Stylus Instrument Research Articles

On How to Determine Surface Roughness Power Spectra

Analytical contact mechanics theories depend on surface roughness through the surface roughness power spectrum. In the present study, we evaluated the usability of various experimental methods for studying surface roughness. Our findings indicated that height data obtained from optical methods often lack accuracy and should not be utilized for calculating surface roughness power spectra. Conversely, engineering stylus instruments and atomic force microscopy (AFM) typically yield reliable results that are consistent across the overlapping roughness length scale region. For surfaces with isotropic roughness, the two-dimensional (2D) power spectrum can be derived from the one-dimensional (1D) power spectrum using several approaches, which we explored in this paper.Graphical

Wear analysis of material measures and stylus probes in repetitive tactile calibration

Tactile industrial measuring instruments are frequently calibrated with material measures defined in ISO 5436–1 to ensure their function, determine their measurement uncertainty and assess the capability of measuring processes. Since these process needs to be repeated on a regular basis, the long-term stability of both material measures and the stylus is essential to enable a repeatable and reliable measurement. Since the tactile sampling of a material measure involves a mechanical interaction, there is the potential for wear when repetitive measurements are performed. We present a comprehensive experimental study on the effects of wear for different stylus instruments – including a reference plane scanning system and multiple skidded scanning systems. Multiple measurement methods are used to determine the state of the stylus and the surface of the material measure, both before and after their mechanical interaction. The impact of the wear on the accuracy of the results can be described, as can the connection between the wear and the hardness of the skidded probe. The study found that significant wear effects on surfaces with even >500 HV become qualitatively visible much earlier than they can be quantitatively detected, with extreme load cases of >1000 repetitive measurements at the same position being necessary to produce major wear influences. Thus, regular visual inspections in case of extensive repetitive measurements can be recommended, just as well as a low measuring force and a reduction of the number of measurements for measurement capability analysis to 12 measurements.

Calibration of the spherical tip radius of Rockwell hardness diamond indenters using a confocal laser scanning microscope

Abstract The precise form of an indenter is an essential part of hardness testing methods. It is therefore incumbent upon a user to ensure that the indenter geometry is calibrated before performing a hardness test. A geometric change of the tip radius by ±5 μm can cause a change of approximately 0.6 units of Rockwell hardness C scale (HRC) in a material with a hardness of 65 HRC. Keeping in mind that the measurement uncertainty is typically of the order of 0.3 HRC, it is critical to know the true value of the tip radius. Typically, tactile methods are used to determine the tip radius of a Rockwell hardness diamond indenter from the measured surface topography. Two main drawbacks of tactile measurements are the long duration of measurement and the limitation in capturing surface features of sizes smaller than the probe tip radius of 2 μm. Both could be overcome by using an optical 3D measurement. Confocal laser scanning microscopes (CLSM) allow a fast contactless 3D-mapping of the surface of Rockwell hardness diamond indenters and can be used to obtain geometric information such as the tip radius. The accuracy of these 3D measurements is still under question. Within this work, some of the influencing factors for fast 3D surface measurement are investigated. Using a CLSM with a 50x objective lens and a numerical aperture of 0.95, typical shape deviations of Rockwell diamond indenters are shown. Furthermore, an improved 3D based point cloud method for the evaluation of the indenter radius is presented. The aim of this paper is to explore the capabilities and limits of CLSM to obtain the 3D surface of a Rockwell hardness diamond indenter in order to calibrate the tip radius and compare their results with measurements from traceable stylus instruments.

Micro- and Nano-Roughness Separation Based on Fractal Analysis.

When describing the tribological behaviour of technical surfaces, the need for full-length scale microtopographic characterization often arises. The self-affine of surfaces and the characterisation of self-affine using a fractal dimension and its implantation into tribological models are commonly used. The goal of our present work was to determine the frequency range of fractal behaviour of surfaces by analysing the microtopographic measurements of an anodised aluminium brake plunger. We also wanted to know if bifractal and multifractal behaviour can be detected in real machine parts. As a result, we developed a new methodology for determining the fractal range boundaries to separate the nano- and micro-roughness. To reach our goals, we used an atomic force microscope (AFM) and a stylus instrument to obtain measurements in a wide frequency range (19 nm-3 mm). Power spectral density (PSD)-based fractal evaluation found that the examined surface could not be characterised by a single fractal dimension. A new method capable of separating nano- and micro-roughness has been developed for investigating multifractal behaviour. The presented procedure separates nano- and micro-roughness based on the geometric characteristics of surfaces. In this way, it becomes possible to specifically examine the relationship between the micro-geometry that can be measured in each wavelength range and the effects of cutting technology and the material structure that creates them.

A novel traceability route to the SI in roughness measurements at IPQ

A new traceability methodology for roughness stylus calibration is being developed in the National Metrology Laboratory of the Portuguese Institute for Quality (IPQ) using a high-precision displacement transducer. The calibration and dissemination of roughness standards measurements is one of the activities of IPQ. A stylus instrument is used to acquire the height values of the scanned points on the surface of the roughness standard. Defined according to ISO standards, namely the ISO 21920-2:2021, the integrated software calculates the roughness parameters that quantify the surface. A set of roughness parameters, measured after stylus calibration with different standards artefacts, as defined in ISO 5436-1:2000 has been evaluated. The need for the development of a new route for the metrological traceability in roughness, with faster calibration and better accuracy was also analyzed. The use of a displacement transducer, as reference, was the studied solution.

The wetting‐to‐nonwetting transition of CVD BN coatings deposited at different temperatures

AbstractBoron nitride (BN) coatings (thickness 20–40 μm) were prepared on graphite substrates by chemical vapor deposition, with precursors of BCl3 and NH3 (ratio of 1:4) and pressure of 500 ± 50 Pa. The influence of the deposition temperature (650°C–1250°C) on the wettability of BN coatings with deionized water was studied. The wetting angle rapidly increases at 1100°C–1250°C, and the wetting‐to‐nonwetting transition occurs. The crystal structure and surface morphology of the BN coatings were characterized by a stylus instrument, scanning electron microscopy, and transmission electron microscopy. Research shows that the contact angle or nonwettability increases with a higher degree of crystallinity and a lower surface roughness, which were both under the control of the deposition temperature since the pressure and gas flows were kept constant in this study. At a deposition temperature of 650°C–950°C, the increase in the degree of crystallinity dominates; at 950°C–1100°C, the increase in surface roughness takes over. At 1100°C–1250°C, the degree of crystallinity continues to increase, while the surface roughness decreases due to the advantage of nucleation and the breakage of large surface clusters into smaller clusters. This results in increases (650°C–950°C), then decreases (950°C–1100°C) and again fast increases (1100°C–1250°C) in the wetting angle between the BN coating and deionized water and finally in the wetting‐to‐nonwetting transition (1100°C–1250°C).

Measurement methods and fractal dimensions of blast-cleaned steel substrates

ABSTRACT Morphological parameters of steel substrates determine the adhesion of coatings and adhesives. Three different assessment methods (cross section image, contact stylus instrument, and stripe light projection) were applied to blast-cleaned substrates. A total of 12 surface configurations were generated with different abrasive materials. The fractal dimensions were estimated by means of the box-counting method. Design of experiment and ANOVA were applied to statistically analyze the relationships. Factors included abrasive type, surface preparation grade, surface roughness, and surface profile measurement method. Similar relative trends for the fractal dimensions resulted for the three measurement methods. The normalized values of the fractal dimensions were approximately twice as high for the cross section profiles compared to the ones from contact stylus and stripe light projection. Fractal values derived from contact stylus measurements showed the highest repeatability, whereas those derived from cross section images showed the lowest repeatability.

Miniaturized interferometric confocal distance sensor for surface profiling with data rates at ultrasonic frequencies

Point-wise measuring profilometers like the tactile stylus instruments or optical sensors are established measurement tools in science and industry to measure and characterize surface textures. We present a fiber-coupled laser interferometric confocal distance sensor for surface profiling. The sensor is characterized by small geometric dimensions and by its high lateral scanning speed. The ability to measure specularly reflecting and rough surface textures are demonstrated by performing several measurements on a sinusoidal standard as well as two roughness standards specified by different degree of roughness using various lateral scan velocities up to 75 mm s−1. These measurement results are compared to those obtained by a tactile stylus instrument used in the identical measurement environment as the introduced optical sensor. Finally, the ability for full-field measurements is presented.

The determination of fractal dimensions of blast-cleaned steel substrates by means of comparative cross-section image analysis and contact stylus instrument measurements

Morphological parameters of substrate surfaces determine the adhesion of coatings and pressure-sensitive adhesives. This paper is concerned with the assessment of fractal parameters by means of cross-section images and contact stylus instrument measurements of blast-cleaned substrates. Mild steel samples were prepared with different abrasive materials. Images were taken from a total of 12 surface configurations with an optical microscope. From each of the cross-section, a 2D profile of the steel surface was derived using the ImageJ image manipulation software. The fractal dimensions of these profiles were estimated by means of the box-counting method and then compared fractal values for 2D profiles taken from contact stylus measurements. Design of Experiment (DoE) was applied to statistically analyze the relationships. The factors considered included abrasive type, surface preparation grade, surface roughness, and most importantly for this paper, the surface profile evaluation method. The profile evaluation methods included cross-section analysis and contact stylus instrument measurements. Regardless of the method used to determine the surface profile, identical relative trends resulted for both measurement variants, with normalised values approximately twice as high for the cross-section profiles compared to the ones from contact stylus data.

A study of the manufacturing process of custom dimensional material standards using pulsed laser systems

New market requirements have led to the manufacturing of parts in the microscale. To produce this kind of parts, one of the options is to adapt the traditional manufacturing processes to work with dimensions of the order of micrometers. At this point, it is worth asking how it is possible to ensure with enough certainty that the dimensions of the parts meet the model requirements. Thus arises the need to use measuring instruments, with adequate traceability to the unit of length of the SI, capable of measuring on this scale. Among the different types, it seems that optical measuring instruments are going to be the most important in the near future. The traceability of this equipment is not currently standardized. One of the main problems is that there are no standard, cost-effective material references to give traceability to the measurement results obtained with these instruments at microscale. In this document, we aim to define the optimal process parameters for the manufacturing of custom material standards using ultraviolet laser systems. For this task, we have carried out a qualitative and quantitative analysis of the results using two different measuring instruments: an optical microscope and a stylus instrument.

Results of a Surface Roughness Comparison between Stylus Instruments and Confocal Microscopes.

This article presents the results of an LMM-R-2019 interlaboratory comparison. Such comparisons of different families of measuring instruments are one of the activities conducted among the calibration laboratories to maintain their ISO 17025 accreditation. Given that the study of surface roughness is becoming increasingly important in the field of dimensional metrology, the comparison focused on determining the Ra parameter on a pseudorandom metallic roughness standard using two types of measuring instruments: physical contact (stylus instruments) and optical (confocal microscopes). Among the aspects studied was whether the roughness measurements obtained using calibrated confocal microscopes could be compared with those using traditional methods since optical instruments obtain measurements more quickly and responsively than do stylus instruments. The results showed that roughness measurements using confocal microscopes are comparable with those from a traditional stylus instrument.

Surface Analysis in Additive Manufacturing Using Image Processing

Fused Deposition Modeling (FDM) is a type of additive manufacturing process where prototypes are developed by depositing layers on previously deposited layer of material. Surface roughness is an important factor in determining quality of produced parts. This work proposes a methodology to calculate the surface roughness of part manufactured using FDM process. The surface roughness values to be measured using conventional stylus instrument and Digital image processing technique. Stylus comes in direct contact with surface so it destroys the surface topography. Image processing is a non-contact method hence it overcomes this problem. A camera and directional lightings will be used to capture images of surface of specimens. These images will be analyzed and processed using various image processing techniques available in MATLAB image processing toolbox. Experimental results will be validated by comparing the results obtained by using image processing technique with conventional stylus system. The system is also proposed to inspect surface irregularities. Key Words: Surface roughness, image processing, MATLAB, FDM.

Surface roughness estimation techniques for drilled Surfaces: A review

Drilling is the process of removing the material and is a pre-processing step for various operations like reaming, boring, and tapping. The surface of the drilled hole has an impact on the performance of the component product. Surface roughness also determines the life cycle of the manufactured product. There are two ways for measuring surface roughness: Contact and non-contact methods. The contact approach employs stylus devices that must come into direct touch with the surface being studied. Stylus instruments are limited in their ability to handle the various geometrical parts that must be measured. The indirect measurement methods make use of optical devices that don't require any contact and are simple to use. This paper aims at reviewing various indirect methods to quantify the drilled surface roughness.

The Relationship between Roughness of Finished Wood Floors and Slip Resistance

The present study investigates the relationship between the roughness of beech wood and oak wood surfaces treated with oil and polyurethane coating and the slip resistance in dry, water-wet and oily conditions. Pendulum tests were conducted for slip resistance assessment, and roughness measurements were performed by stylus instrument using Ra, Rt, Rp, Rz and Rsm parameters for surface roughness evaluation. Slip potential in dry conditions was low for all finished wood floors studied. Contamination of the surface with water and oil reduced the slip resistance of finished oak and beech flooring. The strong negative correlation was found between slip resistance on dry finished flooring and roughness parameters Ra, Rz, Rt and Rp, and positive correlation between slip resistance on water-wet finished flooring and roughness parameters Ra, Rz, Rt and Rp. Moreover, the correlations between roughness parameters Ra, Rt, Rp and Rz and slip resistance were very similar, and the roughness parameters correlated more strongly with the slip resistance on dry and water-wet surfaces than with the slip resistance on oil-wet surface. Comparison of the slip potential classifications of finished wood floors based on pendulum data and based on Rz surface roughness parameters showed that in some cases the Rz parameter appeared to overestimate the slip potential of the floors in wet conditions. The results confirm previous research that roughness measurements should only be used as a guide and should not be used as the only indicator of the slip potential of wood flooring materials.

Wear behavior of Ni-P and Al2O3 electroless nano coating on aluminium alloy

Electroless Nickel (ENi-P) is the major evolving surface coating technique employed in today’s industries. This covering is the decision for some design applications with different actual attributes of EN coatings, for example, hardness, wears opposition, covering consistency and erosion obstruction. The major advantages of ENi-P and Al2O3 coatings are uniform coating thickness, improved wear and corrosion resistance, hardness, ability to deposit on surface activated non conductors etc. Typical anionic surfactant and various passive chemical additives and nano additives such as Al2O3 were added to the EN bath. Coating was carried out on Al LM6 alloy specimens. In this research work, Sodium Lauryl Sulphate (SLS) surfactant along with nano additives such as Al2O3 was added to the ENi-P bath. The effect of surfactant along with nano additives on surface properties such as corrosion resistance, wear properties, surface roughness, micro hardness and microstructure of electroless nickel-phosphorus and Aluminum oxide coating was investigated. The surface roughness of the coated specimens was measured using stylus instrument, microhardness was measured using vicker’s hardness tester, microstructure was studied using Scanning Electron Microscope (SEM) and wear test was measured using Pin on disc machine. The result obtained from the above tests clearly indicates that the surfactant and passive additives improves the surface finish, microhardness, and microstructure and wear rate of ENi-P and Al2O3 coatings significantly.

Comparative assessment of documentation referred to surface roughness measurement

The research relates to the field of metrological supervision, specifically to the control of surface roughness parameters. The authors analyzed the following regulatory documents: GOST R ISO 4287-2014 “Geometrical product specifications (GPS). Surface texture. Profile method. Terms, definitions and surface texture parameters”, GOST 25142-82 “Surface roughness. Terms and definitions”, GOST 2789-73 “Surface roughness. Parameters and characteristics”, GOST 9378-93 (ISO 2632-1-85, ISO 2632-2-85) “Roughness comparison specimens. General technical conditions”, GOST 27964-88 (ST SEV 6134-87, ISO 4287 / 2-84) “Measurement of roughness parameters. Terms and definitions”, GOST 19300-86 “Instruments for measurement of surface roughness by the profile method. Contact profilographs and profilometers. Types and main parameters”, GOST R 8.651-2009 ISO “State system for ensuring the uniformity of measurements. Contact (stylus) instruments for the measurement of surface roughness. Procedure of calibration”, GOST 9847-79 “Optical instruments for surface roughness parameters measuring. Basis parameters and types”, GOST R 8.700-2010 “State system for ensuring the uniformity of measurements. Method of surface roughness effective height measurements by means of scanning probe atomic force microscope”, which regulate the measured parameters of the surface roughness, instruments that measure these parameters. In the course of a comparative analysis of the values of the parameters of existing devices and the values of the parameters of devices prescribed in the standards, a summary table was formed, and the problem of controlling nanoparameters and nanocoatings was also identified. The existing instrument base for monitoring surface roughness allows measuring parameters with high accuracy and within wide limits, but the regulatory framework on the territory of the Russian Federation is outdated and does not allow the use of some modern types of instruments. In this regard, it is necessary to update the requirements of GOSTs for the modern capabilities of technology and control over roughness parameters.

Surface Roughness Measurement Using Light Sectioning Method and Computer Vision Techniques.(Dept.M)

The development of new industries has led to a requirement for super-smooth surfaces and for the ability to measure surfaces of industrial parts accurately; therefore, the measurement of engineering surface roughness is becoming increasingly important. In this work, a new approach is introduced to measure surface roughness by combining a light sectioning microscope and a computer vision system. This method has the advantage of being non-contact. The light sectioning microscope is used to view roughness profiles of the specimens to be measured and the vision system is used to capture images for the viewed profiles. A special program (named SRLSVision) has been totally developed in-house using MatlabTM software to analyze the captured images through two modules. The first module is used to extract the roughness profiles from the captured images by applying various image processing and computer vision algorithms. The second module is used to calculate the ISO roughness parameters (22 parameters) from the extracted profiles. The system has been calibrated for metric units and verified using a standard specimen. In addition, the system was used to measure various samples: machined by different operations and the obtained results were compared with the results obtained by measuring the same samples using a stylus instrument. The accuracy of the system proved to be within ±5.5% compared with the stylus instrument readings.

A Novel Light Sectioning Vision System for A Three Dimensional Surface Roughness Assessment (Dept.M)

Standard roughness measurement procedures depend heavily on stylus instruments which have only limited flexibility in handling different parts. On the other hand, optical non-contact techniques are very interesting for 3D characterization of sensitive and complex engineering surfaces. In this study, a new ap proach is introduced to measure surface roughness in three dimensions by combining a light sectioning microscope and a computer vision system. This approach has the advantages of being non-contact, fast and cheap. A prototype version of a user interface program, currently named SR3D Vision, has been developed to manage three dimensional surface roughness measurements. A light sectioning microscope is used to view roughness profiles of the specimens to be Measured and the vision system is used to capture images for successive profiles. This program has been totally developed in-house using MatlabTM software to analyze the captured images through four main modules: (Measurement controller, Profile or surface extraction, 2D roughness parameters calculation and 3D roughness parameters calculation). The system has been calibrated for metric units and verified using standard specimens. In addition, the system was used to measure various samples machined by different operations and the results were compared with a commercial software and a web-based surface metrology algorithm testing system. The accuracy of the system was verified and proved to be within ±4.8% compared with these systems.

The feasibility of iodine-supported processing for titanium with different surfaces

BackgroundThe reduction of microbial infections can substantially improve the success of implant surgery. The iodine-supported implants that were developed by us for infection prevention were featured at the recent International Consensus Meeting on Musculoskeletal Infection and were partly incorporated into the consensus guidelines. For future clinical application, we examined (1) whether iodine can be added to metals with different surface roughness, (2) differences in surface roughness before and after processing, and (3) the effect of sterilization on the iodine content. MethodsFour Ti-6Al-4V metals were prepared with different surface roughness values by polishing, blasting and plasma spraying. Before and after processing, the surface structure of metals was observed using a scanning electron microscope and stylus instruments. Before and after sterilization, iodine contents were measured by X-ray fluorescence spectroscopy. ResultsAfter processing, sufficient iodine contents with an antimicrobial effect were detected for each metal. These iodine contents decreased after sterilization but were higher than the lowest content of iodine observed to have an antimicrobial effect in a previous study, indicating that the antimicrobial effect persists even after sterilization. After processing, surface roughness was greater for polishing metal. With general surface processing, iodine processing was possible. ConclusionsOur results indicated that surface roughness is affected by the processing method and that the iodine content should be set according to the sterilization method. Considering these factors, iodine processing can be used for clinical applications.

Measurement of groove depth standards in the range 1 μm up to 1 mm (EURAMET project 1407)

A comparison measurement between 10 national metrology institutes on two types of depth setting standards was conducted using mostly tactile but also two optical instruments for measurement. Three etched silicon standards with depths of 5, 20 and 50 μm and one diamond turned nickel coated copper standard with depths of 200, 600 and 900 μm were measured. The cross section of the grooves was trapezoidal. Most of the participants confirmed their CMC entries. Since many measurements had to be made, contamination of the standards and heavy wear on the standards were also observed after the comparison was completed. The wear consists of indentation marks from stylus instruments on both types of standards and as many as 70 scratch marks on the nickel coated copper artefact used. This indicates that the contact pressure of the tactile measuring devices used by some partners was too high. This can be caused by a too high probing force or a too small probing tip radius. Thus, for future comparisons the actual probing force and actual tip radius need to be measured during the comparison by the participants to assure that the recommended values (2 μm tip radius and 0.7 mN probing force) are not exceeded. The recently published German standard DIN 32567-3 "Determination of the influence of materials on the optical and tactile dimensional metrology - Part 3: Derivation of correction values for tactile measuring devices" describes methods to do both.Main textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).