A multiscale phenomenological constitutive model for strain rate dependent tensile ductility in nanocrystalline metals

Acknowledgments No external funding was received for this project.Peer reviewedPostprin

A New Generating Family of Distributions: Properties and Applications to the Weibull Exponential Model

A new method for generating family of distributions was proposed. Some fundamental properties of the new proposed family include the quantile, survival function, hazard rate function, reversed hazard and cumulative hazard rate functions are provided. This family contains several new models as sub models, such as the Weibull exponential model which was defined and discussed its properties. The maximum likelihood method of estimation is using to estimate the model parameters of the new proposed family. The flexibility and the importance of the Weibull-exponential model is assessed by applying it to a real data set and comparing it with other known models

Wrinkling, creasing, and folding in fiber-reinforced soft tissues

Many biological tissues develop elaborate folds during growth and development. The onset of this folding is often understood in relation to the creasing and wrinkling of a thin elastic layer that grows whilst attached to a large elastic foundation. In reality, many biological tissues are reinforced by fibres and so are intrinsically anisotropic. However, the correlation between the fiber directions and the pattern formed during growth is not well understood. Here, we consider the stability of a two-layer tissue composed of a thin hyperelastic strip adhered to an elastic half-space in which are embedded elastic fibers. The combined object is subject to a uniform compression and, at a critical value of this compression, buckles out of the plane — it wrinkles. We characterize the wrinkle wavelength at onset as a function of the fiber orientation both computationally and analytically and show that the onset of surface instability can be either promoted or inhibited as the fiber stiffness increases, depending on the fibre angle. However, we find that the structure of the resulting folds is approximately independent of the fiber orientation. We also explore numerically the formation of large creases in fiber-reinforced tissue in the post-buckling regime

A variational constitutive model for soft biological tissues

In this paper, a fully variational constitutive model of soft biological tissues is formulated in the finite strain regime. The model includes Ogden-type hyperelasticity, finite viscosity, deviatoric and volumetric plasticity, rate and microinertia effects. Variational updates are obtained via time discretization and pre-minimization of a suitable objective function with respect to internal variables. Genetic algorithms are used for model parameter identification due to their suitability for non-convex, high dimensional optimization problems. The material behavior predicted by the model is compared to available tests on swine and human brain tissue. The ability of the model to predict a wide range of experimentally observed behavior, including hysteresis, cyclic softening, rate effects, and plastic deformation is demonstrated

Thermal vibration analysis of cracked nanobeams submerged in elastic foundations by nonlocal continuum mechanics

Funding information The authors declare that they do not receive any funds from any organization for this research.Peer reviewe

Review Multi Pass Friction Stir Processing

The aim of this article is to provide a review of multiple passes friction stir processing technology and their effect on the microstructure refinement, improving mechanical properties furthermore enhancement of reducing distortion and defects in materials. Multi-pass FSP achieves uniform dispersion of reinforcement particles in the metal matrix composites. The present paper reviews the work done in the above mentioned areas and concludes the effect of multi-pass FSP on the mechanical properties

Experimental and computational investigation of energy ball wind turbine aerodynamic performance

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by the British University in Egypt and the Center for Renewable Energy. Author contributions E.E. prepared this manuscript. This study was carried out under the supervision of N.E., A.A.A.F., and T.A.E.-S. All authors carried out data analysis, discussed the results, and contributed to writing the paper.Peer reviewedPublisher PD

Comparison between different methods of sonographic cervical length assessment during pregnancy

Background: Preterm birth is the presence of uterine contraction of sufficient frequency and intensity to effect progressive effacement and dilatation of cervix prior to term gestation (between 20 and 37 weeks). The objective of this study was to compare between the different methods of assessment of cervical length (Trans abdominal, trans vaginal, and transperineal) during pregnancy as a possible screening of preterm birth.Methods: Prospective cohort study was performed on 200 cases who attended at Elshat by hospital. At gestational age from 20 to 26 weeks, there was no significant difference regarding demographic data as (maternal age, parity). The route of examination was started according to urinary bladder fullness at admission. Accordingly, the patient was not instructed to void if she had full bladder, rather we started by transabdominal route. If she had empty bladder at the time she presented we started by transperineal then transvaginal route. The four measurements were compared to each other and the difference between them calculated. The selected sample size was found to be 200 pregnant women.Results: Transvaginal route gave the longest cervical measurements followed by transperineal route then abdominal route (full bladder) and finally tans abdominal route (semi-full bladder). Our results indicate that there is a significant positive correlation among the four methods of measuring cervical length in that gestational age.Conclusions: Tran-abdominal assessment could be used initially for cervical length screening, considering the maternal and fetal condition. Then, if the need arises, transvaginal sonography could be used. This step by step approach may be more convenient and useful to both patients and physicians for cervical length screening

Influence of strain gradients on lattice rotation in nano-indentation experiments: a numerical study

In this paper the texture evolution in nano-indentation experiments was investigated numerically. To achieve this, a three-dimensional implicit finite-element model incorporating a strain-gradient crystal-plasticity theory was developed to represent accurately the deformation of a body-centred cubic metallic material. A hardening model was implemented to account for strain hardening of the involved slip systems. The surface topography around indents in different crystallographic orientations was compared to corresponding lattice rotations. The influence of strain gradients on the prediction of lattice rotations in nano-indentation was critically assessed