scholarly journals Evolution of real area of contact due to combined normal load and sub-surface straining in sheet metal

Friction ◽  
2020 ◽  
Author(s):  
Meghshyam Shisode ◽  
Javad Hazrati ◽  
Tanmaya Mishra ◽  
Matthijn De Rooij ◽  
Ton Van Den Boogaard
Keyword(s):  
Sheet Metal ◽  
Friction And Wear ◽  
Normal Load ◽  
Contact Forces ◽  
Surface Strain ◽  
Material Behavior ◽  
The Real ◽  
Real Area Of Contact ◽  
Macro Scale ◽  
Real Area

Abstract Understanding asperity flattening is vital for a reliable macro-scale modeling of friction and wear. In sheet metal forming processes, sheet surface asperities are deformed due to contact forces between the tools and the workpiece. In addition, as the sheet metal is strained while retaining the normal load, the asperity deformation increases significantly. Deformation of the asperities determines the real area of contact which influences the friction and wear at the tool-sheet metal contact. The real area of contact between two contacting rough surfaces depends on type of loading, material behavior, and topography of the contacting surfaces. In this study, an experimental setup is developed to investigate the effect of a combined normal load and sub-surface strain on real area of contact. Uncoated and zinc coated steel sheets (GI) with different coating thicknesses, surface topographies, and substrate materials are used in the experimental study. Finite element (FE) analyses are performed on measured surface profiles to further analyze the behavior observed in the experiments and to understand the effect of surface topography, and coating thickness on the evolution of the real area of contact. Finally, an analytical model is presented to determine the real area contact under combined normal load and sub-surface strain. The results show that accounting for combined normal load and sub-surface straining effects is necessary for accurate predictions of the real area of contact.

Multi-Scale Contact Modeling of Coated Steels for Sheet Metal Forming Applications

2018 ◽  
Vol 767 ◽  
pp. 223-231 ◽  
Author(s):  
Meghshyam Shisode ◽  
Javad Hazrati ◽  
Tanmaya Mishra ◽  
Matthijn de Rooij ◽  
Ton van den Boogaard
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Normal Load ◽  
Steel Substrate ◽  
Surface Textures ◽  
The Real ◽  
Multi Scale ◽  
Real Area Of Contact ◽  
Real Area

Friction in sheet metal forming is a local phenomenon which depends on continuously evolving contact conditions during the forming process. This is mainly influenced by local contact pressure, surface textures of the sheet metal as well as the forming tool surface profile and material behavior. The first step for an accurate prediction of friction is to reliably estimate real area of contact at various normal loads. In this study, a multi-scale contact model for the normal load is presented to predict asperity deformation in coated steels and thus to estimate the real area of contact. Surface profiles of the zinc layer and steel substrate are modelled explicitly obtained from confocal measurements. Different mechanical properties are assigned to the zinc coating and the steel substrate. The model was calibrated and validated relative to lab-scale normal load tests using different samples of zinc coated steel with distinct surface textures. The results show that the model is able to predict the real area of contact in zinc-coated steels for various contact pressures and different surface textures. Current multi-scale model can be used to determine the local friction coefficient in sheet metal forming processes more accurately.

The Effect of Nanoparticles on the Real Area of Contact, Friction, and Wear

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Hamed Ghaednia ◽  
Robert L. Jackson
Keyword(s):  
Friction And Wear ◽  
Silicon Nanoparticles ◽  
Rough Surfaces ◽  
Contact Friction ◽  
Body Contact ◽  
The Real ◽  
Real Area Of Contact ◽  
The Coefficient Of Friction ◽  
Real Area ◽  
Nanoparticle Additives

Although nanoparticle additives have been the topic of multiple studies recently, very little work has attempted to explicitly model the third body contact of nanoparticles. This work presents and uses a novel methodology to model nanoparticles in contact between rough surfaces. The model uses two submodels to handle different scales of contact, namely the nano-sized particles and micrometer-sized roughness features. Silicon nanoparticles suspended in conventional lubricant are modeled in contact between steel rough surfaces. The effect of the particles on contact force and real area of contact has been modeled. The model makes predictions of the coefficient of friction and wear using fundamental models. The results suggest that particles would reduce the real area of contact and, therefore, decrease the friction force. Also, particles could induce abrasive wear by scratching the surfaces. The implications of the model are also discussed, and the arguments and results have been linked to available experimental data. This work finds that particle size and distribution are playing a key role in tribology characteristics of the nanolubricants.

Analysis of the Real Area of Contact Between a Polymeric Magnetic Medium and a Rigid Surface

1984 ◽  
Vol 106 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Bharat Bhushan
Keyword(s):  
Complex Modulus ◽  
Critical Value ◽  
Computer Applications ◽  
Hard Material ◽  
Rigid Surface ◽  
Magnetic Medium ◽  
The Real ◽  
Real Area Of Contact ◽  
The Mean ◽  
Real Area

The statistical analysis of the real area of contact proposed by Greenwood and Williamson is revisited. General and simplified equations for the mean asperity real area of contact, number of contacts, total real area of contact, and mean real pressure as a function of apparent pressure for the case of elastic junctions are presented. The critical value of the mean asperity pressure at which plastic flow starts when a polymer contacts a hard material is derived. Based on this, conditions of elastic and plastic junctions for polymers are defined by a “polymer” plasticity index, Ψp which depends on the complex modulus, Poisson’s ratio, yield strength, and surface topography. Calculations show that most dynamic contacts that occur in a computer-magnetic tape are elastic, and the predictions are supported by experimental evidence. Tape wear in computer applications is small and decreases Ψp by less than 10 percent. The theory presented here can also be applied to rigid and floppy disks.

Contact Mechanics of Rough Surfaces in Tribology: Single Asperity Contact

1996 ◽  
Vol 49 (5) ◽  
pp. 275-298 ◽  
Author(s):  
Bharat Bhushan
Keyword(s):  
Friction And Wear ◽  
Rough Surfaces ◽  
Asperity Contact ◽  
Elastic Solids ◽  
Elastic Plastic ◽  
Single Asperity ◽  
Real Area Of Contact ◽  
Single Asperity Contact ◽  
Indentation Problem ◽  
Real Area

Contact modeling of two rough surfaces under normal approach and with relative motion is carried out to predict the real area of contact which affects friction and wear of an interface. The contact of two macroscopically flat bodies with microroughness is reduced to the contact at multiple asperities of arbitrary shapes. Most of deformation at the asperity contact can be either elastic or elastic-plastic. In this paper, a comprehensive review of modeling of a single asperity contact or an indentation problem is presented. Contact analyses for a spherical asperity/indenter on homogeneous and layered, elastic and elastic-plastic solids with and without tangential loading are presented. The analyses reviewed in this paper fall into two groups: (a) analytical solutions, primarily for elastic solids and (b) finite element solutions, primarily for elastic-plastic problems and layered solids. Implications of these analyses in friction and wear are discussed.

A Relationship Between Autocorrelation Length and Adhesive Friction Behavior of Rough Surfaces

2005 ◽  
Author(s):  
Yilei Zhang ◽  
Sriram Sundararajan
Keyword(s):  
Rough Surface ◽  
Spatial Information ◽  
Roughness Parameter ◽  
Hertzian Contact ◽  
Root Mean Square Roughness ◽  
Friction Behavior ◽  
The Real ◽  
Real Area Of Contact ◽  
Autocorrelation Length ◽  
Real Area

Autocorrelation Length (ACL) is a surface roughness parameter that provides spatial information of surface topography that is not included in amplitude parameters such as Root Mean Square roughness. This paper presents a statistical relation between ACL and the real area of contact, which is used to study the adhesive friction behavior of a rough surface. The influence of ACL on profile peak distribution is studied based on Whitehouse and Archard’s classical analysis, and their results are extended to compare profiles from different surfaces. With the knowledge of peak distribution, the real area of contact of a rough surface with a flat surface can be calculated using Hertzian contact mechanics. Numerical calculation shows that real area of contact increases with decreasing of ACL under the same normal load. Since adhesive friction force is proportional to real area of contact, this suggests that the adhesive friction behavior of a surface will be inversely proportional to its ACL. Results from microscale friction experiments on polished and etched silicon surfaces are presented to verify the analysis.

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