scholarly journals On the relationship between mechanical energy rate and heat dissipated rate during fatigue for a C45 steel depending on stress ratio

2021 ◽  
Author(s):  
Rosa De Finis ◽  
Davide Palumbo ◽  
Umberto Galietti
Keyword(s):  
Stress Ratio ◽  
Mechanical Energy ◽  
Energy Rate ◽  
The Relationship

scholarly journals On the relationship between mechanical energy rate and heat dissipated rate during fatigue for a C45 steel depending on stress ratio

2021 ◽  
Author(s):  
Rosa De Finis ◽  
Davide Palumbo ◽  
Umberto Galietti
Keyword(s):  
Loading Condition ◽  
Stress Ratio ◽  
Mechanical Energy ◽  
Full Field ◽  
Energy Rate ◽  
Temperature Signal ◽  
Stress Ratios ◽  
Harmonic Components ◽  
The Relationship ◽  
Stepwise Loading

This work deals with the analysis in the frequency domain of the temperature signal and mechanical energy rate of C45 steel under two different fatigue stepwise loading series at stress ratios of 0.1 and -1. It was first investigated the energy distribution among the harmonic components of the signals to understand possible variations caused by a different stress ratio. In addition, the second amplitude harmonic (SAH) of heat dissipated and mechanical energy rates have been considered in the analysis and their relationship was investigated. It has been shown as it depends only on the material, hence it is valid whatever the kind of the test is without any assumption on the energy supplied to the material or material hysteresis loop stabilisation. The adopted approach allows the analysis of intrinsic dissipations by means of rapid, full-field and contactless techniques without any specific requirement on loading condition or temperature signal stabilisation.

Power Harvesting from the Vibration-Induced by the Piezoelectric Stator of Traveling Wave Rotary Ultrasonic Motor

2011 ◽  
Vol 317-319 ◽  
pp. 616-620 ◽  
Author(s):  
Guang Qing Wang ◽  
Zhong Wei Zhao
Keyword(s):  
Energy Conversion ◽  
Analytical Model ◽  
Traveling Wave ◽  
Mechanical Energy ◽  
Ultrasonic Motor ◽  
Maximum Output ◽  
Induced Voltage ◽  
Power Harvesting ◽  
Conversion Model ◽  
The Relationship

In this article, a novel electro-mechanical energy conversion model of power harvesting from the vibration-induced the piezoelectric stator of the traveling wave rotary ultrasonic motor was proposed. Based on the curvature basis approach, the relationship between the deduced voltage and the mechanical stain induced by piezoelectric polarization was formulated. In addition to the relationships between the maximum induced voltages at the resonance frequency, the conversion energy density and the dimensions of the piezoelectric stator were also derived. The analytical model shows that the vibration-induced voltage is proportional to the exciting electrical voltage magnitude and square of height of the piezoelectric ceramic (PZT) but is inversely proportional to the permittivity of PZT and the damping coefficient of the stator. Some simulations and experimental results demonstrate that the maximum output voltage coincides with the energy conversion analytical model.

Hypercapnic acidosis increases oxygen cost of contractility in the dog left ventricle

1994 ◽  
Vol 266 (2) ◽  
pp. H730-H740 ◽  
Author(s):  
K. Hata ◽  
Y. Goto ◽  
O. Kawaguchi ◽  
T. Takasago ◽  
A. Saeki ◽  
...  
Keyword(s):  
Mechanical Energy ◽  
Left Ventricular ◽  
Oxygen Cost ◽  
Membrane Oxygenator ◽  
Arterial Perfusion ◽  
Control Value ◽  
Arterial Blood ◽  
Total Mechanical Energy ◽  
Lv Volume ◽  
The Relationship

The effect of acidosis on left ventricular (LV) mechanoenergetics was assessed in seven excised, cross-circulated dog hearts with the use of the frameworks of the contractility index (Emax) and the relationship between myocardial oxygen consumption (VO2) and pressure-volume area (PVA; a measure of the LV total mechanical energy). Acidosis was stably maintained without hypoxia by appropriately mixing CO2 and air in a membrane oxygenator in the coronary arterial perfusion circuit. Acidosis [pH: 6.98 +/- 0.09 (SD), PCO2: 91 +/- 25 mmHg in the coronary arterial blood] decreased Emax by 45 +/- 12% (P < 0.01) and PVA by 47 +/- 12% (P < 0.01) at a fixed LV volume. When the preacidosis Emax level was restored by Ca2+ infusion during acidosis, unloaded VO2 (the VO2 intercept of the VO2-PVA relation) exceeded the control value by 19 +/- 17% (P < 0.05), indicating that acidosis required higher VO2 for nonmechanical activities at a matched Emax. Moreover, the oxygen cost of enhanced contractility (the incremental ratio of unloaded VO2 to Emax) was 1.53 +/- 0.40 times higher (P < 0.01) during acidosis than preacidosis. We conclude that acidosis results in LV contractile dysfunction accompanied by an increased oxygen cost of contractility. This increased energy cost of the excitation-contraction coupling can be accounted for by a decreased Ca2+ sensitivity of the contractile proteins during acidosis.

Softening of Vulcanized Carbon Black-Loaded Rubber during Extension

1955 ◽  
Vol 28 (4) ◽  
pp. 1123-1132
Author(s):  
D. G. Marshall ◽  
D. L. Walker ◽  
J. G. Smith
Keyword(s):  
Carbon Black ◽  
Viscoelastic Material ◽  
Mechanical Energy ◽  
Viscoelastic Model ◽  
Hysteresis Cycle ◽  
Cross Linkage ◽  
Mechanical Bond ◽  
Softening Process ◽  
Increasing Temperature ◽  
The Relationship

Abstract The results of the observations recorded in this paper may be summarized by the following items. 1. A difference between the first and second load-extension curves is to be expected in any viscoelastic material, although the behavior of black-loaded rubber at large extensions differs in some fundamental respects from a simple viscoelastic material. 2. Within the experimental limits of about ±10 per cent, all of the energy used in softening the black-loaded rubbers studied appears as heat. 3. The ratio between the area of the hysteresis cycle obtained on first stretching a specimen of black-loaded rubber and that obtained during the second extension varies only slightly from compound to compound in the range of extensions studied. 4. Although the modulus of a black-loaded rubber decreases with increasing temperature, the ratio between the hysteresis area of the first extension and that of the second extension remains roughly constant over the temperature range studied. 5. There are electrical resistance changes that correspond closely to the mechanical softening effects experienced with black-loaded rubber. Result (2) suggests that if cross-linkage breaking or changes of state of rubber are specified as mechanisms for producing softening, then the potential energy changes required must be small, compared with the mechanical energy available. Result (5) shows that changes in arrangement of the carbon black particles are associated with the softening process, and therefore suggests that the softening is related to internal strains in the rubber. These results do not prove that the softening observed in rubber is similar in principle to the behavior of a simple viscoelastic model during the first and other extensions. However, these observations are consistent with this view, except for the difficulty connected with the relationship between the softening and the permanent set in the simple viscoelastic material, and the difficulty connected with the persistence of softening. A simple linear model is obviously bound to have considerable limitations in describing the properties of a black-loaded rubber at high extensions. The limitations may arise from the nonlinearity of rubber elasticity and the non-Newtonian nature of rubber flow; alternatively, it may be necessary to postulate some entirely different process, such as rubber heterogeneity or mechanical bond breaking.

scholarly journals Spring-like leg behaviour, musculoskeletal mechanics and control in maximum and submaximum height human hopping

2011 ◽  
Vol 366 (1570) ◽  
pp. 1516-1529 ◽  
Author(s):  
Maarten F. Bobbert ◽  
L. J. Richard Casius
Keyword(s):  
Energy Expenditure ◽  
Muscle Activation ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
And Control ◽  
The Relationship

The purpose of this study was to understand how humans regulate their ‘leg stiffness’ in hopping, and to determine whether this regulation is intended to minimize energy expenditure. ‘Leg stiffness’ is the slope of the relationship between ground reaction force and displacement of the centre of mass (CM). Variations in leg stiffness were achieved in six subjects by having them hop at maximum and submaximum heights at a frequency of 1.7 Hz. Kinematics, ground reaction forces and electromyograms were measured. Leg stiffness decreased with hopping height, from 350 N m −1 kg −1 at 26 cm to 150 N m −1 kg −1 at 14 cm. Subjects reduced hopping height primarily by reducing the amplitude of muscle activation. Experimental results were reproduced with a model of the musculoskeletal system comprising four body segments and nine Hill-type muscles, with muscle stimulation STIM( t ) as only input. Correspondence between simulated hops and experimental hops was poor when STIM( t ) was optimized to minimize mechanical energy expenditure, but good when an objective function was used that penalized jerk of CM motion, suggesting that hopping subjects are not minimizing energy expenditure. Instead, we speculated, subjects are using a simple control strategy that results in smooth movements and a decrease in leg stiffness with hopping height.

scholarly journals The suction,yield and strength characteristics of unsaturated intact loess based on true tri-axial tests

2019 ◽  
Vol 7 (3) ◽  
Author(s):  
Jinjin Fang
Keyword(s):  
Principal Stress ◽  
Stress Ratio ◽  
Shear Failure ◽  
Confining Pressure ◽  
Intermediate Principal Stress ◽  
True Triaxial ◽  
Yield Stress Increase ◽  
Isotropic Consolidation ◽  
The Relationship ◽  
Intact Loess

To simulate the failure of loess under undrained condition in the actual engineering,a series of isotropic consolidation and shear tests with different intermediate principal stress ratio b under constant water content were performed on intact loess with various initial suctions using the true tri-axial apparatus for unsaturated soil. The relationship between the saturations and initial suctions,the characteristics of yield,suction and strength of unsaturated intact loess were studied. The results show that the initial suctions and the suctions after the isotropic consolidation decrease with the increase of saturations. The suctions increase with the increase of the intermediate principal stress ratio b at the true triaxial shear failure. The net mean yield stress increase with the increase of the initial suction. The yield suction is a constant,but not always equal to the maximum suction that the soil specimen experienced in the history. The strength of soil increase with the increase of the net confining pressure,initial suction and the intermediate principal stress ratio b.

scholarly journals Design of Hydro Power by Using Turbines Kaplan on The Discharge Channel Paiton 1 and 2

2018 ◽  
Vol 42 ◽  
pp. 01008
Author(s):  
Alvin K. Sosilo ◽  
Harsono Hadi ◽  
Totok Soehartanto
Keyword(s):  
Discharge Channel ◽  
Block Diagram ◽  
Mechanical Energy ◽  
Mechanical Power ◽  
Hydro Power ◽  
Kaplan Turbine ◽  
Turbine Performance ◽  
Power Turbine ◽  
Simulation Results ◽  
The Relationship

Condenser water from the discharge channel PJB Paiton discharged to the sea has the potential mechanical energy, because the flow rate of 7.6 m3 / s (if both discharge PJB Paiton function) and the discharge channel reaches a height of 4m. This paper will describe the design of hydro power (in the form of a block diagram) by using Kaplan turbine driven by utilizing the wastewater condenser. Kaplan turbine performance represented in the form of the relationship between the incoming water flow and the pitch angle (the angle between the propellers with a hub) to the torque generated. The simulation results indicate that the turbine torque is proportional to the mechanical power turbine. The greater the torque, the greater the mechanical power, and vice versa.

Relationship Between Various Training-Load Measures in Elite Cyclists During Training, Road Races, and Time Trials

2019 ◽  
Vol 14 (4) ◽  
pp. 493-500 ◽  
Author(s):  
Teun van Erp ◽  
Carl Foster ◽  
Jos J. de Koning
Keyword(s):  
Perceived Exertion ◽  
Mechanical Energy ◽  
Training Load ◽  
The Other ◽  
Rating Of Perceived Exertion ◽  
Heart Rate Data ◽  
Training Stress ◽  
Training Impulse ◽  
Road Races ◽  
The Relationship

Purpose: The relationship between various training-load (TL) measures in professional cycling is not well explored. This study investigated the relationship between mechanical energy spent (in kilojoules), session rating of perceived exertion (sRPE), Lucia training impulse (LuTRIMP), and training stress score (TSS) in training, races, and time trials (TT). Methods: For 4 consecutive years, field data were collected from 21 professional cyclists and categorized as being collected in training, racing, or TTs. Kilojoules (kJ) spent, sRPE, LuTRIMP, and TSS were calculated, and the correlations between the various TLs were made. Results: 11,655 sessions were collected, from which 7596 sessions had heart-rate data and 5445 sessions had an RPE score available. The r between the various TLs during training was almost perfect. The r between the various TLs during racing was almost perfect or very large. The r between the various TLs during TTs was almost perfect or very large. For all relationships between TSS and 1 of the other measurements of TL (kJ spent, sRPE, and LuTRIMP), a significant different slope was found. Conclusion: kJ spent, sRPE, LuTRIMP, and TSS all have a large or almost perfect relationship with each other during training, racing, and TTs, but during racing, both sRPE and LuTRIMP have a weaker relationship with kJ spent and TSS. Furthermore, the significant different slope of TSS vs the other measurements of TL during training and racing has the effect that TSS collected in training and road races differs by 120%, whereas the other measurements of TL (kJ spent, sRPE, and LuTRIMP) differ by only 73%, 67%, and 68%, respectively.

Influence of Stress Ratio on the Reliability of Al/Carbon-Fiber Composite Hydrogen Tanks

2008 ◽  
Author(s):  
Haiyan Bie ◽  
Ping Xu ◽  
Jinyang Zheng ◽  
Fangming Kai ◽  
Pengfei Liu ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Hydrogen Storage ◽  
Stress Ratio ◽  
Fiber Composite ◽  
Density Ratio ◽  
Random Variables ◽  
Theoretical Method ◽  
Carbon Fiber Composite ◽  
Composite Layers ◽  
The Relationship

Hydrogen has been proposed as an important energy source for fuel cell vehicles (FCV), and the hydrogen storage tank is considered to be indispensable key equipment for hydrogen application. Currently, Al/carbon-fiber composite hydrogen tanks have become a study focus due to their outstanding properties such as high stiffness-density and strength-density ratio. In standards of this type hydrogen tanks, stress ratio is a primary parameter to be determined. Raising the stress ratio, the reliability will be increased; however, the hydrogen storage density will be decreased accordingly. In this paper, a study on the relationship between the stress ratio and reliability is carried out based on the static strength reliability analysis. The stress-strength interference model is used for the calculation of reliability. For fiber reinforced hydrogen tanks, the stress variance is mainly influenced by two classes of random variables, and the quantity of random variables is affected by the number of composite layers which depends on the stress ratio. So by analysis of stress distribution, the influence of stress ratio on the reliability is revealed, and a theoretical method is developed that can be used for selecting rational stress ratio in the standard.

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