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Research Papers: Other (Seals, Manufacturing)

Modeling of the Friction Behavior in Metal Forming Process Considering Material Hardening and Junction Growth

[+] Author and Article Information
Mengyun Mao

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: maomengyun@sjtu.edu.cn

Linfa Peng

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: penglinfa@sjtu.edu.cn

Peiyun Yi

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: yipeiyun@sjtu.edu.cn

Xinmin Lai

Shanghai Key Laboratory of Digital
Manufacture for Thin-Walled Structures;
State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: xmlai@sjtu.edu.cn

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received December 2, 2014; final manuscript received July 4, 2015; published online October 1, 2015. Assoc. Editor: Mircea Teodorescu.

J. Tribol 138(1), 012202 (Oct 01, 2015) (18 pages) Paper No: TRIB-14-1294; doi: 10.1115/1.4031395 History: Received December 02, 2014; Revised July 04, 2015

In various plastic forming processes of metals, friction has been revealed to play an important role in the determination of the material flow, fracture, and surface quality. The precise description of friction behavior is thus a critical issue for the accurate prediction and analysis of these formability indicators. Generally, the friction behavior is inevitably affected by material hardening and junction growth. However, few of the previous models have taken both of them into consideration, especially for the nonlinear hardening materials. In this study, the classical contact model was modified to include the power-law hardening material, and the general friction law combined with Tabor's equation was employed to estimate the friction stress with the junction growth of asperities. An asperity-based friction model for rough surfaces in metal forming process was then obtained by summarizing the normal and tangential stresses of all the asperities on the surface using Greenwood and Williamson (GW) method. The model was validated by comparing to the finite element (FE) results and the experimental results. And its comparison with Kogut and Etsion (KE) model and Cohen's model revealed a wider range of application for the present model. It was also found to be able to predict the friction coefficient and the real contact area of nonlinear hardening materials under various contact conditions. This work is helpful to understand the friction behavior and further guide the simulation and optimization of forming processes.

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References

Figures

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Fig. 1

Contact model of nominally flat rough surface

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Fig. 2

Brief diagram of modeling procedure

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Fig. 3

A deformable hemisphere pressed by a rigid flat plane

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Fig. 4

Schematic diagram of distribution of effective strain in sphere

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Fig. 5

Asperity contact area as a function of load and strain hardening

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Fig. 6

Sphere–flat friction coefficient as a function of normal load: (a) comparison with Ovcharenko's experiment and (b) comparison with Etsion's experiment

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Fig. 7

Sphere–flat contact area in the inception of sliding as a function of normal load

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Fiig. 9 Contact area of rough surface at the inception of sliding as a function of normal load

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Fig. 8

Friction coefficient of rough surface as a function of normal load

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Fig. 15

Friction coefficient of RS with friction factors (a) f=0.7, (b) f=0.5, and (c) f=0.3

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Fig. 14

Affecting ranges of strain-hardening and junction growth under the dimensionless normal load of (a) Fn/σ0Sn=0.01 and (b) Fn/σ0Sn=0.1

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Fig. 13

The ratio of junction growth on the map of initial plasticity index and friction factor under the dimensionless normal load of (a) Fn/σ0Sn=0.01 and (b) Fn/σ0Sn=0.1

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Fig. 12

The RH effect on the map of initial plasticity index and friction factor under the dimensionless normal load of (a) Fn/σ0Sn=0.01 and (b) Fn/σ0Sn=0.1

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Fig. 16

Friction coefficient as a function of normal load and yielding strain with friction factors (a) f=0.7, (b) f=0.5, and (c) f=0.3

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Fig. 17

Contact area as a function of normal load and hardening exponential with friction factors (a) f=0.7, (b) f=0.5, and (c) f=0.3

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Fig. 11

The friction coefficient and dimensionless normal load as a function of plasticity index under a given exterior condition

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Fig. 10

Comparison of contact areas at the inception of sliding and those under normal load alone

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