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I create chain object and i apply rigid body simulation in it. After that, i try the chain and the chain fall likes real chain like in this picture 
but when i try it in different position, the chain break just like this 
I have tried using constraint, but the chain still will breaks, be it whole or some part of chain.
What is the problem? Here is my blend file https://pasteall.org/blend/4e5bebdcaedd46d8a20fb23d6c399993
In 3.0 it seems to work: Apply the scale + rotation of the links, set the origins to geometry, add some edge loops, and it will work fine. You can also tweak the Substeps Per Frame and Solver Iterations values in the Scene > Rigid Body World panel:
It seems buggy in 2.7 so what you can do is first apply the transforms, set the origin to geometry and edit the geometry, then use this answer by Gandalf: Select 2 adjacent links, go into the left panel > Physics > Rigid Body Tools > Constraints > click on Connect. It will create an empty between the 2 links. Select the empty and in the Properties panel > Physics > Rigid Body Constraint, choose Type > Point and uncheck the Disable Collisions option. Select the 2 next links and do the same until the bottom. In order to avoid shakings, go into the Properties panel > Scene > Rigid Body World, increase the Solver Iterations up to 10:
