Source: https://guthlabs.ai/docs/instruments/thermal-expansion-calculator/
instrument / verified-clean
# Thermal Expansion Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab
**Tranche**: tranche-7
**Evidence ID**: t7-011
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The linear-length calculation is standard when its assumptions are made explicit, but the specification is not honest as written because it advertises area expansion without an area input or formula. Either relabel the instrument as a linear thermal-expansion calculator or add a documented isotropic area-expansion mode, including whether the displayed result is the small-strain approximation or the exact constant-α geometric result.
### Formula and scope findings
- ΔL=αL0ΔT is the standard linear-expansion formula only for isotropic material, constant α over the temperature interval, and sufficiently small strain; these assumptions are not stated.
- The instrument claims area expansion but provides no area input or area formula. For isotropic material, the usual small-strain approximation is ΔA≈2αA0ΔT; the exact constant-α geometric result is A1=A0(1+αΔT)^2.
- The stated formula defines ΔL but not the advertised new length; the implementation must explicitly calculate L1=L0+ΔL.
- CTE is temperature-dependent for many materials, so a single tabulated α is only valid over a stated temperature range or as an engineering approximation.
### Unit assumptions
- α is supplied in 1/K or 1/°C; temperature differences in kelvins and degrees Celsius have equal numerical magnitude.
- L0 and new length use the same length unit; ΔL has that same unit.
- For area calculations, A0 and ΔA use the same squared-length unit.
- The tabulated CTE values below are representative room-temperature engineering values and are treated as constant over each stated interval.
- The area result labeled linearized uses ΔA=2αA0ΔT; the exact constant-α result uses A1=A0(1+αΔT)^2.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
The calculator needs explicit range handling because an extreme but syntactically valid input overflows to infinity. It also has a unit-convention hazard when ΔT is supplied in °F while α is per °C.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"material": "copper",
"alpha_per_K": 0.0000165,
"L0_m": 2,
"T0_C": 20,
"T1_C": 120,
"delta_T_C": 100
},
"expected_outputs": {
"delta_L_m": 0.0033,
"new_length_m": 2.0033
},
"reference_data": {
"material": "copper",
"alpha_per_K": 0.0000165,
"table_fragment": "Copper linear CTE near room temperature = 16.5 × 10^-6 K^-1",
"source_convention": "widely tabulated standard value"
},
"working": "ΔT=T1−T0=120−20=100 °C. ΔL=αL0ΔT=(16.5×10^-6 K^-1)(2.0 m)(100 K)=0.0033 m. New length=L0+ΔL=2.0+0.0033=2.0033 m."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche7/tranche7-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`