scholarly journals Modeling Wear for Heterogeneous Bi-Phasic Materials Using Discrete Elements Approach

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Matthieu Champagne ◽  
Mathieu Renouf ◽  
Yves Berthier
Keyword(s):  
Friction And Wear ◽  
Numerical Models ◽  
Real Life ◽  
Limited Range ◽  
Friction Material ◽  
Contact Interface ◽  
Discrete Elements ◽  
Proper Understanding ◽  
Scale Models ◽  
Automotive Brake

A proper understanding of the processes of friction and wear can only be reached through a detailed study of the contact interface. Empirical laws, such as Archard's, are often used in numerical models. They give good results over a limited range of conditions when their coefficients are correctly set, but they cannot be predicted: any significant change of conditions requires a new set of experimental coefficients. In this paper, a new method, the use of discrete element models (DEMs), is proposed in order to tend to predictable models. As an example, a generic biphasic friction material is modeled, of the type used in aeronautical or automotive brake systems. Micro-scale models are built in order to study material damage and wear under tribological stress. The models show what could be achieved by these numerical methods in tribological studies and how they can reproduce the behavior and mechanisms seen with real-life friction materials without any empirical law or parameter.

A Survey of the Present State of Friction Modelling in the Analytical and Numerical Investigation of Brake Noise Generation

1999 ◽  
Author(s):  
Jörg Wallaschek ◽  
Karl-Heinz Hach ◽  
Ulrich Stolz ◽  
Parimal Mody
Keyword(s):  
Friction And Wear ◽  
Numerical Models ◽  
Engineering Practice ◽  
Noise Generation ◽  
Noise And Vibration ◽  
Levels Of Detail ◽  
Key Issues ◽  
Brake Noise ◽  
Automotive Brake

Abstract Noise and vibration have become key issues in the design of automotive braking systems. Efforts to improve present day braking systems must take noise and vibration behaviour into account. Good knowledge of the mechanisms involved in the generation of brake noise has thus become an important competitive factor in the design of automotive brake systems. The present paper summarizes some facts and hypotheses concerning the generation of brake noise. First the different brake noise phenomena are classified. Then several approaches, including models of various levels of detail which have been suggested to explain the root causes of brake noise generation are discussed in detail. It will be pointed out that friction and wear processes at the interface of brake pad and rotor play an important role in the understanding of brake noise generation. Unfortunately, our present day knowledge on these processes is quite limited. Further research of basic processes is still needed to improve the quality of analytical and numerical models of friction and wear processes, before reliable predictions of brake noise generation become possible. Based on a discussion of simple models frequently used in engineering practice, guidelines for further research in tribological modelling of the interface processes in pad/rotor interaction will be formulated.

scholarly journals An Analytical and Numerical Study of Magnetic Spring Suspension with Energy Recovery Capabilities

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3126 ◽  
Author(s):  
Yu Jia ◽  
Shasha Li ◽  
Yu Shi
Keyword(s):  
Energy Recovery ◽  
Numerical Study ◽  
Numerical Models ◽  
Limited Range ◽  
Paradigm Shifts ◽  
Restoring Force ◽  
Highly Nonlinear ◽  
Spring Mechanism ◽  
Paved Road ◽  
Rider Comfort

As the automotive paradigm shifts towards electric, limited range remains a key challenge. Increasing the battery size adds weight, which yields diminishing returns in range per kilowatt-hour. Therefore, energy recovery systems, such as regenerative braking and photovoltaic cells, are desirable to recharge the onboard batteries in between hub charge cycles. While some reports of regenerative suspension do exist, they all harvest energy in a parasitic manner, and the predicted power output is extremely low, since the majority of the energy is still dissipated to the environment by the suspension. This paper proposes a fundamental suspension redesign using a magnetically-levitated spring mechanism and aims to increase the recoverable energy significantly by directly coupling an electromagnetic transducer as the main damper. Furthermore, the highly nonlinear magnetic restoring force can also potentially enhance rider comfort. Analytical and numerical models have been constructed. Road roughness data from an Australian road were used to numerically simulate a representative environment response. Simulation suggests that 10’s of kW to >100 kW can theoretically be generated by a medium-sized car travelling on a typical paved road (about 2–3 orders of magnitude higher than literature reports on parasitic regenerative suspension schemes), while still maintaining well below the discomfort threshold for passengers (<0.315 m/s 2 on average).

scholarly journals A Review of Progress and Applications of Pulsed Doppler Wind LiDARs

2019 ◽  
Vol 11 (21) ◽  
pp. 2522 ◽  
Author(s):  
Zhengliang Liu ◽  
Janet F. Barlow ◽  
Pak-Wai Chan ◽  
Jimmy Chi Hung Fung ◽  
Yuguo Li ◽  
...  
Keyword(s):  
Wind Energy ◽  
Numerical Models ◽  
Real Life ◽  
Doppler Lidar ◽  
Promising Alternative ◽  
3 Dimensional ◽  
In Situ Techniques ◽  
Energy Assessment ◽  
Wind Shears ◽  
Wind Profiles

Doppler wind LiDAR (Light Detection And Ranging) makes use of the principle of optical Doppler shift between the reference and backscattered radiations to measure radial velocities at distances up to several kilometers above the ground. Such instruments promise some advantages, including its large scan volume, movability and provision of 3-dimensional wind measurements, as well as its relatively higher temporal and spatial resolution comparing with other measurement devices. In recent decades, Doppler LiDARs developed by scientific institutes and commercial companies have been well adopted in several real-life applications. Doppler LiDARs are installed in about a dozen airports to study aircraft-induced vortices and detect wind shears. In the wind energy industry, the Doppler LiDAR technique provides a promising alternative to in-situ techniques in wind energy assessment, turbine wake analysis and turbine control. Doppler LiDARs have also been applied in meteorological studies, such as observing boundary layers and tracking tropical cyclones. These applications demonstrate the capability of Doppler LiDARs for measuring backscatter coefficients and wind profiles. In addition, Doppler LiDAR measurements show considerable potential for validating and improving numerical models. It is expected that future development of the Doppler LiDAR technique and data processing algorithms will provide accurate measurements with high spatial and temporal resolutions under different environmental conditions.

A retrofit for asbestos-based brake pad employing palm kernel fiber as the base filler material

2018 ◽  
Vol 233 (9) ◽  
pp. 1906-1913 ◽  
Author(s):  
CH Achebe ◽  
JL Chukwuneke ◽  
FA Anene ◽  
CM Ewulonu
Keyword(s):  
Specific Gravity ◽  
Palm Kernel ◽  
Friction Material ◽  
Mechanical Tests ◽  
Filler Material ◽  
Oil Absorption ◽  
Brake Pad ◽  
Brake Pads ◽  
The Matrix ◽  
Automotive Brake

The development of automobile brake pad using locally sourced palm kernel fiber was carried out. Asbestos, a carcinogenic material, has been used for decades as a friction material. This development has thus prompted a couple of research efforts geared towards its replacement for brake pad manufacture. Palm kernel fiber was used as an alternative filler material in conjunction with various quantities of epoxy resin as the matrix. Three sets of compositions were made, and the resulting specimens subjected to physical and mechanical tests using standard materials, procedures, and equipment. The essence is to determine their suitability and hence possible performance in service. The result showed that sample C with 40% palm kernel fiber content having hardness, compressive strength, abrasion resistance, specific gravity, water absorption, and oil absorption of 178 MPa, 96.2 MPa, 1.67 mg/m, 1.8 g/cm3, 1.86%, and 0.89%, respectively, had an optimum performance rating. It was equally ascertained that increase in the filler content had the effect of increase in hardness, wear resistance, and specific gravity of the composite brake pad, while water and oil absorption got decreased when compared with results obtained by other researchers using conventional brake pads made of other friction materials including asbestos. This is an indicator that palm kernel fiber is a possible and effective retrofit for asbestos as a filler material in automotive brake pad manufacture.

Numerical Simulation of Fretting Wear at the Dimple/Gimbal Interface

2013 ◽  
Author(s):  
Zhengqiang Tang ◽  
Youyi Fu ◽  
Frank E. Talke
Keyword(s):  
Friction And Wear ◽  
Disk Drive ◽  
Fretting Wear ◽  
Von Mises Stress ◽  
Experimental Measurements ◽  
Contact Interface ◽  
Surface Profiles ◽  
Von Mises ◽  
Worn Surface ◽  
Interface Geometry

A numerical model for the simulation of fretting wear at the dimple/gimbal interface of a hard disk drive suspension has been developed. The friction and wear coefficients used in the model are determined from experimental measurements. Archard’s wear equation is implemented numerically and the contact interface geometry is updated incrementally. The von Mises stress distribution and the worn surface profiles are determined.

Relating Friction in CMP to Topography Evolution

2005 ◽  
Author(s):  
Xiaolin Xie ◽  
Duane Boning
Keyword(s):  
Surface Topography ◽  
Integrated Circuit ◽  
Friction And Wear ◽  
Shallow Trench Isolation ◽  
Integrated Circuit Manufacturing ◽  
Scale Models ◽  
Trench Isolation ◽  
Model Predictions ◽  
Different Types ◽  
Dual Material

Die-scale models of chemical-mechanical polishing (CMP) have been previously reported for a number of different CMP processes used in integrated circuit manufacturing, including oxide, dual material shallow trench isolation, and dual material copper damascene processes. These models can dynamically predict the evolution of surface topography (e.g., local feature step heights, film thickness nonuniformity across the different pattern density regions of the chip, dishing, and erosion) for any time point during CMP. This topography evolution information can be applied to better understand the basis for observed friction and wear in the CMP process. In this work, we explore models of the macroscopic frictional force based on the surface topography. CMP endpoint measurements, such as those from motor current traces, enable verification of model predictions relating friction to CMP surface topography evolution, for different types of CMP processes and patterned chips.

scholarly journals Analogue earthquakes and seismic cycles: Experimental modelling across timescales

2016 ◽  
Author(s):  
Matthias Rosenau ◽  
Fabio Corbi ◽  
Stephane Dominguez
Keyword(s):  
Numerical Models ◽  
Experimental Modelling ◽  
Rupture Dynamics ◽  
Scale Models ◽  
Analogue Models ◽  
Elastic Rebound ◽  
Earthquake Modelling ◽  
Earthquake Model ◽  
Mechanical Models ◽  
Long Timescales

Abstract. Since the formulation of Reid’s elastic rebound theory 100 years ago laboratory mechanical models combining frictional and elastic elements have joined the forefront of the research on the dynamics of earthquakes. In the last decade, with the advent of high resolution monitoring techniques and new rock analogue materials, laboratory earthquake experiments kept developing from simple spring-slider models to more sophisticated scaled analogue models. This evolution was accomplished by advances in seismology and geodesy which, along with a culmination of large earthquakes, have significantly increased the quality and quantity of relevant observations in nature. We here review the cornerstones of analogue earthquake model developments with a focus on scale models which are directly comparable to observational data on short to long timescales. We revisit the basics of analogue modelling, namely scaling, materials and monitoring, as applied in earthquake modelling. An overview of applications highlights the contributions of analogue earthquake models in bridging timescales of observations including earthquake statistics, rupture dynamics, ground motion and seismic cycle deformation up to seismotectonic evolution. We finally discuss limits, challenges and links to numerical models.

High temperature friction and wear properties of graphene oxide/polytetrafluoroethylene composite coatings deposited on stainless steel

RSC Advances ◽  
2016 ◽  
Vol 6 (7) ◽  
pp. 5977-5987 ◽  
Author(s):  
N. Nemati ◽  
M. Emamy ◽  
S. Yau ◽  
J.-K. Kim ◽  
D.-E. Kim
Keyword(s):  
Stainless Steel ◽  
Graphene Oxide ◽  
Friction And Wear ◽  
Solid Lubricant ◽  
Composite Coatings ◽  
Friction Material ◽  
Wear Properties ◽  
Low Friction ◽  
Solid Lubricant Coating ◽  
Friction And Wear Properties

Polytetrafluoroethylene (PTFE) coating is known as a low friction material that is often used as a solid lubricant coating.

Experimental Modal Analysis: Efficient Geometry Model Creation Using Optical Techniques

2006 ◽  
Vol 49 (2) ◽  
pp. 104-113 ◽  
Author(s):  
Steven Pauwels ◽  
Jan Debille ◽  
Jeff Komrower ◽  
Jenny Lau
Keyword(s):  
Modal Analysis ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Real Life ◽  
Geometrical Model ◽  
Experimental Modal Analysis ◽  
Modal Parameter ◽  
Optical Techniques ◽  
Geometry Model ◽  
Modal Parameter Estimation

Experimental modal analysis (EMA) is widely used to characterize the dynamic properties of structures. Recently EMA is being used on more complex structures often involving hundreds of measurement points. Modal analysis results are frequently used in combination with numerical models, imposing higher standards on the quality of the modal parameter estimation and the accuracy of the geometry models. These requirements are often contradictory to the availability of test cells and prototypes. In order to solve this challenge, innovative solutions using optical techniques have been developed that simplify and accelerate the creation of a geometrical model of a test object, while at the same time increase the accuracy of measured coordinates. Industrial applicability of these techniques is proven by a number of benchmarks on real-life structures.

The effect of boron on the performance of automotive brake

2013 ◽  
Vol 10 (6) ◽  
pp. 523-528 ◽  
Author(s):  
A. Muzathik ◽  
Y. Nizam ◽  
M. Ahmad ◽  
W. Nik
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Friction Material ◽  
Brake System ◽  
Brake Pad ◽  
Brake Pads ◽  
Brake Performance ◽  
Single Material ◽  
Automotive Brake

Friction material in an automotive brake system plays an important role for effective and safe brake performance. A single material has never been sufficient to solve performance related issues. Current research aimed to examine properties of Boron mixed brake pads by comparing them with the commercial brake pads. Friction coefficient of Boron mixed brake pads and commercial brake pads were significantly different and increased with the increase in surface roughness. The abrupt reduction of friction coefficient is more significant in commercial brake pad samples than in Boron mixed brake pad formulations. Fade occurred in commercial brake pad sample at lower temperatures. Boron formulations are more stable than their commercial counterparts.

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