In mobile cranes, the deformation of the attachment during the slewing operation affects the ease of operation. Therefore, we constructed a dynamics analysis model to evaluate the deformation of the attachment and the behavior of the hydraulic circuit during the turning operation of the crane. Furthermore, the validity of the analytical model was confirmed by measuring the deformation of the attachment during the actual swing operation by image measurement and comparing it with the analysis results. Furthermore, we conducted a seismic response analysis of the crane using this model, and clarified that no major vibration that would cause the crane to fall or collapse during an earthquake.

We have investigated the finite element modeling for the wire rope including strands and a fiber core. The stiffness properties of axial direction and radial direction are validated by experimental results. The analysis roughly reproduces the experimental results. The further quantitative agreement could be realized by the additional modeling of the contact situations such as gap and surface pressure between element wires and between strands.

Hydrogen energy is expected to be put to practical use, and it is very important to understand hydrogen gas diffusion behavior and ensure safety when hydrogen gas pipelines are damaged. Therefore, assuming hydrogen gas leakage due to damage to a buried pipeline, hydrogen gas diffusion behavior in the ground and in the atmosphere near the ground surface was investigated by full-scale experiments and CFD simulations. In this paper, validation results of the CFD simulations by comparison with the experiments were shown. Reasonable CFD simulation results were obtained without using any special physical model by setting proper geological parameters such as soil porosity, gas permeability, and effective gas diffusion coefficient in porous media at constant leakage hydrogen gas flow rates. The influence of the geological parameters on the hydrogen gas diffusion behavior was investigated by sensitivity analysis. It was confirmed that fluctuations of the geological parameters had an effect of up to about 20%.

In order to use hydrogen as an energy source, our group are developing a rotary engine that uses hydrogen as a fuel. One of the challenges is high power output, and our group aim to promote combustion by computational fluid dynamics (CFD) inside the rotary engine. In this study, our group investigated the range of rotor-housing gap sizes that can perform CFD of rotary engines. Of the 0.01 mm to 0.09 mm investigated, the range in which CFD was possible was 0.09 mm to 0.03 mm. The results of CFD with the minimum gap of 0.03 were almost the same as the results of the visualization experiment.

This paper presents numerical solution to shape optimization for fluid structure interactive fields. A minimization problem for total dissipation energy in viscous flow field is formulated for the shape optimization. Shape gradient of the shape optimization problem is derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Reshaping is carried out by the traction method proposed as an approach to solving shape optimization problems. Numerical analysis program for the shape optimization problem is developed based on FreeFem++, and the validity of proposed method is confirmed by results of 2D numerical analyses.

This paper presents numerical analysis method of some shape design problems for unsteady viscous flow fields. The shape design problems for prescribing fluid force for an isolated body in uniform flow are considered. Shape gradient of the shape design problem is derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Numerical analysis programs for the shape design problems are developed based on FreeFem++, and the validity of proposed method is confirmed by results of 2D numerical analyses.

This paper presents a numerical analysis method of shape optimization for maximizing the discharged heat on sub-boundaries of unsteady heat convection fields. Many mechanical parts used in electoronic equipment such as computer has rotating object for thermal diffusion. However, our research group has not studied for shape optimization of heat convection fields considering these rotating objects. In the study, we consider shape optimization for the heat convection fields considering these rotating objects. Reshaping is carried out by the traction method proposed as an approach to solving shape optimization problems. The presented method is validated from the results of 2D numerical analysis by using FreeFem++.

This paper presents a numerical solution to multi-objective shape optimization for fluid-structure interactive fields. The mean compliance minimization problem in order to achieve stiffness maximization in structural field and the minimization problem for total dissipation energy in viscous flow field are considered for the multi-objective shape optimization. The shape gradient of the shape optimization problem is derived theoretically using the adjoint variable method. Reshaping is carried out by the traction method proposed as an approach to solving shape optimization problems. A new numerical analysis program for the shape optimization based on the traction method and a pseudo elastic analysis is developed by using FreeFem++. The validity of proposed method is confirmed by results of 2D numerical analyses.

In this paper, we present a multi-scale shape optimization method for shape design of a 3D periodic microstructure. The method consists of two-step optimization. As the first step, the material properties of a macrostructure are optimized using a size-optimization technique, where the components of the liner elastic tensor are set as the design variables, in which the objective function and the constraints are set according to design purpose. As the second step, the shapes of 3D periodic-microstructures are determined to identity the material properties of the macrostructures obtained in the first step, where the inverse homogenization method and the H¹ gradient method are employed. The shape optimization problem of a microstructure with hetero materials is formulated as a distributed-parameter system, in which the mass is set as an objective functional and the shape variation field is set as a design variable, the target macroscopic material properties and the homogenization equation are used as the constraints. Through numerical calculations, we confirmed the effectiveness of the proposed method based on the inverse homogenization method and the H¹ gradient method.

In this paper, we propose a non-parametric material orientation optimization method for vibrational eigenvalue problem of laminated shell structures composed of orthotropic CFRP materials. This optimal design problem that maximizes in arbitrarily specified vibrational eigenvalue is formulated as a distributed parameter optimization problem based on the variational method where an objective function based on the KS function is employed to solve duplicated eigenvalue problem. The sensitivity function with respect to the variation of the material orientation is theoretically derived, and the optimal material orientation distribution is determined by the H¹ gradient method for scalar variable. Specifically, the sensitivity function is fictitious to internal heat generation and given to the entire region as the Robin condition of Poisson's equation in order to obtain a smooth material orientation distribution. Then, the temperature distribution obtained there is deemed the optimal smooth material orientation distribution. Numerical analysis examples show the effectiveness of the proposed method for obtaining the optimal material orientation distribution that maximizes arbitrarily specified vibrational eigenvalue.

In the recent automobile industry, weight saving and fuel efficiency improvement and safety are emphasized. However, these are in conflicting relations and it is difficult to achieve both. In this research, we focus on the collision of automobiles and examine the energy absorbing material for automobiles that is adapted to the collision place. For that purpose, we first devise the shape of the member with high energy absorption using collision analysis. In addition, the material of the shock absorbing member currently used in automobiles is often steel. In order to achieve weight reduction, we will focus on aluminum, which is lighter than steel, and hybrid materials using CFRP, which has been studied in recent years.

In this research, we propose a method for improving the accuracy of meshless analysis by sub-domains of different sizes using an optimization method. As an example of analysis, the Poisson boundary value problem is analyzed by the proposed method, and its numerical solution and the exact solution of the problem are compared with the numerical solution by the sub-domain meshless method with the same size sub-domains proposed by the authors previously. It was found that the proposed method could improve the accuracy of meshless analysis by sub-domains of different sizes.

It is well known that the accuracy of solutions by the finite element method directly depends on the number of nodes used in the analysis, while employing more nodes requires much more analysis time. In this study, we propose a new finite element method that can produce accurate analysis results in a short time even with a coarse mesh. The proposed method utilizes both error information obtained by a posteriori error estimation and deep learning to improve the accuracy of analysis results. In this paper, the fundamental formulation of the proposed method is explained in detail, and its basic performance is tested through sample two-dimensional stress analyses.

The adaptive finite element method has been developed as a method for obtaining highly accurate solutions while suppressing the increase of analysis scale. However, it is not always simple and fast because it repeats adaptive remeshing and reanalysis. In this study, we propose a new adaptive method using deep learning, one of remarkably advancing machine learning algorithms. The proposed method only need to remesh once and can estimate accurate solutions by deep learning. In this paper, the fundamental formulation of the proposed method is explained in detail, and its basic performance is tested through sample two-dimensional stress analyses.

In this paper, we constructed optimal design method for multifunctional acoustic metasurface that have air vents and soundproofing function by topology optimization and inspected.

In indoor space that a person lives or works, ventilation is demanded from perspective of thermal environment. However, noise from external environment becomes a problem by establishing the through-holes such as windows on the wall. Ventilation and soundproofing are contradicting functions, but we designed the shape of the wall having the through-hole which enhanced a soundproofing function using an optimization calculation after having maintained a ventilation function. It was confirmed that the acoustic metasurface has three kinds of sound insulation methods: standing wave in the array direction , Wood's anomalous diffraction, and reflection of sound waves by the front cavity.

In this research, we propose a multi-scale design method of anisotropic acoustic metamaterials using level set-based topology optimization, based on a high-frequency homogenization method. Anisotropic acoustic metamaterials exhibit highly unique properties, generally based on the local resonance induced by their unit cells of its periodic structure. In previous work, metamaterials which are only composed of a single type of unit cell were in interest, leading to a limit in the macroscopic wave propagation properties that could be obtained. Therefore, in the present work, we focus on metamaterials that is combined of several types of unit cells, in order to achieve complex wave propagation. First, we introduce the high frequency homogenization method, which is capable of evaluating the macroscopic material property of periodic media based on local resonance. We then formulate the optimization problem for the micro-scale unit cell structures using the level-set based topology optimization method, designing unit cells which possess different wave propagation property at the same resonance frequency. Furthermore, we arrange the optimized unit cell structures in the macro-scale, in order to achieve complex dynamic properties. Finally, we present numerical examples to demonstrate the validity of the proposed multi-scale design method.

This paper proposes a scheme for imposing geometrical constraints in topology optimization to obtain structures considering the visibility of the product user, based on a fictitious physical model. First, a level set-based topology optimization method is concisely introduced, and geometrical requirements for the visibility are clarifid. A fictitious physical model described by a steady-state advection-dffusion equation is then constructed based on the requirements. In this model, virtual heat sources correspond to material domains and the advection direction is aligned with a radial direction around a view point. The visibility is evaluated by the values of the fictitious physical model, and the regions to see, where the value of the fictitious physical field is high, represent blind area. Next, an optimal problem is introduced based on the fictitious physical model. Finally, in the numerical examples, the proposed method yields optimal structure considering the visibility, confirming the validity and the utility of the proposed method.

In this paper, we propose a design method that enable us to improve the tracking error caused by flow-induced disturbance of a control system in multi copters. To solve the above-mentioned problem, we use the Robust Bode (RBode) plot for a feedback controller design in a control system of the multi copters. The RBode plot represents the robust performance criterion as allowable and forbidden regions on the open loop or the controller Bode plots. Using the RBode plot, control engineers can easily design controllers that suppress disturbances and account for perturbations of the controlled object with frequency response data alone. In the propose method, we also use a wavelet transformation in order to obtain a time frequency analysis of the tracking error caused by flow-induced disturbance. Experimental results show that the proposed method enable us to improve tracking error caused by flow-induced disturbance of the multi copters.

This paper presents an estimation method for forces of magnetic attractions between a six-crawler robot and running surfaces by a disturbance observer. The robot has crawlers which have magnets to climb a wall. However, there is a problem that the robot may fall if the force of the magnetic attraction becomes small. To solve this problem, we employ a disturbance observer in the control system of the crawler drive motor. The experimental results show that the proposed method enable us to detect the risk of falling caused by the magnetic attractions between the six-crawler robot and the running surfaces.

In recent years, the automobile industry has been required to reduce the weight of automobiles due to environmental problems. Although reducing the weight of a vehicle has advantages such as improved fuel efficiency, the reduced rigidity affects running performance. In this study, we investigated how the response performance of the vehicle changes by changing the stiffness of the suspension using theoretical formulas. From the calculated results, the relationship between suspension rigidity and steering stability was evaluated. As a result, it was found that the steering stability is greatly affected not only by the rigidity of the entire suspension but also by the rigidity ratio of the parts. Therefore, we aim to evaluate the rigidity and steering stability of the suspension so that it will not be affected by the shape of the suspension by examining the difference between the vehicle running test, analysis, and theoretical formula.

In recent years, due to advances in medical treatment, a wide variety of pharmaceuticals have been developed, and manufacturers are required to have packaging technology suitable for each pharmaceutical. From the viewpoint of quality protection of contents, PTP (Press Through Package) using multi-layer laminate film is being developed, but if the design conditions are not appropriate, the film may crack during the manufacturing process. Therefore, in this study, we try to predict the risk of fracture by creating a film forming limit diagram from the simulation of plug molding of laminate film by the finite element method and from the measurement of the principal strain by experiments.

The reactor coolant system (RCS) of a Pressurized Water Reactor consists of Class 1 components such as the reactor pressure vessel, steam generators, etc., and stress evaluations for various load conditions, seismic conditions, etc. are performed for the components. The load and seismic conditions are analyzed using a load analysis model for the RCS that is simulated by beam elements and spring elements. The obtained conditions are applied to analysis models for each part of a component to which stress analyses are performed. This process however requires many steps. In response to this, the authors are developing an evaluation process, called “Seamless Evaluation Process”, to not only optimize the process of transferring interfacing loads, but also to refine the loads and stresses on components by applying an integrated model consisting of the components in the RCS from load analysis to stress analysis. In this paper, the necessity, the status of development and a summary description of the Seamless Evaluation Process are described.

Due to the increasing demand for electric motors in recent years, the vibration analysis of electric motors is becoming more important. However, the spatio-temporal distribution of the electromagnetic excitation force generated inside the motor is complicated. Moreover, it is difficult to describe the elastic mechanical characteristics of the motor made of composite material. Therefore, it is difficult to predict the vibration of the motor with high accuracy. With the purpose of establishing a high-precision vibration analysis technology for induction motors, we established a magnetic field analysis model and a structural analysis model for the coupled analysis of magnetic field and vibration. The frequency response analysis was performed by coupling these models, and its validity is discussed.

Operational Transfer Path Analysis (OTPA) is a method obtaining contribution from each part to the reference point with small man-hours. However, simultaneous measurement of all reference and response signals are necessary to apply this method. Hence, application of this method to extra-large system such as buildings was difficult. In this study, we then attempted to increase the applicability of OTPA for the contribution separation to extra-large system by using several measurement systems. In the proposed method, several measurement systems were synchronized using optical cable or GPS system. As the verification of the contribution separation accuracy, the obtained contribution in each synchronization method was compared with the contribution by original OTPA. As the result, the optical synchronization method was clarified to be able to calculate accurate contribution with the original OTPA method and the method was found to be the suitable OTPA method using several measurement systems for extra-large products.

In this study, we considered a method to extract a hammering sound in noise environment by removing the noise component using noise transfer function for carrying out correct inspection of the target construction. In the first experiment, hammering test was performed using two tiles (defective and normal tiles) with or without loud white noise from a speaker. Through the proposed method using two microphones (single response and reference microphones), the hammering sound could be extracted well as the sound without noise. Subsequently, another hammering test was carried out when a drone was operated as an instance of the driving noise. However, the method using two microphones could not extract the hammering sound accurately. Then, the number of the reference microphone was increased from one to four to catch the generated noise of each rotating blade. As the result, the hammering sound difference between normal and defective tiles could be grasped better.

The volume of the siren prepared for an emergency vehicle is 90 dB or more and 120 dB or less at a position 20 m in front of the vehicle. It is supposed to measure at a height of 1 m above the ground of the position of 20m in front of the vehicle. In this study, it is assumed that an ambulance and a vehicle ahead are present. I calculated the sound pressure level around the ambulance and, by sound analysis, checked a decrement point. As a result, it is revealed that the forward sound pressure level of the front vehicle decreases because front vehicle was installed. This is a reflection of the front vehicle, and it is thought that a sound becomes hard to arrive. I was able to confirm a decrement point by the interference of a reflection and two speakers.

We have been trying to develop a repeatable self-healing material system by applying the mechanosensing mechanism generated by the bone cells and their network to artificial materials. As the first step, we applied the stress-activated channels by mimicking the function of the cellular ion channel to microcapsules. The purpose of this study was to confirm the self-healing behavior of the model specimens containing the microcapsules with the cold-setting resin. The microcapsules containing epoxy resin and curing agent were prepared by using the coacervation method, and the glass beads treated with mold release agent was used to form the stress-activated channels on their membrane. In order to confirm the function of the stress-activated channels, the tensile loading and unloading cycles were applied to the model specimens. As a result, the model specimens showed the recovery in the mechanical properties repeatability. Thus, the effectiveness of the self-healing material system proposed in this study was verified.

In this study, we perform buckling and postbuckling analysis to invesigate the pattern evolution in a sttiff gel film bonded on a soft substrate. The film and substrate are modeled as the Neo-Hookean solid model. Further, the film is assumed to obey the Flory–Rehner framework for polymeric gels. Since the film swells, the in-plane compressive stresses increases in the film, which causes buckling, i.e., patterns transformation occurs. Finite element analysis is conducted by introducing the Flory–Rehner framework into a user-defined material subroutine (Hong et al., 2009). The step-by-step eigenvalue buckling analysis, which was developed by Okumura et al. (2018), is employed to investigate the onset points and modes of bifurcations. The employment allows us to sequentially trace the first, second and further bifurcations on the bifurcated paths. The obtained results are shown and discussed.

It enables to see the distribution of force as a tensor quantity with the phase contrast microscope. As the resolution of the phase contrast microscope increases, it also becomes possible to see the dynamics of mass transfer in cells and the stress acting on cells and tissues. However, there is no technology to measure a two-dimensional birefringence distribution with sufficient accuracy. In this research, we try to achieve these by using the laser photoelasticity method. Therefore, we made a prototype device of a full-field type measuring a birefringence using a high-speed camera. In order to measure magnitude and direction of a birefringence at the same time, the photoelastic modulator that electrically controls a birefringence is used in it. The PEM modulation frequency is about 20 kHz. In the past, high-speed cameras with faster frame rates were required for FFT analysis of images. That increased the cost of the entire measuring device. The purpose of this study is to measure the two-dimensional distribution of birefringence and to measure the birefringence at a frame rate that is slower than the modulation frequency.

This study aims to investigate loosening behavior of acetabular cup under different loading condition with the presence of interfacial fracture. After long term service, dislocation, aseptic loosening result in decrease in hip joint quality and severe pains to patients which lead to the need for revision surgery. Dislocation mainly affected by mechanical factors such as stress state or interfacial damage. In order to investigate dislocation of acetabular cup, 3 dimensional model of acetabular cup structure including jig, simulated bone, acetabular cup and stem head of artificial hip joint was developed using finite element analysis software. The breakage of cup-bone bonding initiated at contact edged due to geometrical singularities. Moreover, an increases in vertical displacement of acetabular cup was induced by interfacial delamination. Three types of delamination propagation at the different regions of the acetabular cup resulted by different loading modes was revealed by using fracture mechanic approach. Opening modes of delamination was developed due to the change in loading amplitude which significantly enhanced the risk of loosening.

In order to quantitative prediction of abdominal aortic aneurysm (AAA) dilation, we proposed a novel prediction method using nodes on the surface of an finite element aneurysm model as tracking markers. In the proposed method, the current aneurysm shape was reproduced by expanding a hypothesized initial blood vessel FE model. Thus we evaluated the influence of the initial blood vessel configuration, mesh condition, and boundary condition on the node arrangement of expanded AAA model. The influence of the node arrangement was quantitatively compared using the maximum shear strain. As a result, it was found that the node arrangement when expanding the initial blood vessel model to the aneurysm shape depends on the initial blood vessel arrangement. Therefore, we proposed a method of arranging the initial blood vessel model, which is considered to have small artifacts in the node arrangement after expansion.

Collagen is known as a protein which exists in bodies of all animal species and nowadays it will be tried to apply to a novel material for medical devices. It is necessary to understand the strength of collagen to improve the performance and usability of the devices. The basic unit of collagen is called tropocollagen, and it has a rod shape with nano-meter size and contains characteristic triple helical structures. This is indeed too small scale to evaluate experimentally, so modeling and computer simulation by using molecular dynamics are effective to study it. There are many cross-linked structures between tropocollagen molecules, which are considered to largely affect its mechanical properties including strength and ductility. In this study, an all-tom model for computation is constructed in which three tropocollagen molecules are arranged in parallel together with some imaginary cross-linking molecules. The simulation of tensile test is conducted by pulling one of molecules using SMD method, in order to investigate the effect of cross-linking molecule in deformation process. As a result, it is confirmed that the model with cross-linking molecules requires more load than that without them until they take off tropocollagen molecule. In this study, it is found that cross-linking molecules play a microscopic and great role in increasing the strength of collagen.

Various molecules existing in synovial fluid contribute to lubrication of living articular cartilage. However, the tribological molecular mechanism at the frictional interface of cartilage tissue has not been elucidated. It has been reported that the molecular weight of hyaluronic acid (HA) in synovial fluid decrease in patients with joint diseases, and this change in the HA molecular weight would have an influence on the adsorption of proteins in synovial fluid on the friction surface of cartilage tissue. In this study, we directly observed the protein adsorption and the morphological change of collagen fiber at the surface layer of cartilage tissue before and after friction by using a multiphoton excitation microscope. Furthermore, we examined an effect of the difference in HA molecular weight on the frictional properties and the adsorbed film on cartilage tissue. In the results of friction measurement using high molecular weight HA, the friction coefficient decreased significantly compared to those using low molecular weight HA or PBS. In addition, different protein adsorption behavior, especially in γ-globulin, to the cartilage surface was observed depending on HA molecular weight, and it was suggested that a thickened layer of γ-globulin with high molecular weight HA played an important role of the low frictional property in cartilage tissue.

The external force from a mattress to the body surface consists of compressive force component and shear force component. Though the mechanical response of the mattresses to the pressure has been studied widely, the response to the shear needs to be studied more deeply. In this study, a device to measure compression and shear forces of mattresses was developed by using the previously developed device in our laboratory, a 3-axis force sensor and vertical and horizontal stages. The present device is controlled by applying displacement while the previously developed one is controlled by applying the horizontal stretch manually after applying a vertical load. By applying a vertical and subsequent horizontal displacement on gel-like mats with a spherical surface object, a linear force-displacement relationship in the horizontal direction was obtained at first and a slip motion with almost constant load later. By conducting finite element analysis, the changes of vertical and horizontal forces under shear was reproduced with a constant friction coefficient.

The cells in living tissue change not only their proliferation and motility, but also their mechanical properties in response to external mechanical stimuli. The mechanical properties of the cells and their adhesion strength with the extracellular matrix are extremely important in regenerating of load-bearing biological tissues such as blood vessels, bones, and ligaments. On these backgrounds, a micro tensile tester for investigating the mechanical properties of isolated cells was developed in our laboratory. However, the tester requires many manual operations for force-deformation analysis resulting a large time consumption. Therefore, in this study, we developed a micro-tensile tester capable of in situ measurement of force applied to the cells and their deformation by using image-based real-time analysis of deflection of a micro-glass needle attached to the specimen cells. Using this tester, we measured the tensile stiffness of normal vascular smooth muscle cells (VSMCs) and cervical cancer HeLa cells and their adhesion strength to the substrate. We found that both whole cell stiffness and surface stiffness of the cells were larger in VSMCs than in HeLa cells, and these differences also directly affected the adhesion strength of the cells.