Research of a local stress state and estimation of durability of an aviation article’s structure with discrete welded connections at random loading

Aviation technics and technology


Аuthors

Rybaulin A. G.*, Sidorenko A. S.**

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: artcomj@gmail.com
**e-mail: k906@mai.ru

Abstract

In load-carrying structures of flight vehicles the connection of details with the help of spot welding is used. Feature of spot welding is the raised stress concentration which can cause decrease in characteristics of the connection fatigue strength. Fatigue cracks arise between welded elements on a contour of a welded point. For an estimation of aviation structure durability the definition of local stress state characteristics in zones of welded points at action of dynamic loadings is necessary.

In the product techniques of numerical simulation and calculated data evaluating of the stress state characteristics of a of flight vehicles structures with dot welded connections at random vibration are presented. Action of random stationary kinematic loading under operating conditions aviation product on an external suspension bracket of the maneuverable carrier is considered.

The load-carrying structures of the product represent the thin-walled cylindrical shell containing filling material simulating weight of a product. On a shell by means of spot welding the X-shaped wing symmetrically relative to a vertical plane is fixed.

For simulation the dynamic deformation of a structure with discrete welded joints the system of solid-state simulation and finite element calculation for complex structure Solid Works is used. Numerical models are developed with the use of solid-state finite elements and allow to estimate the characteristics of the local deformation structures in zones of irregularities. The spot weld model based on experimental data and taking into account the change of mechanical characteristics of the source material in a zone of thermal influence is offered. Improvement of material properties is spent on hardness size in section of welded points.

Welded points are modeled by allocating the related circular areas on the plane and on the shell and specify the conditions of a mutual motion’s absence between them. Each spot weld contains up to 420 finite elements SOLID of the second-order.

The stress state characteristics are determined for a case of loading structure stationary random acceleration with a specified spectral density.

Spectral characteristics and levels of stresses vibration in various points of the product structure are obtained. Zones of the maximum stresses in a structure are defined and dynamic stress state peculiarities in welded connections are revealed. For an estimation of welded connection durability on the basis of the received spectral density and algorithms of statistical modeling time relationships of random process of stress are constructed.

Keywords:

aircraft, design, wing box, welded connection, spot welding, finite element method, shell, vibration acceleration, vibration stress, spectral density, durability

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