Influence Of Loading Conditions Research Articles

Experimental study on counterintuitive behavior of thin aluminium plates under free airblast loading

An experimental investigation of the counterintuitive behaviour in thin aluminium plates under fullfield test is presented in the paper. Special focus is placed on structural response and permanent deflection of the panels after the complex response. Thus, a series of tests with the plates varied in two kinds of thickness were conducted, where impulsive loading was generated by detonating the explosives at various standoff distances. As loaded impulsively, the vibration response was observed and the final configuration of each plate was measured and recreated. It is shown that all plates subjected to free air blast loading in such conditions exhibited plastic permanent deformation combined with distinct counterintuitive behaviour, as the plates deformed to the opposite direction of the incident wave. In addition, the characteristics of the permanent deflection can be divided into 2 typical deformation shapes, and the occurrences of which were correlated to the dimensionless parameter proposed in previous studies, confirmed to be an approximate indicator to describe the influence of loading conditions herein.

Nonlinear bending analysis of FG-GRC laminated cylindrical panels on elastic foundations in thermal environments

Abstract This paper presents an investigation on the nonlinear bending behaviors of nanocomposite laminated cylindrical panels made of graphene-reinforced composites (GRCs) supported by an elastic foundation under thermal environmental conditions. The extended Halpin-Tsai micromechanical model together with results from MD simulations is employed to obtain the material properties of GRCs which are temperature dependent. A piece-wise functionally graded distribution of graphene fillers along the panel thickness direction is adopted in order to maximize the effect of graphene reinforcement to the panels. The Reddy's third order shear deformable shell theory is applied to derive the governing equations for the bending problem of the panels and the von Karman geometric nonlinearity, the foundation support and the temperature effect are also included in the derivation. The governing equations are solved by applying a two-step perturbation approach to obtain the panel load-deflection and load-bending moment curves of FG-GRC laminated cylindrical panels subjected to a transverse uniform or sinusoidal load. The influences of loading conditions and temperature variation on the nonlinear bending behaviors of FG-GRC laminated cylindrical panels are discussed in details.

Influence of loading conditions on the overall mechanical behavior of polyether-ether-ketone (PEEK)

Testing methods have been developed to compare the mechanical responses and failure behavior of polyether-ether-keton (PEEK) thermoplastic polymer; under quasi-static, high strain rate tensile tests and fatigue loading. Tensile tests were performed with the strain rates varying from 0.0003 s−1 to 60 s−1 and at different temperatures to compare the flow characteristics of the samples undergone various testing conditions. Fatigue tests at different amplitudes and frequencies were also performed to evaluate the temperature rise during cyclic loading and its effect on the fracture behavior. Results show that dynamic tension, in comparison with quasi-static behavior, causes brittle fracture; whereas under fatigue test at high frequencies and loading amplitudes the material behaves not only a more ductile behavior but also it clearly shows the influences of induced self-heating in the modulus and mechanical properties of the PEEK were significant. So the major aim of this article is to discuss about the induced temperature and its effect on the fracture surface. Thermal fatigue has a very significant role in increasing temperature and reducing fatigue life; from there it is necessary to know the conditions at which thermal fatigue happens and also the amount of energy which is consumed. Obtained equation from the experimental results and calculations can estimate the energy dissipation in the fatigue tests which is as a function of cycle and frequency.

A study into the effect of loading conditions on the resistance of asymmetric high-speed catamaran based on experimental tests

Preparing high speed and sea keeping simultaneously are outstanding features of Catamaran boats (as one of multi-hull boats). In this paper, influence of loading conditions on drag through 6 series of experimental tests has been investigated. Experiments have been executed in a towing tank for model in scale 1 ratio to 11.43. Ultimately, results have been presented to full scale boat by Froude number and ITTC model. Loading conditions consist primarily of both weight of boat and longitudinal central gravity (LCG). Hence, adopted Catamaran has been examined in various loading conditions (light, full and over load) and two LCGs allocated to each weight in order to clarify effect of ones on drag. According to results whatever central gravity comes close to transom (backward position of LCGs), drag diminishes in high speed but increase in boat weight leads to decrease in its impact. As a consequence, the most descent of drag about 9.6% occurred in light load and maximum speed.

Mechanical performances of steel fiber reinforced high strength concrete disc under cyclic loading

A comparative study on high strength concrete discs reinforced with steel fibers under monotonic loading and cyclic loading was conducted in this contribution. A total of 40 specimens with steel fiber volume fraction ranging from 0.0% to 4% were tested. An investigation was performed on the influences of steel fiber volume fraction on fracture pattern, load-displacement response, deformation and strength. The influences of loading conditions on the mechanical performances of test specimens were also discussed in detail. Based on the experimental results, empirical equations for predicting the disc strength and deformation of high strength concrete reinforced with steel fibers were proposed.

Left ventricular systolic dysfunction during septic shock: the role of loading conditions.

The clinical significance of septic myocardial dysfunction is controversial, a fact that may be explained by the influence of loading conditions. Many indices may be useful to characterize cardiac function during septic shock, but their feasibility and physiological coherence in the clinical setting are unknown. Hemodynamic and echocardiographic data with tissue Doppler and speckle tracking were prospectively recorded on the first 3days of human septic shock. Hypokinesia, normokinesia, and hyperkinesia were defined as a left ventricular ejection fraction (LVEF) of<45, 45-60, and>60%, respectively. Twelve hemodynamic indices exploring contractility and loading conditions were assessed and analyzed. Two hundred and ninety-seven echocardiographies were performed in 132 patients. During the first 24h (H1-24), 48 (36.4%) patients were hyperkinetic, 55 (41.7%) were normokinetic, and 29 (22.0%) patients were hypokinetic. Thirteen patients had a secondary hypokinesia absent at H1-24 but present at H25-48 or H49-72, for an overall incidence of 42 (31.8%) during the first 3days. Despite a limited feasibility (<50%), global LV longitudinal peak systolic strain was impaired in a majority (>70%) of the patients assessed, including all those with depressed LVEF, and declined early in patients whose LVEF secondarily deteriorated. Most contractility indices were inversely correlated with afterload indices. Hyperkinetic patients exhibited the worst reduction in afterload indices. Hospital mortality was significantly higher in patients with LV hyperkinesia than in their counterparts: 30 (62.5%) vs. 35 (41.7%), p=0.02. Speckle tracking-derived strain was reduced in the majority of patients with septic shock, revealing covert septic myocardial dysfunction, but had poor feasibility. We found an inverse correlation between most of the contractility and afterload indices. Precise evaluation of afterload is crucial for adequate interpretation of LV systolic function in this setting.

Investigation of hydroelastic ship responses of an ULOC in head seas

Investigation of hydroelastic ship responses has been brought to the attention of the scientific and engineering world for several decades. There are two kinds of high-frequency vibrations in general ship responses to a large ocean-going ship in its shipping line, so-called springing and whipping, which are important for the determination of design wave load and fatigue damage as well. Because of the huge scale of an ultra large ore carrier (ULOC), it will suffer seldom slamming events in the ocean. The resonance vibration with high frequency is springing, which is caused by continuous wave excitation. In this paper, the wave-induced vibrations of the ULOC are addressed by experimental and numerical methods according to 2D and 3D hydroelasticity theories and an elastic model under full-load and ballast conditions. The influence of loading conditions on high-frequency vibration is studied both by numerical and experimental results. Wave-induced vibrations are higher under ballast condition including the wave frequency part, the multiple frequencies part, the 2-node and the 3-node vertical bending parts of the hydroelastic responses. The predicted results from the 2D method have less accuracy than the 3D method especially under ballast condition because of the slender-body assumption in the former method. The applicability of the 2D method and the further development of nonlinear effects to 3D method in the prediction of hydroelastic responses of the ULOC are discussed.

The influence of loading conditions on fracture initiation, propagation, and interaction in rocks with veins: Results from a comparative Discrete Element Method study

AbstractWe present the results of a comparative study of loading conditions on the interactions between extension fractures and veins. We model the fracture behavior of brittle discrete element materials each containing a tabular vein body of variable orientation and strength in two different loading conditions. The first is uniaxial tension, applied with servo‐controlled sidewalls. The second is a boudinage boundary condition in which a tensile triaxial stress state is induced in the brittle model volume by quasi‐viscous extensional deformation in the adjacent layers. Most of the fracture‐ vein interactions observed in uniaxial tension also exists in boudinage boundary conditions. However, the importance of each interaction mechanism for a given configuration of relative strength and misorientation of the vein may differ according to the loading mechanism. Nucleation and internal deflection is under both boundary conditions the dominating fracture‐vein interaction style in weak veins. In uniaxial tension models, strong veins tend to alter the fracture path by external deflection, while under boudinage loading these veins are more likely overcome by the fracture step over mechanism. Dynamic bifurcation of fractures was observed in uniaxial tension models but never for boudinage boundary conditions. This is because the acceleration of fracture tips in these conditions is suppressed by interaction with distributed fractures as well as viscous damping by the neighboring layers.

３次元圧電接合体の電場に及ぼす界面端における特異場の影響とその応用

Singular electric displacement fields occur around the vertex of interface in a piezoelectric material joints under loadings. In the previous study, influence of load conditions on singular electric displacement fields in the piezoelectric material joints were investigated to apply for engineering. In this study, some characteristics of singular electric displacement fields in an outside domain of piezoelectric material joints were investigated by using 3-dimensional finite element analysis. Influences of loading conditions on singular electric displacement fields are discussed . Singular electric displacement fields in an outside domain of piezoelectric material joints occur around the vertex of interface in it under loadings. Singular electric displacement fields are infulenced by tme change of the stress to depend on a piezoelectric material joints.

Performance of Shipboard Medium-Voltage DC System of Various Grounding Modes Under Monopole Ground Fault

This paper compares different grounding modes of a shipboard medium-voltage dc (MVDC) system such as ungrounded, solidly grounded, grounded with resistors, and grounded with resistors in parallel. Based on a typical shipboard MVDC system under different grounding modes, the transient short-circuit current and overvoltage under a monopole ground fault condition are calculated with PSCAD/EMTDC. The impact of the grounding resistance on the fault feature of the system is also studied. According to the comparative analysis and simulation results, a suitable grounding mode and the grounding resistance are proposed. The influences of load conditions, capacitance of loads, capacitance of the transmission cables, resistance between line and ground at the fault point, and fault position on the overvoltage are considered. Finally, a system protection scheme consisting of grounding mode selection, capacitor, arrester, and conjugate mirror filter has been developed.

Influences of Loading Condition and Rock Strength to the Performance of Rock Bolts

The influences of displacing angle, joint gap, and rock strength to the performance of rebar bolts and D-Bolts are evaluated in this study. A new method was developed to apply pull and shear loads to the bolt specimen in any combination so that a displacing angle can be established in the range from 0 (pure pull) to 90° (pure shear). In the tests, five displacing angles, two joint gaps, and three “rock” materials were used. The tests showed that the ultimate loads of both the D-Bolt and the rebar bolt remained constant for all the five displacing angles. The deformation capacity of D-Bolt is approximately 3.5 times the rebar under pure pull and 50 % higher than the rebar under pure shear. Both D-Bolt and rebar displaced more in the weak “rock” (concrete) than in the hard rock. The ultimate load of the bolts slightly decreased in the hard rock at pure shear. The deformation capacity of the bolts increased with the joint gap. The energy absorption capacity of the D-Bolt is 3.7 to 1.5 times that of the rebar bolt, depending on the displacing angle. The bolts installed in weak concrete blocks absorbed more energy than those installed in hard rock and high-strength concrete blocks. The loading angle is increased by the displacing angle. These two angles can be calculated with each other in an analytical solution.

Substantial Fatigue Similarity of a New Small-Scale Test Rig to Actual Wheel-Rail System

The substantial similarity of fatigue mechanism in a new test rig for rolling contact fatigue (RCF) has been investigated. A new reduced-scale test rig is designed to perform controlled RCF tests in wheel-rail materials. The fatigue mechanism of the rig is evaluated in this study using a combined finite element-fatigue prediction approach. The influences of loading conditions on fatigue crack initiation have been studied. Furthermore, the effects of some artificial defects (squat-shape) on fatigue lives are examined. To simulate the vehicle-track interaction by means of the test rig, a threedimensional finite element (FE) model is built up. The nonlinear material behaviour of the rail steel is modelled in the contact interface. The results of FE simulations are combined with the critical plane concept to determine the material points with the greatest possibility of fatigue failure. Based on the stress-strain responses, by employing of previously postulated criteria for fatigue crack initiation (plastic shakedown and ratchetting), fatigue life analysis is carried out. The results are reported for various loading conditions and different defect sizes. Afterward, the cyclic mechanism of the test rig is evaluated from the operational viewpoint. The results of fatigue life predictions are compared with the expected number of cycles of the test rig by its cyclic nature. Finally, the estimative duration of the experiments until fatigue crack initiation is roughly determined.

Influence of Load Condition on Flexural Properties and Shear Properties of Steel Tubular Columns Filled with Steel-Reinforced Concrete

In order to exert the force performance of steel tubular columns filled with steel-reinforced concrete, the focus of the paper is about the influence of load condition on flexural mechanical properties and the shear mechanical properties of the composite columns. The two types of loading conditions are: 1.Steel pipe, steel placed in the steel tube and concrete subject to compressive load simultaneously; 2.Compressive load acts on steel and concrete. The results show that the calculated results based on ADINA and the experimental ones are in agreement well. The calculated results also show that the load condition has no influence on flexural mechanical properties, but has a great influence on shear mechanical properties of the composite columns.

Influence of Load Conditions on Mechanical Behaviors of Steel Tubular Columns Filled with Steel-Reinforced Concrete Subjected to Axial Load

By using the finite element software ADINA, the focus of the paper is about the influence of load conditions on the axial compression performance of steel tubular columns filled with steel-reinforced concrete (STSRC) with the base that the calculated results are confirmed by the experimental data. Three types of loading conditions are these that: 1. Steel pipe, steel placed in the steel tube and concrete bear the compressive load; 2. Compressive load acts on the steel and concrete and there is a good bonding between the steel and concrete; 3.The steel and concrete bear the axial load, but the bond-slip between the steel tube and concrete are considered. The results show that the calculated results based on ADINA and the experimental ones are in agreement well, the bearing capacity and the ductility of the short composite columns are not almost influenced by the load condition-one and load condition-two, while the load condition-three has a influence on the axial compression performance of STSRC.

Influence of Loading Conditions during Tensile Testing on Acoustic Emission

The Acoustic Emission (AE) monitoring technique is widely used in mechanical and material research for detection of plastic deformation, fracture initiation and crack growth. However, the influence of AE features (such as signal amplitude, frequency, rise time and duration) on the fracture parameters (such as brittle or ductile mode of propagation and fracture propagation speed) is not completely understood. In this paper, the effect of loading conditions on fracture behavior was studied using AE monitoring during tensile testing of an aluminum alloy specimen. The fracture development was observed using a high speed video camera and was analyzed using the finite element method. The hardware and software produced by Physical Acoustics Corporation (USA) was used. Variations in AE parameters were analyzed and correlated to the stress-strain curves obtained during testing. It is shown that the strain rate and the presence of a crack (modeled by a notch on the sample), affect the fracture mode (brittle or ductile) and a relative amount of the mode dependent AE signatures.

Analysis and Testing for Slip Characteristics of Artificial Hydraulic Circuit based Push-Belt Continuously Variable Transmission

Applying a Continuously Variable Transmission (CVT) in an automotive driveline has several advantages. A CVT can operate at a wider range of transmission ratios, therefore the engine can be operated more efficiently than with a stepped transmission. The present research focuses on the influence of loading conditions on the slip behaviour and torque transmission of the CVT. The CVT model is developed to investigate the range of clamping forces needed to initiate the transmission and to successfully meet the oil pressure requirements. An analytical approach is used to calculate the possible transmission efficiency and traction coefficient of the push belt CVT. The experimental setup and the instrumentation are presented in detail. The measured results are presented in more detail for the V-belt type variator and oil pressure reapplication by a separate hydraulic unit and reduction ratio of CVT.

Multiaxial deformation and strain-induced crystallization around a fatigue crack in natural rubber

The study of fatigue crack propagation in elastomers is an essential prerequisite to improve the service life of tire products. Natural rubber is a key compound in tires, because of its unique mechanical properties and more particularly its remarkable resistance to fatigue crack growth as compared to synthetic rubbers. To explain this resistance, the literature often mentions the phenomenon of strain-induced crystallization which takes place at fatigue crack tips in natural rubber and then reinforces it. In the present study, an original experimental set-up that couples synchrotron radiation with a homemade mechanical fatigue machine is developed to investigate both strain-induced crystallization and deformation multiaxiality around fatigue cracks in natural rubber. During uninterrupted fatigue tests, recording of wide-angle X-ray diffraction patterns is performed in the crack tip region providing the two-dimensional spatial distribution of both crystallinity and principal strain directions. In particular, the influence of loading conditions on the size of the crystallized zone is investigated and related to fatigue crack growth rates. Finally, measurements of deformation multiaxiality, i.e. principal strain directions and change in thickness, obtained by this method are successfully compared with digital image correlation results.

Influence of Loading Conditions on the Deformation Behavior of Human Enamel Studied by Instrumented Indentation

As the hardest and one of the most durable load bearing tissues of the body, enamel has attracted considerable interest from both material scientists and clinical practitioners due to its excellent mechanical properties. The aim of this investigation is to determine the influence of different loading conditions on the deformation behavior of human enamel using instrumented indentation and Berkovich indenter. The used samples were fresh intact human premolars, extracted due to orthodontic reasons. Hardness tests were performed with different loading regimes. To study the influence of loading rates tree different loading rates have been used with 10, 100 and 1000 mN/min. at maximum applied load of 200 mN. The indentation size effect (ISE) was studied using loads from 5 mN to 400 mN without holding time. The indents have been studied using atomoc force microscopy and scanning electron microscopy.

The influence of loading conditions on equine hoof capsule deflections and stored energy assessed by finite element analysis

The biomechanical effects on the hoof capsule of the location of the centre of pressure of the ground reaction force may be important to understand the functioning of the hoof capsule. This study investigated the effect of changes in loading and contact friction on hoof deflections and elastic energy storage by varying the boundary conditions applied to finite element models. For all cases a load of 10 N kg−1, typical of the peak load in the trot gait, was used. In one scenario the coefficient of contact friction was varied from 0 (frictionless) to 1, at a constant non-zero joint moment, to simulate the effects of restriction of the hoof at the ground surface. In the other scenario a varying joint moment, with contact friction set at 0, was used to move the centre of pressure (COP) forward. Both increasing the ground surface friction and moving the COP forward caused the hoof capsule deflections and stored elastic energy to decrease. Peak strain energy in the capsule occurred when the frictional coefficient was 0 and when the COP was below the centre of rotation of the distal interphalangeal joint. Minimum strain energy occurred when the frictional coefficient was 1.0 and when the COP location was 30 mm forward of the joint centre. Hoof expansion and elastic energy storage are considerably influenced by ground surface friction and centre of pressure location. Therefore model validation studies should account for these parameters. Maximising the energy absorption may explain why heel first landing is preferred.

Welding residual stress behavior under mechanical loading

For an accurate estimation of the fatigue performance of welded joints, not only the initial residual stress field but also its variation under load is decisive. The portion of residual stress which stays stable can shift the load stress range much the same way as the mean stresses do in fatigue loading. The relaxation of residual stresses during fatigue loading however reduces this hazard to the structural health. That is, before considering the influence of residual stresses in fatigue, the effect of fatigue on residual stresses should be understood. In this work, the influence of the quasi-static and cyclic loading on the relaxation of welding residual stresses in small specimens and large components out of different steels namely S235JRG2, S355J2G3, P460NL, S690QL, S960QL, and S1100QL has been investigated experimentally. X-ray diffraction analysis as a reliable method has been used for the determination of residual stress profiles in surface layers. For residual stress analysis in deeper layers, synchrotron and neutron diffraction techniques were applied as complementary methods. A clear recognition of the difference between initial welding residual stresses in small- and large-scale specimens was observed. Tensile residual stresses as high as the yield strength could appear in large-scale welded specimens. That was not the case for small-scale welds due to the low grade of restraint. Nevertheless, in both types of samples, the highest residual stresses were obtained in the weld centerline. At the weld toe which is critical regarding fatigue crack initiation, the magnitude of the residual stresses is lower. Beside of that, it was observed that in the case of relaxation, the first load cycles especially in components out of low-strength steels are decisive. The influence of loading conditions and local mechanical properties on the relaxation of welding residual stresses was investigated based on principles of solid mechanics. The von Mises failure criterion was able to describe the relaxation behavior.