scholarly journals A New Compression-Torsion-Tribometer with Scalable Contact Pressure for Characterization of Tool Wear during Plastic Deformation

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Marco Teller ◽  
Simon Seuren ◽  
Markus Bambach ◽  
Gerhard Hirt
Keyword(s):  
Yield Stress ◽  
Contact Pressure ◽  
Friction And Wear ◽  
Wear Behaviour ◽  
Cold Extrusion ◽  
Workpiece Material ◽  
Contact Pressures ◽  
High Contact Pressure ◽  
Multiple Load

A contact pressure which reaches up to ten times the yield stress of the workpiece material is characteristic for cold extrusion processes. Common tests for friction and wear are limited to rather low contact pressures. Thus, the aim of this paper is to present a new compression-torsion-tribometer which is able to scale the contact pressure to a multiple of the yield stress of the workpiece. In order to enable a contact pressure that greatly exceeds the yield stress of the workpiece material, the workpiece specimen is encapsulated laterally. As main parameters, contact pressure, glide length, and relative velocity can be adjusted independently, thus allowing for multiple load cycles. The resulting torque is measured continuously as an indicator for wear. Afterwards wear can be also quantified by examination of surfaces. Hence, the developed setup enables a comparison of tool surfaces and coatings and a characterization of wear behaviour under high contact pressure.

scholarly journals A Novel Reciprocating Tribometer for Friction and Wear Measurements with High Contact Pressure and Large Area Contact Configurations

Lubricants ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 123
Author(s):  
Kim Berglund ◽  
Maria Rodiouchkina ◽  
Jens Hardell ◽  
Kalle Kalliorinne ◽  
Jens Johansson
Keyword(s):  
Contact Pressure ◽  
Friction And Wear ◽  
Guide Vane ◽  
Operating Conditions ◽  
Test Method ◽  
Large Area ◽  
Contact Pressures ◽  
High Contact Pressure ◽  
Wear Tests ◽  
Friction And Wear Tests

There are many moving machine assemblies with conformal tribological contacts at very high contact pressures, e.g., sliding bearings, propeller shaft bearings and machine guideways. Furthermore, applications such as trunnion and guide vane bearing in Kaplan turbines have very low sliding speeds and oscillatory types of motion. Although there is a vast selection of tribology test rigs available, there is still a lack of test equipment to perform friction and wear tests under high contact pressure, reciprocatory sliding and large area contact. The aim of this work is thus to develop a novel reciprocating tribometer and test method that enables friction and wear tests under low-speed reciprocatory sliding with contact pressures up to 90 MPa in a flat-on-flat contact configuration. First, a thorough description of the test rig design is given. Secondly, the influence of contact pressure and stroke length on the tribological properties of a stainless steel and polymer composite material combination is studied. The significance of considering creep, friction during the stroke and contact temperature is specifically highlighted. The novel tribometer can be used to screen different bearing and shaft material combinations and to evaluate the friction and wear performance of self-lubricating bearings for the specific operating conditions found in Kaplan turbines.

Central and Minimum Elastohydrodynamic Film Thickness at High Contact Pressure

1997 ◽  
Vol 119 (2) ◽  
pp. 291-296 ◽  
Author(s):  
M. Smeeth ◽  
H. A. Spikes
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Contact Pressure ◽  
Applied Load ◽  
Optical Technique ◽  
Test Rig ◽  
Minimum Film Thickness ◽  
Elastohydrodynamic Film Thickness ◽  
Contact Pressures ◽  
High Contact Pressure

A new optical technique has been developed which is able to obtain accurate film thickness profiles across elastohydrodynamic (EHD) contacts. This has been used in conjunction with a high pressure EHD test rig to obtain both central and minimum EHD film thicknesses at high contact pressures up to 3.5 GPa. The results have been compared with the classical film thickness equations of Hamrock and Dowson and also with recent high pressure computations due to Venner. It is found that minimum film thickness falls more rapidly with applied load at high than at low contact pressures, with a film thickness/load exponent of −0.3. This confirms the findings of recent high pressure computational EHD modeling.

scholarly journals Comparison of Frictional Properties of CVD-Grown MoS2 and Graphene Films under Dry Sliding Conditions

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 293 ◽  
Author(s):  
Dae-Hyun Cho ◽  
Jaehyuck Jung ◽  
Chan Kim ◽  
Jinhwan Lee ◽  
Se-Doo Oh ◽  
...  
Keyword(s):  
Contact Pressure ◽  
Friction And Wear ◽  
Graphene Film ◽  
Sliding Surface ◽  
Si Substrate ◽  
Wear Properties ◽  
Si Substrates ◽  
Mos2 Film ◽  
Friction And Wear Properties ◽  
Contact Pressures

In the present study, dry friction and wear properties of atomically thin CVD-grown graphene and MoS2 films on SiO2/Si substrates were compared at low (72 MPa) and high (378 MPa) contact pressures. Analysis of atomic force microscopy images of these films verified that the MoS2 films, which were directly grown on the SiO2/Si substrates, had clean surfaces and made conformal contacts with the substrates. In contrast, the graphene film showed many contaminants on its surface and was loosely bonded with its SiO2/Si substrate due to its wet transfer from a Cu foil to the substrate. The MoS2 film exhibited friction and wear properties superior to those of the graphene film both at low and high contact pressures. We found that the clean sliding surface and strong bonding with SiO2/Si were the main causes of the superiority of the MoS2 film compared to the graphene film. Mild wear occurred in a layer-by-layer fashion at low contact pressure for the MoS2 film. At high contact pressure, severe wear occurred due to failure at the boundary between the MoS2 films and the underlying substrates. At both contact pressures, friction did not increase immediately after the removal of the MoS2 film from the SiO2/Si substrate because the film transferred onto the counter sliding surface and served as a lubricant.

Wear behaviour of α-alumina in hot steam at high contact pressure

Wear ◽  
2018 ◽  
Vol 404-405 ◽  
pp. 22-30 ◽  
Author(s):  
Rolf Wäsche ◽  
Guido Brandt ◽  
Roman Ehrke ◽  
Gert Nolze ◽  
Thomas Schmid ◽  
...  
Keyword(s):  
Contact Pressure ◽  
Wear Behaviour ◽  
High Contact Pressure
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