Dynamic Response Behavior Research Articles

Dynamics characteristics of variable stiffness curvilinear fiber-reinforced layered composite beam under moving load by sinusoidal shear flexible beam model including nonlinear and thermal effects

In this study, the dynamic response behavior of curvilinear fibers based layered-composite beam under transversely moving load is investigated considering linear and nonlinear analyses. The formulation is developed applying sinusoidal shear flexible beam theory, geometrical nonlinearity based on von Kármán’s assumption, and the constitutive equation fulfilling the plane stress situation through the width of arbitrarily lay-up composite beam. The load on the beam is treated as moving with uniform velocity, acceleration and also oscillatory motion with time. The governing nonlinear dynamic equations are framed employing Hamilton’s principle and by adopting finite element approach. The response of beam in time domain is obtained solving the governing equations through direct time integration method by Newmark integration scheme. and the results are viewed through the frequency-amplitude relationship. A detailed parametric study involving curvilinear fiber path angles, lay-up ply angles, thickness ratio, moving load velocity, and acceleration, and forcing frequency is made on the dynamic behavior of variable stiffness beam with curvilinear fiber beam. The effect of thermal environment and boundary conditions on the vibrational response behavior of beam is also predicted.

Dynamic damage law and failure modes of layered coal-rock mass under impact loading

Abstract Up to now, most of the structural dynamic analysis is based on the Lagrange system, while the Hamilton system is composed of the phase space composed of the generalized displacement and stress, showing a wonderful symmetry, which opens up a new way for the theoretical research and calculation of dynamics. The physical model of the layered combined coal-rock is constructed by dividing the ‘outburst center’ coal in front of the heading face into the combined layered structure. Based on Hamilton mechanics, the Hamilton canonical equation under symplectic geometry structure is established, combined with Hamilton variational principle and symplectic time subdomain method, the multi-layer symplectic element control equation of coal-rock is established, and the dynamic displacement and stress transfer characteristics at any time can be solved by iterative calculation. The action modes of axial torsional stress, radial principal stress and shear stress of layered coal- rock under impact loading are determined, and the weak layer and interlayer stress transfer dynamic response behavior of layered coal- rock under complex stress conditions are determined. The conclusions are as follows: ①Under static loading, the layered shear stress circle provides the initial condition of damage failure, impact loading acts as an exciting force to trigger the torsion effect, forming the ‘ X ’ -shaped shear line in the radial and axial directions of the interlayer interface, and the boundary produces the ‘ V ’ -shaped dynamic spalling surface. ②The short axis is damaged before the long axis, and the central node is the starting point of instability. The main cracks are formed along the long and short axis respectively, and finally the ‘ O-+ ’ failure mode is formed, which verifies the prominent axial and radial spallation phenomenon. This method avoids the non-conservation of system energy caused by energy dissipation, and will become an effective method to study the dynamic mechanical properties and damage evolution path of coal-rock. It has guiding and reference significance for the theoretical research and prevention technology of coal and rock dynamic disasters.

Dynamic mechanical response and failure behaviour of single-flawed rocks under combined compression-shear loading

Dynamic mechanical response and failure behaviour of single-flawed rocks under combined compression-shear loading

Research on dynamic response behavior of the fuze with a combined fuze-warhead structure under different impact positions of bullets

Abstract Aiming at the problem of unclear fuse detonation response in the process of different positions of the bullet impact detonator, to carry out research on the dynamic response behaviour of the fuse under the difference of the bullet impact position of the fuze-warhead combination structure. Through experiments and LS-DYNA numerical simulation, the influence of different positions of bullet impact booster on fuze reaction level and output pressure is analyzed. The results demonstrate that in the tests where the bullet made contact with the centre of the fuse, transmitting an explosive charge, the velocity of the bullet is 832 m/s, and the fuse exhibits a partial detonation level in response to the impact. The highest fuse response level occurs when the bullet strikes the centre of the pyrotechnic charge - partial detonation, the lowest fuse response level occurs when the bullet strikes the upper side of the pyrotechnic charge - burning, and the fuse response level occurs when the bullet strikes the lower side of the pyrotechnic charge - deflagration or explosion. The maximum fuse output pressure when the bullet strikes the centre of the pyrotechnic charge - 6.09 GPa, the minimum fuse output pressure when the bullet strikes the upper side of the pyrotechnic charge - 0.98 GPa, and the fuse output pressure when the bullet strikes the lower side of the pyrotechnic charge is 2.76 GPa.

Evaluating the dynamic response and phase angle behavior of SBS-modified asphalt mixtures for enhanced pavement performance

Bitumen exhibits viscoelastic properties, showcasing both viscous and elastic behaviors, which are characterized by the phase angle and dynamic modulus. Issues like early fatigue fractures, rutting, and permanent deformations in bituminous asphalt pavements arise due to moisture susceptibility, high-temperature deformation, low-temperature cracking, and overloading. These distresses result in potholes, alligator cracks, and specific deformations that lead to early pavement failure, increasing rehabilitation and maintenance costs. To address these issues, this study examines the dynamic modulus and phase angle behavior of Styrene Butadiene Styrene (SBS) modified and unmodified asphalt mixtures. SBS was incorporated in various proportions, ranging from 2 to 7% by the weight of bitumen. The asphalt mixture performance tester (AMPT) was utilized to measure the dynamic modulus at temperatures of 4.4, 21.1, 37.8, and 54.4 °C, and frequencies of 0.1, 0.5, 1, 5, 10, and 25 Hz. The study found significant correlations between dynamic modulus, temperature, loading frequency, and SBS content. Additionally, Multi Expression Programming (MEPX) and regression modeling were employed to estimate the dynamic modulus of SBS-modified HMA. Results indicated that increasing SBS content up to 7% decreased penetration and ductility values by up to 46% and 56%, respectively, while raising the softening point by 63% due to increased stiffness. The blend with 6% SBS by weight of bitumen exhibited superior performance compared to other mixtures. Phase angle initially increased with rising temperature, peaking at 37.8 °C at lower frequencies, and continued to increase at higher frequencies. Isothermal and isochronal plots showed that the 0% SBS mix had a higher phase angle due to increased bitumen content. Overall, the HMA mix with 6% SBS provided the best outcomes.

A Validation Study on Dynamic Response and Failure Analysis of Large Unconfined Pipes under Localized Blast Loading Using an Explicit Dynamic Approach

Abstract This study utilized an Explicit Dynamic Approach to analyze the dynamic behavior of large-diameter pipes subjected to localized blast loading. The objective of the validation study was to investigate the effects of the explosion's blast force on the dynamic response and material behaviors in large-diameter pipes. The existing experimental data was benchmarked with the numerical results to assess the prediction accuracy. The crucial factors include the amount of the explosive mass (0.2-5.0 kg), the contact regions, and the wall thickness of the pipe (1.46 cm and 2.62 cm). As a result, the contact area significantly influenced the deformation range in each case, ranging from 50-400 cm2. The amount of explosive energy was crucial in determining the material response. For instance, deformations like pitting and spallation were found from the case testing with less than 1.4 kg of TNT, and the completed tearing in the central area was found from the case of higher explosive mass. With modest explosive mass, the pipe material underwent inelastic deformation. However, the material became vulnerable to adiabatic shearing failure when the explosive energy exceeded 1.4 kg in penetrating the 2.62 cm-thick walls. The difference between the simulations and experimental deformation (1.46-mm-thickness) was average at 8.5 %, which presents an attractive tool. Therefore, this Explicit Dynamic tool will be used in subsequent research to study the responses of structural building systems to occasional explosion scenarios and capture the explosion fragments.

Response analysis of a long-span cable-stayed bridge with ultra-high piles subjected to near-fault ground motions considering deep-water, sedimentation, local site, and wave-passage effect

The objective of this study is to examine the dynamic response behavior of a long-span cable-stayed bridge with ultra-high piles subjected to near-fault ground motions, comprehensively considering deep-water, sedimentation, local site, and wave-passage effects. Firstly, a 3D finite element (FE) model of the long-span cable-stayed bridge with ultra-high piles (Approximately 105 m) and a tower height of 216.4 m was established using Midas software. The deep-water, sedimentation, local site, and wave-passage effects were synthetically considered in this FE model. The FE model incorporates the sag effect of the stayed cable and the pile-soil interaction, enabling a detailed seismic analysis. Secondly, the examined near-fault ground motions with long-period velocity pulses were selected from the PEER database according to the design acceleration response spectrum with a fortification intensity of VIII degrees. Finally, nonlinear time history analyses of the selected long-span cable-stayed bridge, subjected to spatial near-fault ground motions including local site effect and wave-passage effect, were conducted, and the responses of critical design sections and points in structures were examined and evaluated. The results demonstrate that long-period velocity pulses can significantly affect the structural responses, while deep-water and sedimentation effects do not have a significant impact on the dynamic responses of long-span cable-stayed bridges. For the local site effect, the softer the soil at the support site and the greater the difference in soil conditions at the support, the larger the structural response. Regarding the wave effect, the structural response will increase or decrease depending on the magnitude of the wave speed and the span length between towers.

Thermo-electric coupling dynamic modeling and response behavior analysis of PEMEC based on heat current method

Complete analysis of the dynamic characteristics of the proton exchange membrane electrolytic cell (PEMEC) is significant for its efficient and flexible utilization. To fully reflect the dynamic process including thermo-electric interactions within PEMEC, this paper disassembles this process and simplifies it for representation through a clear diagram of dynamic power flow. On this basis, we proposed a novel combined qualitative and quantitative analytical method for the comprehensive response by defining the evaluating indexes for PEMEC's response performance. Meanwhile, we analyzed the change pattern of dynamic response behavior, response time and the influence of thermo-electric interaction under multi-scenarios, like different voltage abrupt change magnitudes, different cathode operating pressures, and different inlet water temperatures. The results show that the PEMEC has the biggest response behavior with the longest response time under the largest external voltage variation magnitude. Besides, there is the shortest response time and smallest parameters total changes after response when the cathode operating pressure is 15bar Moreover, when the inlet water temperature is 40 °C it has the characteristic of quick action time and small response magnitude. The model, analysis method, and findings in this paper provide an effective reference for the operational regulation of PEMEC's thermal and electrical parameters.

Study on the dynamic response behaviour of the head cover-bolts-stay ring of a variable-speed pump-turbine

Abstract The vibration characteristics of the hydro-turbine’s head cover is a significant factor that affects the safety of the unit. This paper established the Finite Element Method (FEM) model for the head cover-bolts-stay ring system of a variable-speed pump-turbine, and the dynamic response behaviour of the system under pretension and hydraulic excitation conditions is analyzed. The results indicate that the maximum value of stress locates at the bolt root, which is 715.6MPa under pretension load and 678.7MPa under hydraulic excitation. The results presented in this paper offer valuable guidance for the safety and stability of the variable-speed pump-turbine.

Mechanical modeling and parameter analysis of the docking process for probe-drogue docking mechanisms

The on-orbit probe-drogue berthing docking of two spacecraft can effectively reduce impact force and adjust for initial deviations. However, its dynamic response and influence behaviors of design parameters are extremely concerning but difficult to obtain because of its complicated structure. In this paper, a fast mechanical modeling (FMM) method is proposed to obtain the dynamic response of probe-drogue docking mechanisms during spacecraft berthing missions. Regarding the quasi-static docking process, complex dynamic docking behaviors are simplified and decoupled. The FMM method divides docking into three contact processes based on the scene of contact; it analyzes the deviation adaptive docking principle of this type of docking mechanism by establishing the kinematics and mechanics models of active and passive parts. The finite element simulations and experiments of probe-drogue berthing docking were used to compare with the proposed FMM. The comparison results of different initial deviation conditions indicate that the FMM method guarantees computation accuracy and increases computation speed by two orders of magnitude, which greatly reduces computation costs. Then this efficient FMM method was utilized to analyze the influence of key parameters, such as friction coefficient and cone angle, on the contact force and driving force of the docking mechanism. The conclusions of the parameter analysis of probe-drogue berthing docking can be used to reduce contact force and accelerate iterative design as a reference for the design of this kind of docking mechanisms, making the docking process optimized and reliable.

Inducing and Switching the Handedness of Polyacetylenes with Topologically Chiral [2]Catenane Pendants

AbstractTo explore the chirality induction and switching of topological chirality, poly[2]catenanes composed of helical poly(phenylacetylenes) (PPAs) main chain and topologically chiral [2]catenane pendants are described for the first time. These poly[2]catenanes with optically active [2]catenanes on side chains were synthesized by polymerization of enantiomerically pure topologically chiral [2]catenanes with ethynyl polymerization site and/or point chiral moiety. The chirality information of [2]catenane pendants was successfully transferred to the main chain of polyene backbones, leading to preferred‐handed helical conformations, while the introduction of point chiral units has negligible effect on the overall helices. More interestingly, attributed to unique dynamic feature of the [2]catenane pendants, these polymers revealed dynamic response behaviors to solvents, temperature, and sodium ions, resulting in the fully reversible switching on/off of the chirality induction. This work provides not only new design strategy for novel chiroptical switches with topologically chiral molecules but also novel platforms for the development of smart chiral materials.

Inducing and Switching the Handedness of Polyacetylenes with Topologically Chiral [2]Catenane Pendants.

To explore the chirality induction and switching of topological chirality, poly[2]catenanes composed of helical poly(phenylacetylenes) (PPAs) main chain and topologically chiral [2]catenane pendants are described for the first time. These poly[2]catenanes with optically active [2]catenanes on side chains were synthesized by polymerization of enantiomerically pure topologically chiral [2]catenanes with ethynyl polymerization site and/or point chiral moiety. The chirality information of [2]catenane pendants was successfully transferred to the main chain of polyene backbones, leading to preferred-handed helical conformations, while the introduction of point chiral units has negligible effect on the overall helices. More interestingly, attributed to unique dynamic feature of the [2]catenane pendants, these polymers revealed dynamic response behaviors to solvents, temperature, and sodium ions, resulting in the fully reversible switching on/off of the chirality induction. This work provides not only new design strategy for novel chiroptical switches with topologically chiral molecules but also novel platforms for the development of smart chiral materials.

Dynamic mechanical response and failure behavior of solid propellant under shock wave impact

Solid rocket motor propellants are typically subjected to shock wave loads during ignition. To analyze the dynamic mechanical response and failure behavior of hydroxyl-terminated polybutadiene (HTPB) propellant under varying shock intensities, this study innovatively employed a shock tube apparatus in conjunction with schlieren imaging and 3D-DIC techniques. Shock loading experiments were conducted on propellant samples of three different thicknesses under pressures ranging from 0.3 to 0.7 MPa, capturing the dynamic deformation processes. Results revealed that deformation initiated at the clamped region, extending towards the center and forming a parabolic shape. The maximum deformation of the samples shows an approximately linear relationship with the launch pressure and decreases with increasing sample thickness. The 5 mm sample failed under a 0.6 MPa shock pressure, with electron microscopy images identifying matrix damage, particle debonding, and particle fracture as the principal failure mechanisms. Finite element simulations based on the generalized Maxwell linear viscoelastic constitutive model were conducted, demonstrating good agreement with experimental data. The critical stress for fracture was determined to be 4.12 MPa, and the ultimate shock wave pressures for 3, 6, 9, and 12 mm thicknesses were approximately 0.3 MPa, 0.65 MPa, 1.1 MPa, and 1.4 MPa, respectively. These findings provide valuable insights for assessing the structural integrity of solid rocket motors under ignition shock conditions.

Dynamic ancillary services: From grid codes to transfer function-based converter control

Conventional grid-code specifications for dynamic ancillary services provision such as fast frequency and voltage regulation are typically defined by means of piece-wise linear step-response capability curves in the time domain. However, although the specification of such time-domain curves is straightforward, their practical implementation in a converter-based generation system is not immediate, and no customary methods have been developed yet. In this paper, we thus propose a systematic approach for the practical implementation of piece-wise linear time-domain curves to provide dynamic ancillary services by converter-based generation systems, while ensuring grid-code and device-level requirements to be reliably satisfied. Namely, we translate the piece-wise linear time-domain curves for active and reactive power provision in response to a frequency and voltage step change into a desired rational parametric transfer function in the frequency domain, which defines a dynamic response behavior to be realized by the converter. The obtained transfer function can be easily implemented e.g. via a proportional-integral (PI)-based matching control in the power loop of standard converter control architectures. We demonstrate the performance of our method in numerical grid-code compliance tests, and reveal its superiority over classical droop and virtual inertia schemes which may not satisfy the grid codes due to their structural limitations.

Investigation of friction induced vibrations on a nonlinear two degree of freedom mathematical model and experimental validation

This article investigates the dynamic behavior of a low order nonlinear mathematical model, which is developed based on an existing mass-sliding belt experiment. First, the proposed model is developed with kinematic and friction nonlinearities, and the corresponding governing equations are obtained. Governing equations are then solved numerically for certain operating parameters, and the characteristics of different dynamic responses are investigated. It is observed from the numerical solutions that the dynamic response of the system can be deterministic or chaotic based on the set of operating parameters. Furthermore, the period doubling mechanism is found to be the path from deterministic to chaotic behavior. Second, experiments are performed at a wide range of operating parameters in order to calculate the dynamic friction coefficient, which are used in artificial neural network models for the generation of friction models as functions of operating parameters. It is observed that these operating parameters have significant influence on the variation of the dynamic friction coefficient. Third, the friction models developed with artificial neural network approach are implemented in the nonlinear mathematical model, and numerical solutions are obtained at the same operating parameters. Finally, the numerical results of the low order nonlinear mathematical model are compared to the experimental data, and it is concluded that there is a good correlation between the model predictions and measurements from the perspectives of fundamental frequencies and the characteristics of the dynamic responses. Hence, a better insight about the dynamic response behavior of the mass-sliding belt experiment is achieved through the bifurcation analyses.

Light‐activated 3D printed fish‐like actuator

AbstractHydrogel‐based actuators are innovative materials that exhibit responsive and dynamic behavior in response to external stimuli, making them promising candidates for a wide range of applications in fields such as soft robotics. We employ 3D printing to create layered rectangles, using a passive ink composed of gelatin methacryloyl (GelMA) and an active ink consisting of GelMA and poly(N‐isopropylacrylamide) (PNIPAM). Our aim is to assess and compare the bending capabilities of these structures based on their layer arrangements in a buffer above the lower critical solution temperature. Therefore, an asymmetric rectangular structure is selected as the shape‐changing component in the tail of a 3D printed fish‐shaped hydrogel actuator. We show that gold nanostars integrated into the actuators serve as photothermal elements, enabling the fish tail to repeatedly bend when near infrared light is turned on and off. Our effort illustrates the potential of combining 3D printing, responsive hydrogels and photothermal elements with near infrared light towards soft robotic applications. This combination yields actuators capable of shape‐shifting without requiring localized light or transitioning between environments with varying temperatures.

Quasi-distributed optical fiber sensing for the coupled vibration analysis of high-speed train-bridge coupled system under earthquakes

Due to the extensive construction of high-speed rail lines passing through seismically active areas, the possibility of a sudden earthquake occurring during train operation is very high. Additionally, the earthquake will intensify the dynamic response of trains and bridges, causing serious bridge damage. In this work, the dynamic response behavior of the bridge structures in the coupled train-bridge system under the earthquake is investigated based on the 4-table shaking table system. Shaking table experiments are also conducted on a high-speed railroad model of simple-supported girder bridge at a scale of 1/10 with the simulated layers of China Railway Track System type II (CRTS II) ballastless track slabs. The strain responses of various components, including rails, track plates, base plates, and beams, were measured on the bridge using quasi-distributed fiber optic gratings, both with and without seismic actions. Additionally, the seismic isolation characteristics of the fasteners and the CA mortar layer were investigated. The dynamic performance of the coupled train-bridge system under earthquakes was studied in both the time and frequency domains.

Real-time X-ray diffraction measurement on laser shock-loaded hexanitrostilbene (HNS)

Understanding the lattice evolution of hexanitrostilbene (HNS) is crucial for ensuring its safety and reliability under shock loading. However, the lack of in situ, real-time diagnostics has limited the availability of lattice parameters for shock-loaded explosives. In this study, we utilized dynamic X-ray diffraction technology to obtain the diffraction spectrum of laser shock-loaded HNS and to determine its temporal evolution. Additionally, by improving the laser energy, we initiated HNS and obtained the diffraction spectrum of detonation products during the detonation process. The experimental results showed the presence of a diamond structure in the detonation product, suggesting the existence of either diamond or diamond-like carbon. Our research not only elucidates the crystal structure of shock-loaded HNS and its detonation products but also provides an avenue for laboratory-scale investigations into dynamically loaded explosives, which furnishing an opportunity to unveil the underlying mechanism governing explosive dynamic response behavior.

Exploring Dynamic Spalling Behavior in Rock–Shotcrete Combinations: A Theoretical and Numerical Investigation

Spalling is a widespread dynamic disaster during blasting excavation in underground engineering. To clarify the coupled dynamic response and spalling behavior of an underground tunnel with a spray anchor, an investigation based on the rock–shotcrete combination was conducted using theoretical and numerical methods. The mathematical representation of stress wave propagation between rock and shotcrete was deduced based on the elastic stress wave theory. A novel method for predicting the location and time of initial spalling in a rock–shotcrete combination was proposed. A numerical simulation was conducted to verify the validity of the proposed theoretical method. In addition, the effect of the material’s tensile strength, the loading amplitude, and the thickness of shotcrete on the stress evolution and spalling characteristics was studied. The results demonstrate that the initial spalling locations are sensitive to the relationship between the normalized tensile strength of the rock, shotcrete, and interface. A high incident amplitude can cause the initial spalling in rock, and the shotcrete or rock–shotcrete interface can cause initial spalling due to a low incident amplitude. The stress evolution and spalling characteristics are sensitive to the thickness of shotcrete. The location of the initial spalling failure changes with the thickness of the shotcrete. An appropriate increment in thickness and normalized strength of the shotcrete is beneficial to the dynamic stability of underground engineering.

Dynamic response and damage behavior of impact wear for polycrystalline diamond compact under low kinetic energy impact

Polycrystalline diamond compact (PDC) cutters are the main load-bearing components in shale gas drilling, and their performance significantly affects the efficiency of shale gas extraction. One of the primary reasons for cutter failure is the dynamic impact between the rock and the cutter due to the complex geological conditions of shale gas extraction. Investigating the impact wear behavior and damage mechanisms is vital to designing superior-performing PDC structures and improving their effectiveness in engineering applications. This work investigates the kinetic response and damage behavior of PDCs under low kinetic energy impacts to explain the characteristics and mechanisms of PDC impact wear. The results show that the impact force fluctuates with impact owing to changes in the interface state. Owing to the elastic-plastic properties of PDC, 87 % of the kinetic energy is used for plastic deformation and fracture. Secondly, the contact time and kinetic energy absorption rate only relate to the impact mass. The contact time positively correlates with mass, while the kinetic energy absorption rate changes in the opposite direction. In addition, diamond fracture occurs with a low kinetic energy accumulation of only 0.059 J. Cobalt catalysis and stress effects were found to induce graphitization and carbon rehybridization jointly during impact wear. It is concluded that the PDC impact wear mechanism under low kinetic energy impact is a brittle fracture with a combination of transcrystalline fracture and intergranular fracture. This work provides referable basic research data for designing impact-wear resistant PDC structures and improving the efficiency of shale gas extraction.