Showing papers on "Dynamic load testing published in 2008"
TL;DR: In this paper, an air blast simulation code was used to determine the blast loads at the front surfaces of the test panels, and these were used as inputs to finite element calculations of the dynamic response of the sandwich structure.
359 citations
TL;DR: In this paper, a new testing technique was proposed to relate the physical stress state of rock subjected to simultaneous coupled static and dynamic stresses, which involves modification of a split Hopkinson pressure bar, such that the test specimen is subjected to coupled axial static pre-stress, axial impact loading, and optional confining pressure.
328 citations
TL;DR: In this paper, a mesoscale model is adopted to analyze the dynamic tensile behavior of concrete at high strain rates; especially, the effects of the ITZ on the failure properties are analyzed.
182 citations
TL;DR: In this paper, a servo-hydraulic machine was used to perform dynamic tensile tests on four representative plastic materials following a practice guideline by the Society of Automotive Engineers (SAE).
142 citations
TL;DR: In this paper, a detailed investigation of axial performance of helical piles is presented, where axial loads are investigated for both tensile and compressive axial load loads.
Abstract: Helical piles are increasingly used to support and rehabilitate structures subjected to both tensile and compressive axial loads This paper presents a detailed investigation into the axial perform
140 citations
TL;DR: In this article, the effects of tooth profile modification on multimesh gearset vibration were studied and a nonlinear analytical model was proposed, which considers the dynamic load distribution between the individual gear teeth and the influence of variable mesh stiffnesses, profile modifications, and contact loss.
Abstract: This work studies the effects of tooth profile modification on multimesh gearset vibration. The nonlinear analytical model considers the dynamic load distribution between the individual gear teeth and the influence of variable mesh stiffnesses, profile modifications, and contact loss. The proposed model yields better agreement than two existing models when compared against nonlinear gear dynamics from a finite element/contact mechanics benchmark. These comparisons are made for different loads, profile modifications, and bearing stiffness conditions. This model captures the total and partial contact losses demonstrated by finite element. Perturbation analysis based on the proposed model finds approximate frequency response solutions for the case of no total contact loss due to the optimized system parameters. The closed-form solution is compared with numerical integration and provides guidance for optimizing mesh phasing, contact ratios, and profile modification magnitude and length. DOI: 10.1115/1.2976803
115 citations
TL;DR: In this paper, a dynamic model was developed, using MATLAB, and used for the prediction of the instantaneous dynamic loads of spur gears with symmetric and asymmetric teeth, and a 2-D three-tooth model for finite element analysis.
91 citations
TL;DR: In this paper, a rate-dependent continuum model for the dynamic modeling of concrete is presented by means of viscoelastic and visco-plastic constitutive relationships, which results in an increased tensile strength with increasing loading rate.
88 citations
TL;DR: In this paper, a study on the fluid-dynamic pulsations and the corresponding dynamic forces generated in a centrifugal pump with single suction and vaneless volute due to blade-volute interaction is presented.
Abstract: A study is presented on the fluid-dynamic pulsations and the corresponding dynamic forces generated in a centrifugal pump with single suction and vaneless volute due to blade-volute interaction. Four impellers with different outlet diameters, obtained from progressive cutbacks (trimmings) of the greatest one, were successively considered in the test pump, so that the radial gap between the impeller and the volute ranged from 8.8% to 23.2% of the impeller radius. The study was based on the numerical computation of the unsteady flow through the machine for a number of flow rates by means of the FLUENT code, solving the 3D unsteady Reynolds-averaged Navier-Stokes equations. Additionally, an experimental series of tests was conducted for the pump with one of the impellers, in order to obtain pressure fluctuation data along the volute front wall that allowed contrasting the numerical predictions. The data collected from the numerical computations were used to estimate the dynamic radial forces and torque at the blade-passing frequency, as a function of flow rate and blade-tongue radial gap. As expected, for a given impeller diameter, the dynamic load increases for off-design conditions, especially for the low range of flow rates, whereas the progressive reduction of the impeller-tongue gap brings about corresponding increments in dynamic load. In particular, varying the blade-tongue gap within the limits of this study resulted in multiplying the maximum magnitude of the blade-passing frequency radial force by a factor of about 4 for low flow rates (i.e., below the nominal flow rate) and 3 for high flow rates.
76 citations
TL;DR: In this article, a generic nonlinear, dynamic modeling technique was proposed to simulate discrete rock fractures due to blasting using the finite element method. But the authors did not consider the effect of the dynamic load on the fracture initiation and growth.
Abstract: This paper describes development of a generic nonlinear, dynamic modelling technique to simulate discrete rock fractures due to blasting using the finite element method. The element elimination technique together with a brittle, Rankine failure-type material model are used as a means to simulate the initiation and growth of fractures in the rock under the effect of blast-induced dynamic pressure pulse. Dynamic loads representing ideal and non-ideal detonations are simulated and a new method, termed as optimised pressure profile, is proposed to approximate the pressure-time profile of the blast load to model the dynamic load. Comparison of numerical model results with previously reported observations from the literature reveals the ability of the model as a predictive tool and supports the validity of the developed modelling procedure.
76 citations
TL;DR: In this article, the measured real and reactive power responses to voltage step are used as the input to parameter identification procedure based on curve fitting using least squares method and load model parameters are determined.
TL;DR: In this paper, the results of an experimental study on bonded joints, carried out by means of an instrumented impact pendulum, equipped to load overlap specimens in shear, are reported.
TL;DR: To the best of the knowledge, this is the first generic theoretical framework that can be used to evaluate the performance of many different dynamic load balancing schemes with simple closed-form results.
Abstract: While many interesting dynamic load balancing schemes have been proposed for efficient use of limited bandwidth and to increase the capacity of congested or hot spots (or cells) in wireless networks, to date, a comprehensive mathematical framework which encompasses all of these schemes does not exist. In this paper, we provide a unified mathematical framework for dynamic load balancing, which leads to closed-form performance expressions for evaluating the performance of some of the most important dynamic load balancing strategies proposed in the literature. To the best of our knowledge, this is the first generic theoretical framework that can be used to evaluate the performance of many different dynamic load balancing schemes with simple closed-form results. The accuracy of the results predicted by these analytical expressions derived from the theoretical framework is checked by comparing these results with simulation results provided in the literature for well-known schemes.
TL;DR: In this article, the interaction between the dynamic contact load and the tooth profile wear of POM and Nylon 66 plastic gear pairs is investigated and a dynamic model of a plastic gear pair is presented.
TL;DR: In this article, the authors focus on dynamic brittle crack propagation in an isotropic medium, where the crack deviates from a straight-line trajectory and goes through stop-and-restart stages.
TL;DR: In this article, the development of a soil plug inside an open-ended tubular pile with respect to the installation method is examined using numerical simulations and the penetration process is investigated.
Abstract: The development of a soil plug inside an open-ended pile with respect to the installation method is examined using numerical simulations. In this paper, the penetration process of an open-ended tubular pile with diameter D = 61 cm into granular soil is investigated. The aim is to achieve a better understanding of the mechanisms of soil plugging inside open-ended piles with respect to the installation method. As an example, the horizontal stress distribution inside the tubular pile after installation shows significant increase depending on the installation method. The numerical results are compared to experimental data.
20 Aug 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the dynamic compressive properties of aluminum matrix composites reinforced with 40 and 50 vol.% SiC paticles (SiCp/2024Al composites) were investigated at various strain rates ranging from 1250 to 2500 s −1 using split Hopkinson pressure bar (SHPB).
Abstract: The dynamic compressive properties of 2024 aluminum matrix composites reinforced with 40 and 50 vol.% SiC paticles (SiCp/2024Al composites) were investigated at various strain rates ranging from 1250 to 2500 s −1 using split Hopkinson pressure bar (SHPB). The results showed that the flow stress was strain-rate sensitive. The composites displayed different deformation mechanism at various strain rates. The flow stress kept increasing for 40 vol.% SiCp/2024Al and showed increase–decrease tendency for 50 vol.% SiCp/2024Al at high strain rates, and plastic strain of the composite exhibited considerable increase at high strain rates compared with the quasi-static values. The adiabatic heat generated during dynamic compression led to matrix softening/melting, which caused the instantaneous instability of composites with high reinforcement content under dynamic loading. The fracture surfaces were characterized by scanning electron microscopy. It was obvious that the matrix was softened/melted by heat generated during adiabatic compression.
TL;DR: In this paper, an implicit model is deduced with the primary unknowns of shear strain increments of slip systems under the corotational coordinate system, and the homotopy auto-changing continuation method combined with the Newton-Raphson (N-R) iteration is adopted.
TL;DR: In this article, the effect of initial static stress on the dynamic strength and deformation characteristics of concrete is investigated, and the relationship between dynamic strength factor and the initial stress is obtained.
Abstract: Concrete structures prior to being subjected to dynamic loadings such as earthquake have already withstood initial stress. So the study of strain-rate sensitivity of concrete should be closely related to the initial loading history that concrete experiences. Yet majority of available documents concerning the dynamic properties of concrete do not take the initial static loading history into consideration. In this study, experiments were carried out to investigate the effect of initial static stress on the dynamic strength and deformation characteristics of concrete. A prescribed load was initially applied on the specimen at a very low strain-rate and then a dynamic load was applied at a high strain-rate up to failure of the specimen. The relationship between dynamic strength factor and the initial stress is obtained. The comparison between the results by the proposed formula and those by experiments in this study indicates a good agreement. The stress–deformation curves obtained in the tests show that the initial static loading history plays an important role in the total deformation behavior of concrete. An explanation to the physical mechanisms of high strain-rate strength enhancement with different initial static stress was proposed.
TL;DR: In this article, the authors present an assessment procedure whereby only critical loading events are considered to allow for an efficient and accurate determination of independent values for characteristic (lifetime-maximum) static and total (including dynamic interaction) load effects.
TL;DR: In this paper, the deformation behavior of nickel-iron alloy Inconel 718 in shear was measured at strain rates of 0.01 s − 1 and up to 3000 s −1 with a quasistatic torsion machine and a split torsional Hopkinson bar, respectively.
TL;DR: In this article, the authors studied the dynamic buckling of a shallow pin-ended circular arch under a central radial load that is applied suddenly with infinite duration, and found that the buckling load increases with an increase of a dimensionless arch geometric parameter.
25 Jul 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, tungsten heavy alloys with fibrous grains were obtained by hot-hydrostatic extrusion at 950 °C with plastic deformation ratio of 75%.
Abstract: The tungsten heavy alloys (WHAs) with fibrous grains were obtained by hot-hydrostatic extrusion at 950 °C with plastic deformation ratio of 75%. Dynamic mechanical behaviors under uniaxial dynamic compression were systematically investigated with the angles between the loading direction and the extruding direction being 0°, 45° and 90°. The testing results show obvious difference in dynamic behaviors and susceptibility to adiabatic shear band (ASB) for different specimens. In the 0° specimens, no localized flow is observed. The 45° specimens exhibit slight localized shearing. In the 90° specimens, localized ASB was firstly observed at an angle of 45° with respect to the fibrous orientation followed by cracking, which is greatly desirable for kinetic energy penetration applications. Microstructure analyses reveal that the high susceptibility to ASB of the 90° specimens result from adiabatic temperature rising during dynamic loading and reduced strain hardening caused by the special micro-strained condition and fiber distribution.
TL;DR: In this paper, a methodology combining dislocation theory in the domain of thermally activated inelastic deformation mechanisms and the internal variable approach applied to thermo-elastic/viscoplastic behavior is developed, allowing for obtaining a physically based inELastic heat fraction expression.
TL;DR: In this paper, a 3D finite element model is presented to study the bridge-vehicle interaction and the results indicate that the DLA is correlated well with the velocity of the truck, especially at high speed.
TL;DR: In this paper, a new method for predicting an equivalent pile load-head settlement curve considering the elastic shortening of piles is presented, which can be used to effectively estimate the pile head settlement as well as pile capacity.
TL;DR: In this paper, the authors developed a practical technique to determine dynamic axle loads of multiple vehicles based on the measured bridge response, which can be determined using least squares regularization optimization, and used the updated static component (USC) technique to improve the accuracy and eliminate the difficulty of an optimal regularization selection.
TL;DR: In this paper, a two-phase deformation model for axially loaded structural elements is proposed, which retains the characteristic features of the initial compression and subsequent bending/buckling phases.
25 Jul 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors measured the dynamic compressive properties of a 60-vol.% TiB2/Al composite fabricated by squeeze casting method using split Hopkinson pressure bar.
Abstract: Dynamic compressive properties of a 60 vol.% TiB2/Al composite fabricated by squeeze casting method were measured using split Hopkinson pressure bar. The 60 vol.% TiB2/Al composite showed significant strain-rate sensitivity compared with the rate insensitive aluminum alloy matrix. The flow stress and the strain-rate sensitivity both showed rise/fall tendency at high strain rates. Moreover, a large plastic strain as 7.8% was obtained at 1850 s−1. The dynamic compression behavior of high reinforcement content composite was affected mostly by strain-rate strengthening and adiabatic heating softening mechanism at dynamic loading. Adiabatic heating cannot only accelerate the softening and flow of aluminum alloy matrix but also restrain the low-strain failure of high reinforcement content composites. The TiB2/Al composite exhibited a mixed failure characteristic that consist of cracking of reinforcement particles and ductile fracture of matrix alloy.
TL;DR: In this paper, a new technique called amplitude deviation curve (ADC) or slope deviation curve(SDC) has been developed, which is a modification of the operational deflection shape (ODS).