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Residual stress profile determination by the hole-drilling method with calibration coefficients obtained using FEM

Corrêa Fábio Junkes, Jahnert Frederico Alves, Tomás Jucélio Pereira

Journal of Theoretical and Applied Mechanics

2021

Vol. 59 nr 4

661--673

Residual Stresses (RS) in mechanical components can be undesirable, and their accurate identification can prevent component damage. There are many semi-destructive methods for determination of RS. The hole-drilling method offers many advantages when compared to other methods due to its practicality, applicability to different materials, and low-cost execution. According to the American Society for Testing and Materials (ASTM) E837- -13a Standard, the RS are assumed to be constant at each depth level when employing the hole-drilling method. Thus, calibration coefficients are necessary to calculate stress values at each level using the relaxed strains measured on the component surface, as incremental drillings are performed. However, the coefficients provided by the Standard were obtained using a coarsely-discretized 2D finite element model. This work aims to find new calibration coefficients based on the linear elasticity theory and using the Finite Element Method (FEM) with a refined mesh. A numerical model consisting of linear tetrahedral finite elements was constructed to simulate the resulting strains, as unitary stresses are applied at each depth level of the component inner surface. Using this method, two matrices of calibration coefficients are obtained, one related to normal stresses, and another related to shear stresses. The results show that the RS obtained using the new coefficients presented a 3.9% relative average error compared to analytical values in the four experiments conducted, while the ASTM Standard coefficients resulted in a 9.7% relative average error.

Badania i analiza stanu technicznego ścian drewnianej konstrukcji zrębowej kościoła św. Jana Nepomucena we Wrocławiu

Nowak T., Bednarz Ł., Jasieńko J., Karolak A., Kiedrzyn J.

Wiadomości Konserwatorskie

2018

Nr 55

105--120

W artykule przedstawiono zarys historii obiektu drewnianego o konstrukcji zrębowej oraz krótki opis wykonanych prac budowlano-konserwatorskich. Zły stan techniczny obiektu przed remontem był skutkiem między innymi dwóch jego wcześniejszych przenosin. Ostatni transfer obiektu miał miejsce w 1913 roku do Wrocławia na Wystawę Stulecia. Przed wykonaniem remontu obiektu przeprowadzono badania stanu materiału ścian kościoła przy zastosowaniu metod nieniszczących lub quasi-nieniszczących, takich jak metoda oporu wiercenia oraz metoda fali sprężystej. W artykule zaprezentowano opis i wyniki przeprowadzonych badań oraz analizę stanu materiału drewnianych ścian obiektu.

The paper presents the history of a timber log frame building and a short description of the conservation and renovation work completed. The poor technical condition of the building prior to renovation work resulted, among other things, from two earlier relocations. The last relocation of the building was in 1913 when it was moved to the Centennial Exhibition in Wroclaw. Prior to renovation work, the condition of materials of the church walls was tested using non-destructive or quasi non-destructive methods, including resistance drilling and stress wave methods. A description and results of the testing, along with the analysis of the condition of the timber walls of the building, are presented in this paper.