In this paper, economic analysis on the effect of polyester fibers with high strength on the behavior of Hot Mix Asphalt (HMA) is performed. The results indicate that strength is increased by adding fiber to asphalt. Also, unit weight of asphalt mixture was used as a variable parameter in the analyses. The results show that in some certain percentages of fiber, in addition to the enhancement in mechanical properties of HMA mixture the economic benefit value becomes more than the cost and therefore adding polyester fibers with high stability is suggested for the mixture of modified asphalt concrete. Finally, it can be concluded that adding fibers in values of 0.2% to 0.5% has the best result on the asphalt mixture, which because of high resistance and economic aspects makes it more efficient to be used in the highways of warm regions containing traffic.

Loosening of threaded joints, especially those operating under dynamic loading conditions, is a common and traditional problem for machines, mechanisms and structures. This study develops scientific approaches to the frictional lock of bolted joints to prevent unintentional self-unscrewing. An analytical version of the theory of threaded joint, which is equipped with a spring-loaded collet, is developed in the paper. The mixed contact problem of the interaction of the cyclic-symmetric system of the collet nut blades with the inner bolt and the outer spring, which is fitted with tightness, was set up and solved. In order to obtain analytical solutions to the problem, original one-dimensional models of structural elements of the connection were constructed. Based on the solutions of the contact problem, the moment of friction force is calculated from the initial gap between the blades and the thread, from the value of the spring tightness, from the parameters of the rigidity of the blade and the clamping spring. Finally, the value of the maximum friction torque that counteracts the self-unscrewing of the collet nut is evaluated, and some features of the threaded joint with the collet nut design are considered.

In this paper, experimental and numerical studies are performed to determine the maximum deflection and strength of cylindrical shells. The considered models are subjected to concentrated loads applied progressively until plastic failure of the structures. In order to determine the effect of the geometrical parameters, several models with different thicknesses, lengths, and radius are considered and analysed with various boundary conditions. The numerical analysis is carried out by the finite element method using ABAQUS code. The main objective of the present investigation is to determine the maximum strength that caused damage of the models. The results of the experimental and numerical analysis are recorded, discussed and commented on. It is observed that the thickness, length,and radius dimensions with boundary conditions have great effect on the strength load values that create damage.

In this study, an improved eight-node quadrilateral finite element based on a twice-interpolation strategy (TIS) is given for correctly modeling the singular stress field near 2D crack tip of structures. In present approach, the approximation functions for interpolation strategy are established by using the TIS which included nodal values as well as averaged nodal gradients respectively. The stress intensity factors (SIFs) are therefore calculated following the proposed method. The accuracy of the proposed element and its numerical solutions are described by several examples.

In order to study the behaviour of a notch specimen under plane mixed mode I +II, a Brazilian disc specimen weakened by U-notch located at the edge of disc is considered. A high-strength steel material was used for the disc specimen subjected to diametral compressive loading. A local approach represented by strain energy density approach based on determination of mean value of the strain energy density (that is over a given finite-size volume surrounding the highly stressed regions near the notch tip) was utilized. A finite element analysis by cast3m code have been undertaken in order to determine the evolution of the stress intensity factors and averaged strain energy density for different location of notch from the axis of force application. Variations of radius and angle of notch will cause disturbance in the stress field and local energy in the vicinity of the notch tip. The results of finite element computations were expressed as mathematical relations showing the influence of notch position and its radius on stress intensity factors and averaged strain energy density. The reduction of the angle increases the local energy unlike the increase of the radius tends to reduce it.

Fatigue crack growths of a corner crack emanating from a pinhole of a solid cylinder subjected to cyclic torsion loading were simulated using a Dual-Boundary Element Method (DBEM) based software. For a given crack aspect ratio a/c, larger Mode I stress intensity factor (SIF) was observed at a larger pinhole diameter. Any given initial crack aspect ratio a/c would evolve towards unity. The final evolving crack aspect ratio a/c was shown to be larger than 1. For the same given initial crack length a, a smaller crack depth c was found to result in a shorter fatigue life. A shorter fatigue life yielded a larger orientation angle of the crack growth path.

ABAQUS/Standard is a powerful finite element program designed for general use in nonlinear problems. The paper touches only one aspect of usage of the software, namely a constitutive modelling of slightly compressible hyperelastic materials. It begins with a discussion of a well-known approach of describing slight compressibility in the context of the stored energy function. Basic equations of continuum mechanics are presented as well. The main part of the work concerns an implementation of one of the presented models. To this end, the UHYPER user subroutine is employed. Analytical formulas for a few simple, homogeneous deformation states are given which allow verifying numerical results. Finally, a couple demonstration examples with nonhomogeneous deformations are presented as an attempt at motivating applications in engineering.

Synthesis of 2H and 3C-polytype silicon carbide nanowhiskers mixture of silicon dioxide and carbon was performed by carbothermal reduction process. The reaction temperature for synthesis of 2H-SiC was varied from 1350 C to 1650 C and for the 3C-SiC this range was varied from 1450 C to 1650 C. Scanning Electron Microscopy (SEM) analyses showed that nanowhiskers structures of both 2H-SiC and 3C-SiC polytypes has a size up to 100 nm in diameters and several microns in length. However, the orientation and pattern of grains were different in both structures. While for 3C-SiC polytype, the shape has been classified as SiC majorly grew along [101] plane by X-ray Diffraction pattern and finalized by Raman shift peaks at 799 and 959 cm-1, the shape of 2H-polytipe silicon carbide was categorized as SiC majorly grown along [111] plane confirmed by Raman shift peak at 799 and 963 cm-1. The mechanism of vaporgas interaction was also suggested and discussed for both SiC nanowhiskers polytypes.

Composites prepared by Single Wall Carbon Nano-tube (SWCNT) as well as Nylon assume a vital part in practical applications as in ultrastrong lightweight materials, vehicle and flying machine parts. In the present work, the influence of aspect proportion (l/d) on the longitudinal Young's modulus (E11) as well as transverse modulus (E22) for the SWCNT/Nylon 66 composite have been critically analyzed through utilizing tools of Molecular Dynamics (MD) simulations. Materials Studio 8.0 simulation software utilized in the current study for finding Young modulus. Aspect proportion (l/d) of used CNT in the composite was ranged from l/d = 5 up to l/d = 30 while the fraction of volume (Vf) of the CNT had been kept constant at 8%. Results demonstrated however that the lengthwise Young's modulus for the current composite increment essentially by expanding the aspect ratio (l/d) of Nano-tube while the change in transverse modulus with fluctuating perspective proportion was not exceptionally noteworthy. The results of the simulation have been consequently matched with the Mori-Tanaka model as well as the Finegan model.

Mastic mortar, i.e. a mixture of bitumen and very fine filler particles (i.e. aggregate fine particles smaller than 0.063 mm), can significantly co-influence not only rheological properties of the processed asphalt mixture, but also the visco-elastic properties of compacted asphalt layers including resistance against crack formation. Nevertheless, the number of scientific studies dedicated to this topic in detail, is very limited. The aim of this work is to determine the basic rheological properties of these mastic materials using a dynamic shear rheometer, in particular concentrating on the petrographic origin of the filler particles. Fourteen filler types were selected and mixed with paving bitumen 70/100 in various ratios. Petrographic composition of the individual fillers was determined using powder X-ray diffraction analysis. Attention was given especially to the effect of the presence of mica on the filler and mastic properties. Filler properties were analyzed using the voids of dry compacted filler test so-called "Rigden voids" and the delta ring and ball test. Mastic mortars prepared in a laboratory were subjected to multiple stress creep and recovery test and oscillation measured at 60 °C in a dynamic shear rheometer. Results show that using dynamic shear rheometer to determine the properties of these materials is advantageous. Petrographic origin of the filler to a great extent affects the behavior and properties of the mastic mortar, especially its stiffening effect. Limestone filler stiffened the bituminous binder the least and reference materials, containing high ratio of mica, stiffened the binder the most.