# Frictional Behaviour of the Microstructural Surfaces Created by Cylindrical Grinding Processes
## 2 Structural Surface Creation and Their Characteristics  
### Creation of Microstructural Surface by Sylindrical Grinding  
Grinding is an effective mechanical machining process, which can process high precision and tight tolerance of micro structural surface. In the component preparation, the components were first polish-ground to get a smooth surface and then textured by cylindrical plunge grinding. The wheel surface pattern was generated by a specified dressing operation, in which the diamond dresser cut across the grinding wheel surface from right to left and from left to right at the same dressing depth. Thus, a cross helix gouge pattern is formed on the surface of the grinding wheel. During grinding, the grinding wheel will print its surface pattern on to the ground surface, forming designed dimple microstructural texture, as shown in Figure 1. The mechanism of surface microstructure formation has been presented in previous investigation [17]. Figure 1: Microstructural surface creation by grinding. According to previous study on microstructural surface generation in grinding [17], the geometrical characteristics of ground surface structure are mainly controlled by the wheel dressing and component grinding parameters. The depth of grooves is mainly controlled by grinding depth, while the geometry sizes of structural gauge length and width are also influenced by grinding depth. The structural axial interval is mainly decided by the dressing feed \(f_{d}\), while the structural circumference interval \(L\) is determined by the rotational speed ratio between workpiece and wheel \(n_{w}/n_{s}\). According to the kinematic relation of grinding cutting actions, the proportion of structural gauge length in a grit cutting pitch length should be the same as the proportion of structural gauge width in a dressing feed. According to the mechanism of microstructure groove formation, the microstructure geometric feature sizes can be expressed by the following parameters of the dressing and grinding processes [17]:  
\[l_{w}=L\times(1-\frac{2 xx}{f_{d}})=L\times(1-\frac{2\sqrt{{r_{d}}^{2}-\left({ r_{d}}-{h_{s}}+{a_{p}}\right)^{2}}}{f_{d}}) \tag{1}\]  
\[b_{w}=f_{d}\times(1-\frac{2 xx}{f_{d}})=f_{d}\times(1-\frac{2\sqrt{{r_{d}}^{2}- \left({r_{d}}-{h_{s}}+{a_{p}}\right)^{2}}}{f_{d}}) \tag{2}\]  
where  
\[L=2\pi R_{s}q=v_{w}/n_{s}=2\pi R_{w}\times n_{w}/n_{s} \tag{3}\]  
and  
\[xx=\sqrt{{r_{d}}^{2}-\left({r_{d}}-{h_{s}}+{a_{p}}\right)^{2}}=\sqrt{\left({ h_{s}}-{a_{p}}\right)\left({2r_{d}}-{h_{s}}+{a_{p}}\right)} \tag{4}\]  
\[{h_{s}}={r_{d}}-\sqrt{{r_{d}}^{2}-\left({f_{d}}/{2}\right)^{2}} \tag{5}\]  
Equations (1)-(5) present the structural length \(l_{w}\), structural width \(b_{w}\), circumferential pitch length \(L\) and half minimum uncut plateau length on the workpiece in axis direction \(xx\); here, \(f_{d}\) is the dressing feed, \(r_{d}\) is the dresser tip radius, \(a_{p}\) is the grinding depth, \(h_{s}\) is the section depth of helix grove on the grinding wheel surface, \(q\) is the ration of \(v_{w}/v_{s}\), \(v_{s}\) is the grinding speed, \(v_{w}\) is the work-material speed, \(R_{s}\) is the radius of grinding wheel, \(R_{w}\) is the radius of workpiece, \(n_{w}\) is the rotational speeds of workpiece, and \(n_{s}\) is the rotational speeds of grinding wheel. The structural surface components were produced on a Kellenberger cylindrical grinding machine. The micro structural gauge depth was controlled by the grinding depth of cut or infeed in plunge grinding. The geometry of micro structural length and width was determined by the dressing strategy, speed ratio, tip radius and grinding depth. The dressing and grinding operations were executed under same constant wheel spindle rotational speed (1344 rpm).