The DT16AT sheet billet cutting method effect on the conditional endurance limit

DOI: 10.34759/vst-2022-2-189-196

Аuthors

Matveeva K. F.^*, Gorshkov Y. S.^**, Pavlov V. F.^***

Samara National Research University named after Academician S.P. Korolev, 34, Moskovskoye shosse, Samara, 443086, Russia

*e-mail: matveeva_kf@mail.ru
**e-mail: usgorshkov@yandex.ru
***e-mail: sopromat@ssau.ru

Abstract

Machining by milling and laser cutting are widely applied in blanking-and-stamping production. However, despite the availability and simplicity of the milling method, laser cutting is being increasingly employed in production.

The laser cutting method ensures high productivity of the process in combination with high precision and quality of cut surfaces, as well as a small cutting width. However, one of the significant disadvantages of laser cutting consists in the presence of a temperature-affected zone in the area of laser beam impact, which leads to a change in the material properties at the edge of the billet and, as a result, to a decrease in the fatigue resistance of parts.

Fatigue test samples were cut from a 2.5 mm thick cold-rolled sheet of the D16AT alloy across the rolling direction. One part of the samples was fabricated by milling, while the other part was produced by laser cutting. The samples were tested for high-cycle fatigue in bending at a symmetrical cycle, and the test base was of three million loading cycles. The loading threshold of the three samples without their destruction was being estimated. Besides, after laser cutting the samples, were subjected to etching in Keller’s reagent to eliminate the defective layer formed as the result of laser processing.

The result of the samples fatigue testing revealed that the conditional endurance limit of the samples obtained by the laser cutting method was 55MPam which was 60% lower than the one for the samples manufactured by milling, which was equal to 90 MPa.

The metallographic results allowed revealing that the end-butts of the samples manufactured by the laser cutting method contained the defective layer associated with the metal overburning, which was the cause of the conditional endurance limit reduction. To remove the metal layer with overburning etching was employed, which allowed partial restoring of the conditional endurance limit of the material equal to 80 MPa. In this case, the conditional endurance limit is 18% less than that for the milled samples.

Thus, the conducted study reveals that during the products operation obtained by laser cutting, premature fatigue failure may occur under cyclic loading conditions. To eliminate this possible defect, formed as the result of manufacturing by the laser method, the defective metal layer with overburining should be removed. The defective layer removal will lead to the increase fatigue resistance of the products.

Keywords:

sheet billet from alloy D16AT, laser cutting, material overburning, defective layer removal

References

1. Bratukhin A.G., Abramov B.M., Arutyunov S.G. et al. Aviastroenie: Letatel’nye apparaty, dvigateli, sistemy, tekhnologii (Aircraft industry. Aircraft, engines, systems, technologies), Moscow, Mashinostroenie, 2000, 536 p.
2. Wetzig A., Herwig P., Hauptmann J. et al. Fast Laser Cutting of Thin Metal. Procedia Manufacturing, 2019, vol. 29, pp. 369-374. DOI: 10.1016/j.promfg.2019.02.150
3. RussellGidroabrazivnaya rezka (Water Jet Cutter), Moscow, VSD, 2013, 240 p.
4. Skuratov D.L., Shvetsov A.N. Opredelenie ratsional’nykh uslovii formoobrazovaniya i uprochneniya poverkhnostei detalei na operatsiyakh mekhanicheskoi obrabotki (Determining rational conditions for parts surface shaping and hardening during machining operations), Samara, Samarskii universitet, 2018, 112 p.
5. Monakhov G.A., Zhdanovich V.F., Radinskii E.M. et al. Obrabotka metallov rezaniem. Spravochnik tekhnologa (Metal cutting. Technologist’s guide), Moscow, Mashinostroenie, 1974, 598 p.
6. Grigor’yants A.G. Osnovy lazernoi obrabotki materialov (Fundamentals of materials laser processing), Moscow, Mashinostroenie, 1989, 304 p.
7. Debay A.K., Vadava V. Optimization of kerf quality during pulsed laser cutting of aluminium alloy sheet. Journal of Materials Processing Technology, 2008, vol. 204, no. 1-3, pp. 412-418. DOI: 10.1016/j.jmatprotec.2007.11.048
8. Zeuner A.T., Kühne R., Standke C. et al. Fatigue Behavior of Laser-Cut Sheet Metal Parts with Brazed-On Elements. Metals, 2021, vol. 11, no. 12. DOI: 10.3390/met11122063
9. Grechnikov F.V., Gorshkov Yu.S., Mishin A.M. Izvestiya Samarskogo nauchnogo tsentra RAN, 2015, vol. 17, no. 6-3, pp. 632-635.
10. Filatov E.Ya., Pavlovskii V.E. Universal’nyi kompleks mashin dlya ispytaniya materialov i konstruktsii na ustalost’ (Universal complex of machines for materials and structures fatigue testing), Kiev, Naukova Dumka,1985, 92 p.
11. Kiselev F. D. Fracture diagnostics and operational workability evaluation of working turbine blades of aircraft engine. Aerospace MAI Journal, 2019, vol. 26, no. 4, pp. 108-122. DOI: 10.34759/vst-2019-4-108-122
12. Orishich A., Shulyatyev V., Golyshev A., Malikov A. Thermophysical problems of laser cutting of metals. MATEC Web of Conferences, 2017, vol. 115. DOI: 10.1051/matecconf/201711508004
13. Sýkorová L., Šuba O., Pata V., Kubišová M. Structural Changes in Metals during Laser Cutting. Materials Science Forum, 2018, vol. 919, pp. 25-33. DOI: 10.4028/www.scientific.net/MSF.919.25
14. Rodrigues G.C., Vorkov V., Duflou J.R. Optimal laser beam configurations for laser cutting of metal sheets. Procedia CIRP, 2018, vol. 74, pp. 714-718. DOI: 10.1016/j.procir.2018.08.026
15. Laakso P. Laser cutting. Ruiskuvalupäivät (15-16.11.2007; Tuusula).
16. Wetzig A., Herwig P., Hauptmann J. et al. Latest developments of laser cutting. Journal of Laser Applications, 2016, vol. 103. DOI: 10.2351/1.5119063
17. Courtier A.F., McDonnell M., Praeger M. et al. Modelling of fibre laser cutting via deep learning. Optics Express, 2021, vol. 29, no. 22, pp. 36487-36502. DOI: 10.1364/OE.432741
18. Belforte D.A., Jafferson J.M. Laser Cutting. Reference Module in Materials Science and Materials Engineering, 2016. DOI: 10.1016/B978-0-12-803581-8.01853-1
19. Naresh, Khatak P. Laser cutting technique: A literature review. Materials Today: Proceedings, DOI: 10.1016/j.matpr.2021.08.250
20. Amara E.H., Kheloufi K., Tamsaout T., Aggoune S. Modelling of laser beam distribution effects for metal laser cutting. Lasers in Engineering, 2016, vol. 35, pp. 187-196.