True strain
Materials Science · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- Atomic Melting Melting Specific Heat (W/(m˙K))
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
A materials engineer computes the true strain of a tensile specimen at necking. Given original length (L0) = 1.3500 in; final length (Lf) = 2.9000 in, determine the true strain (epsT).
Given
Find
true strain (epsT)
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except epsT is given, so isolate epsT symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 1 — schematic for True strain — solve for true strain — True strain
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsT:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsT = 0.7646 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.5292 — kept a factor of two that cancels in the correct rearrangement.
- 0.3823 — dropped that same factor in the other direction.
- 0.8411 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
A student compares true strain to engineering strain for a stretched rod. Given original length (L0) = 2.2000 in; true strain (epsT) = 1.1610, determine the final length (Lf) in in.
Given
Find
final length (Lf), in in
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except Lf is given, so isolate Lf symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 2 — schematic for True strain — solve for final length — True strain (2)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Lf:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Lf = 7.0249 in to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 14.0497 — kept a factor of two that cancels in the correct rearrangement.
- 3.5124 — dropped that same factor in the other direction.
- 7.7274 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
The true strain of a drawn wire is calculated from its length change. Given final length (Lf) = 6.0500 in; true strain (epsT) = 0.7750, determine the original length (L0) in in.
Given
Find
original length (L0), in in
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except L0 is given, so isolate L0 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 3 — schematic for True strain — solve for original length — True strain (3)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for L0:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning L0 = 2.7873 in to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 5.5745 — kept a factor of two that cancels in the correct rearrangement.
- 1.3936 — dropped that same factor in the other direction.
- 3.0660 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
A materials engineer computes the true strain of a tensile specimen at necking. Given original length (L0) = 4.2500 in; final length (Lf) = 6.4000 in, determine the true strain (epsT).
Given
Find
true strain (epsT)
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except epsT is given, so isolate epsT symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 4 — schematic for True strain — solve for true strain (case 2) — True strain (4)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsT:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsT = 0.4094 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.8188 — kept a factor of two that cancels in the correct rearrangement.
- 0.2047 — dropped that same factor in the other direction.
- 0.4503 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
A student compares true strain to engineering strain for a stretched rod. Given original length (L0) = 1.8000 in; true strain (epsT) = 0.1170, determine the final length (Lf) in in.
Given
Find
final length (Lf), in in
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except Lf is given, so isolate Lf symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 5 — schematic for True strain — solve for final length (case 2) — True strain (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Lf:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Lf = 2.0234 in to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 4.0468 — kept a factor of two that cancels in the correct rearrangement.
- 1.0117 — dropped that same factor in the other direction.
- 2.2258 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
The true strain of a drawn wire is calculated from its length change. Given final length (Lf) = 2.1000 in; true strain (epsT) = 1.0640, determine the original length (L0) in in.
Given
Find
original length (L0), in in
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except L0 is given, so isolate L0 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 6 — schematic for True strain — solve for original length (case 2) — True strain (6)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for L0:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning L0 = 0.7247 in to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.4493 — kept a factor of two that cancels in the correct rearrangement.
- 0.3623 — dropped that same factor in the other direction.
- 0.7971 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
A materials engineer computes the true strain of a tensile specimen at necking. Given original length (L0) = 2.4000 in; final length (Lf) = 1.5000 in, determine the true strain (epsT).
Given
Find
true strain (epsT)
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except epsT is given, so isolate epsT symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 7 — schematic for True strain — solve for true strain (case 3) — True strain (7)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsT:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsT = -0.4700 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -0.9400 — kept a factor of two that cancels in the correct rearrangement.
- -0.2350 — dropped that same factor in the other direction.
- -0.5170 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
A student compares true strain to engineering strain for a stretched rod. Given original length (L0) = 4.6500 in; true strain (epsT) = 0.7850, determine the final length (Lf) in in.
Given
Find
final length (Lf), in in
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except Lf is given, so isolate Lf symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 8 — schematic for True strain — solve for final length (case 3) — True strain (8)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Lf:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Lf = 10.1947 in to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 20.3894 — kept a factor of two that cancels in the correct rearrangement.
- 5.0973 — dropped that same factor in the other direction.
- 11.2142 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
The true strain of a drawn wire is calculated from its length change. Given final length (Lf) = 1.5000 in; true strain (epsT) = 0.9680, determine the original length (L0) in in.
Given
Find
original length (L0), in in
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except L0 is given, so isolate L0 symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 9 — schematic for True strain — solve for original length (case 3) — True strain (9)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for L0:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning L0 = 0.5698 in to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.1395 — kept a factor of two that cancels in the correct rearrangement.
- 0.2849 — dropped that same factor in the other direction.
- 0.6267 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain
A materials engineer computes the true strain of a tensile specimen at necking. Given original length (L0) = 1.6000 in; final length (Lf) = 2.6500 in, determine the true strain (epsT).
Given
Find
true strain (epsT)
Start with the thinking
- The governing relation printed in this handbook section is True strain.
- Everything except epsT is given, so isolate epsT symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- True strain uses the natural log of the length ratio, unlike engineering strain's linear ratio.
Figure 10 — schematic for True strain — solve for true strain (case 4) — True strain (10)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for epsT:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning epsT = 0.5046 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.0091 — kept a factor of two that cancels in the correct rearrangement.
- 0.2523 — dropped that same factor in the other direction.
- 0.5550 — rounded an intermediate value before the final step.
Reference: FE Handbook — True Strain