What is Hourglass and how to solve it

Hourglass and How to Solve It

As it is discussed in previous articles, using reduced integration method is an effective solution to avoid shear locking of full integration elements which are subjected to bending moment. But using reduced integration elements has also its own drawbacks. First disadvantage of these elements is that the stiffness of first order reduced elements is very low, consequently in some cases they might exhibit an excessive deformation which is called to ‘Hourglass’.

In other words, The hourglass effect is when some elements deform dramatically in their middle part. As a result ABAQUS experiences a hard time re-evaluating the stiffness matrix of these elements and stop the analysis with a numerical error like figure-1

To solve Hourglass error, it is recommended to activate the stiffness control option in … window, or  change the type of element to reduce its deformation. Using a finer mesh can be another solution, since it provides a more realistic view for the Abaqus solver.