Hi
I have to figure out the forces acting upon the joints of a truss-like section. I have attached schematic, it is relatively simple. I'm really rusty with my strucutral mechanics.
The black dots on the drawing represent fixed joints. What would be the forces acting upon those joints? The...
JJPellin
I realise I did not do a good job of describing the situation very well. It is becaue I myself did not have all the required data and information. I have only seen the machine in opperation once and have had to make several assumptions in solving the problem. I myself have been...
Hey Guys
Thanks for all your help and suggestions. I figured out that the loads on the shaft from the rubber components along with the vibrational stress are what caused the shaft to fail. Once the modification was made, the vibrational stress was reduced greatly on the shaft. Also, the new...
BobM3
It fractured on the other side (not the motor side) of the bearing. Initially I dont believe it was a flexible coupling that was used. This might have made the system too rigid. Could this have lead to the fatigue? Is it still a vibration issue then?
I don't have the means to vary the...
Greg Locock and Ron
The shaft failed somwehere near the bearing on the right side. I have done some torsional analysis and it was not the cause of failure. The cause was due to faitgue or fast fracture. I need to understand what induced this fatigue, and whether the vibrational stress was the...
Hi. I saw a similar thread with the same question. My situation is slightly different and would appreciate some advice. I have attached a schematic of the setup in question. The shaft in the middle has failed constantly and the schematic shows a modification that was done to reduce the stress on...
Bestwrench
Yes that was a typo I meant 4140. You are right the higer the carbon content the more brittle your material gets and more chance to nucleate cracks. Your suggestion about a tempered martensitic structure is great since it blalances out the compromised strength from choosing a lower...
Yes checking the frequencies of the shaft and the motor is a good idea. So the drive frequency and the natural shaft frequency must be similar in order to prevent fatigue? I am not familiar with how to do this comparision.
The material that I am moving is recyclable materials such as...
gwolf2
Thanks for the suggestions. I do believe that it is a cyclic bending problem. We are currently using a higher carbon steel 1440. It seems to be working along with the modification to the setup. However if fatigue from cyclic loading is the problem then I would need a better solution. Any...
Hmm yes the groove is a likely initiaiton site for the crack. Any ideas on how to prevent the fatigue from recurring? What exactly is cyclic loading? Do you think that the rubber components are exerted such a weight on the shaft that along with the torsion could cause it to fail?
Thanks
I have attached a pic of a similar shaft failure. However there is a groove running through the top of the shaft that extends through the length of the shaft.
I looked up the yield strength from a few websites that had that figure listed. I just needed an approximate value don't know why I used...
Hi. I am a materials engineer and currently have a project that I require some help with. It is a fairly straightforward setup that I am dealing with. I have posted the setup as an attachment. The drawing was done after a modification to the system was made. The modification was moving the gear...
