Thermal stress effects on the surface durability of gear teeth

2001 ◽  
Vol 215 (8) ◽  
pp. 973-979 ◽  
Author(s):  
A Seireg
Keyword(s):  
Thermal Stress ◽  
Operating Conditions ◽  
Machining Processes ◽  
Coating Technology ◽  
Gear Teeth ◽  
Stress Effects ◽  
Lubricating Film ◽  
Potential Benefits ◽  
Surface Durability ◽  
Stress Cycling

The current standards and design relationships for the surface durability of gears are based on contact stress considerations. Thermal effects are considered only for scoring failures resulting from the destruction of the lubricating film owing to temperature rise. This paper investigates the effect of thermal shock and thermal stress cycling on pitting, micropitting and wear for different gear geometries, materials, operating conditions, machining processes and surface treatments. Because of the current interest in applying surface coating technology to gears, special attention is given to illustrating the potential benefits of this technology in improving the performance and extending the life of gears.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Behzad ◽  
Benjamin Herrmann ◽  
Williams R. Calderón-Muñoz ◽  
José M. Cardemil ◽  
Rodrigo Barraza
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Steady State ◽  
Discrete Model ◽  
Continuum Model ◽  
Transient State ◽  
Operating Conditions ◽  
Steady State Condition ◽  
Content Type ◽  
The Continuum

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress. Design/methodology/approach The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events. Findings The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions. Originality/value Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

scholarly journals Long-Term Stability of Ferroelectret Energy Harvesters

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 42 ◽  
Author(s):  
Muhammed Kayaharman ◽  
Taylan Das ◽  
Gregory Seviora ◽  
Resul Saritas ◽  
Eihab Abdel-Rahman ◽  
...  
Keyword(s):  
Output Power ◽  
Operating Conditions ◽  
Constant Stress ◽  
Center Frequency ◽  
Term Stability ◽  
Energy Harvesters ◽  
Long Term Stability ◽  
Stress Cycling ◽  
Piezoelectric Charge

Cellular polypropylene (PP) has been recently used in energy harvesting applications. In this work, we investigate its viability and long-term stability under various operating conditions. Specifically, the effect of constant stress and stress cycling on output power and long-term stability of ferroelectret energy harvesters is analyzed. Our findings show that after 112 days constant stress significantly increases the piezoelectric charge constant d 33 and output power from 0.51 μW for a stress-free harvester to 2.71 μW. It also increases the harvester center frequency from 450 to 700 Hz and decreases its optimal resistance from 7 to 5.5 M Ω .

scholarly journals Improving the Performance of Process Controllers Using a New Clustered Neural Network

2011 ◽  
Vol 1 ◽  
pp. 273-277
Author(s):  
M. Reza Soleymani Yazdi ◽  
Michel Guillot
Keyword(s):  
Neural Network ◽  
Multilayer Perceptron ◽  
Operating Conditions ◽  
Machining Processes ◽  
Workpiece Material ◽  
Control Scheme ◽  
Organization Capacity ◽  
First Results ◽  
On Line ◽  
Neuro Controller

This paper presents first a newly developed clustered neural network, which incorporates self-organization capacity into the well-known common multilayer perceptron (MLP) architecture. With this addition, it is possible to reduce significantly overall memory degradation of the neuro-controller during on-line training. In the second part of the paper, this clustered multilayer perceptron (CMLP) network is applied and compared to the MLP through modeling and simulations of machining processes. Simulation results presented using machining data demonstrate that the CMLP possesses more powerful modeling capacity than the standard MLP, offers better adaptability to new operating conditions, and finally performs more reliably. During on-line training with machining data about 65% degradation of previously learned information can be observed in the MLP as opposed to only 11% for the CMLP. Finally, an adaptive control scheme intended for on-line optimization of the machining processes is presented. This scheme uses a feed forward CMLP inverse neuro-controller which learns off-line and on-line the relationships between process inputs and output under simulated perturbations (i.e., tool wear and non-homogeneous workpiece material properties). The first results using the CMLP inverse neuro-controller are promising

Thermal Stress Analysis/Life Prediction of Concentrating Photovoltaic Module

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. Cao ◽  
S. Butler ◽  
J. T. Benoit ◽  
Y. Jiang ◽  
R. Radhakrishnan ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Steady State ◽  
Aluminum Nitride ◽  
Stress Analysis ◽  
Fatigue Test ◽  
Heat Sink ◽  
Structural Integrity ◽  
Operating Conditions ◽  
Thermal Stress Analysis ◽  
Pv Cell

Aiming at understanding the structural integrity of two representative concentrating photovoltaic (CPV) module configurations, finite element thermal stress analysis is carried out in this investigation. This study covers the nominal and extreme operating conditions, including system startup and shutdown. While the first CPV module is bonded by epoxy-type material, the bonding material for the second CPV module is lead-free solder. The analysis of the first module confirms that this CPV module can endure the thermal stress under steady-state operation. However, residual stress analysis shows that the epoxy holding together the PV cell/aluminum nitride and aluminum nitride/heat sink pairs will likely break, first at some sporadic spots, and then in a good part of the bond causing the failure of the CPV module, as the cell temperature drops from 100°Cto0°C. Nonlinear viscoplastic analysis using the temperature profile of CPV cell fatigue test ongoing at United Technologies Research Center (UTRC) is performed to evaluate the structure strength and subsequently predict the life of the second CPV module. The result reveals that the maximum characteristic stresses of the PV cell components and heat sink are below the strength allowable for the corresponding materials under both the steady-state and overnight idle conditions. Critical locations on the solder that are potentially susceptible to structural failure after a few thousand thermal cycles due to the excessive shear stress are identified. A rough estimation of the module life is provided and compared with the fatigue test. This investigation provides firsthand understanding of the structural integrity of CPV modules and is thus beneficial for the solar energy community.

Paper 13: Cavitation and Viscosity between Plain Annular Thrust Surfaces

1967 ◽  
Vol 182 (14) ◽  
pp. 107-111
Author(s):  
B. S. Nau
Keyword(s):  
Shear Rate ◽  
Effective Viscosity ◽  
Thrust Bearing ◽  
Threshold Value ◽  
Mineral Oil ◽  
Operating Conditions ◽  
Shear Stresses ◽  
Face Seal ◽  
Lubricating Film ◽  
The Mean

The configuration investigated corresponds to that of a face-seal or ungrooved parallel-face thrust bearing. Film thicknesses and temperatures, and shear stresses were measured for various operating conditions with mineral oil supplied at low pressure to the inner edges of the annuli. Analysis of the experimental results confirms the importance of the bearing parameter, 6ηω02/ h02, in determining the load carried hydrodynamically. At a given temperature the mean effective viscosity of the lubricating film depends on the shear rate, for values in the range 106–107 s–1, decreasing linearly above a threshold value. The cause of this phenomenon is believed to be cavitation occurring in the film.

Thermal stress effects on Dye-Sensitized Solar Cells (DSSCs)

2011 ◽  
Vol 51 (9-11) ◽  
pp. 1762-1766 ◽  
Author(s):  
D. Bari ◽  
N. Wrachien ◽  
R. Tagliaferro ◽  
S. Penna ◽  
T.M. Brown ◽  
...  
Keyword(s):  
Solar Cells ◽  
Thermal Stress ◽  
Dye Sensitized Solar Cells ◽  
Stress Effects ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

scholarly journals Thermal Fatigue under Pulsating Thermal Stress Cycling

1962 ◽  
Vol 28 (191) ◽  
pp. 800-807 ◽  
Author(s):  
Shuji TAIRA ◽  
Masateru OHNAMI ◽  
Tetuo KYOGOKU
Keyword(s):  
Thermal Stress ◽  
Thermal Fatigue ◽  
Stress Cycling
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