Ultrasonic measurements of surface roughness

Abstract

Pulsed ultrasound propagating in water was used at megahertz carrier frequencies (nominally 10-50MHz) to reflect and scatter from rough surfaces in the same way as light. We have considered noncontact ultrasonic techniques as complementary to optical techniques in several ways: (a) for specificapplications such as wet surfaces, (b) for rougher surfaces with average roughness, R(a) ≥ 0.1 µm, and (c) for (simultaneous) profilometry by time-of-flight measurements. Stylus and ultrasonic data are compared. An example of application to the manufacturing environment is for on-line, real-time sensor feedback and process control in the cutting or grinding of metals and ceramics.

Evaluation of the height of internal periodic triangular surfaces by ultrasonic backscatter

“…The geometrical features of periodic surfaces can be immediately evaluated by using the corresponding diffracted modes of diffraction grating theory (Blessing et al, 1993). The sharp discontinuities or valleys in the frequency spectra as in diffraction grating in optics (Wood, 1902) have been used to identify the periodic profile parameters as reported by Claeys et al (1983).…”

Ultrasonic evaluation of the pitch of periodically rough surfaces from back side

“…Since a periodic surface functions as an acoustic diffraction grating, its geometrical features can be immediately identified by analyzing the associated diffracted modes (Blessing, 1993). Wood anomalies (Wood, 1902) have been used to determine geometric parameters of a periodic surface.…”

Continuous-wave ultrasound reflectometry for surface roughness imaging applications

“…In addition, because of the contact, there is the risk of damage to the surface of the item being tested. These observations have provided the impetus for many investigators to seek a variety of imaging technologies [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] for the inspection and measurement of surface roughness. The ultimate goal in this line of research is to quantitatively evaluate the roughness of a surface.…”

“…However, most optical methods are still limited to the laboratory implementation due to the difficulty of adapting them to harsh manufacturing environments as well as the cost of constructing such systems. On the other hand, ultrasonic techniques have been suggested for noncontact measurement and inspection of surface roughness [5].…”

“…The signal amplitude Ŝ is directly related to Λ, which in turn, is related to the variations in the axial direction such that (5) Surface roughness requires determining the relative roughness z − z 0 from Eq. (5) such that (6) For this transducer, the ultrasound wavelength in water is λ = 0.5 mm.…”