Analys av gängor i slagborrning

Threaded joints in percussive drilling are subjected to extreme and repeated axial and torsional loads, playing a critical role in both structural integrity and energy transmission. This thesis presents a combined numerical and experimental investigation aimed at improving the understanding of wave propagation through such joints. A detailed 3D finite element model was developed for LS-DYNA solver using existing CAD model and dedicated meshing tools, incorporating realistic preload, contact and friction conditions to simulate stress wave behavior. To complement this, a 1D model was created in an open-source multi-domain system simulation tool called Hopsan for efficient analysis of impulse responses. Experimental tests using strain gauge sensors captured both axial and torsional wave transmission across a threaded joint under varying torsional preload. Simulation results were validated against these measurements, demonstrating good agreement in axial wave trends and highlighting the influence of preload and friction on energy loss and torsional wave behavior. Mesh refinement study confirmed that a coarser mesh in the threaded region was sufficient for accurate wave resolution. The combined modeling approach provided valuable insight of threaded joints, with the validated LS-DYNA model serving as a reliable tool for analyzing dynamic joint performance. The results highlight the importance of preload and friction in wave transmission efficiency, offering a deeper understanding that can support the optimization of joint design for improved performance and durability in percussive drilling applications.