Session: HT-02-01 Structures under Extreme Loading Conditions (Joint Topic)

Paper Number: 60441

Start Time: Thursday, July 15, 2021, 09:00 AM

60441 - A Proposed Methodology for ECV Fitness-for-Service Evaluation 

A PROPOSED METHODOLOGY FOR ECV FITNESS-FOR-SERVICE EVALUATION

T. Duffey and J. Gibson

Explosive Containment Vessels (ECVs) are widely used throughout the world in such diverse applications as bomb disposal, to perform dynamic experiments, storage and manufacturing, and to contain explosive detonation products and protect surroundings from blast effects [1]. These vessels generally fall into two categories: Single use, in which the vessel undergoes significant plastic deformation; and multi-use, in which the response is primarily elastic.  For multi-use ECVs (i.e. ECVs used for more than one explosive event), both fatigue and ratcheting are potential failure mechanisms and therefore primary concerns. Fitness-for-service methods for evaluation of fatigue are well developed [2] and adequately address ECV fatigue [3]. Analytical methods for evaluation of ratcheting exist. However, there are significant remaining uncertainties in the implementation of a suitable material model for finite-element evaluation of ratcheting/shakedown, as discussed, for instance, by Kalnins and others [4].

In this paper, an experimentally based methodology of fitness-for-service evaluation is introduced that utilizes change-in-thickness measurements pre- and post-test to determine the propensity of the structure to ratchet or to shake down. Focus in this work is on in-plane membrane strains in the vessel. The methodology is illustrated using measured thickness changes on spherical explosive containment vessels. It is intended to eliminate or diminish the need for detailed, finite-element calculations of ratcheting/shakedown that rely upon a ratcheting material model that is challenging to adequately develop.  An example, based upon measured thickness changes in an explosively loaded containment vessel, is presented. An overview of finite element calculations for ratcheting/shakedown is included. Limitations of the procedure and current applicable consensus-code requirements are discussed.

Change-in-thickness measurements, fielded on an initially pristine 3ft spherical ECV, were performed to illustrate the viability of the methodology. The measured plastic in-plane strain was found to be a significant fraction of the membrane strain limit given in Section VIII, Division 3 for impulsively loaded vessels, after a single explosive loading event. To date, this is a work-in-progress and change-in-thickness measurements have been monitored for only this single event. Therefore, these preliminary results cannot predict whether shakedown or ratcheting will occur in subsequent events without additional future testing. The results presented are preliminary; efforts are underway to collect supplementary test data. Additionally, attempts are being made to increase accuracy of thickness measurements, with the intent to reduce error between pre- and post-test thickness comparisons.

[1]. K.W. King and J.H. Waclawczyk, “Blast Containment Chamber Development and Testing”, PVP2006-ICPVT-11-93208, Vancouver, BC, Canada, July 23-27, 2006.

[2]. API-579-1/ASME FFS-1, “Fitness-For-Service”, ASME International and American Petroleum Institute, Washington, DC, 2016.

[3]. T.A. Duffey and K.R. Fehlmann, “Fitness-for-Service Strategies for Impulsively Loaded Vessels”, ASME Journal of Pressure Vessel Technology, Vol. 143, pp. 031201-1 to 031201-6, 2021.

[4]. A. Kalnins, J. Rudolph, and A. Willuweit, "Using the Nonlinear Kinematic Hardening Model of Chaboche for Elastic-Plastic Ratcheting Analysis", ASME Journal of Pressure Vessel Technology, Vol 137, No. 3, p. 031006, 2013.

Presenting Author: Joshem Gibson Los Alamos National Laboratory

Authors:

Thomas A. Duffey TA Duffey, Consulting Engineer
Joshem Gibson Los Alamos National Laboratory