International Journal of Materials and Structural Integrity (15 papers in press)
Deformational inhomogeneity in Al-8Mg alloy microhardness study
by Swami Naidu Gurugubelli, A.V.S.S.K.S. Gupta, N.R.M.R. Bhargava
Thermal cycling reliability of lead-free package stackable very thin fine pitch ball grid array (PSvfBGA) assemblies with reworkable edge and corner bond adhesives
by Hongbin Shi, Toshitsugu Ueda
Constant-pressure molecular dynamics simulation of thermal bubble nucleation in rough wall nanochannels
by Min Chen, Dawei Jiang, Kunpeng Jiang
Flexural fatigue analysis of fibre-reinforced polymer concrete composites under non-reversed loading
by Raman Bedi, S.P. Singh
Abstract: Results of an investigation on the flexural fatigue performance of Polypropylene Fibre-Reinforced Polymer Concrete Composites (PFRPCC) are presented. Flexural fatigue lives of PFRPCC beams at different stress levels were obtained using a 100 kN MTS servo-controlled actuator. The specimens incorporated three weight fractions, i.e. 0.5%, 1.0% and 2.0%, of polypropylene fibres. It has been established using a graphical goodness of fit procedure that the fatigue life distributions of PFRPCC at various stress levels approximately follow the two-parameter Weibull distribution with correlation coefficient exceeding 0.9. The results of the graphical goodness of fit procedure have been reinforced with the help of the Kolmogorov-Smirnov goodness of fit test and the Anderson-Darling test of goodness of fit.The fatigue strength prediction models, particularly representing S-N relationships, have been examined and the material coefficients have been obtained for PFRPCC containing different weight fractions of fibres. Furthermore, using Weibull distribution, probability of failure has been incorporated into the fatigue life data of PFRPCC to develop S-N-Pf relationships, both graphically and analytically. The two million cycle endurance limits for PFRPCC containing different amounts of fibres have also been obtained.
Keywords: polymer concrete composites; fatigue; statistical properties/methods; Weibull distribution; probability of failure.
A new simple formulation for instantaneous coil diameter of a SMA helical spring
by Santhanam Ranganathan, M.S. Sivakumar, Y. KRISHNA
Abstract: Helical coil tension springs made of shape memory alloy (SMA) materials generally undergo large deflection under loading, during which their mean coil diameter changes noticeably. In the design of these helical coil springs, it is necessary to identify the real behaviour which may be affected by the variation in actual coil diameter. Therefore, a simple formulation is proposed in this paper for predicting instantaneous coil diameter. The predictions from the present formulation match very closely with experimental measurements. The proposed formulation is relatively easy to adopt for design calculations. The effects of varying coil diameter on the spring characteristics are also discussed. This is very general and can be used for any helical spring that undergoes small or large deflections, although the proposed formulation is derived for an SMA helical spring.
Keywords: shape memory alloy; SMA; helical coil tension springs; instantaneous coil diameter; large deflection.
Effects of two-step heat treatment on the structure of cotton-derived activated carbon fibres
by Tsuyoshi Yoda, Keita Shibuya, Kazuma Miura, Hideki Myoubudani
Abstract: Activated carbon fibres (ACFs), a novel material, has attracted considerable research attention. The pore structures found on the surfaces of ACFs are strongly related to their functionality. Herein, ACFs were prepared via a two-step thermal treatment of cotton. The diameters and width distributions of thus-prepared ACFs were characterised using scanning electron microscopy (SEM). SEM analysis also revealed that the pore structures on the surfaces of the cotton-derived ACFs were activated by carbon dioxide. Successful adsorption functionality of these ACFs was characterised using a methylene blue solution. The effects of the two-step thermal treatment and potential applications of this methodology are also discussed. The proposed method can be used on other fibre products or industrial waste materials generated during the manufacture of cloth and fibres, and the generated ACFs can be used for energy-storage applications.
Keywords: activated carbon fibre; scanning electron microscope; thermal treatment; activation; pore structure; methylene blue; adsorption; cotton.
Compressive strength enhancement of concrete using fly ash as a partial replacement of fine aggregate and model development
by H.M.A. Mahzuz, Md. Jahid Hasan
Abstract: Fly ash is well known as a Supplementary Cementitious Material (SCM) and for its very fine well-rounded particles. Miniature gaps left in the concrete affect the concrete adversely. Fly ashs miniature and well-rounded shape can easily fill these gaps additionally offering some extra binding. The aim of this study was to use fly ash as a percentage of fine aggregate (FA). To observe the effect on a number of variations, three weight based ratios 1:1.25:2.5, 1:1.5:3 and 1:2:3 have been considered. For each ratio the fly ash varied as 0%, 10%, 20% and 30% of the FA. The curing period has been set at 28 days. The water-cement ratio (W/C) has been kept constant at 0.5. After going through all the processes and procedures the resulting data have revealed that the optimum compressive strength of the concrete lies at 10% of fly ash content. A nonlinear relationship has been perceived within the resulting compressive strength and elasticity varying with different fly ash quantity. Finally a nonlinear regression model has been suggested to mathematically describe the findings.
Keywords: concrete; fly ash; compressive strength; elasticity; nonlinear regression.
Mechanics of contact interaction and deformation of main pipelines in the conditions of extreme external actions
by Nikolay Makhutov, Mikhail Gadenin, Alexander Cherniavsky, Oleg Cherniavsky, Vladimir Nadein
Abstract: Formulation and solution of a task for the composite engineering-geological interacting of a pipeline and a soil are considered. Finite element method is used for numerical analysis of the task, accounting for large displacements and corresponding strains under changing boundary conditions. The capability of the limit state reaching in the pipeline with loss of form stability is shown to depend on the pad layer and the pipe properties. It is demonstrated also that safety maintenance could be provided by usage of ribs, formed on a pipe by a cyclic thermomechanical actions.
Keywords: structural material; deformation; strength; contact interaction; pipeline integrity; seismic steadiness; modeling; finite element method.
Changing the physical and chemical properties of alkaline soil stabilised with industrial waste material tile dust
by Jasbir Saini, Dharmender Kumar Soni, A.K. Mandal
Abstract: Various construction and post-construction damages have been reported in various research works concerning alkaline soil, owing to its irregular behaviour, especially its lower bearing capacity in natural conditions. Further, the soil strength gets decreased on soaking. In Haryana, alkaline soil deposits occur in extensive areas, which are related to certain geotechnical issues such as collapse upon wetting and susceptibility to strength loss. Owing to these characteristics, some of the roads constructed on alkaline soils in Kurukshetra have worsened because of cracking and ravelling. The important objective of this research work is the improvement of the load-bearing capacity of roads constructed on Kurukshetra alkaline soils by tile dust. Soil samples from the Pehowa-Kurukshetra road were collected and tested for enhancement of their properties by tile dust at different dosages ranging from 2 to 12%. The evaluation of the load-bearing capacity of stabilised soil mixtures is done using standard Proctor tests, performed to evaluate the compaction behaviour. The test results indicated that the maximum dry density gets minimised and the optimum moisture content gets increased with the supplementary admixture. Other tests, including the California Bearing Ratio test (CBR) and unconfined compression tests (UCS), are done for evaluating the strength properties of alkaline soil. Chemical tests due to the reaction in submerged conditions were performed in CSSRI lab in Karnal Haryana, and the following tests for pH, ECe, sodium, potassium, calcium, and magnesium were performed in saturated and submerged conditions after 30 days. These samples are put in a container for 30 days in both conditions to evaluate the chemical changes due to admixing of tile dust in alkaline soil. The test results specify that the tile dust significantly enhances the performance of the soil. Thereby, the improved soil is used as a good sub-base in flexible pavements in construction work.
Keywords: alkaline soil; stabilisation; industrial and agricultural waste.
Numerical investigation of the effect of fibre volume fraction on the stress distribution of aerospace grade Al-Li 8090 metal matrix Composite
by Dineshsingh G. Thakur
Abstract: The response of the fibre-reinforced metal matrix composite under tensile loading during micromechanical study is the key significance for analysing the metal matrix composite material behaviour. The present study deals with the Representative Volume Element (RVE) of aerospace grade Al-Li (8090) matrix alloy reinforced with SiC fibres in order to assess the stress distribution around the SiC fibres of SiC/Al-Li 8090 metal matrix composite subjected to the load in transverse and longitudinal direction. Square and hexagonal arrays of RVE has been used for this study. The deformation of the RVE and stress distribution around the fibres has been examined for 5% to 25% volume fraction of SiC fibres. It is observed that, for constant transverse loading, stress transfer between matrix and fibre decreases with increment in fibre volume fraction for square array, whereas stress transfer between matrix and fibre is observed even with increment in fibre volume fraction for hexagonal array. In the radial direction of SiC fibres, 5% volume fraction of the SiC fibres shows the maximum longitudinal stress. Longitudinal stress decreases, as increment in the fibre volume fraction of SiC for square and hexagonal arrays of RVE.
Keywords: Al-Li (8090) alloy; SiC fibre; metal matrix composite; representative volume element; finite element method.
Effect of surface modification on the thermal stability and nano-mechanical behavior of ZrO2 reinforced PMMA nanocomposite
by Himel Chakraborty, Nandagopal Bhowmik
Abstract: The poly(methyl methacrylate)-based composites are potential engineering materials. The scratch resistance of polymer composites is highly influenced by reinforcement type. The present study was based on the zirconium dioxide-poly(methyl methacrylate) composites with surface modification of zirconium dioxide by using methacryloxypropyltrimethoxysilane. The effects of zirconium dioxide functionalisation on curing kinetics and thermal degradation behaviour of the composites were examined by dynamic mechanical analysis and thermal gravimetric analysis measurements. The tribological and nano-mechanical behaviour of the composites was estimated, and the deformed surfaces during the scratching were examined by scanning electron micrography.
Keywords: nanocomposites; thermal stability; nanoindentation; scratch.
Effect of cryotreated electrodes on the machining efficiency of titanium alloy during electro discharge machining: a comparative study
by Munmun UNMUN Bhaumik, Kalipada Maity
Abstract: Electro discharge machining (EDM) is one of the most promising non-conventional machining processes. It can machine any conductive material irrespective of its hardness because there is no direct contact between workpiece and tool. Cryotreatment is introduced in the machining field to boost the tool life as well as to lessen the production cost. In the present study, a comparison study has been performed on EDM of titanium grade 6 alloy using untreated and cryotreated double tempered brass, copper and zinc electrodes. The EDM efficiency has been measured by means of tool wear rate (TWR), surface roughness (Ra), radial overcut (ROC) and material removal rate (MRR); peak current, duty cycle, pulse on time, gap voltage are considered as control parameters. A metallographic study has been done for the untreated and cryotreated electrode surfaces. Lower MRR, TWR and better precision of machined surface can be achieved using cryotreated electrodes than that of untreated electrodes. The surface machined by cryotreated electrodes provides a better surface finish than the surface machined by untreated electrodes. A microstructural analysis has been performed for the electro discharge machined surfaces.
Keywords: cryotreatment; electro discharge machining; material removal rate; surface roughness; tool wear rate.
Experimental investigation of surface-mounted optical fibre strain sensor using neural network analysis
by Ashwarya Sheel Wali, Amit Tyagi
Abstract: This study aimed to develop a smart neural network preceptron model for strain prediction using fibre optic sensors signals. Optical parameters corresponding to surface mounted optical fibre are obtained experimentally under static loading conditions. Four variations are used by creating external damage to study strain variations on healthy, single damage and multiple damage beam structures. The strain values are obtained by using phase difference and change in intensities data as input for feed-forward back propagation neural network model. A comparative study of pre-existing analytical solution, conventional strain gauge measurement, and finite element analysis is performed. The neural network model provides more accurate correlation results with strain gauge and FEA analysis compared to analytical analysis.
Keywords: optical parameters; neural network; finite element analysis; strain.
Shear surface wave propagation in stratified media with slip interfaces
by Karen Ghazaryan, Valentin Mozharovsky, Samvel Sarkisyan, Sergey Ohanyan
Abstract: The surface shear wave propagation is studied in elastic semi-spaces separated by an elastic layer with an imperfectly bonded interface between layer and semi-spaces. The dispersion equations are obtained analytically describing the surface wave phase speed. Based on the dispersion equation analysis it is shown that the interface imperfectness sufficiently decreases the phase speed and can also increase the number of shear wave modes.
Keywords: surface waves; shear waves; imperfect contact; slip model; dispersion.
Risk analysis of jacket platform structure based on failure probability of fatigue damage and collapse
by Yuan Liu, Zhiqiang Lian, Shengli Wan, Shunying Ji
Abstract: The risk inspection for offshore jacket platform structures should be performed in a planned schedule to ensure its safety and to reduce the inspection cost. Therefore, the Risk Based Inspection (RBI) technology has been a hot issue in offshore engineering. In this study, the finite element method is adopted to analyse the fatigue damage and the collapse failure of jacket platforms. The fatigue failure probability of the key members of platform structure will be determined based on the reliability theory. Meanwhile, the collapse failure probability of the platform structure will be analysed when the key members are failing. The risk matrix will be calculated with the results above for the platform to draw up the inspection plan. Finally, the risk assessment of one jacket platform in the South Sea of China is performed quantitatively. The risk matrix of key points and members is generated to work out the inspection target and plan. This study can be aided to determine the inspection plan for jacket platform reasonably and efficiently. The operation cost will be reduced under the safe operation conditions for platform structure.
Keywords: jacket platform structure; risk based inspection; risk assessment; collapse failure; fatigue damage.