Impact Location Research Articles

Multifidelity data augmentation for data driven passive impact location and force estimation in composite structures under simulated environmental and operational conditions

Data driven methods for impact location and severity estimation have great potential for real life application due to their ability to construct meta models that are not affected by changes in structural complexity (e.g. stiffeners and cut-outs). However, to do so, an initial reference database containing known input and output pairs is required to form an accurate meta model. The requirement to collect this data (mainly in the form of experimental tests) is considered by many to be not feasible and hinders the application of data driven methods in large scale, real life structures. Here a new multifidelity approach is presented to reduce the “cost” of constructing the reference database necessary for data driven impact location and severity estimation methods. The proposed cokriging approach is used to combined “cheap” low fidelity FE (Finite Element) simulation data with a limited amount of accurate but “expensive” experimental data to construct a reference database that requires less experimental data sampling (thus lower “cost”) but with similar levels of accuracy compared to reference databases that were constructed from pure experimental data. Using previously developed impact location (kriging based localisation) and maximum force estimation (maximum impact force gradient method) methods, the effect of different reference databases with varying amounts of experimental data samples are tested. The results obtained on a CFRP (Carbon Fibre Reinforced Plastic) coupon and stiffened panel showed that using pure FE data for the reference database yielded poor results. By adding a limited number of experimental points, it was shown that the accuracy increases significantly approaching levels achieved using pure experimental data with significantly less samples. The wider context of data fusion is also explored, highlighting the possibility to combine various sources of data (including inspection history as well as data from sister assets) which can possibly be used to create a data driven framework that requires less initial data whilst also being robust and self-improving.

Effects of Impact Location, Impact Angle and Impact Speed on Head Injury Risk of Vietnamese Pedestrian Hit by a Sedan

Effects of Impact Location, Impact Angle and Impact Speed on Head Injury Risk of Vietnamese Pedestrian Hit by a Sedan

Padded Helmet Shell Covers in American Football: A Comprehensive Laboratory Evaluation with Preliminary On-Field Findings.

Protective headgear effects measured in the laboratory may not always translate to the field. In this study, we evaluated the impact attenuation capabilities of a commercially available padded helmet shell cover in the laboratory andon the field. In the laboratory, we evaluated the padded helmet shell cover's efficacy in attenuating impact magnitude across six impact locations and three impact velocities when equipped to three different helmet models. In a preliminary on-field investigation, we used instrumented mouthguards to monitor head impact magnitude in collegiate linebackers during practice sessions while not wearing the padded helmet shell covers (i.e., bare helmets) for one season and whilst wearing the padded helmet shell covers for another season. The addition of the padded helmet shell cover was effective in attenuating the magnitude of angular head accelerations and two brain injury risk metrics (DAMAGE, HARM) across most laboratory impact conditions, but did not significantly attenuate linear head accelerations for all helmets. Overall, HARM values were reduced in laboratory impact tests by an average of 25% at 3.5m/s (range: 9.7 to 39.6%), 18% at 5.5m/s (range: -5.5 to 40.5%), and 10% at 7.4m/s (range: -6.0 to 31.0%). However, on the field, no significant differences in any measure of head impact magnitude were observed between the bare helmet impacts and padded helmet impacts. Further laboratory tests were conducted to evaluate the ability of the padded helmet shell cover to maintain its performance after exposure to repeated, successive impacts and across a range of temperatures. This research provides a detailed assessment of padded helmet shell covers and supports the continuation of in vivo helmet research to validate laboratory testing results.

Dynamic Behavior of Aluminum Plates Subjected to Sequential Fragment Impact and Blast Loading: An Experimental Study

This paper presents a study on the dynamic behavior of thin aluminum plates subjected to consecutive fragment impact and blast loading. To this end, two separate experimental setups are used. In the first setup, 2 mm thick aluminum plates EN-AW-1050A-H24 were subjected to the ballistic impact of fragment-simulating projectiles (FSPs). Experiments were carried out for FSP calibers of 7.62 mm and 12.7 mm considering both single impact and triple impacts with variations in the spacing of the impact locations. The out-of-plane displacement and in-plane strain fields were measured using digital image correlation (DIC) coupled to a pair of high-speed cameras in a stereoscopic setup. In the second setup, a subsequent blast loading was applied to the perforated plates using an explosive-driven shock tube (EDST). After the plates are perforated, the strain field around the holes depended on the caliber, the impact orientation of the FSP, and the distance between the impact locations. When the blast loading was applied, cracks tended to appear in areas of strain concentration between the perforated holes. It was found that the relative distance between the holes significantly influences the target’s response mode.

A Systematic Review of Spatial Differences of the Ball Impact within the Serve Type at Professional and Junior Tennis Players

Since the flat serve (FS) minimizes the ball spin and kick serve (KS) combined topspin and sidespin, this systematic review aimed to explore the ball impact location (BI) within the FS and KS at the professional men, junior men, and women tennis players. The PRISMA guideline was used, and the original articles were searched in Scopus, Web of Science, and PubMed. The means and standard deviations computed from the distance of BI from the origin within the FS and KS on the x, y, and z axes (global coordinate system) were normalized by the participants’ height and weighted by the number of participants in one-way ANOVA. Ten articles with a pooled sample of 133 males and 51 females aged 11–25 were included. The professional men had more stable BI on the x-axis within the FS by 56% (p < 0.001), within the KS by 58% (p < 0.001), and on the y-axis within the KS by 90% (p < 0.001) than junior men. The professional and junior men had the BI more leftwards from the origin on the x-axis within the KS by 188% (p < 0.001) and 88% (p < 0.001), respectively than within the FS.

The capture of airborne particulates by rain

Rain cleans pollution out of the atmosphere, as droplets collide with airborne particles during free fall. Such particle–droplet collisions have been presumed to be capture events, but the details of such collisions lack thorough investigation. We show that rain droplets and pollution particles interact through multiple collision behaviours, including captures on the droplet surface, cavity-forming droplet entries and ricochets. Rain drop diameter and free fall velocity, in addition to pollution particle density, size, wettability and droplet impact location, determine which capture or escape behaviour occurs. Our findings reveal that rain does not capture all airborne pollutants equally even upon collision, and certain pollutants prove more difficult to remove from the air than others. Consequently, we must account for both rain and pollution characteristics to understand pollution capture mechanisms and pollution fluxes in the environment.

Response of multi-cell steel–concrete–steel sandwich panels impacted by a hemi-spherical head: Experimental and numerical studies

In this study, a novel multi-cell steel–concrete–steel (MCSCS) sandwich panel was proposed for enhancing impact resistance of the traditional steel–concrete–steel​ (SCS) sandwich panel. The MCSCS sandwich panel employed stiffeners and headed studs to improve the bonding behavior between faceplates and concrete core as well as enhance its composite action and impact resistance. Impact tests were conducted on seven MCSCS panels via employing a drop weight loading system, and the influences of impact direction, spacing of headed stud and steel plate thickness on responses of MCSCS panels were investigated. Furthermore, the Finite Element (FE) model of the MCSCS panel was established, and the FE predictions were shown to be reasonable as compared to test results. Two types of failure modes of MCSCS panels under impact load were obtained via analyzing the test and FE results. In addition, based on the verified FE model, the influences of stiffeners, impact location and curvature of hammer head on impact responses of MCSCS panels were revealed via parametric studies. The results of FE simulations indicated that the impact location and curvature of hammer head had evident effect on the energy absorption and impact response of the MCSCS panel. Moreover, owing to the employment of stiffeners, the impact resistance of the MCSCS panel was evidently enhanced as compared to the traditional SCS panel.

Impact localization of composite laminates based on weight function compensation localization algorithm of thin film sensors

ABSTRACT Composite structures are sensitive to impact damage in practical engineering. Electric resistance change method (ERCM) is an ideal technique for damage monitoring of composite structures. Due to the anisotropy of fiber-resin matrix composites, impact location monitoring is difficult, and research on impact location of fiber composite laminates (FRPs) is limited. A preparation method of MXene/CNT/CuNps thin film sensor is proposed. According to the modeling simulation and theoretical calculation, the resistance change characteristics of the thin film sensor are obtained, the relationship between the impact distance and the resistance change is established, and the sensor array is designed. A three-point localization algorithm and a weight function compensation localization algorithm are proposed, which can improve the imaging accuracy of the impact position. The impact point location was observed and analyzed using ultrasonic C-scan technology. The results show that the weight function compensation positioning algorithm can accurately locate the impact of the composite structure, and the error in the X direction is 7.1%, the error in the Y direction is 0.03%, which verifies the effectiveness of the method.

Experimental Investigation on the Failure Behavior of Single-Stiffened Composite Panels under Compressive Load

Whilst the thin-walled composite structures have been widely used to build the primary components in aircraft, Low-Velocity Impact (LVI) can cause severe intra-laminar and inter-laminar damage in the composite material, reducing the mechanical performance of these components. This paper presents an experimental study on the compressive failure behavior of a Single Hat-Stiffener Panel (SHSP) with two typical flaws, i.e., impact-induced damage and skin/stiffener debonding. LVI tests were performed to introduce the damage around the radius edge of the stiffener and the center of the flat skin panel, respectively, while the skin/stiffener debonding was introduced to the SHSP by artificially embedding a PTFE film at the skin/stiffener interface during autoclave curing. The impact energy to cause Barely Visible Impact Damage (BVID) was determined to be 22 J for the thin SHSP configuration. Whilst the considerable damage area was detected by the ultrasonic scan for the thick SHSP at an energy level of 35 J, the impact-induced indentation was not visually detectable (<0.35 mm), indicating a high impact resistance of this thick SHSP. Compression After Impact (CAI) results showed a significant reduction (59.1%) in the ultimate compressive strength of the SHSP when the impact location was on the stiffener compared to the pristine specimen. However, this reduction is less significant (34.7%) when the damage resulted from the same impact energy in the flat skin panel. In this study, the presence of skin/stiffener debonding does not adversely influence the compressive strength of the thick SHSP, while this debonding flaw appears to cause a minor reduction in the compressive strength of the thin SHSP.

Distal Tumor Spread in Rectal Cancer-How Low Should We Go?

Distal tumor spread (DTS) is an adverse prognostic factor in rectal cancer correlating with advanced stage disease. We aimed to assess prevalence and location of distal tumor spread and impact of neoadjuvant chemoradiotherapy (NACRT) in patients who underwent proctectomy for rectal cancer. The pathology database at our institution was queried for all patients who underwent proctectomy with curative intent for rectal cancer from 1/2008 to 12/2016. Specimen slides were re-evaluated by a single expert rectal cancer pathologist to verify diagnosis and measure the distance to the distal resection margin. Main outcome measures were 3-year overall and disease-free survival. 275 consecutive patients were identified. 109/111 patients with clinical stage 3 disease received preoperative neoadjuvant chemoradiotherapy. DTS was found in 13 (4.7%) specimens, 6 with intra-mural and 7 with extra-mural distal tumor spread. DTS was found only in patients with clinical stage 3 disease. Length of DTS from the distal end of the tumor ranged from 0 to 30mm; in only 4 specimens DTS was >10mm. A positive distal resection margin was found in 5/275 (1.8%) specimens. A macroscopically tumor-free margin may suffice in patients with pre-treatment stage 1 or 2 disease. Furthermore, a 1cm margin is adequate in most patients with stage 3 disease.

A two-stage stochastic model for intermodal terminal location and freight distribution under facility disruptions

ABSTRACT A two-stage stochastic model is developed for intermodal facility location and freight distribution under random disruptions at shipper facilities and/or intermodal terminals (IMTs). The magnitude of the disruption and the impacted locations are uncertain parameters. A two-stage stochastic programming model is used to address supply uncertainty at shippers and throughput capacity uncertainty at IMTs. A level-method based decomposition approach and the L-shaped method are used to solve the model. The state of South Carolina in the U.S.A. is used as a case study with the goal of determining the set of IMT locations that minimise the total long-run network costs due to hurricane disruptions. A methodology is developed to generate realistic scenarios. The Freight Analysis Framework Version 4.5 data set is used to generate demands and supply, and k-means clustering is used with the Hurricane database (HURDAT2) to generate hurricane disruption scenarios. Sensitivity analyses are performed by varying the disruption probabilities, disruption duration, and direct shipping cost parameters. The results indicate that as disruptions increase, less disrupted intermodal facilities are opened. Also, as direct shipping costs increase, the long-term savings increase non-linearly for all magnitudes of disruptions.

Validation of the cutaneous impact location to predict intracranial lesion among elderly admitted to the Emergency Department after a ground-level fall

IntroductionIn the Emergency Departments, almost one out of two head CT scans are carried out for traumatic brain injuries among elderly victims of ground level-falls. Recently, a new predictive factor for intracranial lesions in this population has been suggested: presence and location of cutaneous impact. The aim of this study was to establish determinants of intracranial lesion among older patients admitted to EDs due to ground-level falls with traumatic brain injury using the head cutaneous impact location. MethodsA retrospective, observational and monocentric study of patients admitted to Emergency Department for ground-level falls with traumatic brain injury was carried out between 01 January 2017 and 31 July 2017. The primary outcome was identification of an acute intracranial lesion. A bootstrap procedure was employed to evaluate performance and internal validity of the final model. ResultsAmong the 1036 patients included, the mean age was 85.6 (SD 7.6) years and 94/1036 (9.1%, 95% CI 7.4–10.9) patients presented with an acute intracranial lesion. Multivariable analysis adjusted by bootstrap shrinkage showed that compared with temporal-parietal or occipital impact, Odds Ratio of intracranial lesions were 0.61 (95% CI 0.39–0.95, p = 0.03) in patients with frontal impact, 0.27 (95% CI 0.12–0.59, p = 0.001) in patients with facial impact and 0.21 (95% CI 0.06–0.77, p = 0.018) in patients without cutaneous impact. Subcutaneous hematoma (OR 1.97, p = 0.007), loss of consciousness (OR 4.66, p<0.001), fall-related amnesia (OR 2.58, p = 2.6), vomiting (OR 2.62, p = 0.002) and altered Glasgow Score (OR 6.79, p<0.001) were as well associated with high risk of intracranial lesion. Taking antiplatelets or anticoagulants were not associated with an increased risk of intracranial lesions. The model discrimination was adequate (C-statistic 0.79; 95% CI 0.73 – 0.85). ConclusionOur results establish specific determinants of intracranial lesions among elderly after ground level-falls. The cutaneous impact location may identify patients with high risk of intracranial lesion. Further researches are needed to propose a specific score based on these determinants so as to better target Head CT scan use.

Head Impact Location, Speed and Angle from Falls and Trips in the Workplace.

Traumatic brain injury (TBI) is a common injury in the workplace. Trips and falls are the leading causes of TBI in the workplace. However, industrial safety helmets are not designed for protecting the head under these impact conditions. Instead, they are designed to pass the regulatory standards which test head protection against falling heavy and sharp objects. This is likely to be due to the limited understanding of head impact conditions from trips and falls in workplace. In this study, we used validated human multi-body models to predict the head impact location, speed and angle (measured from the ground) during trips, forward falls and backward falls. We studied the effects of worker size, initial posture, walking speed, width and height of the tripping barrier, bracing and falling height on the head impact conditions. Overall, we performed 1692 simulations. The head impact speed was over two folds larger in falls than trips, with backward falls producing highest impact speeds. However, the trips produced impacts with smaller impact angles to the ground. Increasing the walking speed increased the head impact speed but bracing reduced it. We found that 41% of backward falls and 19% of trips/forward falls produced head impacts located outside the region of helmet coverage. Next, we grouped all the data into three sub-groups based on the head impact angle: [0°, 30°], (30°, 60°] and (60°, 90°] and excluded groups with small number of cases. We found that most trips and forward falls lead to impact angles within the (30°, 60°] and (60°, 90°] groups while all backward falls produced impact angles within (60°, 90°] group. We therefore determined five representative head impact conditions from these groups by selecting the 75th percentile speed, mean value of angle intervals and median impact location (determined by elevation and azimuth angles) of each group. This led to two representative head impact conditions for trips: 2.7m/s at 45° and 3.9m/s at 75°, two for forward falls: 3.8m/s at 45° and 5.5m/s at 75° and one for backward falls: 9.4m/s at 75°. These impact conditions can be used to improve industrial helmet standards.

Study on Low-Velocity Impact Behavior of Twaron® Fabric Subjected to Double-Impactor Impact from a Numerical Analysis Perspective

Abstract In the present study, a finite element impact model was developed and analyzed using commercial FEM code ANSYS® and then validated via a drop-weight impact experiment. Moreover, double-impactor impact models were designed and developed with different impact distribution and locations of two impactors to compare impact properties. A total of 18 impact scenarios comprised of asymmetric and symmetric types were performed. The effect of impact location on the impact resistance force and duration time was investigated: the closer the impact point is to the fabric center, the longer the impact duration time. In addition, the effect of impact location on impactor failure deflection was also investigated and it was concluded that regardless of the symmetric or asymmetric impact scenario, the smaller the average distance between the impact location of the two impactors from the fixed boundary, the smaller the overall average failure deflection that occurs. The relevance of impact location and fabric energy absorption capacity was also identified. Furthermore, the effect of impact location on fabric stress distribution and transverse deformation and of the variation of the impact velocity on fabric impact behaviors were investigated. These findings will provide important guidance for engineering soft body armor and composite materials.

Tendency analysis of a tilt rotor wing leading edge under bird strike events

Amongst the most critical in-service loads to be considered during the design phase to ensure the flight safety the bird strike event plays a key-role. Under this scenario, regulations pay particular attention on the wing leading edge component. In this paper, starting by a verified Finite Element (FE) modelling technique, herein discussed, a numerical tendency analysis on the leading edge of a new concept of Tiltrotor has been carried out to support its design and to have indications on the best thickness to strength ratio which is able to satisfy the crashworthiness requirements. Given the bird impact scenarios (impact locations and impact angles), different thicknesses of the metallic component have been investigated, to assess the potential weight saving hence preserving the safety of flight. The results show consistency between the investigated thicknesses and impact scenarios, giving indications for the subsequent phase of the wing design.

Response of axial-loaded steel-concrete composite walls under low-velocity impact

Steel-concrete (SC) composite walls consisting of two external steel plates and sandwiched concrete core have been employed in various engineering structures such as nuclear facilities, protective structures and high-rise buildings. Impact resistance performance is an important aspect for designing this type of structures. This paper experimentally and numerically studies the low-velocity impact response of axial-loaded SC composite walls. A total of six SC composite walls were fabricated and tested by using drop hammer to obtain damage mode, impact force and mid-span deformation. Effects of impact height (impact energy), steel plate thickness, shear connector type and axial-load ratio were analyzed. The specimens experienced severe local indentation at the impact location. As the axial-load level increased from 0 to 0.2, the indentation area, concrete cracking and global deformation was reduced, indicating the axial-load could effectively enhance the impact-resistant capacity of the SC walls. Additionally, finite element (FE) models were developed and validated using test data. The verified numerical models were then employed to analyze the impact process and energy dissipation mechanism as well as the influences of key parameters on the dynamic responses. After that, a simplified formula was suggested to estimate the maximum mid-span deformation of SC composite walls under impact loading.

Understanding the effects of ball orientation in Rugby Union place kicking: the preferences of international kickers and the kinematics of the foot-ball impact

ABSTRACT Rugby Union place kicking is influential to match outcome. Previous research has analysed kicker motion prior to ball contact in detail, but ball orientation and the impact phase are typically ignored. This study aims to firstly identify the ball orientations used by international place kickers, and secondly to experimentally analyse the foot-ball interaction in trained kickers using different ball orientations. Overall, 25.5% of the international kickers used an upright ball orientation, 27.5% used a diagonal orientation and 47.1% used a horizontal orientation. However, ball orientation preference was not significant in predicting kick outcome in a binomial logistic regression model. To address the second aim, ball orientation was experimentally manipulated and lower limb and ball kinematics were captured using high-speed (4000 Hz) video. Whilst the impact location on the ball differed significantly between most ball orientation conditions, the impact location relative to the global vertical was largely consistent across all conditions. This was likely due to kickers adopting very consistent lower limb kinematics, although the shank and ankle angles at impact were affected by ball orientation conditions for some kickers. Impact durations also differed between some conditions, although this did not appear to affect the impact efficiency.

Experimental and Numerical Study of the Influence of Pre-Existing Impact Damage on the Low-Velocity Impact Response of CFRP Panels.

This paper presents an experimental and numerical investigation on the influence of pre-existing impact damage on the low-velocity impact response of Carbon Fiber Reinforced Polymer (CFRP). A continuum damage mechanics-based material model was developed by defining a user-defined material model in Abaqus/Explicit. The model employed the action plane strength of Puck for the damage initiation criterion together with a strain-based progressive damage model. Initial finite element simulations at the single-element level demonstrated the validity and capability of the damage model. More complex models were used to simulate tensile specimens, coupon specimens, and skin panels subjected to low-velocity impacts, being validated against experimental data at each stage. The effect of non-central impact location showed higher impact peak forces and bigger damage areas for impacts closer to panel boundaries. The presence of pre-existing damage close to the impact region leading to interfering delamination areas produced severe changes in the mechanical response, lowering the impact resistance on the panel for the second impact, while for non-interfering impacts, the results of the second impact were similar to the impact of a pristine specimen.

Fiber Optic Impact Location System Based on a Tracking Tandem Low-Coherence Interferometer

This study proposes a method for detecting small-length fluctuations for fiber-optic sensors (FOS). The method is based on a tracking tandem low-coherence interferometer and enables the ability to compensate for temperature and deformation drifts in FOS. As a result, the constant high sensitivity of FOS over a wide frequency range is guaranteed. Sensitivity to the level of 2 nm in the frequency range of 200 kHz has been demonstrated. The operation of the circuit is demonstrated on the example of the 2D location of acoustic signals using a correlation algorithm for signal processing, known as the time reversal method. It is shown that this system enables us to determine the place of the impact on the sample under the test with an accuracy of about 2 cm using a single sensor.

Stress wave propagation analysis of 2D-FGM axisymmetric finite hollow thick cylinder

In this paper, a numerical axisymmetric elastic stress wave propagation analysis of the 2D-FGM hollow thick finite cylinder has been performed. The new accurate material distribution model based on Mori-Tanaka scheme and third-order transition function for 2D-FGMs has been implemented in the graded finite element method with higher-order quadrilateral elements. A non-uniform impulsive pressure has been applied on the one-third of the top inner cylinder wall. Consequently, different wave velocities and reflections from the boundaries have been observed due to the graded distribution of material along with two directions. Moreover, the effects of two-dimensional material property distributions on the stress wave propagations and displacements through the cylindrical wall at different locations have been studied systematically. Normalized effective stresses based on von-Mises criteria has been performed in comparison with the internal impulsive pressure amplitude to provide a measure of the cylinder wall response to the mechanical impact loading, the effective stresses are nearly 2.5 times the internal pressure loading amplitude, closed to the impact location. According to the results, 2D material property gradations has effected the stresses significantly. Alternatively, desired stress values can be achieved through optimal design and appropriate choice of property distribution.