VDA 238-100

VDA 238-100 – Bend Test for Determining the Bending Angle and Force of Sheet Metal

VDA 238-100 is a standardized three-point bend test method used to evaluate the crash-relevant forming behavior of metallic sheets, particularly high-strength steels and aluminum alloys used in the automotive industry. It is widely used to simulate crash scenarios, assess formability, and guide material selection in lightweight vehicle construction.

What Does VDA 238-100 Measure?

The test measures how a metallic sheet bends under a centrally applied load, capturing:

• Maximum bending force

• Bending angle at failure or peak load

• Bending behavior (e.g., smooth bending vs. cracking or fracture)

This data is essential for crash simulation models and for designing structural components that must deform predictably under impact.

Test Specimen

Dimensions

Specimens are rectangular metal strips, typically with:

• Length: 60 mm to 100 mm

• Width: 20 mm to 50 mm

• Thickness (t): Material-dependent (commonly 0.8–2.0 mm for automotive steels)

The width and thickness should reflect the material’s end-use application and be consistent across tests.

Test Equipment and Fixture

Universal Testing Machine (UTM)

A servo-hydraulic or electromechanical UTM with high-speed data acquisition and force control is required. Typical load ranges are 10 kN to 100 kN, depending on material strength.

VDA 238-100 Bend Test Fixture

The key to the VDA 238-100 method is its customized three-point bending fixture, which includes:

• Two lower support rolls (diameter 20 mm ± 0.5 mm)

• One upper loading punch (also 20 mm diameter)

• Span width (support distance): Fixed at 60 mm

The punch and rollers are made of hardened steel, and the system must allow free rotation of the support rollers and low friction contact. The fixture ensures uniform stress distribution and reliable reproduction of crash-relevant bending.

Test Procedure

1. Specimen Positioning: Place the metal strip flat on the support rollers.

2. Loading: Apply a compressive force via the upper punch at a constant speed (commonly 10 mm/min).

3. Bending Angle Monitoring: Track the bending angle during deformation using an angle sensor or machine crosshead position, depending on test rig setup.

4. Failure Detection: The test typically ends at crack initiation, complete fracture, or max force achieved.

Key Measurements:

• Bending angle at max force

• Maximum force

• Mode of failure

Calculations and Bending Angle Formula

The bending angle (α) can be calculated based on the vertical displacement (h) of the punch using the following plain text formula:

α = 2 × arcsin[(h × (L/2)) / ((L/2)² + r²)]

Where:

• α = bending angle (degrees or radians)

• h = punch displacement (mm)

• L = span (support roller distance, typically 60 mm)

• r = radius of the rollers (typically 10 mm)

Note: In many test machines, the angle is recorded directly via an angle encoder, so this formula is used for verification or systems without sensors.

Typical Failure Modes

• Crack initiation at the outer bend radius

• Full fracture of the sheet

• Edge cracks or delamination in coated materials

Understanding the failure mode helps engineers predict how the material will behave in a real-world crash scenario.

Applications and Use Cases

VDA 238-100 is widely used in the:

• Automotive industry for body-in-white and crash component material selection

• Steel and aluminum R&D to benchmark new high-strength alloys

• Crashworthiness simulations for forming and energy absorption

It is particularly relevant for AHSS (advanced high-strength steels) and aluminum-magnesium alloys, which exhibit different bending behavior compared to mild steels.

Tips for Accurate Testing

• Ensure the rollers and punch are precisely aligned

• Use clean, burr-free specimens with consistent thickness

• Perform at least 5 repetitions to establish reliable data

• Calibrate angle measurement devices regularly if used

Related Standards

• DIN EN ISO 7438 – Bending test for metallic materials (less crash-focused)

• VDA 238-100:2016-11 – Official current version of the bend test

• ISO 16842 – Testing for high-speed deformation in crash-relevant applications

Conclusion

VDA 238-100 provides a critical measure of bending performance for metals used in crash-critical automotive components. Its reproducible method and robust fixture design allow engineers to compare materials accurately and make data-driven decisions in vehicle design and lightweighting strategies.

Looking to perform VDA 238-100 testing? We provide precision fixtures, load frames, and full compliance kits ready for high-throughput automotive labs or R&D environments.