Effect Of Variable Loading Research Articles

Effect of variable load on centralized dimple in opposite sliding condition

Abstract In ball bearings without a cage, adjacent balls exhibit a zero-entrainment velocity (ZEV) contact condition, which is worse than typical pure rolling or rolling-sliding contact, and the contact between adjacent balls under periodic loading is notably more complicated. In this work, thermal elastohydrodynamic lubrication (EHL) numerical calculation is carried out under the condition of periodic impact and opposite sliding line contact over a wide range of surface speeds. the pressure is solved by multigrid method, the elastic deformation is evaluated using multigrid integration method, the temperature field is calculated by column-by-column scanning technique. The results show that the loading-unloading process exerts significant influence on the variation of the centralized dimple, pressure, and temperature rises as well as the oil characteristics. With the increase of surface speed, the effect of load fluctuations diminishes, and the central dimple exhibits the following evolutionary trend under ZEV conditions: no dimple at very low velocity - small central dimple - large typical dimple - no dimple at high velocity. The result indicates that under the ZEV condition of EHL stage, elevated velocities decrease the coefficient of friction and augment the film thickness.

The Effect of Variable Load on Dynamic Behavior of Thin Pipe by Hamilton Principle and Cfx-Ansys

This paper presents the study and analysis, analytically and numerical of circular cylindrical shell pipe model, under variable loads, transmit fluid at the high velocity state (fresh water). The analytical analysis depended on the energy observation principle (Hamilton Principle), where divided all energy in the model to three parts , strain energy, kinetic energy and transmitted energy between flow and solid (kinetic to potential energy). Also derive all important equations for this state and approach to final equation of motion, free and force vibration also derived. the relations between the displacement of model function of velocity of flow, length of model, pipe thickness, density of flowed with location coordinate x-axis and angle are derived. In numerical analysis the models are created by using ANSYS Workpench-12 program, where build two models one for fluid, and another for pipe (solid). Depended on CFX-ANSYS package, can transfer all parameters in the fluid (temp., presser, energy) to solid model. The result show a good agreement and low of percentage error between the analytically and numerical result. Also shows the effects of length and flow velocity on the behaviour of pipe

Study on the durability of steel wire under the coupling effects of harsh environment and variable loads

steel wire is regarded as the most important component of cable-stayed bridges, and it has been widely used in practical engineering. Most of the studies only considered the effect of variable loads and chloride corrosion on the durability of steel wires separately. However, few studies have reported their coupling effects. In order to investigate the durability of steel wires considering their coupling effects, A physical test was performed to investigate the corrosion–fatigue performance. After the experiment finished, a tensile device was used to test the mechanical properties of corroded steel wires with different corrosion degrees. Then the corrosion characteristics of different specimens and fracture surface morphology of the steel wires were investigated using a 3D scanner, which was used to analyse the failure mode of each type of steel wires. In addition, a model was proposed to evaluate the reliability of corroded steel wires. Finally, a fatigue test was conducted to explore their fatigue performance and the S-N curve of steel wires with different corrosion degrees was obtained. The results show that the fatigue life of the steel wires is mainly affected by environmental effects when the steel wire at low stress amplitudes. However, as the stress amplitude increases, the fatigue life of it is decided by the stress amplitude. The fracture morphology of the corroded steel wires can be two categories: single-source fracture and multi-source fracture, For the steel wires corroded slightly, cracks often drive from one fatigue source (pit defect). As the corrosion degrees increase, the depth of pits enhances, cracks drive from different fatigue sources. In addition, the propagation zones decrease, and the rupture regions increase, as the steel wires corroded seriously.

One‐dimensional nonlinear creep consolidation of soft soils with time‐dependent drainage boundary under construction load

AbstractTo further investigate the nonlinear creep properties of soft soils and the effect of variable loading, a one‐dimensional (1D) nonlinear creep consolidation system of soft soils under construction load is established, including time‐dependent drainage (TDD) boundary, elastic‐viscous‐plastic deformation, non‐Darcy flow (NDF), and self‐weight stress. The consolidation problem is presented by virtue of the finite volume method, and the associated calculation program is compiled. The efficiency of the numerical solutions is validated by comparing the degenerated solution against analytical, semi‐analytical, and numerical solutions. Then the influences of construction load and nonlinear creep model parameters on consolidation are studied. The results show that TDD boundary and construction load significantly affect consolidation, and the larger the loading rate and interface parameter, the faster soil's overall dissipation process of excess pore‐water pressure (EPP). Meanwhile, at the earlier consolidation stage, considering the secondary consolidation effect will cause an increase in excess pore‐water pressure (EPP). Prolonging the construction period, decreasing the interface parameter, considering the self‐weight stress, or increasing the non‐Newtonian index will all aggravate this phenomenon. Additionally, the TDD boundary, construction load, and non‐Newtonian index flow (NNIF) are not a determinant for final soil settlement.

Optimal Design and Performance Analysis of Three-phase Distribution Transformer with Variable Loading

Electrical power passes through several transformers after generation through consumption. The final stage of any power system consists of many small-rating distribution transformers. Since the loads connected to these transformers vary with time, their effective design and operation with variable loading conditions are crucial for the system to operate efficiently and reliably. In most previous works, loads connected to these transformers are treated as constant power and stray losses of the transformers are neglected in the calculations. Neglecting the load variation and stray losses reduces the transformer life span noticeably and impairs grid quality and reliability. In this work, a small-rating distribution transformer is designed and analyzed analytically and numerically. Detailed procedures on the conventional design are presented with the general design issues. The effect of variable loading on the transformer’s power losses, efficiency, temperature rise, voltage regulation, and output voltage variation is analytically and numerically investigated. Results show that the rating and power factor of the load significantly influence the performance characteristics of the transformer.

Comparison of the Potentiating Effect of Variable Load Jump Squats on Acute Drop Jump Performance in Rugby Sevens Athletes.

Poulos, N, Haff, GG, Nibali, M, Graham-Smith, P, and Newton, RU. Comparison of the potentiating effect of variable load jump squats on acute drop jump performance in rugby sevens athletes. J Strength Cond Res 37(1): 149-160, 2023-The effect of variable load jump squats (JSs) on acute drop jump (DJ) performance across multiple sets was examined. Seventeen elite rugby sevens athletes performed 3 DJs after 3 repetitions of a JS conditioning activity (CA) performed at 30 or 50% 1RM back squat loads. Acute postactivation performance enhancement (PAPE) in DJ kinetic and kinematic variables was assessed using a commercially available force platform (1,000 Hz). Postactivation performance enhancement was predominant after the 30% 1RM load with the greatest frequency of potentiation exhibited in set 3. The 50% 1RM CA resulted in substantial decrements in DJ performance with the exception of active stiffness, reactive strength index (flight:contact time), and contact time. Moderate differences were observed between the 50 and 30% 1RM loads for peak power (W), impulse (N·s), and force at zero velocity (N); active stiffness was the only variable where PAPE was greater in the 50% 1RM CA (ES: small). Active stiffness was the only variable to display favorable associations with relative strength in both the JS 30% 1RM (ES: 0.38 ± 0.20; moderate) and 50% 1RM (ES: 0.24 ± 0.23; small) CA loads. The JS 30% 1RM CA results in greater magnitude and frequency of PAPE of DJ kinetic and kinematic variables and is recommended if seeking to target PAPE in a range of DJ performance variables. Heavier JS loads may be appropriate if enhancement of muscle stiffness and stretch-shortening cycle efficiency is required. Consideration of targeted kinetic and kinematic variables when selecting CA intensity in complex training design is recommended.

Experimental-theoretical studies of hydrotechnical angular-type retaining walls

Relevance. Retaining walls are common structures that are part of waterworks. They have the characteristic features of hydraulic structures, such as large dimensions, low percentages of reinforcement (up to 1.0%), horizontal interblock joints. The listed features determine the nature of the work and the stress-strain state of the retaining walls. The main loads on the rear faces of the retaining walls are loads from the action of the backfill soil. The incomplete consideration of the design features and the nature of the loads action in the design of a number of retaining walls that are in the stage of long-term operation has caused the need to strengthen them. One of the reinforcement methods was to install reinforcement rods in drilled inclined holes in the zones of horizontal interblock joints. It was necessary to conduct experimental studies of reinforced concrete retaining walls under the action of various loads, in particular conside- ring the reinforcement by inclined rods. The aim of the experimental research was to study the effect of variable load on the stress-strain state of these structures, among others with due regard to inclined reinforcement installed in the zones of horizontal interblock joints. When solving the set tasks, proven experimental methods of researching reinforced concrete structures of hydrotechnical structures were used. Results. Experimental data from the study of models of retaining walls, including those with reinforcement by inclined reinforcement, at different locations of the resultant load on rear faces of models were obtained. An experimental substantiation of the reinforcement of reinforced concrete structures of retaining walls with an inclined reinforcement crossing horizontal construction joints has been carried out.

Using a residual strength model to predict mode II delamination failure of composite materials under block fatigue loading

An experimental investigation was undertaken to measure delamination growth to the point of failure under spectrum loading including the effects of cycle sequences. Composite coupons were subjected to Mode II fatigue loading using a reversible three point bend test rig under displacement control. Stress-life curves were established using results from a series of constant amplitude fatigue tests. Variable loading effects were then assessed using a series of methodical block loading fatigue tests for which a residual strength method was successfully adjusted for use with displacement controlled test data. The model produced conservative predictions which displayed good agreement with experimental results.

BEHAVIOUR OF DIFFERENT TYPES OF FOUNDATION SUBJECTED TO DYNAMIC LOADS AND RESTED ON SAND SOIL

Studying of foundation behaviour under different loading cases is one the most important topics that has occupied a great deal of interest. Foundation closely correlated with factors and surrounding conditions such as type of active load and type of soil bearing foundation. Non-static load (dynamic) is one of the most dangerous types of loads that affect the foundations such as earthquakes, which in turn depends heavily on the weight of the building, which depend on the number of floors, as well as the type of soil bearing foundations. To study the effect of variable load on the foundations, a model of two different types of foundations was presented (Raft – Raft with inverted beam) and exposed to El_centro earthquake with constant soil type and changing the number of floors (5, 10 and 15). From analysis results, it showed that:- 1- Raft and raft with inverted beam have almost equal stresses and deformations. 2- Raft with inverted beam is better in resisting H.Z displacement resulting of dynamic loads than raft. 3- Raft with inverted beam improved results although it is equal to 70 % of raft inertia, so that it is better to use it with dynamic loads.

Calculating the Equivalent Service Lifetime of Power Generating Units in Thermal Power Plants1,2

To evaluate the effect of variable loads on the operating efficiency of generating units at thermal power plants we propose using an indicator of the effective run time of the turbine. Formulas are given and an example of calculating the equivalent service lifetime of a power generating unit for different loads is provided.

Effects of Variable Loading on Residual Fatigue Life of the Railway Wheelset

The paper deals with the effects of variable loading on residual fatigue life of the railway wheelset. The railway wheelsets can include some cracks created during manufacturing process or during previous operation. Therefore, it is important to know how the existing cracks will behave during further service of the train. The experiments show that the fatigue crack growth rate depends not only on size of the load amplitudes in a loading spectrum, but it depends also on the sequence of load amplitudes. Taking into account interaction effects of overloading cycles requires use a method that calculates increments of crack length in each cycle, i.e. cycle-by-cycle. One of such methods represents generalized Willenborg model. This model was used for residual fatigue life time estimations of railway wheelset and results obtained were compared with classical approach, which did not take into account interaction effects. Results obtained can be used for establishing of service intervals of railway wheelsets.

New Energy Power Generation Process Output Complementary and Coordinated Control

in view of the current high rate of abandoned wind, photovoltaic power generation costs and wind-fire bundling mode, in the active power control of the wind of low load operation of motor fluctuations in the fire team leader, the subject in the study of wind power, photovoltaic power generation, power, battery energy storage based on the load response characteristic, design the scheduler, a wind and photovoltaic power plant active power scheduling for equipment, allocation of plant-level optimal load distribution system of the thermal power plant joint scheduling, in order to improve the stability of output of new energy, reduce the energy consumption of the whole network. At the same time, the wind and photovoltaic power plant energy storage system and wind farm output coordination problem is equivalent to a mixed integer programming problem to be solved, to simultaneously determine fans and solar panels and bear the load rate; for thermal power plant load distribution optimization design of the minimum unit involved in strategy reduces the effect of variable load, variable load on set pressure and high temperature parts life. This topic to some extent to improve the wind energy and solar energy utilization, helps to reduce the carbon fuel usage, has certain theoretical and practical significance.

변동진폭하중 하에서 균열성장 예측의 실험적 검증

본 연구에서는 모드 I의 변동진폭하중 하에서 평판의 두께관통 균열성장을 예측하고 예측결과를 실험을 통해 검증하였다. 균열성장 모델을 위해 과하중으로 인한 균열가속과 지연효과를 고려하는 Huang의 모델식을 이용하였다. 실험적 검증을 위해 Al6016-T6 평판 균열을 제작하여 변동하중을 부여하고 균열길이를 일정 주기로 육안 측정하였다. 측정데이터로부터 모델 변수를 추정하기 위해 베이지안 접근법에 기반한 파티클 필터 방법을 이용하였고, 이를 통해 위험크기까지의 미래 거동 및 잔존수명을 확률적으로 예측하였으며, 이를 실제 실험한 결과와 비교하였다. 그 결과 변동하중에 의한 균열지연이 잘 예측됨을 확인하였고, 측정 데이터가 증가할수록 예측된 중앙값(median)이 실제와 점점 더 일치하였다. In this study, crack growth in a center-cracked plate is predicted under mode I variable amplitude loading, and the result is validated by experiment. Huang's model is employed to describe crack growth with acceleration and retardation due to the variable loading effect. Experiment is conducted with Al6016-T6 plate, in which the load is applied, and crack length is measured periodically. Particle Filter algorithm, which is based on the Bayesian approach, is used to estimate model parameters from the experimental data, and predict the crack growth of the future in the probabilistic way. The prediction is validated by the run-to-failure results, from which it is observed that the method predicts well the unique behavior of crack retardation and the more data are used, the closer prediction we get to the actual run-to-failure data.

On the prediction of fatigue crack initiation in rolling/sliding contacts with provision for loading sequence effect

The principles of continuum damage mechanics are applied to predict the rolling/sliding contact fatigue crack initiation. The approach involves evaluating the subsurface stresses as well as the state of damage within the contact region. It is shown that the fatigue crack initiation life can be related to the scalar damage parameter D, which is a measure of micro-crack and voids density in the material. Comparison of the predicted results with the available experimental work shows good agreement. The effect of variable loading on the fatigue behavior of rolling contact with provision for non-linear damage evolution is also investigated.

Predicting Effect of Pressure, Shaft Velocity and Surface Finish on Depth of Wear of Lining Thickness of Engine Bushing by Experimentation

Hydrodynamic Cu-Pb-Sn material journal bearings are widely used in automobile and industrial application because of its simplicity, efficiency and low cost. The bearing is often subjected to many stops and starts with unknown load cycles. During this transient period, friction is high and bushes become progressively worn-out, thus inducting certain disabilities. The bushes are provided with a lining of Cu-Pb-Sn material which is found in the range of 450 to 600 micron. The bearing designers are not provided the attention toward this dimension as in practice the failure of bushes observed by seizer, scoring, pitting, cavitations, loss of Babbitt due to high fatigue loads etc. The total depth of wear of healthy journal bearing is observed 150 to 180 micron up to 40000 kms run. The aim of present experimental work is to determine the effect of variable load, sliding velocity of shaft and deterministic surface roughness (R a ) of lining material on sliding wear behaviour and depth of wear of lining thickness(d w ) of Cu-Pb-Sn material bush, which is widely used as bush material in automobile engine. The highest temperature zone was determined and the bush samples are marked circumferentially as a, b, c, d, e, f, g in front side and a', b', c', d', e', f', g' rear side in that region. The relationship between depth of wear of lining thickness (d w ) versus load, shaft speed, surface roughness is established by using the experimental results and regression model. The numerical result indicates that the surface roughness is most important bearing characteristics and the combined effect of load, shaft speed and surface roughness on depth of wear of lining material particularly in high temperature zone.

Predicting effect of pressure, shaft velocity and surface finish on depth of wear of lining thickness of engine bushing by experimentation

Hydrodynamic Cu-Pb-Sn material journal bearings are widely used in automobile and industrial application because of its simplicity, efficiency and low cost. The bearing is often subjected to many stops and starts with unknown load cycles. During this transient period, friction is high and bushes become progressively worn-out, thus inducting certain disabilities. The bushes are provided with a lining of Cu-Pb-Sn material which is found in the range of 450 to 600 micron. The bearing designers are not provided the attention toward this dimension as in practice the failure of bushes observed by seizer, scoring, pitting, cavitations, loss of Babbitt due to high fatigue loads etc. The total depth of wear of healthy journal bearing is observed 150 to 180 micron up to 40000 kms run. The aim of present experimental work is to determine the effect of variable load, sliding velocity of shaft and deterministic surface roughness (Ra) of lining material on sliding wear behaviour and depth of wear of lining thickness(dw) of Cu-Pb-Sn material bush, which is widely used as bush material in automobile engine. The highest temperature zone was determined and the bush samples are marked circumferentially as a, b, c, d, e, f, g in front side and a’, b’, c’, d’, e’, f’, g’ rear side in that region. The relationship between depth of wear of lining thickness (dw) versus load, shaft speed, surface roughness is established by using the experimental results and regression model. The numerical result indicates that the surface roughness is most important bearing characteristics and the combined effect of load, shaft speed and surface roughness on depth of wear of lining material particularly in high temperature zone. Keywords: Crank shaft bush, test rig, depth of wear, lining thickness, surface roughness.

A comparative study on gate leakage and performance of high-𝛋 nano-CMOS logic gates

This paper provides a novel attempt to evaluate the gate leakage and delay characteristics of CMOS transistors and logic gates with various alternative high-κ gate dielectrics, which are replacing SiO2 in traditional nanoscale MOSFETs. Results have been obtained for both fixed as well as variable loads. The assumption that all gates drive the same load is considered in order to provide a fair comparison of the effect of the variation of design and process parameters, especially that of different high-κ dielectrics on the gate direct tunnelling current and propagation delay. On the other hand, the variable loading effect considers a set of practical loading conditions for the logic gates. An exhaustive comparison of all cases finally presents concluding evidence that the tunnelling current is independent of the loading conditions. On the other hand, there is an increase in the delay as the dielectric constant of the gate material, and consequently the load on the device, increases. Ultimately, this paper presents fast and accurate models for on-the-fly calculation of tunnelling current and delay with the aim of integrating them into design automation tools.

Effect of variable loading in the determination of upper-limb anaerobic power in persons with tetraplegia.

This article examines the effects of levels of resistance loading during arm Wingate Anaerobic Testing (WAnT) in persons with differing levels of cervical spinal cord injury (SCI). Thirty-nine persons with motor-complete SCI tetraplegia (13 each at C5, C6, and C7) performed six bouts of arm-crank WAnT with relative loads equivalent to 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 percent of body mass (BM). Power output was determined with the use of the SMI OptoSensor 2000 (Sports Medicine Industries, Inc., St. Cloud, MN, USA) hardware and software package. Values of peak power (P(peak)) and mean power (P(mean)) were examined statistically between groups (C5, C6, and C7) and across levels of resistance loading. Resistance loads that provided the greatest values of P(mean) for the three groups were as follows: C5 = 1.0 or 1.5 percent of BM; C6 = 1.5 or 2.0 percent of BM; and C7 = 2.5, 3.0, or 3.5 percent of BM. Appropriate loading for arm WAnT is specific to the level of tetraplegia and may provide a useful assessment of upper limb power production.