Modelling the influence of gaseous products of explosive detonation on the processes of crack treatment while rock blasting

Purpose is mathematical modeling of fracturing as well as influence of gaseous products of explosive detonation on the changes in rock strength. Methods. Mathematical model, using foundations of Griffith theory, has been developed. To explain conditions of bridge formation while exploding lead azide charges, a two-stage description of solid particle condensation at a crack surface and inside it has been applied using the smoothed particle hydrodynamics. The analysis, involved electronic microscope, has helped verified the results experimentally. Findings. The effect of rock mass disturbance, resulting from explosive destruction, is manifested maximally right after the action. Subsequently, it decreases owing to the gradual relaxation of the formed defects. Therefore, an urgent problem is to develop ways slowing down strength restore of the blasted rock mass fragments. The process of rock fragment strength restoring may be prevented by microparticles getting into the microcrack cavities together with the detonation products. The research simulates their action. The data correlate to the simulation results confirming potential influence of the blasted rock on the dynamics of changes in the strength characteristics of the rock mass. Various compositions of charges with shells made of inert solid additions have been applied which solid particles can avoid the process of microcrack closure. Originality. For the first time, the possibility of deposition formation within rock micro- and macrocracks has been proposed and supported mathematically. Practical implications. Strength properties of the finished product and the energy consumption during impulse loading as well as subsequent mechanical processing of nonmetallic building materials depend on the strength properties of rock mass fragments. Hence, the ability to control the strength restore has a great practical value. Moreover, it can be implemented during the blasting operations.

High Speed, Localized Multi-Point Strain Measurements on a Containment Vessel at 1.7 MHz Using Swept-Wavelength Laser-Interrogated Fiber Bragg Gratings

Dynamic elastic strain in ~1.8 and 1.0 m diameter containment vessels containing a high explosive detonation was measured using an array of fiber Bragg gratings. The all-optical method, called real-time localized strain measurement, recorded the strain for 10 ms after detonation with additional measurements being sequentially made at a rate of 1.7 MHz. A swept wavelength laser source provided the repetition rate necessary for such high-speed measurements while also providing enough signal strength and bandwidth to simultaneously measure 8 or more unique points on the vessel’s surface. The data presented here arethen compared with additional diagnostics consisting of a fast spectral interferometer and an optical backscatter reflectometer to show a comparison between the local and global changes in the vessel strain, both dynamically and statically to further characterize the performance of the localized strain measurement. The results are also compared with electrical resistive strain gauges and finite element analysis simulations.

Numerical and Experimental Studies of the ŁK Type Shaped Charge

In this paper, the authors presented an analysis of the strengthening of the cumulative jet by the appropriate formation of the detonation wave front acting under the influence of high pressure on the liner. The analysis of the Polish ŁK cumulative charge was carried out using numerical methods in the ABAQUS program. Simulation studies were carried out on axial and peripheral initiations of the explosive cumulative liner. For this purpose, two types of cumulative charges were made with the same design parameters, differing only in the explosive detonation-initiation system. The impact of the elastomer insert on the focusing of the cumulative jet was verified. The influence of peripheral and axial initiation on a cumulative jet’s velocity was investigated. The authors proposed a new conical insert placed in the explosive between the pocket for the detonator and the liner, also changing the material of the cumulative liner. The smoothed-particle hydrodynamics method was used to describe the formation of a cumulative jet. The obtained results were verified experimentally, and they show that modification of the ŁK charge has a positive effect on jet amplification, with an inevitable collapse in the final stage of formation. The obtained results correlate with the literature’s data.

Fabrication of Composite Unidirectional Cellular Metals by Using Explosive Compaction

Development of a small and highly efficient heat exchanger is an important issue for energy saving. In this study, the fabrication method of unidirectional (UniPore) composite cellular structure with long and uniform unidirectional cells was investigated to be applied as a heat exchanger. The composite UniPore structure was achieved by the unique fabrication method based on the explosive compaction of a particular arrangement of thin copper and stainless steel pipes. Slightly smaller thin stainless steel pipes filled with paraffin are inserted into small thin copper pipes, which are then arranged inside bigger and thicker outer copper pipes. Such an arrangement of pipes is placed centrally into a cylindrical explosion container and surrounded with explosive. Upon explosive detonation, the pipes are compacted and welded together, which results in a UniPore structure with a stainless steel covered inner surface of unidirectional pores to improve the corrosion resistance and high temperature resistance performance. Two different composite UniPore structures arrangements were studied. The microstructure of the new composite UniPore structure was investigated to confirm good bonding between the components (pipes).