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JIP Accomplishments

Advancing the state of the art in fatigue analysis.

The Joint Industry Program (JIP) has inspired, enabled and implemented a number of key innovations since it was launched at the turn of the millennium. Here are some of its most significant achievements.

The Joint Industry Program (JIP) has inspired, enabled and implemented a number of key innovations since it was launched at the turn of the millennium. Here are some of its most significant achievements.

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JIP I: 2001 - 2003

Rapid progress was made in validating the effectiveness of the structural stress method by effectively correlating large amount of fatigue (S-N) data from drastically different joint types, loading modes, and plate thicknesses. Major accomplishments for the period includesL

  • Demonstrating the robustness of the FE nodal-force-based structural stress procedure for all joint types in applications including aerospace, civil structures, ground vehicles, offshore/marine, petrochemical, and nuclear utilities
  • Automating the structural stress calculation procedures in the form of post-processors for ABAQUS, ANSYS, NASTRAN and I-DEAS for day-to-day fatigue design and evaluations
  • Formulating a structural-stress-based master S-N curve approach by consolidating well-documented historical fatigue data from various industries without using any empirical parameters
  • Establishing a comprehensive weld S-N database containing about 5,000 fatigue tests from literature from the 1950’s to the present

JIP II: 2004 - 2009

In its “sophomore” era, the Joint Industry Program made significant progress in a number of critical areas. Participants:

  • Developed simplified structural stress procedures for weld root/throat failure
  • Investigated various fatigue data under different conditions and constructed master S-N curves for:
    • Weld root/throat fatigue failure
    • Improved welds in applications involving hammer peening, toe grinding, and TIG dressing techniques
    • Corrosion weld fatigue under sea water conditions (free corrosion, Cathodic protection)
  • Developed and validated a modified end-correction procedure at geometric discontinuity in the weld line, such as at a weld end or at a 90 corner
  • Using this procedure, rendered the structural stress at geometric discontinuities substantially insensitive regardless of mesh shape and size at the weld end
  • Developed coarse-model screening procedures for rapidly evaluating the structural stress in large structural models by identifying and including only the essential features of the weld in the FE model
  • Completed validation for plate-to-plate joints, with other joint types under development
  • Investigated fatigue analysis of tubular joints, focusing on comparisons between the conventional hot-spot stress method and BSS method and on their implications for remaining-life assessment
  • Proposed method to unify the multi-axial fatigue data for both normal-dominant and shear-stress dominant
  • Developed Path-Dependent Maximum Range (PDMR), a multi-axial cycle-counting and fatigue-life assessment methodology for welded structures subjected to multiple, non-proportional, time-varying loads
  • Investigated a critical plane approach for use with PDMR for non-welded structures
  • Successfully implemented an advanced “convex hull” algorithm into PDMR-2D to significantly accelerate analysis time, thus enabling fatigue analyses of large structures with multiple, uncorrelated load inputs
  • Proposed equivalency-based statistical analysis of linear or linearized stress-life and strain-life fatigue data, a new statistical data analysis procedure
  • Updated JIP postprocessor periodically with the latest developments and interfaces relevant to commercial versions of FE programs

JIP III: 2010 - 2013

As the Joint Industry Program continued to mature, our progress continued in areas that our members consider critical. For example, we:

  • Developed a fatigue-evaluation procedure for in-plane shear dominant cyclic loading
  • Investigated a weld-fatigue analysis of aluminum alloy joints
  • Developed a fatigue-evaluation procedure for friction stir welds
  • Investigated fatigue initiation and propagation life for welded joints
  • Developed a fatigue-evaluation procedure for welded rod-to-rod and rod-to-tube joints
  • Investigated temperature’s effects on weld fatigue
  • Investigated weld-fatigue behavior beyond 10-million cycles
  • Developed a weld-fatigue evaluation procedure for Titanium welds
  • Developed a JIP III Weld Fatigue Database
  • Continued updating the JIP postprocessor with the latest developments
  • Investigated weld-fatigue behavior in a sour service environment
  • Bureau Veritas (BV) developed guidelines for applying the BSS method to ship and offshore structures

JIP IV: On the Horizon

During the final JIP III meeting, a number of action items were proposed. JIP IV. Potential objectives include:

  • Pursuing acceptance of the BSS approach and JIP procedures by additional code-classification organizations
  • Developing weld-fatigue evaluation procedures incorporating welding-induced residual stress effects
  • Finalizing weld-fatigue evaluation procedures for in-plane shear-dominant cyclic loading
  • Finalizing the weld-fatigue evaluation procedure for aluminum alloy welds (fusion welds and friction stir welds)
  • Finalizing weld-fatigue evaluation for Titanium
  • Updating and improving the current JIP Weld Fatigue Database
  • Continuing the annual Structural Stress Method training courses