Magnitude Of Impact Load Research Articles

An Experimental Study of Wave Impact Loads on an FPSO Bow in 2D Wave-Tank

<i>In harsh environments, an floating production storage and offloading (FPSO) is occasionally damaged by impact loads, such as bow flare slamming and green water. This study conducted an impact load measurement experiment on a model of an FPSO bow in a 2D wave tank. Three types of frequency-focused waves (steep, spilling, and plunging) were generated, and the speed and slope of the waves were measured. Seven wave probes were placed in a row, and the wave elevation was measured to determine the speed and slope of the waves. In addition, the side of the 2D wave tank was photographed with a high-speed camera. The speed and slope of the waves obtained from the wave probe array agreed well with those obtained from the photographs taken using a high-speed camera. In the case of a steep wave, wave runup occurred at the bow before the wave reached the bow of the FPSO, so no impact load was generated, and only hydrostatic pressure was measured. Impact loads were generated in the spilling and plunging waves, and the magnitude of impact loads using the Von Karman’s estimation formula and the impact loads measured in model tests showed similar values.</i>

Topographic analysis of layer erosion in abrasive media

This article delves into the critical role of abrasive wear on the surface of plates in determining the long-term performance and reliability of pressing equipment utilized in the machinery industry. Operating within environments saturated with abrasive particles, these machines face challenges that impact their durability. The rate of deterioration is intricately linked to factors such as collision error, mechanical properties of materials, abrasive particle pressure, and the magnitude of impact loads. The separation of corrosive particles unfolds on a micro-scale, driven by the decomposition of metals resulting from mechanical fatigue, multi-cycle stresses, and repeated loading. By comprehensively examining these factors, this research aims to provide insights that contribute to the development of strategies for mitigating abrasive wear, thereby enhancing the overall operational longevity and reliability of pressing equipment crucial to the production of various machinery components.

МЕТОДЫ ОПРЕДЕЛЕНИЯ ОСНОВНЫХ ФАКТОРОВ, ВЛИЯЮЩИХ НА ЭФФЕКТИВНОСТЬ ТЕХНОЛОГИИ ДОБЫЧИ БЛОКОВ КАМНЯ МАШИНАМИ УДАРНОГО ДЕЙСТВИЯ

This paper presents the main factors influencing the efficiency of rock destruction by impact loading along the contour during mining of blocks in strong rocks, such as the magnitude of impact loading (energy of a single impact), geometric parameters of the working tool, parameters of the fracture scheme, etc. Approaches applied by research institutions in mining science have been scrutinized. A methodology of experimental work to determine the main parameters of fracture depending on the force, energy, and design parameters of the tool is developed. The graphs of dependence of specific energy consumption on the height of the craggy layer as well as of dependence of specific energy consumption of destruction on the energy of a single blow A and of specific energy consumption of marble destruction by a chisel on the height of the craggy layer and change of work value A on the depth of wedge penetration h into the rock are presented.

Foot Strike Run Retraining forPatients With Patellofemoral Chondral Defects: A Case Series.

Military service members (SMs) demonstrate high rates of patellofemoral chondral defects (PFCDs) that are difficult to diagnosis and, if untreated, result in a cascade of events eventually leading to osteoarthritis. Running is an essential occupational task for SMs; however, there is little evidence regarding techniques to maintain running ability in individuals with cartilage defects. The purpose of this case series was to assess the clinical application of foot strike run retraining in patients with PFCDs. This case series included two active duty U.S. Marine Corps SMs who presented to outpatient physical therapy with PFCD, diagnosed via MRI. Both patients attended eight foot strike run retraining sessions. Running mechanics and patient-reported outcomes were recorded pre-training, post-training, and at a 1-month follow-up visit. Both patients successfully converted their strike pattern from a rearfoot to a non-rearfoot strike pattern with training and retained this strategy at 1-month follow-up. Post-intervention, both patients demonstrated increased running tolerance, and improvements in Numeric Pain Rating Scale and Lower Extremity Functional Scale scores. Biomechanical analysis showed that both patients demonstrated a 63% to 70% reduction in average and peak vertical ground reaction force loading rates post-treatment. Modification of foot strike pattern from rear to non-rearfoot strike during running for individuals with PFCD can reduce the magnitude of impact loading, which potentially limits disease progression. These findings suggest that foot strike run retraining may be a feasible strategy to reduce pain and improve function in SMs with PFCD who are required to run for occupational responsibilities.

Analysis of PDC cutter cutting‐broken conglomerate based on the discrete element method

AbstractIt is well known that the magnitude of impact load is one main reason for polycrystalline diamond compact (PDC) cutter failure rapidly when drilling conglomerate formation. However, there are many factors affecting the magnitude of impact load. To assess and mitigate these impacts, the discrete element model of PDC cutting‐broken conglomerate has been established, and the influence law of cementation strength difference (CSD), gravel diameter, and cutting velocity on impact load and gravel fragmentation in the process of cutting broken conglomerate is performed. What is more, the laboratory experiment of rock cutting by different shaped PDC cutters under different CSD and gravel diameters has also been conducted, and the correctness of numerical simulation results is verified by laboratory experiment. Meanwhile, the cutting depth and impact load of different shape PDC cutters under different CSD and gravel diameters have been analyzed. First, the simulation results show that the stripping mode of gravel mainly occurs when the CSD is large, and the corresponding axial and tangential impact load (mean axial peak cutting force [MAPCF]/mean tangential peak cutting force [MTPCF]) is relatively small. As the decrease of CSD, the gravel will be directly broken and the magnitude of the MAPCF/MTPCF will gradually increase, and the probability of impact damage to the cutting cutter will incrementally increase. In addition, larger gravel diameter and cutting velocity will lead to larger MAPCF/MTPCF, and the mode of gravel fragmentation changes gradually from being stripped to being directly broken with the increase of gravel diameter. Second, the laboratory experiment results not only verify the correctness of the simulation results but also find that ridged diamond element cutter has the smallest impact load and the largest cutting depth under different CSD and gravel diameters. This paper can provide a theoretical foundation for the optimization of drilling parameters and PDC bit design in drilling conglomerate formation.

Experimental Research on the Effect of Bedding Angle on the Static and Dynamic Behaviors of Burst-Prone Sandstone

Abstract In order to understand the mechanism of some unconventional failures such as rockburst caused by deep rock excavation, the failure characteristics of burst-prone sandstone specimens under static and dynamic loads were studied by using the MTS816 rock mechanics testing system and the split Hopkinson pressure bar (SHPB) experimental system, as well as the effects of bedding angle and impact pressure on rock mechanical properties and failure patterns. The uniaxial compression test used a cylindrical specimen with a height of 50 mm and a diameter of 100 mm, and cylindrical specimens with height and diameter of 50 mm were adopted in the SHPB tests. The bedding angles in the tests are 0°, 45°, and 90°. In the dynamic impact test, three different impact pressures were applied to observe the magnitude of impact load on the mechanical behaviors of the burst-prone sandstone specimens. The results show that with the increase in the bedding angle, the uniaxial compressive strength firstly decreases and then increases. When the bedding angle is 45°, the uniaxial compressive strength is the lowest. The uniaxial compressive strength is highest when the bedding angle is 0°. The burst-prone sandstone specimens with different bedding angles had three different failure pattern types. Under the dynamic loading, the stress-strain curves show springback phenomenon; with the increase in impact pressure, the dynamic strength of the burst-prone sandstone specimens with each bedding angle increases; the fracture degree of the bedding sandstone specimens gradually increases. The dynamic strength of the 45° burst-prone sandstone specimen is the lowest, and it has the highest fracture degree.

Differences in Peak Impact Accelerations Among Foot Strike Patterns in Recreational Runners.

IntroductionRunning-related injuries (RRIs) occur from a combination of training load errors and aberrant biomechanics. Impact loading, measured by peak acceleration, is an important measure of running biomechanics that is related to RRI. Foot strike patterns may moderate the magnitude of impact load in runners. The effect of foot strike pattern on peak acceleration has been measured using tibia-mounted inertial measurement units (IMUs), but not commercially available insole-embedded IMUs. The aim of this study was to compare the peak acceleration signal associated with rearfoot (RFS), midfoot (MFS), and forefoot (FFS) strike patterns when measured with an insole-embedded IMU.Materials and MethodsHealthy runners ran on a treadmill for 1 min at three different speeds with their habitual foot strike pattern. An insole-embedded IMU was placed inside standardized neutral cushioned shoes to measure the peak resultant, vertical, and anteroposterior accelerations at impact. The Foot strike pattern was determined by two experienced observers and evaluated using high-speed video. Linear effect mixed-effect models were used to quantify the relationship between foot strike pattern and peak resultant, vertical, and anteroposterior acceleration.ResultsA total of 81% of the 187 participants exhibited an RFS pattern. An RFS pattern was associated with a higher peak resultant (0.29 SDs; p = 0.029) and vertical (1.19 SD; p < 0.001) acceleration when compared with an FFS running pattern, when controlling for speed and limb, respectively. However, an MFS was associated with the highest peak accelerations in the resultant direction (0.91 SD vs. FFS; p = 0.002 and 0.17 SD vs. RFS; p = 0.091). An FFS pattern was associated with the lowest peak accelerations in both the resultant and vertical directions. An RFS was also associated with a significantly greater peak acceleration in the anteroposterior direction (0.28 SD; p = 0.033) than an FFS pattern, while there was no difference between MFS and FFS patterns.ConclusionOur findings indicate that runners should be grouped by RFS, MFS, and FFS when comparing peak acceleration, rather than the common practice of grouping MFS and FFS together as non-RFS runners. Future studies should aim to determine the risk of RRI associated with peak accelerations from an insole-embedded IMU to understand whether the small observed differences in this study are clinically meaningful.

Linear Buckling Analysis of Landing Gear

In an aircraft the landing gear is the most critical system which acts as suspension during landing and take-off. During this, it experiences very large magnitude of impact load which is mostly compressive in nature. Hence, a major concern in this structure is buckling failure. Buckling is a mode of failure in which compressive forces act along the axis of the component. Buckling can cause catastrophic deformation of the component for slight increase in load acting on the body. Many a time buckling is the deciding factor for allowable stress. So, the buckling strength of the material used for landing gear should be sufficiently high enough to resist failure. Good corrosion resistance and low density makes Ti-6Al-4V (also called TC4) the most commonly used material for the landing gear. This paper deals with linear buckling analysis of landing gear and compares the result of three titanium alloys (TC4, Ti-7Al-4Mo, TIMETAL 834) for landing gear. The landing gear assembly is designed in CREO 3.0 and linear buckling analysis is performed in ANSYS 19.2.

A peridynamic model for dynamic fracture in functionally graded materials

We introduce a peridynamic model for functionally graded materials (FGMs) and study their dynamic fracture behavior. After verification of elastic wave propagation in FGMs and comparisons with analytical results for the classical model, we analyze dynamic fracture of a functionally graded plate with monotonically varying volume fraction of reinforcement. Mixed-mode loading is imparted by eccentric impact relative to a pre-crack. We study the influence of material gradients, elastic waves, and of contact time and magnitude of impact loading on the fracture behavior in terms of crack path geometry and crack propagation speed. The peridynamic simulations agree very well, through full failure, with experiments. The model leads to a better understanding of how cracks propagate in FGMs and of the factors that control crack path and its velocity in these materials. We discover an interesting effect that surface waves far from the crack tip have in “attracting” the crack towards their location. We discuss advantages offered by the peridynamic model in dynamic fracture of FGMs compared with, for example, FEM-based models.

Variation in Foot Strike Patterns during Running among Habitually Barefoot Populations

Endurance running may have a long evolutionary history in the hominin clade but it was not until very recently that humans ran wearing shoes. Research on modern habitually unshod runners has suggested that they utilize a different biomechanical strategy than runners who wear shoes, namely that barefoot runners typically use a forefoot strike in order to avoid generating the high impact forces that would be experienced if they were to strike the ground with their heels first. This finding suggests that our habitually unshod ancestors may have run in a similar way. However, this research was conducted on a single population and we know little about variation in running form among habitually barefoot people, including the effects of running speed, which has been shown to affect strike patterns in shod runners. Here, we present the results of our investigation into the selection of running foot strike patterns among another modern habitually unshod group, the Daasanach of northern Kenya. Data were collected from 38 consenting adults as they ran along a trackway with a plantar pressure pad placed midway along its length. Subjects ran at self-selected endurance running and sprinting speeds. Our data support the hypothesis that a forefoot strike reduces the magnitude of impact loading, but the majority of subjects instead used a rearfoot strike at endurance running speeds. Their percentages of midfoot and forefoot strikes increased significantly with speed. These results indicate that not all habitually barefoot people prefer running with a forefoot strike, and suggest that other factors such as running speed, training level, substrate mechanical properties, running distance, and running frequency, influence the selection of foot strike patterns.

The influence of lower extremity coronal plane movements on the passive regulation of instantaneous loading mechanics during running

Background: The repetitive transmission of impact forces may contribute to the aetiology of overuse injuries. Therefore determining the mechanisms that regulate impact loading has potential clinical significance. This study aimed to determine the influence of lower extremity coronal plane kinematics on the regulation of impact loading during running. Material/Methods: Thirty-six participants ran at 4.0 m.s-1striking the centre of a piezoelectric force platform with their dominant limb. Coronal plane angular kinematics about the hip, knee and ankle joints were measured using an eight-camera motion analysis system operating at 250 Hz. Regression analyses with instantaneous loading rate magnitude as a criterion were used to identify the coronal plane parameters associated with impact loading. Results: The overall regression model yielded Adj R2 = 0.37, p ≤ 0.01. Two biomechanical parameters were obtained as significant predictors of the instantaneous loading rate. Peak ankle eversion Adj R2 = 0.22, p ≤ 0.01 and peak eversion angular velocity of the ankle Adj R2 = 0.15, p ≤ 0.01 were found to be significant predictors of instantaneous loading rate. Conclusions: The findings of the current investigation therefore suggest that passive joint motions in the coronal plane can regulate the magnitude of impact loading, linked to the development of chronic injuries.

Multi-Thickness Target Plate Impact Experimental Approach to Failure Waves in Soda-lime Glass and Its Numerical Simulation

Abstract A multi-thickness target plate impact experimental technique is proposed in this paper and adopted in the research on the so-called failure wave phenomenon in soda-lime glasses, in which, four sub-targets in different thicknesses embedded in the target ring are impacted simultaneously and the longitudinal stress temporal curves at the backing surface of each of the sub-targets are measured by four manganin piezo-resistive stress sensors. Hence, the failure wave trajectory under a certain dynamic loading can be obtained by only one test, which can reduce considerably the experimental expense as well as the experimental period, and, more importantly, the measurement uncertainty resulted from different loading conditions in repetitious impact experiments is avoided. It is found that the propagating velocity of failure wave is approximate to a constant and increases with the magnitude of the impact loading, and there always exists an initial delay time for the initiation of failure wave behind the precursory shock wave, which decreases with the magnitude of impact loads. Moreover, a numerical simulation for the failure wave propagation is carried out by using the LS-DYNA applied software, together with a statistical isotropic elastic microcrack model to describe the dynamic damage evolvement of soda-lime glasses. It is demonstrated that both the critical damage value distributions and the free surface particle velocity temporal curves can be used to determine the failure wave trajectory, and the numerical results are consistent substantially with the experimental data.

Multi-Thickness Target Plate Impact Experimental Approach to Failure Waves in Soda-lime Glass and Its Numerical Simulation

Abstract A multi-thickness target plate impact experimental technique is proposed in this paper and adopted in the research on the so-called failure wave phenomenon in soda-lime glasses, in which, four sub-targets in different thicknesses embedded in the target ring are impacted simultaneously and the longitudinal stress temporal curves at the backing surface of each of the sub-targets are measured by four manganin piezo-resistive stress sensors. Hence, the failure wave trajectory under a certain dynamic loading can be obtained by only one test, which can reduce considerably the experimental expense as well as the experimental period, and, more importantly, the measurement uncertainty resulted from different loading conditions in repetitious impact experiments is avoided. It is found that the propagating velocity of failure wave is approximate to a constant and increases with the magnitude of the impact loading, and there always exists an initial delay time for the initiation of failure wave behind the precursory shock wave, which decreases with the magnitude of impact loads. Moreover, a numerical simulation for the failure wave propagation is carried out by using the LS-DYNA applied software, together with a statistical isotropic elastic microcrack model to describe the dynamic damage evolvement of soda-lime glasses. It is demonstrated that both the critical damage value distributions and the free surface particle velocity temporal curves can be used to determine the failure wave trajectory, and the numerical results are consistent substantially with the experimental data.

Development of a vehicle–track model assembly and numerical method for simulation of wheel–rail dynamic interaction due to unsupported sleepers

In practice, it is not very uncommon to find railway track systems with unsupported sleepers due to the uneven settlement of a ballasted track system. These unsupported sleepers are among the major vibration excitations for a train and track system when a train moves forwards on a track. The vibration induced by unsupported sleepers can cause a large dynamic contact force between wheels and rails. For heavily loaded high-speed trains, the deteriorated sleeper support may lead to accelerated degradation of the railway track and vehicle components, and may thus impose safety risk to the operation. This paper presents analyses of a coupled vehicle–track assembly consisting of a roll plane vehicle model, a continuous track system model and an adaptive wheel–rail contact model. In order to improve the simulation efficiency, a numerical approach based on the central finite difference method is proposed in this investigation. The developed model assembly and proposed simulation method are utilised to simulate the vehicle–track dynamic interaction in the presence of unsupported sleepers. The dynamic response in terms of the dynamic wheel–rail interaction force due to one or multiple unsupported sleepers is studied. Important factors influencing the dynamic wheel–rail interaction force in the presence of sleeper voids are also investigated. The results show that the vehicle speed, the gap size and the number of unsupported sleepers primarily dictate the magnitude of impact load which can be significant.

Analysis of pitch plane railway vehicle—track interactions due to single and multiple wheel flats

The dynamic impact forces caused by wheel defects such as a flat have been of primary concern for freight trains operating at high speeds. A pitch plane model of a railway vehicle coupled with a comprehensive three-layer track system model is developed to study impact forces generated at the wheel—rail (W—R) interface in the presence of wheel flats. The W—R interaction is described by the non-linear Hertzian contact spring, while the rail is represented by a continuous Euler beam. The Rayleigh—Ritz method is used to solve the coupled partial and ordinary differential equations of the vehicle—track system. An idealized haversine wheel flat with the rounded corner is included in the W—R contact model. The W—R interface forces are evaluated under single or multiple flats on a single as well as multiple wheels. The forces transmitted to the bearings, pads, and the ballast are also evaluated under impacts due to single as well as multiple wheel flats. The results obtained through parametric analyses are discussed in view of a desirable design and operating condition to reduce the magnitude of impact loads. The results suggest that the rail mass, rail pad stiffness and damping, bending stiffness of rail, and ballast mass affect the W—R impact force considerably, apart from the flat size and vehicle speed. The influence of phase between the multiple flats on the resulting magnitudes of impact forces is also evaluated. The results suggest that the impact loads due to two flats are comparable with those due to a single flat when the spacing between the two flats exceeds 45°. Furthermore, the magnitude of impact force due to a single wheel flat could be greater than that due to in-phase flats on both wheels, which can be attributed to the pitch dynamics of the bogie.

Identification of impact force in thick plates based on the elastodynamics and time-frequency method (II)

The paper presents a novel experimental method for the determination of the impact load in the thick plate based on the theoretical Green’s function and the measured waveforms by the sensors arrayed on the surface on the plate. This method requires the location of the impact load. For the accurate estimation of location of impact source in a plate, the arriving time difference between sensors and the propagation velocity of acoustic waveform are necessary. Their measurements are difficult since the acoustic waveforms are dispersive with multi modes in the plate. The time frequency analysis for the acoustic waveform gives the information about the time difference for multi mode dispersive waveform. For the estimation of location of impact source in a plate, the information on the group velocity of the A0 flexible mode is important. In the paper, various time frequency methods are introduced and their methods are compared with simulated signals. The combined higher order time frequency (CHOTF) is employed for dispersive information for the A0 mode flexible mode. The location of impact source and the magnitude of impact load are well estimated based on the theoretical Green’s function and the CHOTF for the acoustic waveforms measured by three sensors arrayed on the plate.

Stiffness and Damping Response Associated with Shock Attenuation in Downhill Running

Studies on shock attenuation during running have induced alterations in impact loading by imposing kinematic constraints, e.g., stride length changes. The role of shock attenuation mechanisms has been shown using mass-spring-damper (MSD) models, with spring stiffness related to impact shock dissipation. The present study altered the magnitude of impact loading by changing downhill surface grade, thus allowing runners to choose their own preferred kinematic patterns. We hypothesized that increasing downhill grade would cause concomitant increases in both impact shock and shock attenuation, and that MSD model stiffness values would reflect these increases. Ten experienced runners ran at 4.17 m/s on a treadmill at surface grades of 0% (level) to 12% downhill. Accelerometers were placed on the tibia and head, and reflective markers were used to register segmental kinematics. An MSD model was used in conjunction with head and tibial accelerations to determine head/arm/trunk center of mass (HATCOM) stiffness (K1), and lower extremity (LEGCOM) stiffness (K2) and damping (C). Participants responded to increases in downhill grade in one of two ways. Group LowSAhad lower peak tibial accelerations but greater peak head accelerations than Group HighSA, and thus had lower shock attenuation. LowSAalso showed greater joint extension at heelstrike, higher HATCOMheelstrike velocity, reduced K1stiffness, and decreased damping than HighSA. The differences between groups were exaggerated at the steeper downhill grades. The separate responses may be due to conflicts between the requirements of controlling HATCOMkinematics and shock attenuation. LowSAneeded greater joint extension to resist their higher HATCOMheelstrike velocities, but a consequence of this strategy was the reduced ability to attenuate shock with the lower extremity joints during early stance. With lower HATCOMimpact velocities, the HighSArunners were able to adopt a strategy that gave more control of shock attenuation, especially at the steepest grades.

脆性材料を対象とした衝撃曲げ試験に関する研究 : 数値解析による検討(モルタル試験体)

The purpose of this study is to establish the standardized testing method of the impact bending strength for brittle materials. We have proposed a testing method to measure the acceleration of the hammer. The basic properties of mortar specimens under impact bending load have been obtained by some experiments. In this paper, it was analytically clarified that the testing method in this study was reasonable to evaluate the impact bending strength of specimens. The behaviors of mortar specimens under impact bending load were calculated by FEM analysis that solved the two-dimensional wave equations. The acceleration curves measured in the experiments were used as input loadings for numerical analysis. The strains of the specimens calculated by FEM analysis coincided with the experimental results, so the acceleration of the hammer could be a value to express the magnitude of impact load to the specimen. Then it seemed that the mortar specimen cracked by tensile stress within the limits of the hammer velocity in this study because the calculated shearing stress of specimen was so small. The strain of specimen increased in proportion to the magnitude of impulse when the period of impact loading was shorter than the period of first normal mode of specimen. So it was reasonable to express the impact strength of the specimen by physical unit of impulse. In conclusion, it seems that the testing method and analytical method in this paper would be useful to evaluate the toughness of brittle materials under impulsive bending load.

A study of cavitation bubble collapse pressures and erosion part 2: Estimation of erosion from the distribution of bubble collapse pressures

Cavitation damage was studied both by the measurement of the collapse pressures of cavitation bubbles (impact loads), using a specially developed method, and by means of cavitation erosion tests on various metals in a vibratory facility. The magnitude of impact loads produced by the collapse of bubbles fluctuates over a wide range and there is a threshold value for the impact load which can contribute to the fatigue fracture of a surface. This value is considered to correspond to the fatigue limit of the material. Assuming the S- N curve for the fatigue in the eroded surface, Miner's law of impact loads is followed for the incubation period and the reciprocal of the volume loss rate during the stable period, regardless of the cavitation conditions and the materials.

Full Scale Measurements on LPG Carrier of Semi-Membrane Tank Type under Servise Condition

In this paper a summary of results is presented of full scale measurements on a LPG carrier of semi-membrane tank type which have been carried out for about two years during her voyage between Japan and the Persian Gulf.The unmanned measurements have been made on dynamic loads caused by liquid sloshing in a LPG tank of a restricted cargo filling ratio of either over 90% or below 30%. The test includes also measurements of reaction forces acting on a tank dome supporting the tank at upper deck structure. Long term measurements of ship notion as well as stresses due to longitudinal bending of hull girder have also been carried out. A statistical study has been made on a relationship between the ship motion and the frequency of occurrence of the liquid sloshing in LPG tank.The results of the measurements have been compared with results of bench test on liquid sloshing in model tank in order to investigate into the effect of tank size on the magnitude of impact load due to sloshing.