Dissipation of Mechanical Energy in an Oscillating Adhesive Contact between a Hard Indenter and an Elastomer

2020 ◽  
Vol 46 (11) ◽  
pp. 1092-1095
Author(s):  
I. A. Lyashenko ◽  
V. L. Popov
Keyword(s):  
Mechanical Energy ◽  
Adhesive Contact

Coefficients of Restitution in Normal Adhesive Impact between Smooth and Rough Elastic Bodies

2020 ◽  
Vol 1 (1) ◽  
pp. 103-109
Author(s):  
Valentin L. Popov ◽  
Keyword(s):  
Energy Dissipation ◽  
Rough Surface ◽  
Mechanical Energy ◽  
Rolling Friction ◽  
Adhesive Contact ◽  
Dissipated Energy ◽  
Microscopic Scale ◽  
Elastic Bodies ◽  
Rear Part ◽  
The Moment

n 1975, Fuller and Tabor have shown that roughness can destroy macroscopic adhesion. This means that in spite of the presence of adhesion at the microscopic scale, the macrosopic force of adhesion vanishes. The mechanism of vanishing macroscopic adhesion is very simple: during approach of elastic bodies, asperities are elastically deformed so strongly that after unloading they destroy the microscopic adhesive junctions. However, both in the moment of formation of microscopic adhesive junctions in the loading phase and their destruction during unloading, mechanical energy disappears. This means that the microscopic adhesion makes the contact dissipative even if there is no macroscopic force of adhesion. In particular, the force-distance dependency during indentation and pull-off do not coincide with each other showing some "adhesive hysteresis". When a ball rolls on such rough surface, there will be a final energy dissipation due to formation of a new contact at the frontline of the contact and its destruction at the rear part. Thus, microscopic adhesion will lead to appearance of rolling friction in an apparently non-adhesive contact. In the present paper, we calculate the approach and pull-off dependencies of force on distance, the dissipated energy in one loading-unloading cycle and estimate the force of rolling friction due to microscopic adhesion.

scholarly journals Adhesive Hysteresis and Rolling Friction in Rough "Non-Adhesive" Contacts

2020 ◽  
Author(s):  
Valentin L. Popov
Keyword(s):  
Energy Dissipation ◽  
Mechanical Energy ◽  
Rolling Friction ◽  
Adhesive Contact ◽  
Dissipated Energy ◽  
Microscopic Scale ◽  
Elastic Bodies ◽  
Rear Part ◽  
The Moment ◽  
Adhesive Contacts

In 1975, Fuller and Tabor have shown that roughness can destroy macroscopic adhesion. This means that in spite of the presence of adhesion at the microscopic scale, the macrosopic force of adhesion vanishes. The mechanism of vanishing macroscopic adhesion is very simple: during approach of elastic bodies, asperities are elastically deformed so strongly that after unloading they destroy the microscopic adhesive junctions. However, both in the moment of formation of microscopic adhesive junctions in the loading phase and their destruction during unloading, mechanical energy disappears. This means that the microscopic adhesion makes the contact dissipative even if there is no macroscopic force of adhesion. In particular, the force-distance dependency during indentation and pull-off do not coincide with each other showing some "adhesive hysteresis". When a ball rolls on such rough surface, there will be a final energy dissipation due to formation of a new contact at the frontline of the contact and its destruction at the rear part. Thus, microscopic adhesion will lead to appearance of rolling friction in an apparently non-adhesive contact. In the present paper, we calculate the approach and pull-off dependencies of force on distance, the dissipated energy in one loading-unloading cycle and estimate the force of rolling friction due to microscopic adhesion.

Reduction of structural vibrations with the piezoelectric stacks ring

2020 ◽  
Vol 64 (1-4) ◽  
pp. 729-736
Author(s):  
Jincheng He ◽  
Xing Tan ◽  
Wang Tao ◽  
Xinhai Wu ◽  
Huan He ◽  
...  
Keyword(s):  
Vibration Control ◽  
Mechanical Energy ◽  
Electrical Energy ◽  
Structural Vibrations ◽  
Rotor Systems ◽  
Fea Model ◽  
Piezoelectric Stacks ◽  
Shunt Damping ◽  
Reduction Effect ◽  
Euler Bernoulli Beam

It is known that piezoelectric material shunted with external circuits can convert mechanical energy to electrical energy, which is so called piezoelectric shunt damping technology. In this paper, a piezoelectric stacks ring (PSR) is designed for vibration control of beams and rotor systems. A relative simple electromechanical model of an Euler Bernoulli beam supported by two piezoelectric stacks shunted with resonant RL circuits is established. The equation of motion of such simplified system has been derived using Hamilton’s principle. A more realistic FEA model is developed. The numerical analysis is carried out using COMSOL® and the simulation results show a significant reduction of vibration amplitude at the specific natural frequencies. Using finite element method, the influence of circuit parameters on lateral vibration control is discussed. A preliminary experiment of a prototype PSR verifies the PSR’s vibration reduction effect.

CLINICAL AND NEUROLOGICAL FEATURES OF TRAUMATIC BRAIN DISEASE DURING THE STAGES OF REHABILITATION

2020 ◽  
Vol 3 (1) ◽  
pp. 51-53
Author(s):  
Rano Azizova ◽  
◽  
Umida Shamsiyeva ◽  
Mirzohid Turabbayev ◽  
Begzod Jorayev ◽  
...  
Keyword(s):  
Mechanical Energy ◽  
Pathological Process ◽  
Brain Disease ◽  
Clinical Forms ◽  
Neurological Features ◽  
Mechanisms Of Development ◽  
The Brain

Traumatic brain disease (TBHD) is a pathological process triggered by the damaging effect of mechanical energy on the brain and is characterized — with a variety of clinical forms — by the unity of etiology, pathogenetic and sanogenetic mechanisms of development and outcomes.

Energy dissipation rate in a baffled vessel with pitched blade turbine impeller

1991 ◽  
Vol 56 (9) ◽  
pp. 1856-1867 ◽  
Author(s):  
Zdzisław Jaworski ◽  
Ivan Fořt
Keyword(s):  
Energy Dissipation ◽  
Cross Sections ◽  
Mechanical Energy ◽  
Vessel Diameter ◽  
Energy Dissipation Rate ◽  
Mean Velocity ◽  
Agitated Vessel ◽  
Radial Profiles ◽  
Pitched Blade Turbine ◽  
Turbine Impeller

Mechanical energy dissipation was investigated in a cylindrical, flat bottomed vessel with four radial baffles and the pitched blade turbine impeller of varied size. This study was based upon the experimental data on the hydrodynamics of the turbulent flow of water in an agitated vessel. They were gained by means of the three-holes Pitot tube technique for three impeller-to-vessel diameter ratio d/D = 1/3, 1/4 and 1/5. The experimental results obtained for two levels below and two levels above the impeller were used in the present study. Radial profiles of the mean velocity components, static and total pressures were presented for one of the levels. Local contribution to the axial transport of the agitated charge and energy was presented. Using the assumption of the axial symmetry of the flow field the volumetric flow rates were determined for the four horizontal cross-sections. Regions of positive and negative values of the total pressure of the liquid were indicated. Energy dissipation rates in various regions of the agitated vessel were estimated in the range from 0.2 to 6.0 of the average value for the whole vessel. Hydraulic impeller efficiency amounting to about 68% was obtained. The mechanical energy transferred by the impellers is dissipated in the following ways: 54% in the space below the impeller, 32% in the impeller region, 14% in the remaining part of the agitated liquid.

Injuries and Occupational Safety

2017 ◽  
Author(s):  
Dawn N. Castillo ◽  
Timothy J. Pizatella ◽  
Nancy A. Stout
Keyword(s):  
United States ◽  
Ionizing Radiation ◽  
Occupational Safety ◽  
Occupational Injury ◽  
Occupational Injuries ◽  
Mechanical Energy ◽  
The United States ◽  
Hierarchical Approach ◽  
Safety Hazards ◽  
Injury Control

This chapter describes occupational injuries and their prevention. It describes in detail the causes of injuries and epidemiology of injuries. Occupational injuries are caused by acute exposure in the workplace to safety hazards, such as mechanical energy, electricity, chemicals, and ionizing radiation, or from the sudden lack of essential agents, such as oxygen or heat. This chapter describes the nature and the magnitude of occupational injuries in the United States. It provides data on risk of injuries in different occupations and industries. Finally, it discusses prevention of injuries, using a hierarchical approach to occupational injury control.

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