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It has long been recognised that particle spin may have a significant effect on the impact erosion rate, particularly of ductile metals. However, no work has previously been carried out to quantify this effect, partly due to the practical difficulty of measuring the magnitude of the rotational speed. Particle spin is a feature of the centrifugal accelerator erosion tester. In this tester it has proved possible to examine the effect on erosion of particle spin direction by varying the target orientation. The results indicated a strong effect of the spin direction on erosion rate at low impact angles when the targets were impacted by angular particles. A quantitative model was developed to explain the effect of particle spin direction on the observed differences. The model is a modification of the Finnie–Bitter model [Wear 3 (1960) 87; Wear 6 (1963) 5; Wear 6 (1963) 160], and is the first to explicitly incorporate the effect of rotating particles on the subsequent erosion rate when the particles impact a metal target. The model supposes that the effective impact velocity, the contact velocity between the particle and the target, is altered due to spin of the particles. The predictions of the model were validated through actual measurement of particle rotational speed by high-speed photographic techniques; the first such measurements. Experimental erosion results conformed to the predictions of the model. An effect of particle spin on the peak erosion rate is also predicted by the model and confirmed by the experimental results. |
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