On the Detonation Pressure Produced at the Inner Surface of the Charge Hole

Abstract

In these experimental studies, the magnitude of the detonation pressure produced at the inner surface of the charge hole by the detonation, of a confined explosive and the change in that pressure with time were chiefly investigated by means of measuring the stress wave produced within a steel rod by this explosion, utilizing a specially designed piezo-electric pressure gauge. The main element of the above pressure gauge was a transducing unit which contains a barium titanate ceramic transducer enclosed tightly in the gauge body. The strong stress caused by the explosion must be properly reduced before being imposed upon the transducing unit. In this gauge such reduction of stress was accomplished by placing an ebonite directly on top of the upper surface of the ceramic transducer. The results obtained are briefly shown below. In the case of the detonation of a confined 45g- or 90g-cartridge charged in a bore hole with a charging density of 0.7g/cm³, the rise time to the peak pressure was less than about 2μs, and this peak pressure decreased rapidly to the state of so-called static pressure about 15μs later, decreasing very slowly thereafter. The duration time of such detonation pressure in the charge hole was about half a millisecond in these experiments. The value of about 3×10⁴kg/cm² was obtained as the steady detonation pressure (generally known as Pᴄ₋ᴊ) of a 45g-cartridge of No. 3 Take dynamite under our experimental conditions, corresponding to a velocity of detonation of 3, 3000 m/s.