In order to improve the accuracy of fatigue life predictions for power modules under future operating conditions, fully-reversed cyclic bending test method was developed for aluminum wires with a diameter of 0.4 mm. The tests were conducted at a temperature of 175 degrees with frequencies of f = 10, 4, 1, 0.4 and 0.1 Hz, and the fatigue life increases with increasing f. When f was converted to the operating time of the power module, t_on, it was observed that the slope α of t_on and fatigue life on a double-logarithmic scale decreases with increasing t_on, approaching 0. For power modules operating at 175 degrees, α is a function of t_on, and incorporating this relationship enables accurate fatigue life prediction.

To ensure the strength and safety of shafts, which are basic components of machines, it is important to accurately evaluate the stress concentration factor (SCF) of stepped round bar fillets. Noda et al. analyzed the SCF of stepped round bar with fillet under tension and bending by using the body force method and proposed SCF formulas valid for all dimensional ranges. These formulas are very useful in design practice. Since shafts generally transmit power, the SCF of torsion is also important, but there is no solution for the torsional SCF that is valid for all dimensional ranges. In this study, therefore, the stepped round bar subjected to torsion is investigated for all dimensional ranges. The finite element method for an axisymmetric body subjected to a non-axisymmetric load is applied to torsional problems by confirming the coincidence with the SCF solution by the body force method for a round bar with a semicircular notch under torsion. The SCF formula proposed for all dimensional range under torsion shows that SCF charts in literature commonly used in design practice have large errors about 10% because they are based on old research results. Peterson's SCF equation is simple and useful, but the application range of the equation for torsion is extremely narrow and inconvenient to be used in machine design.

Due to rapid changes in the market and various customer values, it is necessary to shorten the development period of automobiles. Vehicle performance has been improved mainly through experimental analysis and CAE (computer aided engineering). In the increasingly rapid development of vehicles, machine learning is taking the lead. Vehicle performance prediction usually involves constructing surrogate models using design parameters and CAE results. However, three-dimensionally complex vehicle shapes cannot be fully represented by design parameters. Additionally, reducing vehicle drag has become even more important with the rise of battery electric vehicles. While balancing design and vehicle performance, complex three-dimensional shapes are explored to find optimal solutions, which requires a substantial amount of effort. For predicting vehicle drag performance, a method using variational autoencoder (VAE) is proposed to predict the shape of the vehicle front bumper side, drag coefficient, and flow field on the side and rear of the vehicle. With the proposed method, the drag coefficient was predicted with a maximum error of 0.012, an average error of 0.002, and an R² value of 0.88, demonstrating good agreement with CFD (computational fluid dynamics). Additionally, the predicted velocity magnitude distribution on the side and rear of the vehicle is similar to CFD results. By creating a scatter plot (map) of the latent variables of the proposed method using principal component analysis results, it was found that the direction of increase in the first and second principal components corresponded with the increasing trend of the drag coefficient. Using this map, it becomes possible to predict the drag coefficient, velocity magnitude distribution on the side and rear of the vehicle, and vehicle shape derived from the proposed method. By using the proposed method, it is possible to suggest three-dimensional shapes that were not represented by traditional design parameters, making it easier to balance design and performance and thereby facilitating the search for optimal solutions.

An aerodynamic brake is a device that is aimed for increasing air drag to obtain brake force by expanding plates. As proposed by Takami (2013), multiple plates are distributed on the train roof. In this arrangement, many devices are installed in the wake of the most upstream device. In the wake, where the flow is slow, the devices are difficult to gain drag force. Thus, to obtain efficient drag force in this method, it is desirable to rearrange all the devices so that they are subjected to a higher velocity flow. For this purpose, it is important to understand the influence of the device arrangement on the obtained drag, and this drove us to perform a computational flow analysis on flat-plate-modeled aerodynamic braking devices. Specifically, the flat plates are placed in the staggered layout and the clearance between the flat plates (in the crossflow direction) was parametrically varied. Then, their impact on the magnitude of drag force and the flow field were investigated. As a result, by decreasing the clearance between the flat plates from 50 % to 0 % of its width, drag force increased by 11 % because the flow velocity behind the plates easily recovered so that faster flow hits the plates located downstream.

As part of a study to improve the efficiency of two-phase flow systems using HFO refrigerants, a correlating equation for predicting heat transfer coefficient has been proposed. In particular, the separation angle, which is the boundary between the liquid and gas phases, is an important parameter in the equation for separated flow in a horizontal tube, and it is expected that a more accurate prediction model for the wetting boundary angle can be verified by measuring the temperature distribution using an infrared camera. In this study, a horizontal tube heating apparatus was constructed with a heating test section and a transparent heating apparatus as visible sections to conduct the temperature measurement of the boiling flow of refrigerant R1336mzz(E) by a high-speed infrared camera and visualize the boiling flow pattern by high-speed camera. In the experiments, heat transfer coefficient and frictional pressure drop were measured using horizontal circular tube with an inner diameter of 10.0 mm and the flow pattern was observed at mass fluxes of 100 to 300 kg/(m²∙s) and inlet heat fluxes of 2.1 to 19.3 kW/m². Wavy flow and transition flow to dry-out were observed at low mass fluxes, and slug-wavy, intermittent, and annular flow were observed at high mass fluxes. The heat transfer coefficient and frictional pressure drop gradient were close to the values of the previously correlated equations for the flow pattern stabilized with increasing quality, and these results were reasonable. In the spatial-temporal temperature fluctuation measured by a high-speed infrared camera, the maximum value of the temperature fluctuation was confirmed in the circumferential direction. The temperature fluctuation measurement using a high-speed infrared camera is considered to be a new method to evaluate the separation angle with high accuracy.

The Pure Pursuit method has been widely used as a standard approach in many autonomous vehicles due to its ease of implementation and low computational cost. However, there is a trade-off between responsiveness and preview distance: while a longer preview distance is necessary to accommodate sudden changes in the reference trajectory, increasing this distance reduces the responsiveness of trajectory tracking. This trade-off arises from the dynamic characteristics of the trajectory tracking system when using the Pure Pursuit method. However, no prior studies have attempted to improve these dynamic characteristics by interpreting the system as a vibratory system. In this study, we aim to resolve the fundamental issues of the Pure Pursuit method while retaining its advantages, such as ease of implementation and low computational cost. Specifically, we propose adding an additional preview point ahead of the vehicle, enabling control over both the natural frequency and damping ratio. We provide a detailed explanation of this method and its practical application.

This paper presents a topology optimization method for minimizing power dissipation while constraining the maximum temperature in thermal-fluid systems. The advantage of the proposed optimization is its ability to accurately approximate the maximum temperature constraint as a continuous function. It is necessary to solve the complex interaction between thermal and fluid dynamics multiphysics problems in the fixed design domain. The p-norm measure to approximate the maximum temperature constraint is employed to address these challenges, and the coupled Navier-Stokes and energy conservation equations for incompressible viscous flow are solved in forced convection. The proposed method employs a density-based approach, with design sensitivities computed via the adjoint variable method. The finite volume method (FVM) is used to solve both the state and adjoint equations, while the method of moving asymptotes (MMA) updates the design variables. Through several numerical examples, the effectiveness of the proposed method in handling complex thermal-fluid optimization problems is demonstrated. Compared to existing approaches, our method contributes to the optimization of thermal-fluid systems, making it a promising tool for industrial engineering applications.

In this paper, effectiveness of the headrest which can be attached to the assist device for upward work was investigated based on the static and dynamic analyses. In the static analysis, the cervical spine load model was proposed and static strain on the cervical spine was evaluated. As a result, the moment around C2/C3 disc and the compressive force and shear force on C2/C3 disc were reduced in the presence of the headrest. The dynamic analysis was conducted using the musculoskeletal model analysis software AnyBody Modeling System (AnyBody). First, arm lowering movement was created using the code of AnyBody. Then, dynamic strain on the cervical spine was analyzed for the created movement. As a result, activity of the sternocleidomastoid muscle, the compressive force and shear force on C2/C3 disc under wearing the assist device with the headrest were reduced as compared with those under wearing the assist device without the headrest. Therefore, usefulness of the headrest for reducing the burden on the neck during the upward work was verified.

In recent years, low back pain(LBP) among manufacturers has become a problem. One causes of LBP is the lifting of loads. It has been confirmed that the stoop lifting, where the object is lifted by bending forward with extended knees, puts more strain on the lower back than squat lifting, where the back is straight and the knees and hips are flexed. In addition, it is recommended that men over 18 handle loads of about 40% or less of their body weight, so knowing the object’s weight is important. In this study, we propose a method to determine if the weight of the grasped object is 10 kg or 20 kg immediately after lifting, using a 9-axis sensor attached to the chest and the stoop lifting, which is considered to have a large load on the lower back. A linear approximation was made based on the most recent 0.2s data of the forward tilting angle calculated from the 9-axis sensor measurements, and the change in the tilt was obtained by repeating this process. The difference and maximum of the extreme values at the start of lifting were calculated from the change in inclination, and the amount of grasped material was discriminated against by k-fold cross-validation using a nonlinear Support Vector Machine (SVM) with these two as the feature values. The discrimination accuracy was 82.3%, 7% higher than that of the conventional method calculated under the same conditions. It is necessary to conduct further validation using different lifting methods, known masses, and smaller mass differences in the future.

Spacecraft systems are exposed to a random and non-stationary acoustic environment inside the rocket fairing during launch, necessitating acoustic testing to verify their vibro-acoustic resilience. The conventional approach for deriving stationary acoustic environment conditions for these tests typically employs octave band analysis based on the short-time Fourier transform (STFT). However, this method has been criticized for its inadequacy in ensuring equivalence in extreme response and cumulative fatigue experienced by the test structure. The authors previously proposed a method for deriving stationary acoustic environment conditions by applying the extreme response spectrum (ERS) and the fatigue damage spectrum (FDS), ensuring that the extreme response and cumulative fatigue induced in the structure are equivalent to those caused by a non-stationary acoustic environment. However, this method relies on the assumption that the distribution of extreme responses follows a Rayleigh distribution, which may not always guarantee equivalence when the vibration response exhibits a broadband random process. This study proposes a new method for adjusting the sound pressure spectrum to ensure equivalence in extreme response and cumulative fatigue between the stationary and non-stationary acoustic environments. The proposed method was applied to flight telemetry of acoustic pressure inside an actual rocket fairing, demonstrating its capability to derive more appropriate stationary acoustic environment conditions with respect to ensuring equivalence in extreme response and cumulative fatigue to a non-stationary acoustic environment.