日本金属学会誌

J. Japan Inst. Metals, Vol. 29, No. 8 (1965),
pp. 811-817

Deformation of Polycrystalline Aluminium at High Strain Rates (Studies of High Velocity Deformation of Metallic Materials II)

Susumu Yoshida1 and Norio Nagata1

1National Research Institute for Metals, Tokyo

Abstract:

The dynamic deformation behaviour of annealed polycrystalline aluminium (99.99% purity) has been investigated by a compression test at room temperature using a bar-bar type impulsive loading apparatus. The dynamic stress-strain relation is derived from an analysis of stress-time records at both ends of a cylindrical specimen. The range of strain rates studied is from 1 × 102 sec-1 to 8 × 103 sec-1. The results obtained are as follows:
(1) The dynamic stress-strain curve for aluminium is parabolic similarly to the static curve. The dynamic flow stress is always higher than the static one, and the difference between them for the same strain becomes greater with increase of the strain and the strain rate. This shows that the plastic deformation behaviour of annealed aluminium is dependent on the strain rate.
(2) The experimental stress-strain-strain rate relations for annealed polycrystalline aluminium for strain rates ranging from 1 × 102 sec-1 to 2 × 103 sec-1 and for strains ranging from 1% to 16% are summarized by a relation,

σ (kg/mm2)=12.8 ε·0.38ε·1/16 (sec-1).

(3) When a specimen is dynamically deformed repeatedly at a constant high strain rate, each deformation can be superposed in a similar fashion to the case of static deformation.
(4) The flow stress of a specimen which has been given a certain amount of deformation is different depending on the strain rate history during the deformation. It is higher for a dynamic deformation than for a static deformation. Namely, the flow stress depends not only on the instantaneous strain and strain rate but also on the strain rate history of the specimen.


(Received 1965/4/19)

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