The Possibilities of Evaluating the Yield Strength in the Heat Affected Zones of a Weld through Indentation

Abstract

The research focuses on elastic-plastic behaviour of welded joints of materials which are commonly used in both constructional practice and the automotive industry. The examined welded joints are oriented to a common constructional S355 and a modern high-strength steel DOMEX 700MC.The main tool for the assessment of the elastic-plastic response was the methodology based on the instrumented penetration testing with the use of a cylindrical indenter. The indentation tool was applied into narrow zones of welded boundaries. These zones represent critical areas of welded constructions because of a changing structure and different mechanical properties than the basic material possesses. The indentation data were recalculated to the mechanical properties in shear with the help of Hencky ́s hypotheses about material behaviour. The correctness of the used methodology was verified by a tensile test. The aim of the work is to determine optimal methods for defining a yield strength and to find a hardening trend in the zones. The comparison of these steels revealed different changes due to the welding process. A substantial decrease of the yield strength of Domex700MC was observed, as a contrary to a stable, or partially increased, yield strength of the S355 steel. Structural analyses revealed a different material response of the evaluated steels, according to a different hardness in the heat affected zone.

Fatigue strength degradation of thermomechanically rolled high strength steels welds

“…The indentation yield stress is determined using the analytical definition of shear deformation under the contact surface, according to Hencky's hypothesis [13,14]. The standard tensile test in the longitudinal and perpendicular orientation of the uninfluenced hollow-section part served as a final validation.…”

Deformation Response of Dual Phase Steel in Static and Dynamic Conditions

“…The Hencky theory for plane strain indentation slip is used to calculate the real yield strength. The ratio of indentation yield strength to normal yield strength is 2.57 according to Hencky equations for the plane strain indentation [7,8]. Pressure relative to shear yield stress is Pindent/2k = 2.57.…”

Strength and Fracture Behaviour of Dual Phase Steel Dp450 in Static and Dynamic Conditions

“…To find out the better distribution of plastic deformation and residual hardening effect of the fracture, the macroindentation technique is used to determine the local yield strength with 0.5 mm diameter cylindrical indenter. Based on the elastic-plastic transition of the curve in the forcedepth graph, the yield strength is calculated [6].…”