Thermal Modeling and Effects From Debris Particles in Sliding/Rolling EHD Line Contacts—A Possible Local Scuffing Mode

1999 ◽  
Vol 121 (2) ◽  
pp. 272-281 ◽  
Author(s):  
G. K. Nikas ◽  
E. loannides ◽  
R. S. Sayles
Keyword(s):  
Theoretical Studies ◽  
Third Body ◽  
The Past ◽  
Local Material ◽  
Debris Particles ◽  
Asperity Contacts ◽  
Line Contacts ◽  
Machine Elements ◽  
Soft Particles ◽  
Local Material Properties

The damage caused by debris particles in concentrated contacts has been studied extensively in the past, both theoretically and experimentally. Most of the theoretical studies, in which the damage on the surfaces was calculated in the form of dents, were performed isothermally. It is known that sliding asperity contacts, which resemble third body contacts, reach high local temperatures that can affect local material properties which, in turn, will affect the way damage is generated on the surfaces of machine elements. In the present work the heat transfer of lubricated, rolling/sliding line contacts in the presence of a ductile spherical particle is modeled. The particle is assumed to be significantly softer than the counterfaces that squash it. The local flash temperatures due to the combined sliding and squashing of a debris particle are calculated. It is found that high temperatures caused from small and soft particles are rather the rule than the exception.

An Advanced Model to Study the Possible Thermomechanical Damage of Lubricated Sliding-Rolling Line Contacts From Soft Particles

2000 ◽  
Vol 123 (4) ◽  
pp. 828-841 ◽  
Author(s):  
George K. Nikas
Keyword(s):  
Thermal Stresses ◽  
Frictional Heating ◽  
Influential Factors ◽  
Plastic Compression ◽  
Lubricated Contacts ◽  
Debris Particles ◽  
Line Contacts ◽  
Soft Particles ◽  
Thermomechanical Damage ◽  
Advanced Model

A model presented earlier by the author (Nikas et al., 1998, 1999) for the study of the possible risks associated with the entrapment of debris particles in lubricated contacts has been refined to account for additional influential factors that could affect the results obtained from the initial model. The new results showed that soft contaminants could indeed be very destructive and damage a concentrated sliding contact mainly due to the thermal stresses developed from the frictional heating of the contact during the plastic compression and shearing of a particle. This model yielded flash temperatures of the order of 100°C and up to 2000°C (or more, until local yield occurs). It also showed that it is often the thermal stresses which cause the problems, rather than the mechanical stresses from particles’ deformation.

Effects of debris particles in sliding/rolling elastohydrodynamic contacts

1998 ◽  
Vol 212 (5) ◽  
pp. 333-343 ◽  
Author(s):  
G. K. Nikas ◽  
R. S. Sayles ◽  
E loannides
Keyword(s):  
Failure Modes ◽  
Effective Means ◽  
High Heat ◽  
Local Melting ◽  
Theoretical Simulation ◽  
Debris Particles ◽  
Asperity Contacts ◽  
Machine Elements ◽  
And Performance ◽  
Inlet Zone

A theoretical simulation of the behaviour of debris particles in elastohydrodynamic (EHD) contacts is an effective means for obtaining information regarding the life and performance of lubricated machine elements compared with costly experimentation. The present work indicates that debris particles are often responsible for two failure modes: (a) scuffing caused by particle agglomeration in the inlet zone of an EHD contact and (b) local melting due to high heat produced by the friction of debris in sliding contacts. The present predictions are in agreement with experimental evidence in two ways: firstly, in that EHD contacts may fail because of scuffing if the lubricant becomes contaminated, where the failure due to inlet blockage by debris and eventually fluid starvation, and, secondly, in that sliding asperity contacts encounter high flash temperatures which may cause local melting and thus plastic deformations.

scholarly journals Bending tests on GLT beams having well-known local material properties

2014 ◽  
Vol 48 (11) ◽  
pp. 3571-3584 ◽  
Author(s):  
Gerhard Fink ◽  
Andrea Frangi ◽  
Jochen Kohler
Keyword(s):  
Material Properties ◽  
Bending Tests ◽  
Local Material ◽  
Local Material Properties

Gradient-Free Optimization in Thermoacoustics: Application to A Low-Order Model

2021 ◽  
Author(s):  
Johann Moritz Reumschüssel ◽  
Jakob G. R. von Saldern ◽  
Yiqing Li ◽  
Christian Oliver Paschereit ◽  
Alessandro Orchini
Keyword(s):  
Optimization Algorithms ◽  
Optimization Methods ◽  
Theoretical Studies ◽  
Order Model ◽  
Output Data ◽  
Fuel Injectors ◽  
Solution Strategies ◽  
The Past ◽  
Downhill Simplex ◽  
Low Order

Abstract Machine learning and automatized routines for parameter optimization have experienced a surge in development in the past years, mostly caused by the increasing availability of computing capacity. Gradient-free optimization can avoid cumbersome theoretical studies as input parameters are purely adapted based on output data. As no knowledge about the objective function is provided to the algorithms, this approach might reveal unconventional solutions to complex problems that were out of scope of classical solution strategies. In this study, the potential of these optimization methods on thermoacoustic problems is examined. The optimization algorithms are applied to a generic low-order thermoacoustic can-combustor model with several fuel injectors at different locations. We use three optimization algorithms — the well established Downhill Simplex Method, the recently proposed Explorative Gradient Method, and an evolutionary algorithm — to find optimal fuel distributions across the fuel lines while maintaining the amount of consumed fuel constant. The objective is to have minimal pulsation amplitudes. We compare the results and efficiency of the gradient-free algorithms. Additionally, we employ model-based linear stability analysis to calculate the growth rates of the dominant thermoacoustic modes. This allows us to highlight general and thermoacoustic-specific features of the optimization methods and results. The findings of this study show the potential of gradient-free optimization methods on combustor design for tackling thermoacoustic problems, and motivate further research in this direction.

Consideration of Parameter Scattering in Thermo-Mechanical Characterization of Advanced Packages

1999 ◽  
Vol 121 (4) ◽  
pp. 282-285 ◽  
Author(s):  
T. Winkler ◽  
A. Schubert ◽  
E. Kaulfersch ◽  
B. Michel
Keyword(s):  
Finite Element ◽  
Life Time ◽  
Electronic Packages ◽  
Element Determination ◽  
Local Material ◽  
Element Simulation ◽  
Geometrical Imperfections ◽  
Element Approach ◽  
Partial Randomness ◽  
Local Material Properties

Much progress has been made in the simulation and verification of the thermo-mechanical behavior of plastic packages. On the other hand, until now there is a lack in the consideration of the scatter or uncertainty, respectively, of certain characteristics. A comparatively large scatter of local material properties or random geometrical imperfections can often be observed within the material compounds of electronic packages. The partial randomness of certain input parameters creates uncertainties in the finite element determination of mechanical quantities which are provided for thermo-mechanical reliability optimization and life time prediction. In the following the STOFEM stochastic finite element approach based on perturbation theory is applied as a part of the finite element simulation. It is used to find out some additional effects arising from uncertainties in the modeling, slightly varying parameters or probabilistic influences, respectively. In a second part of the paper, another approach to the consideration of random variations is discussed. It is based on the randomization of initially deterministic relations.

scholarly journals Dragos Gheorghiu, Livia Stefan, Immersing into the Past: an Augmented Reality Method to Link Tangible and Intangible Heritage

2020 ◽  
Vol 8 (2) ◽  
pp. 91-102
Author(s):  
Dragos Gheorghiu ◽  
Livia Stefan
Keyword(s):  
Augmented Reality ◽  
Research Work ◽  
Modern Method ◽  
Sufficient Information ◽  
Efficient Manner ◽  
The Past ◽  
Intangible Heritage ◽  
Points Of Interest ◽  
Local Material ◽  
World Information

The current IT and digital technologies such as Mobile Augmented Reality (MAR) enable the overlap of digital and real world information in relation with a topic, in an engaging and efficient manner, and therefore can be used to store intangible heritage and to study it in the context as well. The current paper refers to such an augmentation of cultural information, performed at the Kallatis site, whose ruins, at present mostly covered by the modern town, do not offer sufficient information on the complexity of the Greek civilization. The implementation of a MAR application consisted in defining several points of interest of the important local archaeologic discoveries, which can trigger, for the visitors using our application, an augmentation of the historical site with images and videos. With the current research work, the authors propose and demonstrate that a mobile MAR application can constitute a modern method for providing visitors with an immersive and holistic experience for understanding the local material and intangible heritage.

scholarly journals Characterizing the Local Material Properties of Different Fe–C–Cr-Steels by Using Deep Rolled Single Tracks

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4987
Author(s):  
Nicole Wielki ◽  
Noémie Heinz ◽  
Daniel Meyer
Keyword(s):  
Deep Rolling ◽  
Track Geometry ◽  
Material Development ◽  
State Dependent ◽  
Local Material ◽  
Material State ◽  
Aisi 1045 ◽  
Cr System ◽  
Machining Operations ◽  
Local Material Properties

As part of a novel method for material development, deep rolling was used in this work to characterize the mechanical properties of macroscopic specimens of C45 (AISI 1045), S235 (AISI 1015), and 100Cr6 (AISI 52100) in various heat treatment states. Deep rolling is conventionally used to enhance surface and subsurface properties by reducing the surface roughness, introducing compressive residual stresses, and strain hardening. In the context of this work, it was utilized to determine material-specific variables via a mechanically applied load. For that purpose, the geometries of individual deep rolled tracks were measured. In dependence of the process parameters such as deep rolling pressure and tool size, the track geometry, i.e., the specific track depth, was for the first time compared for different materials. A functional relationship identified between the specific track depth and the material state dependent hardness forms the basis for a future characterization of the properties of alloy compositions belonging to the Fe–C–Cr system. Since deep rolling is performed in the same clamping as machining operations, hardness alterations could easily be determined at different points in the process chain using an optical in-process measurement of track geometries in the future.

A Description of Local Material Properties Close to a Butt Weld

2013 ◽  
Vol 586 ◽  
pp. 146-149
Author(s):  
Pavel Hutař ◽  
Martin Ševčík ◽  
Ralf Lach ◽  
Zdeněk Knésl ◽  
Luboš Náhlík ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Material Properties ◽  
Radial Crack ◽  
Welded Joint ◽  
Butt Weld ◽  
Pipe System ◽  
Local Material ◽  
Mechanics Analysis ◽  
Welding Procedure ◽  
Local Material Properties

The paper presents a methodology for the lifetime assessment of welded polymer pipes. A fracture mechanics analysis of a butt-welded joint is performed by simulating radial crack growth in the nonhomogenous region of the pipe weld. It was found that the presence of material nonhomogeneity in the pipe weld caused by the welding procedure leads to an increase in the stress intensity factor of the radial crack and changes the usual failure mode of the pipe system. This can lead to a significant reduction in the lifetime of the pipe system.

scholarly journals Combining adhesive contact mechanics with a viscoelastic material model to probe local material properties by AFM

Soft Matter ◽  
2018 ◽  
Vol 14 (1) ◽  
pp. 140-150 ◽  
Author(s):  
Christian Ganser ◽  
Caterina Czibula ◽  
Daniel Tscharnuter ◽  
Thomas Schöberl ◽  
Christian Teichert ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Material Model ◽  
Adhesive Contact ◽  
Force Microscopy ◽  
Atomic Force ◽  
Local Material ◽  
Local Material Properties

We present an atomic force microscopy based method to study viscoelastic material properties at low indentation depths with non-negligible adhesion and surface roughness.

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