At the impact test with the spring-operated impact hammer, as prescribed by the relevant specification, the specimen shall either:
a) be mounted by its normal means on a rigid plane support.
b) be placed against a rigid plane support.
In order to ensure that the specimen is rigidly supported, it may be necessary when performing the test to place the specimen against a plane solid support, for example a wall or a floor made of brick or concrete, covered by a sheet of polyamide which is tightly fixed to the support.
Care shall be taken to ensure that there is no appreciable air gap between the sheet and the support. The sheet shall have a Rockwell hardness of 85≤HRR≤100 according to ISO 2039-2, a thickness of approximately 8 mm and a surface area such that no parts of the specimen are mechanically over stressed due to the supporting area being insufficient.
The mounting arrangement is deemed to be sufficiently rigid if the displacement of the impact surface of the plane support does not exceed 0,1 mm when struck by and impact applied directly to it with the same level of energy as for the specimen.
Unless otherwise specified by the relevant specification, the blows shall be applied perpendicularly to the tested surface. Following above step, the test result is correct only.