Self-identifying
Load Cells
Cross tension forces are markedly lower than shear forces on the same joint, often by a factor of two or three. A load cell sized for the joint rather than the frame is what keeps the peak resolved.
SpecificationsTesting standard
ISO 14272
Resistance welding — Destructive testing of welds — Specimen dimensions and procedure for cross tension testing of resistance spot and embossed projection welds
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 14272 welds two strips together in a cross and pulls them apart through the thickness of the sheet, so the spot weld is opened rather than sheared. The maximum force is the cross tension force, and its ratio to the tensile shear force on the same joint is a working measure of weld ductility. The current edition is ISO 14272:2016.
At a glance
- Test type
- Tensile — the specimen is pulled apart
- Published by
- ISO
- Edition
- ISO 14272:2016
- Runs on
- Series 7200 and Series 9000
What the test does
Two strips are spot welded together in a cross, one laid over the other at right angles, and each strip is bolted into a fixture that pulls it away from the other through the thickness of the sheet. The weld is therefore opened rather than sheared. The maximum force the joint carries before it fails is the cross tension force.
The specimen is held by its four arms in a dedicated jig, not by grips on the sheet itself, because the load has to be applied normal to the weld and a flat grip cannot do that.
What it measures, and why it matters
Cross tension loads a spot weld in its weakest direction. Where tensile shear asks how much in-plane load the joint carries, cross tension asks how well the nugget resists being pulled apart — which is closer to what happens in a vehicle crash, where sheets peel and pry rather than slide past one another.
The ratio between the cross tension force and the tensile shear force on the same joint is a working measure of weld ductility. A high shear force with a low cross tension force is the signature of a hard, brittle nugget: strong in its best direction and fragile in its worst. That combination is common in advanced high-strength steels, where the same alloying that gives the sheet its strength gives the weld a martensitic nugget, and it is exactly what a crash structure must not have. This is the test that finds it.
The cross specimen
The specimen is held by its four arms in a jig, not by grips on the sheet, because the load has to arrive normal to the weld.
- Joint
- One spot or embossed projection weld at the intersection of two strips
- Material
- Any metallic material
- Sheet thickness
- 0.5 mm to 3 mmLower than the 10 mm of ISO 14273, because the arms are bolted flat into the jig and thicker sheet stops behaving as the geometry assumes.
- Maximum weld diameter
- 7√t, with t the sheet thickness in mm
- Arrangement
- Two strips at right angles, welded at the centre of the intersection
- Fixing
- Clearance holes in each arm for the fixture bolts
- Coating
- Left on — never removed before testPractice
- Check the arms are square before welding
- DakA cross that is a few degrees out loads the nugget partly in peel. The force comes out low and nothing in the record says why.
Rate, and what the machine records
- Loading
- Continuous tensile loading normal to the sheet plane, to failure
- Rate
- As specified in the standard; not publicly quotableThe loading rate sits in the purchased text. Fix it and hold it constant across any comparison.
- Reported
- Maximum force, in N or kN, plus the failure mode
- Sampling rate
- High enough to catch an abrupt peakDak
What the numbers are used for
Cross tension force—
The maximum force recorded before the joint fails
A force, not a stress, for the same reason as tensile shear: the nugget area is unknown until the weld is destroyed.
Ductility ratio—
Cross tension force divided by tensile shear force on the same joint
- cross tension force
- peak force from this method, N
- tensile shear force
- peak force from ISO 14273 on an equivalent joint, N
Not defined by the standard, and widely used. A high shear force with a low cross tension force is the signature of a hard, brittle nugget — strong along the sheet and fragile through it.
Why crash work needs this test—
Crash loading peels and pries; it does not shear cleanly
A joint can pass in tensile shear and fail here. The shear figure alone is not evidence of crash performance.
How the test runs
- 01Cut the two strips and drill the fixture clearance holes.
- 02Assemble them at right angles and weld at the centre of the intersection.
- 03Check the arms are square and the weld is central.
- 04Measure and record sheet thickness and weld diameter.
- 05Bolt one pair of arms to each half of the cross-tension jig.
- 06Tighten the bolts evenly, to the same torque on every arm.
- 07Connect the jig halves to the machine through pins or clevises so the assembly can self-align.
- 08Load continuously to failure at the specified rate.
- 09Record the maximum force.
- 10Classify the failure mode and report it with the force.
Uneven bolt torque is the fault that spoils this test most often. Arms that lift under load turn a normal tensile load into a partial peel, and the number that results is low, plausible and wrong. Worn bolt holes in the jig do the same thing gradually enough that nobody notices.
The fixture this method needs
What the report has to contain
- Reference to ISO 14272 and the edition
- Parent material, grade, coating and thickness of both strips
- Welding parameters: current, weld time, electrode force and geometry
- Strip width, arm length and hole positions
- Weld diameter where measured, and how
- Test rate
- Maximum force for each specimen
- Failure mode for each specimen
- Mean and the number of specimens
- Where a shear figure is quoted alongside, the standard it came from
What the machine must be capable of
Cross tension forces on thin sheet are lower than shear forces on the same joint, often by a factor of two or three, so a 50 kN frame is ample for most automotive work and resolution at the low end matters more than capacity. Force accuracy to ISO 7500-1 Class 1 is the normal requirement.
The fixture is what makes or breaks this test. Two mating plates, each bolted to one arm pair of the cross, are connected to the machine through pins or clevises so that the load line passes through the weld and the assembly can self-align. A jig that is stiff in the wrong place forces a bending moment into the joint and the result drifts low. Because it is a jig rather than a grip, the fixture is normally made to the standard's drawing for the sheet thickness being tested, and Dak builds fixtures of this kind to the specimen and to the method.
No extensometer is needed — the result is a force. A data rate fast enough to catch an abrupt peak is needed, as it is for all spot-weld testing.
What goes wrong in practice
Bolts left loose, or tightened unevenly, let the arms lift and turn a normal load into a partial peel. Specimens whose arms are not square to one another do the same. Fixture wear around the bolt holes is a slow version of the same fault and is easy to miss because it degrades gradually. As with the other two methods, recording the force without the failure mode discards half the result: a button pull-out and an interfacial fracture at the same force describe two entirely different welds.
Cross tension against tensile shear
Two directions on the same joint. The pair is more informative than either alone, and the pairing is the point.
| Cross tension (ISO 14272) | Tensile shear (ISO 14273) | |
|---|---|---|
| Load direction | Through the sheet thickness | Along the plane of the sheets |
| Nugget loaded | In its weakest direction | In its strongest direction |
| Thickness covered | 0.5 mm to 3 mm | 0.5 mm to 10 mm |
| Held by | A bolted cross-tension jig | Flat grips with packing shims |
| Typical force | Lower, often by a factor of two or three | Higher |
| Answers | Is the nugget ductile | Is the joint strong enough |
Advanced high-strength steels are where the two diverge most. The alloying that gives the sheet its strength can give the weld a martensitic nugget: excellent in shear, poor in cross tension. A crash structure specified on shear results alone has not been tested for the loading it will actually see.
Questions we are asked about this test
What is ISO 14272?
ISO 14272 is the international method for cross tension testing of resistance spot and embossed projection welds. Two strips are welded together in a cross and each is bolted into a fixture that pulls it away from the other through the thickness of the sheet, so the weld is opened rather than sheared. The current edition is ISO 14272:2016, issued with a corrected version dated 1 September 2016.
Why not just run tensile shear?
Because tensile shear loads a spot weld in its strongest direction. Cross tension loads it in its weakest, which is much closer to what happens in a crash, where sheets pry and peel apart rather than sliding past one another. A joint can pass comfortably in shear and fail in cross tension, and that combination is common enough in advanced high-strength steels that shear results alone are not evidence of crash performance.
What does the ratio of cross tension to shear force tell you?
It is a working measure of weld ductility, though the standard does not define it. A high shear force with a low cross tension force means a hard, brittle nugget: strong along the sheet, fragile through it. That pattern points at the nugget metallurgy — often martensite formed by rapid quenching through the copper electrodes — rather than at nugget size, and it is a reason to look at hold time and post-weld tempering.
Why does it need a jig rather than grips?
Because the load has to arrive normal to the weld. A flat grip clamped on the sheet can only pull along the sheet. The cross-tension fixture is two mating plates, each bolted to one opposing pair of arms, connected to the machine through pins or clevises so the assembly can self-align on the weld. Where a specimen falls outside a published fixture, Dak builds the fixture to the specimen and to the method.
What is the most common way this test goes wrong?
Bolt torque. Arms that are loose, or tightened unevenly, lift as the load builds, and a normal tensile load becomes a partial peel. The recorded force drops and the failure mode changes, so the result reads as a bad weld rather than a bad set-up. Worn bolt holes in the jig produce the same error slowly enough that it is usually blamed on the material.
What machine does it need?
A 50 kN frame is ample for most automotive sheet, because cross tension forces are lower than shear forces on the same joint. Force accuracy to ISO 7500-1 Class 1 is the normal requirement and low-end resolution matters more than capacity. The data rate has to be fast enough to catch an abrupt peak, since a spot weld gives no warning before it goes.
Is the failure mode as important as the force?
Yes, and on this test more than on the others. A button pull-out and an interfacial fracture recorded at the same peak force describe two entirely different welds: the first tore the parent sheet, the second parted across the weld face. Cross tension is the loading most likely to expose an interfacial failure that a shear test passed, so a report that gives force without failure mode has thrown away the finding.
Running ISO 14272 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 | Lower than the tensile shear force on the same joint, often by a factor of two or three; a 50 kN frame covers automotive sheet | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ISO 7500-1 Class 1 | ISO 7500-1 Class 0.5 — a class tighter than the method asks |
| Gripping | A bolted cross-tension jig taking the four arms of the cross specimen, connected through pins or clevises so it self-aligns | Our a fixture built for this method, built to the specimen |
| Environment | Ambient laboratory conditions; no conditioning atmosphere is specified | 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.