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Bend test

Definition: The bend test is a mechanical testing method for determining the deformation and fracture behaviour of a material under bending load. In this test, a specimen is bent by a defined force around a test mandrel or between supports. For metals, the procedure is governed by DIN EN ISO 7438.

Practical relevance: The properties assessed are bending strength, bending angle, crack formation and plastic formability. The test serves the quality control of sheets, weld seams and coatings as well as the assessment of ductility. Influencing factors are specimen geometry, bending radius and test speed. Visible cracks or spalling are considered a rejection criterion in accordance with the specification.

Decision-making perspectives:

  • Technical decision-makers: Assessment of the formability and integrity of welded joints.
  • Purchasing/project management: Definition of normative testing requirements and acceptance criteria.
  • Science: Analysis of stress distributions and crack initiation under bending load.
  • Insurance/law: Documentation of mechanical properties in disputes over material quality.

Typical testing or verification methods: Three-point or four-point bend test, visual crack inspection, metallographic examination after testing.

FAQ:

  • Which standard applies to the bend test on metals?
  • DIN EN ISO 7438 describes the performance and assessment of the bend test on metallic materials.

Brazing Procedure Qualification Testing

Definition: Brazing procedure qualification testing is the qualifying examination of a brazing process to ensure reproducible joints that conform to standards. It serves to demonstrate that a defined brazing procedure achieves the required quality under specified parameters. Requirements are governed, among others, by DIN EN ISO 13585.

Practical relevance: The aspects assessed include braze seam quality, wetting, freedom from porosity, strength and tightness. Influencing factors are the temperature profile, filler material, flux and joint gap. The tests comprise visual inspection, metallographic sections, and tensile or shear tests. Procedure qualification is frequently a prerequisite for safety-relevant applications.

Decision-making perspectives:

  • Technical decision-makers: Ensuring suitable process parameters and material combinations.
  • Purchasing/project management: Requiring qualified procedures and documented test reports.
  • Science: Analysis of diffusion zones and intermetallic phases.
  • Insurance/law: Demonstration of standard-compliant procedure qualification in the event of a failure.

Typical testing or verification methods: Visual inspection, metallographic examination, tensile/shear test, leak test.

FAQ:

  • Why is a brazing procedure qualification test required?
  • It ensures that the selected brazing procedure reproducibly delivers the required quality under defined conditions.

Brinell Hardness Test

Definition: The Brinell hardness test is a static indentation method for determining the hardness of metallic materials. A carbide ball is pressed into the surface with a defined test force, and the indentation diameter is measured optically. The method is standardised in DIN EN ISO 6506.

Practical relevance: The hardness is given as HBW (Hardness Brinell Tungsten carbide), e.g. HBW 10/3000. The method is particularly suitable for soft to medium-hard materials such as structural steels, cast iron or non-ferrous metals. Test force, ball diameter and dwell time are relevant to the assessment. The Brinell hardness frequently correlates with tensile strength and is used for incoming goods inspection or component testing.

Decision-making perspectives:

  • Technical decision-makers: Checking heat treatment conditions and the homogeneity of larger components.
  • Purchasing/project management: Specifying required hardness ranges in material standards or orders.
  • Science: Comparison with other hardness methods (Vickers, Rockwell) and correlation with mechanical characteristic values.
  • Insurance/law: Documented hardness verification for assessing material deviations.

Typical testing or verification methods: Optical indentation measurement, calibration in accordance with ISO 6506-2, comparative measurements with reference blocks.

FAQ:

  • When is the Brinell hardness test preferably used?
  • For coarse-grained or inhomogeneous materials as well as for larger components with medium hardness.
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