High-speed Camera Research Articles

Innovation in physical education teaching based on biomechanics feedback: Design and evaluation of personalized training programs

Psychometric training is a learning and development process that is tied to the requirements and interests of individual learners. The effectiveness and the fun of workout practices can be greatly enhanced by using more personal methods in training. These programs entail tailoring workouts to the fitness level and aims of every participant, as well as their perception of the workout plans. The suggestion of this investigation is to develop and evaluate the effectiveness of individual physical training for teachers focused on biomechanics feedback. Proper body alignment is crucial during any exercise to avoid injuries and achieve maximum results; it is always difficult to sustain correct posture. For motion tracking and to give real-time biomechanics feedback to the students in this study, a refined convolutional neural network (RCNN) has been presented. Filming was done using high-speed cameras and motion capture systems to capture biomechanical responses, which included joint angle, muscle activation patterns, and body posture during activities. This study involved 158 participants drawn from different learning institutions. This approach offers rational and specific feedback on the postures of the body; it enables people to correct themselves and sustain motivation without engaging a trainer. In this study, participants with different levels of fitness engaged with the interactive system were compared to the traditional training method. The result indicated a positive shift in the delivery of personalized training with biomechanics feedback on the system’s potential teaching aid in physical education classes. The study, thus underscores the importance of technology supporting change in physical education programs to improve the student’s learning experiences and their performance in exercises.

Effect of sample temperature and laser ablation angle on optical emission and acoustic signals from laser-induced zirconium plasma

A fiber-coupled, acoustic-wave-assisted (AW) microchip laser-induced breakdown spectroscopy (mLIBS) system was developed to analyze the elemental composition and surface imaging. In this study, we measured the dependence of sample temperature and laser ablation angle (LAA) on the laser-induced plasma–optical emission (LIP–OE) and LIP–acoustic signal (LIP–AS). The intensity of the LIP–OE and ablated mass at three different temperatures and eight different LAAs were estimated using a zirconium sample. Simultaneously, we investigated the LIP–AS amplitude, propagation speed, and shape by synchronizing the AW-mLIBS system with a high-speed camera. The results revealed that the LIP–OE increases with increasing temperature and is unaffected by LAA up to 40° because the amount of the ablated mass was similar to the plasma. Additionally, no considerable variation in plasma temperature was obtained using the Boltzmann method over the sample temperature. However, the propagation speed of the LIP–AS differs with temperature but has marginal angular dependence because the LIP–AS propagates as semispherical. Furthermore, no considerable changes were observed in the LIP–AS amplitude up to 100°C, and the LAA showed a similar tendency to that of the LIP–OE.

Development of a DualEmission Laser-Induced Fluorescence (DELIF) Method for Long-Term Temperature Measurements

The fluorescence intensity of fluorescent dyes typically employed in the dual-emission laser-induced fluorescence (DELIF) method gradually degrades as the excitation time increases, and the degradation rate depends on the type of fluorescent dye used. Therefore, the DELIF method is unsuitable for long-term temperature measurements. In this study, we focused on the fluorescence intensity ratio of a single fluorescent dye at two fluorescence wavelengths and developed a DELIF method for long-term temperature measurements based on this ratio. The fluorescence intensity characteristics of Fluorescein disodium and Rhodamine B, which are typically used in the DELIF method, in the temperature range of 10–60 °C were comprehensively investigated using two high-speed monochrome complementary metal-oxide semiconductor cameras and narrow bandpass filters. Interestingly, the ratio of the fluorescence intensity of each fluorescent dye at the peak emission wavelength of the fluorescence spectrum, λ, to the fluorescence intensity at wavelengths very close to the peak wavelength (λ ± 10 nm) was highly sensitive to temperature variations but not excitation time. Particularly, when Rhodamine B was used, the selection of the fluorescence intensity ratios at a wavelength combination of 589 and 600 nm enabled highly accurate temperature measurements with a temperature resolution of ≤0.042 °C. Moreover, the fluorescence intensity ratio varied negligibly throughout the excitation time of 180 min, with a measurement uncertainty (95% confidence interval) of 0.045 °C at 20 °C. The results demonstrate that the proposed DELIF method enables highly accurate long-term temperature measurements.

Fracture Mode and Thermal Damage Evolution of Sandstone Under the Coupling Effect of Thermal Treatment and Impact Load

The dynamic properties of high-temperature sandstone quickly deteriorate with different cooling methods, which leads to the instability of underground engineering rock structures. Therefore, it is of great significance to quantify the changes in the dynamic characteristics of high-temperature cooled sandstone under impact loads. Therefore, the sandstone is heated to different temperatures and cooled using three methods. A dynamic tensile test is performed using the Splitting Hopkinson Pressure Bar (SHPB) test set for high-temperature cooled sandstone. At the same time, the transient process of rock failure was examined using high-speed cameras. The influence of different temperatures and cooling methods on the thermal damage value of sandstone was analyzed, and the prediction equation was formed. The change in rock energy during rock failure under impact load was calculated.

Vapor Channel Oscillations in Laser Lithotripsy.

Laser-based endoscopic procedures present special challenges to deliver energy for ablation or coagulation of target tissues. When optical fiber-target quasi-contact (< 0.5 mm distance) cannot be maintained or is undesirable, the creation of intervening vapor bubbles and channels provide for the necessary transmission of laser energy to the target. This work investigates the characteristics and the dynamics of vapor channels that directly affect ablation efficiency and ablation rate and are known to effect stone movement, all of which impact procedure efficiency and safety. A simplified, experimental model for thulium fiber laser (1940 nm) lithotripsy consists of a water-filled cuvette and a vertically oriented laser fiber (200 μm core diameter) with its tip at 9 mm for "quasi-free" bubble generation and at vapor channel working distances 1-5 mm from and centered on the transparent cuvette bottom simulating a target's surface. Laser power transmission is recorded and synchronized with video frames from a high-speed camera (24,260 frames per second) to capture the induced vapor channels' and bubbles' development. Laser-induced channel transmission from 0% to 100% for 1, 2, and 3 mm fiber-target distances undergoes oscillations with average periods of 0.32, 0.64, and 1.0 ms, respectively, for 500 W laser output power. For fixed fiber-target distances of 0.5, 1, and 2 mm, the variation of these average oscillation frequencies across laser powers from 500 to 1000 W is much smaller, not exceeding 14%. For fiber-target distances in the range of 1-5 mm, the fraction of the 500 W laser's total pulse energy delivered to the target for 1, 2, and 3 ms pulses linearly decreases from 0.78 to less than 0.2. The channel and bubble dynamics begin with a spherical seed bubble expansion centered on the distal fiber tip that evolves into a pear shape whose surface exhibits periodic irregularities attributable to laser beam interruption by water droplets within the developing bubble. The study of laser-induced channel oscillations provides quantitative information relating fiber-target distance to channel oscillation frequency and energy transmission onto a target. These oscillations directly effect ablation efficiency and ablation rates that are important parameters for the optimization of a procedure's safety and duration. Insights that may lead to further reduction in retropulsion are also presented. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.

Multiscale Modeling and Simulation of Falling Collision Damage Sensitivity of Kiwifruit

Falling damage is the most common form of damage sustained by kiwifruit during the process of picking and post-processing, and it is difficult to conduct a quantitative analysis of this phenomenon through traditional experimental methods. In order to deeply understand the sensitivity of kiwifruit to falling collision damage, the finite element numerical simulation method was used to evaluate and predict the sensitivity of kiwifruit to falling collision damage during harvesting. First, we obtained the appearance characteristics of kiwifruit through reverse engineering technology and determined the geometric and mechanical property parameters of kiwifruit through physical mechanics experiments. Then, according to the characteristics of fruit tissue structure, a multiscale finite element model, including the skin, pulp, and core, was constructed to simulate the effects of different falling heights, collision angles, and contact surface materials on fruit damage, and the accuracy of the model was verified through falling experiments. Finally, based on the simulation results, the Box–Behnken design was employed within the response surface methodology to establish a sensitivity prediction model for the drop damage sensitivity of kiwifruit across different contact materials. The results showed that the maximum relative error between the speed change obtained using finite element simulation and the speed obtained by the high-speed camera was 5.19%. The model showed high rationality in energy distribution, with the maximum value of hourglass energy not exceeding 0.08% of the internal energy. On the contact surface material with a large elastic modulus, a higher falling height and larger collision angle will significantly increase the risk of fruit bruise. When the contact surface material was a steel plate, the falling height was 1 m, and the collision angle was 90°; the maximum bruise sensitivity of kiwifruit reached 6716.07 mm3 J−1. However, when the contact surface material was neoprene, the falling height was 0.25 m, and the collision angle was 0°, the damage sensitivity was the lowest, at 1570.59 mm3 J−1. The multiscale finite element model of kiwifruit falling collision constructed in this study can accurately predict the damage of kiwifruit during falling collision and provide an effective tool for the quantitative analysis of kiwifruit falling collision damage. At the same time, this study can also provide guidance for the design and optimization of the loss reduction method of the harvesting mechanism, which has important theoretical significance and practical value.

Flow behavior and heat transfer characteristics of liquid film on vertical hot surface by inclined jet impingement

In this study, the flow behavior and heat transfer characteristics of the liquid film on the hot wall by inclined jet impingement are experimentally studied in detail. The effects of jet parameters, such as jet inclination angle, impingement distance, jet Reynolds number (Rej), and nozzle diameter are explored. The liquid film flow is visualized using a high-speed camera, and the surface temperature and heat flux are obtained by solving the inverse heat conduction problem. The results indicate that the liquid film shape is strongly affected by jet inclination angle but is almost unaffected by other parameters. As the inclination angle increases, the liquid film shape changes from elliptical to fusiform. In addition, the onset, enhancement, and disappearance of boiling cause the expansion and contraction of liquid film. The splashing rate is barely affected by jet parameters and remains within the range of 80–95 % under all conditions. The propagation of wetting fronts exhibits anisotropy. Except for the impingement distance, the position of wetting fronts along y-axis direction displays a high dependence on all parameters. The Rej and nozzle diameter have a significant effect on the heat flux at the impingement point and parallel flow zone, while the jet inclination angle and impingement distance only effect the impingement point. The visualization image proves that the droplet impingement pattern is the main reason for the increase in heat flux at higher impingement distances. Optimizing jet parameters can promote the wall to enter the rapid cooling stage in advance and increase maximum heat flux, thereby improving the maximum cooling capacity of the jet. Finally, an empirical equation is proposed to predict the maximum Nusselt number.

Study on aerodynamic breakup of non-Newtonian liquid droplets and the distribution characteristics of their sub-droplets

In industrial applications, the secondary breakup of droplets and the size distribution of their sub-droplets are crucial for atomization performance indicators. In this work, a high-speed digital camera is utilized to experimentally and theoretically study the secondary breakup process of xanthan gum (XG) droplets and the size distribution changes of resulting sub-droplets in continuous airflow by changing the Weber number and effective Ohnesorge number. In addition, a detailed study is conducted on the liquid ring with the highest liquid content. The results show that at low Weber numbers, the number of nodes generated at the XG droplet ring is the same as that of the water droplet, following “the combined R-T/aerodynamic drag” mechanism. However, the final diameter of the nodes differs significantly from that of the water droplet. The particle size of XG liquid ring nodes is not only affected by the Weber number but also decreases with the increase of the effective Ohnesorge number. The particle size of the remaining broken sub-droplets in the liquid ring decreases with the increase of the effective Ohnesorge number. Finally, the spatial range of droplet breakup under different parameters is described by using the liquid ring breakup angle, and it is found that the breakup angle of the liquid ring is mainly related to the breakup mode.

Binary collision dynamics of immiscible Newtonian and non-Newtonian fluid droplets

This experimental and theoretical study is devoted to the investigation of head-on collisions of two immiscible Newtonian and non-Newtonian droplets. The density of the two droplets is similar, and the viscosity of 0.3% carboxymethyl cellulose droplet is slightly larger than 10 cSt silicone oil. The sizes and relative velocity of the colliding droplets close to the point of impact are measured by means of image processing. The deformed states after the impact and their evolution with time are studied by experimental visualization and the energy evolution with time are discussed by numerical results. The accuracy of the two-dimensional axisymmetric three-phase flow computational model is validated. We study the effects of collisions of non-Newtonian droplets with Newtonian droplets and the subsequent retraction kinetics. Droplet “cannibalization” is commonly observed: after collision and spreading, the droplet retracts rapidly, resulting in a Newtonian droplet wrapping around a non-Newtonian droplet. We show the whole process of droplet collision captured by a high-speed camera and obtain the cloud and velocity vector maps of the droplets by numerical simulation. The droplet wrapping phenomenon is produced by different three-phase interfacial tensions and viscosities. We delineate the different phases of the collision process and discuss the dominant forces in each phase. We calculate the energy evolution of the spreading phase and use it to derive a predictive model for the dimensionless maximum spreading diameter and spreading time.

Wave mode observation of hydrogen/oxygen driven rotating detonations in the hollow and annular rotating detonation rocket engine

The rotating detonation rocket engine (RDRE) fueled by hydrogen/oxygen propellant represents a promising propulsion technology due to its high thermodynamic efficiency and propellant superior specific impulse. The rotating detonation wave (RDW) must propagate in a specific propagation mode while maintaining the self-sustaining state to ensure stable operation. An experimental system of hydrogen/oxygen fueled RDRE was developed in the present study. The operation of RDRE and propagation mode of RDW were investigated under atmospheric pressure conditions, and both hollow and annular combustors were tested. The high-frequency pressure fluctuations in the RDRE were measured by the dynamic pressure transducer, while a high-speed camera was used to capture images of flame luminescence at the rear end of the RDRE. The experimental results showed that the RDW could be initiated and reached a self-sustaining propagation state with hydrogen/oxygen propellant in the hollow and annular RDRE. A single-wave mode, a two-wave co-rotating mode, and a three-wave co-rotating mode were visualized under different conditions. With the increase in the equivalence ratio, the number of rotating detonation fronts decreased, and the variations in the RDW propagation modes were consistent in the hollow and annular RDRE. However, when the equivalence ratio exceeds 1.2, the propagation velocity decreases sharply in the annular combustor, while in the hollow combustor the RDW propagates stably, revealing a higher upper limit for the equivalence ratio. Also, the dominant frequency distribution was more concentrated in the hollow combustor. The findings provide valuable insight into the variations in detonation modes related to the equivalence ratio and combustor configuration.

Dynamic visualization study of in situ cleaning of polystyrene microparticles off silicon wafer surface

With the improvement of chip performance, the requirements for cleaning the surface of silicon wafers are becoming higher. However, due to equipment and technology, it is difficult to observe the complex motion processes of particles at the microscopic scale. In this paper, an in situ dynamic visualization experiment on the cleaning of Polystyrene Latex (PSL) on the surface of silicon wafers is carried out by using a high-speed camera and image processing software. The mechanical behavior of PSL particles in fluid was investigated on a microscopic scale, and the trajectory and force of the polystyrene particles on the surface of the wafers were visualized, which provided a new perspective for understanding the complex cleaning process. Theoretical models were developed to explain the motion characteristics of the particles by calculating parameters such as van der Waals force, surface tension, and trailing force, and these models provide a theoretical basis for optimizing the cleaning process. There are four particle motion modes in the fluid: (1) interface capture, where the particles on the surface of silicon wafer are trapped by gas–liquid interface under surface tension; (2) particle collision, where the particles captured by the water film collide with the particles on the wafer surface to make the latter leave the silicon wafer; (3) jump attachment, where the particles jump and attach to the surface of the particle group under the action of lift; and (4) wall surface movement, where the particles start up under the action of water flow and then leave the silicon wafer quickly.

Distribution of bone fragments in angled shots: an experimental study conducted on composite models containing artificial bone plates.

In conventional gunshot injuries to targets containing bone the resulting osseous fragments do not precede but follow the bullet on its further way through adjacent soft tissues. The term "secondary projectiles" for the particles does not appear to be appropriate since they are not believed to have enough energy necessary for creating their own wound channels away from the temporary cavity. Former studies have shown that in angled shots to glass panes the bulk of splinters does not follow the bullet's trajectory: The majority of the glass fragments, especially the larger ones, move at right angles to the pane shot through. The aim of the presented study was to examine whether osseous fragments behave like glass splinters in angled shots to flat synthetic bone. In this context, it should also be assessed, whether the bone fragments might act as secondary projectiles in rare cases. To answer these questions, test shots were fired to composite models consisting of flat synthetic bone and ballistic gelatin. Pistol cartridges 9mm Luger were used to fire the shots which were video-documented with a high-speed camera. Afterwards, the composite models underwent CT examination and macroscopic inspection. Video-documentation revealed that the larger bone particles from the perforation site move at a roughly right angle from the osseous sheet into the gelatin, causing an eccentric bulge of the temporary cavity. The smaller bone fragments were also lodged along the bullet's path, predominantly in the cracks radiating from the permanent wound channel.

Fragmentation behavior and velocity formula for secondary fragments from RC slabs during contact explosions

The failure process of reinforced concrete (RC) slabs under contact explosion is dominated by localized damages, accompanied by numerous flying fragments. These concrete fragments pose a significant threat to personnel and equipment, as well as causing dynamic deformation and failure of the retrofitting materials used to restrain the fragments. The behavior of concrete fragmentation during explosions has been seldom studied experimentally, and few fragment velocity formulas exist that incorporate multiple factors. In this paper, the fragmentation process is recorded using two high-speed cameras, revealing that concrete fragmentation during explosions exhibits notable zoning characteristics, with the maximum velocity observed at the center of the fragment cloud’s front. To predict this maximum velocity, a model is derived from dimensional analysis. Utilizing this model, velocity prediction formulas are proposed and validated by 29 contact explosion tests. The formulas consider the explosive-rebar position, slab thickness, explosive mass and explosive shape, and are further improved by considering the concrete cover. The results indicate that, when the slab is not breached, the deceleration of rebar on fragments is weak. However, once the slab is breached, this deceleration becomes increasingly significant as the defined scaled thickness (TS) decreases. In the limiting case, the fragment velocity when the charge is located above the rebar is 0.636 times that of when the charge avoids the rebar. Fragments when the charge avoids the rebar, should be regarded as the most unfavorable case in secondary fragment hazards assessment and structural design.

Effect of settling vortex of coal slime flocs with different sizes on the settlement of microfine particles

This article explores the flow field changes and micro vortex formation mechanisms caused by coagulation and sedimentation of coal slurry flocs of different sizes. The collision adhesion rate, motion trajectory and force analysis of fine particles under micro vortex disturbance. Particle image velocimetry (PIV) and high-speed camera were used to capture deposition process of coal slime flocs, the changes of flow field and fine particles were analyzed by numerical simulation. The smaller flocs form a single vortex ane larger flocs show periodic vortex shedding, resulting in increase fluid velocity and larger interference area. The collision adhesion rate of fine particles in the 3.4 mm floc settling disturbance area is the largest, 9.45 %;Particles<0.3 mm are easily sucked into vortices, while particles>0.3 mm are disturbed by vortices and change their motion trajectory towards the vortex center. It is mainly affected by gravity, pressure gradient force, flow field resistance, and centrifugal force.

Tip clearance influence on the performance of high-speed micro-pumps

The fast-paced development of the aerospace and shipping industry is promoting the development of lightweight and high-speed transfer pumps. High-speed micro-pumps with semi-open impellers are highly sensitive to tip clearance (TC), which crucially influences the head and efficiency. This study proposes a new design for a high-speed micro-semi-open impeller centrifugal pump with a 19 000 rpm rotational speed and 30 m hydraulic head. The performance of the proposed centrifugal pump under different inlet corrosion allowances and different impeller TC ratios (0.05, 0.08, 0.11, and 0.14) is investigated through numerical simulations and experiments. The interaction process between the leakage and main flows in the tip gap is recorded with a high-speed camera and is numerically calculated. The stability of the internal flow field is optimal under smaller TCs. This study provides the optimal TC and guidance for designing high-speed micro-pumps.

Identification of flow patterns in an opaque condenser tube by distributed fiber Bragg gratings

Two-phase loops with phase change heat transfer are pivotal for cooling electronics under high heat flux and for thermal control in spacecraft. Numerous studies aim to clarify the mechanisms behind these loops to enhance cooling capacity and stability, which are closely tied to flow patterns. However, conventional flow pattern identification methods, requiring transparent tubes for direct observation, are impractical for simultaneous heat transfer measurement, especially during condensation. This paper introduces a novel approach for identifying flow patterns within an opaque, vertical condensation tube using embedded distributed fiber Bragg gratings (DFBGs) for R134a. The method involves a “fingerprint” derived from temperature profile derivatives and additional criteria based on temperature variation characteristics. These include the relative deviation from saturation temperature, the relative spatial temperature gradients, and the relative amplitude of temperature fluctuations. Validation against high-speed camera images confirms the method’s efficacy. It enables the determination of flow pattern lengths, the endpoint of condensation, and the construction of a flow regime map. Additionally, it allows for the measurement of vapor velocity in slug flow, facilitating the calculation of slip ratio and void fraction, which correlates reasonably with the Zuber-Findlay model, with systematic positive deviations up to 30%. This method also paves the way for simultaneous measurement of in-tube condensation heat transfer characteristics for various flow patterns.

Flash evaporation in a superheated liquid pool using water as medium

This paper proposes a fast cooling technology called flash evaporation or flashing to overcome cooling problems. Flashing is a pressure-driven phase change phenomenon widely studied because of its complex physics and numerous applications. An experimental system is fabricated to study the efficiency of the proposed process by considering water as a working fluid. A transparent acrylic column is used as the flash chamber, enabled with a high-speed camera to visualize and capture this fast and complex process. Experiments have been carried out with various initial temperatures from 65 °C to 80 °C, initial vacuum tank pressure ranging from 11.32 kPa to 41.32 kPa, and initial water heights of 80 mm and 140 mm. The flashing phenomenon is divided into two stages based on its xeffectiveness. From the present study, it becomes apparent that the drop in the temperature increases with the initial temperature and decreases with increasing vacuum tank pressure. The cooling rate is improved by 49.1% by increasing the initial pool temperature by 23%. The present study demonstrates an effective application of the flashing process in areas requiring high cooling rates and rapid vapour generation, such as refrigeration and drying.

Methyl ricinoleate droplet impact on a high temperature stainless steel surface: Dynamic behavior and heat transfer

The rapid and uniform heating of the feedstock plays a key role in pyrolysis processes. Dispersing methyl ricinoleate (MR) into spray droplets can improve the heating speed and uniformity in the pyrolysis process, which is of great benefit to the yield of the target product. This article describes the results and mechanisms of single MR droplet impacting on a heated stainless steel surface at different temperatures (385 ∼ 520 °C). Two non-contact measurement techniques, including a high-speed camera and a thermal infrared imager, were used to record the dynamic behavior and heating effects of the MR droplet on the heated surface at different temperatures, respectively. Four representative impingement states were observed during droplet impact: adhesion rebound, adhesion rebound with breakup, bouncing, and bouncing with breakup. As a result, a comprehensive map was created, based on a dimensionless analysis, describing the relationships between the typical states. Regarding the quantitative analysis, the maximum spreading factor and the dimensionless droplet residence time were linearly related to the 0.336 and 0.389 powers of the Weber number, respectively. By calculating the average heat flux of a droplet, it was found that it is related to the stainless steel surface temperature, the droplet saturation temperature, and the Reynolds number. The transient temperature at the surface of the MR droplet was measured to quantify the effectiveness of the heating. This study could provide a theoretical basis for the regulation and optimization of MR pyrolysis conditions.

A study of measurement of raceway direct measurement of rolling bearings

Demands for improved fuel efficiency in automobiles and other vehicles have led to smaller, lighter power transmission device which result in high surface contact stress and a thin oil film, which in turn tends to cause the temperature of rolling bearings to rise. The most common temperature measurement method is to touch a thermocouple against the inner and outer rings, and this method has been used for many years. However, the method using thermocouples can only measure temperatures in a limited range near the measurement point. The authors applied the Seebeck effect, a phenomenon in which an electromotive force is generated when different metals are connected and a temperature difference is applied to bearings, to a method of measuring bearing raceway temperatures called the dynamic thermocouple method. In the dynamic thermocouple method, the average value of each contact points between the different metals generates the emf (electromotive force), so the temperature rise of all the each rolling elements in contact becomes the average value, and the exact point of temperature rise is not clear. Therefore, all but one rolling element was changed to electrically insulating zirconia balls. With this method, the contact points between many different metals became one, making it possible to identify the locations of temperature rises on the raceway surface. This method makes it possible to directly measure the temperature change of the raceway. The results of temperature measurements of the raceway surface using two types of bearings with different raceway accuracy showed a clear difference of temperature. The bearing with a poor raceway accuracy showed a temperature rise in the unloaded zone, and slippage was observed when the behavior of the rolling element was checked with a high-speed camera. Furthermore, in bearings with good raceway accuracy, the temperature of the raceway surface remained almost constant even in the non-load zone. By using the dynamic thermocouple method and observing the rolling elements with a high-speed camera, it was possible to correlate the bearing temperature rise with the behavior of the rolling elements.

An Experimental Study of Wave Impact Loads on an FPSO Bow in 2D Wave-Tank

&lt;i&gt;In harsh environments, an floating production storage and offloading (FPSO) is occasionally damaged by impact loads, such as bow flare slamming and green water. This study conducted an impact load measurement experiment on a model of an FPSO bow in a 2D wave tank. Three types of frequency-focused waves (steep, spilling, and plunging) were generated, and the speed and slope of the waves were measured. Seven wave probes were placed in a row, and the wave elevation was measured to determine the speed and slope of the waves. In addition, the side of the 2D wave tank was photographed with a high-speed camera. The speed and slope of the waves obtained from the wave probe array agreed well with those obtained from the photographs taken using a high-speed camera. In the case of a steep wave, wave runup occurred at the bow before the wave reached the bow of the FPSO, so no impact load was generated, and only hydrostatic pressure was measured. Impact loads were generated in the spilling and plunging waves, and the magnitude of impact loads using the Von Karman’s estimation formula and the impact loads measured in model tests showed similar values.&lt;/i&gt;