بررسي و واسنجي مدل‌هاي رفتاري پرتابه و هدف در مدل‌سازي برخورد پرتابه‌ي فولادي با هدف بتني

Evaluation and calibration of concrete and steel material models for steel projectile impact on concrete target

در اين نوشتار، بررسي پارامتريك مدل RHT و واسنجي پارامترهاي آن در شبيه‌سازي مسايل ضربه‌ي بتن در نرم‌افزار اتوداين ارايه شده است. اين مقادير به عوامل معادله‌ي حالت و مدل‌هاي مقاومت، شكست و فرسايش آنها نسبت داده مي‌شوند. در اين نوشتار، با توجه به نياز به مدل‌سازي پرتابه، مدل جانسون-كوك معرفي شده است. بعد از معرفي مدل‌ها و زيرمدل‌هاي آن، تحليل يك نمونه‌ي تجربي ارايه و مطالعات پارامتريك بر روي پارامترهاي مدل‌ها ارايه شده است. موارد بررسي‌شده شامل: شبكه‌بندي، مقاومت پسماند، توان مقاومت شكست، توان نرخ كرنش كششي، توان نرخ كرنش فشاري، ثابت سطح شكست سالم، توان سطح شكست سالم، معيار فرسايش، خطاي انرژي، اصطكاك، سرعت پرتابه و شكل پرتابه است. نتايج مطالعات نشان داده است كه مدل رفتار بتن RHT با واسنجي مناسب پارامترها به‌خوبي قادر به تحليل مسايل ضربه در نمونه‌هاي بتني است.

The study of RHT parametric model and its calibration parameters have been used in the simulation affaivs if the concreto strike in Autodyn software.A reliable simulation of the concrete behavior can gain a significant understanding of the real physical mechanisms and the development of practical design guidelines based on parametric investigations using validated numerical models. The RHT model is one of them that widely used in impact and penetration analysis. The RHT model covers essentially all macro features of quasi-brittle materials such as concrete and rocks under high strain rate loading. However, the model was found to exhibit undesirable performance under some loading conditions. In the present study parametric analysis of the RHT model and its parameters calibration is carried out in impact and penetration analysis. The model performance is based on its constants values. These parameters are related to equation of state, strength , failure and erosion models. In the model, strain hardening and tensile and compressive meridian dependent to third invariant are considered. Softening behavior is modeled as nonassociative failure surface. Rate dependent tension and compression strength are considered.The model structure is based on plastic damage .Shear damage due to diavotoric stresses is considered too. Due to nessecary of steel projectile modeling, the Johnsoon-Cook model introduced further. The Johnsoon-Cook model is a strength model for metal response modelling at high strain rate and higt temperature loads.Following introduce of models and their submodels, analyze of an experimental test and parametric studies on concrete model , steel model state of equation and numerical aspects of analysis are presented. The investigated parameters are : mesh size, residual strength constant , residual strength exponent , tensile strain rate exponent, compressive strain rate exponent, intact failure surface constant , intact failure surface exponent, erosion criteria, energy error , friction, vlocity and shape of the projectile. Results show that using deduced modified parameters setting, the RHT model exhibits excellent results in modeling experimental tests.