# Flexure Test

Along with the tensile test and the compression test, the flexure test is one of the most frequently used types of loading. The flexure test (also referred to as bending test) therefore has great significance in testing a wide range of materials, and is used for the determination of mechanical material characteristics of metals, plastics, wood, paper, cardboard, ceramics and more. Flexure tests are also used in the areas of quality control and research and development of medical products, including the break resistance of injection needles, flexural strength of medical tubing and catheters, the strength of bone plates, and much more.

Flexure test characteristic values are generally obtained via the 2-point flexure test, 3-point flexure test or 4-point flexure test. Specimens with rectangular cross-sections are preferred for use with flexure tests.

Flexure tests according to industry and standardized methods:

## Why flexure tests?

Flexure tests are performed to determine important mechanical characteristics. In particular, this test is used for tests on brittle materials, since the specimen causes metrological problems during the tensile test due to its failure behavior.

## What can you determine using a flexure test?

Depending on the material, different material properties can be determined. The results or characteristic values of the flexure test show, in particular, the material behavior near the surface of the specimen. The deflections measured are approximately four times greater than the extensions in a tensile test.

Typical test results/characteristic values are:

• Strength testing of materials
• Calculation of the flexural stress and strain
• Flexural modulus
• Bending stiffness
• Flexural resistance
• Stress at 3.5 % elongation
• Stresses and elongations at the yield point and at specimen break
• etc.

## How does the flexure test work?

There are three different types of flexure tests:

• 2-point flexure test
• 3-point flexure test
• 4-point flexure test

## 2-point flexure test

In the 2-point flexure test, the specimen is gripped at one end and loaded with a test die on the exposed side.

### 2-point flexure test kits

In the 2-point flexure test, the specimen is gripped at one end and loaded with a test die on the exposed side.

The 2-point flexure test kit is suitable for testing paper, cardboard, and films. It is used to determine the bending stiffness (using the beam method) and bending resistance of paper, board, and cardboard, e.g. to DIN 53121, ISO 5628 and DIN 19304, plastic films for example to DIN 53350 and coated textiles.

ZwickRoell also offers special 2-point flexure test kits for testing of injection needles to ISO 9626, determination of the kink resistance of guidewires, or the flexural strength of stiffer medical tubing (catheters, etc.).

• Product Information: 2-point Flexure Test Kits PDF 518 KB

## 3-point flexure test

In the 3-point flexure test, the specimen is positioned on two supports and loaded in the center with a test die.

### 3-point flexure test kit

The loading device consists of two parallel-positioned anvils for the specimen and an upper anvil positioned centrally between the anvils. The upper anvil applies the load to the specimen.

Depending on requirements (standard), the anvils and upper anvils must have fixed, rotating or rocking mountings to enable testing in accordance with specifications.

The test is mainly used for tough and elastic materials.

To minimize frictional influences during testing the anvils can be mounted so as to rotate around their longitudinal axis. Rocking mountings can be used with the upper anvil and anvil supports to ensure that they are parallel to the specimen.

• Product Information: 3-point Flexure Test Kits PDF 246 KB

## 4-point flexure test

In the 4-point flexure test, the specimen is positioned on two supports and loaded in the center with a test die with two points of contact.

### 4-point flexure test kit

As with the 3-point flexure test, the 4-point flexure test kit consists of two parallel-positioned anvils which, depending on the test requirements, must have fixed, rotating or rocking mountings.

The difference from the 3-point flexure test lies in the way in which the load is applied to the specimen. This is done via 2 upper anvils located symmetrically to the anvils. The bending moment is then constant between the two force application areas.

This test is primarily used to determine the modulus of elasticity in bending for brittle materials.

The Dynstat flexure and impact bending test to DIN 53435 is used in the characterization of material properties for components made of plastics if, for example, only relatively small specimens can be taken from finished injection molded parts due to space constraints.

• Product Information: 3- and 4-point Flexure Test Kits PDF 271 KB

## Plastics flexure tests - standardized methods

3-point flexure test plastics
ASTM D790
to 3-point flexure test plastics
3-point bend test plastics
ISO 178
to 3-point bend test plastics
Dynstat bending test and impact test
DIN 53435
to Dynstat bending test and impact test

## Metals flexure test - standardized methods

3-point flexure test kit for small plate bending test
This 3-point flexure test kit is used to perform the small plate bending test according to VDA 238-100:2017-06 for determination of the bending angle with the objective of reaching conclusions about the deformation behavior of metallic materials during forming processes with dominant bending elements (e.g. hemming operations) or during crash loading.
to 3-point flexure test kit for small plate bending test
Flexure test on metals
ISO 7438, ASTM A370, ISO 8491
to Flexure test on metals
U-bend test on metals
to U-bend test on metals

## Flexure tests on composites

Flexure test on composites
ISO 14125, ASTM D7264, EN 2562, EN 2746
to Flexure test on composites

## Flexure tests on paper and cardboard

2-point flexure test paper
ISO 2493-1, DIN 53121, ISO 5628, DIN 55437-3, DIN 19304
Determination of the flexural strength of paper and cardboard
to 2-point flexure test paper
3-point flexure test on paper and cardboard
Solid board, paper-based composites and reel cores
to 3-point flexure test on paper and cardboard
Buckling resistance of corrugated board
DIN 54608
to Buckling resistance of corrugated board
4-Point flexure test on corrugated board
DIN 53121, ISO 5628
to 4-Point flexure test on corrugated board
Test creasings, cardboard
DIN 55437-1
Accurate determination of the setting parameters for creasing units (creasing knife width, creasing groove width, creasing depth)
to Test creasings, cardboard

## Flexure tests in the medical and pharmaceutical industry

Break resistance of injection needles
ISO 9626
The break resistance of injection needles is determined to EN ISO 9626 using a 2-point flexure test.
to Break resistance of injection needles
Snapoff ampoules break point
Modular test kit for break forces on snapoff ampoules.
to Snapoff ampoules break point
Flexure test on guide wires/catheters/tubes
ZwickRoell offers the right testing system for flexure tests on guide wires, catheters, and tubes.
to Flexure test on guide wires/catheters/tubes
Flexure test on ceramics
EN 843-1 and ISO 6872
The test kit is designed for flexure tests on ceramics to EN 843-1, specimen shapes A and B, and ISO 6872.
to Flexure test on ceramics
Bone plates
ASTM F382 and ISO 9585
Flexure Test on Metallic Bone Plates and Fixation Devices to ASTM F382 and ISO 9585 (Osteosynthesis Plates)
to Bone plates

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