**Coupling Finite Element Analysis and the Theory of Critical Distances to Estimate Critical Loads in Al6060-T66 Tubular Beams Containing Notches**

### **Marcos Sánchez, Sergio Cicero \*, Borja Arroyo and José Alberto Álvarez**

LADICIM (Laboratory of Materials Science and Engineering), University of Cantabria, E.T.S. de Ingenieros de Caminos, Canales y Puertos, Av/Los Castros 44, 39005 Santander, Spain; marcos.sanchez@unican.es (M.S.); borja.arroyo@unican.es (B.A.); alvareja@unican.es (J.A. Á.)

**\*** Correspondence: ciceros@unican.es; Tel.: 0034-942-200917

Received: 29 September 2020; Accepted: 17 October 2020; Published: 20 October 2020

**Abstract:** This paper validates a methodology for the estimation of critical loads in tubular beams containing notch-type defects. The methodology is particularized for the case of Al6060-T66 tubular cantilever beams containing U-shaped notches. It consists in obtaining the stress field at the notch tip using finite element analysis (FEA) and the subsequent application of the theory of critical distances (TCD) to derive the corresponding critical load (or load-bearing capacity). The results demonstrate that this methodology provides satisfactory predictions of fracture loads.

**Keywords:** critical load; fracture; tubular cantilever beam; U-notch; theory of critical distances
