Arithmetic Average Roughness Research Articles

A study on surface reproduction of dental stone models. Detail reproduction test of dental stone and its surface smoothness.

A study was made of the detail reproduction test and roughness of the smooth surface of dental stone as a preliminary approach for examination of the surface reproduction of dental stone models made through combination of various impression materials.Measurement of the detail reproduction test was based on ISO 1563, while that of surface roughness was carried out using both an improved non-contact photogenic surface roughness analysis system and a contact surface roughness analysis system.The study produced the following findings : 1) It was clarified that almost all dental stones were capable of reproducing features 20 μm in size.2) There was a correlation between the relative reflection (RR) of the model surface and its arithmetic average roughness (Ra).A correlation was also found between RR and average angle (R Oa), and between RR and average wavelength (Rλa).

Wear behaviour of nitrogen-implanted and nitrided Ti6Al4V alloy

The comparison between the wear behaviour of nitrogen-implanted Ti6Al4V alloy (where the alloy composition is given in approximate weight per cent) and that of nitrided Ti6Al4V alloy is reported. Both treatments were carried out at temperatures from 573 to 973 K on lapped surfaces (arithmetic average roughness R a ≈ 0.01 μm); in order to compare roughness effects, nitriding was also carried out on rougher samples (R a ≈ 0.25 μm). An improvement in wear resistance for lapped surfaces was noted after implantation at 573 K or higher temperatures and after nitriding at temperatures over 773 K only; however, at 873 K, nitriding was more effective than implantation. Rough nitrided surfaces showed better wear resistance than lapped nitrided surfaces or lapped implanted surfaces. Most probably the improvement in wear resistance on implanted samples is due to a reduction in friction induced by chemical modification of the surface as a result of oxide and TiN. Scanning electron microscopy observations which show subsurface voids and coalescence are in good agreement with a wear model previously reported. As implantation preserves the surface finish, a possible application is suggested.

Bearing length ratio applied to the measurement of engine cylinder-bore wear

Surface profilometry can be used as a wear measurement technique on components too cumbersome for weight loss methods. Engine cyclinder-bore wear is estimated from the bearing length ratio parameter computed from axial profiles of the cylinder-wall. The system approach is used to provide insight to the impact of piston ring forces on cylinder-bore wear. New and worn values of arithmetic average roughness and bearing length ratio parameters for each of three case studies representing 12, 31 and 700 operating hours are presented. Estimates of radial wear for typical internal combustion engine cylinder-bores are included

Investigation of the wear mechanism of carbon-fiberreinforced acetal

The friction and wear characteristics of acetal reinforced with 25 wt.% of randomly dispersed carbon fibers were investigated and compared with those of the base resin. The addition of carbon fibers to the polymer decreased the coefficient of friction and wear rate for the composite material sliding against a hardened and ground steel disk for extended periods of time. A number of surface topography parameters pertinent to the wear process, i.e. arithmetic average roughness, autocorrelation function, asperity density, tip radius of curvature, distribution of the radii of curvature and heights of asperity peaks, and ordinale heights, were calculated and evaluated for the sliding surface of the disk. The worn surfaces of filled and unfilled polymer pins were examined by scanning electron microscopy to investigate the probable wear mechanism for these materials. It was found that the wear of reinforced polymers proceeds by the pulling-out of the broken and worn fibers.

Surface roughness of two dental amalgams after various polishing techniques

1. In comparison with standard polishing after 24 hours, no advantage is gained by using an abrasive paste after 10 minutes. Polishing after 24 hours produced a significantly smoother surface for both amalgam alloys on both the simulated proximal and occlusal surfaces. 2. The standard polishing procedures after 24 hours produced a smoother surface than any of the immediate finishing procedures tested. 3. The high-copper amalgam was signijficantly rougher with initial carving and immediate finishing, but surfaces of both alloys were equally smooth when polished after 24 hours. 4. Both amalgam alloys, when condensed against a new matrix band lacked smoothness when compared to the surfaces obtained by finishing after 24 hours. 5. There was a high correlation between arithmetic average roughness and average maximum peak height as quantitative measurements of surface texture.

Studies of the Surface Geometry of Fibers

The background for a study of surface geometry, among other surface properties of fibers, is briefly surveyed. By the adaptation of an instrument designed for measure ments in the metals industry, exploratory trials were conducted on specimens of a number of fiber types. Only ranges of readings of "arithmetic average roughness," rather than discrete values, were obtamable, but these results were promising in showing that widely different fiber types—viscose rayon, woll, and raw silk—occupied distinct levels. Indications were that the directional character of the scales on wool fibers could be detected Further experimentation, still of an exploratory nature, was con ducted with refined equipment providing means for graphically recording the Irregular ities of fiber surfaces. Comparison of tracings obtained in three successive measure ments on a single specimen of viscose rayon shows that the tracings are characteristic of the fiber surface and not merely, records of extraneous "noise."