Effect of Annealing Temperature on Dislocation Loop Absorption And Evolution in Fe by Molecular Dynamics Study

As the basic material in reactor pressure vessel (RPV), Fe endures amounts of irradiation in the entire lifetime. Many irradiation defects such as dislocation loop are generated which affect the macroscopic mechanical properties. In this paper, we use the molecular dynamics method to investigate the effect of annealing temperature on dislocation loop absorption and evolution. The annealing process contains four steps: At first, the temperature increases from room temperature (300K) to annealing temperature. The annealing temperature is set as 600K, 700K, 800K, 900K and 1000K respectively. Then the system maintains at annealing temperature for adequate time to evolve. After that, the temperature recovers to room temperature. Finally, the system evolves at room temperature to get the final configuration. The diameters of 1/2 <111> and <100> dislocation loop are 5.1 nm and 1.2 nm, respectively. The dimension of simulation cell is defined as 29.6nm × 20.2nm × 21.0nm with 1080455 atoms. Based on annealing simulation, we could obtain and analyze the microstructure evolution of dislocation loop. Apart from that, we also investigate the effect of annealing rate (4.29 K/ps, 6.00 K/ps, 10.00 K/ps and 30.00 K/ps) on the number of defect atoms and dislocation length during annealing process. Here under periodic boundary conditions the system is allowed to relax in all three directions independently. Results show that temperature has significant impact on the absorption and evolution of dislocation loop. However, temperature can improve the maximum values of defect atoms and accelerate absorption process from stage II to stage I when temperature is 900 K and 1000 K. In contrast, annealing rate has negligible impact on whether the number of defect atoms or dislocation length during the absorption and evolution of dislocation loop. These results are meaning for understanding the temperature effect on dislocation loop.

FEM Analysis of Glass Lens Molding Press

Glass molding press is an efficient and promising process for glass lens manufacturing. Molding temperature and velocity are crucial factors for pressing, and the annealing rate directly influences the residual stress and volume change of the final lens. The research contributes to studying the key factors that influence the quality of the molded lens. In the paper, by incorporating stress relaxation and structural relaxation of the viscoelastic material, numerical simulation is undertaken to determine the proper process parameters. Furthermore, the whole process of a spherical lens molding is simulated to predict the final residual stress and volume change, also the influence of different annealing rates is estimated.

Sensitivity of forest plan value to parameters of simulated annealing

Simulated annealing (SA) is a heuristic technique popular in forest planning, providing solutions close to optimality in reduced computation time. The present study challenges the common approach used to establish the parameters of SA that mimic physical processes by proving that slow cooling or large initial temperatures do not necessarily lead to optimal solutions. The study has two objectives: (1) to identify the parameters (i.e., initial temperature and annealing rate) that could supply close to optimal results with reduced experimentation time and (2) to assess the impact of parameters determining SA performances. Using three forest inventory data sets from British Columbia, we investigated the influence of initial temperature, annealing rate, and numbers of runs on forest planning solutions using a replicated completely randomized design organized as a factorial experiment within a repeated-measures framework. The optimal solution seems to be little influenced by the number of runs; our findings indicate that the combination of initial temperature and rate of annealing is critical in obtaining superior results. Furthermore, the selection of the SA parameters seems to be dependent on the harvest age, which indicates that the parameters should be selected considering whether or not a stand is harvested more than once during the planning period.