Numerical evaluation of craters formed by RDX on different ground during detonation

Energetic materials are widely employed in numerous application areas due to their high-energy chemical structures and their relative economic efficiency compared with alternative technologies. In general terms, they are substances capable of rapidly releasing stored chemical energy as heat, gas, and pressure when subjected to stimuli such as impact, shock, friction, or thermal ignition. They are commonly classified as explosives (e.g., TNT, PETN, RDX), propellants (e.g., black powder) and pyrotechnic compositions. In this thesis, attention is focused on high explosives as a sub-group of energetic materials, and their interaction with wooden targets is examined in detail. In the literature, explosives have been studied in a variety of contexts, including defense industry applications (Erdik, 2017), civil and military engineering (Atasoy, 2019), industrial operations such as mining and demolition (Nagy, 2015), and fundamental research on reaction mechanisms and detonation behavior (Menekşe, 2024). These studies highlight the central role of high explosives in technological development and national security. Parallel to conventional explosives, new nitro-organic energetic compounds—particularly azides and nitramines are being developed to achieve higher performance, controlled sensitivity, and improved environmental behavior. Compounds such as 2,4,6-triazido-1,3,5-trinitrobenzene and 2-azido-1,3-dinitropropane are cited as promising candidates for next-generation conventional explosives (Şen, 2013), illustrating the dynamic and rapidly evolving nature of research in energetic materials. Among modern high explosives, cyclic nitramines (CNAs) such as RDX are of particular importance. Over recent decades, they have been extensively investigated in terms of combustion and detonation reaction modeling, as well as their experimental behavior under different loading and confinement conditions (Ermolin & Zarko, 1998; Strunin & Nikolaeva, 2010; Strunin & Nikolaeva, 2013). These studies address parameters such as reaction rates, pressure–time histories and temperature profiles, and clarify how microstructural features affect the propagation of the reaction front. The resulting knowledge contributes to safer design, improved damage prediction and optimized explosive formulations for specific applications. As the use of explosives in both military and civilian settings expands, understanding how they behave on different substrates and ground conditions has become increasingly important. The interaction between an explosive charge and its target environment depends not only on the physical and chemical properties of the explosive itself, but also on the mechanical and structural characteristics of the impacted material. Detonations in or on soil, rock, concrete or wood produce distinct crater geometries and damage patterns. Consequently, there is a need for systematic studies that examine explosive–target interaction, with particular emphasis on crater formation, energy dissipation and stress-wave propagation, and that quantitatively relate target properties to observed crater geometries. The aim of the present study is to investigate the destructive effects of RDX detonations on wooden surfaces, to compare experimentally observed crater formations with established empirical crater formation equations, and to determine crater coefficients for different wood types. The study thus seeks to develop a comparative framework linking the mechanical properties of selected woods—such as hardness and strength—to the size and morphology of craters generated by controlled RDX detonations. In this way, the work contributes to the understanding of how high explosives interact with anisotropic, heterogeneous and relatively low-density materials such as wood, which are frequently encountered in structural and infrastructural systems. Although the literature contains many studies on crater formation in soils, rocks and concrete, systematic investigations focusing on wooden surfaces are scarce. Yet wood is a complex, anisotropic material whose behavior is strongly influenced by species, density, grain orientation, moisture content and internal defects. These factors, arising from the cellular and fibrous structure of wood, cause substantial variation in surface hardness and strength among species. Moreover, modification techniques such as densification, impregnation and chemical treatment can significantly alter the microstructure and mechanical properties of wood. Experimental investigations that relate such tailored properties to crater morphology are therefore crucial for the rational design of wood-based protective or sacrificial elements in blast-exposed structures. In the experimental phase, different wood specimens were selected to represent a range of species and mechanical properties. Their hardness and strength values were measured using standard mechanical test methods prior to detonation. Subsequently, RDX charges of carefully calculated mass were detonated on the wooden surfaces. After each detonation, the diameters and depths of cavities and cracks were measured with appropriate instruments, providing a detailed quantitative description of crater geometry. The experimental results were evaluated in the light of empirical relationships used to model crater formation. Among the numerous equations proposed in the literature, those used by Östmark et al. (2007) and Zhurova et al. (2007)—based on the Kistiakowsky–Wilson rules and expressed in Kamlet–Jacobs form—were found appropriate for the objectives of this study. In these formulations, detonation velocity (D) and detonation pressure (P) are given by D =1.01(N0.5)(Mave Q)0.25(1+1.30) and P=1.558ρ2(N)(MaveQ)0.5 where N is the moles of gaseous products per gram of explosive, MaveMMave is the average molecular weight of these products, Q is the heat of detonation, and ρ\rhoρ is the explosive density. These relations enable estimation of the fundamental detonation parameters of RDX and their connection to crater dimensions on wooden targets. By combining the measured crater diameters, depths and volumes with the calculated detonation parameters, crater formation coefficients were derived for each wood type. These coefficients provide compact, comparable indicators of the blast resistance of different woods and support predictive modeling and engineering design where damage to wooden elements under detonative loads must be assessed. The detonation tests were performed using a 2.5 kg Drop Weight Impact device, with drop heights ranging from 60 cm to 4 cm. Adjusting the drop height controlled the impact energy and allowed the determination of initiation thresholds and safe operating ranges for the RDX charges. The resulting data were used to identify detonation limits and to calculate associated pressure and energy values for RDX on wooden surfaces. After establishing suitable charge masses and initiation conditions, RDX was detonated on pre-characterized specimens, and the resulting craters were quantified and correlated with mechanical properties such as compressive and bending strength and surface hardness. From these measurements, reference crater profiles were defined for each wood type and used to compute crater formation coefficients that express the relationship between RDX detonation conditions and damage to wooden targets. For broader applicability, these coefficients were normalized with respect to both RDX and TNT, two widely used high explosives. This normalization enables approximate translation of findings from one explosive system to another, subject to appropriate scaling. In summary, the study presents a systematic experimental and analytical investigation of crater formation on wooden surfaces subjected to RDX detonations. By integrating mechanical characterization, controlled blast testing, empirical modeling via Kamlet–Jacobs equations and the derivation of crater formation coefficients normalized to RDX and TNT, it offers a coherent framework for assessing the response of wood to high-explosive loading and enriches the broader body of knowledge on explosive interaction with anisotropic, heterogeneous target materials. Keywords: Energetic materials, High explosives, Crater formation, RDX explosion, Wood surface behavior