فصلنامه مواد پر انرژی
سال هفدهم شماره 3 (پیاپی 55، پاییز 1401)

Concrete is one of The Common Materials in Strategic Structures, and Because of it, Cloth Concrete (CC), which is also Called Fabric Reinforced Concrete (TCR), is Considered one of the Latest Technologies in the World. According to the General Applications of Cloth Concrete, the need to Investigate and Evaluate it in the Field of Military and Defense is Clarified, in the Present Research Cloth Concrete Targets with Dimensions of 120 x 120 mm and Thickness of 10 mm under the Influence of Steel Projectiles with Flat, Hemispherical and Conical Noses and the Diameter of 8 mm have been Simulated in Abaqus Software and Verified with Experimental Results, the Speed Of The Ballistic Limit of a Specific Cloth Concrete Sample and the Maximum Diameter of Destruction of the Front and Back Surfaces of the Sample have also Been Measured. the Failure Mechanism of the Cloth Concrete Samples is in the Form of Brittle Fracture and Fragmentation, which have Shown a Relatively Good Performance Against the Penetration Of Projectiles, so that the Area and Diameter of the Damage on the Front Surface of the Samples is Very Small and Sometimes as Much as the Diameter of the Projectile. also, on the Back Surface of the Samples, the Amount of Destruction is Acceptable and with the Increase of the Impact Speed, the amount of Destruction has also Increased Linearly. the Ballistic Limit Speed of Cloth Concrete Samples was also Obtained for Steel Projectiles with Flat, Hemispherical and Conical Noses as 124, 110 and 100 m/s, Respectively, which Indicates the Easy Penetration of the Projectile with a Conical Nose and the Difficult Penetration of the Projectile with a Flat Nose. Finally, the Performance of the Ordinary Concrete Panel alone and together with a Layer of Cloth Concrete on the Front Surface has been Evaluated, so that the Addition of the Layer of Cloth Concrete has been able to Reduce the Diameter of the Destruction of the Front Surface of the Target by 80% and the Kinetic Energy of the Projectile in a Period of Time. this Action has Greatly Improved the Impact Performance of Conventional Concrete Panels.

Binders are one of the most key components of solid composite propellants used in the military and space research industries. In present research, a PPG-PTHF-PPG triblock copolymer was synthesized as a binder using polytetrahydrofuran as an initiator and propylene oxide monomer through the cationic ring-opening mechanism with suitable molecular weight and high efficiency. The synthesized copolymer was investigated and identified with tools such as IR, NMR, GPC, and DSC. In the next, the optimal conditions for copolymer synthesis, including the choice of solvent type, the amount of solvent and catalyst, and the duration of the reaction, were investigated. After taking steps of copolymer synthesis, the curing of the copolymer was tested by different isocyanate curing agents, so the optimal amounts of curing catalyst, chain extender, and R ( mixture of N-100 and IPDI isocyanate agents) were obtained. The mechanical properties of elastomers were also evaluated through preparing dumbbell-shaped elastomers, which showed an 80% increase in elongation compared to the HTPB sample.

Aromatic and aliphatic isocyanates are used in the production of polyurethane. Dimeryl Diisocyanate (DDI), as an emerging biological aliphatic diisocyanate, has many advantages such as low toxicity, low vapor pressure and insensitivity to moisture and is one of the important isocyanates that can be used as a curing agent as well as a viscosity improver and plasticizer in the formulation of propellants, PBX and polyurethanes. In this research, dimeryl diisocyanate (DDI) has been investigated through a two-step method of optimization and influence on various factors. Thus, in the first step, the reaction of the acid dimer with the chlorination agent at room temperature led to the preparation of the acyl chloride compound with an efficiency of 98%, and in the second step, azidation of this intermediate using sodium azide and Curtius rearrangement produced the desired product with an efficiency of it created 89%. The product obtained by this method does not have the disadvantages of the phosgene method, such as high toxicity, unwanted side reactions, and difficult process conditions, and the overall reaction efficiency was 87%.

In this research, increasing the ballistic resistance of the steel armor body was done by Hardfaced Coating method. Welding on the sheet was done with a type of hard coated welding wire made of chromium, niobium-containing iron alloy and also a buffer type of manganese steel. After applying the hardened coatings on the steel sheets, the prepared samples were tested by impact ballistic test. Also, microstructural, hardness, elemental and metallographic analysis were done on the samples after the bullet impact. The thickness of the welded hard coating layer was measured as 8 ± 0.5 mm. The bullet penetration depth was measured as 0.5 mm in the sample with buffer and 1.5 mm in the sample without buffer. In surface hardened sheets, the fired bullet did not pass through the coated sheets. Buffer welding increased the ballistic resistance of the coated sheets against bullets. By forming a hard coating on the steel armor, a hard profile is created from the surface of the coating to the substrate, which plays an effective role in preventing the passage of bullets by creating appropriate flexibility. A composite structure consisting of martensite tempered with carbide particles that creates a hard area along with appropriate flexibility in the coating area, this structure can be the best structure for a coating on steel sheets to prevent bullet ballistic penetration. Cracks are created on the surface of the sample vertically and horizontally after the bullet hit, and these cracks are stopped inside the welding composite structure by chromium and niobium carbides. The mechanism for improving ballistic properties is to prevent crack growth on the weld surface. Surface hard welding with chromium and niobium iron alloy increases the ballistic resistance of steel sheets. Surface hardening coatings can be a suitable alternative to cost-effective methods of producing armor steels with high ballistic performance.

In this paper, the process of penetration of kinetic energy projectiles as the main part of two-stage anti-structure warheads in pre-drilled and damaged concrete targets was investigated using theoretical, numerical and experimental methods. Based on the dynamic cavity expansion theory, the study of the penetration of kinetic energy projectiles in pre-drilled concrete targets has been investigated. In this regard, by modifying the Teland model, the estimated damage to the concrete targets, as well as determining the geometric characteristics of the cavity and tunnel created on concrete purpose, then using empirical methods and numerical simulations, the analysis of penetration of leading projectiles with copper liners and cone geometry has been extracted on concrete purpose, tunnel diameter, geometry of the front and back cavity. The results of empirical tests and numerical simulations of the propagation of the propellants in concrete targets indicate the repeatability and proper matching of the two methods. Determining the diameter of the tunnel in damaged concrete targets, the analytical model of the Tandel has been corrected by considering the effects of the front cavity in the penetration process and by applying the damage effects in it, an optimal model for the penetration of kinetic energy projectiles in targets Damaged puncture has been developed. Comparison of the results of the corrective theoretical model with experimental results compared to other analytical models as well as numerical simulations has a good accuracy. The results according to the predictions show that the damage to a concrete target increases the depth of penetration to a significant extent compared to the pre-damaged state.

The increasing demand for highly pure crystalline materials with narrow Crystal Size Distribution (NCSD) leads related industries to utilize the Draft Tube Baffle (DTB) Crystallizers. The product Crystal Size Distribution (CSD) significantly alters by enhancing the mixing characteristics inside crystallizer, therefore acquiring a precise vision of hydrodynamics will help in designing and scaling up the DTB crystallizer. There are numerous studies on the flow field in the DTB crystallizers, but none of them investigates the interactions and effects of the internal arrangement of DTB crystallizers. In this study, the optimal configuration of three geometrical parameters (tube diameter, the ratio of tube diameter to baffle diameter, and the width of the annular settlement zone) was obtained by numerical simulation of the flow field in 18 DTB crystallizers. The interaction of parameters was studied by employing the general factorial method. Each crystallizer was divided into five compartments where various results such as the distribution of axial velocity, the turbulent kinetic energy, and streamlines were considered for data analysis. The results demonstrate that the hydrodynamics requirements in each compartment will be satisfied in crystallizer with 17.5 cm tube diameter, the ratio of tube diameter/baffle diameter=0.5, and the width of the annular settlement zone equal to the tube diameter.