EXPERT ASSESSMENT OF RESIDUAL STRENGTH OF VEHICLE LONGERON, WHICH WAS DAMAGED BY A CRACK

Beams and plates are important load-bearing elements of most designs of mechanisms and machines that work on bending or torsion. Safe operation of load-bearing beams of spars of cars working in the conditions of repeated alternating loadings and having a large number of concentrators of tension is very important. Stresses cause cracks in the beams, which can cause dangerous accidents. The calculation of these elements is extremely complex and requires the consideration a large number of factors. The problem of studying the bending of beams and plates, which are weakened by cuts or cracks, is covered in many scientific sources. The purpose of the study is to develope a method of expert assessment of the residual strength of the longeron of vehicle. The article develops a method of expert assessment of the residual strength in the load-bearing beam of the car spar, which is damaged by a crack in the stretched fibers of its lower surface under static load. The wall thicknesses of the spar are quite thin, so it is believed that the crack has gone through and can then spread to the vertical walls until the complete destruction of the entire beam. The calculation was performed on the basis of the equations of the nonclassical model of bending of short beams, which took into account the influence of deformations of transverse shear and compression. The residual strength of the beam was determined from the conditions determined by the force criterion of J. Irwin. It was believed that the load on the spar beam is distributed according to the law of sinusoids and concentrated moments at the edges. The obtained numerical data are summarized in comparative tables. The residual strength found according to the force criterion of crack propagation and according to the method of allowable stresses is compared.