Large deformation flexural behavior of laminated composite skew plates: An analytical approach

The paper presents the large deformation flexural response of composite laminated skew plates subjected to uniform transverse pressure. Third order shear deformation theory (TSDT) and von-Karman’s nonlinearity is used for the analysis. Skew domain is mapped into a square domain and finite degree double Chebyshev series is used to discretize the space domain. No grid generation is required in the present solution technique. The nonlinear equations are linearized using quadratic extrapolation technique and the behavior of moderately thick laminated composite skew plates is studied. The effects of geometric nonlinearity, transverse shear, boundary conditions, aspect ratio and modular ratio on the behavior of laminated composite skew plates are discussed in detail.     

High-Speed Friction Stir Welding of AA7075-T6 Sheet: Microstructure,Mechanical Properties,Micro-texture,and Thermal History

Friction stir welding (FSW) is a cost-effective and high-quality joining process for aluminum alloys (especially heat-treatable alloys) that is historically operated at lower joining speeds (up to hundreds of millimeters per minute). In this study, we present a microstructural analysis of friction stir welded AA7075-T6 blanks with high welding speeds up to 3 M/min. Textures, microstructures, mechanical properties, and weld quality are analyzed using TEM, EBSD, metallographic imaging, and Vickers hardness. The higher welding speed results in narrower, stronger heat-affected zones (HAZs) and also higher hardness in the nugget zones. The material flow direction in the nugget zone is found to be leaning towards the welding direction as the welding speed increases. Results are coupled with welding parameters and thermal history to aid in the understanding of the complex material flow and texture gradients within the welds in an effort to optimize welding parameters for high-speed processing.     

Comparative Study on Microstructural Characteristics and Compression Deformation Behaviour of Alumina and Cenosphere Reinforced Aluminum Syntactic Foam Made Through Stir Casting Technique

In order to examine the effect of microballoons type on microstructure and compressive deformation behaviour of aluminum syntactic foam, alumina reinforced and cenosphere reinforced aluminum syntactic foams have been made through stir-casting technique. Alumina microballoons reinforced aluminum syntactic foam (AMRASF) has been developed using stir casting technique. Volume fraction of alumina microballoons in AMRASF varies in the range of 0.39–0.74. The compressive deformation behavior of these AMRASF is compared with that of cenosphere reinforced aluminum syntactic foam (CPRASF). The AMRASF does not exhibit clear plastic collapse stage as observed in case of CPRSAF. It is further noted that AMRASF shows the existence of work hardening phenomena after yielding but CPRASF does not show any significant work hardening after yielding even at higher relative densities of foam. This is explained on the basis of characteristics of alumina microballoons and cenospheres and interface characteristics between matrix and respective microballoons used. Effect of individual microballoons’ characteristics on the foam properties has also been explained.     

Dodecylmethacrylate – olive oil copolymers as potential biodegradable pour point depressant for lubricating oil

The application of greener additives based on vegetable oils has attracted considerable interest due to their biocompatibility and enhanced additive performances compared to conventional additives. Keeping this view in mind and in continuation of our explorative studies on lube oil additives, copolymer of dodecylmethacrylate with olive oil have been synthesized in a focused mono-mode microwave oven using BZP (benzoyl peroxide) as radical initiator. Characterization of the prepared polymers has been performed by spectral (NMR, IR), and SEC-GPC analysis. Performance evaluation of the polymers as pour point depressant (PPD), and viscosity modifier (VM) / viscosity index improver (VII) in different base oils (mineral) have been performed by standard ASTM methods. Biodegradability of the prepared additives was tested against fungal pathogens and microorganisms by disc diffusion (DD) method and by soil burial test (SBT) method respectively. Thermal stability of each of them has been evaluated and included. The multifunctional performances have been compared and reported. The copolymers showed excellent PPD performance along with VM properties and potential biodegradability.     

Multifunctional biodegradable lube oil additives: Synthesis,characterization, and performance evaluation

Copolymers of different concentration of decyl acrylate and 1-decene with rice bran oil were prepared and their characterization was carried out by spectral (NMR, IR), thermogravimetric, and gel permeation chromatography analysis. Performance evaluation of them in lube oil indicates that the polymers effectively act as pour point depressant and viscosity modifier. The viscosity index and pour point values depend on the nature of mineral base oils, polymer type, and also on the concentration of the additives in solution. Biodegradability test was also carried out and as anticipated, the rice bran oil–copolymers showed excellent biodegradable nature among the additives.     

On the dynamic response of buried orthotropic cylindrical shells under moving load

This paper deals with the dynamic response of a buried orthotropic infinite cylindrical shell subjected to a radial line load moving along the shell axis. A thin shell theory formulation has been used and only axisymmetric response has been investigated. The shell is assumed to be perfectly bonded to the surrounding medium (soil) of infinite extent. Orthotropy parameters of the shell have been varied over a wide range to bring out their effects on the shell response. Results have been obtained for different soil conditions—hard, medium and soft.     

Removal of phenols by adsorption on fly ash

Adsorption of phenol and cresol and their mixtures from aqueous solutions on activated carbon and fly ash has been investigated. The effects of contact time and initial solute concentration have been studied and isotherm parameters are evaluated. The Freundlich isotherm has been found to be more suitable for all the systems investigated.     

Equivalent Homogeneous Variable Depth Beams for Cracked FGM Beams; Compliance Approach

We explore the compliance approach for K _I evaluation of a cracked three point beam (TPB) of functionally graded material (FGM). We suggest an equivalent beam of variable height for cracked FGM beams which includes the homogeneous beam for the linear, quadratic and cubic variations in elastic modulus along the beam span. The efficacy of equivalent beams is demonstrated numerically on a 250 × 41 × 6 mm FGM beam with modulus varying from 210 – 315 GPa under 5000 N load.     

Bayes interval for the Weibull parameters utilizing guessed estimates

In this paper an attempt is made to provide a method of obtaining the HPD-intervals for the scale and shape parameters of the Weibull distribution, when a prior distribution of the parameter places a weight (1 − b) on the guess value of the parameter and distributes the rest probability mass b according to some specified distribution. The equal tail credible intervals have been obtained and it is proposed that these limits be used as initial points for obtaining the HPD-intervals.