Definition
Shot peening roughness meter is a special measuring instrument used to quantify the surface morphology characteristics after shot peening treatment. Shot peening is a surface treatment process that impacts the surface of the workpiece through a high-velocity projectile flow, introducing a residual compressive stress layer and changing the surface geometry. The instrument's primary function is to accurately evaluate the surface roughness parameters formed after shot peening, providing critical data support for process control and quality verification. The measurement results are usually combined with relevant industry standards (such as SAE J448, AMS 2432, etc.) to determine the compliance and consistency of the shot peening process.
Principle
The core working principle of the shot peening roughness meter is based on the contact profilometry method. The instrument drives a probe with a specific tip radius to perform lateral scanning at a constant speed on the surface to be tested. The probe is displaced vertically as the surface profile undulates, and this displacement is converted into an electrical signal by an internal sensor such as an inductive or piezoelectric sensor. After signal amplification and digitization processing, the system can reconstruct the microscopic contour curves of the surface. On this basis, a series of statistical parameters characterizing surface roughness, such as arithmetic mean deviation (Ra), maximum profile height (Rz), etc., are calculated through built-in algorithms. Its basic formula can be expressed as:
Ra = (1/l) ∫0l |y(x)| dx
where l is the sampling length, and y(x) is the value of the contour deviating from the midline.
Measurement method
Peening roughness measurement follows a standardized operating procedure. Appropriate sampling length, rated length, and probe specification are selected according to the standard or specification before measurement. When measuring, the instrument performs multiple scans at a typical location in the peening area, usually perpendicular to the main direction of the peening flow, to obtain representative data. During the measurement process, it is necessary to ensure that the sample is stable and fixed, and that the probe has a moderate contact force with the surface to avoid scratching the surface or causing measurement errors. Once the raw profile data is obtained, the instrument software performs profile filtering (e.g., Gaussian filter) based on the selected standard, separates the roughness components, and automatically calculates the predetermined parameter set. A complete measurement report typically contains averages from multiple locations and their degree of discreteness to provide a comprehensive picture of surface uniformity.
Influencing factors
The accuracy and repeatability of measurement results are affected by a variety of factors. In terms of process parameters, the material, hardness, size, shape, shot peening strength, coverage, etc. of the projectile directly determine the morphological characteristics of the final surface. Instrument factors include the tip radius and wear state of the probe, the linearity and resolution of the sensor, the calibration status of the instrument, and the accuracy of the mechanical guide. Operating factors include the way the sample is clamped, the choice of measurement position, the direction of the measurement relative to the peening texture, and environmental vibration. In addition, the data processing settings such as evaluation criteria, filtering parameters, and sampling length used will also have a direct impact on the final reported parameter values. Therefore, controlling these variables and noting them in the report is fundamental to ensuring the comparability of the measurement results.
Applications
Shot peening roughness meters have a wide range of applications in high-end manufacturing. In aerospace, it is used to monitor the surface condition of key components such as engine blades, landing gear, and fuselage structural parts after shot peening to ensure their fatigue performance. In the automotive industry, it is commonly used to verify the quality of shot peening of parts such as connecting rods, gears, and springs. In energy equipment manufacturing, it is used to evaluate turbine discs, blades, and various metal components subjected to alternating loads. In addition, in general machinery, mold manufacturing and materials research laboratories, this instrument is also an important tool for evaluating the effect of surface treatment process and studying the relationship between surface morphology and material properties. The measurement data is one of the key quality indicators that connect the shot peening process parameters with the service performance of the components.
Selection considerations
Choosing a suitable shot peening roughness meter requires comprehensive consideration of technical specifications and application requirements. The core parameters include vertical and horizontal measurement ranges, resolution, and value errors, which meet the accuracy requirements of the relevant standards for shot peening surface measurement. The drive platform of the instrument should have good stability and vibration resistance. Probe systems are available in a variety of sizes to accommodate different levels of sharpness on the shot peening surface. The software functions should support mainstream international standard parameter calculations, and provide capabilities such as contour drawing, statistical analysis, and data export. Ease of operation, environmental adaptability, and subsequent calibration and maintenance services are also important considerations. Users should conduct a comprehensive evaluation based on their main workpiece material, typical roughness range, production cycle requirements, and laboratory conditions to select the right measurement solution.