Axial Impact Research Articles

Crashworthiness design of functional gradient bionic structures under axial impact loading

Gradient structures have become a hot research topic because of their excellent crashworthiness. Inspired by the gradient distribution of human bone and the excellent energy absorption properties of thin-walled constructions, a novel biologically inspired functionally graded lattice-filled tube (FGLT) is proposed in this paper by combining a radial gradient lattice with a thin-walled structure. Lattice arrays with different gradient patterns were prepared by laser melting (SLM) technique and embedded in square thin-walled tubes for experimental crashworthiness study. It was found that there was a 25.47% increase in specific absorption energy of uniform lattice-filled tubes with respect to empty tubes, and a 36.65% increase in specific absorption energy of graded grating filled tubes with respect to empty tubes. It is noteworthy that the peak load of the structure is only improved by 3.95% compared to the empty tube for the gradient lattice as a filler embedded in the thin-walled tube. Finally, based on the response surface methodology (RSM) and the second-generation non-dominated ranking genetic algorithm (NSGA-II), the multi-objective optimization of the new bionic gradient structure with the maximum specific energy absorption and the minimum peak load is performed. The expression of the maximum standardized impact force is obtained by dimensionless processing, which can fully explore the influence of the structural parameters on the impact load. The functional gradient bionic structure provides new ideas for the design of more effective energy absorption structures and collision avoidance systems.

Experimental investigation on cenosphere-aluminum syntactic foam-filled tubes under axial impact loading

Experimental investigation on cenosphere-aluminum syntactic foam-filled tubes under axial impact loading

Crashworthiness analysis and optimization of a novel “cake-cutting” multi-cell tube

Increasing the number of corners can effectively increase the energy absorption of thin-walled tubes. To obtain a thin-walled tube with better energy absorption performance, a novel type of multi-cell thin-walled tube is formed by adding three rib plates, imitating the way of cutting a cake. The rib plates can divide the circular tube into multi-cell tubes with different numbers of multi-cells, and numerical simulations are conducted for the crashworthiness analysis under the axial and oblique impact loadings. The results show that the deformation mode under axial impact is more stable when the number of "cakes" is maximum, and the specific energy absorption is increased by 46% compared with the traditional circular thin-walled tube. Then, a multi-objective optimization framework is employed to find the cutting configuration for better crashworthiness performance. It is found that the optimal multi-cell tube inspired by the “cake-cutting” method can increase energy absorption by 17.4% compared with the original tube. This cake-cutting method provides an innovative designing idea of a thin-walled structure for energy absorption.

Crashworthiness analysis and structural optimization of shrink tube under interference condition

This paper aims to study the crashworthiness of shrink tubes for rail vehicles under axial impact loading. A theoretical model of shrink tube for platform force prediction under interference fit conditions was proposed. The trolley crash test was used to experimentally study the structural energy absorption and characteristics during collision, and a corresponding finite element model was constructed and validated. The finite element model validated the accuracy of the theoretical model. The influence of structural parameters on the crashworthiness of shrink tube under interference conditions was then studied. Structural design variables, including the magnitude of interference (int_pre), thickness (T), long right-angle edge (tri_x) and short right-angle edge (tri_z) were sampled using a full factorial and a Latin hypercube design method. Based on the above samples, the moving least squares method (MLSM) was used to construct an approximate model of peak force (Fmax), specific energy absorption (SEA), and platform force (Fplt). The main effects analysis illustrated that the tri_z had the most significant effects on the peak force, specific energy absorption and platform force. To minimize Fmax and maximize SEA, the global response surface method (GRSM) was employed for parameter optimization. Finally, the optimized configurations were obtained with int_pre=0.067mm, T=10.003mm, tri_x=21.485mm, and tri_z=6.101mm. Compared to the initial design, the SEA value was increased by 16.41 %, while the Fmax value was decreased by 2.21%. The error of platform force derived from the optimal solution and theoretical prediction was 3.62%, which verified that the theoretical prediction model was credible within an acceptable range.

Analysis of Rock Breaking Parameters and Simulation of Mechanical Characteristics of Multi-Nozzle Jet Impact

With the continuous development of high-pressure water jet technology, research on the optimization of structural parameters for multi-nozzle configurations, the perforation effect of jet rotational impact rock breaking, and the impact force during rock breaking has received increasing attention. Through the development of a self-designed high-pressure water jet rotational drilling test device, rock breaking experiments were conducted on sandstone of different strengths using jet streams with different inclination angles, various combinations of nozzles, different target distances, and different rotational speeds. The parameters and structure of the multi-nozzle jet drill bit were optimized, and the impact of water jet-rock breaking effects was studied. The rationality of different inclination-angle jet streams in rock breaking was verified using the ALE-FEM coupling method. The changes in the force on the target body and the fragmentation mode during rock breaking with different inclination-angle jet streams were analyzed. The results showed that under the condition of adjustable inclination angles, a smaller inclination angle resulted in greater depth and a smaller diameter of rock breaking, while a larger inclination angle resulted in greater width and a smaller depth of rock breaking. The optimal combination of multi-nozzle jet streams was determined to be 20°, 30°, and 60°, which achieved a balance between rock breaking and borehole expansion performance. The efficiency of multi-nozzle jet rotational rock breaking decreased with increasing target distance, with the optimal range being 2 to 4 mm. The rotational speed of the multi-nozzle jet stream had a significant impact on rock-breaking efficiency. Under the same target distance conditions, as the drilling speed increased, the volume of rock breaking initially increased and then decreased, and the rate of volume attenuation increased with increasing target distance. The forms of rock breaking in multi-nozzle jet streams were not identical. Jet streams with smaller inclination angles mainly caused tensile failure through axial impact, while those with larger inclination angles primarily caused shear failure through radial impact. This study provides valuable guidance for optimizing the structural parameters of multi-nozzle jet drill bits and researching rotational rock breaking.

Intelligent prediction of lower extremity loadings during badminton lunge footwork in a lab-simulated court.

Introduction: Playing badminton has been reported with extensive health benefits, while main injuries were documented in the lower extremity. This study was aimed to investigate and predict the knee- and ankle-joint loadings of athletes who play badminton, with "gold standard" facilities. The axial impact acceleration from wearables would be used to predict joint moments and contact forces during sub-maximal and maximal lunge footwork. Methods: A total of 25 badminton athletes participated in this study, following a previously established protocol of motion capture and musculoskeletal modelling techniques with the integration of a wearable inertial magnetic unit (IMU). We developed a principal component analysis (PCA) statistical model to extract features in the loading parameters and a multivariate partial least square regression (PLSR) machine learning model to correlate easily collected variables, such as the stance time, approaching velocity, and peak accelerations, with knee and ankle loading parameters (moments and contact forces). Results: The key variances of joint loadings were observed from statistical principal component analysis modelling. The promising accuracy of the partial least square regression model using input parameters was observed with a prediction accuracy of 94.52%, while further sensitivity analysis found a single variable from the ankle inertial magnetic unit that could predict an acceptable range (93%) of patterns and magnitudes of the knee and ankle loadings. Conclusion: The attachment of this single inertial magnetic unit sensor could be used to record and predict loading accumulation and distribution, and placement would exhibit less influence on the motions of the lower extremity. The intelligent prediction of loading patterns and accumulation could be integrated to design training and competition schemes in badminton or other court sports in a scientific manner, thus preventing fatigue, reducing loading-accumulation-related injury, and maximizing athletic performance.

Analysis of energy absorption characteristics of a sinusoidal corrugated filled tube

In this paper, a sinusoidal corrugated filled tube (SCFT) is proposed by filling aluminum foam into a sinusoidal corrugated tube, the finite element model is established using the finite element software Pro/Engineer and Abaqus/Explicit, and the accuracy of the finite element model is verified. Crashworthiness studies under axial impact show that SCFT has better energy absorption (EA) performance than a circular filled tube (CFT) under the same outer tube wall thickness conditions, and the EA and specific EA of SCFT are 1.16 times and 1.12 times that of CFT, respectively; in addition, SCFT has a better interaction effect than CFT under the same outer tube wall thickness. Subsequently, a parametric study of SCFT by amplitude, wavenumber, outer tube wall thickness and aluminum foam density was systematically carried out. The structure studied in this paper can provide a reference for the innovative structural design of filled tubes.

Failure characteristics and conditions of rock-coal combination structure with weak layer under dynamic and static stresses

To comprehensively understand the mechanical response of a rock-coal combination structure containing a weak layer, a series of laboratory static loading and impact loading experiments were conducted. The results showed that under static load, the sliding process of the rock coal structure was relatively slow, and fragments can be observed. Under the action of horizontal impact loading, the whole coal stratum slipped out rapidly, and the process lasted only 0.05 s. Under the horizontal and axial impact loads, the coal stratum remained stable first, and then it slipped out as a whole under the action of static load. Additionally, a sliding instability criterion of a rock coal structure containing a weak layer was established based on theoretical analysis. The key parameter P value was checked through a numerical simulation experiment. It was found that the value was linearly related to the mechanical properties of the weak layer and overburden stress, and the experimental results coincided with the theoretical results. Finally, the relationship between sliding rockburst and strain rockburst was discussed, and these results can provide an important scientific basis for the prevention and control of dynamic disasters in deep mining.

Mere tension output from spring-linkage-based mechanical metamaterials.

Metamaterials whose properties are inaccessible with conventional materials offer powerful tools for unprecedentedly manipulating physical signals. However, an effective design strategy of metamaterials still remains a challenge for changing the compression or tension characters of stress waves during forward propagation. Here, we introduce a class of spring-linkage-based metamaterials exhibiting mere tension output at the distal end, no matter that the input is an axial impact, a sudden tension, or even alternating tension-compression. The metamaterials can turn compressive waves into pure tension and filter them out from the tension-compression mixed ones while allowing tensile signal stably propagating in soliton form. This is achieved by combining nonuniform and nonlinear properties of the proposed cells. In particular, these extraordinary functions of the metamaterial can be turned on or off and adjusted by tuning a key switch cell; thus, it is anticipated to serve as a start for more complex manipulation and utilization of mechanical signals.

Low-velocity impact of square conical gradient aluminium foam-filled automobile energy-absorbing boxes

In this paper, the low-velocity impact and lightweight design of the square conical gradient aluminium foam-filled automobile energy-absorbing boxes (EABes) is numerically studied. Firstly, the validity of the finite element calculation model is verified by comparing with the experimental results. Then, the influences of the conical bottom angle, tube-wall thickness, the number, position, height and depth of induction grooves, and the parameters of gradient foam on the energy absorption properties of the EABes under axial low-velocity impact are studied. After that, the mitigation and energy absorption of square conical gradient aluminium foam-filled automobile EAB are optimised. The results indicate that the aluminium tube-wall thickness has no obvious effect on improving the energy absorption properties of the EAB, and other factors have good effects on improving the energy absorption properties of the EAB. Compared with the constant cross-section EAB before optimisation, the peak impact force (F max) of the finally optimised square conical gradient aluminium foam-filled automobile EAB reduces by 22.4%, and the specific energy absorption (SEA) increases by 59.8%. The investigation is helpful for the design of the square conical gradient aluminium foam-filled automobile EAB.

Dependence of the coefficient of restitution on the shape of an impacting body

The effect of the shape possessed by an impacting body on the coefficient of restitution is addressed using the case of low velocity axial impact of axisymmetric bars. We consider bars of a fixed mass but varying shapes that are parameterized by certain non-dimensional parameters. The eigenvalue problems in all such cases are solved analytically, and the obtained eigenfunctions are used to address the problem of impact with a rigid wall. This transient response problem is solved exactly using the method of Laplace transform. The analytical solutions are compared with fully numerical solutions obtained from the impact of three-dimensional axisymmetric bars using the Finite Element Method (FEM), and a very good match is obtained in all cases considered. In each case, the deformation and restitution times are determined for calculating the coefficient of restitution (COR) using Poisson’s definition, which is compared with Newton’s definition of COR. It is observed for variable cross-section bars that the end of deformation phase is not marked by the bar being completely at rest with the energy purely as internal strain energy, as is conventionally thought of. The redistribution of the initial kinetic energy of the bar after impact in the form of gross motion of the bar and its internal motion is studied. It is found that the longitudinal cross-section variation of the bar decides its rebound characteristic, which is observed by the velocity of gross motion of the bar post impact.

Machine learning/finite element analysis - A collaborative approach for predicting the axial impact response of adhesively bonded joints with unique sandwich composite adherends

Despite the increasing usage of adhesively bonded joints (ABJs) in various industries, optimization of their bond strength in a cost-effective manner remains a challenging task, particularly when complex loading scenarios such as static and dynamic compressive loadings are considered. The task becomes even more challenging in bonded joints with sandwich composite adherends. This study focuses on the performances of double-strap ABJs configured by unique sandwich composite adherends, carbon fiber-reinforced plastic straps, and a room-cured structural epoxy resin under axial impact loading. A Finite Element-Cohesive Zone (FE-CZ) model is developed to simulate the response of the joints, and its integrity is validated against the experimental tests at three impact energy levels. The model is used to simulate the response of various ABJ configurations under axial impact loading, taking into account 13 material, geometrical, and testing-related parameters that influence joint strength, thereby generating 410 data sets. Subsequently, three Machine Learning (ML) models, including deep neural networks and genetic evolution (i.e., genetic programming and genetic algorithms) are developed and trained by the data sets to predict the ABJs load-bearing capacity. The ML models explore the relationship between the design parameters and the joint's ultimate load-bearing capacities, leading to the development of cost-effective and accurate empirical equations, and optimized joint configurations.

Investigating axial ligand impact on pinch-porphyrin peroxidase activity with [bis(o-methylpyridino) (dimethylesterprotoporphyrinato)Fe(III)] chloride

The synthesis and characterization of a novel hexacoordinated compound as a product of the reaction between chlorodimethylesterprotoprphyrin–Fe(III) 1 and 2–methylpiridine (2–CH3Py) was performed. The [bis(o–methylpyridino)(dimethylesterprotoporphyrinato)Fe(III)] chloride 2 is a compound of the family of the pinch–porphyrins, a model of peroxidase enzymes. We analyzed 2 using UV-Vis, 1H NMR, and EPR spectroscopies, as well as kinetic quantifications of its peroxidase activity and computational analysis, to evaluate the presence of the pinch-ligand coordinated to 1 in a series of pinch-ironprotoporphyrin complexes, as previously reported. Our investigation revealed that the oxidant activity of Compound I derived from peroxidase activity determination of 1 and 2, respectively, is better controlled when a heterohydrocarbonated chain is attached to the pyridyl groups that coordinate axially to 1; an effect evidenced by a decrease of the activation energy value associated with Compound 0 formation during the reaction performed by pinch–porphyrin, with the picdien axial ligand and hydrogen peroxide. When correlating the contribution of [Formula: see text]3/2 in the quantum mixed-spin state (qms), [Formula: see text]3/2, [Formula: see text]5/2, of iron(III)-based complexes with their peroxidase activity, we found that when the qms [Formula: see text]3/2, [Formula: see text]5/2, of iron(III) had 80% character [Formula: see text]3/2, the peroxide activity increased significantly. This could be a fundamental trait that could affect the peroxidase activity owing to the distortion of the iron geometry associated with its coordination number when o−methylpyridine is used as an axial ligand.

A Numerical Study of Complex Impact Loads on Thin-Walled Casing of Aeroengine Considering Turbine Guide Vane Structure1

As the main load-bearing component of the aero-engine system, the thin-walled casings have the characteristics of large size, complex structure, thin wall, and large area. In addition to the harsh working environment, it is necessary to study applicable preventive measures to contain high-energy fragments to ensure flight safety. The complex load formed by the axial impact and circumferential torsion exerted by the turbine rotor on the exhaust casing is studied, and the model includes the turbine rotor. By analyzing the deformation and energy dissipation of the exhaust casing in the calculation results, the dynamic response of the power turbine and the exhaust casing in the complex impact load is obtained, and it is verified that the initial speed of the power turbine has no obvious relationship with the dynamic response and energy dissipation of the exhaust casing. At the same time, it is concluded that the axial velocity and aerodynamic force of the power turbine have a strong positive correlation with the complex impact load and dynamic response of the exhaust casing. In the follow-up studies and equivalent experiments, these conclusions can be used as a reference for further experimental design.

Crashworthiness design of bionic-shell thin-walled tube under axial impact

Crashworthiness design of bionic-shell thin-walled tube under axial impact

Optimization of crashworthiness of CFRP thin-walled beams filled with aluminium honeycomb based on surrogate model

The CFRP thin-walled beam filled with aluminum honeycomb is a new design form in the crashworthiness design of automobile energy-absorbing component. It not only meets the requirements of strength, rigidity and lightweight under the normal load, but also ensures absorption of crash energy in a stable failure mode when a crash occurs. In this paper, under two typical conditions of axial impact and lateral impact, structural sample points are established by orthogonal experiment; a highly feasible surrogate model is constructed based on the radial basis function; the initial load peak Fmax and specific energy absorption (SEA) are taken as the main criteria to evaluate the energy absorption performance of the structure; the multi-objective genetic optimization algorithm NSGA-II is used to optimize the energy absorption design of CFRP thin-wall beams filled with aluminum honeycomb. The structure and material parameters of the minibus frame are optimized according to the crash condition to improve the energy absorption performance of the minibus in frontal and side crashes, and on this basis, an effective method to improve the crashworthiness of minibuses is explored.

Investigation of the effect of friction force on the energy absorption characteristics of thin-walled structures loaded with axial impact force

In recent years, there has been a significant increase in studies aimed at enhancing the energy absorption capabilities of thin-walled structures used in vehicles. These studies aim to mitigate the adverse effects of shock waves released during crashes by incorporating recesses that trigger folding on the walls of crash boxes, thereby increasing energy absorption. This particular study investigates the energy absorption and crushing behaviors of interpenetrating thin-walled structures under axial crushing conditions. Two different configurations were modeled to determine the contribution of friction force in dampening impacts in thin-walled structures. One configuration exhibited classical folding, while the other initiated folding after interpenetration upon the application of an axial impact load. The interpenetrating structures generate friction forces through recesses and protrusions on the surface of the crash box to provide energy absorption. The simulations were conducted using the finite element method (FEM) in a non-linear explicit dynamic collision scenario. The crash scenarios for both configurations were analyzed under identical conditions using two different materials (DP-600 and DP-800) and three different thicknesses (1.2 mm, 1.4 mm, and 1.5 mm). The dynamic crash simulations were compared based on Specific Energy Absorption (SEA), Total Energy (ET), Peak Crush Force (PK), Crush Force Efficiency (CE), and Mean Crushing Force (FM) values to examine the effects of friction force on energy absorption capabilities and crushing behaviors of the crash boxes. The analysis results demonstrated that friction force and energy absorption play a positive role in the crashworthiness characteristics of thin-walled structures.

X-ray microtomography analysis of the damage mechanisms in 3D circular braided carbon fiber/epoxy resin composite tubes under axial impact compression

The dynamic behavior of three-dimensional (3D) circular braided composite tubes with different braided parameters was experimentally investigated subjected to axial impact compression using a Split Hopkinson Pressure Bar (SHPB). The damage characterization of the post-impacted tubes was examined using scanning electron microscope (SEM) and X-ray micro-computed tomography (micro-CT). The influence of braided parameters and strain rate, including braided angle, the number of braided layer and axial yarn, on the dynamic mechanical properties, progressive crush characteristics and failure mechanism of 3D braided composite tubes was analyzed in detail. It was found that the smaller braided angle and the larger numbers of braided layers contributed to better axial dynamic properties. The compressive strength, stiffness and specific energy absorption (SEA) of 3D five direction (3D5D) tubes with axial yarn were larger than those of 3D four direction (3D4D) tubes without axial yarn. Meanwhile, the dynamic mechanical response and damage patterns of braided tubes exhibited significant strain rate effects. The impact compression failure mechanisms of braided tubes were mainly fiber tows crushing, fiber breakage, fiber buckling, shear fracture, resin cracking, interfacial cracks, fiber-matrix debonding, etc.

Experimental and numerical study on crashworthiness of bionic hedgehog spine thin-walled structures

Natural impact-resistant biomaterials, with ingenious and exquisite geometric configurations, have resistance to external impact, and thus provide a perfect bionic example for the optimization design and crashworthiness improvement of new thin-walled structures. Based on the configuration characteristics of hedgehog spine, this paper designed the bulkheaded hedgehog spine thin-walled structure and studied the dynamic behavior of thin-walled structures under axial and oblique impact compression by combining 3D metal printing, quasi-static compression test and finite element simulation. The results show that the combined effect of the ribs, inner walls and bulkheads of the bulkheaded hedgehog spine thin-walled structure effectively improves its deformation coordination ability and crashworthiness. The specific energy absorption of the bulkheaded hedgehog spine thin-walled structure under axial or oblique impact is about 4.1, 2.1 and 1.4 times that of the single-wall cylinder, spider web and simplified hedgehog spine thin-walled structures, respectively.

Eccentric Rotor Drop Dynamics Study of Vertical Maglev Bearing System

When considering the problem of a vertical magnetic levitation bearing system, the rotor eccentric fall is more likely to cause the failure of the protective bearing. In this paper, a rotor drop collision model and a protective bearing dynamics model are constructed. It compares and analyzes the evolution of collision force values of the rotor eccentric drop as well as the non-eccentric drop. Further, this paper discusses the law of influence of three factors, rotor quality, rotational speed, and axial protection clearance, on the collision characteristics of the protected bearing in eccentric and non-eccentric cases. It has also experimentally verified this characteristic of rotor speed. The results show that compared with the non-eccentric condition, the axial impact force and radial impact forces of the rotor in the eccentric condition increase by 14% and 114%, respectively. Compared with the non-eccentric condition, with the increase in rotor quality, the axial and radial impact force increase by 68% on average, and the axial depth amplitude of the rotor increases by 350%. With the increase of rotor speed, the axial impact force without an eccentric drop is basically unchanged; the axial impact force of an eccentric drop increases slightly, and the radial impact force increases by 110%. With the increase of axial protection clearance, the radial displacement vibration of the rotor axis increases; the average increase of the maximum axial force is 120 N, and the average increase of the maximum radial force is 100%.