Experimental determination of the tightening coefficient of bolts according to the din standard

The use of slip-critical connections is very common in the design critical steel structures and seen as an effective way to transfer force conditions dynamic loading. limit state connection occurs when calculated shear stress reached, which depends on friction coefficient contact planes value clamping force, equal bolt tension stress. In order ensure necessary tensioning it know tightening coefficient, because according current understanding performance, designed functioning ensured arising at torque achieved. Otherwise, actual work will be different from calculated, only a given provides estimated bearing capacity bolted with planes. This article focuses tensile testing determining factor made high-strength10.9 M14 steel. determined strain gauges by measuring relative nut tightened. method requires specialized equipment test bench can used study performance absence certificate or need verify clarify available data. results show that proposed provide stable determination value. examined bolts were German standard DIN931, strength 10.9 size M14x220, nuts DIN934, 10 M14. An Instron 1000HDX machine was plot Nut control NOGRAU NTW24-034R wrench, elongation FLA 5-11 National Instruments data acquisition system. On basis conducted research, for high-strength has been tested proposed. research allows determine appropriate (verify) stated coefficient.