Influence of material models on theoretical forming limit diagram prediction for Ti-6Al-4V alloy under warm condition

Forming limit diagram (FLD) is an important performance index to describe the maximum limit of principal strains that can be sustained by sheet metals till to the onset of localized necking. It offers a convenient and useful tool to predict the forming limit in the sheet metal forming processes. In the present study, FLD has been determined experimentally for Ti?6Al?4V alloy at 400 °C by conducting a Nakazima test with specimens of different widths. Additionally, for theoretical FLD prediction, various anisotropic yield criteria (Barlat 1989, Barlat 1996, Hill 1993) and different hardening models viz., Hollomon power law (HPL), Johnson?Cook (JC), modified Zerilli–Armstrong (m-ZA), modified Arrhenius (m-Arr) models have been developed. Theoretical FLDs have been determined using Marciniak and Kuczynski (M?K) theory incorporating the developed yield criteria and constitutive models. It has been observed that the effect of yield model is more pronounced than the effect of constitutive model for theoretical FLDs prediction. However, the value of thickness imperfection factor (f0) is solely dependent on hardening model. Hill (1993) yield criterion is best suited for FLD prediction in the right hand side region. Moreover, Barlat (1989) yield criterion is best suited for FLD prediction in left hand side region. Therefore, the proposed hybrid FLD in combination with Barlat (1989) and Hill (1993) yield models with m-Arr hardening model is in the best agreement with experimental FLD.

Prediction of fracture limits of Ni-Cr based alloy under warm forming condition using ductile damage models and numerical method

The stretch forming and the deep-drawing processes were carried out at 300 and 673 K to determine the safe forming and fracture limits of IN625 alloy.The experimentally obtained strain-based fracture forming limit diagram(FFLD)was transformed into a stress-based(σ-FFLD)and effective plastic strain(EPS)vs triaxiality(η)plot to remove the excess dependency of fracture limits over the strains.For the prediction of fracture limits,seven different damage models were calibrated.The Oh model displayed the best ability to predict the fracture locus with the least absolute error.Though the experimentally obtained fracture limits have only been used for the numerical analysis,none of the considered damage models predicted the fracture strains over the entire considered range of stress triaxiality(0.33<η<0.66).The deep drawing process window helped to determine wrinkling,safe and fracture zones while drawing the cylindrical cups under different temperature and lubricating conditions.Further,the highest drawing ratio of 2 was achieved at 673 K under the lubricating condition.All the numerically predicted results of both stretch forming and deep drawing processes using the Hill 1948 anisotropic yielding function were found to be good within the acceptable range of error.

An Exponential Shape Function for Wormholes in Modified Gravity

We propose a new exponential shape function in wormhole geometry within modified gravity.The energy conditions and the equation-of-state parameter are obtained.The radial and tangential null energy conditions,and also the weak energy condition are validated,which indicates the absence of exotic matter due to modified gravity allied with such a new proposal.

Einstein Energy-Momentum Complex for a Phantom Black Hole Metric

We calculate the energy distribution associated with a static spherically symmetric non-singular phantom black hole metric in Einstein＇s prescription in general relativity. As required for the Einstein energy-momentum complex, we perform the calculations in quasi-Cartesian coordinates. We also calculate the momentum components and obtain a zero value, as expected from the geometry of the metric.

FLRW non-singular cosmological model in general relativity

A singularity free cosmological model is obtained in a homogeneous and isotropic background with a specific form of the Hubble parameter in the presence of an interacting dark energy represented by a time-varying cosmological constant in general relativity. Different cases that arose have been extensively studied for different values of the curvature parameter. Some interesting results have been found with this form of the Hubble parameter to meet the possible negative value of the decelera- tion parameter （- 1/3≤ q 〈 0） as the current observations reveal. For some particular values of these parameters, the model reduces to Berman＇s model.

Wormhole solutions under the effect of dark matter in f(R,L_(m))gravity

In the background of f(R,L_(m))gravity,this work investigates three distinct dark matter halo profiles to test the possibility of generalised wormhole geometry within the galactic halo regions.The current study aims to accomplish these goals by examining various dark matter profiles including universal rotation curves(URC),Navarro-Frenk-White(NFW)model-Ⅰ,and NFW model-Ⅱinside two distinct f(R,L_(m))gravity models.According to the f(R,L_(m))=R/2+L^(a)_(m)model,the dark matter(DM)halo density profiles produce suitable shape functions that meet all the necessary requirements for exhibiting the wormhole geometries with appropriate choice of free parameters.In addition,to examine DM profiles under the f(R,L_(m))=R/2+(1+λR)L_(m) model,we consider a specific shape function.Further,we observed that the derived solution from both two models violates the null energy constraints,confirming that the DM supports wormholes to maintain in the galactic halo.

Dynamical system analysis of Dirac-Born-Infeld scalar field cosmology in coincident f(Q)gravity

In this article,we present a dynamical system analysis of a Dirac-Born-Infeld scalar field in a modified f(Q)gravity context.We considered a polynomial form of modified gravity,used two different types of scalar potential,polynomial and exponential,and found a closed autonomous dynamical system of equations.We analyzed the fixed points of such a system and evaluated the conditions under which deceleration to late-time acceleration occurs in this model.We note the similarity of the two models and show that our result is consistent with a previous study on Einstein s gravity.We also investigated the phenomenological implications of our models by plotting EoS(ω),energy density(Ω),and deceleration parameter(q)w.r.t.to e-fold time and comparing to the present value.We conclude the paper by observing how the dynamical system analysis differs in the modified f(Q)gravity,and present the future scope of our research.

Potential application of graphene oxide and Aspergillus niger spores with high adsorption capacity for recovery of europium from red phosphor,compact fluorescent lamp and simulated radioactive waste

The recovery of rare earth elements(REEs) is a global challenge and the mining of rare earths has serious environmental implications due to the toxic waste released post mining.Hence,the rising demand for rare earths and their far reaching electronic applications necessitates an effective strategy to recover the REEs from more viable sources.In this work,the graphene oxide-Aspergillus niger spores(GO-A.niger spores) blend was utilized for adsorptive recovery of a precious rare earth Eu(Ⅲ) and the adsorption variables like pH of the medium,adsorbent dosage,sorption kinetics,thermodynamics,and isotherm were optimized for the developed bioso rbent.The adsorption process suits the Langmuir isotherm model with a maximum adsorption capacity of 147.3 mg/g.The pseudo-second-order kinetics is a perfect fit to describe the adsorption process.The results obtained through the Van’t Hoff plot show negative free energy change(ΔG^(0)) which implies the spontaneity of the adsorption process.The negative standard enthalpy change(ΔH^(0)) values show that the nature of the adsorption process is exothermic.The analytical characterizations including Fourier transform infrared spectroscopy(FTIR),Raman,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Brunauer-Emmett-Teller(BET),thermal gravimetric analysis(TGA),and scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDX) were employed to study the biosorbent.The features of GO-A.niger spores biosorbent were applied to recover Eu(Ⅲ) from real samples such as fluorescent lamp phosphor,red phosphor powder,and a simulated radioactive waste solution.

Non-exotic static spherically symmetric thin-shell wormhole solution in f(Q,T)gravity

In this study,we conduct an analysis of traversable wormhole solutions within the framework of linear f(Q,T)=αQ+βT gravity,ensuring that all energy conditions hold for the entire spacetime.The solutions presented in this paper are derived through a comprehensive analytical examination of the parameter space associated with the wormhole model.This involves considering the exponents governing the redshift and shape functions,as well as the radius of the wormhole throat(r_(0)),the redshift function value at the throat(∅_(0)),and the model parameters(αandβ).Moreover,we establish bounds on these free parameters,which guarantee the satisfaction of the energy conditions throughout spacetime and also provide two solutions.Furthermore,we use the Israel junction condition to observe the stability of a thin-shell around the wormhole.Finally,we calculate the null energy condition criteria as well as the potential for the thin-shell and how it varies with the chosen shape function.

Cosmic acceleration with bulk viscosity in an anisotropic f(R, Lm) background

In this article,we investigate the observed cosmic acceleration in the framework of a cosmological f(R,Lm)model dominated by bulk viscous matter in an anisotropic background.We consider the locally rotationally symmetric Bianchi type I metric and derive the Friedmann equations that drive the gravitational interactions in f((R,Lm)gravity.Further,we assume the functional form f(R,Lm)=R/2+Lαm,where a is a free model parameter,and then find the exact solutions of field equations corresponding to our viscous matter dominated model.We incorporate the updated H(z)data and the Pantheon data to acquire the best-fit values of parameters of our model by utilizing theχ2 minimization technique along with the Markov Chain Monte Carlo random sampling method.Further,we present the behavior of physical parameters that describe the Universe’s evolution phase,such as density,effective pressure and EoS parameters,skewness parameter,and the statefinder diagnostic parameters.We find that the energy density indicates expected positive behavior,whereas the negative behavior of bulk viscous pressure contributes to the Universe’s expansion.The effective EoS parameter favors the accelerating phase of the Universe’s expansion.Moreover,the skewness parameter shows the anisotropic nature of spacetime during the entire evolution phase of the Universe.Finally,from the statefinder diagnostic test,we found that our cosmological f(R,Lm)model lies in the quintessence region,and it behaves like a de-Sitter universe in the far future.We analyze different energy conditions in order to test the consistency of the obtained solution.We find that all energy conditions except strong energy condition(SEC)show positive behavior,while the violation of SEC favors the recently observed acceleration with the transition from decelerated to an accelerated epoch of the Universe’s expansion in the recent past.

Slow-roll inflation in f(T,T)modified gravity

In this study, we explore the concept of cosmological inflation within the framework of the f(T, T)theory of gravity, where f is a general function of the torsion scalar T and the trace T of the energy-momentum tensor.It is assumed that the conditions of slow-roll inflation are applicable in f(T, T) gravity. To determine different observables related to inflation, such as the tensor-to-scalar ratio r, scalar spectral index ns, spectral index αs, and tensor spectral index nt, the Hubble slow-roll parameters are utilized for a particular model of f(T, T). Lastly, an assessment is carried out to determine the feasibility of the models by conducting a numerical analysis of the parameters. The findings indicate that it is feasible to achieve compatibility with the observational measurements of slow-roll parameters by utilizing different values of the free parameters.

Gravastar in the framework of symmetric teleparallel gravity

We present a novel gravastar model based on the Mazur-Mottola(2004)method with an isotropic matter distribution in f(Q)gravity.The gravastar,which is a hypothesized substitute for a black hole,is built using the Mazur-Mottola mechanism.This approach allows us to define the gravastar as having three stages.The first one is an inner region with negative pressure;the next region is a thin shell that is made up of ultrarelativistic stiff fluid,and we studied the proper length,energy,entropy,and surface energy density for this region.Additionally,we demonstrated the possible stability of our suggested thin shell gravastar model through the graphical study of the surface redshift.The exterior Schwarzschild geometry describes the outer region of the gravastar.In the context of f(Q)gravity,we discovered analytical solutions for the interior of gravastars that are free of any type of singularity and the event horizon.

Compact stars admitting Finch-Skea symmetry in the presence of various matter fields

In the present study,we investigate the anisotropic stellar solutions admitting Finch-Skea symmetry(viable and non-singular metric potentials)in the presence of some exotic matter fields,such as Bose-Einstein Condensate(BEC)dark matter,the Kalb-Ramond fully anisotropic rank-2 tensor field from the low-energy string theory effective action,and the gauge field imposing U(1)symmetry.Interior spacetime is matched with both Schwarzchild and Reissner-N?rdstrom vacuum spacetimes for BEC,KB,and gauge fields.In addition,we study the energy conditions,Equation of State(EoS),radial derivatives of energy density and anisotropic pressures,Tolman-OppenheimerVolkoff equilibrium condition,relativistic adiabatic index,sound speed,and surface redshift.Most of the aforementioned conditions are satisfied.Therefore,the solutions derived in the current study lie in the physically acceptable regime.

Thin-shell gravastar model in f(Q,T)gravity

In the last few decades,gravastars have been proposed as an alternative to black holes.The stability of a gravastar has been examined in many modified theories of gravity along with Einstein's GR.The f(Q,T)gravity,a successfully modified theory of gravity for describing the current accelerated expansion of the universe,has been used in this study to examine gravastar in different aspects.According to Mazur and Mottola[Proc.Natl.Acad.Sci.101,9545(2004);Gravitational condensate stars:An alternative to black holes,I12-011,(2002)],a gravastar has three regions with three different equations of state.In this study,we examined the interior of a gravastar by consid-ering p=-ρ EoS to describe the dark sector for the interior region.The next region is a thin shell of ultrarelativistic stiff fluid,in which we investigated several physical properties,including proper length,energy,entropy,and surface energy density.Additionally,we examined the surface redshift and speed of sound to check the potential stability of our proposed thin-shell gravastar model.Furthermore,we used the entropy maximization technique to verify the stability of the gravastar model.A gravastar's outer region is a complete vacuum described by exterior Schwarzschild geometry.Finally,we presented a stable gravastar model,which is singularity-free and devoid of any incom-pleteness in classical black hole theory.

Static spherically symmetric wormholes in f(Q,T)gravity

In this study,we obtain wormhole solutions in the recently proposed extension of symmetric teleparallel gravity,known as f(Q,T)gravity.Here,the gravitational Lagrangian L is defined by an arbitrary function f of Q and T,where Q is a non-metricity scalar,and T is the trace of the energy-momentum tensor.In this study,we obtain field equations for a static spherically symmetric wormhole metric in the context of general f(Q,T)gravity.We study the wormhole solutions using(ⅰ)a linear equation of state and(ⅱ)an anisotropy relation.We adopt two different forms of f(Q,T),(a)linear f(Q,T)=αQ+βT and(b)non-linear f(Q,T)=Q+λQ^(2)+ηT,to investigate these solutions.We investigate various energy conditions to search for preservation and violation among the obtained solutions and find that the null energy condition is violated in both cases of our assumed forms of f(Q,T).Finally,we perform a stability analysis using the Tolman-Oppenheimer-Volkov equation.

Anisotropic stars in modified gravity:An extended gravitational decoupling approach

In this study,we conduct an investigation on decoupling gravitational sources under the framework of f(R,T)gravity.Basically,the complete geometric deformation technique is employed,which facilitates finding the exact solutions to the anisotropic astrophysical system smoothly without imposing any particular ansatz for the deformation function.In addition,we used 5-dimensional Euclidean spacetime in order to describe the embedding Class Ⅰ spacetime in order to obtain a solvable spherical physical system.The resulting solutions are both physically interesting and viable with new possibilities for investigation.Notably,the present investigation demonstrates that the mixture of f(R,T)+CGD translates to a scenario beyond the pure GR realm and helps to enhance the features of the interior astrophysical aspects of compact stellar objects.To determine the physical acceptability and stability of the stellar system based on the obtained solutions,we conducted a series of physical tests that satisfied all stability criteria,including the nonsingular nature of density and pressure.

Synthesis and antimycobacterial screening of new N-(4-(5-aryl-3-(5-methyl-1,3,4-oxadiazol-2-yl)-1H-pyrazol-1-yl)phenyl)-4-amide derivatives

This article demonstrates the synthesis, characterization and the study of in vitro antitubercular activities of twenty four new N-（4-（5-aryl-3-（5-methyl-1,3,4-oxadiazol-2-yl）-1H-pyrazol-1-yl）phenyl）-4-amide derivatives（8a–x）. The antitubercular activity of the compounds against Mycobacterium tuberculosis H37Rv（MTB） revealed that 2-chloro-N-（4-（5-（4-chlorophenyl）-3-（5-methyl-1,3,4-oxadiazol-2-yl）-1H-pyrazol-1-yl）phenyl）benzamide（8n） is the most promising lead molecule with a MIC of1.56 mg/m L, while the corresponding unsubstituted benzamide derivative（8o） is the next most active molecule with a MIC of 3.13 mg/m L. Interestingly, the pyrazole intermediate 5b containing chlorophenyl and N-acylcarbohydrazide substituents also showed significant activity（MIC = 3.13 mg/m L）. Further, the active molecules did not show toxicity against a normal NIH 3T3 cell line, signifying their suitability for further drug development.

Energy conditions of the f(T,B) gravity dark energy model with the validity of thermodynamics

In this article, the analysis of Tsallis holographic dark energy(which turns into holographic dark energy for a particular choice of positive non-additivity parameter δ) in modified f(T, B) gravity with the validity of thermodynamics and energy conditions for a homogeneous and isotropic FLRW Universe has been studied. The enlightenment of the field equation towards f(T,B)=αT^m+βB^n, made possible by the fact that the model is purely accelerating,corresponds to q=-0.54(Mamon and Das 2017 Eur. Phys.J.C 77 49). The generalized second law of thermodynamics is valid not only for the same temperature inside the horizon, but also for the apparent horizon for a change in temperature. The essential inspiration driving this article is to exhibit the applicability that the holographic dark energy achieved from standard Tsallis holographic dark energy and the components acquired from f(T, B) gravity are identical for the specific bounty of constants. The analysis of energy conditions confirms that the weak energy condition and the null energy condition are fulfilled throughout the expansion, while violation of the strong energy condition validates the accelerated expansion of the Universe.With the expansion, the model becomes a quintessence dominated model. The dominant energy condition is not observed initially when the model is filled with genuine baryonic matter,whereas it appears when the model is in the quintessence dominated era.

Periodic cosmic evolution in f(Q)gravity formalism

We study the periodic cosmic transit behavior of the accelerated universe in the framework of symmetric teleparallelism. The exact solution of field equations is obtained by employing a wellknown deceleration parameter(DP) called periodic varying DP, q =m coskt-1. The viability and physical reliability of the DP are studied by using observational constraints. The dynamics of periodicity and singularity are addressed in detail with respect to time and redshift parameter.Several energy conditions are discussed in this setting.

A New Stable Algorithm to Compute Hankel Transform Using Chebyshev Wavelets

A new stable numerical method,based on Chebyshev wavelets for numerical evaluation of Hankel transform,is proposed in this paper.The Chebyshev wavelets are used as a basis to expand a part of the integrand,r f(r),appearing in the Hankel transform integral.This transforms the Hankel transform integral into a Fourier-Bessel series.By truncating the series,an efficient and stable algorithm is obtained for the numerical evaluations of the Hankel transforms of order ν>−1.The method is quite accurate and stable,as illustrated by given numerical examples with varying degree of random noise terms εθ_(i) added to the data function f(r),where θ_(i) is a uniform random variable with values in[−1,1].Finally,an application of the proposed method is given for solving the heat equation in an infinite cylinder with a radiation condition.