Compressive Properties of High Velocity Pressed Iron Powder at High Strain Rates

In the field of powder metallurgy, high velocity compaction (HVC) is a production technique with capacity to improve the mechanical properties of powder metallurgy parts because high density of powder metallurgy parts can be achieved in less than 0.5 s [1, 2]. In order to extend the usage of the HVC method, detailed knowledge of the HVC process is important. To facilitate development of production processes, numerical simulations can be utilized. A common numerical method for powder compaction is the finite element method (FEM). To conduct on FEM simulation precisely, constitutive data of HVC specimens at high strain-rate are required [3, 4]. In this study, the dynamic compressive properties of cylindrical specimens made by HVC were measured using a Spit Hopkinson Pressure Bar (Kolsky bar). The powder material used for the experiments was a press-ready premix containing Distaloy AE, 0.5% graphite (uf-4) and 0.6% Kenolube. During dynamic compression, the failure behavior of specimens was also observed using a high speed video camera. The experimental results, such as failure stress, Young’s modulus and failure behavior, of dynamic compressive tests were compared with those of static compressive tests. Among specimens made by HVC and Conventional Compaction (CC), the effects of specimen density, 6.9, 7.2 and 7.4 g/cm3, on the compressive properties and failure behavior were also examined. For each density, the difference in the failure behavior between HVC-pressed specimens and conventional pressed specimens was observed, whereas stress-strain curves of HVC-pressed specimens were the same as conventional pressed specimens. Moreover, the effects of specimen size on failure behavior and stress-strain curves of specimens were examined.Godkänd; 2013; 20131003 (gusgus