MODELLING OF MATERIAL FLOW STRESS IN CHIP FORMATION PROCESS FROM ORTHOGONAL MILLING AND SPLIT HOPKINSON BAR TESTS

ABSTRACT

Estimation of flow stress of the work material is central to both analytical and numerical modelling of the machining process. Results from split Hopkinson's pressure bar (SHPB) testing were used as a starting point for the estimation of flow stress. Subsequently material flow stress valid in the context of chip formation was computed from analytical model based on results from orthogonal milling tests. The milling operation involving cyclic variation of thickness of cut was carried out for a range of cutting speeds, generating information about flow stress over a wide range of strain, strain rate, and temperatures. Two work materials differing in phase content, namely pure ferritic (REMKO) and pure austenitic (AISI 316L) were the reference materials evaluated in this study.

Keywords:

• Machining
• Modelling
• Flow Stress
• Steel

Notes

¹Parameters obtained with continuous chip model for strain and strain rate.

²Parameters obtained with chip serration model for strain and strain rate.

¹Parameters obtained from orthogonal milling tests with continuous chip model for strain and strain rate.

²Parameters obtained from orthogonal milling tests with serrated chip model for strain and strain rate.

³Parameters obtained from Hopkinson's test on “hat” shaped specimen at room temperature.

⁴M'Saoubi ([9]): parameters obtained from Hopkinson's test on cylindrical specimen at T° up to 300°C.

⁵Changeux ([10]): parameters obtained from Hopkinson's test on “hat” shape specimen at T° up to 300°C.

⁶Tounsi et al. ([3]) parameters obtained from machining tests (turning AISI316 at 250HB).

τ_exp – flow stress based on experimentally measured cutting forces.

τ_num – (1) to (6) – correspond to calculated flow stress values obtained using the 6 variants of material constants from the present study and literature information shown in Table 4.