Impact Force Distribution Research Articles

Neuromuscular Responses to Impact and Collision During Elite Rugby League Match Play

The purpose of this study was to investigate the relationship between the prematch and short-term postmatch neuromuscular responses to the intensity, number, and distribution of impacts associated with collisions during elite Rugby League match play. Twenty-two elite male Rugby League players were monitored during 8 regular season competition matches using portable global positioning system (GPS) technology. The intensity, number, and distribution of impact forces experienced by players during match play were recorded using integrated accelerometry. Peak rate of force development (PRFD), peak power (PP), and peak force (PF) were measured during a countermovement jump on a force plate 24 hours prematch, 30 minutes prematch, 30 minutes postmatch and then at 24-hour intervals for a period of 5 days postmatch. The change in the dependent variables at each sample collection time was compared with that at 24 hours prematch and 30-minute prematch measures. There were significant (p < 0.05) decreases in PRFD and PP up to 24 hours postmatch with PF significantly (p < 0.05) being decreased 30 minutes postmatch. Significant (p < 0.05) correlations were found between the total number of impacts and PRFD and PP 30 minutes postmatch. Impact zones 4 (7.1-8.0 G), 5 (>8.1-10.0 G), and 6 (>10.1 G) were significantly (p < 0.05) correlated to PRFD and PP 30 minutes postmatch with the number of zone 5 and 6 impacts significantly (p < 0.05) correlated to PRFD and PP 24 hours postmatch. Elite Rugby League match play resulted in significant neuromuscular fatigue and was highly dependent on the number of heavy collisions >7.1G. Results demonstrate that neuromuscular function is compromised for up to 48 hours postmatch indicating that at least 2 days of modified activity is required to achieve full neuromuscular recovery after elite Rugby League match play. Position-specific demands on energy systems and the influence of repeated blunt force trauma during collisions during elite Rugby League match play should be considered when planning postmatch recovery protocols and training activities to optimize subsequent performance.

Jet Performance Testing of High-Pressure Waterjet Descaling Nozzles

Descaling nozzles, generator of high-speed waterjets, are key components in high-pressure waterjet descaling system. Jet performance of the nozzle has great effect on hot-rolling steel billet descaling. Most domestic manufactures provide nozzle structural data and impact force scale with rated pressure, such as orifice diameter, injecting angle and scattering angle. However, jet distribution shape and jet impact force distribution and strength, which are major parameters affecting steel billet descaling quality, are not available from manufactures. A jet performance test device for nozzles was developed in this paper. Two and three dimensional graphs of jet impact force distribution with different standoff distance were obtained. Shape of jet distribution area was indicated in two dimensional graphs while jet impact strength and distribution were given in three dimensional graphs, providing evidence for jet performance judgement. Injecting angle, scattering angle and flow volume coefficient could also be measured with the device. A fan-type nozzle used for scale removal was tested. Results obtained were presented and discussed.

Biochemical and Endocrine Responses to Impact and Collision During Elite Rugby League Match Play

The purpose of this study was to investigate the relationship between the prematch and short-term postmatch biochemical and endocrine responses to the intensity, number, and distribution of impacts associated with collisions during elite Rugby League match play. Seventeen elite male Rugby League players each provided blood and saliva samples 24 hours prematch, 30 minutes prematch, 30 minutes postmatch, and then at 24-hour intervals for a period of 5 days postmatch to determine plasma creatine kinase concentration ([CK]) and salivary cortisol concentration ([sCort]). The intensity, number, and distribution of impact forces experienced by players during match play were recorded using portable global positioning systems (GPSs). The change in the dependent variables at each sample collection time was compared to 24 hours prematch and 30-minute prematch measures. The [CK] and [sCort] increased significantly (p < 0.05) during match play. Significant correlations (p < 0.05) were observed between the number of hit-ups and peak [CK] 24 hours postmatch, 48 hours postmatch, and 72 hours postmatch (p < 0.05). The number of impacts recorded in zone 5 (8.1-10.0G) and zone 6 (>10.1G) during match play was significantly correlated (p < 0.05) to [CK] 30 minutes postmatch, 24 hours post, 48 hours post, and 72 hours postmatch. The GPS was able to provide data on the intensity, number, and distribution of impacts resulting from collisions during match play. Elite Rugby League match play resulted in significant skeletal muscle damage and was highly dependent on the number of heavy collisions >8.1G. [CK] remained elevated 120 hours postmatch identifying that at least 5 days modified activity is required to achieve full recovery after elite Rugby League match play.

Evaluation of a flexible force sensor for measurement of helmet foam impact performance

The association between translational head acceleration and concussion remains unclear and provides a weak predictive measure for this type of injury; thus, alternative methods of helmet evaluation are warranted. Recent finite element analysis studies suggest that better estimates of concussion risk can be obtained when regional parameters of the cranium, brain and surrounding tissues are included. Lacking, however, are empirical data at the head–helmet interface with regards to contact area and force. Hence, the purpose of this study was to evaluate a system to capture the impact force distribution of helmet foams. Thirteen Flexiforce® sensors were arranged in a 5×5cm array, secured to a load cell. Three densities of foam were repeatedly impacted with 5J of energy during ambient (20°C) and cold (−25°C) conditions. RMS error, calculated relative to the global force registered by the load cell, was <1.5% of the measurement range during individual calibration of the Flexiforce® sensors. RMS error was 5% of the measured range for the global force estimated by the sensor array. Load distribution measurement revealed significant differences between repeated impacts of cold temperature foams for which acceleration results were non-significant. The sensor array, covering only 36% of the total area, possessed sufficient spatial and temporal resolution to capture dynamic load distribution patterns. Implementation of this force mapping system is not limited to helmet testing. Indeed it may be adopted to assess other body regions vulnerable to contact injuries (e.g., chest, hip and shin protectors).

Numerical modeling of the edge rounding of brittle materials by vibratory finishing

The paper presents a numerical model of the edge rounding of brittle materials during vibratory finishing. The material removal in this process is dominated by small-scale edge chipping where the abrasive particles protruding from the impacting media indent the surface asperities of the wear zone producing chips of the order of 10 μm in length. The model predicts the evolution of the edge profile by applying random indentations to the edge, evaluating the possibility of chip formation, and modifying the edge profile accordingly. The model predictions of the change in edge shape with processing time agreed quite well with experimental results for borosilicate glass edges having initial chamfer angles of 105°, 120°, and 135°. The model was used to identify the effect of edge angle and the distribution of impact forces on edge wear and the resulting surface micro-topography.

数値モデルによるマニピュレータ内の衝撃力予測(G01-1 計算シミュレーション,G01 計算力学部門)

Generally, force sensors do not have high reliability in their detected values, especially for dynamic forces. We discuss a new methodology to obtain the distribution of impact forces in manipulators, by considering the numerical model of the mechanism. In this research, a prediction system of impact force using the Finite Element Method is developed, based upon the incremental equation of motion considering the volume force generated by the motion. Expression of contact is discussed, in this paper, on two ways; (a) the impulse method and (b) the gap-element method. A sensor output in an experiment and the numerical result are compared. Although further investigation on the impulse time is required, the peak values of the impact force are practically in good agreement.

Granule coalescence modelling: including the effects of bond strengthening and distributed impact separation forces

Many existing models of granule coalescence assume that the two granules have successfully coalesced provided that they stick during their initial impact. However, although non-rebound is a necessary condition for coalescence, it is not sufficient. It is also required that the bond formed between the two granules be strong enough to resist being broken by subsequent impacts within the granulator. A theoretical framework is proposed in which both the rate of bond strengthening and the distribution of impact separation forces are included in order to calculate the probability that the collided dumbbell will survive and hence permanently coalesce. This work highlights the need for further research into the mechanisms and the rate at which a granule dumbbell becomes moulded into a single larger granule, and also the distribution of impact forces inside a granulator.

A Study of the Fracture of Pellets Fired Against a Target

AbstractPellets of sintered Al2O3 of approximately 3 mm diameter and length were broken in the Brazilian mode and the distribution of strength obtained. It was found that there was also a distribution of Young's modulus E. Hertzian theory implies that the maximum impact force of a pellet fired against a rigid target would depend on E. However, since the pellets can strike in different geometries there is a distribution of impact force for a fixed E. Comparison of theory with data obtained with a force‐time transducer as the target showed that the major variation of maximum recorded force could be assigned to the variation of E. The median of the maximum recorded force varied with velocity as v6/5, implying that the pellets behaved approximately as impacting spheres. An attempt was made to predict the probability of breakage in one impact from convoluting the distribution of impact force with the strength distribution from the Brazilian test converted to the equivalent strength distribution expected for impacting spheres. This gave the correct order of magnitude but did not accurately predict the experimental values.

A mechanical investigation of the functioning of mouthguards

Mouthguards may play an important role in the prevention of injuries to the teeth and the related tissues of people participating in various branches of sport. Several publications provide statistical data concerning the effect of mouthguards in protecting the head and neck region, including the teeth of e.g. American football players (Ref. 1, 2, 3).Also, much information is available on the mechanical properties of potential mouthguard materials (Ref. 4, 5, 6). However, basic investigations to the mechanics of teeth protection by mouthguards have only scarcely been done (Ref. 7). It was the aim of this study to investigate the functioning of mouthguards, the attenuation of impact forces, non-destructively in terms of both local attenuation in the contact area and distribution of impact forces over adjacent teeth.