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Effective identification of dynamic loads on vehicle systems is crucial for evaluating the structural integrity of railway vehicles. The inverse problem method has been proposed for dynamic load identification to determine the impact load on the carbody. Due to the sparse nature of the impact load, the combination of the l1-norm and TwIST (two-step iterative threshold shrinkage method) methods is used to reconstruct the impact load, taking into account the influence of sensor placement on the identification results. The MOHBA (Multi-objective Optimisation Honey Badger Algorithm) was proposed to simultaneously select the regularisation and iteration parameters. This algorithm aims to improve the accuracy of subsequence load reconstruction by considering the influence of noise levels when selecting the measured data. The impact load experiment was conducted on the scale carbody, and the single-point impact load and multi-point impact load matched well with the actual load. Satisfactory load identification results can still be achieved when the noise level is within 15%. When arranging measurement points on the boundary of the vehicle body, satisfactory load identification results can also be achieved. [ABSTRACT FROM AUTHOR]

The mechanical response of the Ti-4.5Al-2.9V-3Fe alloy demonstrates a significant strain rate strengthening effect and strong ductility at high strain rates (3.0 × 103/s), contrary to the typical behavior of titanium and its alloys which exhibit a trade-off between these properties. Our recent studies have revealed that this unusual improvement can be attributed to a transformation in the plastic deformation mechanism, specifically from slip-dominating to twinning–slipping combination, under dynamic loading conditions compared to quasi-static loading conditions. Microstructure characterization before and after loading confirms this change in deformation mechanism. Furthermore, simulation predicts a dramatic adiabatic temperature rise in the necking region, which may contribute to strain softening effects observed experimentally. These findings provide valuable insights for manufacturing strategies and enhance our understanding of the mechanical behavior exhibited by titanium alloys. [ABSTRACT FROM AUTHOR]

A bottom–up multi-scale performance transfer chain is developed to ascertain the gradual change in the law of vibration characteristics in spatial steel truss structures under fatigue loading. This chain derives the interrelationship between vibration characteristics and the performance of each structural component. Based on the evolution characteristics of the performance model of the member scale in the transfer chain, a new analytical model of the shape function is established. Building on these foundations, a refined model was formulated to depict the gradual change of vibration characteristics in spatial steel truss systems under fatigue loading. This model integrates the cumulative damage rule, the structural residual performance rule, the finite element method and other pertinent theories. The gradual change in vibration characteristics of a steel truss girder bridge subjected to train loads was analyzed using a self-developed three-dimensional finite element analysis framework tailored explicitly for assessing gradual change issues in spatial steel truss structures. The analysis results indicate that the effective residual cross-sectional area and the structural frequency continuously decline as the service time increases. This comprehensive study advances the understanding of fatigue-induced changes in spatial steel truss structures. It offers analytical perspectives for predicting and mitigating the long-term impacts of dynamic loads on large-scale infrastructural components. [ABSTRACT FROM AUTHOR]

This study systematically investigates the mechanical properties of plain concrete (PC) and 2% steel fiber reinforced concrete (SFRC) under both static and dynamic loading conditions, utilizing advanced mechanical testing equipment and dynamic impact testing methods. The strain rate range studied spans from 10−4 s−1 to 483.12 s−1. Under static loading conditions, the maximum bearing capacity and energy absorption capacity of 2% SFRC are 2.16 times and 3.83 times greater than those of PC, respectively, indicating a significant enhancement in toughness and resistance to failure. Under dynamic loading conditions, the energy absorption capacity of SFRC increases to 6.36 times that of PC. The impact failure behavior of SFRC was analyzed using the split-Hopkinson pressure bar—digital image correlation (SHPB-DIC) method, revealing that the failure was primarily driven by splitting tension. The failure process was subsequently categorized into four distinct stages. At high strain rates, the dynamic enhancement factor, peak stress, and peak strain of SFRC exhibit a linear increase with strain rate, whereas the energy absorption capacity increases in a nonlinear manner. This study presents a simplified viscoelastic constitutive model with four parameters and develops a damage-based viscoelastic constitutive model with seven parameters, demonstrating its broad applicability. The findings offer both theoretical insights and experimental evidence to support the use of SFRC under high strain rate conditions. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Magnetorheological elastomers (MREs) are innovative materials composed of ferromagnetic particles embedded within a polymer matrix, enabling real‐time tunability of mechanical properties through external magnetic fields, thereby generating pronounced mechanical‐magnetic coupling effects. However, the mechanical performance of MREs, particularly their load‐bearing capacities under dynamic conditions, remains constrained by the limitations of conventional matrix materials. In this study, shear‐stiffening gel (SSG), exhibiting viscoelastic mechanical behavior, is incorporated into magnetorheological elastomers to develop magnetorheological shear‐stiffening elastomer (MSSE) through a high‐temperature and high‐pressure vulcanization process. The mechanical‐magnetic coupling behavior of these composites is systematically evaluated utilizing a series of mechanical experiments across varying strain rates. Notably, the interaction between carbonyl iron particles (CIPs) and the molecular chains within the shear‐stiffening matrix significantly enhanced the magnetorheological effects of MSSEs, particularly under dynamic impact loadings. Leveraging the adjustable modulus of MSSEs and drawing inspiration from the microstructural characteristics of beetle exoskeletons, a beam‐structured 3D buffer device is designed. This device demonstrates superior energy absorption capacity, underscoring its potential for advanced flexible protection applications. [ABSTRACT FROM AUTHOR]

ABSTRACT To investigate the stress‐confinement effect on the dynamic crack propagation and energy evolution characteristics of heterogeneous granite under impact loading, a three‐dimensional equivalent grain‐based model (3D‐GBM) and FLAC3D‐PFC3D coupled modeling technique was used to establish a numerical model of a full‐scale true triaxial Hopkinson test system. The results indicate that: (1) A rate‐effect model of the dynamic strength enhancement factor for heterogeneous rocks under multiaxial static and dynamic combined loading was constructed, with lateral stress confinement enhancing the sensitivity of dynamic strength to the strain rate. (2) Axial stress reduces the crack initiation stress ratio (σci/σd) and damage stress threshold ratio (σcd/σd), reducing the time to their onset, while lateral stress has the opposite effect. (3) Lateral stress confinement helps dynamically adjust the types of microcracks within the rock, restricts the relative slip friction between particles, and decreases the kinetic energy of failure. (4) At approximately the same strain rate, the strain energy and slip friction energy sequentially increase under uniaxial, biaxial, and triaxial stress confinement. The mutual slip friction and movement between rock particles are more intense under biaxial stress confinement compared to uniaxial conditions. [ABSTRACT FROM AUTHOR]

This paper aims to examine the behavior of cracked adhesive joints experimentally and numerically when they are subjected to quasi-static and dynamic loads using the tensile and falling-wedge impact tests, respectively. Double cantilever beam (DCB) specimens were manufactured and tested under impact loading with varying impact energies to analyze the adhesive joint mode-I dynamic fracture response. To determine quasi-static and dynamic mode-I fracture energies, the compliance-based beam method (CBBM) was utilized accounting for the axial force exerted by the wedge. It was found that by changing the loading condition from quasi-static to impact, the maximum force and fracture energy of adhesively bonded joints were considerably increased by 275% and 452%, respectively. However, within the impact test conditions, increases of 10% and 22% were obtained in maximum force and fracture energy when the impact energy was tripled. The adhesive joints tested under static loading experienced a mixed interfacial/cohesive failure pattern, whereas by shifting the loading condition to impact, the failure pattern turned fully cohesive. The quasi-static and dynamic fracture responses of adhesive joints were modeled using the cohesive zone model employing a triangular traction-separation law. The numerical and experimental results exhibited reasonable correlation. [ABSTRACT FROM AUTHOR]

To enhance the impact resistance of hydraulic columns, a theoretical analysis method was employed to develop a dynamic characteristic analysis model for conventional columns under impact loads. This model facilitated the derivation of key parameters such as equivalent stiffness, maximum retraction amount, and impact duration. A fluid-solid coupling model for the conventional column was constructed using finite element and coupled Eulerian-Lagrangian (CEL) methods. Subsequently, numerical simulation results were compared and analyzed against theoretical predictions. Based on this analysis, an energy-absorbing column was designed, and its fluid-solid coupling model was established to investigate its mechanical response under static and dynamic impact loads.The findings indicate that under a static load of 2000 kN, when superimposed with impact loads of 200 kJ, 400 kJ, and 800 kJ respectively, the peak impact forces on energy-absorbing columns are 89.20%, 91.72%, and 98.42% lower than those on normal columns. The yield displacements of energy-absorbing columns increase by 142.26%, 109.15%, and 108.41% compared to normal columns. Energy absorption in energy-absorbing columns is 152.11%, 171.80%, and 145.18% higher than in normal columns. Furthermore, initial velocities of energy-absorbing columns are consistently lower compared to normal columns. After reaching initial velocity, energy-absorbing columns exhibit reduced oscillations due to interactions between the energy absorber, column, and hydraulic fluid system under impact loads. Unlike normal columns, energy-absorbing columns mitigate stress concentration at the column head through interactions between the energy absorber, emulsion, and column. Additionally, the impact resistance time of energy-absorbing columns is 2.19, 1.64, and 1.85 times longer than that of normal columns.Energy-absorbing columns outperform conventional columns across six metrics: peak impact force, column yield displacement, energy absorption, column movement speed, stress distribution, and impact resistance time, demonstrating superior mechanical properties in impact resistance. [ABSTRACT FROM AUTHOR]

The surrounding rock stiffness has a significant effect on the impact mechanical properties of rockbolts. In order to study the influence of radial stiffness of surrounding rock on the dynamic characteristics of the end-anchored rockbolt, numerical simulations of drop weight impact tests on the end-anchored rockbolt were conducted using finite element method. The simulation results show that the larger the radial stiffness of the surrounding rock, the larger the value of the absorbed impact energy of end-anchored rockbolt. However, there is an upper limit to the effect of radial stiffness on the dynamic behavior of end-anchored rockbolt, i.e., the value of absorbed impact energy tends to be stabilized when the radial stiffness exceeds 2.91 GPa/mm. In the impact simulation, the fracture position of the bolt bar is affected by both radial stiffness and impact energy. The greater the radial stiffness of the surrounding rock, the further the fracture location is away from the anchorage end. The larger the impact energy is, the closer the fracture location is to the anchorage end. It is important to study and determine the range of fracture location of anchor rods to develop new types of anchor rods and to design the support scheme for the surrounding rock under dynamic loading. Finally, due to the linkage between numerical simulation and indoor tests, the effect of steel pipe wall thickness on the upper and lower limits of the results also provides a theoretical basis for the rationalization of the design of steel pipe wall thickness. The study of dynamic impact fracture location of bolt bar is of great significance for the development and design of new types of rockbolt under dynamic loading. [ABSTRACT FROM AUTHOR]

Dimensional analysis methods have shortcomings in predicting the behavior of full-scale samples using small-scale results due to non-linearity of behavior, loading, or changes in material type, the inability to simultaneously predict two parameters with the same unit, and a limited number of independent degrees of freedom are independent. Recently, a new theory called Finite Similitude has been proposed to solve these problems, and in this article, using this theory to analyze the prediction of the dynamic behavior of concrete beams using the results of concrete beams on a smaller scale and beams with similar behavior to concrete (plaster-stone) under dynamic impact loading has been discussed. The predicted results such as force, displacement, energy, and time show that the dimensional analysis of the results with different materials is not accurate enough and in some cases, the difference in the results is more than 50%. However, with the finite similitude method, the behavior of full-scale concrete beams can be predicted by using small-scale plaster-stone samples with less cost, reduced construction time, and high accuracy, so that the error percentage in dynamic analysis in all samples is almost less than 10% was achieved [ABSTRACT FROM AUTHOR]

Shipping impact and wave loads impose dynamic loads on jetties and platforms in the sea, which cause the vibration of structures. Recently, many advanced viscous damper devices have been developed for implementation in structures to diminish structural vibration due to earthquakes or wind. However, the longitudinal configuration of conventional viscous damper devices requires adequate space to locate the damper device within the frame structure, which limits the application of viscous dampers for use in jetties or platforms to dissipate the vibrations imposed by ship impact or wave force. For this reason, in this study, an attempt has been made to develop a new viscous plane damper device applicable in limited space positions where the longitudinal damper device is not able to fit. For this purpose, the initial design for the viscous plane damper device is proposed, and the prototype of the device is manufactured. Then, the performance of the fabricated viscous plane damper is examined through experimental tests by applying cyclic loads using a dynamic actuator. In order to investigate the effect of the diameter and configuration of the piston's orifices, five different diameters for the orifices of 1, 2, 5, 8, and 10 mm are included, and three different distribution configurations of the orifices in the piston plate as Configurations A, B, and C are manufactured and tested experimentally. The lab testing is conducted by applying cyclic loads with different frequencies to evaluate the performance of the developed plane damper device under various load velocities. Accordingly, the dynamic performance of the damper device, including the damping force, effective damping and stiffness and the energy dissipation capacity obtained from the hysteresis response (force–displacement result), is investigated. The results of the experimental tests prove the functionality of the developed device to generate the desired damping force and vibration energy dissipation during applied cyclic loads. Therefore, the new plane damper device can be implemented in any structure to dissipate the effect of imposed vibration. [ABSTRACT FROM AUTHOR]

The present paper reports on various test methods and techniques which have been developed throughout the last decades. These methods have been used to evaluate both axial and shear performance of tendons under impact loading mode. Based on the literature review conducted on the scientific documents, published between 1992 and 2024, the developed facilities mainly work based on the direct impact and momentum transfer methods. In the direct impact method, which can be done in-situ and in the laboratory, the impact energy is applied by a mass freely falls to the test sample. In the momentum transfer method, the test assembly, consisting of both the mass and test sample free-fall at the beginning of the test until the movement of the assembly is halted by a stopper, and the momentum of the mass is transferred to the test sample. Besides, most of the current facilities are working based on the direct impact method. It was also found that less research have been conducted on dynamic shear testing, especially high-strength cable bolts, as most of the facilities have been designed for pull testing. In addition, it was found that in dynamic pull-out tests of rock bolts, two main mechanisms of energy absorption are identified: steel plastic deformation and bolt sliding within the encapsulation medium. The first impact plays a key role in energy absorption, causing significant permanent displacements, while the energy consumed in displacing the bolt is more indicative of dynamic behavior than the total input energy. According to the results, the tendons that undergo static deformations before dynamic loading are more prone to failure as some parts of their performance have already lost. Meanwhile, differences between dynamic and static shear tests suggest that dynamic tests require less energy for failure, as friction is ineffective in impact loading. Finally, the study highlights gaps in the current understanding of tendon performance under impact loading, with potential research directions aimed at improving safety in underground excavation. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tensile failure of complex branching cracks will cause irreversible damage to the structures. In this paper, the effects of the crack orientations, the local branch lengths, and the different load forms on the crack propagation pattern and the bearing capacity of structures are investigated based on the phase field method and experimental research method. The results show that the bearing capacity and propagation patterns of the specimens change significantly with the change of the orientation of the Y-shaped crack under tensile load. The local branch length of the crack only affects the sequence in which the regional crack reaches the final failure and the bearing capacity of the specimen. Under the dynamic impact load, the bifurcation phenomenon occurs, and with the increase of the dynamic impact load, the number of bifurcations increases. The crack propagation pattern in the numerical simulation is completely consistent with the experiment, and the difference in the maximum reaction force is 2.5%. [ABSTRACT FROM AUTHOR]

In the current study, contrary to conventional fiber-reinforced composites, polyamide fiber was used as reinforcement material, and the effects of thermoplastic fiber reinforcement on repeated low velocity impact (LVI) responses of composites were examined. In this regard, polyamide fiber-reinforced composites were fabricated using the vacuum-assisted hand lay-up method (VAHLM) and then exposed to repeated LVI loadings. Experimental tests were performed on the specimens for 100 impacts with a constant velocity of 3 m/s, which is equivalent to 25.2 J, and the impacts of repeated LVI loadings on the dynamic responses such as peak force, energy absorbing/rebounding, total impulse, bending stiffness and contact stiffness were examined. Moreover, the damage mechanisms resulting from the relative damage accumulation depending on the impact numbers were examined. According to the findings, the thermoplastic polyamide fibers absorbed more than 60% of the applied energy, and the absorbed energy increased with ascending impact number. Furthermore, the thermoplastic fiber-reinforced epoxy composites gained stiffness with increasing impact, which was linked to the thermoplastic chain structure. Despite quite a number of impact loadings, no serious damage mechanisms such as fiber breakage, perforation, or penetration were observed, and the specimens maintained their structural integrity. Due to the higher energy absorption of thermoplastics, the utilization of polyamide fibers in composites has been found to be well suited for applications subjected to repeated impacts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sandwich structures are widely used in engineering fields, but their connection and assembly problems become more and more prominent, especially for combat equipment under strong dynamic loads. How to design connection joints to improve the reliability and maintainability of the structure is a hot research topic at present. Aimed at the connection and assembly problem of honeycomb sandwich protection structures in typical combat environment, a quick assembly joint locked by square tubes was designed, and the dynamic responses of the connection structure under different impulses were obtained by foam projectile impact tests. Then the finite element method was used to simulate the impact test, and the simulation results agree well with the experimental results. On this basis, the effects of geometric parameters such as wall thicknesses and connection unit widths on the peak deflections of the structure under the foam projectile impacts were further discussed with the finite element model. The results indicate that, the thinner wall thickness (tt/tf≤0.375) of the square tube makes the connection structure prone to collapse, leading to a significant increase in peak deflections. However, a smaller width (2a/W≤0.267) of the connection unit causes the panel tensile strength to decrease, thereby weakening the impact resistance of the connection structure. In addition, as the connection unit width increases, the peak deflection of the connection structure will first decrease and then increase. This is due to the competition mechanism between the effective cross-sectional area of the connection unit and the mechanical interlocking contact area. The proposed quick assembly connection joint can effectively resist dynamic impact loads, has good impact energy absorption abilities, and easy maintenance and replacement. It is hopeful to be applied to the connection of various types of main combat equipment protection structures, and provides reference for the impact resistance design of sandwich connection structures. [ABSTRACT FROM AUTHOR]

The CFG pile technology is primarily employed for foundation reinforcement, offering cost-saving benefits and demonstrating significant reinforcement effects. Consequently, it has gained widespread utilization. However, due to its unique composition and exceptional strength characteristics, investigating the dynamic properties of rubber particle loess-CFG poses significant challenges. In this study, a numerical simulation approach is employed to investigate the dynamic characteristics of rubber particle loess-CFG and its deformation response under dynamic loading is analyzed. The results indicate that the deformation of rubber particle loess-CFG remains minimal under static loading, while it significantly increases under dynamic loading. However, the vertical and horizontal displacements at the top of the mattress layer are comparatively smaller than those observed in loess-CFG, highlighting their seismic stability. The mattress layer of the rubber particle loess-CFG undergoes vertical compression and deformation, while being horizontally squeezed towards the central region. The horizontal displacement and its variation range are significantly greater than that of the entire pile and the soil between piles. Therefore, it is crucial to analyze the material properties, thickness, and extent of the mattress layer during design in order to mitigate its influence. When subjected to dynamic loading at the base of the model, the rubber particle loess-CFG exhibits a strip distribution of vertical displacement which gradually decreases from bottom to top. Moreover, as focal depth increases, the impact of dynamic loading on foundation deformation diminishes. Consequently, rubber particle loess-CFG provides a dual functionality of enhancing foundation strength while effectively resisting dynamic deformations. These research findings provide a theoretical basis for designing reinforced foundations using rubber particle loess-CFG and offer an innovative approach for recycling waste tire rubber particles. [ABSTRACT FROM AUTHOR]

This study aims to investigate the behaviour of reinforced concrete (RC) beams strengthened by Carbon Fibre-Reinforced Polymer (CFRP) under static and impact loads. A series of RC beams were tested and categorized into four groups, namely, unstrengthened RC beams (B1), RC beams strengthened with a CFRP longitudinal strip in the tension zone (B2), RC beams wrapped with CFRP fabric (B3), and RC beams strengthened with a combination of both CFRP longitudinal strips and wraps (B4). The results show that the average load–displacement capacity of RC beam group (B4) was improved by 84.88% as compared with the unstrengthened beam (B1) under static loads. The dynamic test results demonstrated an increase in the deflection resistance of RC beam group (B4) by −57.89% as compared with unstrengthened RC beam group (B1) under identical drop weights of 1 m. In addition, a collapse failure mode was noticed in the unstrengthened beams, while minor damage was recorded mainly in the case of RC beam group (B4). Furthermore, the numerical analysis conducted using LS-DYNA software (V 971 R6.0.0) proved that the adopted numerical models can efficiently predict the behaviour of RC beams under dynamic loads, with maximum differences reaching up to −12.5% compared with the experimental test results. [ABSTRACT FROM AUTHOR]

Purpose: During operation, dynamic load from the road surface acting on the vehicle affects the dynamic safety of the vehicle. Therefore, it is necessary to research solutions to reduce the dynamic load of the multi-purpose forest fire fighting vehicle. While the active and semi-active suspension system equipped on the vehicle has not been effective compared to the price, the optimal solution to reduce the current dynamic load is to replace the traditional suspension using springs with the air suspension system. This research aims to replace the leaf spring suspension of a multi-purpose forest fire fighting vehicle with an air suspension system in an effort to lessen the vehicle's dynamic load. Methods: By building a dynamic model of the vehicle according to the method of splitting the structure of the multi-body system (MBS) and the Newton–Euler equation, in which the binding force between the suspended and unsuspended masses is described by two submodules are "leaf-spring" and "air balloons". Use this model to investigate the influencing factors including vehicle speed and road type on the dynamic load of the vehicle. The results of the study were carried out on the road type in accordance with ISO 8608:2016 to estimate the DLC value for vehicles utilizing spring suspension and air suspension to evaluate the level of decrease in dynamic loads placed on the vehicle. Results: The survey results of the model with two types of suspension systems compared show that when using an air suspension instead of a metal suspension (leaf-spring) on a multi-purpose forest fighting vehicle, the dynamic load can be reduced up to 19.6%, contributing to reducing the impact load on the vehicle. Conclusions: The author has conducted research and analysis on the capability of reducing dynamic loads based on road type and speed, and evaluation according to DLC criteria. According to the findings, automobiles equipped with air suspension systems perform significantly better; according to ISO 8608:2016, when a vehicle is moving on a road of class A, B, or C, the vehicle is not limited in speed but nevertheless ensures road-friendly criteria. This ensures the detailed durability and dynamic safety of the vehicle. Class D roads are restricted to a maximum speed of 15 km/h, which helps to meet the aforementioned standards, Even with the air suspension system, the vehicle fails to achieve the road-friendly criteria necessary to guarantee its detailed durability and dynamic safety when driving on extremely poor roads (class F), but wheel separation appears narrower than leaf spring suspension. [ABSTRACT FROM AUTHOR]

Structural systems and structural elements can often suffer severe damage or even completely collapse under the effect of sudden dynamic impact loading, which is a different type of loading that is not considered during their design. Research on how structures behave under impact loading and how they can be strengthened to perform better against this type of loading has increased to avoid such undesirable severe damage. Within the scope of this study, it is aimed to improve the behavior and increase the performance of two-way steel fiber-reinforced concrete (SFRC) slabs, one of the leading structural elements that can be affected by impact loading, using steel fiber concrete (SFC) and placing steel plates on the surface of the RC slab. Within the scope of the study, the effects of placing FRC as layers in different positions within the slab and placing the steel plate on different surfaces of the slabs were examined. Impact loading was applied using a drop weight test setup designed by the authors, and the acceleration–time, displacement–time, and impact loading–time behaviors of the RC slabs were measured and interpreted. The use of fiber concrete in RC slabs and strengthened with steel plates increased the maximum acceleration values by an average of 3% and 113%, respectively. The use of fiber concrete in RC slabs reduced the maximum displacement and residual displacement values by an average of 2% and 25%, respectively. Placing steel plates on the slabs reduced the maximum displacement and residual displacement values by an average of 270% and 199%, respectively. In addition, the energy absorption capacities of RC slabs were calculated, and how they were affected by experimental variables was examined. Numerical analyses of the RC slabs tested in the study were also conducted using ABAQUS finite element software, and the results obtained were compared with the experimental ones. [ABSTRACT FROM AUTHOR]

The present study is aimed at upgrading the passenger car's front inner bumper. The dynamic explicit time-stepping method IMPACT was used to conduct the impact analysis. The programme was first evaluated against experimental findings for beams subjected to impacts at low loads. The deviation between the simulated and experimental findings of the deflected beam ranged from 1.6% to 9.5%. The genuine bumper was subjected to two different kinds of impact simulations. The data were used as a standard against which to compare future bumper improvements. Internal energy absorption is much higher in all the conditions. All three designs are able to absorb more energy without changing their overall performance. [ABSTRACT FROM AUTHOR]

In order to analyze the ground vibration responses induced by the dynamic loads in a tunnel, this paper proposes a new simplified tunnel–soil model. Specifically, based on the basic theory of the thin-layer method (TLM), the basic solution of three-dimensional layered foundation soil displacement was derived in the cylindrical coordinate system. The perfectly matched layer (PML) boundary condition was applied to the TLM. Subsequently, a tunnel–soil dynamic interaction analysis model was established using the volume method (VM) in conjunction with the TLM-PML method. The displacement frequency response function of the foundation soil around the tunnel foundation was derived. Finally, a ground vibration test under an impact load in a tunnel was carried out. The test and calculated results were compared. The comparison results show that the ground vibration acceleration response values within 25 m from the load are similar. Compared with the test results, the theoretical calculation results exhibit a decreasing trend in the range of 40–80 Hz between 25 and 60 m, with the maximum reduction being approximately one order of magnitude. In addition, the experimental comparison demonstrates that the model can be used to analyze the ground vibrations caused by underground loads. [ABSTRACT FROM AUTHOR]

In engineering, soft rock is often damaged by dynamic loads such as dynamic compaction, vibrating compaction and blasting, resulting in varying degrees of damage. To understand the compressive response, fracture characteristics and energy dissipation characteristics of red bed soft rock under different dynamics, we carried out a series of dynamic impact tests by the separated Hopkins pressure bar system. The experimental results show that the dynamic peak stress, critical strain and toughness of red bed soft rock increase with the increase in strain rate with the increase in strain rate, which ranges from 37 to 102 s−1. Specifically, the dynamic compressive strength of red bed soft rock at 98 s−1 is 4.63 times that of the quasi-static average. As the strain rate increases, the fracture characteristics: integrity, slightly split and pulverized, and the size of fragments decrease and the number of fragments increases. When the strain rate exceeds the critical value 72 s−1, the fracture characteristics are pulverized. The energy dissipation density increases with the strain rate and increases faster when the strain rate exceeds the critical value. The energy utilization first increases and then decreases, when the strain rate is 88 s−1, the maximum utilization rate is 38%. [ABSTRACT FROM AUTHOR]

This study examines the impact of cutting regimes on determining cutting resistance in the processing of polypropylene (PP) using the CNC lathe EMCO F5. The rationale for this research stems from polypropylene's rarity among thermoplastics in possessing structural stability, allowing for its comparison to metals and practical application in products replacing metal parts. Leveraging its favorable mechanical properties, polypropylene finds utility in producing parts subject to dynamic loads, boasting high resistance to impact loads—particularly undesirable in machining. An advantageous characteristic of polypropylene is its affordability, rendering it an economical choice across numerous applications. Despite these merits, polypropylene's exploration in cutting processing remains limited, underscoring the novelty of this research endeavor. The main method for determining cutting resistance involves measuring electric current strength during processing. This direct measurement, facilitated by input cutting regime parameters, is recorded by the PLC controller, with the current value extracted from the machine tool's ammeter. The experimental approach entails varying cutting regime parameters—cutting speed (v), feed rate (s), and depth of cut (a)—across minimum and maximum values, recognized as pivotal factors influencing cutting force development and the attainment of the desired machined surface quality. [ABSTRACT FROM AUTHOR]

Load balancing plays a critical role in optimizing resource utilization and enhancing performance in cloud computing systems. As cloud environments grow in scale and complexity, efficient load balancing mechanisms become increasingly vital. This paper presents a comprehensive review of load balancing techniques in cloud computing systems, with a focus on their applicability, advantages, and limitations. The review encompasses both static and dynamic load balancing approaches, evaluating their effectiveness in addressing the challenges posed by cloud infrastructure, such as heterogeneity, scalability, and variability in workload demands. Furthermore, the review examines load balancing algorithms considering factors such as resource utilization, response time, fault tolerance, and energy efficiency. Additionally, the impact of load balancing on cloud performance metrics, including throughput, latency, and scalability, is analyzed. This review aims to provide insights into the state-of-the-art load balancing strategies and serve as a valuable resource for researchers, practitioners, and system designers involved in the development and optimization of cloud computing systems. [ABSTRACT FROM AUTHOR]

Hydro-viscous clutch has already become an inevitable choice for special vehicle transmission in the present and future. As a nonlinear system with a large hysteresis loop, its speed control performance is affected by input rotational speed, lubricating oil temperature, lubrication pressure, and other factors. The traditional control method cannot adjust the temperature and rotational speed, which will lead to problems of narrow speed range, poor rotational speed stability, and large dynamic load impact. In order to solve the above problems, this paper studies the control method of an integrated multi-parameter hydro-viscous speed control system (HSCS) in a controlled environment. Through the mechanism analysis of the law of HSCS, the influence law of speed and temperature during the system operation is found. The temperature closed loop based on model predictive control (MPC) is introduced to control the rotational speed, and then the traditional PID control results are compensated according to the speed closed loop. Next, a novel double closed loop control method of temperature and rotational speed for HSCS is formed. Finally, the simulating verification is carried out. Compared with the traditional control method, the design method in this paper can adjust the control parameters according to the temperature of the lubricating oil and the input rotational speed and effectively expand the domain of HSCS and the speed control stability. The effective transmission ratio is extended to 0.2~0.8, and the hydro-viscous torque and speed fluctuation under the engine rotational speed fluctuation are reduced by more than 30%. The novel control method of HSCS designed in this paper can effectively improve the influence of input rotational speed and lubricating oil temperature on the speed control performance of HSCS and can be widely used in nonlinear HSCS such as hydro-viscous clutch. [ABSTRACT FROM AUTHOR]

Understanding fundamental track behaviors under dynamic load conditions is important to optimize design practices and achieve high-quality track performance. The American Railway Engineering and Maintenance-of-Way Association provides recommended practices to estimate trackbed pressures, which are primarily based on the Talbot equations. The Talbot methodology for computing crosstie-ballast (CT-B) interfacial pressures may "not" be valid for modern railroad design due to several factors, including the sensitivity of pressure measuring equipment, the presence of uneven support conditions, and the implementation of jointed rails in testing different wheel loadings, which contributed to overestimation of pressure readings as a result of impact loading. However, modern railroad infrastructure has been designed with a smooth track layout and well-supported rails as well as incorporating rolling stock equipped with smooth wheels, particularly in high-speed train operations. This study proposes a new approach to estimate the pressures at the CT-B interface, which was developed using measured in-track CT-B interfacial pressures taken from an active mainline. The data from the in-track measurements were filtered by using a signal processing tool and analyzed to develop basic equations to predict interfacial pressures as a function of basic train characteristics, including train speed, wheel loads, and wheel spacing, assuming no impact loading from wheel defects. To validate the efficacy of the square wave theory, the predicted pressures were compared with the data obtained from in-track tests. Further, a method to estimate dynamic pressures of a moving train at the CT-B interface was developed using square wave theory. By representing the vehicles of a train as a periodic square waveform, the dynamic CT-B interfacial pressures can be predicted for an unlimited number of locomotives and cars for smooth track geometry, smooth wheels, limited rail surface roughness, and well-supported track. [ABSTRACT FROM AUTHOR]

Through a series of static mechanical tests and (SHPB) dynamic impact tests, the static and dynamic mechanical parameters of rock as represented by yellow sandstone are determined, and the Holmquist-Johnson-Cook model parameters of the rock are calibrated using the test data and theoretical calculations. The feasibility of a numerical model is verified, and numerical analysis of the SHPB impact process under different radial pressure pre-loading is carried out on the basis of good verification. The results show that with increasing impact load, the degree of rock breakage increases, as does the dynamic tensile strength. With the application of increasing pre-static pressure, the dynamic tensile strength of the rock decreases gradually, and the maximum radial cumulative strain increases continuously under a given impact pressure, indicating that micro-cracks in the rock develop initially and then expand under the influence of pre-static pressure; the rock is more easily broken, and its weakening degree increases. Under coupled dynamic and static loading, the energy utilization rate of rock in the Brazilian splitting process is jointly affected by axial compression ratio and impact load. Too large a pressure ratio will reduce the strain-rate sensitivity of rock, resulting in low energy utilization rate, while too low an axial compression ratio will make the dynamic tensile strength of rock relatively high, which is not conducive to tensile failure. Therefore, on the premise of clear fracture form requirements, a suitable combination of axial compression ratio and impact velocity can improve the rock crushing effect and energy utilization rate. [ABSTRACT FROM AUTHOR]

The harsh environment during airplane take-off and flights with complex operating conditions require a high dynamic and impact resistance capability of airplane engines. The design, development, and performance evaluation of new turbofan engines are generally performed through numerical simulations before a full-scale model or prototype experiment for certification. Simulations of fan blade containment tests can reduce trial–error testing and are currently the most convenient and inexpensive alternative for design; however, certification failure is always a risk if the calibration of material models is not correctly applied. This work presents a three-dimensional computational model of a turbofan for designing new engines that meet the certification requirements under the blade containment test. Two calibrated Johnson–Cook plasticity and damage laws for Ti64 are assessed in a simulation of a turbofan blade containment test, demonstrating the ability of the models to be used in the safe design of aircraft engine components subjected to dynamic impact loads with large deformations and adequate damage tolerance. [ABSTRACT FROM AUTHOR]

Flexible ring nets exhibit complex nonlinear mechanical behaviour when subjected to static and dynamic impact loads. This research presents the development of an efficient numerical model for assessing the performance of flexible netting barriers used in debris flow and rockfall risk mitigation. The model is calibrated through benchmark analyses and based on the equivalent stiffness method. The results demonstrate that the proposed numerical approach offers a significant computational cost reduction of 80% compared to complex numerical models while maintaining high accuracy. The coupled Eulerian–Lagrangian finite element method (CEL) is employed to simulate fluid–debris–structure interaction, showing damage characteristics consistent with flexible ring net barriers. The model is suitable for accurately determining the impact forces acting on the barrier and presents the debris behaviour and movement at various flow velocities. Notably, the results confirm that the presented model is capable of evaluating the interaction between the flexible barrier and debris flow with boulders and is an efficient approach to estimating the performance of flexible protection subjected to impacts. [ABSTRACT FROM AUTHOR]

Due to the fact that traditional rock constitutive models are constructed under static loading conditions and cannot accurately describe the mechanical behavior of rocks under dynamic loading, it is of great theoretical value to study the dynamic constitutive theory exhibited by layered shale under impact loading. This article constructs a dynamic damage constitutive theory for layered shale based on the dynamic mechanical deformation and failure characteristics exhibited by shale with different bedding dip angles in impact loading experiments. Based on this theoretical model, a program of the finite element method was developed to numerically simulate the impact test process of layered shale. The results indicate that the finite element program developed based on the dynamic damage constitutive model in this article can effectively reflect the dynamic mechanical characteristics of layered shale during impact loading. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to improve the life of the printed circuit boards (PCB) used in computers based on modal analysis by increasing the natural frequency of the PCB assembly. Design/methodology/approach: In this work, through experiments and numerical simulations, an attempt has been made to increase the fundamental natural frequency of the PCB assembly as high as practically achievable so as to minimize the impacts of dynamic loads acting on it. An optimization tool in the finite element software (ANSYS) was used to search the specified design space for the optimal support location of the six fastening screws. Findings: It is observed that by changing the support locations based on the optimization results the fundamental natural frequency can be raised up to 51.1% and the same is validated experimentally. Research limitations/implications: Manufacturers of PCBs used in computers fix the support locations based on symmetric feature of the board not on the dynamic behavior of the assembly. This work might lead manufacturers to redesign the location of other surface mount components. Practical implications: This work provides guidelines for PCB manufacturers to finalize their support locating points which will improve the dynamic characteristics of the PCB assembly during its functioning. Originality/value: This study provides a novel method to improve the life of PCB based on support locations optimization which includes majority of the surface mount components that contributes to the total mass the PCB assembly. [ABSTRACT FROM AUTHOR]

Rock excavation by disc cutters is widely employed in tunnel boring machine (TBM). Rock-breaking impact load acted on disc cutters especially when cutting heterogeneous rock, which if not properly dealt with, may induce cracking of disc cutters. The impact load is excitation source of the TBM dynamic response and it is feasible to analyze the law of impact load based on dynamic response. In this study, a set of real-time dynamic response monitoring and analysis system was installed in a slurry TBM of a water delivery tunnel in Beijing to analyze the impact load action law that induced cracking of the cutter ring, and a series of in-situ tunneling experiments were carried out. The time-domain and frequency-domain characteristics of acceleration response were deeply investigated. The results show that compared with the static parameters, such as thrust and torque of the TBM, the acceleration response is extremely sensitive to changes of the driving parameters (advance speed, cutterhead rotating speed and penetration rate) and rapidly attenuates from the cutterhead to the shield tail of the machine. In the full section quartzy sandstone stratum, the acceleration response of the cutterhead is significantly increased with the slight improve of the penetration rate and the rotating speed and the effect of the penetration rate is larger. The acceleration response is small during the TBM tunneling with low penetration rate–high rotating speed, which is also applicable to the broken stratum. The results of dynamic response test indicate that the impact load resulting in cracking of cutter ring can be effectively reduced by three methods: reducing penetration rate, reducing rotating speed and tunneling with low penetration rate–high rotating speed. The statistical data of cutter wear validate this conclusion. The findings in the engineering practice can provide valuable references for similar TBM construction. Highlights: In situ tests were conducted to analyze the effect of driving parameters on TBM dynamic response. The dynamic load of disc cutters was investigated from the perspective of TBM dynamic response. Three measures were proposed to reduce the cracking of disc cutter ring. The measures were verified by the statistical analysis data of cutter failure. [ABSTRACT FROM AUTHOR]

The macroscopic mechanical characteristics and microscopic pore structure evolution were investigated in gas-bearing coal subjected to creep loading superimposed with drop hammer impact loads, under different gas adsorption pressures, creep stress levels, and impact load magnitudes. The results show that, as gas adsorption pressure, creep stress level, and impact load increase, the peak strength of coal specimens decreases, while the peak axial strain and radial strain increase. Low-temperature liquid nitrogen adsorption tests demonstrated that the maximum adsorption capacity, total specific surface area, total pore volume, and the proportion of specific surface area and pore volume of micropores in intermediate-sized coal specimens decrease with increase in the three variables. In contrast, the proportion of specific surface area, total proportion of pore volume, and the fractal dimension of transition pores and mesopores increase, indicating a transformation of micropores into transition pores and mesopores. Importantly, a strong linear correlation was established between the damage rate of coal specimens and the proportion of micropore specific surface area, pore volume, and pore fractal dimension. These findings lay the groundwork for developing a macro–micro combined damage and failure constitutive model for gas-bearing coal subjected to superimposed dynamic and static loads, thereby enhancing the theoretical framework of rock dynamics. [ABSTRACT FROM AUTHOR]

Rockfalls are major geological hazards threatening prestressed concrete cylinder pipes (PCCPs) in water diversion projects. To accurately assess the impact of large deformation movements of rockfalls on PCCPs, this study utilized the continuous–discontinuous method to investigate the dynamic response of a PCCP under a rockfall. The impact mode of rockfalls, the mechanical characteristics of PCCP, and the nonlinear-contact characteristics between soil and PCCP were considered in this study. The advantages of continuous and discontinuous numerical simulation methods were utilized to establish a continuous and discontinuous coupling model of "tube-soil-rock" considering the interaction of soil and structure. The impact mechanism and process of PCCP under the rockfall were investigated by simulating the rockfall process and analyzing its spatiotemporal evolution. The influence of PCCP under rockfalls with different heights and radii was studied to clarify the effects of these two parameters on the PCCP. Combined with a practical application example of large-scale water transfer projects, there is a tendency of center flattening under static load and dynamic impact load, and the PCCP part directly below the impact point is the most dangerous. This investigation provided a comprehensive understanding of the impact mechanism of the PCCPs under rockfall. The findings of this study have significant implications for the design of the protection engineering of PCCPs and ensuring the safe operation of water diversion projects. [ABSTRACT FROM AUTHOR]

Tensile test under quasi-static loads conditions is usually used to determine the mechanical strength of thermoplastic starch films. This kind of test does not fully illustrate the load conditions for packaging films, which, under the conditions of use, are succumb to dynamic loads. Thus, the aim of the study was to present the possibilities of using a patented soft tissues measurement testing station to analyze the mechanical strength of thermoplastic starch (TPS) films under impact loading conditions. Two groups of film specimens containing the addition of psyllium husks (TPS/PH) and psyllium flour (TPS/PF) were used for the measurements. The casting method was applied, and glycerol was used as a plasticizer. Microstructure of the specimen surface was analyzed by stereoscopic microscopy. Specimens with the addition of psyllium flour had a more uniform microstructure. The maximum breaking forces obtained during impact tests for these films were 5 times higher than specimens containing psyllium seed husk. The same behaviour was found with respect to stresses with average values of 48.6 MPa for TPS/PF and 20.2 MPa for TPS/PH. Moreover, research confirms usefulness of patented soft tissues measurement testing station to analyse the mechanical strength of thermoplastic starch films. [ABSTRACT FROM AUTHOR]

Regular blasting in opencast coal mines generates significant ground vibrations, impacting mine slope stability and posing risks to life and property. This study focuses on monitoring ground vibrations in an opencast coal mine through near-field monitoring and investigating the impact of blast-induced seismic loading on slope stability. The approach involves a pseudostatic method utilising Strength Reduction Factor (SRF), based on Finite Element (FE) numerical modelling software. The study examines a pit slope with a tension crack under seismic loading, varying the intensity of seismic coefficients (Ks) from 0 to 0.5. These coefficients are determined through field vibration monitoring during production blasts. In numerical modelling, seismic loading is considered in both horizontal (outward of slope face) and vertically downward (in-line with gravity) directions. Numerical modelling incorporates dimensionless horizontal seismic coefficient (Kh) and vertical seismic coefficient (Kv), and both directions which is expressed as Seismic Coefficient Ratio (SCR) which is the ratio of Kv and Kh for interpretation of results. Although SCR induces changes in the Factor of Safety (FoS), its impact is minimal compared to seismic loading solely in the horizontal direction. Consequently, increasing SCR leads to a decrease in FoS. The study observes that Peak Ground acceleration (PGA) in the longitudinal direction has greater dominance than in the transverse direction. Additionally, the seismic wave in the horizontal direction destabilises the slope more than the corresponding vertical seismic wave. These findings are elucidated in the context of the Critical Slip Surface (CSS). [ABSTRACT FROM AUTHOR]

One important parameter for evaluating the safety and reliability of a ship is o the dynamic ultimate load capacity of ship structures. Because of the importance of this parameter, its determination is essential. In this paper, a novel "two-step" approach for determining the dynamic ultimate load capacity of ship structures is proposed. The main idea of two-step approach is to determine the dynamic ultimate load capacity based on the static ultimate load capacity after accounting for impacts that cause strain on the ship structures. This approach is based on nonlinear finite element method. Here, taking stiffened plate as a case study, the practical application of thus two-step approach is discussed in detail. The results of this approach reveal that the static ultimate load capacity decreases by less than 3% after a stiffened plate is subjected to an impact load whose amplitude corresponds to the dynamic ultimate load capacity. Then, the influence of the impact duration on the failure mode and the effect of the impact load cycles and the impact load sequence on the dynamic ultimate load capacity of the stiffened plate were investigated. Finally, the applicability of the two-step approach to a hull girder is demonstrated. The two-step approach and the conclusions presented in this paper can provide guidance for the evaluation of dynamic ultimate load capacity. [ABSTRACT FROM AUTHOR]

Background: Tunnels extend the use of underground space for special applications such as transportation, mine development and civil defense. These structures could become susceptible to severe dynamic loads such as traffic loads, pile driving, impact and blast loads. Methodology: In this context, the experiment and simulations were conducted on semi-cylindrical tunnels of dimensions 1.2 m length × ∅ 0.5 m center-to-center and 0.05 m lining thickness under impact loading. The drop height was kept at 3.0 m and the burial depths of the soil cushion were varied as 0, 0.05, 0.10 and 0.15 m to study the effect of the cushion layer under repeated impact load. The experimental results were obtained in terms of damage to the tunnel and displacements in the tunnel under repeated impacts. Results: It was observed that the impact resistance of tunnels increased significantly when the natural burial depth increased from 0.05 to 0.10 m. It was concluded that the tunnel with 0.15 m burial depth was able to resist up to nine impacts as compared to the tunnel without cushion which offered resistance against two impact only. The numerical investigations were performed for each tunnel under repeated impacts using ABAQUS/Explicit. The numerical results were found to be in good agreement with the experimental results in terms of strain in rebar and mid displacement. The parametric study was performed for the influence of mass and velocity of the impactor in terms of crack pattern, impact force, displacement and energy absorption capacity in the tunnel. On increasing the mass of the impactor from 150 (4.41 kJ) to 400 kg (11.77 kJ), the energy absorption capacity was found to increase from 7.8% to 48.7%; however, on increasing the height of drop from 5 (5.1 kJ) to 20 m (20.40 kJ), the energy absorption capacity of the tunnel was increased from 8.1 to 48.6%. Conclusions: It was concluded that under the low-velocity impact, energy absorption in the tunnel is more sensitive to the mass of the impactor as compared to drop height. It was observed that Yang Qixin's algorithm was the best predicting algorithm among others when comparing peak impact force with the numerical result. [ABSTRACT FROM AUTHOR]

Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas. To improve the capacity of rock sheds for resisting rockfall impact, a sand and expandable polyethylene (EPE) composite cushion was proposed. A series of model experiments of rockfall impact on rock sheds were conducted, and the buried depth of the EPE foam board in the sand layer was considered. The impact load and dynamic response of the rock shed were investigated. The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion. Moreover, as the distance between the EPE foam board and rock shed roof decreases, the maximum rockfall impact force and impact pressure gradually decrease, and the maximum displacement, acceleration and strain of the rock shed first decrease and then change little. In addition, the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction. In conclusion, the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion, and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate. [ABSTRACT FROM AUTHOR]

In this study, field tests of highway subgrade dynamic response were conducted using a self-developed regular dodecahedron soil pressure sensor (RDSPS). The RDSPS can be used to quantify the total stress of the subgrade soil element. The effects of different axle loads, speeds, and vehicle types on the dynamic response of the subgrade were investigated. The spatial distribution law of the vertical dynamic stress of the highway subgrade was examined. An estimation model for the vertical dynamic stress and the influence depth of vehicle load was developed. The results suggest that, under the action of a moving traffic load, the principal stress axis continues to rotate. Both vehicle speed and axle load have an impact on the dynamic response of the subgrade; however, for newly built highways, the impact of the vehicle axle load on the dynamic stress is more significant. The vertical dynamic stress increases linearly with the speed or axle load of the vehicle. The attenuation law of the vertical dynamic stress caused by different types of vehicles on the subgrade along the depth direction is basically consistent, and the attenuation speed changes from fast to slow, with the fastest attenuation rate in the base layer. [ABSTRACT FROM AUTHOR]

Drill and blast tunneling is a cyclic construction process in which the rock away from the blast hole is subjected to cyclic blast load that can influence the dynamic behaviour, energy characteristics and damage evolution of the rock. To study the dynamic mechanical properties and energy evolution of granite under cyclic impact loading, dynamic tests were performed on 100-mm-diameter granite samples at different impact velocities using a split Hopkinson pressure bar system. The stress–strain relationship, energy and damage evolution, and microscopic features of the rock are discussed and analyzed in detail. The results show that the stress–strain relationship of the granite is significantly sensitive to both impact velocity and number of impacts. At the same impact velocity, the peak dynamic stress decreases and the peak strain increases linearly with the increase in the number of impacts, while the peak stress decreases significantly and visible cracks appear or the sample is completely destroyed. Energy evolutions of granite samples during the cyclic impact process with different impact velocities present a uniform variation tendency, and the impact compressive process of granite samples can be divided into three stages: linear elastic deformation stage, plastic deformation-dominant stage and rock failure stage. The cumulative energy dissipation rate, defined as the sum of the ratio of total dissipated energy to the input strain energy after each impact loading, is proposed, and it increases linearly with the number of impacts. In addition, the damage evolution and microscopic features of the rock after cyclic impact loading are also discussed, and the microscopic fracture mode changes from the combination of intergranular and transgranular fracture to transgranular fracture with the increase of impact velocity. Highlights: Dynamic behavior and energy evolution of the granite with a diameter of 100 mm under cyclic impact loading with different impact velocities are investigated. Dynamic behavior of the granite is significantly sensitive to both impact velocity and impact number. The concept of cumulative energy dissipation rate which increases linearly with the impact number is proposed. Microscopic fracture mode of the granite under cyclic impact at different impact velocities are obtained. [ABSTRACT FROM AUTHOR]

The Donghekou landslide triggered by the 2008 Wenchuan earthquake was a typical large-scale rapid and long runout landslide. The saturated deposit material in runout path was liquefiable under the dynamic loading, which may play a key role in the hypermobility of the Donghekou landslide. The dynamic loading triaxial compression tests were performed to investigate dynamic responses of the soil samples from the runout path. The influence of variation of pore water pressure of deposit in runout path on the movement process of the landslide was investigated and analyzed by discontinuous deformation analysis (DDA). The results show that the impact loading could cause a sharp rise of the pore water pressure of the soil, but it cannot trigger liquefaction before the sample failure. Seismic loading is the main loading that causes the liquefaction of deposit material, while landquake loading has little effect on soil liquefaction. During the earthquake, liquefaction of the shallow soil (the depth was < 10 m) of deposit in the runout path was induced by the seismic loading. Thus, the shallow runout-path material and landslide debris can slide faster and farther under a significantly small friction. [ABSTRACT FROM AUTHOR]

Impact loads developed on a tool cutting edge when milling into a workpiece material are prevailing metrics for explaining coating fatigue failure and the subsequent tool-wear evolution. For predicting related stress and strain fields in the compound coating-substrate, stress, strain, and strain-rate, dependent material properties are required. The attainment of such data is briefly described in the paper. Considering these data, the occurring strains in the cutting edge at various entry impact durations, i.e., strain rates, were calculated and compared with fatigue-critical strains. In this way, the wear phenomena causing the coating failure on the flank and rake during milling were clarified. The attained results were also correlated to corresponding ones in turning, where the dynamic loads of the cutting edge are comparably negligible. The conducted investigations showed that the fatigue-critical strains strongly diminish, when the relevant strain rates increase; thus, leading to a remarkable tool-life reduction. This happens, because the increase of the strain-rate restricts the time for the dislocations movements; thus, regions with stress concentrations occur, deteriorating the material ductility, increasing its brittleness, and diminishing the fatigue critical strains. In cutting operations, where the coating fatigue is the main wear factor, the tool-life can be predicted considering these phenomena. In the paper, relevant experimental analytical procedures are introduced. [ABSTRACT FROM AUTHOR]