Given what you are describing in selecting "Selected Direction" you have both a blue selection box in your force definition to define the face the force is applied onto as well as a smaller pink box to select a reference (edge, axis, face, plane, etc) to define the direction in which the force applies. Edge or axis are the easy pink reference selections to use to complete the force definition so just select an edge/axis in the pink selector box and try accepting the definition again.
Thanks for your reply's, still not quite sure.... i have attached a picture below. I'm not sure how to select a face on the pin and dont understand your reply RyanDark ( sorry ) This is the first time ive used this feature of solidworks and haven't been using the program for very long either.
I need to apply a rearward force on the assembly through the pin (Picture is looking at the front).
Thanks in advance. Sam.
Please explain what you want to perform FEA on this model? such as where you want the fixed feat and where the force is applied?
Sam, you have to have the pin face selected in both the blue box and the pink direction box then you need to click on one of the force directions either radial, axial or circumferential. In this case, using the pin as the direction for the force is not what you are looking for since there is no option for a shearing force normal to the pin axis. Instead use a plane that is normal to the direction of the force to define the force direction.
Another word of advice, depending on what part of the assembly is important in the analysis you will want to consider applying this as a bearing load which then has a more accurate bearing distribution of the load on the pin.
The stresses on this pin to check are shear and bearing.
There are two shear planes, so the shear stress is
Tau = F/2A = F/(2*pi*D^2/4).
There are two bearing planes, so the bearing stress is
Sigma = F/2A = F/(2*D*L), where L is the length of engagement, up to a max of about 1D.
The allowable shear stress is the allowable yield stress multiplied by 0.6.
The allowable bearing stress is the allowable yield stress multiplied by 1.5.
Unless you have an advanced understanding of FEA, nothing you do in SW is likely to produce a more accurate result than this hand calc.
Then, remove the pin from the model and apply the force to the bearing surfaces of the other piece.