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  • (1) Stress Concentration or Singularity

    For linear elastic analysis, there is no converged stress at the areas with stress concentration. The maximum stress is infinite just as the theory predicts. Thus, if there is stress concentration, the maximum stress in a linear elastic analysis is not a useful criterion to validate the structure.

    (2) A Beam Example of Stress Concentration

  • orginos

    Rocco Schiavilla
    Theory Center Senior Staff, Jefferson Lab
    Professor of Physics, Old Dominion University

  • J. Wallace Van Orden
    Theory Center Senior Staff, Jefferson Lab
    Professor of Physics, Old Dominion University

  • (1) Use Three or More Layers of Reduced 8-node Elements in the Thickness Direction

    For example, if three layers of reduced elements are used, the computed tip deflection is 4.828 mm; if four layers, 4.581 mm. The computed deflection is reasonable, but they are still larger than the theoretical value (4.281 mm).

    (2) Use Two or More Layers of Reduced 20-node Elements or One or More Layer of Fully Integrated 20-node Elements in the Thickness Direction

  •  (1) Hourglassing Phenomenon

    The reduced integration of linear 8-node solid elements leads to numerical difficulty called hourglassing because the reduced 8-node solid elements tend to be excessively flexible. For example, if two layers of reduced 8-node elements in the thickness direction are used, the computed tip deflection of the beam example in Shear Locking is 5.713 mm, which is much larger than 4.281 mm.

    (2) Hourglassing Explained

  • (1) Use Reduced 8-node Elements with at least Three Layers of Elements in the Thickness Direction

    Deflection = 4.58 mm 

    (2) Use Reduced 20-node Elements with at least Two layers of Elements along the Thickness Direction

    Deflection = 4.305 mm

    (3) Use Fully Integrated 20-node Elements

    Deflection = 4.292 mm

  • Jefferson Lab ships its final accelerator section for a project to upgrade the world’s brightest X-ray laser 

    NEWPORT NEWS, VA – Today, the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility has shipped the final new section of accelerator that it has built for an upgrade of the Linac Coherent Light Source (LCLS). The section of accelerator, called a cryomodule, has begun a cross-country road trip to DOE’s SLAC National Accelerator Laboratory, where it will be installed in LCLS-II, the world’s brightest X-ray laser.

  • “You can’t really describe what it feels like to save someone’s life. You have to depend on others to keep everyone safe, especially when you are in an unstable environment.”

    Brian Hanlon – Security and Services Manager at Jefferson Lab

    U.S. Coast Guard – 1989-1996

    As Brian Hanlon’s teenage eyes skimmed the surf, he took in the large U.S. Coast Guard cutters just off of the shore. Growing up just a block shy from the Florida coast, he heard the stories of the search and rescue missions and was drawn to them.