Effects of Dwell Time on the Deformation and Fatigue Behaviour of A356-T7 Cast Aluminium Alloys Used in High Specific Power IC Engine Cylinder Heads

• Published in: Materials Vol. 13; no. 12; p. 2727
• Main Authors: Natesan, Elanghovan, Meyer, Knut Andreas, Eriksson, Stefan, Ahlström, Johan, Persson, Christer
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 15.06.2020; MDPI
• Subjects: Alloys; Aluminum base alloys; Automotive engines; CAE; cast aluminium; Compressive properties; Computer aided engineering; Copper; Copper base alloys; cylinder head; Cylinder heads; deformation behaviour; Deformation effects; Ductility; dwell; Dwell time; Electrification; Engine cylinders; Engine materials; Engines; fatigue; Fatigue tests; Heat conductivity; High temperature; Influence; Internal combustion engines; Load; Materials fatigue; Mechanical properties; Metal fatigue; Plastic deformation; Powertrain; Silicon; Stress relaxation; Time dependence; Weight reduction
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma13122727

The electrification of automotive powertrains in recent years has been driving the development of internal combustion engines towards reduced volumes with higher power outputs. These changes place extreme demands on engine materials. Engineers employ the computer-aided engineering approach to design reliable and cost-effective engines. However, this approach relies on accurate knowledge of the material deformation and fatigue characteristics during service-like loading. The present study seeks to investigate the effect of dwell times on the deformation and fatigue behaviour of the A356-T7 + 0.5 wt.% Cu alloy used to cast cylinder heads. In particular, we study the effect of dwell time duration at various temperatures. A combined fatigue-dwell testing procedure, with the dwell at the maximum compressive strain, replicates the service conditions. It is found that the material exhibits a stress relaxation behaviour with a decreasing relaxation rate. At lower temperatures, the load level influences the relaxation more than at elevated temperatures. However, the dwell does not significantly affect the hardening behaviour or the life of the tested alloy. Finally, we model the time-dependent material behaviour numerically. The Chaboche model, combined with a Cowper–Symonds power-law, is found to capture the visco-plastic deformation behaviour accurately.