Creep Transient Based On Obstacle Density
Obstacle is something which impedes or hinders the motion of another object. Rivers, cliffs and ridges are examples of natural obstacles which we try to overcome by building bridges i.e. go over the obstacle or we circumvent the obstacle by going on a track around it or we simply blast off the obstacle (mountain, huge rock) etc. and go through a tunnel. When we consider microstructures we deal with dislocations whose motion could be impeded by precipitates, dispersoids, grain boundaries or other dislocations as well. Obstacle could be a force generated due to some reaction at some totally different location. These obstacles might be present due to erroneous manufacturing process or they could be made available artificially for improvement of certain properties. Dislocations may go around, overor through to overcome the obstacles. The obstacle size, distribution, orientation, density, strength and inter-obstacle distance are important parameters to be considered. It is observed that higher the obstacle density, higher is the number of obstacles encountered and since energy is required to overcome an obstacle higher the number of obstacles more is the energy required. Hence creep deformation is less since dislocations travel a relatively small distance at the expense of greater energy.
Monte Carlo Simulation has been used in this experiment in which dynamic variables are updated at each time interval with random numbers to study the microscopic and dynamic behavior of systems. Here we have used stochastic cellular automation in which each element is characterized by strength parameter 's' and slip probability. Load shedding principles i.e. load transfer to neighboring sites when slip occurs is considered.
The model assumes that for small strain regime and materials with low hardening rates strain hardening and recovery processes can be ignored, that materials respond to plastic deformation in the same way because the observed behavior is due to a large number of discrete events coupled through load transfer, and that obstacle density and its behavior does not change during the deformation process.