Seyed Rasoul Atashipour

This paper proposes an innovative approach to identify elastic material properties and mass density of soft tissues based on interpreting their mechanical vibration response, externally excited by a mechanical indenter or acoustic waves. A vibration test is performed on soft sheets to measure their response to a continuous range of excitation frequencies. The frequency responses are collected with a pair of high-speed cameras in conjunction with 3-D digital image correlation (DIC). Two cases are considered, including suspended/fully-free rectangular neoprene sheets as artificial tissue cutout samples and continuous layered human skin vibrations. An efficient theoretical model is developed to analytically simulate the free vibrations of the neoprene artificial sheet samples as well as the continuous layered human skins. The high accuracy and validity of the presented analytical simulations are demonstrated through comparison with the DIC measurements and the conducted frequency tests, as well as a number of finite element (FE) modeling. The developed analytical approach is implemented into a numerical algorithm to perform an inverse calculation of the soft sheets' elastic properties using the imported experimental vibration results and the predicted system's mass via the system equivalent reduction/expansion process (SEREP) method. It is shown that the proposed frequency-dependent inverse approach is capable of rapidly predicting the material properties of the tested samples with high accuracy.

Laser-welding technology has recently enabled the production of corrugated-core steel sandwich panels (CCSSPs) as an innovative large-scale, lightweight structural solution in maritime and infrastructure applications. Detailed numerical analyses, specifically weld-region stress prediction in the presence of transverse patch loading and supports, are computationally challenging and time-consuming for their optimal design. This paper introduces an efficient, simplified combined sub-modelling approach for accurately predicting the detailed structural response of welded corrugated-core steel panels. The approach rests on the homogenisation of the three-dimensional (3D) panel into a two-dimensional equivalent orthotropic single layer (EOSL), where the effect of transverse compressive loads and local support conditions are captured separately via different 2D and 3D sub-modelling techniques, together with a model introduced for calculation of the weld region’s equivalent spring stiffnesses. A laser-welded corrugated-core steel sandwich panel (CCSSP), as a future generation of the steel bridge deck, was examined using different modelling approaches. It was shown that the proposed combined sub-modelling approach can accurately predict stresses and displacements in all the constituent members of the cross-section, including the welds, in a reasonable calculation time when compared with a 3D reference model, unlike the conventional homogenisation approaches.

The publication of this article unfortunately contained a mistake. Table 8 of Appendix B was not correct; please see the updated table below.

Adhesive joints have been known and used in different applications within the area of structural and mechanical engineering for decades. Hybrid joints with glued-in rods are nowadays increasingly used as an efficient way for both constructing new and strengthening/repair of existing timber structures. However, despite ongoing research since the 1980s, general and reliable design criteria for such connections are missing in the European standard for timber structures, Eurocode 5, and there is contradiction between the load bearing capacity predicted by different existing design models. In this study, the adhesive bond-layer failure, as the dominant failure mode in GiR connections, is simulated for single- steel rod joints based on the nonlinear fracture mechanics (NLFM) approach using Abaqus software. A finite element (FE) model, describing timber-adhesive interface failure, is established, calibrated as well as verified through comparison with existing test results reported in literature. The simulations are conducted for two different types of adhesives namely epoxy (EPX) and polyurethane (PUR). The single- GiR joints are loaded in axial tension and progressive failure is simulated to accurately predict the maximum load bearing capacity of the joints due the pull-out failure, in the timber-to-rod adhesive bond layer. A parameter study is conducted and the influence of some geometrical dimensions and material property parameters on the pull-out capacity of single-rod connections is investigated. It is shown that simplified axisymmetric models can also accurately describe the behaviour of single GiR connections when compared with a more realistic 3-D model, with significantly less processing time and computational effort.