This paper focuses on the application of foamed bitumen technology in the production of asphalt mixtures. This technology replaces the common asphalt binder with foamed bitumen for production of asphalt mixtures. Given the foaming, it is possible to produce asphalt mixture at a lower working temperature. This “eco-friendly” technology has been increasingly used by the asphalt mixture producers in Europe because of reducing the energy demands of the asphalt mixture productions. In this paper, first the technology of the foamed bitumen production is explained and then the results of laboratory research are presented, in which selected empirical and functional parameters of two types of asphalt mixtures of the asphalt concrete type (AC) are compared. These mixtures were produced in two versions, one of them containing the common asphalt binder and the other one the foamed bitumen. While comparing the samples, attention was paid especially to the comparison of the stiffness modulus of the laboratory-produced asphalt mixtures according to EN 12697-26 and to their low-temperature characteristics according to EN 12697-46.

The numerical simulation of fatigue behavior of the Aluminum 7075-T6 cantilever beam with an angular crack has been investigated. Cracks are located separately in three different positions of the investigated beam. To predict the fatigue behavior of the cantilever beam the crack propagation was manually simulated. Compression load is applied in different stress ratios between zero and one; then, the obtained numerical results of this research are compared with the experimental results. It is observed that increasing the stress ratio increases the percentage of the fatigue life of the sample significantly. Ascending growth of fatigue life is slow and more severe by increasing of the stress ratio for the first and the third position, respectively. By increasing the stress ratio, the rate of deviation of the crack decreases and it converges to 0° in parallel to the width of the beam. This result is also observed with an increase in the distance from the support of beam. Furthermore, it is also revealed that by the increase in the initial length of the crack, the fatigue life initially reduces with smaller ratios. However, along the larger cracks, the decreasing ratio of fatigue life increases significantly.

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.