Abstract
Tensile uniaxial test is typically used to determine the strength and plasticity of a material. Nominal (engineering) stress-strain relationship is suitable for determining properties when elastic strain dominates (e.g., yield strength, Young’s modulus). For loading conditions where plastic deformation is significant (in front of a crack tip or in a neck), the use of true stress and strain values and the relationship between them are required. Under these conditions, the dependence between the true values of stresses and strains should be treated as a characteristic—a constitutive relationship of the material. This article presents several methodologies to develop a constitutive relationship for S355 steel from tensile test data. The constitutive relationship developed was incorporated into a finite element analysis of the tension test and verified with the measured tensile test data. The method of the constitutive relationship defining takes into account the impact of high plastic strain, the triaxiality stress factor, Lode coefficient, and material weakness due to the formation of microvoids, which leads to obtained correctly results by FEM (finite elements method) calculation. The different variants of constitutive relationships were applied to the FEM loading simulation of the three-point bending SENB (single edge notched bend) specimen to evaluate their applicability to the calculation of mechanical fields in the presence of a crack.
Highlights
The most fundamental test performed to define strength characteristics and plasticity of the material is a uniaxial tensile test
The currently applied methods of strength analysis are developed based on the assumption that in the material there is a linear-elastic relationship between stress and stress (σ = Eε), and the yield strength is a quantity that limits the scope of applicability of this linear relationship (σ ≤ σYS )
Methods for establishing the true stress-strain relationships based on the iterative adjustment are in use. In this approach is believed that the relationship is true when the numerically calculated load curve of the specimen is compatible with the diagram obtained during the uniaxial tensile test [8,9,10,11,12]
Summary
The most fundamental test performed to define strength characteristics and plasticity of the material is a uniaxial tensile test. The size of the plastic zone significantly exceeds the one permissible as specified in the requirements of linear fracture mechanics In this situation, while performing strength analysis, it is essential to apply the model of the non-linear material and defined the relationship between true stress and strain values. To determine stress and strain in the minimum cross-section of the neck and, based on their basis, define a relationship of true stress-strain, different methods were developed and proposed. Methods for establishing the true stress-strain relationships based on the iterative adjustment are in use In this approach is believed that the relationship is true when the numerically calculated load curve of the specimen is compatible with the diagram obtained during the uniaxial tensile test [8,9,10,11,12]. Modeling and calculation of stress and strain fields at loading specimen containing crack (SENB) were performed for verification of the constitutive relations correctness
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
