In the VW 60252 standard developed by Volkswagen automobile company, the requirements for bolts used in vehicle production and subjected to high dynamic stress are explained and a test method is defined.
In automobile manufacturing, a bolt is subjected to various stresses during assembly. Anchor deformation exposes the bolt to complex stress conditions, namely tension, compression, bending and shear. The bolt is affected by both tension and compression in the axial direction, while in the transverse direction it is affected by shear force and shear stress as well as bending moment.
Thread breakage in bolts subjected to stress is generally undesirable because this is a less ductile failure mode than fracture of the threaded shank of the bolt. Another problem is that incipient failure of the threads due to overtightening is difficult to detect during installation. In this regard, bolts subjected to stress must be of the open type and equipped with approved protection to prevent loosening of these bolts or nuts.
The weakest point in a bolt is the stressed area at the root of the thread. The stressed area depends on the tooth type, and thick teeth reduce the stressed area compared to fine teeth. A reduced area reduces the breaking load of the bolt, so coarse threads are used for clamping. Fine threaded bolts are weaker due to the reduced thread height.
The ISO 898-1 standard specifies the tensile stress range in bolts and the mechanical properties of fasteners made of carbon steel and alloy steel (ISO 898-1 Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Bolts, screws and studs of specified property classes - Coarse and fine thread). This standard describes the mechanical and physical properties of bolts, screws and studs made of carbon steel and alloy steel when tested at ambient temperatures between 10 and 35 degrees Celsius. Fasteners (bolts, screws and studs) may not maintain the specified mechanical and physical properties at higher or lower temperatures.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides testing services for bolts exposed to high dynamic stress within the scope of VW 60252 standard, with its trained and expert staff and advanced technological equipment.
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