Friction coefficients in cold forging: A global perspective

Groche, Peter; Krämer, Philipp; Bay, Niels; Christiansen, Peter Leth; Dubar, Laurent; Hayakawa, Kunio; Hu, Chen; Kitamura, Kazuhiro; Moreau, Philippe

doi:10.1016/j.cirp.2018.04.106

Cited by 35 publications

(13 citation statements)

References 11 publications

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“…This differentiates the SCT from other tribometers such as the Double Cup Extrusion Test [18], the Ring Compression Test [19] or the Spike Test [20]. Results derived from the SCT are in good quantitative agreement with results gained with other tribometers [21].…”

Section: Test Setupsupporting

confidence: 57%

Wear Prediction in Oscillating Cold Forging Processes

Groche

Schmidt

2020

Tribol Lett

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Oscillating forming processes allow forming with reduced process forces when liquid lubricants are used. They are industrially applied as oscillating cold forging processes for the production of splines. Previous investigations revealed that the force reduction is provoked by relubrication of the workpiece—tool contact zone. So far, the effect of the oscillation on tool wear remains unknown. The results presented in this paper show that the wear critical region of the tool is the calibration zone. Tool wear is emulated on a test bench under loads of representative cold forging processes. The results disclose several relevant phenomena. Friction conditions can vary considerably in the course of the oscillations. Wear protection layers are effective measures to prolong tool life also under these conditions. Prediction of wear development based on established models fails due to neglecting the local state of lubrication. Graphical Abstract

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Section: Test Setupsupporting

confidence: 57%

Wear Prediction in Oscillating Cold Forging Processes

Groche

Schmidt

2020

Tribol Lett

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“…The frictional force is reduced in order to smoothly maintain the surface properties of the tool and the workpiece, and to allow for constant maintenance of the lubricating film during metal forming. In forming, as a result of plastic deformation, sliding of a newly born surface occurs, so the description scheme of the transition state is a major task of friction modeling [72]. As shown in Fig.…”

Section: Friction Models and Gallingmentioning

confidence: 99%

Galling phenomena in metal forming

Dohda

Yamamoto

et al. 2020

Friction

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Galling phenomena in metal forming not only affect the quality of the engineered surfaces but also the success or failure of the manufacturing operation itself. This paper reviews the different galling conditions in sheet and bulk metal forming processes along with their evolution and the effects of temperature on galling. A group of anti-galling methods employed to prevent galling defects are also presented in detail. The techniques for quantitatively measuring galling are introduced, and the related prediction models, including friction, wear, and galling growth models, are presented to better understand the underlying phenomena. Galling phenomena in other processes similar to those occurring in metal forming are also examined to suggest different ways of further studying galling in metal forming. Finally, future research directions for the study of galling in metal forming are suggested.

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“…Groche et al have recently presented a systematic evaluation of six established tribometers: the ring compression test with boss (RCT-B), the combined forward rod backward can extrusion test (CFRBCET), the backwards cup extrusion test (BCET), the backward can extrusion with simultaneous rotation test (BCERT), the upsetting sliding test (UST), and the sliding compression test (SCT). A typical tribological system for cold forging operations, consisting of a zinc-phosphate conversion layer and polymer on blasted specimens (SAE 5115) with a combined lubricant layer weight of w = 22 g/m 2 , was chosen [7]. Four tribological loads were chosen according to Bay et al [8]: the contact normal stress σ n , the relative sliding velocity v rel , the surface enlargement ψ and the temperature T.…”

Section: State Of the Art Of Friction Measurement In Cold Bulk Metal mentioning

confidence: 99%

“…The adjustment of the tribological loads of different tribometers with the sliding compression test leads to a high accordance regarding the resulting friction coefficients, showing that for the given tribological system, the reproduction of tribological loads within different tribometers yields the same friction coefficients. Using the attained medium friction coefficient within the numerical simulation of the reference extrusion process (for a more in-detail description of the extrusion operation, see [9]) with the same tribological system, allows to reproduce the force-displacement-trend very well [7]. The adjustment of the tribological loads of different tribometers with the sliding compression test leads to a high accordance regarding the resulting friction coefficients, showing that for the given tribological system, the reproduction of tribological loads within different tribometers yields the same friction coefficients.…”

Section: State Of the Art Of Friction Measurement In Cold Bulk Metal mentioning

confidence: 99%

Friction Measurement under Consideration of Contact Conditions and Type of Lubricant in Bulk Metal Forming

Krämer¹,

Groche²

2019

Lubricants

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The tribological system plays a critical part in designing robust and efficient cold forging operations. The appropriate selection of lubrication allows to forge defect-free workpieces with high dimensional precision and desired surface finish while ensuring that no defects, such as cracks or seams, occur. Additionally, friction and wear are highly affected by the choice of tribological system, which in turn influence the cost-effectiveness of the forging operation by preventing premature tool failure. Next to the employed tool coating and work piece material, the lubrication system and work piece surface topography are the main factors influencing the aforementioned constraints when designing efficient forging operations. In order to choose the appropriate tribological system before implementing it within an industrial forging operation, tribometers are used to characterize the performance of the tribological system. In this paper, the necessity to account for not only the tribological loads when designing these tribometer tests as is typical for existing methodologies, but also for process and lubricant specific properties will be highlighted. With the help of the tribometer sliding compression test, it will be shown that using liquid lubricants necessitates the need to account for the escape of lubricant, while this is not true for solid lubricants. The escape of lubricant from the contact zone is governed by lubricant properties as well as the contact kinematics and may lead to significantly different results regarding friction and wear. In order to account for this escape, the tribometer test must be specifically designed to reproduce the contact kinematics of the investigated industrial forging operation.

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Friction coefficients in cold forging: A global perspective

Cited by 35 publications

References 11 publications

Wear Prediction in Oscillating Cold Forging Processes

Wear Prediction in Oscillating Cold Forging Processes

Galling phenomena in metal forming

Friction Measurement under Consideration of Contact Conditions and Type of Lubricant in Bulk Metal Forming

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