Micro-EDXRF, SEM-EDS and OM characterisation of tin soldering found in handle attachments of Roman situlae from Conimbriga (Portugal)

Tin (Sn) or a Sn-rich solder applied to copper-based artefacts has been frequently used at least, since the Ancient Greece, although scarce studies have been published concerning the technology of this metallurgical joining technique. Several filler remnants were reported to be found in a Roman collection of handle attachments of situlae or cauldrons (2nd century BCE–5th century CE) from the archaeological site of Conimbriga, a Roman city from the Lusitania Province (Portugal). All these artefacts were cast in high leaded coppers and bronzes. The present study aims to contribute to the knowledge of Sn-rich soldering, an ancientmetallurgical joining technique, by the characterisation of the fusible metallic alloy present in 10 Roman artefacts by means of micro-energy dispersive X-ray fluorescence spectrometry (micro-EDXRF), scanning electron microscopy with energy dispersive X-ray (SEM-EDS) microanalysis and optical microscope (OM) observations. Results of studied solders show the presence of Cu-Sn alloys, with Sn contents ranging from δ to η phase composition (30–60wt% Sn). As the attachments were made in leaded copper alloys, it was also observed, in some cases, the melting of the interdendritic Pb-rich chains with long-range diffusion of the solder alloy into the substrate. The fillers compositions suggest that the handle attachments have been joined to a situla body by the soldering metallurgical process with Sn or a Sn-rich alloy. The studied leaded Cu-Sn attachments, probably formulated by local craftsman, were joined into the body of a situla or cauldron with a soft solder (soldering), a common metallurgical joint from Antiquity, although no relation was found between composition or typology and the Sn or Sn-rich solder

Effect of material, geometry, surface treatment and environment on the shear strength of single lap joints

The single lap joint is the most studied type of adhesive joint in the literature. However, the joint strength prediction of such joints is still a controversial issue as it involves a lot of factors that are difficult to quantify such as the overlap length, the yielding of the adherend, the plasticity of the adhesive and the bondline thickness. The most complicated case is that where the adhesive is brittle and the overlap long. In any case, there is still a problem that is even more difficult to take into account which is the durability. There is a lack of experimental data and design criteria when the joint is subjected to high, low or variable temperature and/or humidity. The objective of this work is to carry out and quantify the various variables affecting the strength of single lap joints in long term, especially the effect of the surface preparation. The Taguchi method is used to decrease the number of experimental tests. The effect of material, geometry, surface treatment and environment is studied and it is shown that the main effect is that of the overlap length. In order to quantify the influence of the adhesive (toughness and thickness), the adherend (yield strength and thickness), the overlap, the test speed, the surface preparation and durability on the lap shear strength, the experimental design technique of Taguchi was used in the present study. An experimental matrix of eighteen tests was designed and each test was repeated three times. The influence of the eight previously-mentioned variables could be assessed using the statistical software Statview®. In this paper a simple predictive equation is proposed for the design of single lap joints

Combined effect of seawater and load on methacrylate adhesive

[Abstract]: Although the shipbuilding industry is constantly demanding new advanced joining solutions, adhesive technology is not as developed in the marine as compared to other industries. The main reason is the lack of specific knowledge that guarantees the durability of the bonded joints in optimal conditions during the life cycle of a ship. This work simulates in the laboratory a marinelike environment by immersing an adhesive in seawater and subjecting it to constant loading. The objective is to characterize the seawater absorption behavior and its consequences on the mechanical, thermal, and chemical properties of the adhesive after this aging process. Seawater ingress was determined through gravimetric tests at several load conditions of the tensile strength of the adhesive. Besides, absorption process was studied using Fick’s Law, determining the diffusion coefficients. The thermal behavior was monitored with differential scanning calorimetry (DSC) and the chemical degradation was analyzed using Fourier transform infrared spectroscopy (FTIR). Also, the mechanical properties were determined by tensile tests. The surface of the adhesive (dried) was studied by Scanning Electron Microscopy (SEM) technique and the porosity was measured by physisorption with a high-performance adsorption analyzer. A numerical simulation was developed using Darcy’s Law combined with continuity equation. The results show that application of loads and immersion in seawater until full saturation of seawater improve the mechanical properties of the adhesive, but it affects negatively to the glass transition temperature. This should be considered when designing adhesive bonding joints on ships.Xunta de Galicia; ED431C-2020-14The research of Javier Tarrío Saavedra has been supported by the Ministerio de Ciencia e Innovación grant PID2020-113578RB- 100, the Xunta de Galicia (Grupos de Referencia Competitiva ED431C-2020-14), and by the CITIC, also funded by the Xunta de Galicia through the collaboration agreement between the Consellería de Cultura, Educaci´on, Formaci´on Profesional e Universidades and the Galician universities for the reinforcement of the research centers of the Galician University System (CIGUS)

Phase transformation and structural study on the severely plastic deformed Ni–Ti alloys

AbstractIn an effort to obtain nanostructures in bulk Nickel-Titanium (Ni–Ti) shape memory alloys (SMAs) and to carryout their characterisation, samples of the alloys with different compositions have been chosen and subjected to severe plastic deformation (SPD). The selected Ti-rich alloy in the as-received (AR) condition has martensite finish temperature (Mf) above room temperature (RT) and Ni-rich has austenite finish temperature (Af) below RT. SPD method is found to be one of the efficient methods to attain nanostructures. SPD of Ni–Ti alloys (Ti-rich and Ni-rich) have been performed by High Pressure Torsion (HPT) at RT. The changes in the phase transformation temperatures before and after SPD are analyzed by studying the Differential Scanning Calorimeter (DSC) plots. Further, the structural evolution of the samples subjected to SPD in the phase transformation temperature region is studied using in situ X-ray diffraction (XRD) from −180 to +180∘C. Heat treated Ti-rich NiTi samples, previously subjected to HPT, show the same transformation characteristics (transformation temperatures and transformation sequence) as those of the as-received ones. But, Ni-rich alloy shows distinct intermediate R-phase transformation, both while heating and cooling, after subjecting it to HPT followed by heat treatments

Effect of the adhesive thickness on butt adhesive joints under torsional loads

Adhesive joints are extensively used in diverse industrial applications, exploiting the improved mechanical performance they offer over classical mechanical joining methods. To effectively design adhesive joints, it is first necessary to determine the mechanical properties of the materials being used (e.g. the adhesives and adherends). In this work, an epoxy based structural adhesive was characterized under tensile and shear loads using butt joints with solid adherends. The tensile tests were performed in a universal tensile machine and the shear tests were carried out in a torsional testing machine that ensures perfect alignment of the specimens and avoids any spurious bending moments, compression and tension loads during the test. The effect of adhesive thickness on the tensile and shear properties of the adhesive was evaluated, showing that under torsional loads there is a significant effect of the adhesive layer thickness on the shear strength and stiffness of the adhesive

Experimental and numerical failure analysis of aluminium/composite single-L joints

Adhesive bonding is frequently used to manufacture complex-shaped structures. Fibre-reinforced composite materials are extensively used in many industries, such as boat building, automotive and aeronautical. Although the manufacturing methods reduce the connections to the minimum, these are still necessary due to component size and design, technological and logistical limitations. Frequently, the combination of composites with metals such as aluminium or titanium brings design benefits. This work aims to study, by experimentation and cohesive zone modelling (CZM), single-L adhesive joints between aluminium components and carbon-epoxy composites under a peel loading, considering different joint configurations and adhesives of distinct ductility. The addressed geometric parameter is the L-part thickness (tP2). The numerical analysis included the stress distributions, damage evolution, strength and failure modes. The experimental tests validated the numerical results and provided design guidelines for single-L joints. It was shown that the L-part geometry and adhesive type highly influence the joints׳ strength.info:eu-repo/semantics/publishedVersio

Strength and damage growth in composite bonded joints with defects

The use of adhesive joints is increasing in various industrial applications because of their advantages such as weight reduction, reduction of stress concentrations and ease of manufacture. However, one of the limitations of adhesive joints is the difficulty in predicting the joint strength due to the presence of defects in the adhesive. This paper presents an experimental and numerical study of single-lap joints (SLJ) with defects centred in the adhesive layer for different overlap lengths (LO) and adhesives. The numerical analysis by cohesive zone models (CZM) included the analysis of the peel (σy) and shear (τxy) stress distributions in the adhesive layer, the CZM damage variable study and the strength prediction. The joints’ behaviour was accurately characterized by CZM and showed a distinct behaviour as a function of the defect size, depending on the adhesive.info:eu-repo/semantics/publishedVersio