شبيه سازي عددي شكل گيري جت حاصل از خرج گود و نفوذ آن در اهداف بتن مسلح

Numerical simulation of shaped charge Jet formation and penetration in the reinforced concrete targets

خرج گودها، موادمنفجره با قابليت نفوذ بالا هستند وبراي اهداف نظامي وغير نظامي استفاده مي شود. در كاربردهاي غير نظامي خرج گود در كارهاي تخريب، حفاري نفت و معدن استفاده مي شود. در كاربردهاي نظامي، خرج گودها در برابر انواع مختلف زره و همچنين سازه هاي امن استفاده مي شود. تحليل مسائل شكل گيري و نفوذ پرتابه هاي حاصل از خرج گود داراي پيچيدگي هاي زيادي است كه انفجار خرج، انتشار موج شوك درون خرج و اصابت موج به لاينر، تغيير فرم لاينر، شكل گيري پرتابه و در نهايت اصابت آن به سطح هدف و نفوذ در آن تا توقف كامل را شامل مي شود. با توجه به پيچيدگي رفتار هدف بتني درهنگام نفوذ جت، به مدل هايي نياز است كه بتواند اثر تغيير شكل هاي بزرگ، فشار هيدرواستاتيك ونرخ كرنش بالا وگسيختگي را مدلسازي نمايد. اگرچه مراجعي درمورد شبيه سازي نفوذ برخي خرج گودها در اهداف فولادي منتشر شده است ولي در خصوص نفوذ خرج گود در اهداف بتني، مرجع كاملي يافت نشد. هدف اول از اين تحقيق ارائه يك روش شبيه سازي عددي مطمئن به وسيله نرم افزارهاي موجودبر روي نفوذ خرج گود RPG-7 در اهداف بتني مي باشد. بدين منظور در سه مرحله نتايج شبيه سازي ها با نتايج آزمايشگاهي موجود مورد مقايسه قرار گرفت كه شامل تشكيل جت، نفوذ جت در اهداف فولادي و رفتار هدف بتني در مقابل نفوذ مي ياشد. هدف دوم تحقيق، تعيين ضخامت ايمن هدف، از جنس بتن معمولي در مقابل نفوذ جت RPG-7 وبررسي رفتار اين نوع بتن به لحاظ عمق نفوذ، شعاع حفره وگسيختگي دروجوه جلويي و پشتي هدف است.

Shaped charges are explosive devices with a high penetration capability and are used for both civilian and military purposes. In civilian applications shaped charge devices are used in demolition works, oil drilling and mining. In the military applications, shaped charges are used against different kinds of armors and Protective Structures. Analysis of forming and penetration of shaped charge projectiles issue is so complex that include explosion of charge, propagation of the shock wave in the charge, hitting the shock wave to the liner, liner deformation, projectile formation and finally striking projectile to target until it stops. According to the complexity of Behavior of the concrete during the Penetration of the Jet, the material models shoude be able to model the effect to large deformation, high hydrostatic pressure, high strain rate and failure. Although there are many references about Numerical simulation of shaped charge Jet in the armor targets, however it was not found any comprehensive sources about penetration of shaped charge in the reinforced concrete targets. Experimental results suggest that both kinetic energetic projectile and shaped charge are capable of destroying concrete targets, but the magnitudes of damage due to them are different. Compared with a kinetic energy projectile, a shaped charge has more significant effect of penetration into the target, and causes very large spalling area. In this paper, AUTODYN software was used to numerical simulation of shaped charge jet formation and target penetration. Different solver and modeling alternatives of AUTODYN were evaluated for jet formation and penetration problems. Euler solver of the AUTODYN was used to jet formation simulations and Lagrange solver was used for penetration simulations and both models were 2D axisymmetric. To simulate the penetration performance of the RPG – 7 charge, both the jet and the target were modeled by Lagrangian elements. The results of jet formation simulations, performed by the Euler solver were used to determine the properties of the jet. Penetration simulations were performed for a fixed 2 CD standoff distance. The jet material distribution obtained by the Euler solution at 2 CD standoff distance was mapped onto the Lagrange solver. The quality of this EulertoLagrange mapping was limited to the mesh resolution of the Lagrangian jet part. The first goal of this research is presentation of a reliable method to numerical simulation of Penetration of shaped charge of RPG – 7 into the concrete targets by use of available software tools. Therefore, simulation results were compared to the experimental results in three stages that Include the jet formation, jet Penetration in armor targets and behavior of concrete target against Penetration. The second goal is determination of the safe thickness of conventional concrete targets against the Penetration of RPG – 7 weapen and investigation of the behavior of this concrete type of target in terms of penetration depth, hole diameter and failure of the front and rear surfaces of the target.