In this case, wouldn't the solid expand in all directions? Wouldn't x and y decrease?
If every distance in the solid expands, why would you expect a contraction of the material along the inner edge?
(No, x and y do not decrease)
Why is it that the solid only increases outward, though? Why does it no expand inwards as well? This would mean x and y (as shown in the picture) are decreasing. I just can't seem to understand why the object would grow in one direction for each component (horizontal and vertical) when looking at this image.
It is growing in all directions - every distance between points increases, as the whole material stretches.
As long as there is no fixed outer border which stops expansion in that direction, a uniform expansion of everything is the best way to avoid internal stress.
It is not a liquid...
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