On the Use of a Torsional Split Hopkinson Bar to Study Rate Effects in 1100-0 Aluminum

Abstract

The difficulties involved in the accurate measurement of the flow stress of materials at high rates of deformation are reviewed, and methods of overcoming these difficulties are discussed. It is concluded that the best experimental method is that in which a split Hopkinson bar is adapted for torsion testing, and the loading pulse is approximately square in shape and has a relatively short duration. A description is given of apparatus which was developed to achieve this type of loading, the input wave being generated explosively. This wave was found to contain large amplitude fluctuations, and to eliminate these a mechanical “pulse smoother” was used. The operation of this device is described, and the test procedure, method of calibration, and possible sources of inaccuracy are discussed. Results are presented for 1100-0 aluminum alloy deformed at strain rates of the order of 800 sec−1 and are compared with those obtained at a nominal strain rate of 10−4 sec−1; the results are also compared with those obtained in compressive tests by other workers.

Effects on Texture and Microstructure of Aluminium Alloy 7075-T651 during High Strain Rate Torsion

“…This results in the storage of torque between loading end of the bar and clamp. Subsequently, the sudden release of clamp results in propagation of shear stress pulse along the bar, thereby loading the sample in shear at high strain rate [6]. The different angles of twist used in the present investigation are 4, 10 and 16 degrees.…”

“…1. The split Hopkinson torsional bar consists of two elastic bars, a clamp with a sudden releasing mechanism, and a loading arrangement to twist one of the bars [6]. The hollow cylindrical sample is placed between the bars and twist is applied at one end of the bar via a loading mechanism [6].…”

A comparative study on the restrictions of dynamic test methods

“…Hopkinson bar consists mainly of three bars, striker, incident and transmission bars [5][6][7]. The general view of a Hopkinson bar is shown in Fig.…”

“…Another testing machine which is capable of producing a uniform strain rate is the cam plastometer [4]. In Much of the experimental work on the high strain rate response of materials involves the use of the most universally accepted high rate testing apparatus, the split Hopkinson bar (SHB), also known as the Kolsky bar, with different loading modes, including tension [5], compression [6], and shear [7]. Strain rates up to 10 4 s −1 can be attained by the SHB.…”

In situ damage assessment using synchrotron X-rays in materials loaded by a Hopkinson bar

“…Lindholm incorporated most of the previous improvements and presented an updated version of the Kolsky bar for dynamic characterization, which became the most widely used version for decades [6][7][8][9]. This technique was also expanded to tension [10][11][12], torsion [13,14], tri-axial compression [15][16][17] and tension/compression-shear [18][19][20] versions. To subject a specimen to desired testing conditions and to recover the specimen after a well-defined loading history, pulse-shaping and momentum-trapping techniques were introduced [21][22][23].…”