Description
Calculate a two-point load/displacement secant slope.
Orthopedic measurements distinguish side, reference origin, image scale, device lots and mechanical test geometry. A two-point load/displacement slope is structural stiffness rather than a material modulus. Supplied matches, offsets and calibration factors need verified anatomy, devices and test conditions before clinical or design interpretation.
Calculate a two-point load/displacement secant slope.
When to use this tool
Use Bone Test Load Displacement Slope when you already have firstLoadNewtons, secondLoadNewtons, firstDisplacementMillimeters, secondDisplacementMillimeters and need to calculate a two-point load/displacement secant slope.
How to use the tool and how it works
- Enter firstLoadNewtons, secondLoadNewtons, firstDisplacementMillimeters, secondDisplacementMillimeters. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read secantNewtonsPerMillimeter. Use the output convention below.
Require distinct supplied displacements in mm; return (secondLoad-firstLoad)/(secondDisplacement-firstDisplacement) in N/mm.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstLoadNewtons | First Load Newtons | Required. Finite number. |
| secondLoadNewtons | Second Load Newtons | Required. Finite number. |
| firstDisplacementMillimeters | First Displacement Millimeters | Required. Finite number. |
| secondDisplacementMillimeters | Second Displacement Millimeters | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| secantNewtonsPerMillimeter | Two-point structural slope in N/mm, not Young’s modulus. | Required. Finite number. |
{
"input": {
"firstLoadNewtons": 100,
"secondLoadNewtons": 300,
"firstDisplacementMillimeters": 1,
"secondDisplacementMillimeters": 3
},
"output": {
"secantNewtonsPerMillimeter": 100
}
}Limitations and assumptions
- Signed slopes are allowed; this is structural secant stiffness, not a material modulus, failure strength or safe load.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Inspect actual device specifications, calibrated images and the full measurement or test setup. Use complete geometry and material/test information when relating a local scale, side match or structural secant slope to a physical or clinical question.
References
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