Main features of the procedure of influence imperfection shape of the thin-walled structures’ shell on the bearing capacity

MAIN FEATURES OF THE PROCEDURE OF INFLUENCE IMPERFECTION SHAPE OF THE THIN-WALLED STRUCTURES’ SHELL ON THE BEARING CAPACITY

The article describes the method of analysis of the impact of imperfections form of thin-walled structures is based on a comparative analysis of structural strength with disabilities and without deviation from the theoretical contour of the thin-walled shell of stresses acting in all phases of operation. The possibilities of NX software complex in finite element modeling of shape imperfections are considerated.

Keywords: thin-walled design, finite element, modeling, shape, bearing capacity, strength.

As you know, under the control of the geometric parameters of thin-walled structures, technical documentation may be allowed a smooth deflection of thin- walled shells in the form of roundness, waviness, which has a negligible effect on the bearing capacity. For example, for cylindrical shells with honeycomb reinforcements it is allowed deviation of less than half the original thickness of the sheet. However, in the production of thin-walled structures it may be deviate considerably exceeding the permissible value.

In the case of the production of high-priced designs, it must be evaluation of the impact of deviations shell to further study the possibility of tolerance design for use under the terms of the strength.

This article analyzes the impact of imperfections form in excess of the tolerance envelope of thin-walled construction on the carrying capacity in the software package NX.

NX System is one of the leading centers in the field of design automation, which includes one of the key applications in conducting engineering analysis - NX Advanced Simulation. Application NX Advanced Simulation allows us to solve a wide range of problems in assessing the strength of structures.

To assess the effect of deviations smooth shells strength calculation performed on models and designs with variations without departing from the loads acting on all phases of operation.

Mechanical properties of materials, for maximum reliability, must be specified in accordance with the protocols of the test results of samples-witnesses of material goods. The heat affected zones of welds mechanical characteristics of the material are assumed to be the main characteristics of the material with attenuation depending on the type of welding.

The reserve strength of the structure elements of the thickness is specified for minimum thickness measurement results.

According to measurement results, the surface is built with deviations from the theoretical contour Key points. With an ideal finite element model of a thin- walled design, the NX System allows to create a finite element model with disabilities by projecting knots on a curved surface that it significantly reduces the time to prepare for the calculations.

Strength analysis is carried out in NX Advanced Simulation application module extended nonlinear SOL 601,106, taking into account the physical and geometric nonlinearity. This module, in a single solution, is defined in the load vs. time segments for sequentially accounting residual internal stress and strain.

After completion of the calculation, analysis and adequate interpretation of the results obtained, the application postprocessor NX Advanced Simulation has a wide range of possibilities for displaying results in graphical, with a wide range of visualization, as well as in tabular form. It is also possible to analyze the behavior of the structure in the form of an animated presentation.

Comparative analysis of the calculation’s results of deformations, displacements and stresses the design, which executed with smooth deviations and without deviation from the theoretical contour, is assessed the impact of imperfections on structural strength.

Thus, a sufficient safety margin to the design of thin-walled shell deviations from the theoretical path and the slight difference on the displacements and deformations, it can be concluded about the possibility of admission for expensive design strength conditions for further use for its intended purpose. УДК 004.032

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