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Durability engineering videos

Durability engineering videos

Introduction to nCode GlyphWorks for Durability Analysis

In this webinar, we will explore how we can use nCode GlyphWorks to visualize and analyze fatigue performance for product design improvements from measured strain data. We will identify the factors that may lead to durability concerns and fatigue damage. We will also explore ways to identify under-designed and over-designed areas using a back calculation approach and how to meet a target life.

In the presentation we will look at:

  • How to review measured strain data
  • Introduction to strain-life fatigue analysis
  • How to achieve a target fatigue life
  • Fatigue analysis for a combination of events in a durability schedule

Originally presented on March 2, 2021

Notes from the presenter

Some key takeaways and additional information from this webinar:

  • Tools for fatigue calculation in nCode Glyphworks

    Both Strain-Life (EN) and Stress-Life (SN) methods can be used to calculate fatigue life in nCode Glyphworks.

    The StrainLife glyph is typically used when the inputs to the fatigue calculation are in measured strain, usually from a strain gauge or strains extracted out from a strain rosette.

    In this case the strains are potentially already elastic-plastic, but the glyph can also be used for fully elastic strains, for example, a linear finite element (FE) analysis. The loading input strains can be in the form of a time history, a list of cycles, or a rainflow histogram. Additional properties control corrections for geometry, surface effects, mean stress, and other factors affecting fatigue life.

    The StressLife glyph is typically used for component tests in the medium to high cycle regimes and, unlike the Strain-Life method, does not correct for plasticity. Strain gage data with units of strain, not stress, are valid inputs, as stresses can be calculated from strains via material properties.

  • Does nCode comes with a materials database? And is it possible to use one’s own material curve for fatigue calculation?

    Yes, every nCode installation comes with a standard materials database with over 450 in-house validated material fatigue curves for many commonly used materials. A Premium Materials Database containing over 130 fatigue curves for steels and aluminium alloys, plus some other non- ferrous materials is also available for add-on.

    Materials manager allows users to import custom material curves in nCode. It also enables material data to be edited and plotted to enhance usability.

  • Target fatigue life and Back calculation

    Strain Life glyph's back calculation capabilities allows users to assess how the stress should be increased or decreased to meet the target life. This is called a back calculation because we know the target fatigue life and want to calculate what would normally be an input parameter—the stress level. This type of back calculation provides quantifiable stress or strain reduction targets for a redesign or countermeasures. The scale factor values would typically appear in three groups, i.e, scale factor = 1, < 1 and > 1.

    The target life is specified in equivalent units, which are set as part of the loading information. This normally defaults to “Repeats”; i.e., repeats of the input loading history and is used to specify the life result.

    For example, if both life achieved and target life are the same then scale factor value would be equal to 1.

    • Life achieved = 20000 repeats
    • Target life = 20000 repeats
    • Scale factor =1

    If Life achieved is 15000 repeats and target life is 20000 repeats then scale factor value would be less than 1, specifying stress reduction required to meet the target life.

    Similarly, if life achieved is 30000 repeats and target life is 20000 repeats then scale factor value would be greater than 1 indicating an over-designed scenario.




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