Determination of Stress Intensity Factor in a Beam with a Central Crack and Estimation of the Critical Crack Length

Purpose of research.  Propose an analytical method for determining the stress intensity factor for the second form of fracture in a beam with a crack. It will be possible to take into account the influence of cracks and crack-like damage found in beams during surveys using the solution obtained, in the presence of an experimental base of values of the critical stress intensity factors.

Methods. It is proposed a method for calculating the stress intensity factor for the second form of fracture (transverse shear) in the beams using the analytical method known in the resistance of materials and structural mechanics of the section method. To do this, equilibrium conditions are created for mentally cut parts of a bent element using the hypotheses of the distribution of normal and tangential stresses along transverse and longitudinal sections. This method of calculation can be applied in assessing the carrying capacity of wooden beams that have operational damage, such as laminations of adhesive joints and trimmed and force cracks.

Results. Using the proposed technique, we have estimated the critical size of a through-going that does not reach the end of a wooden beam under short-term loading. The experimental data obtained by the author are taken as the initial data for the calculation.

Conclusion. For the practical application of this technique, on the basis of experimental data, the values of the calibration coefficients should be selected that match the theoretical solution with the experimental data best of all. In addition, in a further experimental study, it is necessary to obtain and refine the dependencies of the critical stress intensity factor on operational factors: loading duration, wood moisture, cross-sectional dimensions, crack position, crack depth ratio and total cross-sectional width of elements.

wooden beam, method of sections, stress intensity factor, critical crack length

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