What Is Bend?
Veneer bending test, in which the veneered panel bends around a cylindrical or conical mandrel of defined diameter; It is a test that evaluates whether there is cracking in the coating or separation from the lower surface.
Purpose of Bend
The aim is to verify that the coating can flex without cracking under forming and service deformations.
Which Products Is Bend Applied To?
- Coated sheet and strip products
- Painted panels to be shaped
- Powder coated parts
- Coated pipe and profile
In Which Sectors Is Bend Used?
Standards Related to Bend
- ISO 1519 (silindirik mandrel)
- ISO 6860 (konik mandrel)
- ASTM D522
- ASTM D4145
Bend Conditions
- Mandrel diameter
- Diameters defined in the standard; The smallest crack-free diameter is determined
- Bending
- At defined speed and angle; coating on the outer surface
- Conditioning
- The coating is fully cured and conditioned in the environment defined in the standard.
- Assessment
- Crack inspection under magnification; tape test if necessary
Equipment for Bend
- Cylindrical and conical mandrel testing devices
- Coating-thickness gauge
- Magnifier or stereo microscope
- Conditioning room
Sample Requirements for Bend
- Panel bottom material thickness must comply with the specification
- Coating thickness must be measured
- Panel edges must be free of notches
- The coating must be fully cured
Duration of Bend
Typically 1–2 days.
Bend Procedure
- 1The panel is conditioned and the thickness is measured.
- 2Mandrel diameter is selected.
- 3The panel covering is bent to the outside.
- 4The bending region is examined with magnification.
- 5If necessary, it is repeated with smaller diameters.
- 6The smallest mandrel diameter without cracking is reported.
Bend Acceptance Criteria
The acceptance criterion is the absence of cracks and separation within the mandrel diameter given in the specification.
Evaluation of Results
The thickness of the substrate directly affects the result; Thicker sheet metal cracks earlier in the same coating. At low temperature, coatings become brittle, so the specification may call for low temperature warping.
Bend Report
- Standard applied
- Substrate material and coating thickness
- Mandrel diameters
- Conditioning and temperature
- Crack findings
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Paint and coating specifications
Otomotiv Testleri — What Does This Testing Field Cover?
The section below describes the field that the Bend test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Automotive testing shows that a component keeps working under conditions representing the loads it will meet over the life of the vehicle. A vehicle is not a single product but an ENVIRONMENT: vibration, temperature cycling, salt water, stone impact, electrical transients and electromagnetic noise are all present at the same time and for years.
What distinguishes this family is that VEHICLE MANUFACTURER SPECIFICATIONS sit on top of the standards. ISO and SAE publications establish the common ground; but Volkswagen, BMW, Ford, Stellantis, Toyota and Renault define different severity levels, additional tests and different acceptance criteria in their own specifications. For a component, the phrase "complies with automotive standards" is not sufficient on its own; which manufacturer's specification, and which revision of it, must be answered.
The family carries three separate processes together and they are often confused. Homologation covers the type approvals a vehicle needs to enter traffic and runs under state authority. Supplier approval means passing the vehicle manufacturer's own quality and testing requirements and is a commercial relationship. The third is design verification: the engineering team demonstrating that its own design meets its targets.
At component level the test plan is built around the LOCATION OF USE. A module in the engine bay and a module in the boot do not go through the same temperature and vibration profile; a component inside a door and one in the roof console do not see the same water and dust exposure. The ISO 16750 series is the common framework for this location-based approach.
The shift to electric vehicles has reshaped the field. High-voltage safety, insulation coordination, battery safety, charging interface conformity and the electromagnetic behaviour of high-voltage components have been added to the classical automotive test set. In a quiet vehicle, acoustic and vibration expectations have changed too; sounds once masked by the combustion engine are now audible.
The quality system side cannot be separated from testing in this field. A manufacturer under IATF 16949 presents test results in the PPAP file; measurement system analysis, process capability study and the control plan stand around the test report. A single good result is not enough — the process must be shown to be able to repeat it.
Method groups in this field
Environmental and climatic
Temperature cycling, thermal shock, damp heat, salt spray, dust and water ingress (IP), solar radiation. Severity levels vary with the mounting location.
Mechanical
Sine and random vibration, shock, mechanical loads, fastener torque and durability cycles.
Electrical
Supply voltage variations, transients (ISO 7637), reverse polarity, overvoltage, short circuit and sleep current measurements.
EMC
Component emissions (CISPR 25), radiated and conducted immunity (ISO 11452 series), electrostatic discharge (ISO 10605).
Materials and emissions
Odour, fogging and VOC emissions from interior materials; flammability; UV ageing; coating durability and stone impact.
Functional safety and cyber security
Functional safety evidence under ISO 26262 and cyber security engineering under ISO/SAE 21434; these are tied to regulation through UNECE R155 and R156.
Commonly confused in this field
- An automotive report without a specification reference is not accepted in the supply chain; which OEM specification and revision was applied must be stated.
- Type approval and supplier approval are different processes. A component with E-Mark approval is not thereby considered to have passed the OEM's own acceptance tests.
- A result obtained on a prototype does not carry over to series production; PPAP is done with series production parts.
- On the EMC side, measuring emissions alone is incomplete; immunity is a separate body of work and is more critical in a vehicle.
- On electric vehicle components, high-voltage safety is a distinct competence; classical 12 V test infrastructure is not sufficient.
Which decisions these results support
- Supplier component approval and the PPAP file
- UNECE type approval and E-Mark marking
- Design verification and durability evidence
- Root cause analysis of field complaints and warranty returns
- Assessing the impact of a design or supplier change
Related Tests
Frequently Asked Questions About Bend
According to which standard is Bend made?
Bend is executed in scope ISO 1519 (silindirik mandrel), ISO 6860 (konik mandrel), ASTM D522 and ASTM D4145. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Bend apply to?
Mainly applied to Coated sheet and strip products, Painted panels to be shaped, Powder coated parts and Coated pipe and profile. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Bend done?
The determining parameters are: Mandrel diameter — Diameters defined in the standard; The smallest crack-free diameter is determined, Bending — At defined speed and angle; coating on the outer surface and Conditioning — The coating is fully cured and conditioned in the environment defined in the standard.. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Bend?
Panel bottom material thickness must comply with the specification, Coating thickness must be measured and Panel edges must be free of notches. The number of samples is determined according to the product standard and the scope to be reported.
How long does Bend take?
Typically 1–2 days. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Bend result called "appropriate"?
The acceptance criterion is the absence of cracks and separation within the mandrel diameter given in the specification.