll stresses become larger as a friction coefficient between web layers, nip load, drum diameter or a line tension increases, or Young’s modulus decreases. Poisson’s ratio has little effect. The roll stresses depend on not only WIT (increased tension of the outermost layer due to the nip load), but a decreasing rate of tension at a web point during winding, and they have a cross relation with a value obtained by integrating a web tension varying curve from the start point where the web enters the roll to the end of winding. In case of two-drum surface winding with differential drum speeds, the web tension varies complicatedly at three nip zones and is larger between the rider roll and the second drum. The tension of the outermost layer decreases with increase in the roll diameter. The slippage occurs as the outer web layer pulls the inner in the roll rotational direction and is larger at the outer web layers. When speeds of the two drums are equal, the first drum drives the roll and the tension is larger between the second and the first drum. The slippage is the same as the differential drum speed case in the range of 2/3 of the roll thickness, but in the rest range, the slippage occurs in the opposite direction.

In the automobile industry, quietness has been pursued with electrification and vehicle weight has been reduced for longer traveling distance. In design of component products to be mounted on vehicles, “low noise” and “weight reduction” have been also required. In order to realize them, it is important to approach sound characteristics in initial design stage and detail design stage. In the initial design stage, parts layout, material and rough dimensions are designed to decrease “average” of noise level. In the detail design stage, accurate dimensions and detailed shapes are designed to suppress noise peaks. These are called “two-step design”. Especially, analytical SEA (ASEA) is a suitable technology for the initial design because it provides results by using only theoretical equations without 3-D models. However, it has hurdles to be a practical process. One is a constraint of ASEA that accuracy of results can be kept high only in high frequency range. In this paper, we proved theoretically and practically that initial design using ASEA was effective even in low frequency range.

This research was aiming to investigate cutting characteristics of Polystyrene (PS) 3 mm square bars subjected to indentation of a center bevel (blade angle of 42°) steel blade and stacked on an AL anvil (underlay). To reveal the effect of contact width of workpiece against the anvil on the sheared edge profile of workpiece, the contact width was varied from 1 mm to 40 mm during the cutting test. In this process, the cutting load response was investigated and the sheared edge profile of workpiece was observed by a microscope. To discuss the effect of the anvil width on the deformation behavior of workpiece, a finite element method (FEM) analysis with elasto-plastic plain strain model was developed using a crack generation rule. Through the experiment and FEM analysis, a proportion of wedge penetration flow and crack propagation of sheared workpiece was revealed with the contact width. The peak maximum cutting force, pre-crack position and the breaking position were characterized with the contact width. When the contact width was two times or much larger than the thickness of workpiece, the wedge penetration flow form was remarkably appeared, while the crack propagation based smooth flat form was appeared when the contact width was narrower than the thickness of workpiece. A bent-down or bent-up deformation of workpiece varied with the contact width and its sign change occurred when the contact width was about two times of the thickness of workpiece. When choosing the narrower contact width than the thickness of workpiece, an asymmetric crack propagation occurred due to the misalignment of blade position against the left and right side edges of anvil.

This study aims to develop the switch and crossing for a single line operation at the double track section. First, the authors design and produce the simplified structure of the switch and crossing for passenger trains which can be installed without the cutting of the existing rails. Secondly, we test the fatigue durability of the front end of the structure by rolling fatigue test device. As a result, the sufficient durability is verified under the condition that the design use period is one month and the total annual axle loads are 1.0×108 kN. Thirdly, we perform the running test of the motor car on the product installed at the test track and confirm that the motor car can pass over the structure at the maximum speed 15 km/h. Fourthly, we perform the vehicle running simulation based on FEM and confirm the running safety of the structure from the point of view of the stress generated at the components, the derailment coefficient and the decrease ratio of wheel loads. Finally, we test the fatigue durability of the specimen and conclude that the welding part of the turn rail and bed plates, the spring for turning rails and rail fastenings have a practically sufficient durability.

If we use wood as a structural material, we can reduce carbon dioxide emissions. In Japan, houses have been made by wood traditionally and wood is used as a structural material such as pillar and beam. In order to use wood as a structural material, a joint is necessary. The shapes of these traditional joints are determined empirically and used without any analytical evaluation such as stress analysis. Therefore, stress analysis is necessary in order to use such joints efficiently. In this study, we make stress analysis of the gooseneck joint, which is one of the typical joints in Japan. The strain distributions of the joint are measured, and the stress distributions are obtained by digital image correlation method (DIC). We also simulate the gooseneck joint subjected to tensile load by using FEM. A male part and a female part are contacted in the joint region. Comparing FEM results to DIC results, the validities of both results are confirmed. Moreover, we propose the formulae to obtain the joint stress concentration factor by using the FEM results. The optimum shape, which gives the least maximum stress under uniaxial loading, is obtained by using the proposed formulae.

In this paper, sound absorption properties of poroelastic lattice structure are investigated through numerical simulation and measurement. The lattice structures discussed in this paper are composed of slender beams only (BCC) and beams and shells (BCC-S), and can be fabricated by using the selective laser metal melting machine. In our numerical investigation, the homogenization method is used to calculate a macroscopic elastic tensor for a solid phase, an equivalent density and a bulk modulus for a fluid phase. Also, the sound absorption coefficient for normal incidence can be calculated by using these macroscopic parameters. The obtained numerical result of the sound absorption coefficient agrees qualitatively with the experimental result. In particular, it is found that the dense BCC-S structure attains sufficient sound absorption capacity in comparison with other conventional sound absorption materials.

We have developed a small size and high strength spiral bevel gear fabricated by five axis controlled machining center. In the present report, we propose a novel spiral bevel gear with the rib at the end of face width to reinforce the tooth bending strength, which is machined with a ball-nose end-mill tool. We investigate the influence of the rib shape on the bending stress at the tooth root based on 1D-CAE model and demonstrate the effect of rib reinforcement at the proposed spiral bevel gear. As a result, a novel guideline is found to design the small size and high strength spiral bevel gear with the rib at the end of face width from a view of rib shape.

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.

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.

Dynamical Energy Analysis (DEA) has been introduced as a mesh-based high frequency method modelling structure borne sound for complex built-up structures. This has proven to enhance vibro-acoustic simulations by making it possible to work directly on existing finite element meshes circumventing time-consuming and costly remodeling strategies. In addition, DEA provides detailed spatial information about the vibrational energy distribution within a complex structure in the mid-to-high frequency range. DEA has been used to calculate the structure borne sound of an assembled agricultural tractor and good agreement between measurements and DEA calculations has been shown. In particular, it has been demonstrated that DEA can model shell structures accurately. However, it is still difficult to model a solid structure because currently DEA is based on wave transmission calculations through plate/plate junctions. Additionally, accurate FE meshes of assembled complex structures are often not available due to the uncertainties of modelling welds, bolts and rubber bushes between components. We propose here to integrate measurement data into DEA to improve the effectiveness of DEA modelling. Advanced Transfer Path Analysis (ATPA) is employed to extract energy transmission characteristics of a structure. The direct transfer functions between interface points are calculated using ATPA based on measured frequency response functions. DEA elements connecting interface points and representing energy transmission characteristics of the structure are created based on the ATPA result. The proposed method is verified with a finite element model of a simple structure.

Recently medical treatment device using a complex vibration is developed, it has been designed for the improvement of the conversion efficiency. However, few reports are available on the vibration transducers as used in small blood vessel. In this paper, the new type longitudinal-torsional complex vibration transducer was designed. The principle of vibration conversion from longitudinal vibration to longitudinal-torsional complex vibration was described in detail. In order to obtain the most effective performance, the structure parameters of the vibrator involving the mode conversion were mentioned. The important parameters to achieve the highest conversion efficiency from longitudinal vibration to torsional vibration were investigated by using the finite element method analysis models. The angled-multilayered converter was designed, and the important parameters as layers offset angle and lead angle of twist structure were discovered. The most effective parameters were obtained for the offset angle was 10 degree and the lead angle was 56-59 degree. It was confirmed that the vibration conversion efficiency was improved by making a hole for the suction into the device.

This study aims to develop a numerical simulation model of the folding process of a creased paperboard and to reveal the deformation characteristics of the creased paperboard. A cantilever type bending moment measurement apparatus was experimentally examined with a 0.43-mm thickness paperboard. To verify the folding mechanics of the creased part, the initial crease was varied within a certain range, and the lamination numbers were considered with 8 layers. A fluffing resistance model based on the z-directional (out-of-plane) tensile test was developed and simulated using isotropic elasto-plastic solid properties. However, because the fluffing resistance is restricted in the normal direction of the detached interface, in-plane shear resistance is not considered. When investigating the folding process of a creased part, the in-plane shear resistance and its breaking limit seem to be the primary characteristics. Therefore, in this work, in order to characterize the delamination and bulging deformation, an internal breaking criteria was numerically analyzed using a new combination model. A general purpose finite element method (FEM) code was applied to develop a combination model comprising the out-of-plane fluffing subroutine and the in-plane shear glue strength. Through the FEM simulation of the folding process of creased paperboards, the following results were revealed: (1) The simulated bulging profile of the creased part and its bending moment resistance well matched with the corresponding experimental result at the stationary folding state with a folding angle >20°. (2) The in-plane shear glue strength characterizes the pattern of the interlayer delamination in the folding process of the scored zone. (3) The initial delaminated span of the scored zone is estimated as >150% of the creasing width. (4) The initial gradient of the bending moment resistance is characterized by the scored depth.

This paper deals with the onset and development of wavy wrinkling of a web caused by a roller tilt using a FEM commercial software. The simulation model mainly used is composed of two rigid rollers and a web (a rectangular sheet) divided by a membrane element with four nodes. After applying tension to the web, both end parts of the web are fixed to the rollers and then the one roller is inclined gradually. The main results are summarized as follows. (1) The wavy wrinkling suddenly occurs at a tilt angle β of the roller. A pitch, amplitude and slope of the wavy wrinkles are larger in the loose side of the web comparing with those in the tight side. The number of wavy wrinkles of the web decreases exponentially with increase in β. A slack area is approximately estimated as an area where the von Mises stress is smaller than a certain value. (2) The number of wavy wrinkles becomes larger when Young's modulus or a thickness of the web decreases, or when the web tension increases, comparing at the same β. (3) The onset of the wavy wrinkling is strongly affected by the imperfection of the tensile strain distribution and of the web position relative to the rollers in the tension process. (4) Another wavy wrinkling simulation method is proposed, which makes a membrane buckle by applying a small out-of-plane displacement.

The gear rolling densification of Powder Metal (PM) gears leads to better mechanical properties due to the selectively closed porosity of some hundreds of a micrometer under the surface of the tooth. The optimization of this process is critical in order to reduce the overall design time of the process and to increase the quality of the rolled gear. One way to optimize the process, tool design and gear with stock is to conduct Finite Element (FE) simulations with a plasticity material model for porous metals. The simulations should be able to predict the resulted geometry and densification, after that the opposite procedure can be conducted and by using simulations as a design tool to predict the process parameters. In this paper, FE simulations are being performed for the gear rolling densification process. The aim is to investigate how such simulations can be used to improve the quality of the rolled gear. Moreover, to identify how more advanced plasticity material models such as the anisotropic model of Ponte-Castaneda Kailasam and coworkers can help and increase the accuracy of the calculations, compared to more commonly used models such as the one suggested by Gurson-Tveergard-Needleman (GTN). Furthermore, the results from the simulations in densification and involute profile are also correlated with experimental results to validate the accuracy of the simulations. Finally, the accuracy of the simulations in densification and involute profile will define if the target of optimizing the gear rolling densification process through FE simulations is realistic.

Titanium and titanium alloys have a lot of excellent characteristics when used for the parts and components of machines and structures. As for bolted joints, however, they are used only for some limited cases because of the high cost. Their specific characteristics, e.g., low weight and high resistance to corrosion, are highly attractive from the engineering point of view. In this paper, thermal contact coefficients at the interface composed of titanium and titanium alloys are measured, and the empirical equations for evaluating the coefficients are derived in the same form proposed in the previous papers. Then, heating experiments of bolted joints, tightened by titanium bolts, are conducted to examine how the bolt preloads vary when subjected to thermal loads, and the bolt preload variations are compared to the case tightened by carbon steel bolts. In the next place, aiming at a broader use of titanium and titanium alloy bolts, numerical analyses are performed to demonstrate the effectiveness of those bolts by incorporating the foregoing thermal contact coefficients into the finite element formulation. The numerical results are favorably in good agreement with the experimental ones, and they suggest that threaded fasteners made of titanium alloys can be favorably applied to the joints whose clamping forces are likely to decrease when subjected to thermal loads.

Karman vortex shedding occurs when the gas passes through the duct with tube bank of the heat exchangers, such as gas heaters and boilers. Very high level sound in called “self-sustained tones” occurs due to the interference of the vortex and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because insertion conditions have not been established. Then, perforated plates are installed in both sides of the duct to suppress the self-sustained tones. As a result, it was clarified that the perforated plate could suppress the self-sustained tone as expected. However this experiment was conducted using perforated plates with aperture ratio over 1% and the suppression effect appears in all of these aperture ratios. Wherefore the critical aperture ratio at which the suppression effect begin to appear could not be grasped in that experiment. This paper aims to clarify the critical aperture ratio and the effect of a cavity volume which is used with perforated plate on the SPL. Experiments were carried out to clarify these items. As a result, it could be obtained that the critical aperture ratio is about 0.25% and the influence of the cavity volume on SPL is a little. The optimum aperture ratio is concluded to be 4%.

Elastic moduli of metal sheets have planar anisotropy determined by crystalline texture. Texture control is effective in raising Young's modulus of steel sheets in some directions on the plane. Some steel sheets with strong elastic anisotropy produced by cold-rolling and continuous annealing can be applied to some structural components to improve their rigidity. However, the elastic anisotropy of the steel sheet with texture has been applied to few industrial products because the structural design using anisotropic materials is difficult. In the present study, two steel sheets with different texture were prepared for the experiments and numerical simulation, the torsional rigidity was investigated in steel square tubes with elastic anisotropy. Torsional rigidity have been examined, it depended on the direction of the sheet applied to the component. It was most effectively improved when the direction of the highest shear modulus coincided with longitudinal direction in the square tube. Elastic compliance matrix was identified by fitting to Young's modulus of steel sheet with elastic anisotropy, and finite element analysis was carried out using shell elements by considering the elastic anisotropy. Furthermore, the Voigt-Reuss assumption calculations of elastic anisotropy based on the texture measurements revealed that the decreases in shear modulus at diagonal direction were caused by the ODF intensity around {110} component, and the increases in shear modulus were caused by {112} component.

The criterion of micro-crack initiation on stronger, tougher steel, i.e., fail-safe steel, with an ultrafine elongated grain (UFEG) structure was studied through a combinations of numerical simulation and experimental observations and measurements. The test sample was machined from the rolled bar with 0° and 90° rotation along the rolling direction (RD). The static three-point bending test was conducted in a temperature range from 200 °C to -196 °C. The stresses near the initial notch were analyzed by three-dimensional finite element method. The conventionally quenched and tempered steel with a martensitic structure fractured brittlely with a peak bending loading. On the other hand, the developed steel did not fully fracture due to a lamella fracture even if load drops occurred during the bending test. The load drops are attributed to micro-cracks with normal to the loading direction (LD) or with an angle of 45° to the LD that occurred from near the initial notch root. When the crack orientation, i.e., LD is parallel to the RD, the developed steel showed a catastrophic fracture behavior. In the developed steel, the brittle fracture stress normal to the RD, σF⊥RD, was 3.2 GPa at temperature over -100 °C and 2.6 GPa at temperature below -170 °C. The σF of weak direction in the developed steel was 0.7 times lower than σF(QT) of the conventionally steel. When the effective grain size on fracture is assumed to be packet in the martensitic structure, the brittle fracture stress parallel to the RD, σF//RD, was estimated to be 6.2 GPa at temperature over -100 °C and 5.0 GPa at temperature below -170 °C. These values are 1.4 times as compared with the σF(QT), 1.9 times higher than the σF⊥RD regardless of the test temperatures. The anisotropic brittle fracture stress in the fail-safe steel is attributed to the microstructural features, and we would be able to control a fracture of the steel by designing microstructures.

Diaphragms made of stainless steel plates are widely used in switching parts in electrical devices, which control on/off of the electric supply of electric devices. However, there are many geometrical parameters for designing diaphragms such as height, diameter, and so on. The aim of the study is to estimate effects of the design parameters on click characteristics of diaphragms based on FEM. In the numerical analysis, the residual stress generated in the press forming has been investigated, and the click characteristics such as load and click ratio were estimated with the numerical model by changing the geometry of several diaphragms. Finally, the relationship between design parameter and click characteristics was defined as ‘design space’, and we could obtain the designable area by controlling the design parameters. Furthermore, if the diameter of a diaphragm was changed, we could choose the diaphragm by controlling the design parameters based on the proposed designable area. From these results, the proposed design space is useful for the estimation of the designable region of diaphragm considering click characteristics.

Thread cutting is one of the crucial machining procedures of mechanical processing. However, breakage of the nose of a threading tool is relatively common in fine-thread machining and directly related to the nose radius. The design concept of the unequal nose radius (UNR(1)) tool involves increasing the radii of the front teeth of a multi-point threading tool and maintaining the radius of the last tooth as the nose radius of the standard thread. This design can enhance the machining efficiency and remove burr. However, no method exists for determining the nose radius. Ideally, each tooth of a UNR multi-point threading tool should have approximately the same life span. Because the life of the tool is inversely proportional to the strain value, we proposed comparing the maximum strain value of each tooth to determine the nose radii. A recursive binary search was adopted for comparison. The best values were then gradually converged into a single solution to obtain the optimal nose radii combination. Considering a 3-point threading tool for example, the recursion results provided the optimal radii combination. The experiments confirmed that the machining efficiency of the 3-point threading tool was 15 times of that of a single-point threading tool.

Karman vortex shedding occurs when the gas passes through a duct with a tube bank of the heat exchangers, such as gas heaters and boilers. Very high level sound in called “self-sustained tones” occurs due to the interference of the vortex and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because insertion conditions have not been established yet. The purpose of this study is to clarify the effectiveness of the perforated plates for self-sustained tones. Then, perforated plates were installed in both sides of the duct to suppress the self-sustained tones. Because we thought that the perforated plate might have acoustic damping and resonance mode of the duct transverse direction to the flow might be suppressed by its damping effect, when the self-sustained tone occurred. Experiments were carried out to examine the suppression effect of the perforated plates installed. As a result, the suppression effect appeared in almost aperture ratio φ of perforated plate in case of φ > 0.01 (1%).

How a wound roll stress distribution will change when a nip roller is used during winding, and how a wrap angle around the nip roller will affect the roll stress distribution, these are investigated by simulating a winding process of two-dimensional models composed of a web, winding core and nip roller using a FEM software. The results show that the roll stress distribution is classified into the following three groups, (G-I) no nip roller, (G-II) nip roller with zero wrap angle and (G-III) nip roller with non-zero wrap angle (90, 180 deg.). The roll stresses increase in this order. The stress distribution of (G-III) is almost the same even though the wrap angle changes. Macroscopic slipping patterns (like J-line) of wound rolls indicate that large friction forces due to a nip load pull the outer layers to the core rotational direction. A summation of friction forces acting on the web surface having contact with the nip roller is zero, when no external torque acts on the nip roller. This indicates the stress distribution of (G-III) is almost the same. The friction force (the slipping velocity) is generated by a strain increase due to the wrap angle and a V-shaped tangential strain distribution due to contact with the nip roller.

We propose a flexible circular saw for high-speed cutting of curved lines in carbon fiber-reinforced plastic (CFRP). A conventional circular saw is appropriate for straight line cutting, but it cannot be applied to curved line cutting because of the interference between the saw body and the machined surface. To eliminate this problem, the flexible circular saw is deflected into a bowl shape by circular forced displacement, and the cross-section of the saw becomes a circular arc. A curved line can be cut by the bowl-like-deflection. The deflection shape is very important to realize the curved-line cutting without interference. We investigated the deflection of the flexible circular saw by a finite element method (FEM) analysis. Suitable slit shapes for the saw body are also proposed, based on the FEM results regarding stress in the saw body, the minimum radius of curvature, and the effects of cutting force and centrifugal force and eigenvalue. We also conducted a curved-line cutting test on a CFRP plate, and we found that the flexible circular saw can cut curved lines with high accuracy and high speed without interference between the saw body and the machined surface.

It was reported that the incremental sheet metal forming (ISMF) produces larger deformations as compared to the conventional forming processes. We developed a new ISMF method based on incremental punching. In this study, a theoretical method based on M-K analysis is presented to determine the forming limit curve (FLC) in this forming process and it has been integrated to our in-house FEM program. Also, a ductile fracture model is used for comparing of the forming limit of the process. A numerical example is then given and verified by experiments. The results indicate that the proposed method provides an available approach to determine the FLC of incremental punching process.

For the planarization process of LSI wafers, metal bumps covered with a certain kind of resin are machined with a diamond tool before its stacking. In this study, the deformation process and temperature field in this process are analytically simulated with FEM. In order to analyze the cutting process for resin which has a viscosity, the cutting simulator first has to treat the visco-elastic-plastic material property. Secondly, to analyze the cutting at the micro-meter level depth of cut, the analysis model was scaled down. Finally, to simulate the cutting process of a LSI wafer, PVC and 70%Cu-30%Zn brass were assigned a resin and a metal part, respectively. As a result, it was clarified that the machining temperature during a resin cutting remains high even if the depth of cut is a micro-meter scale because of its poor thermal conductivity. In addition, the chip forming process showed very discriminative deformation at the boundary between the metal bump and a resin.

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.

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.

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.

Owing to the population aging, it is expected that the number of patients undergoing acetabular bone and hip joint disease will increase. A total hip arthroplasty (THA) is one of the treatments for serious disease of hip joint. However, in the situation of massive acetabular bone loss, an acetabular reconstruction cage is additionally needed to reconstruct the hip joint. In this study, we focus on the acetabular reconstruction cage. The conventional cage is mainly made of metal. However, due to the lack of mechanical biocompatibility, there is a serious problem of ‘stress shielding’ of metal. The acetabular reconstruction cage made of CFRP could be possible to reduce the stress shielding, but the applicability for strength should be guaranteed. Therefore, the purpose of this study is to develop a numerical modeling method for acetabular reconstruction cage, and estimate the mechanical behaviors of bone and the cage. According to the numerical simulation, relative displacement of CFRP cage to bone was almost the same as Ti-6Al-4V cage. Moreover, strain energy density of CFRP was higher than Ti-6Al-4V in a wide range. Therefore, it was concluded that CFRP enables to design acetabular reconstruction cage which is more excellent for restraint of bone atrophy and promotion of bone remodeling than ready-made without influence on micromovement.