Standard 25 mm
Pneumatic Vice Action Grip
Light, flat-faced grips for foil. Below about 0,076 mm the method calls for smooth inserts rather than serrated ones, because the serrations perforate the specimen.
SpecificationsTesting standard
ASTM E345
Standard Test Methods of Tension Testing of Metallic Foil
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM E345 covers tension testing of metallic foil in thicknesses less than 0,150 mm at room temperature, using Type A and Type B specimens. It gives strength and ductility for comparing materials, alloy development, quality control and design.
At a glance
- Test type
- Tensile — the specimen is pulled apart
- Published by
- ASTM
- Edition
- E345-24a
- Material
- Metals, alloys & welds
- Runs on
- Series 7200 and Series 9000
What the test does
A foil specimen thinner than 0,150 mm is cut to Type A or Type B geometry, its thickness measured carefully, and mounted flat and wrinkle-free in grips whose inserts are chosen by thickness — serrated for the thicker end of the range, smooth below about 0,076 mm. It is pulled at a constant rate at room temperature on a machine conforming to Practices E4, with strain measured by a non-contacting method where elongation is required. Strength and ductility come out, for comparing materials, alloy development, quality control and design.
What it measures, and why it matters
The same properties as any tension test, at a scale where everything that is normally a detail becomes the dominant source of error. That is really the subject of this method. The grip insert has to change because a serration that holds thicker metal punches through foil. The load cell has to be chosen for tens of newtons because the frame's own is working far outside its class. The thickness measurement, a rounding error on a bar, becomes a two per cent error on the strength. Foil has its own standard because at 0,150 mm all of those stop being manageable at once.
Thin enough to change the rules
Below a certain thickness the grip that holds thicker metal simply cuts through, so the insert changes with the specimen.
- Thickness
- Less than 0,006 in (0,150 mm)A scope limit. Above it, ASTM E8/E8M applies.
- Specimens
- Type A and Type B
- Temperature
- Room temperature
- Machine
- Conforming to Practices E4
- Grip inserts
- Wedge with serrated inserts, but SMOOTH below 0,003 in (0,076 mm)The clearest example on the site of a grip choice being written into a method: a serration that holds 0,1 mm foil punches through 0,05 mm foil.
- Handle by the tabs, never by the gauge
- DakA fingerprint crease in foil is a fold, and a fold is where it will break.
The load cell decides this test. Foil breaks below a hundred newtons, and an accuracy class applies only down to a stated fraction of capacity — so a frame's own cell is almost always the wrong instrument for it.
Test speed
- Rate
- A constant rate as specified
- Reported
- Strength and ductility
- Strain
- Non-contacting where elongation is neededDakA clip gauge's own weight and spring force are significant against a specimen this light.
- Reject jaw breaks and specimens with a visible crease
- Dak
Calculations
Tensile strength—
Maximum force divided by the original cross-sectional area
- area
- width times thickness, and the thickness is the difficult one
Foil thickness is a small number measured with an instrument whose own error is comparable to it. A one-micrometre error on 50 µm foil is two per cent straight into the strength.
Why the insert changes—
Serration depth becomes comparable to specimen thickness
A serrated jaw grips by indenting. When the indentation approaches the thickness of the material, it is no longer gripping — it is cutting.
How the test runs
- 01Confirm the thickness is below 0,150 mm; above that, use ASTM E8/E8M.
- 02Measure the thickness carefully, and record the instrument used.
- 03Cut Type A or Type B specimens as specified, avoiding burrs on the edges.
- 04Handle specimens by the tab ends only.
- 05Choose the grip inserts by thickness — smooth below 0,076 mm, serrated above.
- 06Select a load cell whose range suits a coupon breaking below 100 N.
- 07Verify the load cell class at that working load, not at frame capacity.
- 08Mount the specimen flat and free of wrinkles.
- 09Fit non-contacting strain measurement where elongation is required.
- 10Load at the specified constant rate to failure.
- 11Reject jaw breaks and creased specimens, and record how many.
Grips and fixtures for this method
Self-tighteningTJ-15
Universal Parallel Wedge Grips
Wedge grips with the appropriate inserts for the thicker end of the range.
SpecificationsWhat the report has to contain
- Reference to ASTM E345 and the edition
- Material, alloy and temper
- Specimen type — A or B
- Measured thickness and the instrument used
- Grip insert type and the reason for the choice
- Load cell capacity and its verified class at the working load
- Rate of testing
- Tensile strength and ductility values
- How strain was measured
- Number of specimens rejected and why
What the machine must be capable of
Very small forces measured traceably. A foil coupon commonly breaks below a hundred newtons, and an accuracy class applies only down to a stated fraction of capacity, so the frame's own load cell is almost always the wrong instrument — the class stops describing it long before the working load is reached. Grips must hold flat without cutting, with the insert type chosen by specimen thickness. Where elongation is reported, non-contacting strain measurement avoids a clip gauge loading the very specimen it measures.
What goes wrong in practice
Using serrated inserts below the thickness where they perforate rather than grip, which produces jaw breaks that look like weak foil. Oversized load cells. Creased or wrinkled specimens. Reporting a strength without saying how the thickness was measured, when that measurement carries a large share of the uncertainty. And running foil under ASTM E8/E8M because it is a metal, which is exactly the boundary this method exists to draw, and the reason it draws it at 0,150 mm rather than anywhere else.
ASTM E345 or ASTM E8/E8M
| ASTM E345 | ASTM E8/E8M | |
|---|---|---|
| Thickness | Below 0,150 mm | Above it |
| Grips | Insert type set by thickness | Conventional wedges |
| Load cell | Sized for tens of newtons | Sized for the section |
| Strain | Non-contacting preferred | Clip gauge routine |
The same measurement at a scale where the fixture and the instrumentation stop being incidental. Everything that is a detail on a 10 mm bar becomes the dominant error on 50 µm foil.
Questions we are asked about this test
What is ASTM E345?
It is the ASTM method for tension testing metallic foil — material thinner than 0,150 mm — at room temperature, using Type A and Type B specimens. It gives strength and ductility data for comparing materials, alloy development, quality control and design. The current designation is ASTM E345-24a.
Why do the grip inserts change with thickness?
Because a serrated jaw grips by indenting the specimen, and when the indentation depth approaches the material's thickness it stops gripping and starts cutting. The method calls for smooth inserts below about 0,076 mm for exactly that reason. It is the clearest case in any of these standards of a grip choice being written into the method rather than left to the laboratory.
Why is the load cell the limiting instrument?
Because a foil coupon commonly breaks below a hundred newtons, while a frame's own cell is usually sized for the frame. An accuracy class applies only down to a stated fraction of capacity, and below that fraction it no longer describes the instrument — so a kilonewton-scale cell measuring 40 N produces a precise-looking number with no traceable accuracy behind it.
Why is thickness measurement so critical here?
Because it is the divisor and it is very small. Strength is force over width times thickness, and on 50 µm foil a one-micrometre measurement error is two per cent straight into the reported strength — before any question about the force. The instrument used to measure it deserves recording alongside the value, which is not something a 10 mm bar ever requires.
Why not use a clip-on extensometer?
Because its own weight and spring force are significant against a specimen this light, so it loads the foil it is trying to measure. A non-contacting method avoids that entirely. It is the same reasoning that makes video or laser extensometry standard for elastomers, arriving from the opposite direction — there the extension is too large, here the specimen is too delicate.
Why does handling matter?
Because a crease in foil is a fold, and a fold is a stress concentration the specimen will break at. Fingerprints, tweezers in the wrong place and a specimen allowed to buckle in the grips all produce the same result: a low value at a location that has nothing to do with the material. Handling by the tab ends only removes most of it.
Where is the boundary with ASTM E8?
At 0,150 mm. Below that this method applies, above it ASTM E8/E8M does. The boundary is not arbitrary — it is roughly where conventional gripping, conventional extensometry and a frame's own load cell all stop being appropriate at the same time, which is why foil earned a method of its own.
Running ASTM E345 on the Series 7200 and Series 9000
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | Very low — a foil coupon commonly breaks below 100 N | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ASTM E4 — verified at the actual working load, which is a small fraction of most frames | Verified to ASTM E4, and to ISO 7500-1 Class 0.5 |
| Gripping | Light grips with faces chosen for the thickness — smooth below 0,076 mm, serrated above it | Our self-tightening serrated wedge grips, with V-jaws for round specimens, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.