Force and momentum diagram for an isosceles trapezoid
Force and momentum diagram for an isosceles trapezoid
(OP)
Hello
I am trying to figure out the effect of stacking molds of hot liquid material on top of other molds.
I know there needs to be a moment analysis but my statics knowledge has been lost.
We are seeing cracks develop in the center of the molds and I'm looking to see what is the actual resulting force within this area.
I've included a drawing that should have all the data necessary for this problem.
Thank you
I am trying to figure out the effect of stacking molds of hot liquid material on top of other molds.
I know there needs to be a moment analysis but my statics knowledge has been lost.
We are seeing cracks develop in the center of the molds and I'm looking to see what is the actual resulting force within this area.
I've included a drawing that should have all the data necessary for this problem.
Thank you






RE: Force and momentum diagram for an isosceles trapezoid
RE: Force and momentum diagram for an isosceles trapezoid
The thickness of the mold is three inches, everywhere. I don't see how the material is relevant, I'm just looking for the internal stress at the middle of the top lip section. This will be the same for any material. Also, disregard the temperature, assume it is room temperature. Initial casting stresses are negligible. I've included another picture showing the stacking pattern. The bottom row of molds in fully supported on the bottom with another row of molds on top (rectangles molds used for simplicity). The top row of molds is supported by the two different bottom molds, one for each side. Bad explanation, see picture.
Thanks
RE: Force and momentum diagram for an isosceles trapezoid
Will elaborate more, hope soon.
RE: Force and momentum diagram for an isosceles trapezoid
I think a conservative model, not knowing more, is with loads of 1.5 ton (have taken 1.5 tonne) at corners of the bottom of the topping molds.
Unconservatively, the weight of the mold itself and the pressure of the molten material is for now omitted in all these quoted models that follow.
On this asummption and P-Delta included, we get a maximum VonMises stress result of 2.6 MPa in the lesser dimensions' model and of 11 MPa in the second bigger. Flexural behaviour of course is involved. This is with the actual loads without any safety factor. The maximum stresses occur under the applied loads of 1.5 ton.
At the center of the faces, atop, the VonMises stresses stand in the range of somewhat over 1.1 MPa in these models with 1.6 ton point loads.
Have, also, modeled the loads applied uniformly to each side, 3 tons in the loaded length. Then the maximum stresses occur at the center of the side faces, atop, at values of around 1.8 MPa in the lesser model and 3.75 MPa in the bigger.
Modeling the same thing with brick or tetrahedral elements may lead to somewhat lesser stresses.
Other load conditions may be causing the cracks. How the molds are being hung and then at what impact factor laid, and the quality of the wanted uniform support at the rim have a say in the results. As well including the omitted factors. The temperature effects in the production cycle will impact stresses and maybe standing strengths.
More detailed studies of the cracks, loadings, temperature effects would help to a more accurate adjudication of the cause of the failures.