وابستگی به دما و تاثیر آن بر روی زبری سطح در ماشین کاری با جریان ساینده Temperature Dependence and Effect on Surface Roughness in Abrasive Flow Machining

Introduction Abrasive flow machining (AFM) is a non-traditional finishing process, which possesses excellent capabilities for finishing complicated surface and inaccessible regions of a workpiece [1]. In AFM, an abrasive-laden polymeric medium is extruded under pressure through the surface to be machined or the restrictive passage formed by the workpiece and fixture assembly. The more restrictive the passage is, the faster media flow speed is. In this case, the stronger AFM action becomes. On the other hand, the media is sheared seriously when it is extruded trough the narrow passage. The temperature of media rises drastically and the viscosity of media decreases at the same time. The action of AFM gets weak. The exact mechanism of AFM has been understood due to the complicacies of effect factors. Hence, it is of great practical and theoretical interest to study temperature rise during the AFM process. The theoretical and experimental determination of thermal properties of medium is carried out by Fletcher and Fioravanti [2]. Davies and Fletcher [3] experimentally found that viscosity of medium is significantly affected by temperature. Viscosity of highly viscous medium reduces drastically even with a small increase in temperature (2-10°C). R.K. Jain and V.K. Jain proposed a simple model analysis to understand thermal phenomenon of AFM and thereby to predict temperature change during the process [4]. Moreover, the rheological properties have been studied by some reports [5,6]. The experiments show that the viscosity of medium is seriously influenced by temperature. In this paper, the real-time temperature change is measured and recorded by a control and measure system with computer. Experiments are performed at setting high temperatures. The effect of temperature on surface roughness is studied directly. This paper is organized as following. Next section mainly introduces the experiment system of abrasive flow machining. In the following section, the experiment procedure is discussed in detail. Then analysis and discussion are given. Finally conclusion is made. Analysis and Discussion Fig. 6 shows the surface roughness of workpieces machined by AFM. For the workpiece with Ra 4.8 μm initial surface roughness, the surface roughness may decrease two grades after AFM at below 40°C and one grade at above 50°C. The machining action of media decreases with increasing in temperature. Conclusions This research first reveals the variable trend of temperature during the AFM processing. The surface roughness of surfaces finished by AFM at different temperatures is studied. The following conclusions have been derived from the above study: (1) Effect of temperature on surface roughness of the surfaces machined by AFM is serious. The machining action of AFM is strong at low temperature and weak at high temperature. The efficient machining should be below 40°C, the most efficient machining should be below 25°C. (2) Without control of temperature, the machining action produces mainly from first a few cycles. The more cycles aren’t useful to improvement the surface roughness. (3) In order to realize a stable and efficiency machining, the temperature must be controlled during the AFM process. The roughness is good with increasing number of cycles after the temperature is controlled at low.