My first subject of research was cold pressure welding. Microscopic studies of the weld formation led to establishment of a theoretical model for bond formation based on continuum mechanics, and a new surface preparation method introducing brittle surface layers by chemical Ni-plating. In parallel to this work, I studied fundamentals of friction in metal forming. Together with Wanheim a theoretical model for friction was proposed based on slipline analysis of the flattening of surface asperities. The model was later improved including subsurface deformation using finite element analysis. The increasing focus on environmental aspects of lubrication in sheet metal forming tribologically difficult materials such as stainless steel motivated research on development and testing of environmental friendly lubricants and tribo-systems preventing galling. A universal sheet tribo-tester was developed, which can carry out consecutive tests at controlled sliding length, sliding speed and idle time between tests in order to emulate production conditions. The work resulted in the introduction of new, environmentally benign lubricants, new tool coatings diminishing the risk of galling and tailored tool surfaces facilitating micro-plasto-hydrodynamic lubrication, which prevents galling. The work on strategic surface coatings promoting bond formation in cold pressure welding was continued in work on resistance projection welding of dissimilar metals. Development of an FEM program for resistance welding was initiated in the 1990-ies resulting in the formation of a Danish spin-off company SWANTEC commercializing and further developing the program, which today is state-of-the art and applied by a large part of automotive industry and steel mills in the world.