Acceleration Force Research Articles

Subaxial Cervical Spine Motion With Different Sizes ofHead-supported Mass Under Accelerative Forces.

The evolution of military helmet devices has increased the amount of head-supported mass (HSM) worn by warfighters. HSM has important implications for spine biomechanics, and yet, there is a paucity of studies that investigated the effects of differing HSM and accelerative profiles on spine biomechanics. The aim of this study is to investigate the segmental motions in the subaxial cervical spine with different sizes of HSM under Gx accelerative loading. A three-dimensional finite element model of the male head-neck spinal column was used. Three different size military helmets were modeled and incorporated into head-neck model. The models were exercised under Gx accelerative loading by inputting low and high pulses to the cervical vertebra used in the experimental studies. Segmental motions were obtained and normalized with respect to the non-HSM case to quantify the effect of HSM. Segmental motions increased with an increase in velocity at all segments of the spine. Increasing helmet size resulted in larger motion increases. Angulations ranged from 0.9° to 9.3° at 1.8 m/s and from 1.3° to 10.3° at 2.6 m/s without a helmet. Helmet increased motion between 5% to 74% at 1.8 m/s. At 2.6 m/s, the helmet increased segmental motion anywhere from 10% to 105% in the subaxial cervical spine. The greatest motion was seen at the C5-C6 level, followed by the C6-C7 level. The subaxial cervical spine experiences motion increases at all levels at both velocity profiles with increasing HSM. Larger helmet and greater impact velocity increased motion at all levels, with C5-C6 demonstrating the largest range of motion. HSM should be minimized to reduce the risk of cervical spine injury to the warfighter.

Time Series Prediction for Energy Consumption of Computer Numerical Control Axes Using Hybrid Machine Learning Models

The prediction of energy-related time series for computer numerical control (CNC) machine tool axes is an essential enabler for the shift towards autonomous and intelligent production. In particular, a precise prediction of energy consumption is needed to determine the environmental impact of a product and the optimization of its production. For this purpose, a novel approach for predicting high-frequency time series of numerically controlled axes based on the program code to be executed is presented. The method involves simulative preprocessing of the input NC code to determine each axis’s acceleration, velocity, and process force. Combined with the material removal rate, these variables are input for a machine learning (ML) model that delivers axis-specific high-frequency time series predictions. Compared to common approaches, it is thus possible to make predictions for the variable energy consumption of machine tools for any tool path or target resolution in the time domain. Experiments show that this approach achieves a high precision when a robust learning data basis is available. For the X-, Y-, and Z-axis, errors of 0.2%, −1.09%, and 0.09% for aircut and of 0.15%, −3.55%, and 0.08% for material removal can be achieved. The potentials for further improvement are identified systematically.

Finite element modeling of steady plastic shockwaves in porous metals: Role of size, shape, and spatial distribution of voids

This paper aims at developing a finite-element model, which simulates a planar impact experiment on a ductile metallic porous material. When the shockwave passes through a porous medium, the voids face a rapid collapse, and the material particles in the vicinity of the voids are subjected to very high acceleration. Acceleration forces generated at the microscale level may affect the overall response of the porous material. Analyzing the effect of the initial porosity, size, shape, and spatial distribution of voids on the plastic shock velocity and the shock structure was the main objective of this work. It is found that, for a given impact velocity, the plastic shock velocity depends solely on the material parameters of the dense material and the initial porosity. However, the size, shape and spatial distribution of voids, together with the initial porosity, play a significant role on the structure of the plastic shock.

Imaging in Whiplash-Associated Disorders.

"Whiplash," a term describing the severe acceleration and deceleration forces applied to the head, craniocervical junction (CCJ), and cervical spine during trauma, is one of the most frequent mechanisms of injury to the CCJ. The CCJ is a complex region at the transition of the cranium and the cervical spine, essential for maintaining craniocervical stability. In whiplash injuries, the CCJ may be compromised due to underlying ligamentous or, less frequently, osseous, intravertebral disk and/or muscular lesions. Imaging is crucial in detecting acute lesions but may also play a role in the follow-up of chronic pathology because soft tissue lesions and progressive disk pathology could contribute to a whiplash-associated disorder.

Development of an impulsive motion generator inspired by cocking slip joint of snapping shrimp.

We propose an impulsive motion generator inspired by snapping shrimp. The proposed device mimics the geometrical arrangement of a unique claw joint calledcocking slip jointand integrates it with an artificial rack-pinion actuator mechanism rather than adopting the musculoskeletal system as it is. The design approach allows the proposed device to reproduce the impulsive slip motion through the torque reversal and unlatching mechanism of the underlying unique joint by using a single servo motor. Static and dynamic analyses revealed that the actuator force required to store and release elastic energy was remarkably small compared with the resulting acceleration force and rotation/tip speed. Through simulations and experiments, we validated the mechanical analyses and confirmed that the resulting ultrafast slip motion was comparable with the claw closure of snapping shrimp based on the cocking slip joint. Moreover, from an engineering perspective, the motion profiles are modifiable through design parameters, and the repeatability of the impulsive slip motion is satisfactory.

Sex differences regarding the effects of arm swing on ground reaction force and trunk movements between track and field athletes

The purpose of this study was to clarify the sex difference in the effects of arm swing movements of track and field athletes on ground reaction force and trunk movement. Seven male and nine female athletes belonging to a university track and field team were asked to perform arm swings for 10 seconds each under three different conditions (longitudinal, lateral, and original) while in the standing position. Three-dimensional coordinate data for each experimental trial was collected using an automatic optical motion analyser, and ground reaction forces were measured using a force plate. Under the longitudinal condition, the mean acceleration force was greater for males than for females (p < .05), and the operating range of trunk twist angle was significantly greater for females than for males (p < .05). However, under the original condition, there were no significant differences between the sexes in mean acceleration force, but there were significant differences in maximum twist angle and minimum and maximum shoulder abduction angles (p < .05). These results indicate that there are sex differences in trunk movement and ground reaction force depending on the direction of arm swing.

Acceleration of metal plates by hybridization of electrical and chemical energy for potential application in high-velocity impact welding

Vaporizing foil actuator welding is employed to connect dissimilar metals by utilizing the energy of an electrical explosion as the driving force for flyer plate acceleration. Herein, the electrical and chemical energies of explosives were combined to increase flyer plate velocity. A metal foil or wire mesh was used as an actuator, and a small amount of explosives was placed on the foil. Uniform acceleration of the flyer plate on the actuator was recorded using a high-speed video camera. The electrical energy applied to the actuator was measured synchronously by filming. The explosion of chemical explosives was successfully initiated owing to the electrical explosion of the actuator. In all experiments, the combination of the electrical explosion and chemical reaction improved the acceleration of the samples, facilitating higher velocities. The impact of the actuator type (mesh or foil) and the electric discharge parameters on the performance was studied. While foil actuators were more efficient in experiments on electric explosions alone, mesh actuators were superior when the chemical explosive was added. Explosions of the mesh actuator could initiate low density pentaerythritol tetranitrate (PETN) (the space-filling rate of PETN was approximately 30%). An explosive force of 0.3 g of PETN was converted into a driving force, imparting the flying plate with a velocity greater than 210 m/s. Electrical energy consumption for PETN initiation may be assumed to have an insignificant impact on flyer plate acceleration. In future, the proposed method may be used to connect heavier and thicker materials without expensive high-performance capacitors.

DEVELOPMENT, INSTRUMENTATION, AND ANALYSIS OF RECOIL THROUGH A RIFLE SCOPE

The research and development of new technologies to incorporate in the sport optics field have orientated the design, development, and construction of new riflescopes with state-of-the-art materials, processes, and technology. With each evolution, the riflescope should be evaluated to observe and acquire data on how the riflescope behaves during recoil. For this, the data acquisition and test setup should be easy to maintain, portable, and fast setup addition, measurements should be repeatable and low-cost. A literature review was conducted to check what has been done, what sensors and data acquisition controllers were used, the setup type, and the results. The sensor selection process required numerous specifications to filter the possible sensors for the ideal selection. The main factors and basis for the appointment were weight, G force, frequency, and price. The calculated theoretical max acceleration suffered by the rifle setup is 114g. The sensor also must be easily mounted/unmounted to/from the riflescope body. Furthermore, the sensor should be rigidly fixed not to suffer any unnecessary vibration from the interface and interfere with the measured data. Finally, the data acquisition should be accomplished relatively quickly to measure all the necessary data points. Sensors and accessories from various manufacturers were researched that fit the requirements. However, due to cost limitations, the selected sensor was the ADXL372.The testing setup includes a rifle and riflescope assembly on a stand. The sensor is guided and fixed on the riflescope, and a microcontroller reads and stores the acquired values. As a result, the testing setup is easy to transport and has a quick and repeatable structure. The measured acceleration values can calculate acceleration curves, displacement, velocity, and forces. The setup is ideal as it can be used to monitor the riflescope reaction on each test point, and results can have many uses, such as validating a numerical model FEA simulation. This paper will present and discuss the instrumentation and setup needed to read acceleration values on a riflescope from the firearm recoil and analyze the data for further use and interpretation. Keywords: Rifle scope, Recoil, accelerometer, MEMS, ICP, Arduino, ADXL372.

Design and numerical analysis of Cross-Laminated bamboo (CLB) buildings with different rocking wall configurations

Engineering bamboo attracts increasing attention due to its renewable, low-carbon properties as well as the high strength-to-weight ratio. This paper proposed a displacement-based design (DBD) method for cross-laminated bamboo (CLB) rocking wall buildings based on experimental tests. The DBD was to control the story drift limitation considering the collapse prevention (CP) hazards level. The DBD accounted for the detailed design of prestressed tendons (PT) and conventional friction dampers (CFD). Segmented and monolithic rocking wall configurations were designed based on DBD and applied in the building. The simplified numerical models (SNM) for those two rocking walls were established in ABAQUS using cartesian connectors. Then two three-story CLB building models, i.e., X-LamBR1 with segmented rocking wall and X-LamBR2 with monolithic rocking wall were developed. Modal analysis and time history analysis were conducted with these two models. Smaller inter-story displacement, acceleration, and shear force were observed in X-LamBR2. Simulation results indicated that building with a monolithic rocking wall configuration performed better under earthquake excitation.

Формирование секторных полей остаточных термопластических напряжений в полотне круглой пилы

The efficiency of a stationary circular saw is determined by the performance and operational reliability of the woodcutting unit. During operation, the circular saw blade is exposed to a variety of complex loads and thermal conditions. The rigidity and stability of the saw blade determine its capacity to resist the perturbing cutting forces. The cutting compound itself is a thin disc made of steel with a hole in the middle that has a serrated cutting edge. It consists of three areas: peripheral, middle, and central. The stability of the saw blade is determined by the middle and peripheral parts. The increase in durability is achieved by plastic deformation to form the strip boundaries of the radial sections. These parts are treated by forging in both national and international practice. Normalization of loads on the blade in case of local mechanical contact with the working body is formed in the strip boundaries of the radial sections through the formation of places with plastic deformation of the metal, which rearrange the loads and place them in the radial direction. At the same time, countertension appears from the adjoining sections, leading to mutual “repulsion” of them and the creation of compressive tension that compensates for the forces of centrifugal acceleration, thermal heating of separate areas of the saw blade, external longitudinal and transverse bending tension that arise during wood processing. The combined interaction of all adjoining sections provides the tension and stability of the saw blade. The creation of the radial sections by forging has some significant disadvantages. Their elimination requires a fundamentally new approach, such as the formation of the residual stress sections in the saw blade by thermal exposure. It creates a normalized residual thermoplastic tension in the saw blade by a short-time (1–2 s) focused thermal influence on the strip boundaries of the radial sections. The results of the conducted research determined the boundaries of the sections for thermal treatment and the temperature range, which ensure the formation of normalized residual thermoplastic tension in the circular saw blade through concentrated pulsed heating of the strip edges of radial sections. For citation: Melekhov V.I., Solovev I.I. Formation of Sectoral Residual Thermoplastic Tension Fields in Circular Saw Blade. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 146–154. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-146-154

Dynamic Response Analysis of Mega-Sub Isolated Structures under Multiaxial Earthquakes

With the use of seismic isolation techniques on mega-sub structures, several scholars have carried out research on them. However, little research has been carried out on mega-sub isolated structures under multiaxial earthquakes. There have been instances in actual engineering where the peak vertical acceleration exceeded the horizontal direction, and the vertical seismic component will also amplify the dynamic response of the structure in the horizontal direction, so in practice, it is necessary to consider the influence of the vertical component of the earthquake on the structure. To investigate the dynamic response of mega-sub isolated structures under unidirectional earthquake and coupled earthquake, this paper used numerical methods to analyze the influences of the horizontal and vertical damping ratio of the isolation layer, the horizontal and vertical frequency ratio of the main substructure, and the mass ratio of the main substructure on the acceleration and displacement of the main and substructure. The optimum parameter values are finally achieved by analytical calculations, which provide a basis for further optimization and practical design of the structure. Finally, the collision between the main and sub-structures in the mega-sub isolated structure was simulated, and the influences of the peak ground motion, main and subframe spacing, vertical seismic component, and sub-structure height on the collision force and acceleration were analyzed. It was shown that the conflict of the main and sub-structures generates instantaneous, large collision forces, which also instantaneously amplify the acceleration and base shear force response, which should be avoided in practical engineering.

Rail-structure interaction and vehicle-track-structure interaction level 1 and 2 analyses

Rail-structure interaction (RSI) analysis and vehicle-track-structure-interaction (VTSI) analysis are often required during bridge design. For example, the California High-Speed Train Project requires RSI analysis for final design of all structures, as well as VTSI analysis, with the level of interaction to be modeled determined by the complexity of a structure. The goal of RSI analysis is to ensure that superstructure deformations and rail stresses are within acceptable limits. VTSI analysis is a dynamic analysis that takes into account influence of actual trainsets. VTSI Level 1 analysis includes train loads as a series of moving loads. This analysis allows evaluation of dynamic impact effects from trainsets and vertical accelerations of the deck. For complex high-speed railway bridges, VTSI Level 2 might be required, accounting for full dynamic interaction between the trainset and the bridge. To represent this interaction, the trainset is modeled as a multibody system consisting of rigid bodies, springs, and dashpots. The interaction between wheels and rails is accounted for through kinematic constraints and Lagrange multipliers. This paper presents modeling, RSI, and VTSI analyses of a railway bridge in the LARSA 4D software package. The track and superstructure are modeled in an expedited way using a macro that generates the track, approach, and bridge geometries. Fasteners are modeled as hysteretic springs and automatically positioned along the curved geometry of the track using a LARSA 4D’s bridge path coordinate system definition. RSI analysis is performed accounting for temperature differentials between rails and the deck, vertical train loads, acceleration and braking forces. Break in the rail is introduced using stage construction analysis, followed by progressive collapse analysis (with adapting increments and arc-length control) or nonlinear dynamic analysis. Finally, VTSI Level 1 and 2 analyses are performed and the results are compared. Car body accelerations are compared to limit values to ensure passenger comfort.

Inertial Sensor Technologies-Their Role in Equine Gait Analysis, a Review.

Objective gait analysis provides valuable information about the locomotion characteristics of sound and lame horses. Due to their high accuracy and sensitivity, inertial measurement units (IMUs) have gained popularity over objective measurement techniques such as force plates and optical motion capture (OMC) systems. IMUs are wearable sensors that measure acceleration forces and angular velocities, providing the possibility of a non-invasive and continuous monitoring of horse gait during walk, trot, or canter during field conditions. The present narrative review aimed to describe the inertial sensor technologies and summarize their role in equine gait analysis. The literature was searched using general terms related to inertial sensors and their applicability, gait analysis methods, and lameness evaluation. The efficacy and performance of IMU-based methods for the assessment of normal gait, detection of lameness, analysis of horse-rider interaction, as well as the influence of sedative drugs, are discussed and compared with force plate and OMC techniques. The collected evidence indicated that IMU-based sensor systems can monitor and quantify horse locomotion with high accuracy and precision, having comparable or superior performance to objective measurement techniques. IMUs are reliable tools for the evaluation of horse-rider interactions. The observed efficacy and performance of IMU systems in equine gait analysis warrant further research in this population, with special focus on the potential implementation of novel techniques described and validated in humans.

Shaking table tests of veneer masonry wall retrofitted with long-rawlplug screw anchors

Veneer masonry walls are vulnerable to lateral forces such as seismic loads, and their failure has caused human casualties and property damage. This study developed a new anchor for existing veneer walls and evaluated its seismic performance using shaking table tests. The presence or absence of retrofit anchors, combination of anchors and steel strips, and anchor spacing were considered as the experimental variables. Out-of-plane excitation was applied to the specimens, and the magnitude of the seismic acceleration was calculated according to the required response spectrum defined in ICC-ES AC156. The experimental results showed that overturning occurred on the non-retrofitted veneer wall; however, the veneer wall reinforced using the proposed anchor exhibited no overturning. The peak ground acceleration, relative displacement, amplification coefficient, and shear force of the reinforced specimens decreased relative to those of the unreinforced specimens. Notably, the proposed method achieved a high seismic reinforcement performance even when the anchor spacing was set to 800 mm.

Active metamaterials for realizing odd mass density

Solids built out of active components have exhibited odd elastic stiffness tensors whose active moduli appear in the antisymmetric part and which give rise to non-Hermitian static and dynamic phenomena. Here, we present a class of active metamaterial featured with an odd mass density tensor whose asymmetric part arises from active and nonconservative forces. The odd mass density is realized using metamaterials with inner resonators connected by asymmetric and programmable feed-forward control on acceleration and active forces along the two perpendicular directions. The active forces produce unbalanced off-diagonal mass density coupling terms, leading to non-Hermiticity. The odd mass is then experimentally validated through a one-dimensional nonsymmetric wave coupling where propagating transverse waves are coupled with longitudinal ones whereas the reverse is forbidden. We reveal that the two-dimensional active metamaterials with the odd mass can perform in either energy-unbroken or energy-broken phases separated by exceptional points along principal directions of the mass density. The odd mass density contributes to the wave anisotropy in the energy-unbroken phase and directional wave energy gain in the energy-broken phase. We also numerically illustrate and experimentally demonstrate the two-dimensional wave propagation phenomena that arise from the odd mass in active solids. Finally, the existence of non-Hermitian skin effect is discussed in which boundaries host an extensive number of localized modes. It is our hope that the emergent concept of the odd mass can open up a new research platform for mechanical non-Hermitian system and pave the ways for developing next-generation wave steering devices.

Longitudinal Outcomes of Cumulative Impact Exposure on Oculomotor Functioning in Professional Motorsport Drivers

Professional motorsport drivers are regularly exposed to biomechanical forces comparable with those experienced by contact and collision sport athletes, and little is known about the potential short-term and long-term neurologic sequelae. To determine whether cumulative impact exposure is associated with oculomotor functioning in motorsport drivers from the INDYCAR professional open-wheel automobile racing series. This is a longitudinal retrospective cohort study conducted across 3 racing seasons (2017-2019). Statistical analyses were conducted in November 2021. Data were retrieved from a secondary care setting associated with the INDYCAR series. INDYCAR series drivers who participated in 3 professional level racing seasons and were involved in at least 1 contact incident (ie, crash) in 2 of the 3 seasons were included in the study. Cumulative acceleration and deceleration forces and total contact incidents (ie, crashes) measured via accident data recorder third generation chassis and ear accelerometers. Postseries oculomotor performance, including predictive saccades, vergence smooth pursuit, and optokinetic nystagmus, was measured annually with a head-mounted, clinical eye tracking system (Neurolign Dx 100). Thirteen drivers (mean [SD] age, 29.36 [7.82] years; all men) sustained median resultant acceleration forces of 38.15 g (observed range, 12.01-93.05 g; 95% CI, 30.62-65.81 g) across 81 crashes. A 2-way multivariate analysis of variance did not reveal a statistically significant association between ear and chassis average resultant g forces, total number of contact incidents, and racing season assessed (F9,12 = 0.955; P = .54; Wilks Λ = 0.44). In this cohort study of professional drivers from the INDYCAR series, there were no statistically significant associations among cumulative impact exposure, racing season assessed, and oculomotor performance. Longitudinal studies across racing seasons using multidimensional examination modalities (eg, neurocognitive testing, advanced imaging, biomarkers, and physical examination) are critical to understand potential neurological and neurobehavioral sequelae and long-term consequences of cumulative impact exposure.

Development of an Open-Source Injection Mold Monitoring System

In the highly competitive injection molding industry, the ability to effectively collect information from various sensors installed in molds and machines is of the utmost relevance, enabling the development of data-based Industry 4.0 algorithms. In this work, an alternative to commercially available monitoring systems used in the industry was developed and tested in the scope of the TOOLING 4G project. The novelty of this system is its affordability, simplicity, real-time data acquisition and display in an intuitive Graphical User Interface (GUI), while being open-source firmware and software-based. These characteristics, and their combinations have been present in previous works, but, to the authors' knowledge, not all of them simultaneously. The system used an Arduino microcontroller-based data acquisition module that can be connected to any computer via a USB port. Software was developed, including a GUI, prepared to receive data from both the Arduino module and a second module. In the current state of development, data corresponding to a maximum of six sensors can be visualized, at a rate of 10 Hz, and recorded for later usage. These capabilities were verified under real-world conditions for monitoring an injection mold with the objective of creating the basis of a platform to deploy predictive maintenance. Mold temperature, cavity pressure, 3-axis acceleration, and extraction force data showed the system can successfully monitor the mold and allowed the clear distinction between normal and abnormal operating patterns.

Assessment of arresting performance of foamed concrete arrestors via the coupled discrete element and virtual prototype simulations

Engineered material arresting system (EMAS) is a foamed concrete arrestor that can arrest aircraft overrunning the runway. Identification of the arresting effect of foamed concrete materials on overrunning aircraft is crucial for optimizing EMAS. By coupling the Discrete Element Method (DEM) and the Virtual Prototype Method (VPM), the EMAS crushing process and the aircraft dynamics are simulated simultaneously. The material properties of different foamed concrete were firstly determined via experiments, and then adopted as input for DEM of EMAS. Subsequently, the VPM of A320 aircraft with various overrun speeds was established. The rationality of the DEM-VPM model was verified by the field test result. The sensitivity analysis on the arresting processes reveals that a 67% increase in EMAS thickness and a 102% increase in material strength can enhance the arresting performance by 96% and 11.5%, respectively. However, freeze–thaw has negative effect. In addition, higher overrun speeds of the aircraft can cause greater acceleration and drag forces, and thereby magnify the risk of damage to the aircraft.

Development of Nonlinear Geometric Seismic Isolation with a Duffing Spring

Seismic isolation is widely used in several countries, and the number of seismically isolated buildings has increased rapidly in recent decades. Seismic isolation extends the natural period of a building to decrease the absolute acceleration and seismic force. As there is a trade-off between the absolute acceleration and displacement, a soft layer results in a large displacement for a large seismic wave, but the hard one causes the large absolute acceleration even for a small seismic wave. The restoring force of a Duffing spring is given by the third and first orders of the displacement. This spring has been applied to protect a building from large earthquake waves. However, the influence of the coefficient of the Duffing spring that determines the dynamic characteristics of the system has not been clarified. Thus, a used Duffing spring may not be appropriate for seismic resistance. Moreover, most studies are based on analytical methods, and the advantages of the Duffing isolation have not been verified in an actual system. To address these problems, this paper reveals the influence of the coefficient of the Duffing spring on structural responses to seismic waves. Moreover, this paper devised a way to implement a Duffing spring for seismic isolation and carried out experiments to verify the validity in actual systems. The experimental results presented that the Duffing spring was effective in protecting a building in actual systems.

Shaking table test and seismic behaviour evaluation of viscous damping wall with amplification mechanism

Methods to improve the damping efficiency of dampers have been widely investigated. This study introduces a shaking table test on a viscous damping wall (VDW) with a displacement amplification mechanism. A mechanical model was developed and validated using a model test. Then, shaking table tests were conducted on five-story steel frames equipped with an VDW and a viscous damping wall with amplification mechanism (AVDW). The AVDW was confirmed to be effective in mitigating the structural acceleration, inter-story displacement, and shear forces. Finally, a numerical simulation of a seven-story structure was performed to characterise the seismic behaviour of the AVDW system. By comparing the structural responses and performance state, the efficiency of the AVDW in mitigating the structural responses and improving seismic safety was confirmed.