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This report documents the results of two of tests that were performed on an explosive containment vessel at Sandia National Laboratories in Albuquerque, New Mexico in July 2013 to provide some deeper understanding of the effects of charge geometry on the vessel response [1]. The vessel was fabricated under Code Case 2564 of the ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels [2]. The explosive rating for the vessel, based on the Code Case, is nine (9) pounds TNT-equivalent. One explosive test consisted of a single, centrally located, 7.2 pound bare charge of Composition C-4 (equivalent to 9 pounds TNT). The other test used six each 1.2 pound charges of Composition C-4 (7.2 pounds total) distributed in two bays of three.

Code Case 2564 for the design of impulsively loaded vessels was approved in January 2008. In 2010 the US Army Non-Stockpile Chemical Materiel Program, with support from Sandia National Laboratories, procured a vessel per this Code Case for use on the Explosive Destruction System (EDS). The vessel was delivered to the Army in August of 2010 and approved for use by the DoD Explosives Safety Board in 2012. Although others have used the methodology and design limits of the Code Case to analyze vessels, to our knowledge, this was the first vessel to receive an ASME explosive rating with a U3 stamp. This paper discusses lessons learned in the process. Of particular interest were issues related to defining the design basis in the User Design Specification and explosive qualification testing required for regulatory approval. Specifying and testing an impulsively loaded vessel is more complicated than a static pressure vessel because the loads depend on the size, shape, and location of the explosive charges in the vessel and on the kind of explosives used and the point of detonation. Historically the US Department of Defense and Department of Energy have required an explosive test. Currently the Code Case does not address testing requirements, but it would be beneficial if it did since having vetted, third party standards for explosive qualification testing would simplify the process for regulatory approval. Copyright © 2013 by ASME.

For an impulsively loaded containment vessel, such as the Sandia Explosive Destruction System (EDS), the traditional notion of a single-value explosive rating may not be sufficient to qualify the vessel for many real-life loading situations, such as those involving multiple munitions placed in various geometric configurations. Other significant factors, including detonation timing, geometry of explosive(s), and standoff distances, need to be considered for a more accurate assessment of the vessel integrity. It is obvious that the vessel structural response from an explosive charge detonated at the geometric center of the vessel will be very different from the structural response from the same explosive charge detonated next to the vessel wall. It is, however, less obvious that the same explosive can produce vastly different vessel response if it is detonated at one end versus at the middle versus from both ends. The goal of this paper is to identify some of the effects that non-trivial loading situations have on the vessel structural integrity. The metric for determining vessel integrity is based on Code Case 2564 of the ASME Boiler and Pressure Vessel Code. Based on the findings of this work, it may be necessary to qualify impulsively loaded containment vessels for specific explosive configurations, which should include the quantity, geometry and location of the explosives, as well as the detonation points. Copyright © 2013 by ASME.

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Establishing design and inspection criteria for impulsively loaded vessels requires a precise understanding of the damage mechanisms and failure modes experienced by the vessels. To that end, Stress Engineering Services, Inc. performed a metallurgical examination of three impulsively loaded vessels that Sandia National Laboratories had intentionally tested to failure, two by impulsive loading and one by hydrotest after impulsive load testing. The vessels were scale models of Type 316 stainless steel vessels use for disposal of chemical ordnance. The examination identified microstructural effects, mechanical damage, and fractographic features associated with exposure to impulsive loads. In particular, the examination identified damage associated with wave interference patterns and unusual patterns of deformation and cracking associated with residual ferrite stringers within the austenitic matrix of the alloy. The characterization of the damage mechanisms leading to failure has direct relevance to ASME design criteria, to the selection of appropriate materials, and to inspection practices for impulsively loaded vessels.

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The Explosive Destruction System (EDS) was developed by Sandia National Laboratories for the US Army Product Manager for Non-Stockpile Chemical Materiel (PMNSCM) to destroy recovered, explosively configured, chemical munitions. PMNSCM currently has five EDS units that have processed over 1,400 items. The system uses linear and conical shaped charges to open munitions and attack the burster followed by chemical treatment of the agent. The main component of the EDS is a stainless steel, cylindrical vessel, which contains the explosion and the subsequent chemical treatment. Extensive modeling and testing have been used to design and qualify the vessel for different applications and conditions. The high explosive (HE) pressure histories and subsequent vessel response (strain histories) are modeled using the analysis codes CTH and LS-DYNA, respectively. Using the model results, a load rating for the EDS is determined based on design guidance provided in the ASME Code, Sect. VIII, Div. 3, Code Case No. 2564. One of the goals is to assess and understand the vessel's capacity in containing a wide variety of detonation sequences at various load levels. Of particular interest are to know the total number of detonation events at the rated load that can be processed inside each vessel, and a maximum load (such as that arising from an upset condition) that can be contained without causing catastrophic failure of the vessel. This paper will discuss application of Code Case 2564 to the stainless steel EDS vessels, including a fatigue analysis using a J-R curve, vessel response to extreme upset loads, and the effects of strain hardening from successive events. Copyright © 2010 by ASME.

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The Explosive Destruction System (EDS) was developed by Sandia National Laboratories for the US Army Product Manager for Non-Stockpile Chemical Materiel (PMNSCM) to destroy recovered, explosively configured,chemical munitions. PMNSCM currently has five EDS units that have processed over 850 items. The system uses linear and conical shaped charges to open munitions and attack the burster followed by chemical treatment of the agent. The main component of the EDS is a stainless steel, cylindrical vessel, which contais the explosion and the subsequent chemical treatment. Extensive modeling and testing have been, and continue to be used, to design and qualify the vessel for different applications and conditions. This has included explosive overtests using small, geometrically scaled vessels to study overloads, plastic deformation, and failure limits. Recently the ASME Task Group on Impulsively Loaded Vessels has developed a Code Case under Section VIII Division 3 of the ASME Boiler and Pressure Vessel Code for the design of vessel like the EDS. In this article, a representative EDS subscale vessel is investigated against the ASME Design Codes for vessels subjected to impulsive loads. Topics include strain-based plastic collapse, fatigue and fracture analysis, and leak-before-burst. Vessel design validation is based on model results, where the high explosive (HE) pressure histories and subsequent vessel response (strain histories) are modeled using the analysis codes CTH and LSDYNA, respectively. Copyright © 2008 by ASME.

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