C ristian Bagni

Hottinger Bruel & Kjaer UK Ltd, Rotherham, United Kingdom

Dr. Cristian Bagni holds a Master’s Degree in Civil and Structural Engineering (Unversità degli Studi di Parma, Italy) and a PhD in Structural Engineering (The University of Sheffield) developing a new Finite Element methodology to assess the static and fatigue behaviour of notched and cracked components. He has co-authored papers on Computational Mechanics and Fatigue, and he has reviewed papers for International Journals including ‘Fatigue & Fracture of Engineering Materials & Structures’ (FFEMS), and ‘Theoretical and Applied Fracture Mechanics’. After working for several years at the University of Sheffield’s Advanced Manufacturing Research Centre (AMRC) on high profile aerospace research projects, he also gained extensive experience on advanced manufacturing processes. Cristian joined Hottinger Brüel & Kjær in July 2020 as Technologist for Fatigue and Fracture, and amongst his activities he leads research on the fatigue behaviour of joints. He also supports the Advanced Materials Characterisation & Testing (AMCT) facility with the analysis and post-processing of fatigue test results, and consequent characterisation of both joints and parent materials.


The use of adhesives in structural joints as an alternative to traditional joining techniques, such as welding and rivets, is becoming increasingly popular in the transportation industry, including (but not limited to) automotive and aerospace. This trend is driven especially by the increasing need and focus on greener ways of transportation and the consequent light weighting requirements. Furthermore, adhesives have the significant advantage, over traditional joining techniques, of allowing joining of dissimilar materials, including composites. Therefore, to optimise the design of adhesively bonded structures and reduce the risk of in-service fatigue failures, the transportation industry needs efficient, robust, and easy-to-use approaches for the modelling and fatigue life estimation of adhesively bonded joints.

This work presents a practical methodology for estimating the fatigue life of adhesively bonded joints that can be easily adopted by companies in the transportation industry. The proposed methodology includes Finite Element (FE) modelling guidelines to recover the required stresses along the bond lines, with limited changes to the typical FE modelling strategies currently used, especially in the automotive industry. It is proposed to model the adherends using shell elements and the adhesive layer with solid elements. The exposed edges of the adhesive are then wrapped with membrane shell elements used to extract the peel stresses. The solid elements and the shell elements are connected using ‘bonded contacts’ (or similar tools, depending on the Finite Element software used). The proposed modelling guidelines provide FE models that are not computationally too onerous, with a good level of mesh insensitivity and that do not require congruent meshes. The peel stresses recovered from the FE model along the bond lines are then used as an input into nCode DesignLife to estimate the fatigue life of the bonded joints in the analysed structure. The fatigue life estimation is carried out using the standard nCode DesignLife SN analysis engine and bespoke SN curves obtained through testing of adhesively bonded specimens, representative of the joints in the production parts.


Poster Session00:00-00:00Cristian Bagni

106 - A pragmatic approach for the fatigue life estimation of hybrid joints
Room 9Thursday 30th November11:45-12:15Cristian Bagni
S09-4 Fatigue of assemblies
105 - A practical methodology for the fatigue life estimation of adhesive joints
Welcome to Booth.

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