BIZOMAT MAKEOS · Materials
Tensile Test Evaluation (Yield, UTS, Elongation, Reduction of Area, True Fracture)
From my tensile test readings, what are the yield and tensile strengths, elongation, reduction of area, modulus and true fracture stress, and does the material meet its specification?
Evaluation of a round tensile specimen: original area, yield strength from the 0.2% offset load, tensile strength from the maximum load (as the nominal stress of the true stress–strain tool), elastic modulus from a load and extension in the elastic range, elongation after fracture, reduction of area from the fracture diameter, true fracture stress and strain, the yield-to-tensile ratio, and checks against the specification minimums.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Original diameter | mm | Diameter of the reduced section before the test. |
| Original gauge length | mm | Gauge length marked before the test. |
| Load at 0.2% offset yield | kN | Load at the 0.2% offset yield point (or the upper yield point for steels with a sharp yield). |
| Maximum load | kN | Highest load reached. |
| Load at fracture | kN | Load when the specimen broke. |
| Gauge length after fracture | mm | Gauge length measured after fitting the broken halves together. |
| Diameter at fracture | mm | Smallest diameter at the fracture. |
| A load in the elastic range | kN | A load well inside the straight elastic part of the curve. |
| Extension at that load | mm | Extensometer extension over the gauge length at that load. |
| Specification minimums | ||
| Least yield strength | MPa | Least yield strength in the specification. |
| Least tensile strength | MPa | Least tensile strength in the specification. |
| Least elongation | % | Least elongation in the specification. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Original diameter
- What it is
- The diameter of the reduced (gauge) section of the round specimen, measured before testing.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 200 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- All the strength results vary with 1 ÷ d₀², so measure it carefully.
What this means: Original gauge length
- What it is
- The gauge length marked on the specimen before testing, used for elongation and the modulus.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Load at 0.2% offset yield
- What it is
- The load at which the material yields: at the 0.2 % offset point, or at the upper yield point for a sharp yield.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 23 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter it in kN, not N: divide a test-machine reading given in newtons by 1000.
What this means: Maximum load
- What it is
- The highest load the specimen carried during the test, which gives the tensile strength.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 33 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Load at fracture
- What it is
- The load on the specimen at the moment it broke, used with the fracture area for the true fracture stress.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 26 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Gauge length after fracture
- What it is
- The gauge length measured after carefully fitting the broken halves back together.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 4000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 61 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Diameter at fracture
- What it is
- The smallest diameter at the fracture neck, measured on the broken pieces.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 200 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: A load in the elastic range
- What it is
- A load picked from the straight elastic part of the load–extension curve, used with its extension to estimate the modulus.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Extension at that load
- What it is
- The extension over the gauge length at that elastic load, read from the extensometer.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.032 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use extensometer data; crosshead movement includes machine stretch and understates the modulus.
Specification minimums
What this means: Least yield strength
- What it is
- The minimum yield strength required by the material specification.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0 MPa to 5000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Least tensile strength
- What it is
- The minimum tensile strength required by the material specification.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0 MPa to 5000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Least elongation
- What it is
- The minimum elongation after fracture that the material specification requires, for the same gauge length.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Method and formulas
- A₀ = π d₀² ÷ 4; yield = F_y ÷ A₀; tensile strength = F_max ÷ A₀ (as the true stress–strain tool’s nominal stress).
- Elongation = (L_f − L₀) ÷ L₀; reduction of area = (A₀ − A_f) ÷ A₀ (A_f from the fracture diameter).
- Modulus E = (F_e ÷ A₀) ÷ (ΔL_e ÷ L₀).
- True fracture stress = F_f ÷ A_f; true fracture strain = ln(A₀ ÷ A_f).
- Example: yield 292.85 MPa, tensile 420.17 MPa, elongation 22%, reduction of area 57.75%, modulus 198.94 GPa.
Limitations
- Round specimens; flat specimens use width and thickness for the area.
- Modulus from a single point is approximate; use the slope of the elastic line.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Work up a tensile test report
- Check a mill certificate or test result against a specification
- Estimate modulus from extensometer readings
Who it is for
- Materials engineers
- Test laboratory technicians
- Quality engineers
What you get
- Yield and tensile strength, yield ratio
- Elongation, reduction of area and modulus
- True fracture stress and strain
Interpreting the result
- A high yield-to-tensile ratio leaves little warning before failure; ductile structural steels are usually below about 0.85.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1331–1334. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Reading a tensile test
In Yield and Plastic Flow by the Numbers
What it covers: What a tensile test measures and how to evaluate one: yield by offset or yield point, tensile strength, elongation, reduction of area, modulus and true fracture values, and when a result is invalid.
Useful alongside · BIZOMAT original book
Inclusions and the largest one
In Microstructures by the Numbers
What it covers: Rating non-metallic inclusions on the right section, why their amount matters less than their largest size, estimating the largest inclusion by extreme values, and inclusions in tensile tests.
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