TECHNOLOGICAL SUPPORT OF CONTACT RIGIDITY OF MACHINE PARTS

Examples of solving problems according to the method described in the first part of this work in the processing of contacting surfaces by turning, milling and grinding, as well as the comparison of calculated and experimental values of the contact convergence of surfaces, and the algorithm for calculating the determination of machining modes in order to ensure a given contact stiffness are given. The article describes the practical application of the research results in relation to the assembly unit of an aircraft gas turbine engine.

TECHNOLOGICAL SUPPORT OF CONTACT RIGIDITY OF MACHINE PARTS

The theoretical provisions on establishing the relationship between the geometric characteristics of the surfaces of contacting parts, as well as the physical and mechanical characteristics of the material of these surfaces on their contact stiffness, including the contact stiffness of the surfaces of parts of high-load gas turbine engine components, are presented. The analysis of dependencies on the relationship of contact stiffness and pliability of surfaces with the technological conditions of their processing by various types of cutting process (turning, milling, grinding) is given.

Single-stage technological support and machinery contact rigidity increase

The oretical and empirical dependences of contact rigidity in a fixed joint at the first and repeated loadings upon engineering methods of a joint surface treatment are presented. There are shown data on potentialities of engineering methods of treatment in support and increase of contact rigidity.

Givental’s Non-linear Maslov Index on Lens Spaces

Givental’s non-linear Maslov index, constructed in 1990, is a quasimorphism on the universal cover of the identity component of the contactomorphism group of real projective space. This invariant was used by several authors to prove contact rigidity phenomena such as orderability, unboundedness of the discriminant and oscillation metrics, and a contact geometric version of the Arnold conjecture. In this article, we give an analogue for lens spaces of Givental’s construction and its applications.

Contact modelling of highly heterogeneous friction material for braking applications

Friction brakes are increasingly undergoing considerable development to improve their durability, efficiency, maintenance costs and environmental impact. Nevertheless, to achieve this, it is necessary to understand the different mechanisms involved in contact that are multi-scale and multi-physical in nature. On the multi-scale aspect, it is well known experimentally that heterogeneities have a pre-weighted role on performance without being able to explain it. Thus, modelling seems to be a good way to better understand the influence of these heterogeneities, provided that we have a multi-scale method to consider them. The objective of this article is therefore to propose a methodology for simulating contact in the presence of heterogeneous materials. The strategy consists in enriching the contact rigidity in terms of behaviour by a method of numerical homogenization. The significant advance of this article lies in the consideration of contact within the technique of numerical homogenization of a heterogeneous material. The strategy is then validated by comparing the mechanical fields between the proposed method and an explicitly meshed case. One of the main contributions of this work is the reduction in computing time compared to the traditional FEM method.

TORSIONAL WAVE SCATTERING IN TWO-LAYER PIPE WITH ACCOUNT FOR CONTACT RIGIDITY

The purpose of the paper is to study the wave propagation in a two-layer pipe, taking into account the rigidity of the contact between its layers. It is considered by solving the equation of motion for the vector and scalar potentials. A dispersion equation describing the frequency distribution of the phase velocities of waves in the waveguide under investigation is derived. In order to take into account the degree of contact rigidity between layers additional terms are added to the boundary conditions, including the normal (kGN) and tangential (kGT) contact rigidity coefficients. It is shown that torsional waves are separated from other types of waves and can be considered separately. The example of a numerical solution of the dispersion equation shows the possible behavior of dispersion curves without regard to the contact rigidity. The similar problem solution is provided with allowance for contact rigidity at various perforation coefficients. A conclusion is drawn on the effect of contact between layers on torsional wave behavior. The similar method solves the problem for a homogeneous pipe with internal stratification. Recommendations are given for taking into account the revealed regularities in the development of ultrasonic methods of control based on torsional wave propagation.

Automated quality support of surface and contact rigidity in machinery

One of the ways to ensure and increase machining quality is an adaptive mode control of a technological operation. It is necessary to have a simulator for adaptive control system functioning. There are such simulators not for all materials under machining and working conditions. Under production conditions such a problem can be solved at the expense of self-correcting technological system use. The integration of a self-correcting system into an automated system of scientific investigations will allow ensuring required operation properties with a specified accuracy.

Theoretical analysis of mating surfaces contact rigidity with technological conditions of their machining

An author’s version for the design definition of an approach value of contact surfaces under load taking into account roughness of a surface worked and a surface layer cold work of these surfaces is presented. The analysis of a processing mode impact upon the value of surfaces contact approach is carried out, and also the comparison of the computation results of a flexibility parameter with experimental data is performed.

NEUROCOMPUTER MODELING OF CONTACT RIGIDITY

Contact rigidity of a joint is one of the main criteria of operability of forest cars. It defines vibration activity and durability of the tightened bolted connections therefore its assessment will allow to predict behavior of technical systems. In work the technique of an assessment of contact rigidity by means of the nerocomputer modeling allowing to consider parameters of quality of a blanket is presented. Results of re-searches allowed to receive mathematical models for contact rigidity. In the paper there is presented a procedure of contact rigidity estimate with the aid of neurocomputer modeling. A contact rigidity of a joint is one of the basic criteria of machine and mechanism capacity for work. It defines vibration activity and strength of tightened bolted connections therefore its estimate will allow forecasting the behavior of technical systems. Neurocomputer modeling is a promising method allowing taking into account quality parameters of a surface layer of machinery at the analysis of a deformed state.