A single-point, or 3-point, bend test uses one loading anvil, whereas a 4-point bend test uses two loading anvils. The selection of an appropriate bend fixture depends on the material you’re testing.
Did You Know: A four-point conversion kit may be available for most standard three-point fixtures. Contact us for additional information.
| Type of Bend Test | 3-Point | 4-Point |
| Type of Material | Homogeneous (plastics) | Non-Homogeneous (composites & wood) |
| Stress Concentration | Small and concentrated under the center loading point | Larger region to avoid premature failure |
| Specimen Deflection | Typically measured with the crosshead position | Typically measured with a deflectometer |
Did You Know: A four-point conversion kit may be available for most standard three-point fixtures. Contact us for additional information.
3 comments:
3 point bending will have higher fracture or 4 point bending have higher facture? why
If similar parts are measured by the 3 point bend and 4 point bend tests,can we expect the results to be similar?
Hi there,
As mentioned in the table above, the bend type is usually selected based on the material, not necessarily which test shows a higher load at fracture. In most cases, non-homogeneous materials tend to be stiffer and more brittle, so using a 4-point bend test will prevent the material from failing prematurely by distributing the load over 2 anvils. As one is subjecting the material to a larger area of force with the 4 point bend than with the 3 point bend test, the results will not always be similar. This will of course depend on what kind of material you are testing. Feel free to send us more information on your particular test so that we can make more specific recommendations!
Sarah_jastram@instron.com
Sarah
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