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How do I change loading rate to speed up quasi-static simulation in Abaqus/Explicit?
Big Picture: I am trying to perform a quasi-static, displacement controlled, 3-point bend simulation on a 2D notched beam. My simulation size is about 7100 variables. Ultimately, I am trying to run this simulation using a VUMAT implementing a damage accumulation material model, but for right now I am using the built in Elastic model while I figure out how to manipulate loading rate. I want to run this model for at least 100 cycles which will be done using steps. I am trying to get the simulation to run in a reasonable amount of time so that I can get information quickly. I have been able to use Mass Scaling to speed up the model, which seems to work, but does distort my results. The only information I want from the simulation is reaction force and displacement, this is because I want to calculate stiffness of the structure (i.e. force divided by displacement). A lot of the documentation online talking about doing Quasi-Static simulations using Abaqus Explicit says that the two ways of speeding up the simulation are mass scaling and controlling loading rate.
Problem: I want to compare the results using the two methods and see if using a faster loading rate will help with the distortion of my results. I have tried to figure out how to control loading rate but my results are not making sense. I have stepped back from my simulation and am working with a 2D, one by one, square plate while I try to figure out how to manipulate loading rate. Basically, my question is, how do I control loading rate using Abaqus Explicit?
What I have tried: Under the amplitude keyword there are 4 numbers in a row separated by commas. I have tried adjusting the third number both greater than 1 and less than 1. From what I understand in both the Abaqus documentation and what I have read on line these numbers come in pairs such that the amplitude follows this: time_0, amplitude_0, time_1, amplitude_1, time_2, amplitude_2. I have been using this such that: time_0, amplitude_0, time_1, amplitude_1 where 0 represents the beginning of the step and 1 represents the end of the step. Therefore, I have manipulated the number representing time_1.
From what I can understand it seems like reducing this number to a value less than 1 would increase the rate at which loading is applied and therefore reduce the time the simulation runs. I say this because a rate is an event divided by time. So, if time is decreased the rate should increase.
My results: It is hard to see in the two graphs but essentially all graphs look like the light green one. In that the data points are not evenly spread out throughout the x-axis. The simulation goes from 0,0 to the second point and then all other points are in a vertical line. It seems like the graphs are converging, but the vertical lines seem odd. Even if I apply this to my notched beam simulation with 7100 variables, it doesn't speed up at all.
System: Abaqus 6.11 run on a Unix cluster
Input file for the simple Square plate I have been practicing with
Input file for the Notched beam I am using as my actual model
2 Graphs showing the results from my square trial