In ansys Solid185 when fully integrated induces locking. The deflection values are smaller than analytical deflection values. When i used solid45 to model the same structure it gives results close to analytical solution. This is bcoz solid45 has extra shape functions besides the sf for 8 noded brick element
In the above displacement field shown u1, u2 and u3 doesnot corresspond to any node. Introduction of extra dofs make the elemnt flexible to overcome locking. But how these extra shape functions considerably increase accuracy?