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Test a Mechanism (Qualification FEA)

After the topology optimization converges, deFlex can run additional structural analyses on the resulting mechanism. This lets you evaluate structural performance at specific loads and verify that the design operates within safe stress limits.

There are two kinds of post-optimization analysis:

  • Qualification FEA -- Runs automatically after optimization (unless disabled in Advanced settings). Characterizes the mechanism's full operating range by incrementally increasing displacement until yield.
  • Test Mechanism -- A manual analysis you submit at a specific force or displacement of your choosing.

Running a test​

The Test Mechanism form appears in the Properties sidebar after an optimization has completed and produced results.

Input mode​

A segmented control at the top lets you choose the input type:

  • Force -- Specify the applied force in the current force unit. The solver computes the resulting displacement.
  • Displacement -- Specify the input displacement in the current length unit. The solver computes the required force.

Switching between modes clears any yield warning.

Magnitude​

A numeric input field for the load value. The placeholder shows the safe operating range (e.g., "0 -- 150 N") based on the bounding limits from qualification FEA. If the limits are estimates (from the operating envelope rather than qualification FEA), the range is prefixed with a tilde ().

Nonlinear toggle​

A switch that enables nonlinear FEA for the test. Default is off. The nonlinear option is disabled (grayed out with a "pending" label) until the qualification FEA completes, because the nonlinear solver requires the qualification baseline.

When enabled, the test uses a geometrically nonlinear solver that accounts for large deformations, giving more accurate results for highly flexible mechanisms.

Yield warning​

If the entered magnitude exceeds the estimated yield limit from qualification FEA, a warning appears before the test is submitted. The warning shows the estimated yield limit value and explains that results may show plastic deformation. You have two options:

  • Continue -- Submit the test anyway, accepting that the mechanism may be loaded beyond its elastic range.
  • Reduce to max -- Automatically sets the magnitude to the yield limit value.

The warning only appears once per magnitude change. If you click Continue and then click Run Test again, it submits without re-showing the warning.

Submitting​

Click Run Test to submit. The button shows "Running..." while the server processes the request. After completion, the result appears in the Properties sidebar.

Understanding test results​

The Test Result panel displays the outcome of a completed test mechanism analysis. It opens automatically when you select a test result in the scene tree.

Shows the test name, a badge indicating Linear or Nonlinear analysis, and a description of the mesh type:

  • Manual tests (tests you submit) run on a "smooth mesh" (refined analysis mesh).
  • Auto tests (from qualification FEA) run on the "pixelated grid" (the optimization grid).

The mesh type is determined by whether the test was auto-generated, not by whether it is linear or nonlinear.

Factor of safety​

If available, a prominent color-coded card shows the factor of safety (yield stress divided by maximum Von Mises stress):

  • Green (>= 1.5) -- Safe. The mechanism operates well within elastic limits.
  • Orange (>= 1.0 but < 1.5) -- Marginal. Close to yield; consider reducing load or strengthening the design.
  • Red (< 1.0) -- Unsafe. The mechanism is predicted to yield at this load.

See Mechanism Metrics for more on how factor of safety is computed.

Performance​

A card showing key force and displacement results:

MetricDescription
Applied ForceThe input force in Newtons
Grip ForceThe reaction force at the workpiece (output) spring
Mechanical AdvantageRatio of grip force to applied force
Input DisplacementHow far the input moved
Output DisplacementHow far the output moved

Stress details​

A collapsible section with detailed stress metrics:

  • Max Von Mises -- Peak equivalent stress, the primary failure criterion
  • Max Principal -- Maximum principal stress (tension)
  • Min Principal -- Minimum principal stress (compression)
  • Max Shear -- Maximum shear stress
  • P50, P90, P99 -- Stress percentiles across all elements, useful for understanding stress distribution rather than just peak values

Strain details​

A collapsible section with strain results:

  • Max Von Mises Strain -- Peak equivalent strain
  • Max Principal Strain -- Maximum tensile strain
  • Min Principal Strain -- Maximum compressive strain
  • Strain Safety Factor -- Yield strain divided by maximum Von Mises strain

Fatigue (Goodman criterion)​

Appears only when fatigue data is available. A collapsible section showing:

  • Safety Factor -- Goodman fatigue safety factor
  • Assessment -- Either "Infinite life" (safe for unlimited cycles) or "Finite life" (will eventually fail under cyclic loading)
  • Stress Amplitude -- The alternating stress component
  • Mean Stress -- The mean stress component

Export​

A button at the bottom exports all test results to a CSV file. The filename is derived from the test name.

Qualification FEA results (Mechanism Metrics)​

The Mechanism Metrics panel shows results from the automatic qualification FEA that runs after optimization. It provides the operating envelope for your mechanism.

Status​

A badge at the top shows the qualification FEA status: Pending, Running, Complete, Failed, or Skipped. While running, a spinner is displayed.

Design limits​

When qualification FEA completes, the design limits card shows the safe operating envelope:

  • Max Input Displacement -- Maximum displacement at the input before yield
  • Max Output Displacement -- Maximum displacement at the output before yield
  • Max Input Force -- Maximum force at the input before yield
  • Max Output Force -- Maximum force at the output before yield

If values come from the operating envelope (estimated) rather than qualification FEA, they are marked with "(est.)".

Analysis status​

Shows the convergence status of the two qualification FEA phases:

  • Free Motion -- Mechanism moving freely (no workpiece contact)
  • Grip Block -- Mechanism gripping a rigid workpiece

Each shows a status icon (green check for converged/yield found, orange check for yield reached/extrapolated/low confidence, red X for failed/diverged) and a text label.

Additional details include:

  • Computation Time -- How long the qualification FEA took
  • Yield Percentile -- The stress percentile used for yield detection

Qualification FEA chart​

When step data is available, an inline SVG chart displays two subplots:

  1. Force vs. Displacement (top) -- Shows the force-displacement relationship for free motion and grip block phases as separate curves.
  2. Stress vs. Displacement (bottom) -- Shows effective stress vs. displacement for both phases, with a horizontal dashed line at the material yield stress.

A legend identifies the free motion curve, grip block curve, and yield stress line.

Collapsible sections​

  • Stress at Yield -- Max Von Mises, max/min principal stress, and max shear at the yield point.
  • Material Properties -- The applied material's name, Young's modulus, Poisson's ratio, yield stress, ultimate stress, and design thickness.

Export​

Two export buttons are available:

  • CSV -- Exports mechanism metrics and qualification FEA data to CSV.
  • STL -- Downloads the mesh as an STL file (only visible when a mesh URL is available).