Identification of Friction Coefficient in Forging Processes by Means T-Shape Tests in High Temperature

In hot metal bulk forming and forging, the interface heat transfer and the friction between the tooling and the billet are of particular importance since they have a significant effect on material flow, deformation, forming forces, component surface finish and die wear. Several authors have used different characterization methods to measure the friction coefficient using cylindrical upsetting tests, ring compression tests, Spike tests and T-Shape tests among others.In the present paper, The T-Shape test has been used in order to measure the friction between aluminium billets and tool steel. In order to obtain the sensitivity of the test, a Finite Element (FE) parametric study has been performed which indicates that shape of specimen could be chosen to measure the friction. For this, compression tests for three specimens in dry conditions have been carried out and shape of specimen has been measured. These measurements and the use of adequate inverse modelling techniques enabled a precise characterization of the forging friction coefficient. Heat transfer coefficient (HTC) has been precisely characterised from the columnar upsetting thermal tests and later used in simulating the T-Shape tests to estimate the friction factor (m). Friction factor has been determined by comparing the experimental results with the numerical simulation results of T-Shape compression test. An encouragingly good agreement has been found between the experimental and numerical results.

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Characteristics of Fluoride Based Conversion Coating Film on Al-Alloy for Metal Forming Applications

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.622-623.37 ◽

2014 ◽

Vol 622-623 ◽

pp. 37-44

Author(s):

Varunee Premanond ◽

Pongpan Niyomrit

Keyword(s):

Friction Coefficient ◽

Soap Film ◽

Conversion Coating ◽

Cold Forging ◽

Al Alloy ◽

Coating Film ◽

Compression Tests ◽

Metal Soap ◽

Cold Forming ◽

Ring Compression

During the process of cold forming of aluminum, the high pressure which is introduced on the die can result in high adhesion between the aluminum and the die surface. Therefore, it is necessary for the aluminum billet to be coated with a lubricant prior to forming, to reduce adhesion and to ease the flow of material in the die. There are several popular types of lubricant systems used in cold forging of aluminum. For severe deformation, conversion coating in conjunction with soap lubricant are commonly used. The conversion coatings include soap phosphates (PO4-soap), as well as soap aluminum fluoride (AlF-soap). Therefore, this work studied the performance of the AlF-soap system and compared it to the conventional PO4-soap system as tested on AA6063 aluminum. Ring compression tests and ball on disc tests were conducted to explore friction conditions and the thinning of the lubricant under several forming conditions. It was found that the quantity of metal soap layer of AlF-soap used affected the friction coefficient and the lubricant thinning under forming operation. The suitable coating weight of metal soap layer of AlF-soap for this experiment was found to be 2 g/m2. The friction coefficient of the PO4-soap system was 16.26% lower than the AlF-soap system. However, the amount of thinning of the AlF-soap film after ring compression tests was lower than that of PO4-soap film.

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Effect of the heat-transfer coefficient in ring-compression tests

Journal of Materials Processing Technology ◽

10.1016/0924-0136(95)02141-8 ◽

1996 ◽

Vol 62 (1-3) ◽

pp. 10-13 ◽

Cited By ~ 7

Author(s):

K. Andersson ◽

S. Kivivuori ◽

A.S. Korhonen

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Compression Tests ◽

Ring Compression ◽

The Heat Transfer Coefficient

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An Experimental Study on Lubrication Behavior of Glass Lubricants during Hot Plastic Deformation of Ni-Based Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.591-593.960 ◽

2012 ◽

Vol 591-593 ◽

pp. 960-964

Author(s):

Rui Li ◽

Chao Yang Sun ◽

Qing Dong Zhang

Keyword(s):

Plastic Deformation ◽

Strain Rate ◽

Friction Factor ◽

Flow Behavior ◽

Compression Tests ◽

Hot Plastic Deformation ◽

Ring Compression ◽

Specimen Material ◽

Inconel 690 ◽

Lubrication Performance

Friction factor and flow behavior of melt glass lubricants A5 and up68/2886 during hot plastic deformation of Ni-based alloys Incoloy800H and Inconel 690 were studied by using ring compression tests. The results indicated that glass up68/2886 had higher mobility than glass A5. Friction factor between interfaces went up with temperature in sufficient lubrication, but the opposite in inadequate lubrication, and the friction factor went down with strain rate under both conditions. Besides, yield strength of specimen material also slightly influenced lubrication performance of glass lubricants in inadequate lubrication. Low friction factor about 0.1 was still obtained in inadequate lubrication by using glass up68/2866, therefore excellent performance could be expected when glass up68/2886 was used properly such as at higher strain rate.

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Interfacial Friction of Ceramics at High Temperature Ring-Compression Test

Materials Science Forum ◽

10.4028/www.scientific.net/msf.704-705.967 ◽

2011 ◽

Vol 704-705 ◽

pp. 967-972

Author(s):

Hui Gai Wang ◽

Yan Pei Song ◽

Fei Wang ◽

Kai Feng Zhang

Keyword(s):

High Temperature ◽

Boron Nitride ◽

Friction Factor ◽

Compression Test ◽

Elevated Temperatures ◽

Interfacial Friction ◽

Average Pressure ◽

Compression Tests ◽

Ring Compression Test ◽

Ring Compression

Using ring compression tests, the interfacial friction and flow stress of 3Y-TZP/Al2O3 composite at elevated temperatures were investigated. Theoretical calibration curves of the friction factor and the relative average pressure curves for the ring compression tests of 6:3:2 standard rings were drawn based on a velocity field capable of describing the bulge phenomena. The lubricant was the boron nitride (hexagonal). The tests were adopted at temperature range of 1400°C-1600°C. Results indicate that the interfacial friction factor has the value in the range of 0.34-0.49, so that boron nitride lubricant can be used effectively in present temperatures. As two extremely important parameters, the temperature and strain rate have no significant effect on the fraction factor. It is proved reliable that the ring-compression test at 1400°C and even higher is used to evaluate the performance of boron nitride lubricant.

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Determination of Friction Coefficient by Employing the Ring Compression Test

Journal of Engineering Materials and Technology ◽

10.1115/1.1369601 ◽

2000 ◽

Vol 123 (3) ◽

pp. 338-348 ◽

Cited By ~ 36

Author(s):

Hasan Sofuoglu ◽

Hasan Gedikli ◽

Jahan Rasty

Keyword(s):

Finite Element ◽

Friction Coefficient ◽

Material Properties ◽

Rate Sensitivity ◽

Compression Tests ◽

Element Analysis ◽

Test Conditions ◽

Calibration Curves ◽

Ring Compression ◽

Friction Calibration

The main objective of this research was to investigate the effect of material properties, strain-rate sensitivity, and barreling on the behavior of friction calibration curves. The compression tests were conducted to obtain the necessary material properties for the finite element analysis. A series of ring compression tests were then conducted in order to determine the magnitude of the friction coefficient, μ. The experiments were first conducted for the modeling materials, namely, white and black plasticine and later on, for aluminum, copper, bronze, and brass. The experiments were then simulated via an elastic-plastic finite element code (ABAQUS). Contrary to the results available in the literature, where the same friction calibration curves are recommended for all types of materials and test conditions, the results of this investigation showed that friction calibration curves are indeed affected by the material properties and test conditions.

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A Finite Element Study of Thermo-Mechanical Fields and Their Relation to Friction Conditions in Al1050 Ring Compression Tests

Journal of Manufacturing and Materials Processing ◽

10.3390/jmmp2040083 ◽

2018 ◽

Vol 2 (4) ◽

pp. 83 ◽

Cited By ~ 1

Author(s):

Brigit Mittelman ◽

Elad Priel ◽

Nissim Navi

Keyword(s):

Finite Element ◽

Flow Stress ◽

Friction Coefficient ◽

Computational Models ◽

Experimental System ◽

Pure Aluminium ◽

Compression Tests ◽

Element Analysis ◽

Ring Compression ◽

Flow Stress Data

The most accepted method for determining friction conditions in metal forming is the ring compression test (RCT). At high temperatures, extraction of the friction coefficient, μ, commonly requires numerical analysis due to the coupling between the mechanical and thermal fields. In the current study, compression tests of cylindrical specimens and RCT experiments were conducted on commercially pure aluminium (Al1050) at several temperatures, loading rates, and lubrication conditions. The experiments were used in conjunction with a coupled thermo-mechanical finite element analysis to study the dependence of the friction coefficient on those parameters. It is demonstrated that due to the coupling between friction conditions and material flow stress, both μ and flow stress data should be determined from the cylinder and ring specimens simultaneously and not subsequently. The computed friction conditions are validated using a novel method based on identification of the plastic flow neutral radius. It is shown that, due to heat loss mechanisms, the experimental system preparation stage must be incorporated in the computational analysis. The study also addresses the limitation of the RCT in the presence of high friction conditions. The computational models are finally used to examine the thermo-mechanical fields, which develop during the different processes, with an emphasis on the effect of friction conditions, which were then correlated to the resulting microstructure in the RCTs.

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