Impact Location Research Articles

Localization of impact on CFRP structure based on fiber Bragg gratings and CNN-LSTM-Attention

Low-velocity impacts can cause microscopic and invisible damage to carbon fiber reinforced polymer (CFRP) structures, potentially compromising their integrity and leading to catastrophic failures. Therefore, obtaining precise information about the impact location is crucial for monitoring the health of CFRP structures. In this paper, an impact localization system for CFRP structures was developed by using fiber Bragg grating (FBG) sensors, and impact signals detected by FBG sensors are demodulated by edge-filtering at high speed. An impact localization method of CFRP structure based on CNN-LSTM-Attention is proposed. The time difference of arrival (TDOA) between signals from different FBG sensors are collected to characterize the impact location, and attention mechanism is introduced into the CNN-LSTM model to augment the significance of TDOA of impact signal detected by proximal FBG sensors. The model is trained using the training set, its parameters are optimized using the validation set and the localization performance of different models are compared by the test set. The proposed impact localization method based on CNN-LSTM-Attention model was verified on a CFRP plate with an experiment area of 400 mm*400 mm. Experimental results prove the effectiveness and satisfactory performance of the proposed method.

Damage quantification based on drift ratios and axial capacity degradation for RC columns under low-velocity impact loads

Damage determination and quantification are critical issues in conducting damage assessment and performance-based design for RC columns under low-velocity impact loads. An impediment in these issues lies in defining reasonable damage criteria. To this end, a framework inspired by existing experimental results is proposed to quantify the damage of RC columns. The core concept of this framework is to establish the relationship between the engineering demand parameter (i.e., drift ratio) and the damage index based on residual axial capacity and to convert the damage index threshold to the drift ratio threshold using a reliability-based method. According to the proposed framework, damage criteria are developed for RC columns in two typical impact scenarios, including the mid-span and near-base impacts. During this process, linear relationships between the maximum drift and the residual one at the impact location are developed by statistically analyzing the existing experimental data (a total of 212 test samples). Based on experimentally validated numerical models, empirical formulas for estimating the residual axial capacity of RC columns are established. The maximum drift, the residual drift, and the axial capacity degradation are interrelated in the proposed damage criteria, overcoming the limitation that the current deformation-based damage criteria used for low-velocity impact loads lack physical significance.

Dynamic response of clamped sandwich beams with foam-filled sinusoidal corrugated core subjected to low-velocity impact

Sandwich structure is a lightweight structure with high specific strength and specific stiffness, as well as excellent energy absorption and load-carrying capacity. Sandwich structures are widely used in aerospace, high-speed rail and marine applications. Low-velocity impact of a sandwich beam with foam-filled sinusoidal corrugated core is investigated by means of theoretical derivations and numerical calculations. A yield criterion is used to obtain an analytical solution of the dynamic behavior of champed sandwich beams with foam-filled sinusoidal corrugated cores under low-velocity impact. Numerical calculations are performed. The analytical results are in excellent accordance with the finite element results. Influences of the amplitude, half-wavelength and thickness of the sinusoidal corrugated plate, foam strength, metal-sheet strength, and the impact location on the dynamic behavior of the sandwich beams with foam-filled sinusoidal corrugated cores under low-velocity impact are discussed. The present analytical model can predict reasonably well the dynamic behavior of foam-filled sinusoidal corrugated core sandwich beams under low-velocity impact.

Damage to a High Bypass Ratio Fan During Uas Ingestions

Abstract Foreign object ingestion into engines has been studied for many years, but the focus has been on soft bodies (i.e., birds, ice). Recently, there has been a dramatic increase of uncrewed aircraft systems (UAS) in the airspace that represent a new threat to aircraft engines due to key components like the motor, battery, and camera being composed of hard components. Due to the differences between hard bodies and soft bodies, studies are required to understand the new threat these UAS pose to aircraft. The objective of this study is to investigate the impact of various factors such as impact orientation, fan rotational speed, relative translational speed, and radial impact location on the damage caused to a representative fan assembly. This study aims to analyze the sensitivity of these factors and their influence on the overall damage to the fan. The ingestion simulations will use a representative fan assembly model and a UAS model that has been experimentally validated at the conditions of an ingestion. This work will identify critical parameters of the ingestion and then utilize them to anticipate the extent of damage that may arise during specific stages of a flight where an ingestion is most probable. Moreover, it also compares these cases with some known baseline cases, such as a fan blade out and bird ingestion of similar mass, to understand the likely severity compared to more studied common cases.

Experimental and Simulation Studies on Protective Structures in Floating Dock

In this research, two distinct designs of protective structures were developed to address structural damage caused by ships impacting the internal structures of floating docks during maintenance operations. The designed protective structures consist of support sections and load-bearing sections, with the load-bearing section comprising three frame sections. For ease of description, the front frame section, middle frame section, and rear frame section are referred to as Frame A, Frame B, and Frame C, respectively. A drop-weight test was conducted with a stern-shaped indenter impacting the structures at 3.89 m/s. This study also assessed varying impact speeds and positions. The results showed that Specimen 2 had localized indentations on Frame B, while Specimen 1 exhibited overall deformation of Frame B and additional deformations in Frame A. The simulations agreed with the experimental results, confirming the model’s accuracy. At speeds from 2.34 m/s to 5.45 m/s, Specimen 2 consistently showed localized deformations, while Specimen 1 showed comprehensive deformation of Frame B at 3.89 m/s due to lower rigidity. When the indenter impacted the specimens at different locations with a speed of 5.45 m/s, the two specimens exhibited varying degrees of damage. As the impact location shifted from the central area to the end, the maximum indentation depth of Specimen 1 decreased from 52.26 mm to 41.71 mm, while that of Specimen 2 decreased from 43.26 mm to 38.50 mm. The reduction in indentation depth and extent as the impact location approached the support frame can be attributed to the increasing involvement of the web plate beneath the frame in resisting the impact. Additionally, compared to Specimen 1, Specimen 2 exhibited a relatively smaller overall indentation depth, and the impact of location variation on indentation depth was also relatively minor.

The effect of baseball bat properties and participant ability on youth hit ball speed

The following describes the results of a batting cage study involving youth batters hitting with three types of baseball bats in two weight classes. Participants were allowed to select a bat length from within each type and weight according to their preference. The bats were then swung in random order. Reflective markers were placed on the bats and balls, allowing infrared cameras to track their motion from which speed was obtained. Given the differing ability of the participants, the study outcomes were normalized to the swing speed of each batter. Bat performance was quantified from the bat-ball coefficient of restitution. Laboratory measures of bat performance were shown to strongly correspond with the peak batting cage results. The ball exit speed of hollow bats exceeded that of traditional solid wood bats by as much as 5%. The ball exit speed was also found to be affected more by players’ ability than the bat type. Batter swing speed correlated strongly with bat inertia and was relatively insensitive to the bat-ball impact location, showing that participant effort was not biased by impact quality. Batter swing speed tended to depend more strongly on bat inertia than has been found in adult studies, which may be due to the smaller size of youth participants.

Evaluating load-bearing and hypervelocity impact shielding capabilities of face-centered cubic lattice core sandwich panels

In the present paper, a comparative study on load-bearing as well as hypervelocity impact shielding performance of sandwich panels with face-centered cubic (FCC) lattice core is numerically performed in order to evaluate their competency in satellite structure applications. To this end, 5A06 aluminum alloy FCC and FCCz beside cube and octahedron lattice structures with similar areal densities were investigated. Whipple shield structure of same material and areal density was also studied in order to be compared to lattice structure in protection field. The present study simulates hypervelocity impact of a spherical projectile with 2 mm diameter, represents the space debris, collides with the structures at the velocity range of 2–6 km/s. Numerical simulation model was validated by performed experimental study. Authors were inspired by cube and FCCz topologies to propose a novel lattice structure could provide outstanding shielding and load-bearing capabilities in comparison to the other structures studied in this research. Furthermore, the detailed effects of projectile impact location on the protection performance were investigated and the mentioned item was found to have considerable influence on the structure shielding performance.

Effect of impact position on the mechanical response and viscoelastic behavior of double‐blade composite stiffened structures

AbstractThis paper focuses on the mechanical response and viscoelastic properties of double‐blade composite stiffened structure (DCSS) under low‐velocity impact (LVI). Firstly, the impact resistance and viscoelastic behavior of the DCSS are revealed by LVI testing at four different locations using the same initial velocity. Next, the damage morphologies at the impact locations are observed with ultrasonic A‐ and C‐scan equipment and optical microscopy. At last, the DCSS containing impact damage is implemented for axial compression and the strain values of the DCSS surface are obtained using a strain testing system to reveal its residual properties and buckling behavior. The results show that there are significant differences in the impact damage modes at the four different locations. The maximum impact resistance is observed at location D, while location A has the opposite. The DCSS has a certain viscoelastic behavior at LVI and conforms to an exponential decay model. Moreover, position B presents interface debonding damage due to stiffness discontinuities at the flange and skin bonding and severely weakens the load carrying performance of the DCSS.Highlights The impact resistance of different positions is analyzed by LVI experimental results. Viscoelastic properties exist at different impact locations and obey the exponential decay model. Impact damage alters the buckling load and residual strength of the DCSS. The damage mechanism of the triangular zone is revealed by damage morphology.

Strain waves on additively manufactured plates for an on-orbit impact detector concept

Orbital debris impacts on spacecraft are an emerging threat to space missions due to the exponential increase in the number of satellites orbiting the Earth. Debris characteristics (size, material, velocity, etc.) are not well known for the size range of 10 mm or less that is undetectable using Earth telescopes or radar observation. The objective of this research was to determine wether a concept designed to detect impact of particles in the ∼1 to 5 mm range, find the location of the impact, and characterize the impacting projectile (velocity, size, angle, density), is feasible.The paper describes the design, fabrication, and tests performed on “witness plates” (the concept) made of two parallel layers of additively manufactured aluminum and instrumented with sixteen gages, eight on each layer. Laboratory experiments have shown that the waves can be recorded and properly interpreted to find location of impact, sound speed in the plate, and to estimate impact velocity. It was shown analytically that the amplitude of the first strain wave that propagates from the impact point is expected to decay as 1/r. This was observed as well in the signals recorded in the experiments. CTH computations were performed during the pre-test design phase and the post-test analysis phase. In fact, the numerical simulations have been key and pervasive in this research effort as they provided invaluable insight for the initial design and the correct interpretation of signal anomalies seen during the tests. Additionally, the computations confirmed the 1/r law derived analytically, i.e. that the assumptions for the derivation were justified. The main conclusions of the research are that, for a normal impact, the 1/r law for front gages can be easily used to determine the diameter of the impactor. It is possible that the back gages could be used to determine the density of the impactor as well. Finally, it was shown that oblique impacts generate an expected assymetry in the signals recorded. Though this aspect should be investigated further, the assymetry is probably uniquely related to the impact angle, which could provide the angle information.

Evaluation of comfort zone boundary based automated emergency braking algorithms for car‐to‐powered‐two‐wheeler crashes in China

AbstractCrashes between cars and powered two‐wheelers (PTWs: motorcycles, scooters, and e‐bikes) are a safety concern; as a result, developing car safety systems that protect PTW riders is essential. While the pre‐crash protection system automated emergency braking (AEB) has been shown to avoid and mitigate injuries for car‐to‐car, car‐to‐cyclist, and car‐to‐pedestrian crashes, much is still unknown about its effectiveness in car‐to‐PTW crashes. Further, the characteristics of the crashes that remain after the introduction of such systems in traffic are also largely unknown. This study estimates the crash avoidance and injury risk reduction performance of six different PTW‐AEB algorithms that were virtually applied to reconstructed car‐to‐PTW pre‐crash kinematics extracted from a Chinese in‐depth crash database. Five of the algorithms include combinations of drivers’ and PTW riders’ comfort zone boundaries for braking and steering, while the sixth is a traditional AEB. Results show that the average safety performance of the algorithms using only the driver's comfort zone boundaries is higher than that of the traditional AEB algorithm. All algorithms resulted in similar distributions of impact speed and impact locations, which means that in‐crash protection systems likely can be made less complex, not having to consider differences in AEB algorithm design among car manufacturers.

Analysis of Bullet Impact Locations in the 10 m Air Pistol Men’s Competition Based on Covariance

The purpose of this study was to quantify the bullet impact locations of the men’s 10 m air pistol competition and propose objective metrics for evaluating shooting techniques. We automatically collected data from the top 20 competitors’ shooting results using computer vision techniques. Metrics such as x-variance, y-variance, covariance, x-mean, y-mean, root mean square error (RMSE), x-mean score, and y-mean score were computed to investigate correlations among rankings, left–right and up–down shot groups, aiming relationships, and precision. Covariance analysis revealed significant interactions between horizontal and vertical aiming, highlighting the importance of balanced coordination between these directions for high performance. Athletes with lower covariance values, indicating less variation between horizontal and vertical aiming, tended to achieve higher rankings. Additionally, top-ranked athletes exhibited lower RMSE values, underscoring the importance of precision in achieving high scores. In conclusion, this study analyzed the correlation between x and y through covariance, examined its relationship with competition rankings, and proposed new indicators for training and performance enhancement. This study is novel in that it provides quantitative data to correct poor aiming and shooting habits by performing a covariance-based bidirectional correlation analysis, rather than simply analyzing bullet impact locations in a single horizontal or vertical direction. Our approach establishes a foundation for more data-driven and objective evaluations in the sport of shooting.

Experimental and numerical investigation on low-velocity impact damage and parametric study of composite rotor blades

Modern helicopter rotor blades are made of composite materials. Due to the harsh service environment, the blades may be impacted by hail and other falling objects at low velocity. The damage behavior of composite rotor blades subjected to low-velocity impact is studied here. Low-velocity impact experiment is conducted on a composite helicopter rotor blade, and the impact force and the damage are measured. Based on the experiment, a finite element model is developed and validated to predict the impact damage of the blade. With the model, a parametric study is performed to investigate the effects of impact energy, impact locations, and foam core on impact responses of the composite blades. The results show that the rib is the most vulnerable part to damage, associated with severe deformation, and delamination rapid expanding under low-velocity impact. The foam crush region is close to the blade top surface below the impact point. The interface between the skin and internal part is especially sensitive to increase in impact energy. Impacts near the leading edge produce higher impact force, while impacts near the trailing edge cause large deformation and small impact force. Better impact performance will be achieved when modulus and density of the foam are increased.

Study on ballistic impact performance of bionic fish scale protective armor

Composite bulletproof armor used in modern battlefield environments is mostly composed of ceramic/ultra-high molecular weight polyethylene (UHMWPE). In order to further improve its bulletproof performance, this study draws on the superposition of fish scales. The upper layer of the flexible protective armor consists of composite scale layers stacked on top of each other, and the lower layer consists of UHMWPE plates with grooved structures at the corresponding locations of the scales, where a single composite scale consists of an upper SiC ceramic layer and a lower UHMWPE layer. Finite element simulation is used to analyze the protective performance of the protective armor. The effects of back plate thickness, scale tilt angle, and impact location on the protection performance are investigated. The results show that the 8 mm thick back plate can effectively resist the impact of Type 53 7.62 mm armor-piercing incendiary ammunition, and the protective effect is best when the scale tilt angle is 30°. The maximum depression depth of the backplane is 12.4 mm, and the deformation of the backplane is reduced by 3 mm when the bullet hits the overlapping area of the scale compared with the central area of the target scale, accounting for 32.67% of the total deformation. The research work has guided the development of new bionic flexible protective armor.

Acoustic emission source localization for complex structure with multi-holes based on heuristic adaptive pathfinding and gradient descent method

Space debris poses a safety hazard to the operation of spacecraft, and the study of impact localization for spacecraft structures is of significance for the timely discovery of the impact location and the safeguarding of spacecraft and personnel safety. However, existing studies have mainly focused on continuous structures, and discontinuous structures of spacecraft with portholes and orifice-containing valves have been understudied. Therefore, in this article, the shortest propagation path algorithm of the signal and the acoustic emission source localization method applicable to multi-holes discontinuities structures are proposed. After calculating the signal arrival time difference, the localization method calculates the shortest propagation path of Lamb wave in complex multi-holes structure by the heuristic adaptive path-finding algorithm, which calculates distance differences traveled by the signal propagation to each sensor. The heuristic adaptive path-finding algorithm first constructs a map set based on the geometrical features of the structure, after which it searches for each partial path in the final path by heuristic computation to identify the shortest signal propagation trajectory. The objective function is established based on the target structural characteristics and sensor position parameters, of which the parameters of the equations are optimized based on the new travel difference-of-distance values generated from the results of the heuristic adaptive pathfinding calculation. Finally, the acoustic emission source coordinates are updated with a gradient descent strategy, which has an average localization error of 0.956 cm in 252 experiments and can effectively realize the impact localization calculation of multi-holes complex structures.

Reversing the gaze: understanding how community members are negatively affected by impact assessment

ABSTRACT This study addresses the persistent tensions in Impact Assessment (IA), which aim to balance public engagement with technical analysis. In this context, the IA process itself poses a significant risk to the individuals and communities involved in the impact assessment. The consequences of these risks, and whether they materialize, remain uncertain and depend on the specific context of each IA process. Drawing on the sociology of risk and broader IA literature, we present a case study of the Grassy Mountain Coal Project in southern Alberta, Canada. Instead of evaluating project-specific impacts within the IA process, we examine the impacts of the IA process on community members. By reversing our gaze, we aim to understand how IA processes impact communities and how these impacts manifest. Led by the results of the study, the impacts of the IA on community members are examined under three specific impact locations: (1) risk perceptions and anticipatory impacts, (2) procedural issues, and (3) community and regional conflicts. Our conclusions underscore the need to recognize these types of impact on communities and explore ways to minimize the costs of IA to communities.

Validation of an Abaqus impact wave propagation model

Structural Health Monitoring (SHM) is an important topic in aircraft industry to reduce the maintenance costs and increase the availability of an aircraft fleet through automating the determination of the health of the aircraft structure and systems using on-site sensors, like piezoelectric (PZT) and optic fibre Bragg grating (FBG) sensors that are often applied in SHM sensor networks. A finite element model for wave propagation due to an impact is very desirable to enable the design of optimal sensor network configurations for SHM applications, to obtain a better understanding of wave propagation (especially in composite structures) and also to generate simulated (virtual) test data for SHM algorithm development. Therefore, an Abaqus explicit finite element (FE) model was developed for wave propagation due to impacts. To validate such a model, a series of impact tests were performed with a drop tower on an aluminium clamped square panel, at different impact energy levels and different impact locations. On the panel, eight FBG and six PZT sensors were installed. These experimental results were used to validate the FE model, in which the impacts were simulated and the computed PZT and FBG sensor responses were compared against the experimental results. The paper will present the impact test setup, the finite element model and the validation results. The main focus of the paper will be the sensitivity analysis, identifying the model parameters that significantly affect the impact sensor responses and their optimal settings. A very good correlation between the numerical and experimental results was obtained. In near future work, the model will be extended to a (thermoplastic) composite panel, for which experimental results on a flat composite panel already have been collected, and a stiffened composite panel representative of an actual horizontal tail plane are planned.

Low-velocity impact localization on a full composite wing of UAV using fiber optic sensors under operating environments

In this paper, low-velocity impact localization algorithms were suggested using fiber optic sensing system. In order to obtain high frequency signals due to low-velocity impact, a commercial high speed fiber Bragg grating (FBG) sensing system (a sampling speed of 100 kHz) was adopted. The test article is a full-scale composite wing box structure as the main wing of an unmanned aerial vehicle. The multiplexed FBG sensor array was attached on the lower surface of the upper skin. Low-velocity impact experiments were performed to obtain the impact signals for the reference data set. The reference data set is composed of the impact signals from the impacts on the reference points. The suggested algorithm in this study is based on the comparisons between impact signals and the reference signals in the database set. The main idea is to determine the reference point which has the most similar data set as the impact location. This idea was validated from the experiments of the non-reference points. As the next step, operational environments were considered to enhance the reliability of the suggested algorithm. The considered environments are the static loads and vibrations. These days, most of UAVs use the electric motors and propellers as the main propulsion system. Thus, harsh vibrations inherently occur and affect the performance of impact localization algorithms. From the experiments under these operating environments, it can be checked that the suggested algorithm has sufficient robustness to such environments.

Consequences of thermal aging on the detection of impact damage in composite structures with PZT/FBG guided wave systems

In the context of recent reusable launch vehicles (RLV) developments, SHM could help fast and economic revalidation of RLVs between launches, provided that the transducers keep their functionality and reliability after repeating launches being exposed to harsh flight conditions. This paper studies the detection of barely visible impact damage in composite plates with guided waves (GW) based SHM systems. More precisely, it focuses on how this detection can be affected by the degradation of the sensors potentially induced by the exposition to flight conditions. The aging conditions in this work mainly consist of thermal cycling with high maximum temperature (150°C), expected for RLV structures and close to the operational limit of the thermoset-matrix composite. The response of the sensors to such environmental conditions depends on the sensor itself and on its bonding to the structure. Thus, in this paper two different types of sensors are tested (commonly used PZT transducers and FBG sensors) along with two different bonding methods (classic bonding with a secondary adhesive and cobonding on composite surface during the curing process). The sensors are setup in pairs (PZT-PZT or PZT-FBG) with GW signal paths going through the impact location. After a baseline acquisition, incremental impact tests (with increasing energy) are performed and GW signals are acquired after each impact to assess the damage signature on the waveform. Then after submitting the plate to thermal cycling, GW signals are recorded again to assess its effect on the damage detection performance and on the risk of false alarms (mistaking sensor degradation for structural damage). Sensor degradations are monitored through non-destructive techniques and impedance self-diagnostic measurements for PZT. Additionally to this aging test, the responses of degraded sensors previously studied by the authors are compared with the impact signature to assess how those degraded sensors could harm the impact detection.

Understanding post-impact biomechanics of ballistic cranial injury by smoothed particle hydrodynamics numerical modelling

AbstractVirtual crime scene investigation using numerical models has the potential to assist in the forensic investigation of firearm-related fatalities, where ethical concerns and expensive resources limit the scope of physical experiments to comprehend the post-impact biomechanics comprehensively. The human cranial numerical model developed in this study incorporates three main components (skin, skull, and brain) with dynamic biomaterial properties. The virtual model provides valuable insights into the post-impact biomechanics of cranial ballistic injuries, particularly in high-speed events beyond conventional investigative capabilities, including the velocity of ejected blood backspatter, cavitation collapsing, and pressure waves. The validation of the numerical model, both quantitatively and qualitatively, demonstrates its ability to replicate similar bone fractures, entrance wound shapes, and backward skin ballooning observed in physical experiments of the human cranial geometry. The model also yields similar temporary cavity sizes, wound sizes, and blood backspatter time against the physical cranial model, aiding in bloodstain pattern analysis. Additionally, the numerical model enables exploration of ballistic factors that vary in each crime scene environment and influence cranial injuries, such as projectile type, velocity, impact location, and impact angle. These established injury patterns contribute to crime scene reconstruction by providing essential information on projectile trajectory, discharge distance, and firearm type, assisting in the resolution of court cases. In conclusion, the developed human cranial geometry in this study offers a reliable tool for investigating firearm-related cranial injuries, serving as a statistical reference in forensic science. Virtual crime scene investigations using these models have the potential to enhance the accuracy and efficiency of forensic analyses.

Time of Arrival Extraction for Impact Localisation on Composite Structures

Time of arrival (TOA) serves as a widely utilised metric for pinpointing impact locations on composite aircraft structures. Nevertheless, the effectiveness and reliability of existing TOA extraction methods across diverse impact scenarios remains unclear. This study aims to comprehensively assess the effectiveness of established TOA extraction methods for impacts on composite structures, employing both analytical and experimental approaches.