2 Replies Latest reply on May 24, 2007 12:42 PM by Designer Designer

    Jacobian Check ???

    Designer Designer

      Any body can explain to me what is Jacobian Check ?
      What is the effect to mesh....?

      I have tried analyse a part with different seeting for jacobian check, but the result is not different...


        • Jacobian Check ???
          dear friend,
          Parabolic elements can map curved geometry much more accurately than linear
          elements of the same size. The mid-side nodes of the boundary edges of an
          element are placed on the actual geometry of the model. In extremely sharp or
          curved boundaries, placing the mid-side nodes on the actual geometry can result
          in generating distorted elements with edges crossing over each other. The
          Jacobian of an extremely distorted element becomes negative. An element with
          negative Jacobian causes the analysis program to stop.
          In the course of calculating the element stiffness matrix, the program performs
          integration processes over the domain of the element. The integration process is
          simplified by evaluating the function of interest at prescribed locations inside the
          element. These locations are called Gaussian points. For the purpose of checking
          the quality of parabolic elements, COSMOS/Works gives you a choice to base the
          Jacobian check on 4, 16, or 29 Gaussian points.
          The Jacobian ratio of a parabolic tetrahedral element, with all mid-side nodes
          located exactly at the middle of the straight edges is 1.0. The Jacobian ratio
          increases as the curvatures of the edges increase. The Jacobian ratio at a point
          inside the element provides a measure of the degree of distortion of the element at
          that location. COSMOS/Works calculates the Jacobian ratio at the selected
          number of Gaussian points for each tetrahedral element. Based on stochastic
          studies, it is generally seen that a Jacobian ratio of 40 or less is acceptable.
          COSMOS/Works adjusts the locations of the mid-side nodes of distorted elements
          automatically to make sure they pass the Jacobian check.
          • Jacobian Check ???
            Designer Designer
            Thank`s for your great explanation....