Carbamide Peroxide, an adduct of Urea and Hydrogen Peroxide, is commonly used in the cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. However, it exhibits explosive properties and can be easily manufactured from readily available household chemicals, making it a potential emerging threat. We carried out a detailed performance assessment, combining experiments, thermochemical calculations and numerical simulations and highlighted a good level of agreement between experimental data from lab, field and underwater firings. A maximum detonation velocity of 3.65 km/s was recorded for unconfined 25 kg UHP charges at 0.85 g/cm 3 (200 mm charge diameter). We determined in these conditions an infinite diameter detonation velocity of 3.94 km/s. These results are also consistent with previous results obtained at small scale under heavy confinement. Airblast measurements highlighted an average 40 % TNT equivalence for impulse and 55 % for peak overpressure at short distance, which are in good agreement with the 57 % (Power Index) calculated from Explo5, while 50 % for bubble energy (explosive power) and 20 % for shock pressure (brisance) were obtained from underwater experiments. The use of different experimental approaches has proven useful to characterise the performances parameters of a non-ideal explosive for risk assessment purposes. K E Y W O R D Sdetonation, non ideal explosive, performance, urea hydrogen peroxide | INTRODUCTIONCarbamide Peroxide or Urea Hydrogen Peroxide (UHP) is commonly used in the dental, cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. This adduct can also be easily manufactured from readily available household chemicals. Like other oxidisers such as ammonium perchlorate [1] or ammonium nitrate [2], UHP exhibits explosive properties [3,4] and could represent a potential emerging threat. Determining UHP detonation performance parameters is hence important for safety purposes.Because there is a need to predict large-scale explosive behaviour from small-scale experiments [5], our

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Detonation chambers (either mobile or fixed) are used worldwide for a wide range of applications. At present, a 1/7 scale model of a 1 ton detonation chamber is available for extended testing in Belgium. The chamber is a single wall cylindrical vessel with semielliptical ends. Each time an explosive charge is fired in the vessel, that vessel is submitted to a number of deformation cycles. A series of strain gauges measures the deformation of the vessel walls. Experimental peak strains and vibration frequency can be compared with predicted values based on simple formulas. Measured values are reasonably close to the estimated values. The influence of the shape of the charge is studied. The shape has an important influence on the chamber response. For a fixed charge mass, a spherical charge causes less deformation than a cylindrical charge and is therefore advantageous from a fatigue point of view.

Vessels subjected to internal impulsive loadings, such as those used for controlled-detonation chambers, can be designed for a single impulsive load application or for multiple impulsive loads. Design of a single-use vessel may take advantage of the capability of the vessel material to absorb energy through elastic-plastic behavior, provided that the public health and safety is protected, even though the owner’s investment in the vessel may be compromised because of severe distortion and potential loss of containment functionality. However, when the vessel is designed to contain multiple internal impulse loads, the usual design practice is to require completely elastic response or, at most, very localized elastic-plastic behavior. A recently approved ASME Boiler & Pressure Vessel Code, Section VIII, Division 3 action (Code Case 2564-2) provides limits for the accumulated plastic strains in such vessels, including a limit on the accumulated plastic strain averaged across the wall thickness of the vessel, that are sufficiently conservative to permit the design of vessels for both single-impulse and for multiple-impulse applications. Analytical or experimental demonstration to meet the Code Case 2564-2 strain limits is straightforward for the single-impulse vessel design and is relatively straightforward for multiple-impulse vessel designs when the vessel response to any of the individual impulsive loads is nearly elastic. However, when the design-basis impulsive loading for a multiple-impulse vessel design leads to significant plastic straining, the demonstration of design adequacy becomes extremely complex, raising issues of impulsive loading sequences (since elastic-plastic response is load-path dependent, what is the temporal order of the impulse loadings?) and demonstration of shakedown to elastic or near-elastic behavior. In such cases, an analytical demonstration of design adequacy may be impractical, while an experimental demonstration may be both practical and illuminating, especially if the demonstration is carried out at a scale that is both economical and convincing. Here, a one-seventh-scale model of a controlled-detonation vessel is used as the basis for demonstrating the effect of shakedown to essentially elastic behavior, with no further accumulation of plastic straining, along with the satisfaction of ASME Code Section VIII, Division 3, local ductility exhaustion requirements. The experiments on a scale model vessel have proved that the phenomenon of shakedown can be demonstrated experimentally, for internal detonation loadings that initially led to plastic strains up to 0.7%.

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