Impact Dynamic Model Research Articles

Well-planned greenery improves air urban quality - Modelling the effect of altered airflow and pollutant deposition

Urban air quality is influenced by vegetation through alterations in airflow and pollutant deposition processes. We investigated these interactions by integrating the Vegetation Impact Dynamic Assessment model (VIDA) with the Large-Eddy Simulation model PALM. Our analysis focus on nitrogen dioxide (NO₂) and particulate matter (PM) concentrations at the local scale, considering three tree genera. Our findings reveal the necessity of accounting for both gaseous pollutants and particles separately due to their differing mechanisms of deposition onto leaves. The coupled PALM-VIDA model demonstrates a significant reduction in PM levels across the modelling domain and within street canyons when deposition to vegetation is incorporated. Reduction in NO₂ through deposition to vegetation is lower but human NO2 exposure can still be decreased if tree species selection and placement leads to desirable effects on air flow. Sparse tree arrangements or species with sparse crowns facilitate ventilation and are often better at reducing NO₂ concentrations in street canyons compared to denser vegetation with higher deposition but negative effects on ventilation. Our study informs urban planning and green infrastructure design, underscoring the multifaceted role of urban greenery in air pollution mitigation strategies. Its main conclusion is that both deposition processes and the influence of air mixing and ventilation need to be considered to accurately assess the effects of urban trees on local air quality. Ill-considered placement and species selection may cause a net increase in pollutants underneath the trees. However, careful planning can address this risk and instead improve overall air quality.

Analysing the damping performance of automobile crash dummy ribs

Chest injuries are commonly encountered in traffic accidents, with ribs playing a crucial role in chest impact response. This study focuses on the damping performance of ribs and its influence on chest response during collisions. Employing mechanical bionics principles, the mechanical equivalence of ribs under collision impact was determined. Consequently, a rib impact dynamic model based on equivalent damping theory was developed. This model was integrated with a rib drop hammer impact test system, yielding a numerical solution for the equivalent damping ratio of the rib, quantified as 0.085. Additionally, to validate the accuracy of the rib impact dynamics model, a verification method based on the half-power bandwidth method was proposed. Through the implementation of the rib force hammer impact test, the equivalent damping ratio was determined to be 0.093, showing an 8.6% deviation from the result of the impact dynamics model. These findings not only confirm the validity of the rib equivalent damping theory within the impact dynamics model but also provide theoretical support for the design and improvement of dummy ribs and, potentially, the overall development of crash test dummies.

Impact toughness and dynamic constitutive model of geopolymer concrete after water saturation

The dynamic compression test of geopolymer concrete (GC) before and after water saturation was carried out by the split Hopkinson pressure bar (SHPB). And the effects of water saturation and strain rate on impact toughness of GC were studied. Based on Weibull statistical damage distribution theory, the dynamic constitutive model of GC after water saturation was constructed. The results show that the dynamic peak strain and specific energy absorption of GC have strain rate strengthening effect before or after water saturation. The impact toughness of GC decreases after water saturation. The size distribution of GC fragments has fractal characteristics, and the fractal dimension of GC fragments after water saturation is smaller than that before water saturation. The dynamic constitutive model based on Weibull statistical damage distribution theory can accurately describe the impact mechanical behavior of GC after water saturation, and the model fitting curves are in good agreement with the experimental stress–strain curves.

Research on the solid particle erosion wear of pipe steel for hydraulic fracturing based on experiments and numerical simulations

Erosion wear is a common failure mode in the oil and gas industry. In the hydraulic fracturing, the fracturing pipes are not only in high-pressure working environment, but also suffer from the impact of the high-speed solid particles in the fracturing fluid. Beneath such complex conditions, the vulnerable components of the pipe system are prone to perforation or even burst accidents, which has become one of the most serious risks at the fracturing site. Unfortunately, it is not yet fully understood the erosion mechanism of pipe steel for hydraulic fracturing. Therefore, this article provides a detailed analysis of the erosion behavior of fracturing pipes under complex working conditions based on experiments and numerical simulations. Firstly, we conducted erosion experiments on AISI 4135 steel for fracturing pipes to investigate the erosion characteristics of the material. The effects of impact angle, flow velocity and applied stress on erosion wear were comprehensively considered. Then a particle impact dynamic model of erosion wear was developed based on the experimental parameters, and the evolution process of particle erosion under different impact angles, impact velocities and applied stress was analyzed. By combining the erosion characteristics, the micro-structure of the eroded area, and the micro-mechanics of erosion damage, the erosion mechanism of pipe steel under fracturing conditions was studied in detail for the first time. Under high-pressure operating conditions, it was demonstrated through experiments and numerical simulations that the size of the micro-defects in the eroded area increased as the applied stress increased, resulting in more severe erosion wear of fracturing pipes.

Air pollution removal with urban greenery – Introducing the Vegetation Impact Dynamic Assessment model (VIDA)

Urban greenery is identified as a potential tool in air pollution mitigation. However, the impact is still debated. This paper introduces the innovative VIDA (Vegetation Impact Dynamic Assessment) model, specifically designed to quantify air pollution removal through deposition on vegetation. The VIDA model offers an advanced representation of vegetation that could be integrated into urban air quality dispersion models in the future. Furthermore, the model serves as a valuable tool for exploring the intricate interactions among deposition, resuspension, and wash-off processes, as well as understanding how meteorological conditions and various leaf traits influence these processes.The current version of the model focuses on particulate matter (PM) and encompasses a range of processes, including deposition on vegetation surfaces, encapsulation within the waxy cuticle, wind-driven resuspension, and wash-off. Additionally, the model takes into consideration dynamic changes in PM concentrations on the leaf surface over time, incorporating factors such as PM size fractions, meteorological conditions, and leaf characteristics. This comprehensive approach allows for the evaluation of various species or species groups based on their distinct traits. The VIDA model effectively reproduces measured data, yet continued evaluation remains crucial as new data emerges. Notably, challenges were encountered due to data scarcity and the absence of standardized methods for characterizing vegetation traits. Addressing these challenges and refining the representation of wash-off process will enhance the VIDA model's utility in predicting the dynamic relationship between vegetation and air quality.The introduction of VIDA provides a significant advancement in modelling air pollution removal by deposition to vegetation at a relevant local scale and enables inclusion of urban greenery as tool in urban planning for air pollution mitigation.

Damage mechanisms of spline teeth of friction plates under non-uniform impact

The fatigue fracture failure of friction plates seriously affects the safety of high-power density transmission systems due to the non-uniform impact with the inner hub. However, the crack initiation inducement and underlying damage mechanisms are still confused so far, which has critical significance for improving the service life. To address this problem, the matrix metallographic structure of friction plates was observed by Scanning Electron Microscope (SEM), which excludes internal defects within the organization. Then, an impact dynamic model was established to investigate the collision laws between spline teeth and the inner hub. The effect of the inner hub’s speed fluctuations on the impact force and acceleration was analyzed, and an analytical relationship between tooth root stress, impact force, and gear parameters was established. A large module simulation prototype test rig was designed based on the proposed equivalent model to verify the impact dynamic model. Results show that the majority of collisions between spline teeth and the inner hub are “catch-up collisions”, which well explains the non-uniform impact phenomenon. The “frontal collisions” will only occur when the speed of the inner hub is lower than that of the friction plate. The higher cumulative frequency of tensile stress on the pull side of spline teeth roots by “catch-up collisions” reveals the underlying mechanism for the differential extent of cracks’ damage. The minimum bending stress of the teeth root is 125.5 MPa at a pressure angle of 32°, which shows a linear increase with tooth clearance. The fatigue fracture of friction plates has been effectively suppressed after structural optimization.

Low-velocity impact response of the post-buckled FG-MEE plate resting on visco-Pasternak foundation: Magneto-electro-mechanical effects-based interaction analysis

Revealing the coupling of nonlinear behavior and the magneto-electro-mechanical effects in the impact responses of post-bucked magneto-electro-elastic structures contributes to the intelligent development of aircraft structural systems. The low-velocity impact responses of the post-buckled functional gradient magneto-electro-elastic(FG-MEE) plate resting on visco-Pasternak foundation are investigated. In the framework of the von Kármán-type nonlinear model considering post-buckling configurations, the low-velocity impact dynamics model of the post-buckled FG-MEE plate is constructed. The two-step perturbation method is developed to obtain the post-buckling equilibrium path induced by the magneto-electro-mechanical effects. Further, the higher-order form of the two-step perturbation method-Galerkin integral method is proposed for the post-buckled FG-MEE plate resting on visco-Pasternak foundation, acquiring the high-order truncated solutions of displacement, electric potential, and magnetic potential. Ultimately, the snap-through phenomenon of the post-buckled FG-MEE plate under low-velocity impact is captured, and the variation in the degree of coupling between nonlinear behavior and the magneto-electro-mechanical effects is systematically revealed.

Topology Transformation Analysis on Serial Flexible Variable Topology Mechanism

The flexible variable topology mechanism (FVTM) has become a research focus in the field of the mechanism because of its reconfigurable characteristics, which exhibit excellent adaptability in complicated working environments. In the process of topology transformation, the FVTM often generates impact, which leads to vibration and instability of the flexible elements. It seriously affects the accuracy and reliability of the operation. In view of this, this paper takes the serial-FVTM as an example to analyse its impact characteristics during topology transformation. The impact dynamics model is established by the theorem of impulse. Based on this, the fourth-order Runge-Kutta method is used to solve the dynamics differential equations. Using the control variable method, the influence of different parameters on the impact characteristics of the FVTM is obtained through numerical simulation analysis. Finally, the methods to improve the stability of the FVTM during topology transformation are analysed to expand new ideas for the subsequent research.

Impact Dynamic Analysis of Suspended Marine Cables

Objective: It is often impossible to avoid collisions between marine cables, the impact dynamic response of the collisions between marine cable needs to be obtained. Methods: In this paper, we derive the lumped mass method based on the bending moment and torque; using the lumped parameter method, the suspended cable is discretized into lumped mass models, and the impact force of the suspended cable is considered in the dynamic analysis; the impact dynamics model of the suspension cable is developed by referring to the specific parameters of the suspension cable and combining them with offshore construction processes. Results: There is a relationship between the impact force and the tension of the cable. The tension and impact force are related in cable collisions. While the maximum effective tension occurs at the upper end of the vertical cable and at the collision point, the horizontal cable's tension at the collision position is minimal. The distribution of curvature mutates at the collision point, causing bending deformation. The horizontal cable experiences greater bending change at the collision position than the vertical cable. Conclusion: In summary, collision of different parts of vertical cable is not obvious, while horizontal cable is more prone to self-collision and collision with vertical cable. Collision impact on horizontal cable is greater, with minimum tension occurring at collision point. Maximum velocity for horizontal cable appears at collision position, and for vertical cable at bottom. Maximum acceleration for both cables occurs at collision zone.

Impact dynamic characteristics and constitutive model of granite damaged by cyclic loading

To study the influence of damage degree on dynamic characteristics of damaged rock mass, the samples with different damage degrees were obtained by cyclic loading test and then the impact failure test was carried out by a 100-mm diameter split Hopkinson pressure bar (SHPB) device. In addition, the Zhu-Wang-Tang (ZWT) constitutive model was improved to establish the dynamic constitutive model of damaged granite. Results show that when the cyclic upper limit stress (CULS) reached 60% of the compressive strength of rock mass, the Felicity effect was significant and the Kaiser effect basically disappeared. Furthermore, there was obvious compressive strengthening effect of damaged rock mass under impact load, with the increase of the CULS in the early stage, the dynamic compressive strength of granite samples showed an overall decreasing trend. The damage degree had a significant effect on the propagation and energy absorption ability of rock mass, thus affecting its failure characteristics. Eventually, the proposed constitutive model was fitted with the experimental data, which showed that the model could accurately describe the dynamic mechanical properties of damaged granite under impact load.

Dynamic Response Difference of Hydraulic Support under Mechanical-Hydraulic Co-Simulation: Induced by Different Roof Rotation Position and Hysteresis Effect of Relief Valve

As key supporting equipment in coal mining, hydraulic supports are vulnerable to impact pressure from roof movement and deformation. In this paper, a mechanical-hydraulic co-simulation platform for hydraulic supports is established. Moreover, the rationality of the simulation platform is verified. Based on this platform, the rigid-flexible coupling impact dynamics model of hydraulic support is built. Finally, by delaying the opening time of the relief valve, the energy dissipation problem of the relief valve hysteresis effect on the hydraulic support system under the rotary impact is discussed. The results indicate that the rotary load acting on the hydraulic support decreases gradually with the backward movement of the roof rotary position, which causes the peak pressure in the column to decrease (by 69 MPa). The hinge point load of different parts shows different load transfer laws. The hysteresis effect of the relief valve prolongs the energy release time of the system, increasing the pressure in the column by 23 MPa. The instantaneous opening speed of the relief valve spool reaches 15.7 m/s, and the hinge point between the top beam and the column is most sensitive to the hysteresis effect (impact coefficient increases by 0.63).

Dynamic response of wind turbine blade surface material under water droplet high velocity impact

When a wind turbine blade exposure to some degree of rainfall, water droplets in the atmosphere impact the blade at high velocity will causes erosion damages of the leading edge. The damages have significant influence to the aerodynamic performance of the blade, and also the cost of power generation. In this paper, a high velocity impact dynamics model of water droplet impact on wind turbine blade is develops based on SPH-FEM coupling method, where SPH model is used to model the large deformation region of the fluid domain, and FEM method is used to model the small deformation region of the structure domain. Together with properties of gelcoat material on the blade surface, effects of varying impact velocities and angles on the impact response of the gelcoat material are analysed through numerical simulation. The results show that during a high velocity impact event of water droplet, the contact force history appears two peaks. Also contact forces and strains on the blade material decreases with decreasing droplet impact velocity and impact angle, the total contact duration of the droplet during the impact decreases with increasing droplet impact velocity and angle. The present study is expected to provide theoretical guidance for enhancing the erosive capacity of wind turbine blade gelcoat material.

Research on Rock Damage Evolution Based on Fractal Theory-Improved Dynamic Tensile-Compression Damage Model

According to the characteristics that the dynamic tension of rock material is elastic brittle and the dynamic compression is elastic plastic, based on previous studies, the influence of initial damage is considered in the established compression damage model, and the calculation formula of the damage threshold used to evaluate whether the surrounding rock is affected by blasting is given. According to the classic rock impact dynamic damage model and statistical damage mechanics theory, a rock compressive and tensile statistical damage constitutive model and impact damage model under blasting load is proposed. Based on the proposed damage model and the classic dynamic tensile damage model, the numerical simulation of blasting damage was carried out, and the numerical calculation results were compared with the field measurement results. Based on the established damage model, to further clarify the damage evolution characteristics of rock under blasting load, fractal dimension theory was introduced to analyze the rock damage under blasting loads with different blasting hole network parameters. The results show that compared with the axial direction of the blast hole, the direction of blast hole diameter is the main direction of blasting fracture extension. Tensile fracture mainly occurs along the hole diameter direction, and compression fracture mainly occurs below the hole bottom. Compared with the numerical calculation results based on the classical dynamic tensile damage model, the blasting fracture range obtained according to the damage model, especially the fracture depth below the bottom of the hole, was not much different from the measured value and was closest to the measured value. The crack density of 1 us, 90 aperture, and 130 aperture was larger than that of the other working conditions. Among them, the crack density of 130 aperture was the largest, followed by 90 aperture. At 2~3 us after initiation, cracks between two blast holes, radial cracks and circumferential cracks around two blast holes, and obvious cracks were formed around blastholes; at 4~5 us after initiation, the shock wave front decreased rapidly and propagated outward in the form of the compression wave. The crack propagation velocity was much smaller than that at 1~3 us after initiation. In summary, the proposed damage model is reasonable and has certain engineering practicability.

On Inverse Inertia Matrix and Contact-Force Model for Robotic Manipulators at Normal Impacts

State-of-the-art impact dynamics models either apply for free-flying objects or do not account that a robotic manipulator is commonly high-stiffness controlled. Thus, we lack tailor-made models for manipulators mounted on a fixed base. Focusing on orthogonal point-to-surface impacts (no tangential velocities), we revisit two main elements of an impact dynamics model: the contact-force model and the inverse inertia matrix. We collect contact-force measurements by impacting a 7 DOF Panda robot against a sensorized rigid environment with various joint configurations and velocities. Evaluating the measurements from 150 trials, the best model-to-data matching suggests a viscoelastic contact-force model and computing the inverse inertia matrix assuming the robot is a composite-rigid body.

Dynamic Modeling and Analysis of Impact in Space Operation Tasks

For the rigid impact and flexible impact in space operation tasks, impact dynamic models between two objects are established in this paper, laying the model foundation for controlling or suppressing the impact. For the capture task between a grapple shaft and a rigid body, the impact dynamic model is established based on the Zhiying–Qishao model. Moreover, by introducing a friction factor into the original impact model, an improved dynamic model between two rigid bodies is proposed. For the capture task with flexible impact, an impact dynamic model between the grapple shaft and a flexible wire rope is established based on the dynamic model of the flexible wire rope. The ground experiments and simulations are carried out with two objects on an air flow table. The experiment results validate the impact dynamic model proposed in this paper.

Failure mechanism and predictive model of lithium-ion batteries under extremely high transient impact

With the advantage of high energy density, lithium batteries are widely used in industrial and military applications. However, under the complex conditions of vehicle collision and high-speed flight ammunition, lithium-ion batteries have functional failure, which seriously affects the safety and stability of systems using batteries. In this paper, research on the electric parameter drift of lithium-ion batteries under high impact is carried out through a machete test system, and the experimental phenomena are analyzed theoretically. Based on this, an equivalent circuit model is established to analyze the failure phenomenon and mechanism of lithium-ion batteries under more extreme impact scenarios, which are difficult to test in the laboratory. Finally, the mechanical impact dynamic (MID) model of lithium-ion batteries at the moment of high impact is established, and the influence of separator thickness, elastic modulus and other parameters on the impact resistance of lithium-ion batteries is revealed, which provides a reference for the optimization design of lithium-ion batteries under a high-impact environment.

Novel calculation method for dynamic excitation of modified double-helical gear transmission

This paper presents a novel calculation method for dynamic excitation of the 3-D modified double-helical gear pair in consideration of actual contact state. The 3-D modification method combines tip, root, and axial modification. Firstly, the tooth surface equation of double-helical gear with 3-D modification is derived and the calculation method for time-varying mesh stiffness (TVMS) of the modified double-helical gear pair is proposed and the effects of modification parameters on TVMS are studied. Secondly, the tooth surface load distribution is analyzed on the basis of TVMS for the double-helical gear pair. Accounting the influence of modification parameters on tooth surface friction coefficient, the time-varying friction excitation (TVFE) of the modified double-helical gear pair is researched. Besides, combining approach mesh stiffness of the modified double-helical gear pair and impact dynamic model, the calculation formula of meshing impact force (MIF) is proposed, and the effects of helix angle and modification parameters on MIF are discussed. The calculation methods of TVMS, TVFE and MIF proposed in this paper will be useful for accurate prediction about vibration and noise of the double-helical gear system.

Movement characteristics analysis of bi-directional friction linear micro-motor driven by a set of micro-actuator

In this paper, a bi-directional friction linear micro-motor (BFLM) driven by a set of micro-actuators was introduced and analyzed. The BFLM was fabricated using PolyMUMPs process. The impact dynamics model for the BFLM was established, and its motion equation was also derived that takes into account the friction and contact. The relative motion between the driving head and the slider, as well as forward or backward movement of the slider were analyzed in detail. The forward and backward movement displacement of the slider was measured, and the experimental results were in good agreement with theoretical predictions. The theoretical results show that the motion direction of the slider can be changed by controllable driving frequency to the BFLM. It was feasible to use a set of actuators to drive the slider in bi-directional motion.

Hysteresis modeling of impact dynamics using artificial neural network

Abstract In this paper, the process of training an artificial neural network (ANN) on predicting the hysteresis of a viscoelastic ball and ash wood bat colliding system is discussed. To study how the material properties and the impact speed affect the hysteresis phenomenon, many experiments were conducted for colliding three types of viscoelastic balls known as sliotars at two different speeds. The aim of the study is to innovate a neural network model to predict the hysteresis phenomenon of the collision of viscoelastic materials. The model accurately captured the input data and was able to produce data sets out of the input ranges. The results show that the ANN model predicted the impact hysteresis accurately with <1% error.

A 3D impact dynamic model for perforated tubing string in curved wells

Perforating-test joint operation in oil&gas wells may causes strong impact vibration of downhole tools which can easily lead to buckling of tubing string, falling off of tools and damage of instruments. A 3D impact dynamic model of the perforated tubing string is established by using d'Alembert's principle and microelement method, and solved by the Newton difference method, taking into account the well trajectory, internal/external fluid pressure, interaction forces between the tubing and casing, and the coupling effect of perforating gun-shock absorber-tubing string. Due to the complexity of the verification, firstly, a similar experiment is carried out to test the accuracy of the model preliminarily. Secondly, through a case analysis, the feasibility of the model in the perforation impact dynamic analysis of tubing string in curved wells is further investigated. Both the two tests show that the model proposed in this paper has good calculation accuracy and can meet the needs of perforation shock vibration analysis of tubing string in curved wells perforation.