In this work, we propose a new four-node shell element (called BKWH24) with six degrees of freedom per node based on the first-order shell theory of Reissner-Naghdi. The element is valid for thin to thick shells, taking into account membrane, bending, and transverse shear effects with strain components explicitly linear in the thickness coordinate. The BKWH24 shell element is based on the generalisation of the plate-bending BKWA element regarding the approximations of displacements, rotations, and shear strains. The paper presents results for several classical benchmarks for shells and proposes new benchmarks to demonstrate the influence of transverse shear effects in thick shells.
Exceptional points (EPs) correspond to specific values of the system parameters that yield defective eigenvalues. The concept is demonstrated experimentally in the case of a simple mechanical system consisting of two coupled linearized pendulums. The latter is designed and instrumented in order to allow the encircling of an EP: the modulation of both the mass and stiffness matrices is achieved by controlling the length of one pendulum, whereas the damping is controlled by using eddy current brake mechanisms. The time evolution of the state vector, identified with the help of the extended Kalman filter, is described using the instantaneous modal basis. This allows one to quantify and observe mode coupling mechanisms, non-adiabatic effects and chiral behaviour. The paper ends with a numerical study, via the analysis of the monodromy matrix and the multiple-scale approach, which illustrates both the effect on chirality of the period of encircling and the presence of an EP in the loop.
Maintenance strategies have traditionally been designed with a primary focus on cost reduction and operational efficiency, often overlooking their broader environmental and social impacts. However, in the current context where industries must align with European carbon neutrality 2050 objectives and the United Nations Sustainable Development Goals (SDGs), maintenance is recognized as a key lever for enhancing the three pillars of sustainability in industries: economic, social, and environmental. In addition, recent studies have shown that the ongoing digital transformation of industry through Industry 4.0 technologies such as artificial intelligence, Internet of Things, digital twins, and big data analytics, offers new opportunities to improve maintenance strategies. These developments have given rise to the concept of Maintenance 4.0, which opens new perspectives for aligning maintenance practices with broader sustainability objectives.To better understand the impact of these technologies on maintenance sustainability, as well as the existing assessment initiatives in the current state of research, this paper conducts a systematic literature review (SLR). A total of 31 relevant studies were analyzed and classified into literature reviews, conceptual frameworks, and evaluation models. The review reveals that while economic and environmental benefits are increasingly supported by measurable indicators, the social dimension remains underexplored and lacks standardized metrics. In addition, most studies focus on short-term operational gains and do not address life cycle-wide perspective, including manufacturing and end-of-life stages.Based on these findings, this paper (i) clarifies the current maturity of research and its exploratory nature; (ii) identifies major gaps which is the lack of lifecycle-based assessments and operational social indicators; (iii) highlights the weak operationalization of circular economy principles in maintenance 4.0 strategies; and (iv) proposes future research directions to develop holistic, life cycle-oriented, human-centric, and practically validated frameworks. These contributions aim to support the transition toward more sustainable maintenance practices, in alignment with sustainability goals.
Eigenmodes remain a recurring concept in several branches of physics for the analysis of dynamical systems.As long as they are Hermitian, they satisfy standard orthogonal properties.This is no longer true when gains and/or losses are taken into account.For specific values of some parameters, eigenvalues as well as their associated eigenvectors can coalesce because of the existence of an exceptional point (EP).These EPs have gained much interest in recent years because of the counter-intuitive concepts associated with them, like strong attenuation or mode switching phenomenon.In the fields of acoustics and vibration, EP control may lead to a better understanding of energy exchanges and dissipation between modes.These aspects are also integral elements of metamaterials, since their design is based on resonators and their coupling.This work aims at exploring the key concepts related to EPs by revisiting the well-known coupled pendulums problem in the presence of damping.First, the free response of the experimental system is investigated after tuning it on an EP.Then an encircling is performed by varying the parameters through time.Experimental results allow us to observe nearly-optimal dissipation, energy ex-
