Papers by Namasivayam Navaranjan
International Journal of Food Properties, Dec 11, 2023
Journal of Food Safety, Apr 22, 2020
Innovation in colorimetric sensors to detect early signs of food spoilage is a growing interest i... more Innovation in colorimetric sensors to detect early signs of food spoilage is a growing interest in food safety and quality control. Currently available chemical dyes for sensor applications have concern because of their possible migration into food packaging and food in contact. In this study, a colorimetric indicator was developed using natural butterfly pea (Clitoria ternatea) anthocyanin with Sago (Metroxylon sagu) as polymeric film. The principle was based on pH shift due to chemical processes produced by microorganism causing anthocyanin color to change. The film was fabricated by solvent casting method and characterized by color change at different pH values, total water solubility, swelling rate, and morphological structure. Trials on chicken breast samples in various conditions exhibited that the film indicator responded well according to pH variation enabling a real‐time monitoring due to spoilage. Thus, our natural pH indicator with visible color variation allows for simple, economic and safe monitoring of perishable foods.
Journal of Food Engineering, Dec 1, 2013
Three expanded polystyrene (EPS) boxes with different thermal resistance (R-value), a box-in-box ... more Three expanded polystyrene (EPS) boxes with different thermal resistance (R-value), a box-in-box type cardboard prototype and commercial EPS boxes were packed with fish using standard industry procedures and subjected to a simulated airfreight temperature regime replicating commercial practice. The Quality Index Method was used to assess the fish quality. The boxes with lower R-values did not have a measurable negative effect on the quality compared to the commercial EPS box. There was also no measurable difference in quality between fish stored in the corners or centre of all the boxes. For another experiment a double fluted cardboard prototype and commercial EPS boxes were filled with ice and subjected to a constant temperature regime to determine their R-value. The second prototype had slightly lower R-values than commercial EPS boxes. However, the double fluted wall structure might limit the foldability and manufacturability and will need to be further investigated.
Computers & Structures, Aug 1, 2012
ABSTRACT The effect of different in-plane boundary conditions on the critical load and post-buckl... more ABSTRACT The effect of different in-plane boundary conditions on the critical load and post-buckling behaviour of a uniaxially compressed, simply supported corrugated paperboard panel is examined, with the aim of reducing the discrepancy between model and published experimental results. In-plane boundary conditions with uniform load distribution or uniform compression on the loaded edges, free or constant normal in-plane edge movement and shear free edges, are modelled. Analytical single-term Galerkin and finite element approaches are used. The critical loads obtained analytically and numerically, for different boundary conditions agree well with an analytical reference result.
Composite Structures, Sep 1, 2010
This paper uses Lock-in infrared thermography to evaluate the stress and damage states in sandwic... more This paper uses Lock-in infrared thermography to evaluate the stress and damage states in sandwich structured corrugated paperboard packaging. To this end corrugated boxes with and without handholds were subjected to compression loading and the resultant Lock-in thermal images captured. The stress contours around a handhold obtained from the Lock-in images enabled the failure mode and the structural response of
Cellulose, May 6, 2019
Understanding heat transfer in corrugated fibreboard is important to the design of more effective... more Understanding heat transfer in corrugated fibreboard is important to the design of more effective packaging for industries which involve the freezing and chilling of food. In this work the thermal conductivity of papers which compose corrugated fibreboard were measured and used to validate finite element models of heat transfer in fibreboard. The results showed paper to be highly anisotropic, with thermal conductivity in the machine and cross machine directions being almost an order of magnitude larger than in the thickness direction. The finite element models showed good agreement with experimental results and demonstrated that the majority of heat transfer in corrugated fibreboard is though the fluted medium. Based on the finite element models, simple models for the prediction of the thermal performance of corrugated board were evaluated and shown to be very effective in reproducing the results of the more complex finite element methods. These simple methods can be used to perform corrugated fibreboard design calculations, and the models with and without radiation can be used to provide estimates of the lower and upper bounds of the thermal resistance for a given board design.
Composites Part B-engineering, Feb 1, 2013
Abstract This paper evaluates the humidity effect on the elastic properties and failure mechanism... more Abstract This paper evaluates the humidity effect on the elastic properties and failure mechanism of two types of layered corrugated paperboard structures composed of entirely recycled material and virgin radiata pine (Pinus radiata D. Don) kraft and mixed fibre linerboards and fluting medium. Board samples and their component paper sheets were tested at 50% and 90% constant relative humidity (RH) under compression load and images of failure zones were obtained by serial sectioning and confocal microscopy. The compressive strength and modulus of elasticity of all components were found to be highest in the machine direction at 50% RH and lowest in the cross-machine direction at 90% RH. Virgin paper sheet components performed better in compressive performance than recycled components in both directions and at both relative humidities. In both types of corrugated board microscopic examination showed that failure under compression at 50% and 90% RH occurred along the adhesive line as well as by failure of inter-fibre bonds within the components. The combination of failure mechanisms resulted in local buckling of the boards. The elastic performance of recycled corrugated board was found to be inferior to that of virgin corrugated board at both RH conditions.
Applied Mechanics and Materials, May 1, 2014
The degradation of the connection between shear studs and concrete is a complicated phenomenon th... more The degradation of the connection between shear studs and concrete is a complicated phenomenon that depends on many factors, including; interfacial properties, concrete crushing and steel yielding. The purpose of this paper is to outline the scope and methodology of the research project being undertaken to characterise the shear stud-concrete interface of a composite beam using finite element analysis. A mesoscopic model will be created for a section of the interface. With the use of a multi-scale approach, the mesoscopic model will be incorporated into a global model. The influence of steel roughness and mechanical properties will be included. Concrete is to be modelled as heterogeneous, comprising discrete regions of aggregate, cement matrix, and an interfacial transition zone (ITZ). The effect of the ITZ will be taken into account using a zero thickness cohesive element. Experimental testing using a push-up rig is to be conducted to verify the numerical models. The ultimate aim is to develop a simplified representation of the shear stud-concrete interface that can be used in a large scale finite element model of a composite member to correctly capture the behaviour of the shear stud-concrete interface in the elastic and inelastic state.
International Journal of Applied Mechanics, Dec 1, 2015
Foam–metal composites are being increasingly used in a variety of applications. One important asp... more Foam–metal composites are being increasingly used in a variety of applications. One important aspect in the structural integrity of foam–metal interface is the ability to resist failure around the interface whilst ensuring required load bearing capacity. This study investigated the mechanical and failure behavior at the interface region at micro-scale. The foam–metal composite consisted of polyurethane (PU) foam directly adhered to a galvanized steel face sheet. Optical, scanning electron and atomic force microscopies were used to examine the interface geometry and to obtain a realistic surface profile for use in a finite element (FE) model. Finite element analysis (FEA) was used to study the effects of different interfacial roughness profiles on the mechanical interlocking and modes of failure, which are directly related to the interfacial strength. A set of FE models of idealized surface pairs of different geometries and dimensions were developed based on the microscopic observations at the foam–metal interface. The FE modeling results show that the micro-scale roughness profile at the foam–metal interface causes mechanical interlocking and affects the stress field at the scale of the interface surface roughness, which consequently governs the specific failure mode and the relative proportion of the cohesive to adhesive failure in the interface region for a given foam–metal interface. It was found that the aspect ratio (relative width and height) and width ratio (relative spacing) of roughness elements have a significant effect on the stresses and deformations produced at the interface and consequently influence the modes (cohesive or adhesive) of failure.
Journal of Materials Science, Jun 1, 2008
A new method based on the atomic force microscope has been developed to measure the lateral flexi... more A new method based on the atomic force microscope has been developed to measure the lateral flexibility of single wood pulp fibres. In this method, individual wet pulp fibres from earlywood and latewood of Pinus radiata were placed on a newly designed two-point support, and the load and the deflection of fibres were measured under three-point bending test using a modified cantilever probe. The lateral flexibility values of the fibres were then calculated using propped cantilever beam theory. The results obtained indicate that earlywood fibres are substantially more flexible, and have a greater range of flexibility values than latewood fibres.
Journal of Applied Crystallography, May 13, 2005
A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the micr... more A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the microfibril angle and the associated standard deviation for the cellulose microfibrils in the S 2 layer of the cell walls of softwood specimens. The length and orientation of over 1000 cell walls in the irradiated volume of the specimen are measured using quantitative image analysis. From these data are calculated the azimuthal variation of the scattered intensity. The calculated values are compared with the measured values. The undetermined parameters in the analysis are the microfibril angle (M) and the standard deviation (È) of the intensity distribution arising from the wandering of the fibril orientation about the mean value. The two parameters are varied to give the best fit between the calculated and the measured values. Six separate pairs of values are determined for six different values of the angle of incidence of the X-ray beam relative to the normal to the radial direction in the specimen. The results show good agreement. The azimuthal distribution of scattered intensity for the real cell-wall structure is compared with that calculated for an assembly of rectangular cells with the same ratio of transverse to radial cell-wall lengths. Despite the existence of marked differences in the intensity distributions around the zero azimuth angle, the position of the extreme flanks of the distribution is very close for the real and the rectangular cells. This means that useful values of the microfibril angle can be obtained from the curve for the real cells using the Meylan parameter T derived by drawing tangents to the flanks of the intensity distribution and using M = kT. The value of k is M/(M + 2 È). Since both of these parameters are determined in the work now described, k is also determined. It is also demonstrated that for = 45 (where is the angle between the plane face of the wood specimens and the radial direction) the peaks in the azimuthal intensity distribution for the real and the rectangular cells coincide. If this peak position is È 45 , then the microfibril angle can be determined from the relation M = tan À1 (tan È 45 /cos 45), which is precise for rectangular cells.
Journal of Plant Nutrition and Soil Science
World Academy of Science, Engineering and Technology, International Journal of Materials and Metallurgical Engineering, 2016
Proceedings of the Twelfth International Conference on Computational Structures Technology
ABSTRACT This paper demonstrates the impact of including multi-term symmetric and anti-symmetric ... more ABSTRACT This paper demonstrates the impact of including multi-term symmetric and anti-symmetric out-of-plane displacement shapes functions and geometric imperfection modes on panel post-buckling behaviour, using multi-term analytical Galerkin’s models of corrugated paperboard. Comparisons of single- and multi-term solutions show a nine-term symmetric displacement mode model’s central deflection can differ by as much as 16% at a load of 1.8 times the critical load compared to a single-term result. Investigations for panels with both symmetric and anti-symmetric displacement modes show that if either a symmetric or anti-symmetric panel imperfection were present, only higher modes of the same type as the imperfection contribute to the panel displacement. However, if both symmetric and anti-symmetric panel imperfections were present, the symmetric and anti-symmetric displacement modes influence each other’s relative amplitudes noticeably. The direction and magnitude of higher imperfection modes present relative to the fundamental imperfection mode affect the apparent panel stiffness below the critical load, observed as higher or lower panel centre displacements. A smaller fundamental imperfection mode with additive higher imperfection modes causes the panel to appear stiffer, while a larger fundamental imperfection mode with opposing higher imperfection modes makes the panel appear more flexible, than a panel with only a fundamental imperfection mode.
Seasoned softwood board exposed to in-service moisture variations is subject to dimensional chang... more Seasoned softwood board exposed to in-service moisture variations is subject to dimensional changes and distortions. In-service dimensional instability of a board is a critical issue since it causes serious problems in buildings and other engineering structures. This thesis presents research involving the development of numerical models to describe the in-service changes in dimension, at a board scale, for small variations in the moisture content. The models used input data defining the properties of the microstructural components that make up the cellular structure of the wood resulting in the cells having heterogeneous anisotropic properties. The application of full cyclic constraint to the boundaries of the elements that made up the representative volume element was investigated and used to determine the equivalent homogenised properties. A cellular model was developed to describe the behaviour of the wood as a function of density, microfibril angle, spiral grain angle and moistu...
The 6th International Conference on Computational Methods (ICCM2015), May 4, 2015
Cellulose, 2019
Understanding heat transfer in corrugated fibreboard is important to the design of more effective... more Understanding heat transfer in corrugated fibreboard is important to the design of more effective packaging for industries which involve the freezing and chilling of food. In this work the thermal conductivity of papers which compose corrugated fibreboard were measured and used to validate finite element models of heat transfer in fibreboard. The results showed paper to be highly anisotropic, with thermal conductivity in the machine and cross machine directions being almost an order of magnitude larger than in the thickness direction. The finite element models showed good agreement with experimental results and demonstrated that the majority of heat transfer in corrugated fibreboard is though the fluted medium. Based on the finite element models, simple models for the prediction of the thermal performance of corrugated board were evaluated and shown to be very effective in reproducing the results of the more complex finite element methods. These simple methods can be used to perform corrugated fibreboard design calculations, and the models with and without radiation can be used to provide estimates of the lower and upper bounds of the thermal resistance for a given board design.Graphical abstract
Foam-metal composites are being increasingly used in a variety of applications. One important asp... more Foam-metal composites are being increasingly used in a variety of applications. One important aspect in the structural integrity of foam-metal interface is the ability to resist failure around the interface whilst ensuring required load bearing capacity. This study investigated the mechanical and failure behaviour at the interface region at micro scale. The foam-metal composite consisted of polyurethane foam directly adhered to a galvanised steel face sheet. Optical, scanning electron and atomic force microscopy were used to examine the interface geometry and to obtain a realistic surface profile for use in a finite element (FE) model. Finite element analysis (FEA) was used to study the effects of different interfacial roughness profiles on mechanical interlocking and modes of failure, which are directly related to interfacial strength. A set of finite element models of idealised surface pairs of different geometries and dimensions were developed based on the microscopic observation...
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Papers by Namasivayam Navaranjan