We have investigated the finite element modeling for the elevator wire rope 8×S(19) to reproduce the stiffnesses in both axial and radial directions. In order to validate the finite element calculation, compression test to measure the radial-direction stiffnesses of strand, fiver core and wire rope have been newly proposed. From the experimental result of strand, it is found that the radial-direction stiffness is greatly lower than axial-direction one and is affected by the contact situation between wires. It is also found that our finite element model well reproduce the stiffnesses of strand in the both directions. From the experimental result of fiber core, it is found that load-displacement curve in the radial direction involves a hysteresis, reflecting the mechanical property of fiber. The fiber core is modeled as an elastic body with the Young modulus of 300 MPa. From the experimental result of wire rope, load-displacement curve in the radial direction involves a hysteresis as well as the fiber core and the stiffness is similar with that of the fiber core. The stiffness increases as the tension of wire rope is increased. That is due to the strong contacts between wires and between strand and fiber core. Assembled finite element model of wire rope well reproduces the stiffnesses of wire rope in the both directions.

Owing to environmental concerns, fuel conservation and weight reduction are considered to be crucial problems in the automobile industry. Moreover, safety is an important issue, and thus studies on reducing injuries to vehicle occupants are very important and have attracted significant attention. In side collisions involving passenger cars, improvements in the occupant protection system and vehicle body structure are important. To design structures that are stiff and light, it is necessary to understand the load transfer from a moving deformable barrier to the structure of the automobile body. The index Ustar (U*), which is independent of stress and strain, has been introduced by the authors for expressing load transfer in the structure. Although the index Ustar has been successfully applied for performing load path analyses during frontal collisions of passenger cars, the boundary condition of a moving deformable barrier used in a side collision is load-controlled. Thus, the index Ubistar (U**) is preferable. However, the index Ubistar is currently defined under static loading conditions. In this study, the definition of the conventional index Ubistar was extended to ensure that it can be applied even when multi-point loads and inertia forces are applied. Based on the complementary energy, it was shown that the definition of a dynamic Ubistar can be expressed in the same form as that of the conventional static Ubistar. The calculation of the internal compliance matrix is performed only once, and thus its efficiency is higher when compared with that of the index Ustar. Then, the index Ubistar is applied to dynamic loading cases such as a plate with a hole and side collision of a passenger car. The load transfer at an arbitrary instant can be visualized by the Ubistar distribution, and this method aids in the selection of materials, arrangement of structural members, and stiffening of structures.

Tensile fracture simulations are performed on the (001) interfaces of Fe/Ni and Fe/Pd/Ni by molecular dynamics method, in order to discuss the interfacial strength by means of the eigenvalue and eigenvector of atomic elastic stiffness, B^a_ij=Δσ^a_i/Δε_j. Three models are considered, Fe/Ni stacked layers (Bimetal), 2 atomic interlayers of Pd between Fe and Ni phases (Pd 2layer) and same thickness Fe/Pd/Ni/Pd blocks (Trimetal). Before tensile simulation, distribution of η^a(1) < 0 atoms (η^a(1) is the 1st eigenvalue of the solution of B^a_ijΔε_j=η^aΔε_i) and residual atomic stress in each atomic layers are discussed. Then tensile simulations are implemented; the peak strain and stress of Pd2layer are significantly reduced from that of Bimetal. Trimetal shows slightly lower maximum stress at slightly higher strain than Bimetal. Bimetal shows fracture in Ni phase near the interface, while Pd2layer and Trimetal do in Pd phase near the Ni/Pd and Fe/Pd interface, respectively. Void generation process or the initial stage of the fracture is then discussed with the distribution of η^a(1) < 0 atoms and corresponding eigenvector, {Δε₁,Δε₂,・・・,Δε₆} ={Δε_xx,Δε_yy,・・・,Δγ_xy}. In all models the void is formed at the intersection between the interface and slip deformation, so that we can’t find clear mode for atomic plane opening but complicated modes for plastic deformation and inhomogeneous heterometal interface. However, large deformation modes or large negative η^a(1) definitely emerge at the opening void edges.

When analyzing cavitation erosion, it is necessary to grasp the stress state inside a material due to the bubble collapse process. In this study, the behavior of a vapor bubble collapse and the stress distribution inside the material due to the bubble collapse were analyzed by using an in-house fluid/material coupled numerical method. In order to evaluate the stress inside the material, the “stress influence area” is introduced and used for the evaluation of the amount of input stress to the material. For analysis results, the two times of impulsive pressure occur in a first collapse, which is caused by two kinds of mechanism, one is a micro-jet, and the other is pressure waves of rebound of the toroidal bubble. Even though the impulsive pressure on a material surface by the micro-jet is smaller than the pressure waves of rebound, the maximum equivalent stress which is installed inside the material is nearly the same value. Further, even though the maximum equivalent stress generated in the material is almost the same, the "stress influence area" is overwhelmingly large in the case of the pressure waves of the rebound as compared to the micro-jet. Therefore, it indicates that the stress state inside the material cannot be predicted just by the measurement of impulsive pressure on the material surface.

Internal combustion engines today are required to provide even higher levels of thermal efficiency. Raising the compression ratio and applying lean combustion are effective measures for increasing the thermal efficiency of internal combustion engines. However, raising the compression ratio gives rise to knock accompanied by pressure oscillations in the combustion chamber, thereby hindering the attainment of higher thermal efficiency. In short, it is necessary to have a technique for suppressing knock under engine operating conditions of a high compression ratio and lean combustion. The reaction characteristics of the fuel have a large effect on the occurrence of knock. Yet, the relationship between fuel properties and knock has still not been made entirely clear under conditions of a high compression ratio and lean combustion. Therefore, in this study a test engine was used to examine autoignition characteristics, pressure waveforms and other combustion characteristics under a condition of a high compression ratio, focusing in particular on fuel properties. As a result, it was found that, in addition to the fuel octane number, a fuel with a long ignition delay time in the high-temperature region is effective in suppressing knock accompanied by pressure oscillations.

Lean homogeneous charged compression ignition (HCCI) combustion achieves clean and high thermal efficiency, however the operating load range is limited by steep combustion and NOx emission near the high load. Therefore, it is necessary to switch the combustion modes of HCCI and spark ignition (SI) under minimized torque gap for practical use, but the large gap between the combustible air-fuel mixture of these two combustions makes it difficult to be accomplished. In this study, a new switching assist combustion using high-pressure fuel injection was applied to resolve this issue. As a result, the gap between HCCI and SI combustions was connected successfully.

Several high energy ignitions have been proposed to improve ignition performance of diluted combustion recently. One of the major issues in the high energy ignition systems is heat generation of an ignition coil due to increase of power consumption. This study proposes a method to reduce electricity consumption by controlling time distribution of discharge energy while keeping the ignition performance. The following conclusions were obtained as results of verification with an actual engine. (1) A concept for reducing the power supply-demand difference that does not inhibit flame core growth was proposed. (2) To reduce the power supply-demand difference, an ignition coil with an additional active coil was fabricated to enable time distribution control of ignition energy. (3) By controlling the time distribution of ignition energy, both energy saving and ignitability of ignition were achieved, and the prospect of net fuel consumption improvement was obtained.

In this paper, “the stereo matching interface” as a new visual recognition interface for remote operations is proposed. It satisfies the following functional requirements, which have been developed through a survey of prior arts. The stereo matching interface allows operators to recognize depth information about position errors to any remote target objects, 1) only uses information interpreted from the robotic perspective, 2) superimposes depth information on the image without separating the display area, 3) is a planar (2-D) image, 4) measures and presents depth information in the parallel to elevation angle direction and 5) allows users to selectively use arbitrary point depth information on the image. As a design that satisfies these functional requirements, we use that the parallax of the stereo camera images for the same spatial feature points changes with depth distance. The feature of this interface is that one of the images is edged by image processing to improve visibility, and it uses the human mechanism of selective attention. Furthermore, it was confirmed that the stereo matching interface satisfies the above functional requirements and fully performs the basic function. It has advantages of being able to recognize the presence or absence of depth distance errors over the entire display area (functional requirement 4 and 5) and to complete main operations using only intuitive images from the robotic perspective (functional requirement 1 and 2), without additional operations to identify any target objects. Furthermore, it is suggested that the following design values can be obtained: the reduction of falling and collapse of target objects, the synergistic effects in large scale-spaces, and the ease of integration into conventional equipment. Therefore, an alternative interface worthy of comparison with prior arts is considered to have been provided. On the other hand, the depth position error during turning and the convergence angle shift are practical issues. Besides, usability issues are the generation of depth indexes in the absence of spatial feature points on the surface of the target object and the visibility of the depth indexes.

This study focuses on autonomous robot navigation. In general, robot controllers are designed based on an accurate model of the environment. In contrast to this, we adopted an approach where information is written into the environment and used to operate the robot controller. This method can reduce the computational complexity and energy cost and has the advantage of expanding the system to consider multiple robots. However, the mechanism by which information is to be written into an environment in order to operate the robot in a real space with obstacles or walls has not yet been clarified. Thus, in this study, we adopted acoustic devices in the design to consider situations where robot controllers must interact with obstacles. First, we examined the acoustic field created by interactions between sound waves and obstacles using the finite-difference time-domain method and verified it in the real world. Then, we apply the designed acoustic field to an robot controller. The experimental results demonstrated successful robot navigation. The results also show that complicated sensor systems for the robot are not required to be designed to capture obstacles in working places. At the same time, our approach enable autonomous navigation even when the robot cannot visually recognize the target position.

This paper proposes a swash plate disturbance application device for human standing stability evaluation. It is known that when a mechanical disturbance is applied to the lower body, the COP (center of pressure) trajectory of the human is closely related to the standing stability of the human. Based on this fact, the paper first proposes a swash plate disturbance application device to measure the COP trajectory when the mechanical disturbance is applied. A linear identification method, where the input is the disturbance and the output is COP trajectory, is used to get a human standing stability system model. The model is expressed by a transfer function which includes the parameters of poles and zeros. Using the identified parameters, a human standing stability index is proposed. By some swash plate disturbance experiments for human standing and system identification experiments under several experimental conditions based on the proposed method, parameters of stability system dynamical model are obtained. The proposed index is calculated using the parameters. Then, it is found that the stability index values according to the experimental conditions such as normal standing and tandem standing, which is known more unstable one and less stable one, are properly obtained.

In recent years, the deterioration of infrastructure facilities such as bridges has become a problem. Precautionary measures such as visual inspections and repair by humans are in place as countermeasures for aging, but there are problems with cost and safety in such inspections. If inspection by robots becomes possible, both will be improved, which will greatly contribute to the maintenance of infrastructure facilities. In this paper, we propose a localizational position specifying system for a robot supporting bridge inspection of the moving robot under the bridge to support inspection of the bridge. Since the robot must travel on the steel structures at the bottom of the bridge, strong permanent magnets need to be installed on the edge parts in the wheels. Also, it is not possible to receive the coordinate information from the satellite as it travels at the bottom of the bridge. Therefore, a 1-dimensional low-cost LiDAR sensor and a stepping motor are used to implement as a planar LiDAR sensor which rotates 360 degrees, specify the position of the current robot by obtaining distance and direction data from fixed feature points. The localizational position specification through the planar LiDAR are examined by the experiment. As a result, it was possible to estimate the localizational position of the robot.

In recent years, electric powered wheelchairs have become indispensable in long-term care. Up so far, many electrically powered wheelchairs have been developed to reduce the burden of caregivers, in which omnidirectional electrically powered wheelchairs attracted researchers’ attentions because these types of EPWs can be used without stress in narrow and/or crowded spaces. In this research, we have developed an omnidirectional wheelchair typed mobile assistive robot with power assistance. In addition, traditional electric powered wheelchairs use a joystick or a force sensor as the operation interface. Joysticks cannot be used by the elderly or disabled, and force sensors are too expensive to be used for wheelchairs. In this study, we have developed a new type of Human Machine Interface (HMI) using a mechanism that can detect force at low cost by using linear potentiometers and compression coil springs instead of a force sensor. The accuracy of the developed HMI is verified, and its effectiveness is confirmed in practical use. Further, we conducted power assisted experiments in forward/backward and lateral directions and turn on the spot using an admittance control with the developed HMI attached to our omnidirectional wheelchair robot. From the experimental results, the developed HMI control accurately measures the forces applied on the wheelchair by the user. Finally, a power-assisted experiment was conducted in the straight direction on a 5-degree slope. These experiments proved that our HMI-based power assist system is effective for omnidirectional wheelchairs.

The granular damper enables damping of vibration by enclosing a plurality of particles in the structure. The vibration damping principle of the granular damper is the dissipation of energy due to friction between particles. Since this damper is easy to install, it has been applied research as a vibration control structure for various machines. In order to ensure vibration damping performance and perform design, it is necessary to predict the frictional force between particles and the collision force with a container by simulation. The purpose of this research is to propose the evaluation method of the vibration damping performance of the granular damper and the prediction method by the discretized element method using the fine particles with the basic particle diameter of 100 μm or less. As for the experimental method, various evaluations have been made possible by a simple test method in which fine particles are enclosed in a metal plate. With this test method, we succeeded in obtaining a good damping effect even with a granular damper with a particle size of 100 μm or less, and finding the control factors necessary for design.

“ The passive dynamic biped walker robot ” can walk on a slope due to only the function of gravity. Many researches concerning this walker are executed nowadays. The conventional dynamic model of this walker has two legs connected with its body like a rigid pendulum. The lateral rolling motion of the body causes to swing each floated leg forward alternately. From this, the walker can naturally walk down a slope. But this walker has a possibility of falling down due to the instability by the instant standing with one leg alone. On the other hand, the descending model of this report also has the same particularity that can walk down a slope without active control. But it has the appearance that two fan-shaped disks are connected at the arc centers with free rotation. Consequently, the possibility of falling down almost vanishes. The principle of descending a slope of this model is based on the yawing motion induced by the lateral deviation of the gravity center which the rolling motion of the body generates. These rolling and yawing motions are consequently coupled each other and generate the self-excited swaying motion like a switchback. The purpose of this research is to clarify the conditions of the occurrence of this switchback motion. The author analyzed this interesting dynamic motion of each fan-shaped disk as three dimensional descending movement of the rigid body without a fixed point. From this analysis, he could confirm the occurrence of the switchback motion which also was observed in the experiments.

In mechanical structures where the components are joined by bolts, the vibration damping depends mainly on energy dissipation due to friction at the contact surfaces. In this paper, we propose a method for estimating modal damping ratios of bolted structures with partial overlap region by the dynamic finite element contact analysis. First, the eigenvalue analysis considering the contact surface stiffness is performed and the natural frequencies are evaluated to determine the pressure load to be applied to the contact surface in the contact analysis. Then the transient analysis is performed with a single frequency sinusoidal forced displacement to obtain the frictional dissipated energy for each mode shape and the modal damping ratios are estimated from the dissipated energy. The validity of the proposed method is confirmed by comparing the estimated damping ratios with the experimental results. We carry out the contact analyses by varying the excitation amplitude to examine the amplitude dependence of the damping ratio and reveal the reason for its amplitude dependence based on the slip velocity and the frictional force on the contact surface. The results show that the modal damping ratios have a strong amplitude dependence. The damping ratios change drastically in the lower amplitude range while they indicate a small change in the higher amplitude range. This is because the transitions from sticking to slipping occur over the whole contact area in the lower amplitude range, as a result, the dissipated energy rapidly increases compared to the vibration energy. In contrast, the dissipated energy increases at the same rate as the vibration energy in the high amplitude range.

In recent years, high-power and low-cylinder engines are widely used. These engines produce a strong torsional vibration due to engine combustion in the powertrain. In automatic transmissions, a lock-up clutch which connects the engine and the gear train directly is operated in low engine rotation speed for fuel economy. The lock-up clutch operation in the low engine rotation speed causes the increase of vibration due to the resonance. To suppress the torsional vibration, a lock-up damper, a torsional spring, is attached in the torque converter. Centrifugal pendulum vibration absorbers (CPVA) are also developed for the countermeasure. However, the natural frequency of the CPVA varies in the large amplitude due to the nonlinearity, and large size of the centrifugal pendulum vibration absorber is needed to increase the suppressive effect. To overcome these problems, a new centrifugal pendulum vibration absorber with slider crank chain (SCDA) is invented. In this paper, the equation of motion of the SCDA is derived, and the suppressive effect of the SCDA is discussed theoretically. It is found that (1) the nonlinear natural frequency of SCDA can be designed almost linearly with its optimal link length ratio, (2) the SCDA with optimal link length ratio can suppress the vibration amplitude effectively, and (3) the suppressive effect of SCDA is larger than that of the CPVA.

This paper provides a vector-valued level set-based topology optimization method for multiple materials. The proposed method is characterized by a perfectly symmetric representation of multi-material by a vector valued level set function, which lowers the dependence of initial configuration in the optimization calculation. The problem that the multi-material optimal configuration depends on how the parameters are given, due to the asymmetric material representation, is fundamentally solved. Also, this paper implements the method to adjust the geometrical complexity of optimal configurations with the regularization parameter. First, a topology optimization problem is formulated based on the representation by the perfectly symmetric vector-valued level set function, and the method to regularize the optimization problem is generalized for multi-material topology optimization. Next, we construct an optimization algorithm in which the level set function is updated by the reaction-diffusion equation. Finally, two- and three-dimensional numerical examples are shown to confirm the validity and utility of the proposed topology optimization method.

Origami structures with curved creases (curved origami structures) have gained extensive attention in several fields. It is well-known that self-locking is one of characteristics of the curved origami structure. When the self-locking occurs, its shape is fixed without external forces. On the view of computer-aided design for the curved origami structure, many studies have focused on computational modeling methods of its shape. However, there are few methods to evaluate mechanical characteristics of the curved origami structures and to simulating folding behavior from unfolded state to folded state with occurring self-locking. Therefore, this study proposes a new computational modeling method for the curved origami structure. In the proposed method, truss elements are applied to creases modeling in finite element analysis and the self-locking is simulated using stepwise forced displacements. To clarify availability of the proposed method, design and simulation problems of origami grippers which are curved origami structures with occurring self-locking are investigated. Through this investigation, feasibility of origami grippers is also discussed.

In this study, we conduct modeling and numerical analysis of a straight edge dislocation in a three-dimensional geometrically nonlinear elastic medium. Based on the fundamental framework of geometrical elasto-plasticity, kinematics of the continuum is represented by the reference R, intermediate B and current S states and local deformations are described by the multiplicative decomposition of the deformation gradient; F = F_e·F_p. Here, the reference and current states are Euclidean submanifolds while the intermediate state B is represented by Weitzenböck manifold with non-zero torsion in the affine connection. Following to the equivalence of torsion and dislocation density tensor through Hodge star operation, a plastic deformation gradient F_p is obtained from the Cartan first structure equation using the homotopy operator. The current state S is determined so that it minimizes the strain energy functional. We solve the variational problem by using isogeometric analysis; Galerkin method with non-uniform B-spline basis function. The present analysis shows that all stress components agree quantitatively well with those of the Volterra dislocation model. Around the dislocation core, stress fields are non-singular on the contrary to the Volterra dislocation. In addition, we found that all stress components distribute asymmetrically due to the geometrical nonlinearity of the model.

In the present report, we attempt to monitor the temperature of Cu direct laser drilling process of multi-layer printed circuit board with a high speed camera based on two color method and to construct a model of its process with a CFD (computational fluid dynamics). We look at the via-hole drilling using a CO₂ laser beam for the FR-4 type insulation layer, which made of glass fiber reinforced epoxy resin plastics, as build-up layer. First, we estimate the temperature distribution at the time line of process including the penetration of Cu layer on the surface and the cooling of drilled hole wall after laser drilling. Second, we discuss a CFD model for the drilling process based on finite volume method. As a result, it can be seen that the monitored results is in good agreement with the calculated ones by CFD model.

We tried laser slicing of (100) MgO wafer used as a substrate for heteroepitaxial growth of single crystal diamond. The laser slicing was successful by irradiating the inside of the material with an ultrashort pulse laser and generating a {100} cleavage. However, it was clarified that the cleavage of {100} was excessively extended and deviated from the slicing surface, so that steps of 20 μm were formed on the peeled surface. In order to reduce the kerf-loss, it was necessary to control the cleavage of {100}. Therefore, we proposed a scanning method to control cleavage and its extension. As a result, we succeeded in slicing a 2-inch MgO wafer with a kerf-loss of 30 μm.

In this study, the fundamental burnishing characteristics and quality of a molded product were evaluated during the sliding burnishing process with an active rotary tool developed by the authors was applied to the on-machine surface finishing of an aluminum mold for resin injection molding. The burnishing characteristics were mainly evaluated based on the surface profile, roughness, glossiness, material composition, and residual stress. The burnishing force increased with the indentation depth of the tool, and a constant fluctuation occurred according to the tool rotation cycle. Good burnished surface roughness and glossiness were achieved when the burnishing tool was fed at the same height as the cusp recesses on the preliminary surface. High compressive residual stress existed on the subsurface during the burnishing process, compared to the machined surface and polished surface, and the compressive residual stress increased with the indentation depth of the burnishing tool. The feed direction of the burnishing tool had a significant effect on the burnished surface quality, and the quality improved when the sliding directions of the tool rotation and tool feed were the same. The mold piece obtained from the burnishing process had almost same surface roughness as that obtained from the polishing process. The molded product quality obtained for these molds was similar to the mold surface quality, and the molded product obtained from the mold fabricated through the burnishing process had the same quality with that obtained through the polishing process. Based on these results, on-machine surface finishing of the injection mold was achieved using a general machine tool through position control by applying sliding burnishing with an active rotary tool.

Clarifying the mechanics of body movements during snowboarding, a popular winter sport, requires analysis of snowboarder motion when gliding down a slope. Several studies have used inertial and force sensors to evaluate characteristics of the acting force and joint torque of snowboarders. Nevertheless, few studies have examined the eye-tracking of a snowboarder. In daily life and sports activities, humans obtain most of their information about the external environment by vision. Therefore, analyzing the gaze of humans during sports activities is expected to improve performance on the sports field. For this study, we investigated relations between the line of sight and acting force during snowboarding, as measured using a gaze measurement system and two 6-axis force sensors, while a snowboarder glided down a slope. Lag times between movements of the line of sight and the associated acting forces of a snowboarder were calculated using a cross-correlation function for measurement information obtained from the experiment. Results show that the line of sight of a snowboarder moved to the forward pole on a slalom course before he generated the acting force necessary for making turns. The proposed method is expected to be useful for assessing snowboarders’ skills.

On-chip microdroplet-based electroporation is a newly developed process that enables droplet electroporation in a microfluidic device. If the process is to be realized at low cost, the electrode pair should be installed on the same plane. On the other hand, the electrode pair is installed as parallel plates in electroporation process with ordinary cuvettes. When the electroporation process is converted to a microfluidic device, the effect of electrode placement must be investigated because the electrode placement pattern is different from that of conventional electroporation. Therefore, numerical analysis of cell membrane perforation in micro rectangular channels was performed to support the design of an on-chip microdroplet-based electroporation system. The calculated geometry was given a state in which one cell was located in the center of the droplet. Since membrane perforation by a voltage pulse is a 1 μs time scale phenomenon, a numerical method was applied in which the electric field formation and membrane perforation are calculated in the same time step. The current conservation equation and the asymptotic Smoluchowski equation were coupled by the transmembrane voltage to calculate the time dependence. The calculation results showed that the position of high pore density on the cell membrane was slightly shifted compared to the case of electroporation by cuvette, but the position was almost ideal. And the pore density, electric field strength and transmembrane voltage distribution on the membrane showed accurate perforation locations and mechanisms. In addition, numerical analysis was also performed on the ideal parallel plane electrode assuming electroporation with a cuvette. It was shown that although the parallel planar electrode enables more efficient electroporation, the same planar electrode can also perforate the cell membrane at almost the same position. Finally, based on the results of 81 different calculations, the transitions in pore density and transmembrane voltage when cell is translocated are shown. The computing software COMSOL Multiphysics 5.4 on Windows OS was used on the workstation HP Z8 (CPU: Intel Xeon Gold 6128×2, Main memory: 96 GB).

To clarify the relationship between the downstream flow field of a windbreak fence and aerodynamic forces acting on a train placed downstream of the windbreak fence, wind tunnel tests with models were conducted. A 1/40-scale windbreak fence model (height H = 50 mm, hole diameter D = 0, 2, 6, and 10 mm, thickness T = 0.8, 1.6, 4.0, and 8.0 mm) and a vehicle model with square cross-section were used. Flow velocity and turbulence intensity were measured by PIV measurement. The pressure distribution around the train model was measured with differential pressure sensors. Effects of varying the thickness and hole diameter of the windbreak fence and the distance between the fence and the train on the flow fields and train aerodynamic characteristics are examined. As a result of the tests, pressure coefficients show that the pressure field on the upstream side of the train varies more considerably than that on the downstream side with varying the distance between the windbreak fence and the train. Hence, the variation of drag force is mainly caused by the change of pressure field on the upstream side of the train. The drag coefficient is minimized when the distance between the windbreak fence and the train is a certain value, which has been also shown in previous studies. In this study, the reason why the drag coefficient is minimized is clarified. Both averaged velocity and drag force acting on the train become lower as the ratio of fence thickness to hole diameter T/D becomes larger. Although T/D of real fences is about 0.1, T/D can be about 1 for wind tunnel tests. Hence, it is recommended that the ratio T/D of the fence model should be less than 1 for wind tunnel tests.

Large shock responses are generated at the deployment of solar paddles and antennas of a spacecraft because the strain energy of retained parts are released almost instantaneously. Therefore, the shock resistance of spacecraft instruments must be verified before launch. Specially designed separation mechanisms or explosive devices have been used for spacecraft separation, but shock testing using these devices is costly, so alternative methods such as mechanical impact testing are used. Adjusting the shock response spectrum (SRS) in these tests to desired values is a difficult task that requires considerable expertise. In this paper, we present a method for tuning an SRS. This method involves inserting a structure between the base plate of shock tester and the test specimen in order to modify the vibration propagation characteristics. Due to its easy implementation, this method can also be applied to other mechanical shock testers in use. In addition, a method for predicting the SRS using the transfer function synthesis method is also proposed to facilitate the adjustment of the test level.

This paper presents an approximate computing method of a shock response spectrum induced by a drop-weight shock test. The proposed method is based on a reduced impedance method, and computes the shock response spectrum by synthesizing the vibration characteristics of the spacecraft equipment and shock test device. A computational efficiency of the traditional reduced impedance method is significantly improved by proposing the method to only synthesize the dominated vibration characteristics of the substructures. The shock responses on the simplified model of the drop-weight shock test device are analyzed by the traditional reduced impedance method and the proposed method. Then, the shock response spectra given by both methods are compared. The result shows that the proposed method provides the shock response spectrum with accuracy of ±6dB for the traditional methods, and the computation cost is decreased by 1/60. This study offers a practicable approach to estimate an approximate shock response spectrum before a drop-weight shock test.