The Deformable and Strength Characteristics of Nanocomposites Improving

Mechanical properties of composites and nanocomposites have been considered in the assumptions of linear elasticity. To describe the nanoscale contact between matrices and inclusions on the interface surface, the conditions of ideal contact and non-classical Gurtin-Murdoch conditions have been implemented. The influence of shapes and relative sizes of inhomogeneities and matrices of representative volumes on the effective elasticity modulus of nanocomposites has been treated. Matrices in the form of cube and cylinder of finite sizes and inhomogeneity in the form of spheres and fibers have been considered. Finite element-based calculation models have been generalized to composites with distributed nanoinclusions of random and ordered orientation. The resulting models create the informative base for nanocomposites synthesis technologies with improved deformable and strength characteristics.

Effect of surface tension on the antiplane deformation of bimaterial with a thin interface microinclusion

Within the framework of the concept of micromechanics, a method for taking into account the effect of surface energy for a thin interface micro-inclusion in the bimaterial under conditions of longitudinal shear has been proposed. The possibility of non-ideal contact between inclusion and matrix is provided, in particular, tension contact. This significantly extends the scope of applicability of the results. A generalized model of a thin inclusion with arbitrary elastic mechanical properties was built. Based on the application of the theory of functions of a complex variable and the jump function method, the stress field in the vicinity of the inclusion during its interaction with the screw dislocation was calculated. Several effects have been identified that can be used to optimize the energy parameters of the problem.

THE METHOD OF SELECTION THE SOLID FINITE ELEMENT MODELS OF LOAD-BEARING SYSTEMS OF MACHINE TOOLS WHEN PERFORMING ENGINEERING ANALYSIS

The paper presents a methodology for the selection of a solid finite element models for load-bearing systems of machine tools. The technique is based on the analysis of the results of computer simulation of different models of load-bearing systems of three machines with different layouts. The variability of the models is determined taking into account the traction devices and joints in the conjunctions. The traditional approach for modeling the non-ideal joint in the form of elastic elements set is used, despite the fact that modern CAE systems for modeling non-ideal contact in mates offer special contact finite elements. The conducted computational experiments demonstrate that the most accurate model is obtained by using models of traction devices and joints. In this case, the computational model requires significant computational resources. It is found that the exception of the design model of the bearing system of the machine traction devices can lead to an increased modeling error in static problems up to 25 %. The results of modal and dynamic calculations are more resistant to changes in the design model of the machine, as the error of the design parameters does not exceed 10 %. In addition, the computational models of tightened joint, with a stiffness of more than N/m, are not much different from models with ideal contact. It is shown that with an acceptable 25% modeling error, it is preferable to use a computational model of the load-bearing system without taking into account the non-ideal contact and traction devices

THE METHOD OF SELECTION THE SOLID FINITE ELEMENT MODELS OF LOAD-BEARING SYSTEMS OF MACHINE TOOLS WHEN PERFORMING ENGINEERING ANALYSIS

The paper presents a methodology for the selection of a solid finite element models for load-bearing systems of machine tools. The technique is based on the analysis of the results of computer simulation of different models of load-bearing systems of three machines with different layouts. The variability of the models is determined taking into account the traction devices and joints in the conjunctions. The traditional approach for modeling the non-ideal joint in the form of elastic elements set is used, despite the fact that modern CAE systems for modeling non-ideal contact in mates offer special contact finite elements. The conducted computational experiments demonstrate that the most accurate model is obtained by using models of traction devices and joints. In this case, the computational model requires significant computational resources. It is found that the exception of the design model of the bearing system of the machine traction devices can lead to an increased modeling error in static problems up to 25 %. The results of modal and dynamic calculations are more resistant to changes in the design model of the machine, as the error of the design parameters does not exceed 10 %. In addition, the computational models of tightened joint, with a stiffness of more than N/m, are not much different from models with ideal contact. It is shown that with an acceptable 25% modeling error, it is preferable to use a computational model of the load-bearing system without taking into account the non-ideal contact and traction devices

Method of finite bodies for determination of the plane stressed state of rectangular plates with a rectangular hole

The paper is devoted to the determination of the stress-deformed state of structurally heterogeneous bearing rectangular plates with a rectangular hole. The new analytical-numerical method (finite bodies) was used, to find the stress state of the plate with a hole. The method of finite bodies uses the conditional partition of the doubly-connected surface of the plate into simpler connected rectangular parts. On the lines of conditional contact, the conditions of ideal contact are taken into account, which ensure the equality of stresses, deformations and displacements. The perturbed stressed state, which is presented in the form of a series of functions, which is rapidly intercepted at a distance from the outline of the hole, is considered. A finite sum of solutions of a plane problem is used and the stress state of a perturbed state is given as a sum of a series for nonorthogonal functions. The components of vector of displacements and stresses are written. The determination of the coefficients of the sum of a series is based on the proposed method of satisfying all boundary conditions and the conditions of ideal contact to find the minimum of a generalized quadratic form. The numerical criterion for the convergence of the method is theoretically established. It is shown that the accuracy of satisfaction of boundary conditions and conditions of ideal contact is estimated by one number – the minimum of a generalized quadratic form.

Numerical Analysis of Bolt Elastic Interaction in Non-Gasketed Flange

The joint of low pressure shaft in turbofan engine is a typical non-gasketed flange connection structure, which requires the uniform preload distribution due to high performance. But in the process of tightening, because of bolt elastic interaction, the final preload distribution could be varied. The face runout of contact surface changed the properties of the elastic interaction, which proposed new requirements of non-gasketed flange research. Thus the two bolts flange FEA model was developed to focus on the effect of bolt space, tightening step and face runout on preload change rate with actual contact. The six bolts flange FEA model was developed to make a comparison between ideal contact and actual contact. The bolt elastic interaction of actual contact was proposed, which provide the final preload distribution of different tightening patterns. And then the effect of tightening start position on final preload distribution was discussed, which could provide theoretical basis for non-gasketed joint assembly.

Combined method of opencast and underground mining of valuable ore

The efficiency of the combined opencast and underground mining of deposits directly depends on the overburden amount within the open pit boundaries. The amount of overburden to be removed, in its turn, is determined by the angles of the open pit slopes. At the same time, the influence of the open pit slope angle on the amount of the rock mass within the open-pit contours increases in an arithmetic progression with the mining depth. This fact confirms the direct relationship between the open pit slope angle and the efficiency of the mining operations from both an economic and ecological points of view. The article considers the technology for mining steeply inclined deposits of valuable ores by means of underground chambers mined out in advance with consolidating stowing to support unworked sides of an open pit called “well”. The chambers which can be not only vertical but also inclined at an angle of 60-80° serve to create an artificial fence (a ring concrete support). The work of the fence supporting the open pit side is markedly different from that of retaining walls of any type since the consolidating stowing mixture used to create the fence provides an ideal contact of the concrete wall with the enclosing rocks, thus making it impossible for an artificial fence to overturn. The proposed combined mining technology is expected to reduce considerably the number of the overburden operations, to minimize the damage caused by mining operations to the environment, and to increase the intensity of mine workings.