Modeling of Surface Fracture in Friction Interaction of Fiber Composites

The model of the frictional interaction of a fiber composite material with a rigid non- wearing body is proposed, which makes it possible to study the effect of the mechanical and strength characteristics of the fiber and matrix materials and the composite structure on its stress state, in particular, at the fiber-matrix interface. Analysis of the stress distribution in the subsurface layers of the composite was carried out for different values of the ratio of matrix to fiber materials hardness, the sliding friction coefficient and the distance between the fibers. For the known failure criteria of fiber composites, the conclusions about the effect of the structure and relative strength properties of a fiber (fiber bundle) and matrix on the pattern of subsurface fracture of the composite under sliding friction conditions are made

Axial Bearing Capacity Analysis of Pile Foundation using Nakazawa Method

Pile foundation serves to distribute all the loads in the building to the ground. There are several calculation methods for bearing capacity of pile foundation, one of them is Nakazawa method. Nakazawa method adapted from calculation used in Japan where it is relevant for soft soils. The aim of this research is to obtain axial bearing capacity of pile foundation that can withstand axial forces using Nakazawa method. The parameter that used for the calculation is modified or average N-value (). The analysis result shows the value is smaller than N existing, indicate that Nakazawa tend to use weaker value of N blows. It means the calculation is considered softer type of soils than the existing ones.The value of point bearing capacity, Rp, assimilate to the pattern of N-SPT. The result value of friction bearing, Rf, in respect of depth shows the linear trending. Rf along the pile depends on the friction interaction between soil and structure. This phenomena influenced by the soil type. The value of cohession along the pile augment, means the ability of soils to stick to the pile/structure is also high. It explains why the value of friction bearing is bigger in respect of depth.

INVESTIGATION OF ROTATIONAL AND LONGITUDINAL MOTIONS OF A SUPER LONG ROD IN INCLINED BORE-HOLES

The article deals with a super long elastic tubular rod with an internal fluid flow. The rotational and longitudinal motions of straight and curved rods in inclined bore-holes are studied. The bifurcation states of the rod at these motions are investigated. The purpose of the study is to detect at the beginning of bifurcation states of straight and curved rods taking into account their friction interaction with the inner surface of a bore-holes. The reasons of appearance of bifurcation protrusion of the rod are stated. Among these reasons, an internal longitudinal force and torque are identified and described as main ones. Research methods are based on the construction of boundary-value problems determining the stress­strain state and stability of super long straight and curved rods in an inclined bore-hole. Solving the problems allows detecting the beginning of bifurcation states of rods. KEY WORDS: SUPER LONG ROD, STRIGHT AND INCLINED BORE-HOLE, ROTATIONAL AND LONGITUDINAL MOTIONS, BIFURCATION STATES, LONGITUDINAL FORCE, TORQUE.

Influence of contact-friction interaction at cutting on processing quality

By mathematical modeling it is determined, that when turning in the zone of secondary plastic deformations of the cut layer at increase of the friction coefficient, the length of the chip contact with the front surface of the cutting wedge increases. In this case, significant residual stresses are formed in the surface layer. Keywords cutting, metal, cutting wedge, friction coefficient, chip, quality, stress, residual stresses [email protected]

ESTIMATION OF THE COEFFICIENT OF STATIC FRICTION BY MEANS OF NUMERICAL ANALYSIS

The friction coefficient is one of the most important tribological parameters. The value of this coefficient may be determined with the use of various methods. The friction coefficient proves to be of significance when assembling the elements of the gear pump body WPZ-80A. The bodies of these pumps consist of three elements and are manufactured in two configurations of materials. These materials are aluminium alloy AK-20 and grey iron ZL-250. Friction interaction between the elements of the pump body ensures its stable operation under load. Research so far has focused on numerical analyses for pump bodies at a set friction coefficient. This article presents a reverse analysis, i.e. an estimation of the friction coefficient value based on the WPZ-80A pump body effort. To this end, numerical analysis based on the Finite Element Method (FEM) has been used. The analysis was based on the fact that the value of friction coefficient significantly influences deformation distribution in the WPZ-80A pump body. The analysis was performed on an already constructed pump body of known geometry with no structural modifications. The value of the static friction coefficient was estimated by observing the scale of deformations in the pump body under a set load. Although the main focus was on analysing the mechanism behind the deformations, an attempt was also made at extending the application scope for FEM. Depending on the measurement method, friction coefficient values may significantly differ. Despite the differences, the values resulting from numerical analysis should not differ from the range of values obtained with other methods of analysis. The range of friction coefficient values was determined on the basis of literature studies. As a result, it was possible to verify FEM in a field different than classic effort analysis. The aim of the work presented in this article was to obtain information on tribological properties with the use of numerical analysis.

SYNERGETIC MODEL OF ELECTRO-FRICTION INTERACTION

The paper describes algorithms and structure of the electro-friction interaction synergetic model. The results of theoretical modelling and experimental study of sliding electrical contact are given. The comparison of theoretical and experimental results made in the paper proves high validity of the model and its programmatic implementation.

Mechanical Properties and Size Effects of Self-Organized Film

In our research, we have focused on the estimation of tribological and mechanical characteristics of self-organized copper film, formed through a friction of brass-steel pair in aqueous solutions of carbolic acid. We have found out that self-organized copper film formed through a friction interaction of pair brass-steel is nanostructural. The data obtained through the indentation of self-organized copper films indicated size effect. With an increasing load and contact area of interacting bodies, the coefficient of friction first drops sharply with an increasing normal load and then begins to grow. We have found out that the adhesion component of friction contributes to the friction coefficient at small loads. We have shown that the hardness of self-organized copper films formed at friction in aqueous solutions of acids increases upon shifting from acetic to caproic acid.