Learning Forum

[to2020]

Hi, nI am doing a bond test with the rebar and concrete. When I apply 5mm of displacement on the rebar (over 200-300 substeps). When I want to look at the stress on the rebar, should I be using maximum principal stress or equivalent stress (von-mises)? nFor e.g. I have inputted the tangent modulus as 0 and have the yield stress at 500MPa. When I solve and look at the maximum principal stress, it shows like over 1000MPa in the rebar (when the yield stress is at 500MPa and ultimate tensile strength is at 560MPa). Whereas the von-mises shows it is approximately 500MPa? nBecause the maximum principal stress doesn't seem to be correct. I have previously posted about this (/forum/discussion/comment/92045#Comment_92045) and I have tried the solution suggested by one of the forum coordinator (but when I turn on the large deflection, I get an error). nIf someone could please explain or give some suggestion, it would be greatly appreciated. nThanks in advance. n

[Ashish Khemka]

nnAre you using a bilinear hardening model? If tangent modulus is zero then you may see a perfect plastic behavior. Please confirm.nnRegards,nAshish Khemkan

[to2020]

nYes, I am using bilinear hardening model.n I have tried yield stress at 500MPa, ultimate tensile strength of 560MPa and Tangent Modulus of 0. In this case, the equivalent stress on the bar seems reasonable as it is like the yield stress. But the maximum principal stress in the rebar seems incorrect as I get very high values (over 1000MPa)nI have then tried yield stress of 500MPa, ultimate tensile strength of 560MPa and Tangent Modulus of 6000 MPa (which is like typical in reinforcement bars). When I do this, the equivalent stress in rebar also goes above ultimate tensile strength (like over 1000MPa) and the maximum principal stress also is very high (over 1000MPa). nnCould you please help with why this is occurring and what I could do? nThanks! n

[Ashish Khemka]

nnAfter the yield point the material behavior is again linear but with reduced modulus. The value of ultimate strength that is entered is useful for factor of safety calculations but has no relation with the bilinear model. You can define multiple points (plastic strain vs stress) on stress-strain curve using Multilinear Hardening model.Regards,nAshish Khemkan

[to2020]

nnYes I may have to do the multilinear hardening model because I don't want the material to exhibit perfect plasticity after the yield stress and ultimate strength because the bar in experiment would fail. nI have the tensile data for the rebar, how can I input the data to the model? nThe above is a screenshot for when it roughly reaches the yield stress. How can I calculate the values to input to the multilinear model?Thanks! n

[Ashish Khemka]

nnI have replied to your other query on multilinear model. Please see if this helps.nnRegards,nAshish Khemkan