The student Jon Mendiola Ramos an EXCELLENT CUM LAUDE with mention INDUSTRIAL DOCTORATE

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The student Jon Mendiola Ramos an EXCELLENT CUM LAUDE with mention INDUSTRIAL DOCTORATE

THESIS

The student Jon Mendiola Ramos an EXCELLENT CUM LAUDE with mention INDUSTRIAL DOCTORATE

2025·12·05

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  • Thesis title: Metodología para la predicción del comportamiento a fatiga a alto número de ciclos (HCF) de uniones atornilladas de alta resistencia considerando las tensiones residuales y la capa plástica generada en el proceso de fabricación

Court:

  • Presidency: Miguel Muñiz Calvente (Universidad de Oviedo)
  • Vocal: Diego Infante García (Universidad Politécnica de Valencia)
  • Secretary: Miren Larrañaga Serna (Mondragon Unibertsitatea)

Abstract:

The increase in energy consumption in recent years, coupled with climatic change, has led to an unprecedented demand for renewable energy sources. Among these, wind energy production has experienced continuous growth, resulting in a rise in wind turbine power output and the need to extend the service life of existing installations. Consequently, understanding and assessing the structural integrity of components is essential, both in the design of new parts and in the maintenance of those already in operation.

One of the critical elements in wind turbine is bolted joints, which are responsible for securing the main components. A failure in these joints can lead to the collapse of the entire machine. Failures in bolts located in critical joints are typically caused by mechanical fatigue, which arises from the cyclic and transient loads experienced during service. The key factors influencing the fatigue life of bolts include the manufacturing process the tightening condition, and the operational loads.

The thesis presents a combined numerical and experimental methodology for estimating the service life of high strength bolts, taking into account both the manufacturing process and the loading conditions during operation. The main contributions of this work are as follows:

  • Development and validation of a numerical-experimental methodology to predict both residual stresses and the plastic strain layer generated during the manufacturing process of high strength bolts. This methodology enables the evaluation of the effects of thread cold rolling and surface coating processes on residual stresses and plastic strain layer.
  • Development of several numerical methodologies for estimating the high cycle fatigue life of high strength bolts. The comparison of these methodologies has made it possible to quantify the impact of the manufacturing process on bolt fatigue life. These methodologies have been validated through experimental fatigue testing.