I'm confused about the orientation of the stress element. It seems like it's different in different videos in the series. The element shows 0 MPa in the x direction, but in the diagram, there is 300 N shear force in the x direction. The 0 N is in the y-direction in the diagram. It seems to me that the stress element should have σy=0 MPa, σx=0.444 MPa compression (arrows in), and τxy=0.0533 MPa (arrows as they are currently). Either that, or the τ arrows should be flipped. Am I missing something?
@@piotrmisiaszek5236 Even though the stress element is always shown with σy on top and σx to the right, the key thing to remember is that they are σ stresses NO MATTER WHAT. So only normal (P/A) and Bending (Mc/I) stresses will contribute to the x or y σ stress. In this case, only bending stresses are present at point A. So that 300N SHEAR force won't have any effect on the x or y σ stress. Normal & Bending forces = σ stresses Shear forces = τ stresses
If you think about it slowly and pictorially, he calculated the MC/I stress. Which is compression, Now the compression will actually be along the the height of the beam, which is the y direction. It may not be correct though, but that's how I understand it.
I believe this is just because we assume x is in the direction of the 300N force in this case and y is normal to that direction. ultimately what you deem x and y just depends on the coordinate system you choose at the outset of the problem :)
If you look at the cross section we are analyzing and consider the neutral axis and think about where the compression forces are coming from, it's from above the stress element, in this case we used a standard x-y (Right-Up) coordinate axis, and therefore the stress due to the beam bending corresponds to sigma_y.
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he's great. I'm taking my final early so I'm having to learn this stuff online. Dr. Hanson always gives me a good laugh while learning
That's definetely cool Dr. Hanson!!!
(22:07)
This is what I want to see…Great job Dr Hanson
Wonderful solids lessons!! really taking the time to explain the problems along with a good sense of humor :))
Hey Jeff, I love you!
Thank you. I study mechanical engineering and you helped me a lot
I'm confused about the orientation of the stress element. It seems like it's different in different videos in the series. The element shows 0 MPa in the x direction, but in the diagram, there is 300 N shear force in the x direction. The 0 N is in the y-direction in the diagram. It seems to me that the stress element should have σy=0 MPa, σx=0.444 MPa compression (arrows in), and τxy=0.0533 MPa (arrows as they are currently). Either that, or the τ arrows should be flipped. Am I missing something?
I've got same feelings, anybody can explain?
@@piotrmisiaszek5236 Even though the stress element is always shown with σy on top and σx to the right, the key thing to remember is that they are σ stresses NO MATTER WHAT. So only normal (P/A) and Bending (Mc/I) stresses will contribute to the x or y σ stress. In this case, only bending stresses are present at point A. So that 300N SHEAR force won't have any effect on the x or y σ stress.
Normal & Bending forces = σ stresses
Shear forces = τ stresses
@@maryckbuilds but how would you know whether the Mc/I we calculate is x or y σ stress? is it always y σ stress?
If you think about it slowly and pictorially, he calculated the MC/I stress. Which is compression, Now the compression will actually be along the the height of the beam, which is the y direction. It may not be correct though, but that's how I understand it.
Maybe t is 150? Cause it is the thickness in the direction of V?
How do we know that the σ we calculated is σy and not σx?
I believe this is just because we assume x is in the direction of the 300N force in this case and y is normal to that direction. ultimately what you deem x and y just depends on the coordinate system you choose at the outset of the problem :)
If you look at the cross section we are analyzing and consider the neutral axis and think about where the compression forces are coming from, it's from above the stress element, in this case we used a standard x-y (Right-Up) coordinate axis, and therefore the stress due to the beam bending corresponds to sigma_y.
Oh my god! These videos are great!
Thanks