Hello to all,
I am a mining engineer working on crack response approach to liability for the damage to the structures (residential and other) caused by blast induced ground vibrations. current crack response approach states that liability exists only if the crack response in the form of changes in the crack width to blasting factors is larger than the crack response to environmental changes (air temperature and humidity). I disagree because crack response to blasting is dynamic process and response to environmental changes can be considered static. My question is, how to model dynamic crack response and what values should I monitor.
I have tried to perform a transient analysis in ANSYS code. first I recorded crack responses to both blasting and nonblasting influences. peak to peak displacement (crack opening) for non blasting influence is 50 micrometers over 17 hours and peak to peak displacement for blasting influence was 20 micrometers over 10 miliseconds. I applied these displacements as loads and used loadstep options to set the excitation time. Plain stress condition is assumed, 8 node quad element (plane 82) was used and the material is concrete. I can plot stress intensity in the crack tip over time, also strain energy over time etc.
My assumption is (and I must say that I'm not an expert for fracture mechanice, more a novice) that in 17 hours of exposure stresses rise slowly and there is enough time for them to redistribute. Vice verca, under the impulse influence of blasting ground vibrations, stresses would rise rapidly with no time to redistribute along the constructive element. Hence I should have higher readings for stress and I do not. It seams to me that in my analisys stress is only dependant on the opening of the crack. what am I doing wrong?
Thanks