Strain Rate Sensitivity of Low Carbon Threaded Steel Rods of Grade 4.6

Bolt connections are widely used in construction and engineering to securely join structural elements. These connections are essential for distributing loads across components and ensuring that structures can withstand external forces. The planned failure of these bolts is of great importance in steel safety barriers (SSBs), as it can directly influence the height of the guardrail and the working width of the SSB during the vehicle impact, which consequently affects the crash consequences. Therefore, it is of great importance to determine the bolt response until fractures under different strain rates. For that purpose, experimental tensile tests of low-strength steel rods of grade 4.6 were conducted at various strain rates (0.0025-25 s^-1) until fracture. Test specimens were photographed during the testing, and by means of image processing, input data for calculation of true stresses and strains up to the point of fracture were extracted. Based on the experimental data, material parameters were determined for the Cowper-Symonds model, enabling precise numerical simulations of these connections at various strain rates. A validation study was also performed successfully.