Test systems for measuring the coefficient of friction on bolted joints

Customers benefit from minimal downtimes and lower costs during on-site service, as well as from an integrated, standard-compliant calibration of the entire measuring chain.

The complexity of bolted joints is constantly increasing with new areas of application such as wind turbines or electromobility leading to a growing variety of surfaces and coatings. With this development, bolted joints are also becoming more complex. Wind turbines, for example, use high-strength, pretensionable screw sets that require complete traceability of the production history as well as special material controls and test procedures.

Here, analysis systems help to investigate the effects of different bolt shapes, materials, lubricants and other factors and to determine and document their influence on friction values. Kistler has many years of experience in the construction of customized testing systems, which can also record very high torques to fulfil customer requirements.

Like all measuring and test devices, these analysis systems also need to be calibrated regularly. This is the only way to reliably monitor the precision and stability of the measuring chain used and to ensure standard-compliant processes during production. Traceable calibrations which means calibrations that are traceable to national or international standards are a high internationally recognised standard.

Numerous norms, such as IATF16949 in the automotive industry, exclusively require traceable calibrations, which only accredited laboratories are permitted to carry out. The German Accreditation Body DAkkS issues accreditations for permanent calibration laboratories, for mobile laboratories or for on-site calibrations. Unlike in a permanent laboratory, external influences such as the ambient temperature during calibration, can only be influenced to a limited extent in on-site calibrations. Kistler's expertise in the field of measurement technology therefore plays a particularly important role.

On-site calibration reduces cost

On-site calibrations have many advantages: the service time of the system is minimal there is no need for time-consuming dismantling and assembly work and the measuring system is calibrated holistically on site as the entire measuring chain is included. The current expansion of the scope of accreditation for on-site calibrations enables Kistler to traceably calibrate test systems for friction coefficient tests on bolted joints of up to 60 kNm in the measurand torque.

The achievable extended measurement uncertainty is 0.5%. Kistler Remscheid thus closes a gap in the field of accredited on-site calibrations.