(please excuse my bad English. I don't speak English)
I have to deal with an old hydraulic machine, recovered from a deposit. I have no knowledge on mechanical engineering. Only civil engineering.
The machine is for doing traction tests on steel bars (for example ribbed bars). The machine is old, from the 70’s or 80’s I guess.
It has a system for plotting the stress-strain/deformation chart on paper, but also has digital instrumentation added, which is being read by an old PC still running Windows XP, and it only provides the raw data from the instruments (as a text file).
The digital system seems to be added, I guess, in the 90’s, and comes with a handbook with some instructions (as for example, how to calibrate the machine), but no explanation on the internal workings.
I need to algorithmically process the raw data produced by the tests, to extract various parameters.
As I had been taught theoretically, the type of chart I should get, must look like this:
But off course, this is a real world physical test, so I get this kind of chart
I had been told that it starts with an accommodation phase which I should ignore, and I need to extract various information from the rest of the chart.
Now, here is a zoom of the “elastic phase”
I have no knowledge on why it behaves that way, but I conjecture (guess) that the traction force is increased in discrete steps, and between each force increase, the machine waits some amount of time for the steel bar slowly elongating until it reaches a stress-strain/deformation static equilibrium.
If that conjecture is correct, then I should isolate only the “static equilibrium” points to do calculations, and discard the other, because the other points are transient states, and the theoretical applications of the test are only for static behaviors (civil engineering applications). If the conjecture is correct, I should discard the transient states and retain only the static data for purposes of static mechanic applications of the traction test, which are the only theoretical applications of the test in civil engineering.
But off course, I have no knowledge on dynamic mechanics, and I may be making some huge mistake. I’m not a mechanical engineer.
So, the question is: Is the conjecture correct? Should I make some additional considerations?
[Edit] I would welcome if you can give me a book title, for reference, on the dynamical behavior of this type of machine.