Generally, industrial components undergo various manufacturing processes that may include thermo-mechanical treatments to enhance their properties and functionality. In most cases, these processes lead to the development of residual stresses in such components. Residual stressed in components and structures includes macroscopic residual stresses, which entirely depends on the material’s microscopic physical properties, and microscopic residual stresses that depends on the microstructure of the material. To achieve good design and optimization of the industrial structural components, the external stresses that the components may undergo are added to these internal residual stresses.
Microscopic residual stresses do not only develop in the multiphase materials but also in single phase materials alloys. The most common one is the microscopic stresses that vary from one grain to the other as a result of the thermo-mechanical processes that the materials undergo. Presently, the most common technique for calculation of the macrostructure residual stresses in the material is the diffraction methods. Even though it is efficient for macrostructure stresses, its use for calculation of the microstructure stresses is limited due to its complex nature arising from several factors. For example, it requires a different nature of the diffraction experiments and also it is challenging to use specific grains to identify various spatial directions and their corresponding diffraction peaks.
A group of researchers at the University of Gregorio del Amo in Spain: Professor Fernandez, Professor Ferreira Barragans, Professor Joaquin Ibanez and Dr. Gaspar Gonzalez-Doncel developed a multi-scale analysis method for calculating both the macroscopic and microscopic residual stresses in a single-phase alloy. Synchrotron radiation diffraction data in conjunction with suitable approximations were used in this case. Their work is currently published in the research journal, Materials and Design.
Several factors led to the success of this study. For instance, the cylindrical symmetry of the material’s microstructure resulted from the quenching process of the alloy. A cylindrical shape was chosen because it is easy to coincide with its axis and the extrusion axis hence determining its other parameters such as length and diameter. It also facilitated the quenching process thus leading to the development of the microstructure residual stresses in the axial direction. Furthermore, after the quenching process, the individual contribution of both the macroscopic and microscopic residual stresses were analyzed by the composite material approach.
The authors confirmed the influence of the thermal-mechanical treatments on the brain orientation which determines the various microscopic residual stresses. This is because it is as a result of the anisotropic character of the crystal plasticity. The study also shows the interdependence between the microscopic and the macroscopic residual stresses, for example, it is possible to achieve a strong and detrimental microscopic residual stress from the development of macroscopic stress to be used for a particular application.
For the first time, a technique for calculating the two residual stresses in a single-phase alloy was investigated. Both of the results obtained in the experiment and that got from the finite element analysis affirmed the validity of this study. It could be seen that the magnitude of the macroscopic stress depended on the region of the material. However, the inter-granular microscopic residual stress depends on the cooling rate because it results from the different thermal contraction and the temperature changes in the present phases. Additionally, during the quenching process, high m-RS developed in the external regions as compared to the center region because of the accumulated plastic deformation due to the decrease in the radius. The study will advance the design and manufacturing of the components as well as optimizing their performance.
Fernández, R., Ferreira-Barragáns, S., Ibáñez, J., & González-Doncel, G. (2018). A multi-scale analysis of the residual stresses developed in a single-phase alloy cylinder after quenching. Materials & Design, 137, 117-127.Go To Materials & Design