A method for evaluating friction using a backward extrusion-type forging

Shen, G.; Vedhanayagam, Arun; Kropp, E.; Altan, Taylan

doi:10.1016/0924-0136(92)90314-i

Cited by 54 publications

(20 citation statements)

References 3 publications

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“…In addition, it required a non-linear calibration curve to determine the shear friction factor. To overcome such a problem, several tests [1][2][3] based on backward extrusion or forward and backward extrusion, have been developed. These tests were better suited for predicting the friction levels in the cold forging process involved with the large surface expansion and higher pressure distribution along the punch compared to the interface between the billet and dies.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of miniaturized tip test

et al. 2008

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A tip test was developed and used successfully for friction measurement between the billet and dies or punches for the cold forging process. In the present investigation, the test was downsized and experimentally investigated to find the size effect on test results. For the test, aluminum alloys of 2024-O and 6061-O were used and the specimen was made into a cylinder of diameter and height of 10.0mm and 5.0mm, respectively. For lubrications, VG32, VG100, grease, and corn oil were used in experiments and tests were also carried out with two different humidity conditions. A micro-hardness test was made to compare the hardness distribution with the strain distribution obtained from the finite element simulation. The load levels and tip distances were measured for Al6061-O specimen with various lubrication conditions and compared to each other to find any correlation between the two. The shear friction factors were determined for various lubrications by using the finite element simulation under the present condition.

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Section: Introductionmentioning

confidence: 99%

Experimental study of miniaturized tip test

et al. 2008

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“…Bay [2] studied the application of the friction model for the analyses of the bulk metal forming process. On the basis of these and other results, [3][4][5][6][7] Ebrahimi and Najafizadeh developed an upper-bound theory to determine the average Tresca friction coefficient by conducting a barrel compression test. [8,9] According to this theory, the average Tresca friction coefficient m for a cylindrical sample can be determined by measuring the degree of barreling sample and using the following equation:…”

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confidence: 99%

Evaluation of Friction Coefficient by Simulation in Bulk Metal Forming Process

Onodera

Chiba

2009

Metall Mater Trans A

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With the objective of evaluating the accuracy of the upper-bound theory for calculating the average Tresca friction coefficient m in the hot forging process, we performed simulations using different values of m in each compression process to high strain levels. It was found that the upper-bound theory is not applicable at high strain levels, because the contact surface of the cylindrical sample is composed of an originally flat end surface and the annular portion formed by the contact of the lateral surface with the anvil surface. The relation among P ¼ R m H R t H 0 ; true strain, and m could be expressed by a 0 þ a 00 e þ a 000 e 2 À P À Á þ b 0 þ b 00 e þ b 000 e 2 À Á m þ c 00 e þ c 000 e 2 À Á m 2 ¼ 0: Here, the m values obtained were in good agreement with the actual ones used in the simulations. The value of m of the arbitrary geometry cylindrical sample could also be directly read from a contour map with a relationship among nominal strain, parameter B of the corresponding standard sample, and m.

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“…마찰조건을 정량적으로 예측하기 위한 시험법 으로는 링 압축 시험법 [2]을 비롯하여 스파이크 시험법 [3], 버켙 시험법 [4], 인젝션 업셋팅 시험법 [5], 전후방 압출 시험법 [6] 팁 시험법 [7,8] (1) 펀치의 형상은 마찰보정선도에 큰 영향을 미치지 않는다. …”

Section: 서 론unclassified

Effect of Punch Design and Flow Stress on Frictional Calibration Curve in Boss and Rib Test

2009

Transactions of Materials Processing

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Recently, boss and rib test based on backward extrusion process was proposed to quantitatively evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and flow stress on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the calibration curves showing the heights of the boss and rib. In addition, the effect of flow stress on the calibration curves was investigated through FE simulations. It was found that there is no effect of strength coefficient of the workpiece on the calibration curves for estimation of friction condition. On the other hand, the strainhardening exponent of the workpiece has a significant influence on the calibration curve.

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A method for evaluating friction using a backward extrusion-type forging

Cited by 54 publications

References 3 publications

Experimental study of miniaturized tip test

Experimental study of miniaturized tip test

Evaluation of Friction Coefficient by Simulation in Bulk Metal Forming Process

Effect of Punch Design and Flow Stress on Frictional Calibration Curve in Boss and Rib Test

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