Wear 256 (2004) 1037–1049 The influence of particle rotation on the solid particle erosion rate of metals T. Deng 1 , M.S. Bingley ∗ , M.S.A. Bradley Medway School of Engineering, Wolfson Centre for Bulk Solids Handling Technology, University of Greenwich, Medway Campus, Chatham Maritime, Kent ME4 4TB, UK Received 30 July 2002; received in revised form 27 June 2003; accepted 27 June 2003 Abstract 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. © 2003 Elsevier B.V. All rights reserved. Keywords: Erosion; Particle spin; Modelling; Metal target 1. Introduction Few studies have considered the possible interaction be- tween a spinning particle and a target during erosion, and yet, an understanding that particle rotation during impact may have a significant influence on erosion has been recog- nised for many years [1]. The importance of particle rotation should not be dismissed. However, practical considerations have effectively prevented the experimental quantification of such effects. Irregular-shaped particles accelerated in a fluid tend to rotate as a result of unbalanced forces acting on them. Only homogenous spherical particles will not rotate under such circumstances. It is possible that rotation of particles may affect the erosion rate and even the erosion mechanism when the particles strike a target surface. The first reported discussion of the potential significance of particle rotation ∗ Corresponding author. Tel.: +44-1634-883-495; fax: +44-1634-883-153. E-mail addresses: dt12@gre.ac.uk (T. Deng), m.s.bingley@gre.ac.uk (M.S. Bingley). 1 Tel.: +44-20-8331-8646; fax: +44-20-8331-8647. was by Finnie [1]. He presented theoretical results, based on a hypothetical distribution of rotational velocities, that indi- cated a pronounced effect of particle rotation on erosion rate. Work by Hutchings [2,3] was highly influential in suggest- ing that particle rotation may even affect the actual mecha- nism of material removal during erosion of ductile metals. Although his model does not explicitly refer to the effect of rotating particles striking a surface, it does consider the ef- fect of a particle rotating forwards (top-spin) or backwards (back-spin) after impact. Hutchings proposed three possible kinds of material removal mechanism [2,3] during the ero- sion of ductile metals, and suggested that particle rotation occurring after impact had a significant effect on the mech- anism in operation. It was suggested that an angular-type particle striking a surface may generate ‘Type I’ cutting or ‘Type II’ cutting (micro-machining) depending on the ro- tational direction of the particle following impact. For a spherical particle, it is generally assumed that ploughing de- formation is more likely. It was shown that these three differ- ent erosion mechanisms might lead to very different erosion rates [2,3]. More recently, Papini and Spelt [4,5] developed a rigid–plastic model of impact and used it to predict crater 0043-1648/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0043-1648(03)00536-2