I leave them out. For 3D problems, positive and negative signs tell you the direction of the internal forces and moments. For normal stresses you need to specify tension or compression. So the positives and negatives are important in that it will show you directions which will help you tell whether the normal stresses are compression or tension. For shear stresses, I like to specify the direction of the shear stresses. So, again, the positives and negatives are important in that it helps you tell which direction the shear stresses are acting.
@@jasonws1094 I would have to defer to your teacher. For normal stress, I DON'T want my students to include a negative: I want them to give me the magnitude and tell me tension or compression. For shear, I want them to give me the magnitude and tell me which direction it is pointing. There are some teachers who want a negative sign if the normal stress is in compression. And of course this is only for 3D stresses, for 2D stresses there is a sign convention that you should use.
BIG THANKS!
why did you just dont consider the negative signs when doing your calculations of stresses? is it ok to put them in or should we leave them out
I leave them out. For 3D problems, positive and negative signs tell you the direction of the internal forces and moments.
For normal stresses you need to specify tension or compression. So the positives and negatives are important in that it will show you directions which will help you tell whether the normal stresses are compression or tension.
For shear stresses, I like to specify the direction of the shear stresses. So, again, the positives and negatives are important in that it helps you tell which direction the shear stresses are acting.
@@engineeringdeciphered but is it okay if i include the - sign in my calculations
@@jasonws1094 I would have to defer to your teacher. For normal stress, I DON'T want my students to include a negative: I want them to give me the magnitude and tell me tension or compression. For shear, I want them to give me the magnitude and tell me which direction it is pointing. There are some teachers who want a negative sign if the normal stress is in compression. And of course this is only for 3D stresses, for 2D stresses there is a sign convention that you should use.
So would you say there’s no normal force only shear force?
Shouldn't the shear stress caused by torque be in the opposite direction? i.e. positive-z direction
Remember we are calculating the internal shear that counteracts those external torques that you mentioned. It has to add up to zero.
yes sir
yes
or no