322,948 research outputs found
Strength evaluation and failure prediction of bolted and adhesive glass/steel joints
No full textThis paper investigates the use of bolted and brittle/ductile adhesive connections in glass structures. Two benchmark designs of shear connections are introduced and tested experimentally in quasi-static tensile tests. The designs consist of tempered glass and aluminium substrates while steel splices are used for the load application. In addition, material characterisation testing for the glass and the adhesive is performed and the outputs are used for the numerical simulation of the same joints. Pressure-sensitive, plasticity and failure models are introduced and calibrated to accurately capture the behaviour of the adhesives. Good agreement between the experimental observations and numerical predictions is achieved. The results show that both types of adhesive joints outperform bolted joints while counter-intuitively the lower strength ductile adhesive achieves consistently higher joint strength compared to the brittle adhesive. The numerical analyses highlight that brittle adhesive joints fail once the fracture strain of the adhesive has been reached, while for ductile adhesives an extensive plastic zone develops near the areas of stress concentrations thereby delaying the damage initiation
Failure prediction and optimal selection of adhesives for glass/steel adhesive joints
No full textMild steel/tempered glass adhesive joints are becoming a common occurrence in the construction industry. A numerical parametric study for adhesive property optimisation is conducted and determines strength and ductility as the main parameters affecting the joint performance. Numerical simulations include adhesive pressure-sensitivity, plasticity and failure modelling and are also used to further investigate onset and progression of damage leading to failure of the joints. Following this, the market of structural adhesives is scanned, resulting in the identification of an adhesive system that aligns with the ‘optimal’ strength and ductility parameters identified from the parametric study. The chosen adhesive system is experimentally compared and benchmarked against a brittle and a ductile adhesive in steel/glass adhesive joints subjected to four different load-cases. It is demonstrated that the proposed modelling methodology yields accurate predictions of the adhesive and adherend stress states and failure behaviour for the four different load-cases, thus highlighting the model's ability to predict the response and failure of all three adhesives and tempered glass.</p
Development of cohesive zone models for the prediction of damage and failure of glass/steel adhesive joints
No full textThe use of mild steel/tempered glass adhesive joints has increased rapidly over recent years. Cohesive zone modelling (CZM) is used extensively for the numerical analysis and failure prediction of adhesive joints. The bonding to the glass surface is generally weaker than the bonding to metal substrates, and therefore the development of cohesive laws by testing on different substrates generally leads to overoptimistic and non-conservative predictions. However, the interface characterisation using standardised methods for glass/steel joints is complicated due to the relatively low strength of the glass substrate leading to premature failure. This paper presents modifications proposed for the Double Cantilever Beam (DCB) and End Notched Flexure (ENF) tests bonded with dissimilar glass/steel adherends used to extract traction-separation laws in fracture modes I and II. For this relatively small coupon size, an in-house glass heat strengthening process was developed. The cohesive laws were validated by comparing the numerical predictions for two different adhesives with experimental test data for double lap shear joints subjected to four different load cases.</p
Artificial neural network-based geometry compensation to improve the printing accuracy of selective laser melting fabricated sub-millimetre overhang trusses
No full textSelective laser melting processes deposit and join metal powders to near net shape in a layer-by-layer manner. The process of melting and re-solidification of several layers of deposited material can result in geometric deviations, and the impact is particularly significant for sub-millimetre structures oriented at a wide range of overhang angles with respect to the building platform. This paper assesses and benchmarks the capabilities of a neural network-based geometric compensation approach for truss lattice structures with circular cross-sections. The neural network method is capable to generate free-form cross-sections with enhanced geometric freedom for compensation compared to more established analytical compensation approaches limited to predefined geometric shapes. For neural network training, lattice dome structures composed of trusses with different overhang angles were designed and printed by selective laser melting and measured via X-ray computed tomography, resulting in point cloud data sets containing more than 20,000 data points for each overhang angle. For experimental validation, neural network-compensated dome structures were benchmarked against dome structures with elliptical parameter compensation. Results show that the neural network compensated lattice trusses achieve higher printing dimensional accuracy compared to the uncompensated structures and those compensated based on elliptical parameter estimates.Full Tex
Effect of elevated temperatures and humidity on glass/steel adhesive joints
No full textGlass/steel adhesive joints are being used increasingly in the construction industry as they offer significant structural advantages. While humidity and elevated temperatures are known to lead to the degradation of both the bulk adhesive materials and the bonded interfaces, quantification and prediction of the degradation effects are currently lacking. In this paper, the effects of elevated temperatures and humidity were determined and predicted by employing a combined experimental and numerical methodology. Bulk material and interface characterisation tests were performed to quantify the degradation of the bulk material properties and the glass/steel interfaces. Two numerical methodologies were devised and compared based on their ability to predict failure of glass/steel adhesive joints following environmental exposure, namely a continuum mechanics approach based on the bulk properties of the adhesive, and a cohesive zone modelling approach that assesses damage and failure based on the glass/steel interface properties. The results highlight the significantly different relative contributions of bulk property and interface degradation depending on the type of adhesive used
Functionally graded lattice structures with tailored stiffness and energy absorption
No full textLattice structures are lightweight and are known to exhibit excellent energy absorbing capability when subject to compressive loading. In this paper, a new analytical model for the stiffness, strength, and energy absorption of additively manufactured functionally graded lattice structures is presented, leading to the establishment of a new energy absorption optimisation approach. The influence of cell orientation, cell aspect ratio, and cell relative density on the mechanical properties is characterised. The optimal through-thickness density distribution to maximise energy absorption is determined, subject to mass and initial stiffness constraints. Energy absorption is shown experimentally to increase by up to 67.1 % via tailored through-thickness grading of the structure's relative density. Finite element models are also developed to accurately describe the mechanical performance of these functionally graded lattice structures. These models provide valuable insight into the properties of functionally graded lattice structures and can serve as a basis for the tailored design of lightweight energy absorbers.Full Tex
Bio-inspired lattice structure optimisation with strain trajectory aligned trusses
No full textLattice structures have great potential for lightweight additively manufactured parts. This paper presents a bio-inspired functionally graded lattice structure optimisation approach for compliance minimisation of statically loaded structures. Topology optimisation determines the optimal relative density distribution within a design space and the associated strain fields. A lattice structure is then generated within this design space, comprised of trusses aligned with principal strain trajectories. The trusses have a rectangular cross-section, resulting in three size variable per node during the final sizing step. A minimum feature size is implemented so that the designs are suited to the particular additive manufacturing process print resolution. The presented approach is further demonstrated to efficiently solve problems with multiple load cases and produce lattice topologies that mimic those found in bone. The optimised lattice structure examples presented are on average 12% less stiff in comparison to a conventional SIMP topology optimisation approach. However, they are well suited to multifunctional applications such as heat transfer where the surface area is increased by an average of 94%. The optimised lattice structures are also shown to be able to eliminate additive manufacturing support structure requirements.Full Tex
Prediction of moisture diffusion and failure in glass/steel adhesive joints
No full textAbstractGlass/steel adhesive joints are being used increasingly in the construction industry as they offer significant structural advantages over conventional mechanical fastener approaches. However, adhesive joints are also known to be sensitive to moisture diffusion into the bondline, which reduces the interfacial bonding strength for hybrid glass/steel substrates. The effect of moisture on the performance degradation of glass/steel adhesive joints has been successfully predicted assuming adhesive property degradation but requires experimental determination of the affected moisture ingress zone. This study utilizes a multi-physics numerical approach implemented via the commercial finite element code Abaqus 2020, which firstly simulates moisture ingress into the adhesive/glass interface and subsequently couples the diffusion effects with a cohesive zone modelling approach for damage initiation and propagation. The numerical predictions are calibrated against experimental data on glass/steel Double Cantilever Beam (DCB) specimens, which are bonded with a ductile methacrylate adhesive (Araldite 2047–1). The modelling approach is then validated against the experimental response of large double lap shear joints of a significantly different bondline geometry. It is demonstrated that the numerical model successfully predicts the critical exposure time for partial to complete joint degradation enabling the development of engineering guidelines for life-time prediction of various joint geometries.</jats:p
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
