Experimental and Numerical Peeling Investigation on Aged Multi-Layer Anti-Shatter Safety Films (ASFs) for Structural Glass Retrofit

Anti-shatter safety films (ASFs) are often used for structural glass applications. The goal is to improve the response of monolithic elements and prevent fragments from shattering. Thus, the main reason behind their use is the possibility to upgrade safety levels against the brittle failure of glass and minimize the number of possible injuries. However, the impact response of glass elements bonded with Polyethylene terephthalate (PET)-films and pressure sensitive adhesives (PSAs) still represents a research topic of open discussion. Major challenges derive from material characterization and asymmetrical variability under design loads and ageing. In particular, the measurement of interface mechanical characteristics for the adhesive layer in contact with glass is a primary parameter for the ASF choice optimization. For this reason, the present paper presents an experimental campaign aimed at calibrating some basic mechanical parameters that provide the characterization of constitutive models, such as tensile properties (yielding stress and Young modulus) for PET-film and adhesive properties for PSA (energy fracture and peel force). In doing so, both tensile tests for PET-films and peeling specimens are taken into account for a commercially available ASF, given that the peeling test protocol is one of most common methods for the definition of adhesion properties. Moreover, an extensive calibration of the Finite Element (FE) model is performed in order to conduct a parametric numerical analysis of ASF bonded glass solutions. Furthermore, a Kinloch approach typically used to determine the fracture energy of a given tape by considering a variable peel angle, is also adopted to compare the outcomes of calibration analyses and FE investigations on the tested specimens. Finally, a study of the effect of multiple aspects is also presented. The results of the experimental program and the following considerations confirm the rate dependence and ageing dependence in peel tests.

Experimental Analysis and Multiscale Modeling of the Dynamics of a Fiber-Optic Coil

Fiber-optic gyroscopes (FOGs) are common rotation measurement devices in aerospace applications. They have a wide range of diversity in length and in the winding radius of the coil to meet system requirements. Every dimensional parameter in the coil influences the dynamic response of the system, eventually leading to measurement errors. In order to eliminate the errors and to qualify the system, after the design and production stages, a deep and comprehensive testing procedure follows. In this study, the dynamic behavior of a quadrupole wound fiber-optic coil is investigated. First, pre-wound fiber-optic coils are tested with an impact modal test, where the mode shapes and natural frequencies are determined with structural data acquisition. For the modal analysis, a finite element (FE) model is developed where a representative volume element (RVE) analysis is also included to properly consider the influence of the microstructure. The experimental and numerical results are compared and validated. Moreover, an estimation model is proposed for a type of coil with different fiber lengths. Finally, the estimated coil set is produced and tested employing the same methodology in order to illustrate the capacity of the developed framework.

Analysis of exterior beam-column joints under varying column axial load and code comparisons

This paper presents a finite element (FE) study of beam-column joints subjected to cyclic loading. This study is primarily dependent on investigating the shear behavior of joints under the influence of different column axial load ratios. Wherefore, a total range of the column axial load ratios, whether in tension or compression has been considered. This paper proposes a two-dimensional (2D) FE model that considers material non-linearity. The proposed FE model was verified with experimental results from literature that tested varying column axial load ratios and different failure modes. The examination among experiential and numerical outcomes demonstrated that the FE model can reenact the conduct of beam-column joints and can catch the different failure modes with acceptable accuracy. A parametric study was established using the proposed FE model and strut-and-tie (ST) model of Pauletta to assess the Eurocode joint shear strength equations. For this purpose, four specimens were designed according to Eurocode recommendations while two other specimens were designed to satisfy all of the Eurocode recommendations except for the required joint confinement. An interaction diagram was introduced for each specimen to express the behavior under varying column axial load ratios. The results of the comparison between Eurocode, FE model, and ST model showed some differences in calculating the joint shear strength capacity, especially under column tension loads. Furthermore, this paper proposed new design equations based on Eurocode equations taking into account the column axial load effect. These proposed equations worked to increase the accuracy in calculating the joint shear strength capacity. Proposed equations were compared to the FE model results and other experimental results available in the literature. The comparison showed that the differences with the FE model decreased and that the proposed equations had better accuracy at different tension and compression loads than the Eurocode.

Optimization of the Curved Metal Damper to Improve Structural Energy Dissipation Capacity

Structural curved metal dampers are implemented in various applications to mitigate the damages at a specific area efficiently. A stable and saturated hysteretic behavior for the in-plane direction is dependent on the shape of a curved-shaped damper. However, it has been experimentally shown that the hysteretic behavior in the conventional curved-shaped damper is unstable, mainly as a result of bi-directional deformations. Therefore, it is necessary to conduct shape optimization for curved dampers to enhance their hysteretic behavior and energy dissipation capability. In this study, the finite element (FE) model built in ABAQUS, is utilized to obtain optimal shape for the curved-shaped damper. The effectiveness of the model is checked by comparisons of the FE model and experimental results. The parameters for the optimization include the curved length and shape of the damper, and the improved approach is conducted by investigating the curved sections. In addition, the design parameters are represented by B-spline curves (to ensure enhanced system performance), regression analysis is implemented to derive optimization formulations considering energy dissipation, constitutive material model, and cumulative plastic strain. Results determine that the energy dissipation capacity of the curved steel damper could be improved by 32% using shape optimization techniques compared to the conventional dampers. Ultimately, the study proposes simple optimal shapes for further implementations in practical designs.

Cohesive Zone Model Modification Techniques According to the Mesh Size in Finite Element Models of Stiffened Panels with Debonding

When catastrophic failure phenomena in aircraft structures, such as debonding, are numerically analyzed during their design process in the frame of “Damage Tolerance” philosophy, extreme requirements in terms of time and computational resources arise. Here, a decrease in these requirements is achieved by developing a numerical model that efficiently treats the debonding phenomena that occur due to the buckling behavior of composite stiffened panels under compressive loads. The Finite Element (FE) models developed in the ANSYS© software (Canonsburg, PA, USA) are calibrated and validated by using published experimental and numerical results of single-stringer compression specimens (SSCS). Different model features, such as the type of the element used (solid and solid shell) and Cohesive Zone Modeling (CZM) parameters are examined for their impact on the efficiency of the model regarding the accuracy versus computational cost. It is proved that a significant reduction in computational time is achieved, and the accuracy is not compromised when the proposed FE model is adopted. The outcome of the present work leads to guidelines for the development of FE models of stiffened panels, accurately predicting the buckling and post-buckling behavior leading to debonding phenomena, with minimized computational and time cost. The methodology is proved to be a tool for the generation of a universal parametric numerical model for the analysis of debonding phenomena of any stiffened panel configuration by modifying the corresponding geometric, material and damage properties.

Sustainable Manufacturing of Ultra-Fine Aluminium Alloy 6101 Wires Using Controlled High Levels of Mechanical Strain And Finite Element Modeling

The evolution of grain size and component mechanical behaviour are fundamental aspects to analyse and control when manufacturing processes are considered. In this context, severe plastic deformation (SPD) processes, in which a high shear strain is imposed on the material, are recognized as the main techniques to achieve microstructural changes and material strengthening by the recrystallization, attracting both academic and industrial investigation activities. At the same time, nowadays, sustainable manufacturing design is one of the main responsibilities of the researchers looking at UN2030 agenda and the modern industrial paradigms. In this paper a new severe SPD process is proposed with the aim to steer manufacturing to fourth industrial revolution using some of Industry 4.0 pillars. In particular, additive manufacturing (AM) and numerical simulations were setup as controlling and monitoring techniques in manufacturing process of wires.Strengthening effect (yield and ultimate tensile strength, plasticity and hardness) and microstructural evolution (continuous dynamic recrystallization -CDRX-) due to severe plastic deformation were experimentally analysed and numerically investigated by an innovative finite element (FE) model able to validate the effectiveness of a properly modified process for ultra-fine aluminium alloy AA6101 wires production designed with the aim to avoid any post manufacturing costly thermal treatment.The study provides an accurate experimental study and numerical prediction of the thermo-mechanical and microstructural phenomena that occur during an advanced large plastic deformation process; it shows how the combination of smart manufacturing and simulations control represents the key to renew the traditional manufacturing methods in the perspective of the Industry 4.0, connecting and integrating the manufacturing process for the industrial evolution in production.

PREPARATION AND NUMERICAL SIMULATIONS OF DRUG-LOADED HYDROXYAPATITE BIOMATERIALS

To meet the challenge of regenerating bone lost to disease or trauma, biodegradable scaffolds are being investigated as a way to regenerate bone without the need for an auto- or allograft. Herein, we prepared poly (lactic acid) (PLA)/chitosan(CS)/nano-hydroxyapatite biomaterials through solution polymerization and solvent volatilization. Cefadroxil was used as a model drug for loading on biomaterials using supercritical carbon dioxide. In addition, we investigated the in vitro drug release effect, and the in vitro release results showed that the drug could release more than 73% of the drug load within 48[Formula: see text]h. This excellent drug release property could allow continuous drug use at the wound site, further broadening its application in the medical field. A three-dimensional finite element (FE) model of bone screws was established, and the mechanical properties of the screws were numerically calculated. The stress and deformation of the bone screws under different external conditions were simulated. The bending simulation showed that the screw can withstand the maximum deformation of 0.418[Formula: see text]mm and equivalent stress of 566.94[Formula: see text]MPa at a force of 700 N. The maximum equivalent stress of the screw reached 321.84[Formula: see text]MPa, and the corresponding torque was 779.68 N[Formula: see text]mm when the torsion angle was gradually increased to 30[Formula: see text]. The fabricated material has excellent mechanical properties and can be used for bone repair. This study provides a new direction for preparing drug-loaded polymer biomaterials and developing new materials for bone repair.

Finite-Element Modelling of Double-Roller Clamping Spinning of Wind Concentrator

In order to improve the unit-power of a wind-driven generator, a wind concentrator with complex shape is installed in front of the impeller, which makes the airflow integrated and accelerated. It is important to manufacture the wind concentrator with high precision. The double-roller clamping spinning (DRCS) is a dieless, flexible spinning process that is very suitable for forming a wind concentrator with complex shape. The profile of a wind concentrator is divided into two parts: the contraction section and the expanding section. The process routes of both the contraction section and the expanding section are determined, and roller path equations are derived. Then the finite element (FE) analysis model that can describe the plastic deformation behavior of the DRCS forming for a wind concentrator is established, and the DRCS process of the flange is simulated. Furthermore, the wall-thickness distribution on the expanding section during the forming process is obtained. Finally, the reliability of the FE model is verified using the experimental results.

Latest Advances in Finite Element Modelling and Model Updating of Cable-Stayed Bridges

As important links in the transport infrastructure system, cable-stayed bridges are among the most popular candidates for implementing structural health monitoring (SHM) technology. The primary aim of SHM for these bridges is to ensure their structural integrity and satisfactory performance by monitoring their behaviour over time. Finite element (FE) model updating is a well-recognised approach for SHM purposes, as an accurate model serves as a baseline reference for damage detection and long-term monitoring efforts. One of the many challenges is the development of the initial FE model that can accurately reflect the dynamic characteristics and the overall behaviour of a bridge. Given the size, slenderness, use of long cables, and high levels of structural redundancy, precise initial models of long-span cable-stayed bridges are desirable to better facilitate the model updating process and to improve the accuracy of the final updated model. To date, very few studies offer in-depth discussions on the modelling approaches for cable-stayed bridges and the methods used for model updating. As such, this article presents the latest advances in finite element modelling and model updating methods that have been widely adopted for cable-stayed bridges, through a critical literature review of existing research work. An overview of current SHM research is presented first, followed by a comprehensive review of finite element modelling of cable-stayed bridges, including modelling approaches of the deck girder and cables. A general overview of model updating methods is then given before reviewing the model updating applications to cable-stayed bridges. Finally, an evaluation of all available methods and assessment for future research outlook are presented to summarise the research achievements and current limitations in this field.

Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study

Revision surgery (RS) is a necessary surgical intervention in clinical practice to treat spinal instrumentation–related symptomatic complications. Three constructs with different configurations have been applied in RS. One distinguishing characteristic of these configurations is that the revision rods connecting previous segments and revision segments are placed alongside, outside, or inside the previous rods at the level of facetectomy. Whether the position of the revision rod could generate mechanical disparities in revision constructs is unknown. The objective of this study was to assess the influence of the revision rod position on the construct after RS. A validated spinal finite element (FE) model was developed to simulate RS after previous instrumented fusion using a modified dual-rod construct (DRCm), satellite-rod construct (SRC), and cortical bone trajectory construct (CBTC). Thereafter, maximum von Mises stress (VMS) on the annulus fibrosus and cages and the ligament force of the interspinous ligament, supraspinous ligament, and ligamentum flavum under a pure moment load and a follower load in six directions were applied to assess the influence of the revision rod position on the revision construct. An approximately identical overall reducing tendency of VMS was observed among the three constructs. The changing tendency of the maximum VMS on the cages placed at L4-L5 was nearly equal among the three constructs. However, the changing tendency of the maximum VMS on the cage placed at L2-L3 was notable, especially in the CBTC under right bending and left axial rotation. The overall changing tendency of the ligament force in the DRCm, SRC, and CBTC was also approximately equal, while the ligament force of the CBTC was found to be significantly greater than that of the DRCm and SRC at L1-L2. The results indicated that the stiffness associated with the CBTC might be lower than that associated with the DRCm and SRC in RS. The results of the present study indicated that the DRCm, SRC, and CBTC could provide sufficient stabilization in RS. The CBTC was a less rigid construct. Rather than the revision rod position, the method of constructing spinal instrumentation played a role in influencing the biomechanics of revision.