Figure 38.

Chain Hoist After 5-Ton High-Explosive Test (200-psi Level)

Figure 39.

Vacuum Pump After 5-Ton High-Explosive Test (200-psi Level)

The final test conducted by Boeing was at the invitation of the Defense Nuclear Agency. They had scheduled a test equivalent to more than 500 tons of TNT for October 6, 1976. Because of their interest in, and potential importance of, industrial hardening measures, they asked Boeing to participate on a contract basis (Contract DNA-001-76-C-0350). Since no failures occurred to specimens during the 5-ton tests at Holloman at overpressures of up to 300 psi, the DNA requested that specimens be included in the large-scale test at the 600-psi level.

The first set of test specimens included four large machines-a drill grinder located at 200 psi (similar to the machine buried in the static test at Auburn, Washington); an electrolytic chip breaker grinder at 80 psi; a power supply device at 40 psi (the grinder and its power supply are shown in Figure 40); and a minibike at 600 psi. The bike, in addition to being a functional component, was available locally in time to meet the schedule and represented several different types of structure, including hollow tanks, tubular structure, and the relatively damage-resistant castings of the motor.

The second set of test specimens was comprised of aluminum pipes. These were tested at the 600-psi overpressure level to permit analytical correlation of observed damage with predicted failure mechanisms. The third set was made up of portable electric hoists. These were included to represent very rugged machinery. Small electric pumps and varidrive units were included in the fourth set of specimens to represent medium-hard machines. The fifth set was made up of the electromechanical calculators and adding machines. These represented soft, relatively fragile machinery. The sixth and last set of the test specimens included waterfilled electronic cabinet racks. These represented tanks such as those found in chemical processing lines.

The test specimens were placed on styrene blocks to permit protection against ground shock and then packed in chips and covered with soil. Most of the test specimens were placed so that the depth of soil above the protective chips would ensure reliable earth arching. The soil cover calculations were based on the assumption that the angle of failure of the soil under dynamic blast loading would be the same as the angle of failure previously demonstrated under static load conditions. To learn more about the minimum effective depth of cover for soil arching, several of the mechanical calculators buried at the 200-psi location were placed in 1-foot increments of depth from 5 feet to only 1 foot to ensure that some specimens would be damaged because of insufficient soil cover.