I am testing a new version of an old handle for refrigerators. The handle is basically an aluminium pole with two brackets at each end holding it to the door. Changes have been made to both the handle and the brackets, so I try to test them separately, sort of. I've tested the new handle with the old brackets and am now testing the old handle with the new brackets.
The opening force, applied at the middle of the handle, is about 60 Newtons, possibly even lower due to the nature of the test.
After about 80,000 openings, the old bracket failed. I'm thinking this is either a matter of fatigue or something was a bit off with the test equipment.
With the FEA software we have, I can only look at separate parts, so when calculation the forces acting on the bracket I have considered the handle as being solidly mounted at both ends, resulting in a force of F/2 and a moment of F*L/8 acting on each bracket. The resulting Von Mises stress, as well as max principal stress, is above Rm for the zinc alloy used, which is about 330 MPa.
obviously, something is wrong with my analysis. I'm quite certain that it's the fact that I cannot take into consideration the flex of the door and handle which should be making life easier for the bracket. So what do I do? Reduce the applied forces and moments in the analysis until I get the desired max principal stress?
Also, does anyone know where I can find fatigue diagrams for zinc alloys? aluminum alloys?
The opening force, applied at the middle of the handle, is about 60 Newtons, possibly even lower due to the nature of the test.
After about 80,000 openings, the old bracket failed. I'm thinking this is either a matter of fatigue or something was a bit off with the test equipment.
With the FEA software we have, I can only look at separate parts, so when calculation the forces acting on the bracket I have considered the handle as being solidly mounted at both ends, resulting in a force of F/2 and a moment of F*L/8 acting on each bracket. The resulting Von Mises stress, as well as max principal stress, is above Rm for the zinc alloy used, which is about 330 MPa.
obviously, something is wrong with my analysis. I'm quite certain that it's the fact that I cannot take into consideration the flex of the door and handle which should be making life easier for the bracket. So what do I do? Reduce the applied forces and moments in the analysis until I get the desired max principal stress?
Also, does anyone know where I can find fatigue diagrams for zinc alloys? aluminum alloys?