International Journal of Materials and Structural Integrity (24 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
Higher-order Hermite-enriched contact finite elements for adhesive contact problems
by Vishal Agrawal, Sachin Singh Gautam
Abstract: It is known that during the simulation of the adhesive contact problems
highly non-linear responses of interaction forces occur within the very narrow
adhesive zone. It leads to the loss of quadratic-rate of convergence during Newton-
Raphson iterations and unstable computational behaviour. In the case of standard
finite element formulation, a very fine mesh resolution is needed for the stable
computations, but a significant computational cost is associated. For minimising
the cost without the loss of accuracy of the solution, contact surface enrichment
approaches have been presented. These approaches use the higher-order
Lagrangian polynomial functions for the enrichment of contact finite elements. In
the present work, based on the incorporation of fifth- and seventh-order Hermite
interpolation functions, two new enriched-contact finite elements are formulated.
The performance of proposed enriched-contact finite elements is demonstrated
through the simulation of peeling of an initially flat deformable strip from a rigid
substrate. A stable solution is obtained at a relatively coarser mesh than the fully
Lagrangian discretised finite element mesh. It is shown that the proposed higher order
Hermite enriched-contact finite elements attain better performance when
compared with earlier introduced enriched elements.
Keywords: adhesion; computation contact mechanics; enriched finite elements;rnnonlinear finite element analysis; Hermite polynomials.
Nonlinear analysis of FGM plates using generalized higher order shear deformation theory
by Srividhya Singam, Basant Kumar, R.K. Gupta, Rajagopal Amirtham
Abstract: In the present work a generalised higher order shear deformation theory (GHSDT) for the flexural analysis of the functionally graded plates subjected to uniformly distributed load of varying intensities has been formulated. A finite element formulation with a confirming type isoparametric approximation has been formulated and implemented. Various types of boundary condition have been considered for the analysis. The formulation accounts for geometric nonlinear terms in the strains. The formulation also complies with plate surface boundary conditions and does not require shear correction factors. The formulation has been validated by comparing the results with those available in the literature. Numerical results for different load parameters, volume fractions, and boundary conditions have been presented and compared with literature. Results show that the proposed GHSDT gives a better approximation to transverse shear strains, and the results are closer to those obtained from analytical solutions.
Keywords: functionally graded plates; nonlinear analysis; GHSDT; rule of mixtures; power law.
Effect of obliquity on ballistic impact response of plain-woven fabric
by Kuldeep Yadav, Ashutosh Kumar Upadhyay, Karunesh Kumar Shukla
Abstract: This numerical study presents the effect of obliquity on ballistic impact response of plain-woven fabric. A numerical model of plain-woven fabric subjected to a high-velocity impact at yarns crossover is simulated with the help of commercial finite element tool ABAQUS. The FE analysis depicts that the ballistic impact response of plain-woven fabric largely depends on the obliquity of impact owing to phenomena such as uneven strain distribution in different directions and sliding of the projectile on woven fabric yarns about the point of impact. The total energy dissipated by the fabric showed a decreasing-increasing behaviour with an increase in obliquity. This transition in the trend of total energy dissipated by fabric came in between 30o 45o, depending on the relative dominance of sliding of yarn and uneven strain distribution.
Keywords: plain-woven fabric; ballistic impact; obliquity; Kevlar.
Effect of soot on tribological properties of steel and ceramic contacts
by Yadvendra Kaushik, P. Ramkumar
Abstract: The present study aims to understand the effect of soot on tribological properties using different tribo-couples of bearing steel, silicon nitride and zirconia. The present test programme is performed using a pin-on-disc tribometer with LVDT, temperature and friction transducers. All tests are carried out at a sliding speed of 5 m/s and contact stress of 2.05 GPa to simulate a typical valve-train operation condition in a diesel engine. Commercially available heavy-duty diesel engine oil is used as lubricating oil. Friction and wear results are studied at different concentrations of soot. Silicon nitride showed the lowest friction and wear against the bearing steel amongst the all tribo-couples. Post-test analysis is carried out using optical microscopy and SEM with EDX of the worn surfaces of the pin materials to identify the wear mechanisms. Abrasive wear mechanism was found to be the primary wear mechanism for all tribo-couples. A delamination wear mechanism is proposed for zirconia in the presence of soot contamination.
Keywords: ceramic; friction; soot; wear; zirconia.
Mixed mode stress intensity factors of slanted edge cracked plate with hole subjected to various in-plane loadings using XFEM
by Khubilal Khatri, Achchhe Lal
Abstract: This manuscript presents the fracture behaviour of a slanted edge cracked plate with a circular hole subjected to various in-plane loadings, such as tensile, shear and combined (tensile and shear) loadings, through the mixed mode stress intensity factors (MMSIF). There is a lack of work in the direction of calculating the fracture behaviour of the slanted crack under the influence of a hole subjected to the various in-plane loadings. In this work, the crack is modelled using extended finite element method (XFEM) under plane strain condition using MATLAB. The MMSIFs are increased with the increment in the crack length, but as the crack angle is increased the Mode-I SIFs are decreased whereas the Mode-II SIFs are increased. The SIFs are critical for the plate with a hole compared with the plate without a hole. The values of MMSIFs are the highest for the plate under combined loading and the least under tensile loading.
Keywords: XFEM; MMSIF; slanted edge crack; plate with a circular hole; in-plane loadings.
Crystal plasticity-based creep model for solution-strengthened nickel-based alloys
by Pritam Chakraborty, Wen Jiang
Abstract: Nickel-based alloys are widely used in high temperature applications owing to their favourable properties at extreme conditions. However, owing to their high cost, efforts are being relentlessly made to extend the useful life of the components made from these alloys. Such life extension requires reliable constitutive models with detailed quantitative understanding of the factors contributing to property variations. Micromechanical analysis along with multi-scale methods can be a key enabler in developing the required high fidelity models. Particularly for properties, such as creep, that require long term prediction, accelerated tests with empirical models may prove insufficient. Thus, in the present work, a crystal plasticity-based creep model has been developed for solution strengthened nickel-based alloys. Through this model, the effect of microstructural variations in grain orientation, size, etc. on the secondary creep strain rate can be captured. The performance of the model is evaluated against creep data of alloy 617.
Keywords: crystal plasticity; creep; finite element method; alloy 617.
Wavelet-based finite element simulation of guided waves containing harmonics
by Ambuj Sharma, Sandeep Kumar, Amit Tyagi, Kumar Kaushik Ranjan
Abstract: This paper presents a promising numerical scheme for simulation of many harmonics in wave propagation. The wavelet-based adaptive technique eliminates the requirement for a very large number of nodes in the finite element method for propagation of such waves. This dynamic adaptive grid selection is based on the fact that very few wavelet coefficients are required to represent a short pulse containing higher harmonics. The method is particularly useful where higher harmonics are ignored owing to very high computational cost. In this work, B-spline and Daubechies wavelets-based non-standard (NS) multi-scale operators are applied, and the results are compared with the finite element method.
Keywords: non-standard wavelet operator; finite element method; higher harmonics; Lamb wave; structural health monitoring.
A new 3D finite element for the finite deformation of nearly incompressible hyperelastic solids
by Ashutosh Bijalwan, Badri Prasad Patel
Abstract: Volumetric locking is exhibited by nearly incompressible solids such as rubber, resulting in over-stiffening response of the finite element mesh. In this work, we develop the displacement-based computationally efficient volumetric locking free 3D finite element using smoothing of determinant of deformation gradient (J-bar method) within the framework of isotropic hyperelasticity. The developed methodology is employed to analyse a rubber block undergoing finite stretch and bending deformations. The convergence study for finite stretch and bending of the rubber block is presented. Results of the analysis show that the J-bar method efficiently removes the volumetric locking.
Keywords: incompressible; locking; finite deformation; J-bar method; neo-Hookean rubber.
Filler shape and volume fraction effect on dynamic compression behaviour of glass filler reinforced epoxy composites
by Sarthak S. Singh, Venkitanarayanan Parameswaran, Rajesh Kitey
Abstract: The effect of filler shape and volume fraction on the dynamic compression behaviour of low volume fraction rigid particle filled polymer composites is demonstrated by performing experiments using split-Hopkinson pressure bar (SHPB) setup. The results indicate negligible influence of spherical particles on the mechanical behaviour of composites owing to the large inter-particle separation distance at low volume fractions. On the contrary, the mechanical behaviour of composites is considerably affected by milled-fibres owing to the large surface area to volume ratio of slender fillers, which significantly decreases the inter-particle separation distance. The computational analysis in combination with experimental observations reveals two competing deformation mechanisms, the constraints provided by fillers to the polymeric chain movements and increasing strain softening in the matrix due to magnified stresses in between the particles. Depending upon the filler volume fraction, one of the two mechanisms dominates, thus tailoring post-yield stress vs. strain curves of filled polymers.
Keywords: particulate reinforced epoxy composite; dynamic compression; Split Hopkinson’s pressure bar.
Numerical investigation of crack growth in AISI type 316LN stainless steel weld joint using GTN damage model
by Namburu Sai Deepak, C. Lakshmana Rao, S.A. Krishnan, G. Sasikala, Raghu V. Prakash
Abstract: Ductile crack growth in austenitic 316LN stainless steel weld joint has been studied using FEA simulations with Gurson-Tvergaard-Needleman (GTN) damage model. The material specific GTN damage parameters are assessed and calibrated based on coupled experimental and numerical simulations for tensile and compact tension specimens. The influence of initial crack tip at various locations across the weld thickness has been analysed using CT geometry. The simulated results reveal that the crack propagates along the initial crack line for centrally located welds and deviates from the crack line for interfacial welds.
Keywords: 316LN SS Weld joint; numerical simulation; Gurson-Tvergaard-Needleman damage model; crack propagation behaviour; equivalent plastic strain; void volume fraction.
Comparative study of algorithms to handle geometric and material nonlinearities
by Shantanu Mulay, R. Udhayaraman, M. Anas
Abstract: It is critical to handle geometric and material nonlinearities in a stable manner while solving the problems from solid mechanics, such that it results in a converged solution. The present work compares the suitability of generalised displacement control (GDC) and displacement control algorithms (DCA) by solving several 1D and 2D formulations. The ability of these algorithms to handle homogeneous and inhomogeneous deformations is also studied. A novel direct displacement control method (DDCM), coupled with Newton-Raphson method, is proposed and compared with GDC and DCA approaches. Appropriate conclusions are finally drawn based on the successful demonstrations of the numerical results obtained by GDC, DCA and DDCM approaches.
Keywords: direct displacement control method; generalised displacement control.
Triaxial tests on weak planes damage of hard brittle shale of Longmaxi formations in south Sichuan Basin,China
by Yi Ding, Xiangjun Liu, Wei Zeng
Abstract: In the petroleum field, rock mechanical properties are a significant parameter for design of drilling operations. Shale formation has a high risk of wellbore instability in drilling. To reduce this risk, more investigations on shale should be conducted. Therefore, in this paper, by using X-ray diffraction and electron microscope scanning test, the mineral composition and microstructure of brittle shale of the Longmaxi formation have been analysed. Based on the triaxial compression tests, rock mechanical parameters in variable time have been discussed when shale is in the external force condition. In particular, considering shale failure along a weak plane, change laws of shale mechanical properties, such as stress, strain, structure integrity and elastic parameters, have been analysed. This work offers comprehensive exploration on shale mechanical properties. Mechanical parameters of shale in this study can provide reference for engineering design, and more importantly, establish the foundation for investigation of rock damage in the future.
Keywords: shale; triaxial tests; rock mechanics; weak plane damage.
Environment friendly milling of Inconel-625
by Pragat Singh, J.S. Dureja, Harwinder Singh, Manpreet S. Bhatti
Abstract: Inconel 625, having wide industrial applications, exhibits poor machinability because of rapid work-hardening and poor thermal conductivity. Therefore, cutting fluids are used to remove heat and provide lubrication in the cutting zone, but their application poses serious environmental and health hazards, hence the need to minimise their use. The nanoparticle-based minimum quantity lubrication (NMQL) technique provides an effective alternative to flooded cooling-machining of Inconel and stainless steel. The current study evaluates the performance of NMQL in terms of tool wear and surface finish during face milling of Inconel 625. To enhance thermal conductivity of MQL, soluble multi-walled carbon nanotubes (1% wt.) were mixed in vegetable oil. Cutting parameters were optimised to minimise tool wear and surface roughness, and validation tests were also conducted under flooded and dry conditions to compare their performance with NMQL machining. The performance of the cutting tool during NMQL machining was found to be 15.56% and 3.45% better than dry and flooded machining, respectively, on the basis of tool wear and 14.06% and 59.02% improved over flooded and dry machining, respectively, in terms of surface roughness.
Keywords: Inconel 625; face milling; minimum quantity lubrication; nanoparticle-based minimum quantity lubrication; multi-walled carbon nanotubes; tool wear; surface roughness; environment friendly machining.
Modelling and characterization of a magneto-rheological elastomer isolator device under impact loadings using interpolated multiple adaptive neuro-fuzzy inference system structure
by Mohd Sabirin Rahmat, Khisbullah Hudha, Zulkiffli Abd Kadir, Nur Rashid Mat Nuri, Noor Hafizah Amer, Shohaimi Abdullah
Abstract: This paper presents the modelling and characterisation of a magneto-rheological elastomer isolator device (MREID) under impact loading using the adaptive neuro-fuzzy inference system (ANFIS) technique. The characterisation of an MREID under impact loading was performed using an impact pendulum test rig, and the data obtained from the experimental work was processed in the form of force-velocity and force-displacement characteristics. In order to predict MREID behaviour in simulation analysis, multiple ANFIS models were proposed. A single ANFIS model was represented as a single kinetic energy produced by the impact mass used in experimental work. The experimental data was then used to train the ANFIS in predicting MREID behaviour and validating its performance. For verification, the prediction model, a parametric model (namely, the modified Bouc-Wen model) was developed, and the models were compared. The proposed interpolated multiple ANFIS model predicted the behaviour of the MREID with a high level of accuracy. The proposed model produced a better prediction than the modified Bouc-Wen model.
Keywords: magnetorheological elastomer; isolator device; impact loading; ANFIS; Bouc-Wen MRE modelling.
Factors influencing the interference of inner surface parallel biaxial cracks in thick-walled pipes
by Xiaofeng Qin, Feng Li, Xingguo Zhao
Abstract: The present work provides insights into the factors that influence the interference of inner surface biaxial cracks in a thick-walled cylinder under internal pressure by the finite element method. An interaction impact factor λ is defined based on theoretical formula of stress intensity factor of a single axial crack and factors such as angles, ratio of crack length to wall thickness, and ratio of outer diameter to wall thickness, which probably have an effect on the interference of two parallel axial cracks. The present work reveals there is a critical angle determining the closure and opening effect between the biaxial cracks. When the angle between biaxial cracks is larger than the critical value, the opening effect will be strengthened with the increase of angle, ratio of crack length to wall thickness, and ratio of outer diameter to wall thickness. The closure effect will be strengthened with the increase of angle, ratio of crack length to wall thickness and ratio of outer diameter to wall thickness when the angle between the biaxial cracks is smaller than the critical value.
Keywords: stress intensity factor; biaxial cracks; interaction impact factor; thick-walled pipe.
Study on the adsorption of methylene blue by NaOH KH550 modified bagasse
by Xuanjun Dai, Jiyuan Zhu
Abstract: The chemical composition, thermal stability and crystallinity of NaOH/KH550 modified bagasse were studied using the infrared spectroscopic analysis, thermogravimetric analysis and x-ray diffractometry. After modification, the hemicellulose was removed and KH550 was grafted onto the surface of the bagasse fibre effectively. Then, the modified bagasse was used as the adsorbent of methylene blue (MB) for the adsorption study. According to the results, the initial concentration of MB ranged from 10 to 200 mg/L at room temperature (25 ℃). The removal rate of MB could reach 94% under the conditions of adsorbent dosage greater than or equal to 4 g/L, solution pH from 8 to 12 and an adsorption time longer than 60 minutes. Furthermore, the adsorption isotherm model and adsorption kinetic model of modified bagasse for MB were studied, and the results showed that the adsorption isotherm accorded with the Freundlich model and the adsorption kinetic model accorded with a pseudo-second-order kinetic equation.
Keywords: bagasse; coupling reagent; characterisation; methylene blue; adsorption.
Cyclic electromechanical response of poly(vinylidene fluoride)
by Lambadi Harish, C. Lakshmana Rao
Abstract: In this study, we present the results of cyclic electromechanical experiments conducted on uniaxially stretched poly(vinylidene fluoride) (PVDF) films. The experiments were carried out over a range of applied displacement amplitudes, ranging from 0.5 mm to 1.5 mm, superposed on an initial stretch on the test samples. The strains were calculated using a non-contact speckle monitoring method. The hysteresis plots of mechanical and electromechanical cyclic responses are presented. Stress relaxation was observed up to 70% in the orthogonal to stretch direction and 16% in the stretch direction. Observed piezoelectricity along both the directions are reported and discussed in the paper.
Keywords: PVDF; cyclic loading; non-contact speckle method; electromechanical response; piezo sensor.
Effect of high temperature on fly ash based alkali-activated concrete compared with Portland cement concrete
by Sonal Thakkar, Urmil Dave, Jay Patel
Abstract: Sustainability and durability of concrete structures is an issue in todays world. This paper presents comparative study of effect of high temperature on fly ash based alkali-activated concrete, activated with sodium based activators and Ordinary Portland cement concrete for same grade. Residual compressive strength, split tensile strength, flexural strength, bond strength and modulus of elasticity were evaluated for both concrete at temperatures of 27
Keywords: high temperature; alkali activated concrete; fly ash; ordinary Portland cement concrete; residual mechanical properties.
Experimental characterisation of leaks through elastomermetal interface
by Sri Krishna Sudhamsu Kambhammettu, Lakshmana Rao Chebolu, Abhijit Deshpande, Jithin Devan
Abstract: Elastomeric seals are devices that are widely used to prevent fluid leakage through the interface of mating parts. In this paper, we study the leak characteristics of a representative elastomeric seal system using an experimental setup that has been developed to measure the leak rate of gas through an elastomer-metal interface as a function of sealing load intensity and fluid pressure. These experiments are carried out on Nitrile Butadiene Rubber (NBR), Hydrogenated Nitrile Butadiene Rubber (HNBR) and Fluoro-elastomer (FKM) specimens using nitrogen gas at pressures ranging from 40 kPa to 800 kPa. The experiments revealed that the leak rate increases rapidly with gas pressure and decreases with sealing load intensity. When leak rate was plotted against normalised gas pressure, it was observed that all the data points fall reasonably on one single curve irrespective of sealing load intensity and the material. These results will be useful for further analysis in developing a mathematical model for characterising fluid leak through elastomer-metal alloy interfaces.
Keywords: elastomeric; seals; leak; failure; elastomer-metal interface; prediction of leak; modeling; experimentation.
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.