Description
Calculate a supplied two-point force-displacement secant stiffness.
Bench measurements require explicit signal units, calibration signs, geometry and reference conditions. Engineering strain differs from final-length ratio, secant stiffness differs from a material modulus, and nominal contact area differs from actual conductive contact. A supplied coefficient or certificate reference does not establish device validity.
Calculate a supplied two-point force-displacement secant stiffness.
When to use this tool
Use Prosthetic Bench Load Displacement Pair when you already have beforeForceNewtons, afterForceNewtons, beforeDisplacementMillimeters, afterDisplacementMillimeters and need to calculate a supplied two-point force-displacement secant stiffness.
How to use the tool and how it works
- Enter beforeForceNewtons, afterForceNewtons, beforeDisplacementMillimeters, afterDisplacementMillimeters. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read forceChangeNewtons, displacementChangeMillimeters, secantStiffnessNewtonsPerMillimeter. Use the output convention below.
Require different displacement endpoints; return after-before changes and force change/displacement change in N/mm.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| beforeForceNewtons | Before Force Newtons | Required. Finite number. |
| afterForceNewtons | After Force Newtons | Required. Finite number. |
| beforeDisplacementMillimeters | Before Displacement Millimeters | Required. Finite number. |
| afterDisplacementMillimeters | After Displacement Millimeters | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| forceChangeNewtons | Force Change Newtons | Required. Finite number. |
| displacementChangeMillimeters | Displacement Change Millimeters | Required. Finite number. |
| secantStiffnessNewtonsPerMillimeter | Force change divided by displacement change, N/mm; endpoint order and negative values are retained. | Required. Finite number. |
{
"input": {
"beforeForceNewtons": 10,
"afterForceNewtons": 110,
"beforeDisplacementMillimeters": 1,
"afterDisplacementMillimeters": 3
},
"output": {
"forceChangeNewtons": 100,
"displacementChangeMillimeters": 2,
"secantStiffnessNewtonsPerMillimeter": 50
}
}Limitations and assumptions
- Endpoint order may reverse and negative stiffness is retained. This is a secant between supplied points, not a tangent modulus, elastic material property or safety assessment.
- 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
Use verified instrument records, calibration data and a complete device/material model. Evaluate uncertainty, operating conditions and appropriate professional requirements before interpreting local ratios or labels as performance, fitness or safety.
References
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