EN 16955-2017 pdf download.Hardware for furniture – Tapered pressure tubes for selfsupporting gas springs for the height adjustment of seating- Test methods and requirements for strength and durability.
5 Test apparatus
5.1 Material testing machine
A material testing machine capable ol perrorming tests in accordance witn ISO iU’9 shati he used. ihe testing machine force measuring system shall be verified statically in accordance with EN ISO 7500-1:2016, Class 1.
5.2 Testing equipment for magnetic powder flaw test
A testing equipment for magnetic powder flaw test for the particle inspection for the detection of surface imperfections shall be used.
6 Test
6.1 General
For each combination of dimensions, production procedure, surface finish, materials or condition of the material or any other characteristic which affects the strength and durability, a separate test shall be conducted.
6.2 Strength and durability
6.2.1 SamplIng
The test samples shall consist of 32 pressure tubes taken on a random basis from the series production.
Any kind of marking on the pressure tube shall be done before strength and durability test.
6.2.2 Test procedure
6.2.2.1 Test setup
The test setup is shown in Figure 2.
6.2.2.2 Test procedure
The test shall be performed according to ISO 1099.
The alternate bending moment M shall be as specified in Table 1. It shall act in parallel to the longitudinal axis of the pressure tube. The length of the lever arm which applies the force is (150 ± 5) mm. The time characteristic of the test force shall be sinusoidal. The stress cycle frequency shall not exceed 30 Hz. The alternate bending stress shall be applied with stress regulation. The temperature of the test piece shall not exceed 50°C during the test.
To determine the strength and durability, the alternate bending stresses shall be applied in 2 x 106 cycles and a mean stress of 0.
6.2.3 Evaluation and requirement
After the test, the surfaces of the test pieces shall be subjected to a magnetic powder flaw test over their entire length and their entire circumference.
The magnetic powder flaw test shall be performed on pressure tubes made of unalloyed and low- alloyed steels with alternating current magnetization. The test areas shall be cleaned and free of interfering impurities. Suitable test apparatus shall be used to ensure that a tangential field strength of at least 2 kA/m is achieved. Wet test media shall be used for the test. The particle size of the magnetic powder shall be according to EN ISO 9934-2.
Only carrier liquids which do not cause any corrosion to the subject of the test shall be used. If oil is used as a carrier agent, the sort selected shall be easily removed and leave no interfering residue. Marked test oils are suitable.
If water is used as a carrier agent, it can he necessary to use additives to ensure that the surface is properly wet (amount according to manufacturer’s instructions). The detection sensibility shall not be impaired by these additives.
The test is deemed to have been passed if no cracks or fractures are seen on any of the 32 pressure tubes tested.
7 Test report
Each type test shall be documented in a test report.
The test report shall contain at least the following information:
— address of testing laboratory;
— date of testing.
— date of production of the pressure tubes;
— full description of the pressure tubes (e.g. type, material, surface finish, dimensions);
— manufacturer of the pressure tubes;
— dimensions of the test fixture (according to the details supplied by the manufacturer of the pressure tubes);
— overlap 13 in test fixture;
— alternate bending moment and the strength class;
— cycle frequency;
— documentation of the test equipment and the test setup;
— condition of the test pieces after the magnetic powder flaw test (fracture, visible crack lengths).
8 Marking of the pressure tube
The following shall be marked indelibly in a clearly visible place on each pressure tube:
— manufacturer;
— type designation of the manufacturer;
— reference to this European Standard and strength class (according to Table 1) (e.g. EN 16955-2).EN 16955-2017 pdf download.
EN 16955-2017 pdf download
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