Demonstration of tailored impact to achieve blast-like loading

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Highlights

  • The Blast Simulator at UCSD uses high velocity impact to achieve blast-like loads on structures.

  • Data collection from the impact is explained with an emphasis on a method for obtaining impulse demand.

  • To demonstrate the hydraulic punch, a Blast Simulator test is compared to a high fidelity computer model.

  • The Blast Simulator test is also compared to a field test using live explosives.

  • Good agreement with the field test demonstrates that heavy tailored impact is a viable alternative to field testing.

Abstract

Investigation of blast loading using mechanical devices is a viable alternative to field testing with live explosives. Using impact to simulate blast-like loads has been shown to generate repeatable loading similar to field testing with live explosives, and impact loading has the advantage of high speed camera data that is not obscured by a fireball. It is demonstrated that the UCSD Blast Simulator has the capability of generating blast-like loading on civil structures by using hydraulic rams, in which the loading is tailored in two ways. First, the careful regulation of the hydraulic pressures and valve opening/closing allows the impact to be adjusted so that the peak loads and duration of the load can be controlled. Secondly, the presence of a polyurethane material at the front of hydraulic rams determines the shape of the loading that is applied to the test specimens. These two key characteristics of the Blast Simulator, which govern the pulse duration, shape, and impulse associated with impact, are referred to as the punch and the programmer. The experimental data processing methodology relating to the punch of the hydraulic rams is described, along with a brief description of the rubber programmer material. The results of a major Blast Simulator test are shown, as well as the description of a method for incorporating all relevant aspects of the punch and the programmer into a corresponding high fidelity computer simulation. Finally, the results of this Blast Simulator test are compared to a corresponding field test using live explosives in order to demonstrate the capability of the Blast Simulator to generate blast-like loading.

Section snippets

Introduction and alternative testing methods

The UCSD Blast Simulator [1] is a US Federal Government-sponsored apparatus that utilizes hydraulic actuators in order to simulate blast-like events (Fig. 1a and b). The objective of this paper is to demonstrate the ability of the Blast Simulator to generate impulsive loading on structures that is similar to blast loading. This is demonstrated through a comparison of a Blast Simulator test, a high fidelity computer simulation, and a field test. This paper describes the two characteristics of

Net hydraulic force

The technology used in the Blast Simulator was developed by MTS Corporation and UCSD. Each impact mass in the Blast Simulator is driven independently based on inputs supplied prior to a test. These inputs control the hydraulic pressures and valve opening times, which ultimately determine the peak forces and load durations applied to the test specimen, from the hydraulic punch. More detailed information about this process, as well as general information about the Blast Simulator, can be found in

Blast Simulator test and finite element simulation

The procedure previously outlined, which calculates impulse demand, is validated through a test that was conducted at the UCSD Blast Simulator in collaboration with Simpson Gumpertz & Heger, Inc. This test investigated the response of a prototype stud wall system used as a retrofitting strategy for structures that are vulnerable to blast. Thus, this test includes both the prototype wall as well as an un-grouted masonry wall, which represents an existing, vulnerable, structure (Fig. 4a).

The

Direct comparison to field test

The final validation program at Tyndall Air Force Base consisted of full-scale tests under live explosives representing actual blast pressure-pulses and fireball conditions. Fig. 10a shows the fireball generated from the live explosive test. Fig. 10b shows a suite of different prototype walls just prior to the pressure pulse, and Fig. 10c shows the response of the walls from the impulsive loading.

The loading is shown in Fig. 11, where the field test data have been compared to Blast Simulator

Summary and conclusions

The UCSD Blast Simulator uses high velocity impact to simulate blast-like loading on structures. The presence of a particular elastomer at the front of the impact rams and the tailoring of the hydraulic punch of the pistons are characteristics that are unique to the Blast Simulator. Since the hydraulic punch is not incorporated into other large scale test devices that utilize impact for heavy dynamic loading such as crash sleds, a method for obtaining the impulse delivered from the hydraulic

Acknowledgments

The prototype steel stud wall research was sponsored by the Army Research Laboratory (ARL) under Cooperative Agreement Number DAAD 19-03-2-0036 and the U.S. Air Force Research Laboratory at Tyndall Air Force Base, managed by SCRA Applied R&D, and executed by Simpson Gumpertz & Heger, Inc. This prototype wall study was performed under the direction of Ronald O. Hamburger, Principal Investigator, Dr. Ronald L. Mayes, Project Manager, and Dr. Ady Aviram, Project Engineer.

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