Publications
239 results found
Rolfe E, Kelly M, Arora H, et al., 2017, Failure analysis using X-ray computed tomography of composite sandwich panels subjected to full-scale blast loading, Composites Part B: Engineering, Vol: 129, Pages: 26-40, ISSN: 1359-8368
The tailorable mechanical properties and high strength-to-weight ratios of composite sandwich panels make them of interest to the commercial marine and naval sector, however, further investigation into their blast resilience is required. The experiments performed in this study aimed to identify whether alterations to the composite skins or core of a sandwich panel can yield improved blast resilience both in air and underwater. Underwater blast loads using 1.28 kg TNT equivalent charge at a stand-off distance of 1 m were performed on four different composite sandwich panels. Results revealed that implementing a stepwise graded density foam core, with increasing density away from the blast, reduces the deflection of the panel and damage sustained. Furthermore, the skin material affects the extent of panel deflection and damage, the lower strain to failure of carbon-fibre reinforced polymer (CFRP) skins reduces deflection but increases skin debonding. A further two panels were subjected to a 100 kg TNT air blast loading at a 15 m stand-off to compare the effect of a graded density core and the results support the underwater blast results. Future modelling of these experiments will aid the design process and should aim to include material damage mechanisms to identify the most suitable skins.
Zhou J, Kaboglu C, Mohaghegian I, et al., 2017, High velocity impact resistance of fibre metal laminates, 21th International Conference on Composite Materials
Rolfe E, Kelly M, Arora H, et al., 2017, Full-scale blast testing of composite sandwich structures with novel skin and core constructions, 14th International Conference on Fracture, Pages: 167-168
© 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved. A range of composite sandwich panels with different polymeric foam cores and face-sheets were subjected to full-scale air and underwater blast testing. The panel with a styrene acrylonitrile (SAN) foam core had the lowest deflection and suffered from the least damage. By implementing a stepwise graded density SAN foam core, a smoother deflection profile during air blast can be achieved. Underwater blast testing revealed that implementing a stepwise graded density core reduces the panel deflection. Additionally, there is a trade-off between reduced panel deflection and damage depending on the skin material selected.
Kaboglu C, Liu J, Blackman BRK, et al., 2017, The effects of different types of architecture of composite and matrix on the impact behaviour of Carbon Fibre Reinforced Composites, ICAS2017 - International Conference on Advances in Science
Kaboglu C, Pimenta S, Morris A, et al., 2017, The Influence of different types of core materials on the impact behaviour of sandwich structures, 3rd Global Conference on Materials Science
Li X, Jiang L, Wang Y, et al., 2017, Correlation between K+-Na+ diffusion coefficient and flexural strength of chemically tempered aluminosilicate glass, Journal of Non-Crystalline Solids, Vol: 471, Pages: 72-81, ISSN: 1873-4812
The correlation between K+-Na+ diffusion coefficient and mechanical properties of chemically tempered and hybridly tempered (thermally plus chemically tempered) aluminosilicate glass is investigated. First, the profile of the potassium ion concentration is experimentally measured, and the diffusion coefficient is calculated according to the Boltzmann-Matano approach. Second, the flexural strength and the Weibull modulus are determined using a method combining experimental (coaxial double ring) and finite element analysis. The results indicate that the flexural strength decreases with the diffusion coefficient of the air side for both types of glass samples, while there is no significant relationship between the diffusion coefficient and the Weibull modulus. The diffusion coefficient on the air side shows a higher value than that on the tin side. With the same diffusion coefficient, the flexural strength of chemically tempered glasses is found to be higher than that of hybridly tempered glasses. The effect of the diffusion coefficient on the modulus of rupture (MOR) for the hybridly tempered glass is more remarkable. These results would be useful for designing the glass strength and guiding the strengthening process by chemical or hybrid tempering.
Tebbutt JA, Vahdati M, Carolan D, et al., 2017, Numerical investigation on an array of Helmholtz resonators for the reduction of micro-pressure waves in modern and future high-speed rail tunnel systems, Journal of Sound and Vibration, Vol: 400, Pages: 606-625, ISSN: 1095-8568
Previous research has proposed that an array of Helmholtz resonators may be an effective method for suppressing the propagation of pressure and sound waves, generated by a high-speed train entering and moving in a tunnel. The array can be used to counteract environmental noise from tunnel portals and also the emergence of a shock wave in the tunnel. The implementation of an array of Helmholtz resonators in current and future high-speed train-tunnel systems is studied. Wave propagation in the tunnel is modelled using a quasi-one-dimensional formulation, accounting for non-linear effects, wall friction and the diffusivity of sound. A multi-objective genetic algorithm is then used to optimise the design of the array, subject to the geometric constraints of a demonstrative tunnel system and the incident wavefront in order to attenuate the propagation of pressure waves. It is shown that an array of Helmholtz resonators can be an effective countermeasure for various tunnel lengths. In addition, the array can be designed to function effectively over a wide operating envelope, ensuring it will still function effectively as train speeds increase into the future.
Kaboglu C, Pimenta S, Morris A, et al., 2017, The effect of different types of core material on the flexural behavior of sandwich composites for wind turbine blades, Journal of Thermal Engineering, Vol: 3, Pages: 1102-1109, ISSN: 2148-7847
In this study, three differently-configured sandwich structures were manufactured with three different core materials: Balsa wood, Tycor and Polyethylene terephthalate (PET). Glass-Fibre Reinforced Polymer (GFRP) skins were used to understand the effects of different types of core materials on the flexural behavior of sandwich composites under four point bending (4PB) condition, using digital image correlation (DIC). DIC is one of the most outstanding techniques to understand the mechanical behavior of the structure during the test, thus defining any problematic regions in the structures. The failure mechanisms of the structures were observed by using strain maps of the structures. The results show that the sandwich structure with Balsa wood as a core material has the highest stiffness; however, catastrophic failure appeared in the early stages of the test. The sandwich structure with PET and Tycor exhibited very similar behaviour under load.
Mohagheghian I, Wang Y, Zhou J, et al., 2017, Deformation and damage mechanisms of laminated glass windows subjected to high velocity soft impact, International Journal of Solids and Structures, Vol: 109, Pages: 46-62, ISSN: 0020-7683
Bird strike can cause serious risks to the safety of air travel. In this paper, the aim is to improve design by determining deformation and damage mechanisms of laminated glass windows when subjected to high velocity soft impacts. To achieve this, laboratory-scale impact experiments using bird substitute materials were performed in the velocity range of 100–180 m s−1. An important step forward is that high-speed 3D Digital Image Correlation (DIC) has effectively been employed to extract the full-field deformation and strain on the back surface of the specimens during impact. The finite element simulations were performed in Abaqus/explicit using Eulerian approach and were able to represent successfully the experiments.For the laminated glass structures investigated, the damage inflicted is strongly sensitive to the nose shape of the projectile and most deleterious is a flat-fronted projectile. Two threshold velocities for impact damage have been identified associated with firstly the front-facing and secondly the rear-facing glass layer breaking. The order of the glass layers significantly influences the impact performance. The findings from this research study have led to a deeper and better-quantified understanding of soft impact damage on laminated glass windows and can lead to more effective design of aircraft windshields.
Jiang L, Wang Y, Mohagheghian I, et al., 2017, Subcritical crack growth and lifetime prediction of chemically strengthened aluminosilicate glass, Materials & Design, Vol: 122, Pages: 128-135, ISSN: 0261-3069
The effect of residual stress on subcritical crack growth in chemically strengthened aluminosilicate glass in air and water was firstly investigated using the double torsion (DT) technique. An experimental evaluation procedure was developed based on the DT method. The research demonstrates that high compressive stress (CS) and low central tension (CT) in chemically strengthened glass are beneficial in improving crack growth index and decreasing susceptibility to fatigue. Chemically strengthened glass with high CS and low CT exhibits a smaller proof-test ratio, which indicates better survival characteristics. The results are useful in designing the strength and optimizing the strengthening process by ion exchange to obtain a more robust glass with long service lifetime.
Arora H, Del Linz P, Dear J, 2017, Damage and deformation in composite sandwich panels exposed to multiple and single explosive blasts, International Journal of Impact Engineering, Vol: 104, Pages: 95-106, ISSN: 0734-743X
The blast resistance of glass- bre reinforced polymer (GFRP) sandwich struc-tures has been investigated for increasing shock intensity and for multipleblast exposures. In this study, sandwich panels of 1.6 m x 1.3 m were subjec-ted to 30 kg charges of C4 explosive at stand-o distances from 8 m to 16 m.These targets formed part of two studies presented here: one, to observe theloading of the same geometry of target to an increasing shock intensity; andthe second, to observe the response of one target to multiple blast impacts.Experimental data provides detailed data for sandwich panel response,which are often used in civil and military structures, where air-blast load-ing represents a serious threat. High-speed photography, with digital imagecorrelation (DIC), and laser gauge systems were employed to monitor thedeformation of these structures during the blasts. The experimental dataprovides for the development of analytical and computational models. Ini-tial analysis of the blast experiments are presented alongside a nite elementmodel to establish trends in deformation behaviour. Details of failure mech-anisms and the conditions for the onset of failure are also discussed.
Dear JP, Rolfe E, Kelly M, et al., 2017, Blast performance of composite sandwich structures, 11th International Symposium on Plasticity and Impact Mechanics (IMPLAST), Publisher: Elsevier, Pages: 471-478, ISSN: 1877-7058
A range of composite sandwich panels with different polymeric foam cores and face-sheets were subjected to full-scale air and underwater blast testing. The air blast panels had glass fiber reinforced polymer (GFRP) face-sheets with three different polymeric foam cores: styrene acrylonitrile (SAN), polyvinylchloride (PVC) and polymethacrylimide (PMI). The panels were subjected to 100 kg TNT equivalent charge from a stand-off of 15 m. The SAN panel had the lowest deflection and suffered from the least damage. The underwater blast panels had either a single density or graded density SAN foam core and either glass fiber reinforced polymer or carbon fiber reinforced polymer (CFRP) face-sheets. The research revealed that there is a trade-off between reduced panel deflection and damage. All the blast research that has been performed is part of a program sponsored by the Office of Naval Research (ONR).
Mohagheghian I, Wang Y, Jiang L, et al., 2017, Quasi-static bending and low velocity impact performance of monolithic and laminated glass windows employing chemically strengthened glass, European Journal of Mechanics A - Solids, Vol: 63, Pages: 165-186, ISSN: 0997-7538
In this paper, firstly the quasi-static bending performance of chemically strengthened alumina silicate glass plates is investigated for different glass thicknesses: 2.2, 4.0 and 6.0 mm. The flexural strength is measured using coaxial double ring experiments. The 3D Digital Image Correlation (DIC) technique is employed to measure the strain at failure. The failure probability is then assessed using the Weibull statistical distribution.Secondly, the performance of the laminated glass windows made of these chemically strengthened glass plates is evaluated quasi-statically under concentrated and distributed loadings. The effects of polymer interlayer thickness, glass and polymer type and multi-layering the polymer interlayer on the structural performance are investigated. The type and thickness of the polymer interlayer, as well as the type of loading are found to influence the fracture sequence in the glass plates and consequently the post fracture safety of the structure. The response of laminated glass specimens is then assessed under low velocity soft impacts, for velocities up to 3.3 m s−1, using a drop tower facility. Laminated glass with a polyvinyl butyral (PVB) interlayer shows the greatest improvement in terms of peak force and absorbed energy.
Rolfe E, Kelly M, Arora H, et al., 2017, Composite materials for blast applications in air and underwater, DYNAMIC RESPONSE AND FAILURE OF COMPOSITE MATERIALS AND STRUCTURES, Editors: Lopresto, Langella, Abrate, Publisher: WOODHEAD PUBL LTD, Pages: 263-295, ISBN: 978-0-08-100887-4
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Arora H, Rolfe E, Kelly M, et al., 2017, Full-Scale Air and Underwater-Blast Loading of Composite Sandwich Panels, EXPLOSION BLAST RESPONSE OF COMPOSITES, Editors: Mouritz, Rajapakse, Publisher: WOODHEAD PUBL LTD, Pages: 161-199, ISBN: 978-0-08-102092-0
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Rolfe E, Kelly M, Arora H, et al., 2016, X-ray CT analysis after blast of composite sandwich panels, Procedia Engineering, Vol: 167, Pages: 176-181, ISSN: 1877-7058
Four composite sandwich panels with either single density or graded density foam cores and different face-sheet materials were subjected to full-scale underwater blast testing. The panels were subjected to 1kg PE4 charge at a stand-off distance of 1 m. The panel with graded density core and carbon fiber face-sheets had the lowest deflection. Post-blast damage assessment was carried out using X-ray CT scanning. The damage assessment revealed that there is a trade-off between reduced panel deflection and panel damage. This research has been performed as part of a program sponsored by the Office of Naval Research (ONR).
Ahn J, He E, Chen L, et al., 2016, Prediction and measurement of residual stresses and distortions in fibre laser welded Ti-6Al-4V considering phase transformation, Materials & Design, Vol: 115, Pages: 441-457, ISSN: 0261-3069
Residual stresses and distortions due to time dependent and localised heating imposed during fibre laser welding a 2.0 mm thick titanium alloy Ti-6Al-4V sheet were studied. Sequentially coupled thermo-metallurgical-mechanical simulations were performed to predict welding induced residual stresses and distortion in the fibre laser weld sample, and validated using an experimental database including weld pool geometry and temperature fields. Residual stress measurements were taken using X-ray and neutron diffraction techniques and distortion measurements were recorded using a coordinate measuring machine (CMM). The influence of thermally driven non-isothermal diffusional and diffusionless solid state phase transformations on welding residual stresses and distortions were considered in the numerical model. An internal state variables approach was used to represent the transformed volume fraction of different microstructural phases as a function of cooling rate and peak temperature, and the volumetric change due to temperature variations and phase transformations were calculated. In addition, post weld heat treatment (PWHT) as a method for reducing residual stresses was examined.
Ahn J, Chen L, He E, et al., 2016, Effect of filler metal feed rate and composition on microstructure and mechanical properties of fibre laser welded AA 2024-T3, Journal of Manufacturing Processes, Vol: 25, Pages: 26-36, ISSN: 1526-6125
The influence of aluminium alloy 4043 filler wire feed rate on the weld quality and mechanical properties of high power 5 kW fibre laser welded aluminium alloy 2024-T3 was investigated. Loss of volatile alloying elements such as magnesium and other elements including copper and silicon which all contributed to the hot crack sensitivity was measured using energy dispersive X-ray spectroscopy at different filler wire feed rates. High feed rates of above 4.0 m/min produced instabilities, whereas, low feed rates below 2.0 m/min did not sufficiently modify the chemical composition of the weld pool. The optimum feed rate was found to be in the range between 2 and 3 m/min, where the corresponding dilution ratio of around 9–12% in the weld pool with less than 0.6% silicon content reduced the percentage of Mg2Si and also decreased the solidification temperature and total shrinkage during freezing. The addition of filler metal reduced the risk of welding defects and improved ductility to over 3.5% and a fairly higher tensile strength of around 380 MPa than without. Microstructural examination showed that the addition of filler wire increased the number of finer dimples within the weld, resulting in a purely ductile fracture behaviour, as well as reduced micro hot cracks and porosities.
Mohamed M, Lin J, Foster A, et al., 2016, Formability investigation using a new test design for hot stamping processes, International Journal of Materials and Product Technology, Vol: 54, Pages: 3-19, ISSN: 0268-1900
Hot stamping is widely used in the forming of lightweight automotive panel components. The process optimisation requires knowledge of constitutive relations of work-piece material but assessment of formability of materials in hot stamping conditions is exceptionally challenging. A testing method and corresponding specimen design are developed in this paper for evaluating formability of materials in hot stamping conditions. A series of tests have been carried out for AA6082 aluminium alloy, at different forming rates and failure modes have been analysed. A set of stress-state dependent damage equations for AA6082 is introduced and this has been input into the FE code, ABAQUS. An FE model is developed and validated from the experimental results. Failure modes at particular forming conditions are predicted and designed specimen shapes are optimised for different forming conditions. It is concluded that work-piece design is related to ductility for hot stamping conditions and recommendations for work-piece design are given.
Mohamed M, Lin J, Foster A, et al., 2016, Formability investigation using a new test design for hot stamping processes, INTERNATIONAL JOURNAL OF MATERIALS & PRODUCT TECHNOLOGY, Vol: 54, Pages: 3-19, ISSN: 0268-1900
Jiang L, Wang L, Mohagheghian I, et al., 2016, Effect of residual stress on the fracture of chemically strengthened thin aluminosilicate glass, Journal of Materials Science, Vol: 52, Pages: 1405-1415, ISSN: 1573-4803
The effect of residual stress on the fracture of chemically strengthened thin aluminosilicate glass was investigated. The large deflection problem on the flexure of thin chemically strengthened glass was solved through finite element analysis. The relationship among compressive stress (CS), central tension (CT), and the modulus of rupture of chemically strengthened thin glass was also discussed. High CS and low CT improved the flexural strength of chemically strengthened glass. However, the effect of residual stress was more complex on Weibull modulus than on strength. The effect of residual stress on the fractography of chemically strengthened thin glass was analyzed. Transparent and opaque zones were observed on the fracture surface of chemically strengthened glass. The relative thickness of the opaque zone (dOpaque/d0), which is a constant in the same fracture zone, linearly decreased with increasing fracture zone. This result indicates that the stored elastic strain energy was released with the number of transverse cracks. These results provide useful information on the failure analysis of chemically strengthened thin glass.
Jia L, Yu L, Zhang K, et al., 2016, Combined modelling and experimental studies of failure in thick laminates under out of plane shear, Composites Part B - Engineering, Vol: 105, Pages: 8-22, ISSN: 1359-8368
A multi-scale model validated with out-of-plane shear testing is presented to analyse thick composite structural failure. Key features of this multi-scale analysis approach are inclusion of shear non linearity and modelling the response at a sub-laminate level whilst the structural failure is predicted at a ply level. Based on this multi-scale approach, a user-defined FORTRAN subroutine (VUMAT) has been written for ABAQUS/EXPLICIT solver and is used to model the shear nonlinearity and intra-laminar failure. In addition, a cohesive zone model is used to predict the inter-laminar delamination. The modelling has been employed to predict the failure processes for Iosipescu shear test specimens with different fibre orientations. The results show that both the failure mode and the load-displacement trace for finite element simulations agree closely with the experimental findings. This demonstrates the validity of this multi-scale, nonlinear, three-dimensional model for thick laminates. In particular, for the Iosepescu shear test, the effect of the fibres being aligned along the length of the specimen or out-of-plane is investigated as well as different dimensions of the specimen. These simulations are validated by experiments using Digital Image Correlation (DIC).
Sancho A, Cox MJ, Cartwright T, et al., 2016, Experimental techniques for ductile damage characterisation, Procedia Structural Integrity, Vol: 2, Pages: 966-973, ISSN: 2452-3216
Ductile damage in metallic materials is caused by the nucleation, growth and coalesce of voids and micro-cracks in the metal matrix when it is subjected to plastic strain. A considerable number of models have been proposed to represent ductile failure focusing on the ultimate failure conditions; however, only some of them study in detail the whole damage accumulation process. The aim of this work is to review experimental techniques developed by various authors to measure the accumulation of ductile damage under tensile loads. The measurement methods reviewed include: stiffness degradation, indentation, microstructure analysis, ultrasonic waves propagation, X-ray tomography and electrical potential drop. Stiffness degradation and indentation techniques have been tested on stainless steel 304L hourglass-shaped samples. A special interest is placed in the Continuum Damage Mechanics approach (CDM) as its equations incorporate macroscopic parameters that can represent directly the damage accumulation measured in the experiments. The other main objective lies in identifying the strengths and weaknesses of each technique for the assessment of materials subjected to different strain-rate and temperature conditions.
Cornish A, Smith RA, Dear J, 2016, Monitoring of strain of in-service railway switch rails through field experimentation, Proceedings of the Institution of Mechanical Engineers Part F -Journal of Rail and Rapid Transit, Vol: 230, Pages: 1429-1439, ISSN: 0954-4097
In the financial year 2009/10, the Great Britain (GB) rail infrastructure manager, Network Rail, spent £32 million on the failures within switches and crossings. Approximately 53% of those failures occurred within the switch panel. In addition, two major incidents in GB in recent years have highlighted a lack of understanding of the loads and vibrations experienced by, and the consequent rates of deterioration of, switch panels. This paper describes work which has been undertaken to help improve understanding of in-service loads experienced by switch panels and their consequent deterioration rate. Field experimentation has been designed and installed on four sites around GB, with the same design of switch. The change in response to loading, and the rate of deterioration, of the switch panels at each site was monitored over time. The effect of the vehicles and the deterioration were analysed individually before a comparison between the four sites. The analysis from the strain gauge measurements showed that there was an increase in the variance and maximum strains generated on the stock rail with the switch closed compared to when the switch is open. Finite element analysis was used to validate variation recorded by the strain gauges under similar loads.
Del Linz P, Wang Y, Hooper PA, et al., 2016, Determining Material Response for Polyvinyl Butyral (PVB) in Blast Loading Situations, Experimental Mechanics, Vol: 56, Pages: 1501-1517, ISSN: 1741-2765
Protecting structures from the effect of blast loads requires the careful design of all building components. In this context, the mechanical properties of Polyvinyl Butyral (PVB) are of interest to designers as the membrane behaviour will affect the performance of laminated glass glazing when loaded by explosion pressure waves. This polymer behaves in a complex manner and is difficult to model over the wide range of strain rates relevant to blast analysis. In this study, data from experimental tests conducted at strain rates from 0.01 s−1 to 400 s−1 were used to develop material models accounting for the rate dependency of the material. Firstly, two models were derived assuming Prony series formulations. A reduced polynomial spring and a spring derived from the model proposed by Hoo Fatt and Ouyang were used. Two fits were produced for each of these models, one for low rate cases, up to 8 s−1, and one for high rate cases, from 20 s−1. Afterwards, a single model representing all rates was produced using a finite deformation viscoelastic model. This assumed two hyperelastic springs in parallel, one of which was in series with a non-linear damper. The results were compared with the experimental results, assessing the quality of the fits in the strain range of interest for blast loading situations. This should provide designers with the information to choose between the available models depending on their design needs.
Samieian MA, Cormie D, Doebbel F, et al., 2016, Experimental investigation into the strength of single sided silicone glazing joints under blast loading, Challenging Glass Conference 5, Publisher: TU Delft, ISSN: 2589-8019
An experimental study has taken place to quantify the strength of single sided structural silicone glazing joints under blast loading. The structural silicone specimens in this experiment were tested using a high-speed servo-hydraulic test machine at varying rates, representative of that experienced in a blast. Tests were conducted at displacement rates of 1m/s, 2m/s and 4m/s. The load was applied at two different angles of 30° and 45°. The tests were carried out on samples with different bite depths. The load was measured and the strength of the silicone joint was calculated at different testing rates. For a given testing rate and loading angle, the strength was found to be constant for different bite depths. The strength also showed an escalation at higher displacement rates. For the loading angles tested, there was no correlation found between the angle of loading and the strength. Through the measurement of displacement during the test, the work done on the silicone joint was also calculated.
Ahn J, Chen L, Davies CM, et al., 2016, Parametric optimisation and microstructural analysis on high power Yb-fibre laser welding of Ti-6Al-4V, Optics and Lasers in Engineering, Vol: 86, Pages: 156-171, ISSN: 1873-0302
In this work thin sheets of Ti–6Al–4V were full penetration welded using a 5 kW fibre laser in order to evaluate the effectiveness of high power fibre laser as a welding processing tool for welding Ti–6Al–4V with the requirements of the aircraft industry and to determine the effect of welding parameters including laser power, welding speed and beam focal position on the weld microstructure, bead profile and weld quality. It involved establishing an understanding of the influence of welding parameters on microstructural change, welding defects, and the characteristics of heat affected zone (HAZ) and weld metal (WM) of fibre laser welded joints. The optimum range of welding parameters which produced welds without cracking and porosity were identified. The influence of the welding parameters on the weld joint heterogeneity was characterised by conducting detailed microstructural analysis.
Narayanan A, Maharaj C, Kelly M, et al., 2016, Recent developments in measuring creep strain in high temperature plant components, Strain, Vol: 52, Pages: 467-477, ISSN: 1475-1305
Accurate measurements of creep strain are necessary to evaluate the condition and predict the remaining life of power plant constituent materials. Optical techniques are appropriate for this purpose as they are a non-contact method and can therefore be used to measure strain without requiring direct access to the surface. Within this class of techniques, the Auto-Reference Creep Management And Control (ARCMAC) camera system can be used to calculate the strain between two points using a series of silicon nitride (SiN) target spheres (the ARCMAC gauge). There are two iterations in system design, the Conventional ARCMAC and Digital Single-Lens Reflex (DSLR) ARCMAC.Experiments are conducted to determine the absolute limit of accuracy of the systems in comparison to a strain gauge, and the relative accuracy across several orders of magnitude until specimen failure. In addition, tests have been performed using the ARCMAC gauge at elevated temperatures to evaluate the effect of temperature on the gauges and to investigate whether its accuracy diminishes in creep conditions.It was found that both conventional and DSLR ARCMAC systems can be accurate to 60 µε or less. In accelerated creep tests, the ARCMAC gauge produced similar agreement to a linear variable displacement transducer when used to measure creep strain. Strain variations (under 500 µε) were noted on a steel plate subjected only to operational temperature and no stress. This error is very reasonable compared to a critical strain value of 93,000 µε in a given high temperature-service material. Digital Image Correlation (DIC) results using the DSLR ARCMAC system show approximately 4% error in measurement for plastic strains in the specimen. The two measures of strain measurement (using ARCMAC and DIC) can serve to complement each other.
Del Linz P, Hooper PA, Arora H, et al., 2016, Delamination properties of laminated glass windows subject to blast loading, International Journal of Impact Engineering, Vol: 105, Pages: 39-53, ISSN: 1879-3509
Delamination processes absorb significant amounts of energy in laminated glass windows when they are subjected to blast loads. Blast tests were performed previously and their results had been used to calculate the loads imposed on the support systems. In this research, the delamination process at realistic deformation rates was studied to understand the reaction force response obtained. Laboratory tensile tests were performed on pre-cracked laminated glass specimens to investigate their delamination behaviour. The experiments confirmed the presence of a plateau in the force-deflection graphs, suggesting that the delamination process absorbed significant energy. The experimental results were then employed to calibrate FEA models of the delamination process with the aim of estimating the delamination energy of the polyvinyl butyral (PVB) membrane and glass layers and its relationship with deformation speed. The delamination energies obtained through this research, if used with the appropriate PVB material model, are a valuable new tool new tool in the modelling and design of laminated glass façade structures.
Del Linz P, Liang X, Hooper PA, et al., 2016, An analytical solution for pre-crack behaviour of laminated glass under blast loading, Composite Structures, Vol: 144, Pages: 156-164, ISSN: 0263-8223
Laminated glazing is often employed to minimise damage and injuries during blast events. In this work, the von Karman theory for large deflections of plates was used to simulate the effect of large explosions on laminated glazing. Linear material properties were assumed for both the glass and Polyvinyl Butyral layers. The glass and PVB layers were assumed to act fully compositely during the pre-crack phase of the deformation. A higher order deflection function was employed to represent the complex deformed shape observed in DIC blast test data collected by Hooper et al. [1]. The deflection results showed that the method developed could produce accurate estimates of the glazing deformation history during a blast event. The analytical solution was also used to compute the reaction forces acting on the window supports, which were found to be of a similar magnitude to those calculated from experimental data. In addition, crack densities were predicted, which were found to follow a pattern similar to those seen in blast experiments. The analytical approach developed is valuable for risk assessment engineers and façade designers who much prefer analytically based models over full-scale FE analysis, as FEA is often too time consuming for design assessments.
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