Simulation of multicentric destruction with regard for inhomogeneous distribution of rated voltage

The algorithm simulating the initiation and development of fatigue cracks in the joint weld on the example of the mount of the mobile platform and the supporting cowl of Gottwald NMK 170 EG (63 tons) crane rotator, the destruction of which occurred in 2011 in the territory of “Novorossiysk commercial sea port” OJSC (NCSP), is worked out. The proposed algorithm takes into account the non-uniform weld geometry affecting the value of the stress concentration factor and the uneven distribution of the rated stress related to the joint design features. The modeling process is based on the experimentally established fact that the geometry profile of the junction between the weld and the base metal along the welded joint changes randomly. As a result, the fatigue flaking along the weld lacks any regular pattern. Under the cyclic loading, the development of the destruction is a sequential process of the crack nucleation in different parts of welded joints along the weld, single surface cracks growth under the fracture mechanics laws, nucleation of new cracks, and crack coalescence in the adjoining sections. At the coalescence of the crack edges, the contour profile is changing which leads to increasing the growth rate of the crack depth. In the future, the development of the multicentric destruction continues until the critical crack. The damage accumulation and destruction development rate depends on the uniformity coefficient of the stress concentration along the weld. The implementation of the proposed model allows solving the problems of determining the frequency of node diagnosis and the points with the utmost probability of fatigue cracks initiation, as well as validating the possible methods of structural reinforcement.

многоочаговое разрушение, концентрация напряжений, распределение НДС, неравномерное распределение номинальных напряжений, multifocal destruction, stress concentration, distribution of stress strain behavior, uneven distribution of rated stress

1. Lukjanov, V.F., Korobtsov, A.S, Naprasnikov, V.V. Statisticheskoe modelirovanie razrusheniya svarnykh soedineniy. [Statistical modeling of fracture of welded joints.] Automatic Welding, 1989, no. 1, pp. 43–48 (in Russian).

2. Lukjanov, V. F., Korobtsov, A.S. Imitative simulation of welded joint fracture under low-cycle loading. International Journal of Pressure Vessels and Piping, 1991, vol. 47, iss. 2, pp. 193-206.

3. Kurkin, S.A., Khovov, V.M., eds., et al. Komp'yuternoe proektirovanie i podgotovka proizvodstva svarnykh konstruktsiy. [Computer-aided design and preproduction of welded structures.] Moscow: Izd-vo MVTU im. N.E. Baumana, 2002, 464 p. (in Russian).

4. Sosudy i apparaty stal'nye. Normy i metody rascheta na prochnost' pri malotsiklovykh nagruzkakh. GOST 25859-83. [State standard 25859-83. Steel vessels and apparatuses. Norms and methods of fatigue strength calculation under lowcyclic loads.] Moscow: Izdatel'stvo standartov, 1983, 36 p. (in Russian).

5. Parkhomenko, А.А. Metody i kriterii otsenki lokal'nogo napryazhenno-derformirovannogo sostoyaniya svarnykh soedineniy : diss. magistra tekhniki i tekhnologii. [Methods and criteria for evaluating the local stress-strain state of welded joints: Master of Engineering and Technology diss.] Rostov-on-Don, 2006, 111 p. (in Russian).

6. Basquin, О. H. The exponential law of endurance tests. Proceedings, American Society for Testing and Materials, 1910, vol. 10, pp. 625–630.

7. Manson, S.S. Fatigue: a complex subject-some simple approximation. Experimental Mechanics, 1965, vol. 5, iss. 4, pp. 193–226.

8. Coffin, L.F., Jr. A study of the effect of cyclic thermal stresses on a ductile metal. Transactions of the ASME, 1954, vol. 76, pp. 931–950.

9. Assaulenko, S.S., Lukyanov, V.F. Analiz prichin razrusheniya metallicheskikh konstruktsiy opornogo uzla strelovogo krana. [Failure analysis of boom seat metal structures.] Vestnik of DSTU, 2014, no. 4(79), pp. 186–194 (in Russian).

10. Assaulenko, S.S. Optimizatsiya razmeshcheniya reber zhestkosti pri remonte ramy povorotnoy platformy gruzopod''emnogo krana. [Optimize the placement of stiffening ribs for repair of a lifting crane platform.] Vektor nauki TGU, 2014, no. 1 (27), pp. 33–35 (in Russian).

11. Iluin, A.V., et al. Metody rascheta tsiklicheskoy prochnosti svarnykh soedineniy. [Analysis techniques for fatigue strength of welded joints.] Leningrad: LDNTP, 1983, 33 p. (in Russian).

12. Paris, P.C., Erdogan, F.A. A critical analysis of crack propagation laws. Transactions of the ASME. Journal of Basic Engineering, 1963, no. 4, pp. 528–534.