Neutron diffraction and finite element modeling to study the weld residual stress relaxation induced by cutting

• Stress relaxation by cutting is studied by neutron diffraction and simulation.
• It is correlated to the cutting length exponentially based on St. Venant’s principle.
• The critical length to avoid relaxation is proposed as 0.3 of the initial length.

Temperature and residual stresses were thermo-mechanically modeled in a 1000 mm long welding plate based on the simplified variable length heat source. The stress relaxations were simulated as a function of the plate length after cutting the initial weld specimen by using an element removal method and treating the prior stress field as the next cutting origins. Meanwhile residual stresses were sequentially measured in a weld with the length of 300 mm and cut welds having 150, 10 mm lengths for comparison using neutron diffraction. Residual stresses from both the modeling and experimental results exponentially decrease from about 370 to 0 MPa as the total weld plate length decreases from 300 mm to 10 mm. Such stress relaxation by the cutting length is correlated to the exponential decrease law based on the St. Venant’s principle. It suggests that the minimum cutting length about 300 mm is necessary to prevent the stress relaxation less than 3% of the initial stresses in a high-strength steel weld.