Numerical Modeling and Simulations of Twinning-Induced Plasticity Using Crystal Plasticity Finite Element Method

In the current work, a fully implicit numerical integration scheme is developed for modeling twinning-induced plasticity using a crystal plasticity framework. Firstly, the constitutive formulation of a twin-based micromechanical model is presented to estimate the deformation behavior of steels with low stacking fault energy. Secondly, a numerical integration scheme is developed for discretizing constitutive equations through a fully implicit time integration scheme using the backward Euler method. A time sub-stepping algorithm and the two-norm convergence criterion are used to regulate time step size and stopping criterion. Afterward, a numerical scheme is implemented in finite element software ABAQUS as a user-defined material subroutine. Finally, finite element simulations are executed for observing the validity, performance, and limitations of the numerical scheme. It is observed that the simulation results are in good agreement with the experimental observations with a maximum error of 16% in the case of equivalent stress and strain. It is also found that the developed model is able to estimate well the deformation behavior, magnitude of slip and twin shear strains, and twin volume fraction of three different TWIP steels where the material point is subjected to tension and compression

Curve Fitting for Damage Evolution through Regression Analysis for the Kachanov–Rabotnov Model to the Norton–Bailey Creep Law of SS-316 Material

In a number of circumstances, the Kachanov–Rabotnov isotropic creep damage constitutive model has been utilized to assess the creep deformation of high-temperature components. Secondary creep behavior is usually studied using analytical methods, whereas tertiary creep damage constants are determined by the combination of experiments and numerical optimization. To obtain the tertiary creep damage constants, these methods necessitate extensive computational effort and time to determine the tertiary creep damage constants. In this study, a curve-fitting technique was proposed for applying the Kachanov–Rabotnov model into the built-in Norton–Bailey model in Abaqus. It extrapolates the creep behaviour by fitting the Kachanov–Rabotnov model to the limited creep data obtained from the Omega-Norton–Bailey regression model and then simulates beyond the available data points. Through the Omega creep model, several creep strain rates for SS-316 were calculated using API-579/ASME FFS-1 standards. These are dependent on the type of the material, the flow stress, and the temperature. In the present work, FEA creep assessment was carried out on the SS-316 dog bone specimen, which was used as a material coupon to forecast time-dependent permanent plastic deformation as well as creep behavior at elevated temperatures and under uniform stress. The model was validated with the help of published experimental creep test data, and data optimization for sensitivity study was conducted by applying response surface methodology (RSM) and ANOVA techniques. The results showed that the specimen underwent secondary creep deformation for most of the analysis period. Hence, the method is useful in predicting the complete creep behavior of the material and in generating a creep curve

Exploration of drug addiction prevalence among young generation of Pabna district, Bangladesh

Drug addiction has spread at a frightening rate in the whole world, especially in the South Asian countries such as Bangladesh which needs to be analyzed, discussed and eradicated. This present survey based study was conducted with an aim to discover the scenery of drug addiction in northern region of Bangladesh. Researchers also uncovered the factors, problems and effects of drug addiction, age of first drug used, source of money to buy drugs and effective measures to prevent this problem etc. Total 600 youngsters from Pabna, a northern part of Bangladesh were directly interviewed by using self-construct questionnaire. Age range of the participants was between 12 and 35. Result showed, low income participants were highly addicted (58.62%) and family problems (43.93%) were the most prevalent cause of addiction. Participants involved in sports had lower drug addiction propensity (36.38%). Addicted young consumed more nicotine (95.04%), alcohol (63.93%) and marijuana (44.28%). Among addicts, youngs started using drugs mostly between 15 to 18 years age. Parent’s income (42%) was the prime source of money to buy drugs and 91% of addicted young faced complications. Counseling (71.2%) and systematic penalty (66.4%) were the best preventive measures for drug addiction. The young generations of Bangladesh are cankering their crucial youth time in addiction and they should be rescued by counseling, monitoring and treating them with care and affection from the parents, society and government. Keywords: Drug Addiction, Survey, Young People, Pabna, Banglades