Showing papers on "Dynamic load testing published in 2021"
TL;DR: A new technique of intelligence system based on the adaptive neuro-fuzzy inference system (ANFIS)-group method of data handling (GMDH) optimized by the imperialism competitive algorithm (ICA) for forecasting pile bearing capacity is presented.
Abstract: The pile bearing capacity is considered as the most essential factor in designing deep foundations. Direct determination of this parameter in site is costly and difficult. Hence, this study presents a new technique of intelligence system based on the adaptive neuro-fuzzy inference system (ANFIS)-group method of data handling (GMDH) optimized by the imperialism competitive algorithm (ICA), ANFIS-GMDH-ICA for forecasting pile bearing capacity. In this advanced structure, the ICA role is to optimize the membership functions obtained by ANFIS-GMDH technique for receiving a higher accuracy level and lower error. To develop this model, the results of 257 high strain dynamic load tests (performed by authors) were considered and used in the analysis. For comparison purposes, ANFIS and GMDH models were selected and built for pile bearing capacity estimation. In terms of model accuracy, the obtained results showed that the newly developed model (i.e., ANFIS-GMDH-ICA) receives more accurate predicted values of pile bearing capacity compared to those obtained by ANFIS and GMDH predictive models. The proposed ANFIS-GMDH-ICA can be utilized as an advanced, applicable and powerful technique in issues related to foundation engineering and its design.
50 citations
TL;DR: The membrane structure is a flexible structure, which is easy to vibrate or even relax under dynamic load as discussed by the authors, and the relaxation of membrane structures is more like that of air.
Abstract: The membrane structure is a flexible structure, which is easy to vibrate or even relax under dynamic load. Engineering accident analysis shows that the relaxation of membrane structure is more like...
44 citations
TL;DR: In this article, impact tests were conducted on prismatic granite containing two rectangular holes with different axial static pre-stresses by a modified split Hopkinson pressure bar (SHPB), and uniaxial compression tests were also carried out for comparison.
Abstract: To deeply understand the failure characteristics of defective rock under actual stress condition, impact tests were conducted on prismatic granite containing two rectangular holes with different axial static pre-stresses by a modified split Hopkinson pressure bar (SHPB), and uniaxial compression tests were also carried out for comparison. Combined with digital image correlation (DIC), the dynamic damage and fracture process of specimens were observed by low-speed and high-speed cameras. Moreover, the energy evolution characteristics of specimens were analyzed to further understand the failure mechanism. The results indicate that the pre-stress has dual effects on the dynamic mechanical behavior of rock specimens, and the transition mechanism of the effect of pre-stress can be revealed by the elastic deformation limit. Observations show that the failure of specimens under different loads is caused by the growth of secondary cracks at hole corners. However, with the increase in pre-stress, the crack mode tends to shear and the strain localization tends to concentrate on sidewalls, resulting in severe rock bursting and extensive fracturing. Four coalescence modes around two rectangular holes were summarized: diagonal shear coalescence under static load, no coalescence under dynamic load, shear coalescence inside the middle rock bridge area under the pre-stress of 25–55% UCS, and indirect coalescence outside the rock bridge area under the pre-stress of 75% UCS. The specimen with the pre-stress of 75% UCS releases the internal strain energy during dynamic failure process, while the specimen with lower pre-stress absorbs the external impact energy. Finally, some insights are provided for deep rock engineering based on the test results.
35 citations
TL;DR: The validity and convergence of the proposed algorithm is proved by strict mathematical theory and numerical results of engineering example, and the dynamic load identification of uncertain structures can be transformed into a series of deterministic inverse problems by the matrix perturbation method.
33 citations
TL;DR: A novel and efficient method utilizing blind source separation and orthogonal matching pursuit is proposed in this paper to identify the time-space coupled distributed dynamic loads.
33 citations
TL;DR: In this article, a numerical model based on refined plate theory (RPT), modified couple stress theory (MCST) and NURBS-based isogeometric analysis (IGA) is introduced to predict the complex behaviors of small-scale structures.
32 citations
TL;DR: The Fuzzy-PID provides a capability to enhance dynamic performance and system power quality because achieve less fluctuation and more smoothing for signals makes it is superior for voltage control for AC-DC micro-grid.
Abstract: Voltage stability and power quality play very effective issues in power systems. This paper aims to improve the voltage stability and enhance system power quality in the AC-DC micro-grid system based on intelligent fuzzy controllers. These controllers are fuzzy-PI (FPI) and fuzzy-PID (FPID) current-controller with the existence of distribution static synchronous compensator (D-STATCOM). The capability of proposed system has been applied in two case studies that emulate abrupt fault and dynamic load changes on AC-DC hybrid micro-grid that collects different types of renewable energy sources. In addition to, the proposed fuzzy-based controllers produce the optimum dynamic response and resolve the power quality issues. Numerical simulations associated with detailed comparisons between different controllers are provided. It was found that when the studied system is subjected to a 3-phase fault, the voltage fluctuation at the D-STATCOM is reduced by 7.86% and 4.62% and the dynamic system performance is improved by 12.9% and 8.8% with using Fuzzy-PID and fuzzy-PI, respectively. Also with the dynamic load changes, the fluctuation of system voltages at the D-STATCOM is reduced by 0.982% and 0.577 % and the dynamic system performance is improved with 6.67%, 5.71% when comparing Fuzzy-PID controller and Fuzzy-PI to the uncontrolled system. The Fuzzy-PID provides a capability to enhance dynamic performance and system power quality because achieve less fluctuation and more smoothing for signals makes it is superior for voltage control for AC-DC micro-grid.
32 citations
TL;DR: The result shows that the ring gear crack fault can rarely affect the dynamic load sharing among the external meshing gear pairs, and can help better understand the internal laws of crack fault for planetary gear set.
32 citations
02 Mar 2021
TL;DR: In this paper, the influence of thermal conductivity on the dynamics of a rotating nanobeam is established in the context of nonlocal thermoelasticity theory and the governing equations are derived using generalized heat conduction including phase lags on the basis of the Euler-Bernoulli beam theory.
Abstract: In this article, the influence of thermal conductivity on the dynamics of a rotating nanobeam is established in the context of nonlocal thermoelasticity theory. To this end, the governing equations are derived using generalized heat conduction including phase lags on the basis of the Euler–Bernoulli beam theory. The thermal conductivity of the proposed model linearly changes with temperature and the considered nanobeam is excited with a variable harmonic heat source and exposed to a time-dependent load with exponential decay. The analytic solutions for bending moment, deflection and temperature of rotating nonlocal nanobeams are achieved by means of the Laplace transform procedure. A qualitative study is conducted to justify the soundness of the present analysis while the impact of nonlocal parameter and varying heat source are discussed in detail. It also shows the way in which the variations of physical properties due to temperature changes affect the static and dynamic behavior of rotating nanobeams. It is found that the physical fields strongly depend on the nonlocal parameter, the change of the thermal conductivity, rotation speed and the mechanical loads and, therefore, it is not possible to neglect their effects on the manufacturing process of precise/intelligent machines and devices.
32 citations
TL;DR: In this paper, the effect of infilling on mechanical response and crack behavior of pre-stressed rock with double rectangular holes under dynamic load was investigated through a series of coupled static-dynamic loading tests on diorite specimens in three different filling states, i.e., no infilling, single infilling and double infilling.
Abstract: The effect of infilling on mechanical response and crack behavior of pre-stressed rock with double rectangular holes under dynamic load was investigated through a series of coupled static–dynamic loading tests on diorite specimens in three different filling states, i.e., no infilling, single infilling and double infilling, using a modified split Hopkinson pressure bar. The deformation, damage and fracture process of specimens were recorded and analyzed by low-speed and high-speed cameras with digital image correlation method. Test results reveal that under the same dynamic load, the strength of specimens increases first and then decreases with the increase of axial static pre-stress, and reaches the maximum under 25% UCS due to crack closure. The strengthening effect of double infilling on strength is much more significant than that of single infilling and increases with the pre-stress. Observations show that with the increase of pre-stress, the degrees of damage and strain localization of specimens increase, and the superficial damage on the free surface of sidewalls are more severe. The effect of infilling is significant on the crack initiation and propagation, especially on the inhibition of sidewall spalling, rock ejection and the axial displacement failure of rock septum between holes. With the increase of pre-stress, the failure pattern and the crack coalescence mode change from obvious tensile to shear, and the coalescence position changes from the inside to outside of the septum area. However, the change of filling state has little effect on the coalescence mode, only on the coalescence position.
28 citations
TL;DR: A support vector regression (SVR)-based method is presented, which aims to reconstruct the uncertain dynamic load using heterogeneous responses, and results indicate that the proposed method can be utilized to identify the interval of dynamic load with outstanding accuracy and efficiency.
TL;DR: This paper tries to provide a comprehensive review of techniques for dynamic load identification, including under ill-posedness and uncertain parameter processing; with an emphasis on the statistical, data science, machine learning, and artificial intelligence aspects.
Abstract: Due to the great challenges of measuring forces directly, identifying dynamic loads based on accessible responses is a crucial problem in engineering, helping ensure integrity and reliability of mechanical structures. Dynamic load identification is a difficult inverse problem due to matrix ill-posedness, noise-sensitivity and computational scale, especially in uncertain structures. Unexpected inaccurate or non-unique solutions may be found if these problems are not well addressed. During the past decades, many methods have been proposed to deal with these problems. This paper tries to provide a comprehensive review of techniques for dynamic load identification, including under ill-posedness and uncertain parameter processing; with an emphasis on the statistical, data science, machine learning, and artificial intelligence aspects. Classical physics-based dynamic load identification theories in frequency and time domain are also introduced. Research challenges and prospects of dynamic load identification in mechanical systems are discussed finally. This review may offer guidelines for dynamic load identification in practical complex structures, as well as possibilities for further researches. Some methods could have broader applicability to other inverse problems.
01 Apr 2021
TL;DR: The simulation and experimental results show that the safety warning of the cylindrical lithium-ion battery based on mechanical penetration has a certain safety margin, which can provide valuable reference for the battery safety under mechanical abuse in the future.
TL;DR: In this article, a combined dynamic compression-shear test was performed on inclined cylindrical sandstone specimens with hydrostatic confining pressures and showed that the shear component in the dynamic load limits the dynamic peak stress of rocks.
Abstract: Rocks in the deep underground are likely subjected to both hydrostatic confining pressure and dynamic compression–shear load. Thus, accurately characterizing the dynamic properties and failure mechanism of hydrostatically confined rocks under combined compression–shear impacting is crucial for the stability assessment of deep underground rock structures. In this study, on the basis of an improved split Hopkinson pressure bar (SHPB) apparatus, the combined dynamic compression–shear tests are performed on inclined cylindrical sandstone specimens with hydrostatic confining pressures. During the test, the dynamic force balance of rock specimens can be well satisfied using the pulse shaping technique. Our results show that the hydrostatic confining pressure and dynamic loading rate help strengthen the load-carrying capacity of rocks. In contrast, the shear component in the dynamic load limits the dynamic peak stress of rocks. As hydrostatic confining pressure increases, the failure surface based on the Drucker–Prager criterion gradually expands outward. Under dynamic loading, the compressive deformation modulus of rocks decreases with increasing shear component in the dynamic load, contrary to its response to hydrostatic confining pressure. Fragmentation analysis indicates that the hydrostatic confining pressure and the shear component of dynamic loading restrict the fracture behavior of rocks. Besides, as the specimen inclination angle and the hydrostatic confining pressure increase, the failure pattern of rock specimens changes from the tensile-dominated failure with a truncated conical surface to the shear-dominated failure with a single shear plane along its short diagonal.
TL;DR: In this article, a vehicle-ballastless track coupled model with consideration of concrete cracks in high-speed railways through finite element method was proposed, and an iterative method is proposed to estimate the fatigue crack growth of concrete under long-term train dynamic load on the basis of the Forman model.
TL;DR: In this article, Nanosecond pulsed laser was used to create texture (involving micro-dimples having different dimple area density) on the inner race of test bearings.
Abstract: In case of lightly loaded radial ball bearings, failure mechanisms other than fatigue such as smearing of raceways due to increased frictional torque and vibrations often prevail. Hence, attempts have been made herein for reducing the frictional torque and minimizing the vibrations of a radial deep groove ball bearing employing surface textures at the inner race. Nanosecond pulsed laser was used to create texture (involving micro-dimples having different dimple area density) on the inner race of test bearings. Using an in-house developed test rig, frictional torque and vibrational parameters were measured at different speeds and light loads (i.e. in vicinity of 0.01C, where C is dynamic load capacity of radial ball bearing). Significant reduction in frictional torque and overall vibrations were found in the presence of micro-dimples on inner race at light loads irrespective of operating speeds. Even without satisfying the minimum load needed criteria for the satisfactory operation, substantial reduction in smearing marks was found on the races of textured ball bearings in comparison to conventional cases.
TL;DR: In this article, a new lattice structure, drawing on inspiration from nature, was developed and manufactured via selective laser melting (SLM) to explore the effects of printing parameters on densification and mechanical performance.
TL;DR: In this article, an experimental system was developed to investigate the load distribution in a cylindrical roller bearing and the experimental static load distribution agreed well with the theoretical calculation, while the dynamic load at specific position of load zone reflects the manufacture difference among rollers and dynamic balance of distributing loads.
TL;DR: In this paper, the authors analyzed the thermo-elastic dynamic behavior of simply supported viscoelastic nanobeams of fractional derivative type due to a dynamic strength load.
Abstract: This paper analyzes the thermoelastic dynamic behavior of simply supported viscoelastic nanobeams of fractional derivative type due to a dynamic strength load. The viscoelastic Kelvin–Voigt model w...
TL;DR: A novel time-domain algorithm based on the Newmark-β method, which is first attempt to solve the problems of dynamic load identification for continuous systems, and is effective and robust against noises as well.
TL;DR: In this paper, the authors investigated the efficacy of using an innovative hybrid strengthening technique composed of near-surface mounted (NSM) steel rebars along with fiber reinforced polymer (FRP) sheets to prevent or diminish the risk of progressive collapse in precast reinforced concrete (RC) beam-column joints.
01 Mar 2021
TL;DR: In this paper, a process to quantify the impact of truck suspension systems and road surface condition on the damage exerted to the pavement is presented, where the International Roughness Index (IRI) was used to simulate the road roughness.
Abstract: Several mechanistic-empirical software packages have been developed in the last two decades to address the impact of axle load and axle configuration on pavement responses and their performance. These software packages generally do not consider the vehicle pavement interaction. The interaction of truck suspension system with the roughness of the road surface may exert additional forces to the pavement. A process to quantify the impact of truck suspension systems and road surface condition on the damage exerted to the pavement is presented in this paper. The International Roughness Index (IRI) was used to simulate the road roughness. The truck-pavement interaction was then modeled to estimate the dynamic load applied to the pavement. The process followed to develop the algorithms is discussed, followed by a parametric study to demonstrate the interaction among the suspension properties, road roughness and vehicle speed. The impact of dynamic load on the pavement distresses and the progress of deterioration is also discussed.
TL;DR: The buckling analysis of rectangular sandwich plates with pure polymeric tapered cores and functionally graded carbon nanotube (FG-CNT) reinforced composite face sheets under static and harmonic dynamic loads is presented in this article.
TL;DR: A three-dimensional dynamic load distribution model of planetary gear sets, which can capture the influence of several component and system level design variations and the unique dynamic response of the parametrically excited system under various gear mesh phasing conditions is studied.
TL;DR: In this paper, the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations, and the deformation and failure characteristics are obtained.
Abstract: In actual production, deep coal mine roadways are often under typical static-dynamic coupling stress (SDCS) conditions with high ground stress and strong dynamic disturbances. With the increasing number of disasters and accidents induced by SDCS conditions, the safe and efficient production of coal mines is seriously threatened. Therefore, it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS. In this paper, the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations, and the deformation and failure characteristics are obtained. According to the simulation results, the horizontal stress, vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock. Among these factors, the influence of the dynamic disturbance is the most substantial. Under the same stress conditions, the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor. The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses. The results indicate that for the roadway under high-stress conditions, the in-situ stress test must be strengthened first. After determining the magnitude of the in-situ stress, the location of the roadway should be reasonably arranged in the design to optimize the mining sequence. For roadways that are strongly disturbed by dynamic loads, rock supports (rebar/cable bolts, steel set etc.) that are capable of maintaining their effectiveness without failure after certain dynamic loads are required. The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS, and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.
TL;DR: This paper presents a multi-objective multi-verse optimization scheme to minimize the dynamic economic load dispatch issue using valve-point effects and proves the effectiveness of solving various dynamic economical load dispatch problems depending on the numerical outcomes.
Abstract: In power system operation, optimal economic dispatch is imposed by the costs of increasing power generation, the increasing demand for electrical energy and the scarcity of energy resources. By satisfying all constraints, the most important thing is the economical load distribution in order to enable the generators used in the system to generate optimal power. The non-smooth cost function and emission with nonlinear constraints are the practical economic load dispatch issues that create a challenge that is effectively reduced. This paper presents a multi-objective multi-verse optimization scheme to minimize the dynamic economic load dispatch issue using valve-point effects. Along with all other necessary constraints, this algorithm preserves the ramp of unit required rate constraint. However, it maintains these limitations via the transaction duration to the next time horizon to eliminate the power system operation’s discontinuity, not only for its time horizon. The objective of this method is by satisfying various operational constraints and the power generator has the load requirement along with the minimization of cost. The proposed algorithm is tested on two test systems by varying the generating units as 40, 80, and 160. Simulation results are performed under the MATLAB environment and, the acquired results are compared with many existing algorithms in terms of fuel cost, emission cost, and robustness. The proposed scheme is very encouraging and proves the effectiveness of solving various dynamic economical load dispatch problems depending on the numerical outcomes.
TL;DR: In this article, the response of pre-stressed anchored excavation walls under dynamic and pseudo-static loadings was investigated using FLAC 2D, and the results were successfully validated against full-scale experimental data.
Abstract: This study investigates the response of pre-stressed anchored excavation walls under dynamic and pseudo-static loadings. A finite difference numerical model was developed using FLAC 2D , and the results were successfully validated against full-scale experimental data. Analyses were performed on 10, and 20-m-height stabilized excavated slopes with 60° to 90° of inclination angle with the horizon to represent an applicable variety of wall geometries. In dynamic analysis, the statically stabilized models were subjected to 0.2 to 0.6g of the dynamic peak acceleration to evaluate the effect of ground acceleration on their performance. Furthermore, pseudo-static analyses were performed on the statically stabilized models with pseudo-static coefficients ranging from 0.06 to 0.22. The results revealed that ground anchored slopes generally showed acceptable performances under dynamic loading, while higher axial forces were induced to ground anchors in higher and steeper models. Furthermore, comparing the results of dynamic and pseudo-static analyses showed a good agreement between the two methods' predictions in the mobilized axial force along the ground anchors. Pseudo-static coefficients were then proposed to replicate dynamic results, considering the slope geometry and dynamic load peak acceleration. The results revealed that higher and steeper stabilized slopes required higher values of pseudo-static coefficients to match the dynamic predictions successfully. The results indicate that pseudo-static coefficient tend to increase with the increase in dynamic load peak acceleration in any given model. Doi: 10.28991/cej-2021-03091703 Full Text: PDF
TL;DR: In this article, an active magnetic bearing (AMB) with power electronic control for high-speed machinery, which are termed active magnetic bearings (AMBs), is presented, which is a contactless-type bearing, which uses magnetic force to support the rotor.
Abstract: This article reviews electromagnetic bearings with power electronic control for high-speed machinery, which are termed active magnetic bearings (AMBs). AMB is a contactless-type bearing, which uses magnetic force to support the rotor. This is suitable for high-speed applications, harsh operating conditions, and also clean environments. However, the AMB has nonlinear characteristics and is inherently unstable. Due to recent advancements in fast-switching power devices, high-switching-frequency power converters, high-bandwidth current control, nonlinear control strategies, advanced digital controllers, and sensors, AMBs have become promising for high-speed aerospace, industrial, and energy applications. This article contains a brief tutorial on the AMB, covering its operating principle, system-level block diagram, magnetic-circuit-based analysis, dynamic load due to rotor mass unbalance, load capacity, force slew rate, and response to large force disturbance. Furthermore, a design example of an eight-pole AMB with four excitation coils is presented to achieve a load capacity of 180 N. A preliminary design, based on magnetic circuit analysis, is seen to fall short in terms of load capacity. Iterative changes to the AMB dimensions achieve the required load capacity, but the characteristics are still nonlinear. Finite-element analyses bring out the effects of magnetic saturation on load capacity, linearity between force and current, force slew rate, and relationships between maximum force generated and AMB dimensions. An improved design procedure is presented to achieve both desired load capacity and linear characteristics, while balancing the compactness requirement. The improved design also achieves the desired slew rate besides faster response and improved stability.
TL;DR: In this paper, the mixed finite element method (FEM) was developed from the variational formulation of flexoelectric boundary value problems for general 2D boundary value problem with cracks under a dynamic load.