Banca de DEFESA: EMERSON DA TRINDADE MARCELINO

NUMERICAL SIMULATION OF THE MECHANICAL BEHAVIOR OF A WOL-MODIFIED SAMPLE USING TWO-DIMENSIONAL AND THREE-DIMENSIONAL MODELS BASED ON THE FINITE ELEMENT METHOD

Fracture; Modified-WOL specimen; Finite Element Method; Instrumented bolt.

This work demonstrates how the use of numerical models, which predict the mechanical behavior of a specimen, can contribute to the design and preparation of experimental mechanical tests. In this study, the Modified-WOL specimen was analyzed, which has an internal bolt and a reaction pin as loading devices. This specimen is used to evaluate the materials’ resistance to the propagation of cracks considering a tensile load and the type of environment that will be submitted in service. With just one test with this specimen, it is possible to obtain the value of the threshold Fracture Toughness for Environment-Assisted Cracking of the material. For this, it is necessary to measure directly the load applied to the specimen using an instrumented bolt. However, the hole needed to insert a strain gauge into this bolt can lead to a reduction in its mechanical strength. Due to the scarcity of works that use numerical tools to dimension tests with this type of specimen, this work aims to simulate the mechanical behavior of a Modified-WOL specimen during the initial loading with three- dimensional and two-dimensional models with the Finite Element Method, considering the axial hole in the bolt and the use of different types of steel in the bolt and pin to evaluate the mechanical response of the set: specimen, bolt, and pin. Mesh convergence studies were carried out to identify the most adequate mesh density for each model. Numerical simulations proved that the presence of the hole does not cause significant changes in the integrity of the bolt. Two parametric studies were also performed. The first considered different bolt turning rates to identify the one that produces a loading rate lower than the maximum limit established in the standard. The second considered different coefficients of friction in the contacts, which demonstrated that the absence of good lubrication will result in the evolution of a transverse component of the load, which may invalidate the test.