This study evaluates the consequences of modelling a weld-generated Heat Affected Zone when optimizing lightweight steel structures for crashworthiness. A case study on the resistance of an X-core sandwich panel is presented using a Particle Swarm Optimization-algorithm to search the design space for optimal solutions. Structures are developed by procedures including- and excluding a HAZ effect and later compared. The developed structures show distinct differences in terms of geometry, energy absorbed per unit mass, failure mode and sensitivity to HAZ material properties. Highlighting the importance of a proper set up for structural optimization, these findings question the validity of omitting weld effects when optimizing for crashworthiness.


The efficiency with which a hull structure may absorb kinetic energy without catastrophic consequences is, from the perspective of structural design, one of the main safety concerns for the shipbuilding industry. Generally, this necessitates exploring system characteristics to increase the tolerance for impact loading whilst preserving commercial competitiveness. The increased computational resources made available has in recent years enabled this exploration to be performed using metaheuristic optimization algorithms together with numerical simulations based on non-linear finite elements.

The low weight-to-stiffness ratio of the all-steel sandwich panel makes it a key structural component for the future of sustainable shipping. To be a viable option however, efficiency is needed, not only in ultimate- and fatigue limit states, but also under load cases associated with accidental scenarios. In reference to marine technology, the concept of crashworthiness is generally defined as an ability to absorb energy without hull breach. As the basis for a crashworthy sandwich panel, several novel structures have been suggested (Klanac, Ehlers, Tabri, Rudan, & Broekhuijsen, 2005). Most extensively researched among these are the X- and Y-core which are deemed to be the most suitable candidates to date (see e.g. (Kõrgesaar, Jelovica, Romanoff, & Kurmiste, 2014), (Ehlers, Tabri, Romanoff, & Varsta, 2012), (St-Pierre, Deshpande, & Fleck, 2015), (Rubino, Deshpande, & Fleck, 2008)).

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