Regardless of whether industrial or biomedical applications are considered, the potential adverse effects associated with wear can dramatically affect the lifespan of a device. The use of 3D optical scanners has emerged as a non-destructive and highly accurate method for conducting wear analysis on a wide range of sample types.
The Importance of Wear Analysis
There are numerous wear mechanisms that can result in a progressive loss of material, as well as cause other surface modifications following mechanical contact between the surfaces of two objects. These mechanisms include abrasion, corrosion, erosion and plowing, to name a few; each of which are associated with causing different effects on the objects. The continuous monitoring of wear progression therefore plays a significant role in how manufacturers of various devices, which can range from mechanical components to medical prostheses, can improve the efficiency of their products.
Effective Tribological Tests
The most effective tribological test is one that exhibits the highest degree of realism, which means that the best test is one that most closely imitates the conditions of the real application. The main reasons that manufacturers perform tribological tests is to rank the applicability of their materials when applied to existing equipment, select the best materials for new applications, characterize the wear and friction properties of the test material and investigate the wear mechanisms that would be expected when the object is used for its respective application.
Traditional Methods of Wear Analysis
When analyzing abrasive wear, some of the most common analytical models include those that place the sample material in contact with a countersurface, such as a rotating wheel or disk. Erosive wear, which is typically caused by the bombardment of hard particles onto a material’s surface, can be classified according to the propulsion of the eroding particles, achievable through the use of a fast gas, liquid stream, jet impingement or gas-blast method.
Obtaining 3D Wear Information
The majority of measurement techniques used to quantify wear in samples are based on two-dimensional (2D) stylus measurements. While these techniques are capable of characterizing wear based on a single trace measurement taken from the sample surface, they are often limited in their sensitivity for detecting peak and valley differences, as well as their inability to provide users with spatial structure information.
To resolve these limitations, non-contact three-dimensional (3D) surface measurement systems, such as optical profiling, have improved the visualization and quantification of wear in sample materials. Some optical techniques that have been successfully applied for wear analysis purposes include universal measuring microscopes, Fourier profilometry and scanning profilometry.
Advantages of 3D Optical Scanners
Both optical 2D profilometers and 3D scanners function according to similar principles based on optical range-finding techniques. Optical 3D scanners are advantageous for wear analysis purposes as a result of the reduced errors associated with inhomogeneity or liquid absorptions, as well as their high accuracy that reaches up to 10 micrometers (µm) in resolution. Furthermore, 3D optical scanners are non-invasive and non-contact devices that preserve the topography and morphology of the target surface throughout the analysis procedure.
3D Optical Scanners and Wear Analysis
The optical 3D scanning process can vary depending on which scanner is used; however, for wear analysis purposes, it is recommended that devices based on confocal scanning microscopy and triangulation are used, as these methods have been shown to provide users with results of the highest resolution, precision and accuracy.
In a 2017 Materials study, researchers applied 3D optical scanning technology to an industrial application in an effort to assess the wear resistance of mixing blades that had been mounted onto a two-star planetary concrete mixer. The portable 3D laser scanner the researchers used provided them with real-time digitalized 3D models of the of the full worn object. This 3D image included a 3D wear map of the total amount of material loss at five different points, as well as its distribution over the surface of the specimen, during the tribology test. When compared to traditional 2D contact measurements, a maximum difference of 80 µm was obtained.
The same 2017 paper also investigated the biomedical application of optical 3D scanners by evaluating the loss of material of certain knee joint prostheses when exposed to the stress of a knee mechanical simulator. While no significant differences were found to exist between the 3D wear maps and gravimetric tests for this type of sample, the researchers remain confident that the use of a 3D optical scanner provided them with more accurate information on the 3D wear distribution and material loss.
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- Rossler, T., Mandat, D., Gallo, M. H., POchmon, M., & Havranek, V. (2009). Optical 3D methods for measurement of prosthetic wear of total hip arthroplasty: principles, verification and results. The Optical Society Publishing 17(15); 12723-12730. DOI: 10.1364/OE.17.012723.
- Valigi, M. C., Logozzo, S., & Affatato, S. (2017). New Challenges in Tribology: Wear Assessment Using 3D Optical Scanners. Materials 10(548); DOI: 10.3390/ma10050548.