Testing of Fasteners

First and foremost among fasteners are nuts and bolts in all their many variations; yet screws, rivets and hooks and eyes are also used to join components and metal sheets and sections, which must not separate under load. Fastener technology in general, particularly welding and associated technologies, also belong to this group. Relevant standards are DIN EN ISO 9015-1 and -2, as well as DIN EN ISO 14271 and DIN ISO 22826. 

Tensile Tests

Threaded fasteners are selected very carefully with regard to their industrial application and are integrated carefully into the design. Accurate determination (via tensile tests) of the elastic tensile modulus and the limits of elastic loading is essential, since these values determine the limit forces required for a secure, reliable threaded connection. Because there are so many applications, a vast range of screws and bolts of many different types is required. Zwick’s comprehensive selection of specimen grips, with the option of customized solutions, simplifies testing in this area.

Shear Tests

In addition to single-axis tensile loading, shear loads also occur in fasteners in service and can quickly cause a joint to part. Shear tests on joined parts or specimens are therefore essential, particularly where riveted joints are involved. Accurate load application is essential to prevent other forces arising in addition to the shear force and distorting results. Zwick works with you to develop a specification for the correct gripping of the specimen or component and then produces the required arrangement. These test devices can be simple or very complex, but always do exactly what is required of them.

Fatigue Tests

In addition to static loads, fasteners in general are subjected to frequent cyclic loading, including vibrations. Fatigue tests on screws and bolts are most quickly and efficiently performed in a Vibrophore, which can apply cyclic loads with a maximum force of up to 1000 kN in a frequency range up to approx. 285 Hz, using grips designed specifically for screws/bolts and other fasteners. The magnetic drive, which generates controlled resonance in the system, including the specimen, requires minimal power during this test, resulting in highly cost-effective testing. In what are referred to as "H" specimens, the individual joints are subjected to common cyclic loading in tension and compression and the fasteners to a shear effect. H specimen holders designed for this test initially distribute the forces over the entire structure. The bending and resultant loosening of the structure can be measured with an extensometer. With the strain values, the testing machine—once again a Vibrophore—can also provide control of loads or strain, depending on how the test is conducted.

Additional Tests for Fasteners

  • Flexure and compression tests
  • Torsion tests
  • Hardness tests
  • Creep tests
  • Drop weight tests