Prediction Of Impact Force Research Articles

A novel machine learning framework for impact force prediction of foam-filled multi-layer lattice composite structures

Numerical simulations can provide valuable insights for the optimization of design and operational management; however, they are often impractical and computationally intensive. Machine learning methods are appealing to these problems due to their sufficient efficiency and accuracy. In this study, a novel framework for predicting the impact responses of foam-filled multi-layer lattice composite structures (FMLCSs) was proposed by combining the accurate finite element (FE) analyses, surrogate models, fast Fourier transform (FFT) method, and inverse FFT (IFFT) method. Firstly, reliable FM models were established to simulate the crashworthiness of the five FMLCSs under impact loading, including an analysis of energy transformation. Subsequently, surrogate models, namely radial basis function (RBF), polynomial response surface (PRS), Kriging (KRG), and back propagation neural network (BPNN), combined with methods of FFT and IFFT, were employed to predict the impact force-time series of the FMLCSs. More than 1000 frequency points were employed for each type of FMLCS, and all the R-square (R2) values of the established surrogate models exceeded 0.95, indicating that the proposed framework accurately predicted the impact duration and impact responses in the frequency domain. In addition, parameter sensitivity analysis revealed that a high peak impact force was accompanied by a short impact duration. Moreover, increasing the lattice-web height resulted in a significant increase in the impact duration.

Impact monitoring of large size complex metal structures based on sparse sensor array and transfer learning

During aircraft operations, the impact events experienced by the aircraft may cause damage to the structure, thus posing a safety hazard. Therefore, an accurate determination of where the impact occurred and the time history of the impact force can provide an important basis for assessing the condition of the aircraft. However, modern aircraft structures are often large and complex, and relying on dense arrays of sensors for monitoring adds additional weight to the aircraft and reduces the economics of aircraft operation. This paper proposes a region-to-point monitoring strategy. First, a Convolutional Neural Network (CNN) model with region localization capability is trained using the sparse sensor array acquisition data. Then, the weighted center algorithm is used to determine the specific location where the impact occurs, in which the added fuzzy genetic algorithm can provide the ability to adjust weights to improve localization accuracy adaptively. As for the impact force prediction, this paper adopts a model based on a Convolutional Neural Network-Gated Recurrent Unit combined with a Squeeze-Excitation attention mechanism (CNN-GRU-SE), which is capable of predicting the impact force occurring in the flat plate and reinforced structure region of the aircraft under different energy conditions. Finally, the impact of incorporating a transfer learning approach on model performance and training cost is investigated for fuselage regions with different structures.

Theoretical Prediction of Impact Force Acting on Derailment Containment Provisions (DCPs)

This study proposes a theoretical method to estimate the impact force of Derailment Containment Provisions (DCPs) for the prevention of secondary collisions in the event of a train derailment. By comparing the impact forces estimated using the commonly used Olson model and dynamic simulations, the study identifies significant differences in average and maximum impact forces. The study shows that these differences arise due to the mass effects of vehicle bodies transmitted to the DCP during a collision. To address this issue, the impact force of the Olson model was modified by considering the stiffness of suspensions between masses as a simplified spring–mass model. The modified impact force was verified through impact simulations using the KTX model on curved tracks with various radii. The results show that the modified Olson model provides a reasonable estimate of the impact force, with differences of less than 8% observed under all simulation conditions. This study provides a valuable contribution to the design and analysis methodology for DCPs, improving their effectiveness in preventing secondary collisions and enhancing railway safety.

Analysis of Feature Dimension Reduction Techniques Applied on the Prediction of Impact Force in Sports Climbing Based on IMU Data

Sports climbing has grown as a competitive sport over the last decades. This has leading to an increasing interest in guaranteeing the safety of the climber. In particular, operational errors, caused by the belayer, are one of the major issues leading to severe injuries. The objective of this study is to analyze and predict the severity of a pendulum fall based on the movement information from the belayer alone. Therefore, the impact force served as a reference. It was extracted using an Inertial Measurement Unit (IMU) on the climber. Additionally, another IMU was attached to the belayer, from which several hand-crafted features were explored. As this led to a high dimensional feature space, dimension reduction techniques were required to improve the performance. We were able to predict the impact force with a median error of about 4.96%. Pre-defined windows as well as the applied feature dimension reduction techniques allowed for a meaningful interpretation of the results. The belayer was able to reduce the impact force, which is acting onto the climber, by over 30%. So, a monitoring system in a training center could improve the skills of a belayer and hence alleviate the severity of the injuries.

Numerical prediction and experimental validation of impact sound radiation by timber joist floors

Timber joist floors are widely applied in residential buildings. The accurate prediction of the sound radiated by timber joist floors is challenging due to the interaction between the impacting mass and the floor, orthotropy of the joist and plate components, the effects of the floor size and boundary conditions, etc. In the present work, state-of-the-art approaches for the prediction of impact forces, structural vibration, and radiated sound power were combined into a prediction method for the sound pressure level in a room due to sound radiation by an impacted timber joist floor. This method was then extensively validated in a case study. The natural frequencies and mode shapes of the decoupled joists and plates were both experimentally determined and computed from finite element models, and a good agreement was found when an orthotropic material model is considered for all components. A considerable variation in material properties between nominally identical parts was also discovered. The accuracy of the floor assembly model was subsequently investigated, also by means of modal testing. It was found that a correct representation of the boundary conditions plays a key role in the accuracy of the predicted floor vibration field. Finally, the radiated sound pressure levels were measured and computed. A satisfactory agreement between measurement and computation was observed. At very low frequencies, the interaction between the floor and room modes can play an important role, and a modal room model is employed instead.

Foreign Object Damage Behavior of a Silicon Carbide Fibrous Ceramic Composite

The response of a silicon carbide (SiC) fibrous ceramic composite to foreign object damage (FOD) was determined at ambient temperature and velocities ranging from 40 to 150 m/s. Target specimens were impacted, at a normal incidence angle and in a partially supported configuration, using 1.59 mm diameter hardened steel ball projectiles. Qualitative analysis of the damage morphologies of targets and projectiles was made via scanning electron microscopy (SEM). In addition, the extent of impact damage was characterized by determining the post-impact strength of each target specimen as a function of impact velocity. Relative to the as-received (As-R) strength, the fibrous composite showed limited strength degradation due to impact with the maximum reduction of 17% occurring at 150 m/s. A quasi-static analysis of the impact force prediction was also made based on the principle of energy conservation and the results were verified via experimental data.

Prediction of the impact force on reinforced concrete beams from a drop weight

It is always a challenge to efficiently and accurately estimate the force on structures from falling objects. This study aims to predict the maximum impact force on reinforced concrete beams subjected to drop-weight impact using artificial neural network. A new empirical model including a comprehensive version and a simplified version is proposed to estimate the maximum impact force. The model was verified against a database collected from the literature including 67 reinforced concrete beams tested under drop-weight impacts. The database covers the concrete strengths ranging from 23 to 47 MPa, the projectile mass from 150 to 500 kg, and the impact velocity up to 9.3 m/s. The prediction of the comprehensive version of the proposed model fits the experimental results very well with an average absolute error of 11.6%. The simplified version of the proposed model is established for easy estimation, with the average error of 23.2% in prediction of the maximum impact force.

Prediction of impact force of debris flows based on distribution and size of particles

A debris flow is a solid-liquid two-phase flow; the composition and gradation of the particles within have a significant influence on its impact force. This paper proposes a new method for studying the impact force according to the composition of a debris flow based on analysis of existing calculation methods. The impact force is divided into three parts: (1) the dynamic pressure provided by the debris flow slurry, which is composed of fine particles and water; (2) the impact force of coarse particles; and (3) the impact force of boulders. This paper analyzes the established formulations used to calculate the impact force by using hydrodynamic theory and contact mechanics to propose a debris flow impact model according to the debris flow type. The results show that the impact force is closely related to the solid volume fraction, composition of particle materials, motion velocity, and depth of a debris flow. Among all the components of the impact force, the boulder impact force is the largest followed by the impact force of coarse particles; the dynamic pressure is minimal.

Foreign Object Damage by Spherical Steel Projectiles in an N720/Alumina Oxide/Oxide Ceramic Matrix Composite

Foreign object‐damage (FOD) phenomena of an N720/alumina oxide/oxide ceramic matrix composite (CMC), impacted by 1.59‐mm spherical chrome steel projectiles up to Mach 1, were assessed at ambient temperature at a normal incidence angle in both partial and full supports. The impact damage was in the form of craters, matrix/fiber tow breakage, compaction of the material, delamination and cone cracks, and their occurrence and degree depended on both impact velocity and type of target supports. The partial support resulted in significant damage with increasing impact velocity, accompanying substantial strength degradation. The presence of tensile stress and presumably stress wave interaction at the backside of a target could have been responsible for greater impact damage in partial support. Although the CMC targets impacted at 340 m/s were on the verge of being penetrated, the targets still survived catastrophic failure retaining about 68% of the as‐received strength, indicative of relatively superior FOD resistance as compared to monolithic ceramic counterparts. A quasi‐static analysis of impact force prediction was made based on the energy balance principle and was validated indirectly using the experimental data on frontal impact damage size.

Prediction of impact force in sideways fall by image-based subject-specific dynamics model

The impact force applied to the greater trochanter during sideways fall is a critical factor for determining whether or not a hip fracture would occur. However, the impact force is subject-dependent as it is related to the subject’s anthropometric parameters and the kinematic variables in fall. It cannot be accurately predicted by the currently available dynamics models. We developed and validated a method for constructing subject-specific dynamics models to more accurately predict the impact force. The anthropometric parameters required in the model were obtained from the subject’s whole body DXA (dual energy X-ray absorptiometry) image. The subject-specific dynamics models were then validated by protected fall tests using young volunteers. The effects of anthropometric parameters on the impact force were investigated using 90 clinical DXA images obtained from a local osteoporosis clinic center. The impact forces predicted by subject-specific dynamics models had much better agreement with the experimental data, compared with those predicted by the existing empirical functions. The parametric study results indicated that although body weight and height are the dominant parameters affecting the impact force, other parameters such as the hip vertical velocity before impact also have considerable effects. This finding suggests that the existing empirical functions that only consider body weight and height may not be able to accurately predict the impact force. As whole body DXA images are readily available in osteoporosis clinic centers, the proposed method may have potential applications in the clinic to improve the assessment of fall-induced hip fracture risk.

The influence of contact modelling on simulated wheel/rail interaction due to wheel flats

Most available wheel/rail interaction models for the prediction of impact forces caused by wheel flats use a Hertzian spring as contact model and do not account for the changes in contact stiffness due to the real three-dimensional wheel flat geometry. In the literature, only little information is available on how this common simplification influences the calculation results. The aim of this paper is to study the influence of contact modelling on simulated impact forces due to wheel flats in order to determine the errors introduced by simplified approaches. For this purpose, the dynamic wheel/rail interaction is investigated with a time-domain model including a three-dimensional (3D) non-Hertzian contact model based on Kalker's variational method. The simulation results are compared with results obtained using a two-dimensional (2D) non-Hertzian contact model consisting of a Winkler bedding of independent springs or alternatively a single non-linear Hertzian contact spring. The relative displacement input to the Hertzian model is either the wheel profile deviation due to the wheel flat or the pre-calculated vertical wheel centre trajectory. Both the 2D model and the Hertzian spring with the wheel centre trajectory as input give rather similar results to the 3D model, the former having the tendency to slightly underestimate the maximum impact force and the latter to slightly overestimate. The Hertzian model with the wheel profile deviation as input can however lead to large errors in the result. Leaving aside this contact model, the correct modelling of the longitudinal geometry of the wheel flat is actually seen to have a larger influence on the maximum impact force than the choice of contact model.

Uncertainty in Impact Identification Applied to a Commercial Wind Turbine Blade

This work evaluates the uncertainty of impact force and location estimates using an entropy-based impact identification algorithm applied to a commercial wind turbine blade. The effects of sensor placement, measurement directions and distance between impacts and sensor locations are studied. Results show that impacts to a 35m long wind turbine blade can be accurately located using a single tri-axial accelerometer regardless of sensor location. Uncertainties in impact force estimates are consistent across sensor locations. When omitting acceleration information in the spanwise direction, the bias and variance of force estimates is consistent, but when a single chan- nel of acceleration data is used, both increase somewhat. Impact force identification error was found to be uncorrelated with the distance between the impact and sensor location. The entropy of the estimated force time history, an indicator of the impulsivity of the estimate, was found to be a good indicator of the quality of force estimate. The bias and variance of impact force estimation error was found to be directly correlated with the entropy of the impact force estimate. When considering validation test data from all possible sensor configurations, the entropy of the recreated force estimates was a better indicator of the force magnitude prediction interval than was the specific sensor configuration. By classifying impact force estimates based upon entropy values, impact force prediction intervals were more precisely determined than when all validation impact data were considered at once.

Prediction of geometrical properties of perfect breaking waves on composite breakwaters

Breaking wave loads on coastal structures depend primarily on the type of wave breaking at the instant of impact. When a wave breaks on a vertical wall with an almost vertical front face called the “perfect breaking”, the greatest impact forces are produced. The correct prediction of impact forces from perfect breaking of waves on seawalls and breakwaters is closely dependent on the accurate determination of their configurations at breaking. The present study is concerned with the determination of the geometrical properties of perfect breaking waves on composite-type breakwaters by employing artificial neural networks. Using a set of laboratory data, the breaker crest height, h b , breaker height, H b , and water depth in front of the wall, d w , from perfect breaking of waves on composite breakwaters are predicted using the artificial neural network technique and the results are compared with those obtained from linear and multi-linear regression models. The comparisons of the predicted results from the present models with measured data show that the h b , H b and d w values, which represent the geometry of waves breaking directly on composite breakwaters, can be predicted more accurately by artificial neural networks compared to linear and multi-linear regressions.

Finite Element Analysis on the Impact-induced Damage of Composite Fan Blades Subjected to a Bird Strike

Carbon fiber-reinforced composites have been recently applied for engine fan blades because of their high specific strength. In the design of the fan blade, bird-strike impact is one of the greatest concerns, since impact-induced damage can lead to the engine stalling. This study presents a numerical method to analyze bird-strike impact as a soft-body impact on a cantilevered composite panel. Especially, we coupled a stabilized dynamic contact analysis, which enables appropriate prediction of impact force on the panel, with laminate damage analysis to predict the impact-induced progressive damage in the composite. This method is verified through a comparison with experimental results. With the numerical method, we investigate the effect of impact condition, blade thickness and shape on the impact-induced damage in a composite fan blade subjected to a bird strike. An intermediate blade thickness and a large blade curvature help to improve the bird-striking impact resistance of the composite.

Numerical Prediction of Impact Force in Cavitating Flows

A numerical method including a macroscopic cavitation model based on the homogeneous flow theory and a microscopic cavitation model based on the bubble dynamics is proposed for the prediction of the impact force caused by cavitation bubble collapse in cavitating flows. A large eddy simulation solver, which is incorporated with a macroscopic cavitation model, is applied to simulate the unsteady cavitating flows. Based on the simulated flow field, the evolution of the cavitation bubbles is determined by a microscopic cavitation model from the resolution of a Rayleigh–Plesset equation including the effects of the surface tension, the viscosity and compressibility of fluid, the thermal conduction and radiation, the phase transition of water vapor at the interface, and the chemical reactions. The cavitation flow around a hydrofoil is simulated to validate the macroscopic cavitation model. A good quantitative agreement is obtained between the prediction and the experiment. The proposed numerical method is applied to predict the impact force at cavitation bubble collapse on a KT section in cavitating flows. It is found that the shock pressure caused by cavitation bubble collapse is very high. The impact force is predicted qualitatively compared with the experimental data.

Numerical prediction of impact force in cavitating flows

An analytical method including a macroscopic cavitation model based on the homogeneous flow theory and a microscopic cavitation model based on the bubble dynamic was proposed for the prediction of the impact force caused by cavitation bubbles collapse in cavitating flows. A Large Eddy Simulation (LES) solver incorporated the macroscopic cavitation model was applied to simulate the unsteady cavitating flows. Based on the simulated flow field, the evolution of the cavitation bubbles was determined by a microscopic cavitation model from the resolution of a Rayleigh-Plesset equation including of the effects of the surface tension, the viscosity and compressibility of fluid, thermal conduction and radiation, the phase transition of water vapor at interface and chemical reactions. The cavitation flow around a hydrofoil was simulated to validate the macroscopic cavitation model. A good quantitative agreement was obtained between the prediction and the experiment. The proposed analytical method was applied to predict the impact force at cavitation bubbles collapse on a KT section in cavitating flows. It was found that the shock pressure caused by cavitation bubble collapse is very high. The impact force was predicted accurately comparing with the experimental data.

Foreign object damage behavior in a silicon nitride ceramic by spherical projectiles of steels and brass

Assessments of foreign object damage (FOD) of a commercial, gas-turbine grade, in situ toughened silicon nitride ceramic (AS800) were made using different projectile materials at ambient temperature. AS800 flexure target specimens rigidly supported were impacted at their centers in a velocity range from 100 to 450 m/s by spherical projectiles with a diameter of 1.59 mm. Three different projectile materials were used including hardened steel, annealed steel, and brass. Post-impact strength of each target specimen impacted was determined as a function of impact velocity to appraise the severity of local impact damage. For a given impact velocity, the extent of FOD was greatest for hardened steel projectiles, least for brass projectiles, and intermediate for annealed steel projectiles. The key material parameter affecting FOD the most was identified as the hardness (or yield stress) of projectile materials. Prediction of impact force as a function of impact velocity for each projectile material was made based on a quasi-static plastic model incorporated with the average ‘contact yield pressure’ determined from static indentation testing.

A fast time-domain model for wheel/rail interaction demonstrated for the case of impact forces caused by wheel flats

The prediction of impact forces caused by wheel flats requires the application of time-domain models that are generally more computationally demanding than are frequency-domain models. In this paper, a fast time-domain model is presented to simulate the dynamic interaction between wheel and rail, taking into account the non-linear processes in the contact zone. Track and wheel are described as linear systems using impulse-response functions that can be precalculated. The contact zone is modelled by non-linear contact springs, allowing for loss of contact. This general model enables the calculation of the vertical contact forces generated by any kind of roughness excitation between wheel and rail. Here, the model is adapted to the excitation caused by wheel flats by introducing the irregular wheel shape as a form of extreme roughness. A brief parameter study is presented to demonstrate the functioning of the model. The results from the model are discussed and compared with results from literature.

A Solution of the Ill-Posed Impact-Force Inverse Problems by the Weighted Least Squares Method

This paper deals with an inverse problem of impact-force prediction. The force is expressed in a set of expansion functions; hence, the original governing equation is reformulated to a problem of finding the weight of each expansion function. The expansion function is designed to best approximate the impact-force profile. The approach allows us to take into account more priori information of the solution; consequently, a better solution can be obtained. A numerical verification shows the estimation error of the present method is 3%, while the error of the Tikhonov solution is 18.5%.

Prediction of Impact Forces on an Aircraft Composite Wing

The capabilities for monitoring impact forces on an aircraft composite wing using impact response function (IRF) are examined. The IRF is derived based on the finite element method (FEM). Impact locations are identified by minimizing strain errors and force deviation errors. The reconstruction of impact forces are performed by computational inverse methods. The results of impact location identifications and impact force reconstructions are verified by numerical simulations using finite element analysis.