Effect Of Dynamic Loading Research Articles

Strain rate effects on the crack propagation speed under different loading modes (I, II and I/II): Experimental investigations

Studying rock behavior under the effect of dynamic loads is one of the practical issues in engineering projects that has been considered by many researchers in last decades. Experimental measure of crack propagation speed under three loading modes (mode I, mixed mode I/II and mode II) and under a quasi-static and dynamic strain rate is still a big challenge due to the difficulties associated with measuring this parameter. Taking into account the high strength of hornfels rock and its extensive applications in the scientific and practical life, series tests were conducted on rectangular specimens of this rock type under a quasi-static and dynamic strain rate by using a servo hydraulic machine and drop weight machine, respectively. A special electric circuit was designed in this study to investigate the effect of the loading mode and strain rate on the crack propagation speed. Crack propagation speed was measured under six strain rates (6 × 10-4, 6 × 10-3, 6 × 10-2, 1.9 × 10+1, 3.8 × 10+1 and 5.6 × 10+1 S-1) and under three loading modes. The results showed that the crack propagation speed depends on the loading mode and strain rate. By increasing the strain rate from 6 × 10-4 to 5.6 × 10+1 S-1, the average crack propagation speed under pure mode I, mixed mode loading I/II and pure mode II increases by 12, 4.6 and 4.1 times, respectively. The crack propagation speed under pure mode I and mixed mode loading I/II almost has the same increment rate. But the increment rate of the crack propagation speed under pure mode II is slightly larger. For pure mode I, no significant changes were observed on the crack propagation path by increasing the strain rate. For mixed mode I/II and pure mode II, the crack propagation path under a quasi-static strain rate was a traditional concave-up path. While under a dynamic strain rate, the crack tended to grow through a straight or slightly concave-down path.

Effect of dynamic loading on fracture resistance of gradient zirconia fixed partial denture frameworks

Statement of problemThe new strength-gradient zirconia composed of 3-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 5-mol% yttria-stabilized tetragonal zirconia polycrystal (5Y-TZP) has been claimed to have superior mechanical properties. However, data on the fracture resistance of 3-unit gradient 5Y-TZP and 3Y-TZP fixed partial denture frameworks are lacking. PurposeThe purpose of this in vitro study was to evaluate the effect of dynamic loading on the fracture resistance of gradient zirconia fixed partial denture frameworks. Material and methodsTwo standardized stainless-steel master dies were designed to simulate a mandibular left second premolar and second molar prepared to receive zirconia frameworks. The frameworks were designed with a 0.6-mm uniform wall thickness. The mesiodistal width of the connectors was 3 ±0.02 mm, and the occlusogingival height was 3 ±0.02 mm. Forty zirconia frameworks were fabricated and divided into 2 groups according to the tested materials (n=20): 3Y-TZP and gradient 5Y-TZP and 3Y-TZP. The frameworks were cemented onto their corresponding dies with a conventional glass ionomer cement. Half of the cemented frameworks in each group underwent 600 000 cycles of dynamic loading in a mastication simulator (n=10). The other half was fractured without dynamic loading (n=10). Fracture resistance measurements (N) for each framework were recorded by using a universal testing machine at a crosshead speed of 1 mm/min. A fractured framework from each group was examined by using a scanning electron microscope (SEM) at ×100 magnification. The data obtained were statistically analyzed by using 2-way ANOVA, the pairwise Tukey honestly significant difference (HSD), and simple main effect tests to detect the difference between group mean values (α=.05). ResultsThe mean ±standard deviation of fracture load value before dynamic loading was 1919 ±193 N for the 3Y-TZP group and 908 ±99 N for the gradient 5Y-TZP and 3Y-TZP group. In addition, the mean fracture load value after dynamic loading was 1418 ±163 N for the 3Y-TZP group and 716 ±85 N for the gradient 5Y-TZP and 3Y-TZP group. The interaction between the effects of the zirconia material and dynamic loading on the fracture resistance was statistically significant (P=.002). The 3Y-TZP group had a statistically significant, higher fracture load mean value the gradient 5Y-TZP and 3Y-TZP group before and after dynamic loading (P<.001). ConclusionsThe fracture resistance of 3Y-TZP frameworks was significantly higher than that of gradient 5Y-TZP and 3Y-TZP frameworks before and after dynamic loading. Dynamic loading significantly reduced the fracture resistance of 3Y-TZP and gradient 5Y-TZP and 3Y-TZP frameworks.

Characterizing the permanent deformation Response-Behavior of subgrade material under cyclic loading based on the shakedown theory

Coarse-grained soil is widely used as a filling material in the railway subgrade to provide foundational support to the long-term effects of dynamic (cyclic) train loads transmitted by the track structure. Despite this wide usage, there is limited literature on its permanent deformation behavior characterization under different magnitudes of dynamic stress. The GDS (Geotechnical Digital System) dynamic triaxial tests were presented in this paper to characterize and quantify the dynamic response-behavior of coarse-grained railway subgrade soils when subjected to dynamic loading. Based on the shakedown concept, the patterns of accumulated axial plastic strains for the coarse-grained soil under different magnitudes of dynamic stress were classified into three categories, namely plastic shakedown, plastic creep, and incremental collapse. As a result, the critical dynamic stresses for plastic shakedown and plastic creep state could easily be determined. The experimental test results indicated that whilst the critical dynamic stress of the coarse-grained soil increased with an increase in the effective confining pressure, it correspondingly decreased as the loading frequency increased from 1.0 to 3.6 Hz, respectively. From the regression fitting-analysis of the experimental test results, an empirical model is proposed in this paper, which denotes the critical dynamic stress of coarse-grained subgrade soils as a function of the effective confining pressure. As a contribution to the literature and potential engineering applications, the proposed models may provide theoretical significance for the subgrade state evaluation and settlement control.

Jet impingement in high-energy piping systems, part II: Model improvement and guidance development

The Standard model in ANSI/ANS-58.2 (1988) has been widely employed in the design and safety analysis of nuclear power plants for jet impingement under postulated pipe rupture accidents. However, the potential non-conservatisms presented in Standard Review Plan (2015) need to be addressed when evaluating this model. The current work aims to improve the model on jet prediction including jet geometry and stagnation pressure, as well as to address the potential non-conservatisms. Based on the model evaluation results in Part I, new correlations for the jet core length and stagnation pressure in subcooled water and saturated water/two-phase jets are implemented to replace the existing correlations in the Standard model. It is shown that the revised code with the newly developed correlations predicts the stagnation pressure generally higher or conservatively for all conditions investigated.On the potential blast wave effect, the current work develops an approach to quantify the over-static and reflected pressures using the equivalent weight of TNT approach in literature. To employ this approach, the released energy in the equivalent of TNT needs to be determined from jet impingement. This energy is calculated using the vessel burst energy concept with conservative assumptions in the current work. For jet geometry, dynamic models to predict the jet spreading angle for saturated steam jets are compared with the Prandtl-Meyer angle for under-expanded supersonic jets. It is found that the jet spreading angle for saturated steam jets in the Standard model generally agrees with the dynamic model in literature for a wide range of initial vessel stagnation pressure conditions. Regarding the pressure distribution within jets, it is confirmed that edge-peaking pressure profiles can be observed for saturated steam jets at far distances from the break plane (z > 3.3 D); however, the dimensionless pressures at these locations are generally less than 0.07. Regarding the jet dynamic loading effect, the literature review suggests that dynamic amplification and resonance of impinged downstream structures and components might not occur for jet impingement in nuclear power plants.

Effects of Dynamic Loading under Extreme Conditions on Wear Resistance of T105Mn120 Castings for Railway Safety Systems

Effects of Dynamic Loading under Extreme Conditions on Wear Resistance of T105Mn120 Castings for Railway Safety Systems

Effective stiffness and period-dependent seismic response modification factors for flexure-dominated fully-grouted reinforced masonry rectangular shear walls

The wall effective elastic stiffness, displacement ductility, and seismic force modification factors are important force-based seismic design (FBD) parameters for reinforced masonry (RM) shear walls. The effective stiffness, ke of reinforced masonry shear walls (RMSW) is crucial in computing the natural period and thus the elastic forces, and essential also in computing the displacements corresponding to the design seismic forces. This study analyzes previously reported test results of forty-three flexure-dominated fully-grouted rectangular RMSWs subjected to quasi-static cyclic load to evaluate the FBD parameters adopted by Canadian and American standards. In this study, based on the experimental results of 43 tested walls, a new stiffness reduction factor is proposed considering the effect of axial stress, vertical reinforcement ratio, and horizontal reinforcement ratio. Moreover, the seismic force modification factors are compared to the Canadian and US codes. The results showed that ductility related reduction factors should be dependent on the wall natural frequency and there is a room to relax the current proposed code values. In addition, incremental dynamic analysis was performed using a simplified numerical model to study the effect of dynamic loading on response modification factors and stiffness characteristics of the walls.

Strength and structural variations in dredger fill subjected to vacuum dynamic consolidation

Laboratory vacuum dynamic consolidation tests were performed to study the effect of dynamic impact loads on the shear strength characteristics of dredger fill. The results revealed that the shear strength increased with the increase in the number of blows. The relationship between the increase in the shear strength and the soil structure was analyzed through scanning electron microscopy and mercury intrusion porosimetry. The structure collapsed progressively and the larger inter-aggregate pores were affected the most. Considering pore evolution, the pore size distribution was primarily unimodal, and the variations in porosity and shear strength with the blow count were the same. Thus, the shear strength of dredger fill is influenced by its structure. On average, five blows ensure high compaction efficiency.

Investigation of impact behavior of reinforced concrete beam to column connection strengthened with carbon fiber‐reinforced polymer strips

AbstractReinforced concrete (RC) members may expose to impulsive dynamic loads due to the reasons such as the explosions occurring in the interior or exterior part of them, rockfall, the vehicle crash to the bridges, the collision of masses with the effects of floods and landslide. Many studies have investigated the effects of impulsive dynamic loads on the beam, column, and slab RC structural elements have been investigated in the literature. However, the authors have not encountered any study focused on the impact behavior of beam to column connections of the frames constructing the bearing system of reinforced concrete structures. Therefore, an experimental study has been planned to investigate RC beam impact behavior to column connections strengthened with carbon fiber‐reinforced polymer (CFRP) strips. The concrete compressive strength, shear reinforcement spacing, CFRP strip spacing, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, displacements, and the strains measured from CFRP strips have been recorded in experiments. The experimental variables' effect on dynamic responses of RC beam to column connections strengthened with CFRP strips subjected to impact load has been interpreted in detail. The study's scope and improved numerical analysis procedure have also been introduced to verify experimental results. Good agreement between numerical and experimental results demonstrated that the presented numerical procedures could be safely used for evaluation of impact behavior of RC beam to column connections strengthened with CFRP strips.

Static and Dynamic Analysis of Seasonal Tilt Solar Module Mounting Structure

This paper highlights the concept of a ground-mounted solar PV plant. It deals with the ground-mounted solar photovoltaic design, and development using numerical analysis under static and dynamic conditions. Ground-mounted solar components are made up of steel shows superior performance and is cost-effective. CFD analysis is executed on the structure of the study for flow and assessment of wind pressure on the developed model using Indian environmental conditions. The CFD results have been compared and validated h the analytical calculations obtained through IS 875 codes part 3 for wind pressure. Structural FE analysis is carried out to ensure structural stability for the given hazardous environmental conditions like wind load. Also, modal analysis is carried out to study the effect of dynamic loading.

Silos structural response to blast loading

Extensive research work has been conducted to study the structural behavior of silos for various static load types; namely the grain load compression phases inside the silos and the thermal loads. However, very few investigations were related to the effect of different dynamic loads on silos, especially shock and blast loads. The aim of this research is to evaluate the structural response of grain silos due to massive blast loads. The Beirut explosion that occurred on August 04, 2020 is considered as a case study in a structural engineering approach with numerical non-linear finite element modeling of the silos. Due to the uncertainty of the exploded material mass, the magnitude of the explosion is defined as the numerical model magnitude that generates the same silos damages and sways recorded on site. The numerical study models are based on silos data (geometrical and material properties), and the use of the Conventional Weapons Effects Blast Loading (CONWEP), and the Coupled Eulerian-Lagrangian (CEL) methods to generate the blast loads. In addition, damage for the standing silos has been assessed, and final recommendations were stated. The results of this study define the magnitude of the explosion and the structural state of the remaining silos.

Settlement Analysis of machine foundation Under Reciprocating Load using FEM

The analysis of the machines foundations is an important issue in the geotechnical engineering as the foundations of the machine provide a strong platform for the machines to work in a smooth manner with minimal maintenance requirements. The process of analyzing of the machines foundations requires more attention since it includes not only the static loads but also the dynamic loads that result from the unbalanced forces that the machine generates or its vibratory motion. Of course, this movement load is transferred to the soil through the foundation and its effect can be calculated using the principles of kinetic soil and vibration theory. Here, the search deals with the study of analyzing machines foundations under the influence of kinetic loads taking into consideration the type of soil and its condition, the shape of the foundation and its location from the surface of the earth, the type of kinetic load projected and the method of analysis. In this study, and for the purpose of achieving what has been mentioned with using finite element method (program Plaxis 2D V8.6 ) three types of sandy soil (Loose, medium and dense) were taken. The effect of dynamic loads on different types of machine foundations (square, rectangular, and strip) was studied and under the influence of a different dynamic frequency (5,10,15, 20 Hz) was studied and the effect of a group of these factors on the amount of displacement of the machine foundation was studied and these results were compared with the maximum Amplitude when resonating with a special parameter called Normalized Displacement. It is noted from this study that the value of the displacement decreases by increasing the values of the (L / B) ratio of the foundation for the same frequency for the three soil states, , and that the increase the value of the elastic modulus (E), the Normalized displacement value approaches the number (1), that meaning it approaches the resonance at the frequency ( 5 Hz) for the case of the square foundation more than the rectangle and the strip , and for the remaind of the frequencies (10, 15, 20 Hz) the Normalized displacement value will be less compared to the frequency (5 Hz) as well as less variation between the cases of different foundations shape.

Effect of dynamic loads and vibrations on lithium-ion batteries

Lithium-ion batteries are being increasingly used as the main energy storage devices in modern mobile applications, including modern spacecrafts, satellites, and electric vehicles, in which consistent and severe vibrations exist. As the lithium-ion battery market share grows, so must our understanding of the effect of mechanical vibrations and shocks on the electrical performance and mechanical properties of such batteries. Only a few recent studies investigated the effect of vibrations on the degradation and fatigue of battery cell materials as well as the effect of vibrations on the battery pack structure. This review focused on the recent progress in determining the effect of dynamic loads and vibrations on lithium-ion batteries to advance the understanding of lithium-ion battery systems. Theoretical, computational, and experimental studies conducted in both academia and industry in the past few years are reviewed herein. Although the effect of dynamic loads and random vibrations on the mechanical behavior of battery pack structures has been investigated and the correlation between vibration and the battery cell electrical performance has been determined to support the development of more robust electrical systems, it is still necessary to clarify the mechanical degradation mechanisms that affect the electrical performance and safety of battery cells.

Анализ влияния упругих свойств дейдвудных подшипников на рабочее состояние судового валопровода

The paper considers the ship shafting and its design. Depending on the constructive features, operating conditions, effects of continuous, dynamic, variable and random loads the operation of the shaft line is accompanied by wear of the shafting structure and auxiliary parts. The formulas for calculating the maximum permissible clearances during operation in stern bearings of propeller shafts are given, according to the norms and technical and operational requirements. A graph of the maximum permissible clearances in metal stern bearings is presented. There has been carried out a dynamic design of the shaft line in order to define the influence of rigid characteristics of the stern bearings on eigen frequency of transverse vibrations. It is noted that the service life of the shaft line depends on the material of bushings or liners of the bearings (bakout, babbit, textolite, caprolon, bronze, polyurethanes, rubber) and their wear degree. The design scheme of the ship shaft line on elastic supports with a coefficient of rigidity is presented. To assess the influence of the elastic properties of deadwood bearings, the method of initial parameters was used. According to the researchers’ opinion, the greater the wear, the lower their stiffness coefficient. At a certain wear degree of deadwood bearings, there occurs resonance at the lowest operating frequencies. It has been proved that the greater the deflection at the attachment point of the propeller, the lower the eigen frequency of transverse vibrations of the shaft line. It has been pointed out that the calculations should include the separation of the shaft line from the deadwood bearing, since it contributes to a decrease in eigen frequency and causes a resonance during transverse vibrations.

Dynamic evaluation of jack-up platform structure under wave, wind, earthquake and tsunami loads

Nowadays, the demand for using jack-up platforms to carry out a large percentage of deep-water oil and gas exploration is steadily increasing. The response of jack-up platforms to the severe dynamic loads that may be encountered during the structure life is not examined enough. Therefore, this study attempts to investigate the response of jack-up platforms performance under the effect of dynamic loads due to wave, wind, earthquake and tsunami forces using the finite element method for two models with the lowest and highest hull elevations. The jack-up platform is located in the Gulf of Mexico. Earthquake accelerations are applied to the model in high and moderate seismic levels. In addition, tsunami waves are applied to the platform in three different directions at 0°, 45° and 90°. This study utilised Airy's linear wave approach to assess the surface elevations and wave kinematics. The reference wind velocity is 10 knots at 10 m over the mean water level. Results indicate that the dynamic response of the structure is affected by the height of the platform and by the increase of the platform hull elevation. The combination of the El-Centro earthquake, dead and live loads provides the major impact on the platform at the lowest (70 m) and highest (85 m) hull elevations. The comparison of all result proves that the jack-up platform hull under high earthquake intensity and tsunami waves with 45° has experienced maximum deformation. Moreover, raising the deck will increase the response of the dynamic load and displacements but will negatively affect the platform.

Stability Analysis and Fracture Patterns of Hard Main Roof in Longwall Top Coal Caving with Large Mining Height

In order to study the fracture patterns of hard main roof in longwall top coal caving (LTCC) with large mining height, a two-dimensional physical similarity model was created to simulate the mining process of No. 8100 large mining height face in Tongxin coal mine, China. The results show that there are three positions of broken line in hard main roof presented with the advance of longwall face, and the underground pressure induced by hard main roof fracturing presents the effect of superposition of large and small periods. It is found that there are two fracture patterns of main roof during the mining process: composite structure of lower cantilever beam and upper voussoir beam with hard main roof and composite structure instability of lower and upper voussoir beam with hard main roof. The underground pressure induced by these two fracture patterns is also analyzed by building mechanical models. In the end, the hydraulic fracture technique is introduced to presplit the main roof and weaken the effect of dynamic loads induced by composite structures instability.

Experimental studies of the effect of concentrated dynamic loads on a three-layer structure with a filler

The results of experimental studies of the effect of concentrated dynamic loads on a three-layer structure with glass fiber filler are presented. A comparative analysis of the obtained results with theoretical data is carried out. Keywords: three-layer structure, striker, bearing layer, fiberglass, impact loading. hairulla213@mail.ru

A Comparative Experimental Study on The Human and Artificial Hip Joint:Stress Analysis with Static Load Time and Impact Load.(Dept.M)

Although the understanding of the mechanical properties and fracture behaviour of bone is continuously improving, as yet it's far from complete. So, this paper represents an experimental study about the effect of static and dynamic loads under different parameters on intact bone and human hip joints. The same test will be applied on the human hip joints after insertion of the artificial femur component in the bone. A special test-rig was designed in order to fix both natural and artificial implant and expose them to a state of loading similar in magnitude and direction to that encountered in the human-being.A comparison between the stress-strain distribution of the intact and artificially implanted bones were conducted by using strain gauges. The results showed that the stresses were reversed after insertion of the artificial femoral component and the stresses were maximum at the near of the tip of the prothesis. Also, the absence of the collar-calcar causes a severe reduction of the stresses which may be due to important metabolic changes.

Linear Transient Dynamic Analysis of Plates With and Without Cutout

The present work exhibits the analysis of a plate with and without cutout considering the dynamic analysis in a transient zone with its application in the civil, structural, and aerospace industry. For this, first-order shear deformable C0 continuous Finite Element (FE) is implemented to examine transient response of plate. The governing ODE of motion’s is integrated using central difference explicit time integration scheme. A lumped mass matrix is obtained by a special diagonlization scheme and the total mass of the element is conserved by inducing effective rotary inertia terms. A FE program is developed based on derived FE formulation to investigate the effect of dynamic loading on such plates. The analysis exhibits the results in terms of displacement, forces, and bending moment of the plate for various aspect ratios and different parameters. The results are shown in terms of tables and graphs for smaller to larger cutout in plates with its different aspect ratio considering transient analysis. The results reveal that transient dynamics analysis shows a considerable difference in the behavior of plates with and without cutout in terms of time period, amplitude, and bending moment than that obtained from static analysis.

Three-Dimensional Non-Linear Analysis based on the Temporal Evolution of an RCC Dam Including the Alluvium Effect

This article discusses the seismic response of roller-compacted concrete dams by interpreting their behaviour under the effect of static and dynamic loads applied to a real case study: the Boussiaba dam. A three-dimensional finite element numerical modelling was undertaken using the Midas GTS- NX 2017 calculation code. The geometric model was established in Autocad taking into account the actual geomorphology of the terrain and the existing dam and then exported to GTS-NX. The dynamic solicitation, i. e. the earthquake, was generated from two accelerograms 0.25 g and 0.35 g amplitude respectively recorded in the Mila region located less than 20 km from the dam site. The initial static load being constituted by the dead weight, the water thrust and the sludge thrust at the bottom of the dam. Several reference points were chosen on the dam body to study the different parameters adopted. The results obtained during the dynamic numerical analysis show that the overall behaviour of the dam during earthquakes was satisfactory, without endangering the structural integrity of the structure. Keywords: Dynamic; Finite elements; Midas GTSnx; RCC dam; Three-dimensional. DOI 10.35180/gse-2021-0047

Dynamical modeling and analysis of hyperelastic spherical shells under dynamic loads and structural damping

This paper investigates the effects of dynamic loads and structural damping on the nonlinear behaviors of incompressible hyperelastic spherical shells modeled by the Yeoh strain energy function. Firstly, the dynamical modeling is formulated for the nonlinear behaviors of the shells by the variational principle, and the second order nonlinear ordinary differential equation describing the radially symmetric motion is obtained. Then, the dynamic behaviors, such as periodic, quasiperiodic and chaotic motions, are discussed under different loading types. Particularly, for constant loads, the first integral of the integrable Hamiltonian system without damping is given and it is numerically proved that there exists an asymmetric "∞" homoclinic orbit for the prescribed material parameters obtained in experiments; moreover, it is found that for different prestretches, the structural parameter has a completely different role on the nonlinearity of the system, and the basins of attraction are given with the structural damping. For periodic loads, there exist some interesting dynamic phenomena, i.e., quasiperiodic oscillation in the approximately integrable Hamiltonian system, limit cycles and chaos with the damping. The criterion for chaos is discussed by the Melnikov method combined with the numerical calculation and the chaos is further analyzed with the Poincaré section and the phase plane.