This paper presents a numerical procedure using shell element to evaluate the buckling behavior of the cylindrical structure subjected to pressure load. In numerical simulation for pressure vessels using conventional shell elements, the pressure loads imposed to both top and bottom surfaces are expressed as the difference between the internal and external pressures. In this work, the special shell element, in which the surface traction is exactly expressed at the surface, is applied to the buckling analysis. In this approach, the distribution of the transverse normal stress through the thickness can be evaluated. Therefore, the influence of the difference between the internal and the external pressures to the behavior of the buckling of the cylindrical shell structures can be assessed. In the situation that a perturbative load is applied under a certain stress state, bifurcation points are searched by solving a standard eigenvalue problem. Several numerical examples are presented to examine the effectiveness of the proposed approach. The buckling behavior that cannot be considered with the conventional shell elements can be observed by this approach.

Dissimilar T-lap joint between aluminum alloy 7075-T651 and 5083-H116 was fabricated by friction stir welding. Special focus was paid to the defect formation and mechanical properties which were significantly affected by the welding parameters. The results showed that four typical types of defects were detected in the T-lap joint; tunnel, kissing bond, hook, and bonding line defects. The tunnel and bonding line defects could be avoidable by decreasing the welding rate. At low welding rate, however, the hook defect was formed and reduced the skin effective thickness. The kissing bond defect was too hard to be eliminated by using one welding pass only by changing the welding parameters. Among these defects, the hook defect played the important role in the mechanical properties of T-lap joint. It is a special finding that there was the optimum welding rate by which the maximum joint efficiency was attained. These findings were summarized into the table and map which can optimize the joint properties.

This paper provides effects of furnace temperature conditions on the fracture toughness value of cleavage plane {110} on a single crystal silicon wafer. The fracture toughness K_IC was measured using the controlled surface flaw (CSF) method under an assumption to develop a thin crack introduced by a Vickers indenter. A system for evaluating four-point bending fracture strength under high temperature conditions was designed and constructed. This system can provide fracture strength under high temperature conditions for small plate specimens cut from the single crystal silicon wafer. CSF method needs to remove the surface layer, since residual stresses may be formed around the indentation mark and crack introduced by the indenter. Ion shower, can control micrometer order the removal surface layer, was applied for this analysis. An appropriate removal amount of the surface layer was confirmed based on effects of removal amount of surface on the fracture toughness in a room temperature condition. This result was applied for evaluations for the fracture toughness under various temperature conditions. Effects of furnace temperature condition on the fracture toughness and the fracture patterns were experimentally clarified in ranged over from room temperature to 600 °C. Above effects were compared with a result obtained from specimens without the removal process of the surface. Fracture's behaviors on the cleavage plane {110} of the single crystal silicon wafer in the high temperature range were discussed based on these experimental results.

A study to investigate contact detection and recognition of the cutting state by means of the acoustic emission (AE) technique in ultra-precision turning is presented. Detection of accurate cutting-edge position was achieved through investigation of the contact limit between the cutting edge and workpiece through use of the AE technique. Moreover, to recognize the cutting state, changes in AE signals instigated by corresponding changes in the cutting condition were monitored. In the contact-detection experiment, contact between the cutting edge and workpiece was detected with a cut depth of 10 nm. Likewise, in the cutting state recognition experiment, AE signal waveforms were observed to demonstrate changes corresponding to changes in the cutting state. These results confirm the feasibility of using the AE technique in cutting state monitoring experiments.

The prediction of muscle forces is very important in order to evaluate the physical loads during human motion. Although a number of musculoskeletal models, which can predict muscle forces during motion, have been proposed, these models use the optimization method, in which the sum of the predicted muscle forces is minimized. However, unfortunately, the optimization method does not usually consider the role of antagonistic muscles, which act in a direction opposite to the prime motion or for restriction of rotational joint motion. Therefore, the present study proposes a new method to predict muscle forces considering the role of the antagonistic muscle during human motion. The present study proposes a new model, in which the agonist muscle is assumed to be connected to the antagonistic muscle by a coupled spring. Joint torque is defined as the summation of both the torques derived from the agonist muscles and the torques derived from the antagonistic muscles. Each muscle force can be predicted in order to maintain balance among the torques generated by the agonist muscles and the antagonistic muscles, respectively. Experiments were conducted in order to validate the proposed method of predicting muscle forces. Surface electromyograms (sEMGs) were measured for comparison with the predicted muscle forces. The experimental results showed that the predicted muscle forces agreed well with the sEMGs of muscles.

The objective of this study was to simulate the swimming motion with bi-fins and investigate the effect of ankle joint motion by simulation. A model of a swimmer was constructed by utilizing the swimming human simulation model SWUM. The bi-fin was modeled as a series of five rigid plates. One rigid plate was connected to another by virtual springs and dampers. In order to determine the spring constants of the springs and damping coefficients of the dampers, static and dynamic bending tests were conducted. In order to determine the fluid force coefficients for the fin, an experiment in which the fin was located vertically in a pool and was moved horizontally by an air cylinder was conducted. In order to acquire the motion of swimming with fins, two swimmers were asked to perform maximal front crawl swimming with/without fins in an indoor swimming pool. The swimming motion was filmed by three cameras underwater and one camera on land. Using all of the input data, simulations reproducing the experimental trials were carried out. By the simulation, the developed simulation method was validated since the simulated swimming speeds were consistent with the experimental values in errors less than 6% of accuracy. By analyses with the validated simulation method, it was found that the smaller ankle joint movements resulted in a faster swimming speed. It was also found that the fixed angle of ankle joints affected the body pitch angle and that there is an optimum fixed angle for a swimmer to maximize swimming speed.

Soaking in bathwater has been a familiar custom for the Japanese for a long period of time. The authors discussed bathing comfort from the viewpoint of biomechanics in a previous study. However, it took a lot of effort to evaluate the joint torques during soaking in the water while conducting the experiments. Therefore, it was required to estimate the soaking postures and center of pressure (COP) in order to conduct the biomechanical evaluation with minimal experiments. The objective of this research was to develop an algorithm to estimate soaking posture and COP. In this study, it was assumed that a human took a soaking posture in the bathtub so as to minimize muscle exertion, that is, to minimize the joint torque as much as possible. Based on this assumption, an algorithm to estimate the soaking posture was constructed as an optimization problem of the objective function. An experiment was conducted for the purpose of validating the estimation algorithm. In this experiment, three kinds of bathtub shapes were tested for five healthy males. As a result, the estimated posture and COP were in good agreement with the measured one. The maximum error of the joint angle was 6.0% among all participants. The average values of the error in the location of the COP for each condition were 0.01 m or less. From the results of the present study, the possibility of estimation the joint torque is suggested.

In this study, it was analyzed how presenting information on the system safety level of automated driving system affects the driving behavior of driver, with the experiment using the driving simulator. During automated driving categorized to the level 2, we analyzed the driving preparation level of the drivers when presenting the system safety level on a display fixed on instrument panel. This driving preparation level of drivers was quantified, based on the gaze action and brake/gas pedal operation behavior of drivers, in a driving simulator investigation with 26 subjects' participation. As one of the experimental results, when system safety level was presented to drivers, the operation preparation level of the drivers increased instantly with the fall of the system safety level. We also quantified the effects by presenting system safety level in this driving simulator study. It was verified that the risk of the traffic accidents as Human-Machine system based on the state transition probabilistic model proposed by authors can be minimized when the system safety level was presented to the drivers. For instance, it was confirmed that the collision probability tended to reduce relatively by 37.9% with the indication of the system safety level.