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Showing 2 results for Johnson-Cook Model
Sh. Amini Nejad, G.h. Majzoobi, S.a.r. Sabet,
Volume 20, Issue 2 (1-2020)
Abstract
In this research, the effect of strain rate on the tensile behavior of the graphene/epoxy nanocomposites was investigated. The specimens were prepared for 0.05, 0.1, 0.3 and 0.5 wt.% graphene oxide and were subjected to tensile tests at different strain rates. The experimental results showed that the maximum improvements in the tensile strength, the modulus, and nanocomposite were 9%, 16%, and 0.1 wt.%, respectively. Also, the results indicated that the epoxy and its nanocomposites were sensitive to the strain rate. The rate sensitivity decreased with the increase of the graphene weight percentages. Moreover, it was shown that by increasing the strain rate, the tensile strength and modulus for pure epoxy were improved by 15.8% and 16.8%, respectively. In this study, the appropriateness and applicability of the Johnson-Cook material model for describing the stress-strain relation of the nanocomposites were examined by a combined experimental-numerical-optimization technique. The numerical simulations were carried out using Abaqus commercial program and the optimizations were performed using the Surrogate modeling. The results showed that the Johnson-cook model is not accurate at very low strain rates. However, the accuracy of the model was remarkably improved by increasing the graphene weight percentage or increasing strain rate.
Fatemeh Negahdari, Behnam Akhoundi,
Volume 22, Issue 10 (10-2022)
Abstract
In orthopedic surgery, the drilling process is used to internally fix the fracture zone. During bone drilling, if the temperature exceeds the limit of 47 °C, it results in altered bone alkaline phosphatase nature, occurrence of thermal necrosis, non-fixation and inadequate bone fusion In order to investigate the effective parameters of the drilling process, after three-dimensional modeling of the femur bone in Mimics software and determination of bone coefficients based on the Johnson-Cook model, numerical simulation of the cortical and trabecular bone oblique drilling process have been performed. The drilling process was performed in both normal and high speed modes based on reverse heat transfer theory using DEFORM-3D software. The results of numerical simulation after validation with experimental results showed that this theory is capable of estimating the temperature and heat flux in this process and the occurrence of necrosis in both processes (normal and high speed) is imminent. The temperature in the drilling area of the trabecular bone is higher than the cortical bone at all speeds and feed rates and the axial force of the trabecular bone is less than the cortical bone at all speeds and feed rates. The optimum point leading to the minimum temperature in normal drilling of trabecular and cortical bone is the feed rate of 150 mm/min and the rotational speed of 2000 rpm. This optimum point is obtained in the high-speed drilling of trabecular and cortical bone at the feed rate of 150 mm/min and rotational speed of 4,000 rpm and 7,000 rpm.
