Online Steel Fatigue Resource Generates Interest

The Bar Fatigue Blog is hosted by the Long Product Market Development Group (LPMDG), part of the Steel Market Development Institute (SMDI; Detriot, MI), is an online resource/tool for automotive engineers looking for the latest steel fatigue innovations and information. Topics of discussion include the comparison of the fatigue properties of high carbon steels for various processing cycles and the fatigue properties of medium carbon steels in the normalized and quenched and tempered conditions.

The blog is open to participation by steel and ground vehicle OEM and supplier design engineers, powertrain / chassis engineers, materials engineers, application engineers, academia and FEA simulation experts. A synopsis of the most recent posts includes:

Carburized Core Properties When Hardness is Controlled by Cooling Rate, the core hardness of carburized parts is a function of the steel hardenability, the cooling rate of the quenchant used and the cross section size of the part. With a given steel and quenchant, the hardness is controlled by the cooling rate.

Strength and Fatigue Life vs. Carbon Content at High Hardness (60 HRC), which shows strength and fatigue life of both plain carbon and low alloy steel grades with carbon contents ranging from 0.50 percent to 0.95 percent. The heat treatments used to obtain this hardness level were quench and tempering, carburizing and induction hardening. The yield strength and ultimate tensile strength decrease as the steel carbon content increases. As the carbon content increases to 0.95 percent, the ultimate strength decreases to about 1,000 MPa to 1,500 MPa.

Effect of Intergranular Oxidation (IGO) on Axial Fatigue Test Bar Performance, in this test, two 100 lb heats of vacuum melted 8695 steel were made for test iterations 40 and 41. The two heats were forged into bar stock from which axial fatigue test samples were machined. The static strength of iteration 40 without IGO is about 50 percent greater than iteration 41 with IGO. The elongation or ductility is also greater. If IGO had a negative effect on performance, it would occur under high cycle conditions. Therefore, it is concluded that IGO is not detrimental to the fatigue life of these samples.

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