Tensity and endurance of a structure with discrete weld bonding under stationary random vibrations

Machine-building Engineering and Machine Science

Welding, allied processes and technologies


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

Discrete weld bonding are zones of increased stress concentration, formed due to heating non-uniformity during welding process and significant difference in mechanical characteristics of a metal in weld junctions from those of a parent material. Under repeated loading action the occurrence of fatigue fractures evolved between weld materials at the contour of a weld point is most probable. The fatigue endurance of the structures with weld bonding is determined, for the most part, by the stressed state dynamic characteristics at local zones of weld points. To obtain the proper durability estimation of such kind of structures one should define stressed state dynamic characteristics with allowance for its essential spatial non-uniformity and local changes in material properties.

The paper presents the technique and results of a structure with spot-welded joints subjected to random vibration probabilistic characteristics computation using finite elements simulation. Simulation of the dynamic stress state was executed for the structure under random kinematic loading conditions with the specified power spectral density function of acceleration. To substantiate the correctness of the simulation of spot-welded joints the authors studied by computation the samples of spot-welded joints, tested for static strength under tensile and shearing, and plotted vibrating stress spectral characteristics for various points of the structure. Zones and levels of maximum stresses were determined. Features of dynamic stress state in welded joints were revealed. Estimations of specific damageability and mean longevity of welded joints under various theories of accumulation of fatigue damages were obtained.

The attribute of the study consists in detailed modelling of dynamic stress state at welded joint considering significant changes of the properties of the parent material over spot weld cross section. The properties of the material at spot weld local zones are determined based on micro-hardness yield stress empirical dependences.

The developed technique and numerical simulation results can be applied to assess the vibration strength of thin-walled structures with discrete welded connections.

Keywords:

discrete weld bonding, spot welding, random vibration, finite element simulation, dynamic tension, spectral density, fatigue strength, fatigue endurance

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