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.

scholarly journals Piezoelectric mathematical modeling; technological feasibility in the generation and storage of electric charge

2022 ◽  
Vol 2159 (1) ◽  
pp. 012009
Author(s):  
J E Camargo-Chávez ◽  
S Arceo-Díaz ◽  
E E Bricio-Barrios ◽  
R E Chávez-Valdez
Keyword(s):  
High Performance ◽  
Emerging Technologies ◽  
Mechanical Energy ◽  
Energy Generation ◽  
Energy Sources ◽  
The Cost ◽  
Relationship Of ◽  
Sound Pulses ◽  
The Relationship ◽  
And Storage

Abstract Emerging technologies are efficient alternatives for satisfying the growing demand for sustainable and cheap energy sources. Piezoelectrics are one of the most promising energy sources derived from emerging technologies. These materials are capable of converting mechanical energy into electricity or vice versa. Piezoelectrics have been used for almost a hundred years to generate electrical and sound pulses. However, the use of piezoelectrics for power generation is constrained by the cost associated with equipment and infrastructure. This problem has been addressed through mathematical models that relate the physical and electrical properties of the piezoelectric material with the voltage generated. Although these models have high performance, they do not incorporate voltage rectification and electrical charge storage stages. This work presents a mathematical model that describes the relationship of the physical and electromechanical properties of a system employing a piezoelectric for energy generation. The voltage of the system and the charge stored in a capacitor are calculated through this model. Also, contour diagrams are presented as a tool for facilitating the efficiency of energy generation.

scholarly journals Study on Mechanical Properties of Gravelly Sand under Different Stress Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Dongjie Zhang ◽  
Fei Luo ◽  
Zhanyuan Zhu ◽  
Jiaming Liu ◽  
Jing Li ◽  
...  
Keyword(s):  
Strain Hardening ◽  
Stress Ratio ◽  
Void Ratio ◽  
Strain Softening ◽  
Triaxial Compression ◽  
Stress Path ◽  
Tibet Plateau ◽  
Shear Tests ◽  
Characteristic Angle ◽  
The Relationship

To investigate the strength and deformation characteristics of gravelly sand on the Qinghai-Tibet Plateau under different stress paths, a series of triaxial shear tests was conducted under confining pressures of 50–400 kPa in four types of stress path conditions of conventional triaxial compression (CTC) (drained and undrained), triaxial compression (TC), and reduced triaxial compression (RTC). We can see from the test results that gravelly sand samples show strain hardening and shear contraction under the CTC (drained), TC, and RTC during the shearing process but exhibit strain softening under the CTC (undrained). To explore the microscopic deformation mechanism of gravelly sand, a characteristic angle θ was defined to reflect the relative movement of soil particles. The relationship between principal stress ratio σ1/σ3 and characteristic angle θ and that between void ratio e and characteristic angle θ were derived. Subsequently, the relationship expression of stress ratio η (q/p) and void ratio e was established, and the trend of void ratio e with the stress path was studied. To describe the strain hardening and strain softening characteristics of gravelly sand in different stress paths, a new dilatancy equation was obtained by introducing the characteristic state stress ratio Mc into the dilatancy equation of the modified Cam-Clay model based on the state-dependent dilatancy theory. Finally, an elastoplastic constitutive model of gravelly sand was established by applying a nonassociate flow rule. All model parameters can be determined by triaxial shear tests under different stress paths, and the comparison results show that the proposed model can well reflect the mechanical behaviors of gravelly sand under different stress paths.

scholarly journals Effect of Stress Ratio on the Relationship between Fatigue Lives of Bovine Bone and Stress Frequency.

1998 ◽  
Vol 64 (619) ◽  
pp. 831-838 ◽  
Author(s):  
Sotomi ISHIHARA ◽  
Takahito GOSHIMA ◽  
Osamu NAGAMORI
Keyword(s):  
Stress Ratio ◽  
Bovine Bone ◽  
The Relationship
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