Optical 3D Measurement System Research Articles

Assessment of process chain suitability of the optical 3D measuring system by using influencing factors for measurement uncertainty

Optical 3D measuring systems serve as indispensable tools for the measurement and quality control of complex objects feeding process chains in industrial information integration. However, the accuracy of 3D measurements is influenced by a multitude of parameters, and the associated measurement uncertainties and influential factors remain insufficiently researched. This study investigates the effects of measurement object properties and software on measurement outcomes. Specifically, we examine seven geometries (diameter, distance, roundness, concentricity, flatness, parallelism and verticality) and four influencing factors (surface roughness, coating, polygonization, and interpolation). Our analysis employs variance analysis and compares the results with those obtained through linear regression using machine learning. In conclusion, the analysis of measurement uncertainty for optical 3D measurement systems in the assessment of seven distinct geometric characteristics provides a framework for determination of process chain suitability of the optical 3D measuring system.

Mechanical and tribological properties of 5A06 aluminum alloy at low temperature

There are significant differences in the mechanical and tribological properties of 5A06 aluminum alloys subjected to a wide temperature range, and the related research has received very limited attention so far. In this paper, the mechanical properties of 5A06 aluminum alloy were obtained by tensile test at temperature as low as 77K, which laid a foundation for analyzing its tribological properties. Then, dry linear reciprocating sliding wear tests were performed on a ball-on-disc tribometer to explore the friction behavior and wear mechanism of 5A06 aluminum alloy at different temperatures from low temperature (173K) to room temperature (293K). Finally, the wear morphology and chemical composition of the worn surface were characterized by an optical 3D measurement system and a scanning electron microscope equipped with an energy dispersive spectroscopy. The results indicate that the ambient temperature affects the tribological properties of 5A06 aluminum alloy by changing its mechanical properties and the dissipation of friction heat. Compared with 293K, the coefficient of friction decreases by 14.66% and the wear rate decreases by 70.79% at 173K. The main wear mechanisms of 5A06 aluminum alloy are delamination wear and oxidation wear at 293K and 273K, and a combination of abrasive wear, adhesive wear and oxidation wear at 223K and 173K.

Investigations on the Experimental Setup for Testing the Centric Tensile Strength According to ASTM C307 of Mineral-based Materials

Centric tensile tests often exhibit high standard deviations due to various factors, hence various test setups have been developed in the past. Based on the specifications in ASTM C307-18, the experimental setup was further developed to reduce the standard deviation resulting from the test setup itself and thus to obtain reliable, reproducible test results. Furthermore, it has been investigated, whether the test setup is suitable for materials of low strength. In the further developed experimental setup three mineral-based materials with tensile strengths in the range of 0.4 to 5.9 MPa were examined and compared to ASTM C307-18. For this purpose, the optical 3D-measurement system ARAMIS® and a positioning adapter designed for the specimen geometry were used to validate and verify the developed experimental setup and to ensure a consistent position of the specimen. For the low strength mineral-based materials tensile strength tests could be implemented and recommendations for the test parameters test speed, preload and required number of specimens could be developed.

Raster angle impact on FDM-based additive manufactured fluidic oscillator

The interior surface of a fluidic oscillator produced by FDM (Fused Deposition Modeling)-based additive manufacturing is associated with a directional pattern corresponding to the 3D printing raster angle. The present research explores the impact of raster angle α = 0 , 45, and 90° from three commercial 3D printers versus a CNC machined oscillator. The surface is characterized using an optical 3D measurement system. The performance of the emanated jet is assessed using hot-wire anemometry downstream of the outlet nozzle, and the required supply pressure is measured at the actuator inlet. Printer P 1 with an actuator average roughness S ̄ a = 8 . 3 μm and printer P 2 with S ̄ a = 29 . 9 μm inherit clear raster patterns while actuators printed by printer P 3 , more economical compared to printer P 1 , do not exhibit an evident pattern related to raster angle with S ̄ a = 17 . 7 μm. Regardless of the type of printer and associated surface texture, oscillators with 0° raster angle provoke higher jet spreading accompanied by a lower required supply pressure compared to the milled sample. Strikingly, the performance for P 3 0 and P 3 90 is noticeably superior to the other printed oscillators and surpasses the milled actuator in terms of jet switching quality. Power-law fit is depicted to estimate the jet spreading versus surface roughness for each raster angle.

Effect of temperature on evaporation dynamics of sheep's blood droplets and topographic analysis of induced patterns

To characterize various induced phenomena and the blood of healthy sheep using several parameters, the evaporation dynamics of 72 drops of sheep blood evaporated at several temperatures: 23, 37, 60, and 90 °C on glass hydrophilic substrates were studied. This allows the prediction of the sheep blood pattern, knowing the surface temperature and vice versa. To determine the variation in the Marangoni number between the center and the triple line, an infrared thermography method was used to measure the temperature variation along the surface of the drop. Simultaneously, a high-performance camera was used to measure the variation in the height of the drop during the evaporation using a superior algorithm software for image analysis, drop shape analyzer, under controlled conditions (Humidity = 40%, Tatm = 23 °C). The study of the evaporation dynamics and pattern formation shows the effect of temperature on the flow circulation inside the drop, resulting in the final deposit. The results showed two categories corresponding to two different evaporation phenomena induced by the thermal Marangoni effect. Furthermore, to transform the induced pattern of sheep blood evaporation into a 3D image, a topographic study was performed using a highly accurate, fast, and flexible optical 3D measurement system. The topographic parameters were subsequently extracted from these 3D images. The statistical study showed a good correlation between the topographic parameters and the surface temperature, and a significant difference between each temperature group for each parameter.

Additive manufacturing impact on a fluidic oscillator with respect to surface roughness

This experiment investigates the impact of areal surface roughness Sa on the performance of a fluidic oscillator produced by additive manufacturing (AM) versus the conventionally machined samples. The fluidic oscillator used is a classical curved (Type-II) Sweeping Jet (SWJ) actuator with two feedback channels. The interior surface finish of each sample is characterized using an optical 3D measurement system. The performance of the emanated jet is evaluated using hot-wire anemometry downstream of the outlet nozzle while the required supply pressure is recorded using a high-frequency pressure transducer at the actuator inlet. A bifurcated velocity profile of the external flow typical for the SWJ is observed in all cases, irrespective of the manufacturing process and surface roughness Sa< 20 μm. The jet velocity profiles are found to be satisfactorily self-similar, confirming that the surface roughness in the examined range does not qualitatively change the internal flow dynamics. However, increasing the surface roughness causes a reduction in the output jet spreading and a concomitant increase in the jet oscillation frequency. A linear model is presented to estimate the jet spreading versus the surface roughness.

Study of Friction and Wear Effects in Aluminum Parts Manufactured via Single Point Incremental Forming Process Using Petroleum and Vegetable Oil-Based Lubricants.

This paper focuses on studying how mineral oil, sunflower, soybean, and corn lubricants influence friction and wear effects during the manufacturing of aluminum parts via the single point incremental forming (SPIF) process. To identify how friction, surface roughness, and wear change during the SPIF of aluminum parts, Stribeck curves were plotted as a function of the SPIF process parameters such as vertical step size, wall angle, and tool tip semi-spherical diameter. Furthermore, lubricant effects on the surface of the formed parts are examined by energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) images, the Alicona optical 3D measurement system, and Fourier-transform infrared spectroscopy (FTIR). Results show that during the SPIF process of the metallic specimens, soybean and corn oils attained the highest friction, along forces, roughness, and wear values. Based on the surface roughness measurements, it can be observed that soybean oil produces the worst surface roughness finish in the direction perpendicular to the tool passes (Ra =1.45 μm) considering a vertical step size of 0.25 mm with a 5 mm tool tip diameter. These findings are confirmed through plotting SPIFed Stribeck curves for the soybean and corn oils that show small hydrodynamic span regime changes for an increasing sample step-size forming process. This article elucidates the effects caused by mineral and vegetable oils on the surface of aluminum parts produced as a function of Single Point Incremental Sheet Forming process parameters.

Single column plate plus other column lag screw fixation vs. both column plate fixation for anterior column with posterior hemitransverse acetabular fractures - a biomechanical analysis using different loading protocols.

Open reduction and internal fixation of both columns is considered the treatment of choice for displaced anterior column with posterior hemitransverse (ACPHT) fractures in non-geriatric patients. Plate fixation of one column combined with lag screw fixation of the other column allows to decrease operative time and approach-related morbidity compared to conventional both column plating. The aim of this biomechanical study was to evaluate whether single column plate plus other column lag screw fixation confers similar stability to both column plate fixation. Physiological loads were simulated using both the single-leg stance (SLS) as well as the sit-to-stand (STS) loading protocols. A clinically relevant ACPHT fracture model was created using fourth-generation composite hemipelves. Fractures were stabilized with three different fixation constructs: (1) anterior column plate plus posterior column screw fixation (AP+PCS), posterior column plate plus anterior column screw fixation (PP+ACS) and anterior column plate plus posterior column plate fixation (AP+PP). Specimens were loaded from 50 to 750N with a ramp of 100N/s. Fracture gap motion (FGM) and relative interfragmentary rotation (RIFR) between the three main fracture fragments were assessed under loads of 750N using an optical 3D measurement system. STS loading generally resulted in higher mean FGM and RIFR than STS loading in the AP+PCS and AP+PP groups, while no significant differences were found in the PP+ACS group. Compared to conventional both column plate fixation (AP+PP), PP+ACS displayed significantly higher FGM and RIFR between the iliac wing and the posterior column during SLS loading. No significant differences in FGM and RIFR were identified between the AP+PCS and the AP+PP group. Overall, single column plate plus other column lag screw fixation conferred similar stability to conventional both column plate fixation. From a clinical point of view, AP+PCS appears to be the most attractive alternative to conventional AP+PP for internal fixation of ACPHT fractures.

Experimental Comparison of Optical Inline 3D Measurement and Inspection Systems

Fast optical 3D inline inspection sensors are a powerful tool to advance factory automation. Many of these visual inspection tasks require high speeds, high resolutions, and repeatability. Stereo vision, photometric stereo, light sectioning, and structured light are the most common principles for inline imaging in the several micrometers to sub-millimeter resolution range. Selecting the correct sensor principle can be challenging as manufacturers’ datasheets frequently use different values to describe their systems and do not stick to proposed characterizations defined by the “Initiative Fair Data Sheet” or the VDE/VDI standards. With the help of standardized parameters, this paper aims to compare four different measurement principles, namely AIT’s own single sensor light field camera method, a structured light pattern projector, a laser triangulation sensor, and a stereo camera system, with an approximate field of view of $100\times 100$ mm. We demonstrate simple yet meaningful experiments to determine lateral resolution, temporal noise, and calibration accuracy to enable an objective system comparison. Additionally, the reproduction of small surface structures and an overall performance on a challenging test object is evaluated. Results show that the measurement principles partly serve different application areas. The provided methods will help end users to select the correct sensor for specific applications.

Evaluation of tensile strength of painted steel wi local corrosion at structural connections

Steel structures are often protected by paint coating, but the coating easily deteriorates at structural connections because moisture and dust accumulate at the contact. This leads to the local corrosion on the steel members near the contact and a reduction in tensile performance. The corrosion characteristics and tensile strength of steel plates with a concrete block are investigated. Four types of specimens were prepared, and each type had an unpainted area with different lengths away from the contact boundary. An accelerated cyclic corrosion test was conducted for 600 cycles using CCT-I test conditions specified in the ASTM D 6899–03 standard. To analyze the corrosion characteristics, the surface geometry of corroded specimens was measured in 1 mm × 1 mm intervals by an optical 3D measurement system. The average corrosion depth outside the concrete block was proportional to the unpainted area, and the average corrosion depth inside the concrete block was accelerated in unpainted areas. The two average corrosion depths have a power regression relationship, so the average corrosion depth inside the concrete block can be estimated from the average corrosion depth outside it. A simple method for quantitatively defining the residual thickness is proposed in terms of the effective thickness and the residual tensile strength, which can be evaluated using the effective thickness. Compared to previously proposed methods for this purpose, the effective thickness has higher accuracy.

Combining laser transformation hardening and ultrasonic impact strain hardening for enhanced wear resistance of AISI 1045 steel

A medium-carbon steel AISI 1045 was hardened by a laser heat treatment (LHT), a multi-pin ultrasonic impact treatment (UIT), and two combined laser-ultrasonic surface treatments (UIT + LHT and LHT + UIT processes) to improve the wear resistance of the surface layer. The paper is focused on detecting the relationship between the surface roughness and microstructure, phase state, hardness, residual stress of the specimens hardened by the LHT, UIT and combined UI + LHT/LHT + UIT processes, and their wear and friction behaviors. The hardened plane specimens were examined after the short-term (15 min) and long-term (45 min) wear tests under oil-lubricated conditions in the quasi-static and dynamic loads. The analysis of the surface morphologies and cross-section profiles of the worn tracks were assessed by an optical 3D measurement system and scanning electron microscopy (SEM). The wear mechanisms are also discussed. Results showed that the combined LHT + UIT treatment provides a lower surface roughness (Ra ~0.25 μm) and a highest surface hardness (~11,000 HV0.05) while the combined UIT + LHT treatment leads to the deeper hardened zone by 1.5–2 times. As compared to the untreated specimen (dynamic tests), the wear loss magnitudes were respectively decreased by ~5%, 35%, 42%, and 84% after the UIT, LHT, combined UIT + LHT and LHT + UIT processes. The LHT + UIT-processed specimen has the highest wear resistance owing to the formation of the fine-grained martensitic microstructure, more flattened surface microrelief, and the absence of the oxide film.

Biomechanical comparison of fixation techniques for transverse acetabular fractures – Single-leg stance vs. sit-to-stand loading

ObjectivesTo biomechanically compare five different fixation techniques for transverse acetabular fractures using both the single-leg stance (SLS) and the sit-to-stand (STS) loading protocols and to directly compare fracture gap motion (FGM) and relative interfragmentary rotation (RIFR). MethodsTranstectal transverse acetabular fractures were created on fourth-generation composite hemipelves in a reproducible manner. Five different fixation techniques were biomechanically assessed using both an SLS and STS loading protocol: anterior plate (AP) only, posterior plate (PP) only, anterior plate plus posterior column screw (AP+PCS), posterior plate plus anterior column screw (PP+ACS) and anterior plus posterior plate (AP+PP). After preconditioning, the specimens were loaded from 50 to 750 N with a ramp of 100 N/s. FGM and RIFR under loads of 750 N were measured using an optical 3D measurement system. ResultsIn the three groups of fixation techniques addressing both columns, STS loading resulted in higher mean FGM and in RIFR than SLS loading. No construct failure was observed. In the single plate groups (AP only and PP only), STS loading resulted in failure of all specimens before reaching loads of 750 N, while no failure occurred after SLS loading. No significant differences in FGM and RIFR were found between the double plate (AP+PP) and the single plate plus column screw (AP+PCS and PP+ACS) techniques. ConclusionSLS loading appeared to overestimate the strength of acetabular fracture fixation constructs and STS loading may be more appropriate to provide clinically relevant biomechanical data. Internal fixation of a single column might not provide adequate stability for transverse fractures, while strength of single plate plus column screw fixation and double plate fixation was comparable.

Impact of compression stockings on leg swelling after arthroscopy \u2013 a prospective randomised pilot study

BackgroundPost-operative limb swelling may negatively affect the outcome of arthroscopic surgery and prolong rehabilitation. The aim of this pilot study was to evaluate the effect of compression stockings versus no compression on post-operative swelling and pain in the early post-operative phase.MethodsA single-centre, randomised controlled trial was performed. Patients who underwent minor knee arthroscopy were randomised to wear class II compression stockings (23-32 mmHg) (CS) or no compression stockings (NCS) immediately post-operatively for ten days. All patients received low molecular weight heparin (LMWH) at prophylactic dosage. The primary outcome variable was post-operative swelling of the limb, quantified by using an optical 3D measurement system (Bodytronic© 600). Pain was rated on a visual analogue scale (VAS). From a total of 76 patients assessed, 19 patients were eligible for final analysis. The trial followed the CONSORT criteria, was registered at clinicaltrial.gov and approved by the local ethics committee.ResultsThe circumference at the middle thigh (cF) was significantly different between groups at day 10 (p = 0.032; circumference − 1.35 ± 2.15% (CS) and + 0.79 ± 3.71% (NCS)). Significant differences were also noted around the knee (cD) at day 10 (p = 0.026) and a significant trend at cD and at the mid lower leg (cB1) at day 4. The volume of the thigh was also different with marked difference between days 1 and 4 between the two groups (p = 0.021; volume + 0.54 ± 2.03% (CS) and + 4.17 ± 4.67 (NCS)). Pain was lower in compression group (not statistically significant).ConclusionsPost-operative limb swelling can be reduced significantly by wearing compression stockings in the early post-operative phase when compared to not wearing stockings. This may improve the rehabilitation process after arthroscopic surgery. The optimal duration of compression therapy seems to be between three and ten days.Trial registrationclinicaltrials.gov (NCT02096562, date of registration 11.11.2013).

Experimental evaluation of the tribological behaviour of CeO2 nanolubricants under extreme pressures

Lubrication of moving components is critical for lowering friction and reducing energy consumption. Nanoparticles have been recently studied as additives for improving the load-carrying capacity and overall tribological performance of lubricants employed for metal-mechanic applications. Cerium oxide is a lanthanide metal oxide (rare earth) with environmentally friendly characteristics that is widely used for consumer products, and most recently for enhancing the tribological performance of composite materials and lubricants. In this work, formulated polymeric lubricants employed for metal forming processes with dispersed cerium oxide (CeO2) nanoparticles were characterized under extreme pressure (EP) conditions. Nanoparticle concentrations of 0.01, 0.05, and 0.10 wt.% were dispersed by homogenization and ultrasonication in the selected lubricant. Tribological characterization under EP was performed with a T-02 four-ball tribometer according to the ITeE-PIB Polish method for testing lubricants under conditions of scuffing. This method applies and increasing load of 0-7200 N to the tribopair in a very short amount of time (18s) and is employed to find the maximum pressure a lubricant film can withstand. The scuffing load (Pt), and pressure loss limit or load carrying capacity (poz) were determined after each test. Wear scar diameters (WSDs) of worn ball materials were measured with an Alicona optical 3D measurement system. The anti-wear (AW) and friction-reducing characteristics of CeO2 nanolubricants were determined with a T-05 block-on-ring test. No seizure was found for all lubricants likely due to the presence of additives in the polymeric lubricant. Nanoparticles were found to delay scuffing initiation at concentrations up to 0.05 wt.%, and the load required for scuffing increased by 35 %. The load-carrying capacity was enhanced by up to 84% with only 0.01 wt.% CeO2. Higher concentrations (0.10 wt.%) had a detrimental effect, most likely due to nanoparticle agglomeration. The coefficient of friction (COF) was lowered from 0.035 for the polymeric lubricant to 0.006 with a concentration of 0.01 wt.% CeO2.The tribological results obtained by both tests demonstrate that CeO2 nanoparticles have friction-reducing and EP characteristics, making them suitable as lubricant additives in the metal-mechanic industry.

A Time-Dependent Corrosion Characteristic of a Steel Member in Contact with Concrete

Steel members in composite structures of steel and concrete, such as composite girder bridges, guardrails, and steel piers, are often partially embedded in concrete members. The corroded steel members in contact with concrete were recently fractured because of corrosion damage. This study investigates the time-dependent corrosion behavior of a steel plate in contact with concrete by performing an accelerated cyclic corrosion test, which was specified in the ASTM D 6899-03, on four types of composite model specimens of steel plates with different painted areas and concrete blocks for 100, 200, and 400 cycles. The surface geometry of the corroded steel plates was measured at a 1 × 1 mm interval using an optical 3D measurement system after the corrosion productions were removed. The corrosion characteristic, that is, the changes in the corrosion growth, corrosion depth, and the corrosion depth distribution with testing time, was statistically analyzed. The application procedure of the present test results to atmospheric environments was also proposed based on the amount of flying salt.

Characterizing 3D sensors using the 3D modulation transfer function

The fields of optical 3D measurement system applications are continuously expanding and becoming more and more diverse. To evaluate appropriate systems for various measurement tasks, comparable parameters are necessary, whereas the 3D modulation transfer function (3D-MTF) has been established as a further criterion. Its aim is the determination of the system response between the measurement of a straight, sharp-edged cube and its opposite ideal calculated one. Within the scope of this work simulations and practical investigations regarding the 3D-MTF’s influences and its main issues are specifically investigated. Therefore, different determined edge radii representing the high-frequency spectra lead to various decreasing 3D-MTF characteristics. Furthermore, rising sampling frequencies improve its maximum transfer value to a saturation point in dependence of the radius. To approve these results of previous simulations, three fringe projection scanners were selected to determine the diversity. As the best 3D-MTF characteristic, a saturated transfer value of has been identified at a sufficient sampling frequency, which is reached at four times the Nyquist limit. This high 3D resolution can mainly be achieved due to an improved camera projector interaction. Additionally, too small sampling ratios lead to uncertainties in the edge function determination, while higher ratios do not show major improvements. In conclusion, the 3D-MTF algorithm has thus been practically verified and its repeatability as well as its robustness have been confirmed.

Improving contour based pose estimation for fast 3D measurement of free form objects

Abstract This paper introduces new techniques for pose estimation of free form objects with an optical 3D measurement system. The approach of pose estimation based on contour features was extended by utilizing projected features, which allows to overcome estimation limitations due to the lack of features on free form objects. The principles of combining contour features with projected markers are explained and results comparing different sizes, geometries and densities of projected markers are provided.

Surface integrity analysis of abrasive water jet-cut surfaces of friction stir welded joints

Nowadays, the abrasive water jet (AWJ) technology is much in use for cutting materials into complex shapes with high dimensional accuracy. The objective of the present paper is to study the topography as well as the roughness of the surfaces in friction stir welded (FSW) joints, machined by AWJ. It discusses machinability of the FSW joints by AWJ. Subsequently, this paper makes a critical analysis of the surface properties by optical profilometer. Top and bottom surfaces, created by FSW, have also been analyzed using an optical 3D measurement system to determine the morphology and topographic parameters. FSW possesses favourable joining properties and generates a minimum heat-affected zone (HAZ) because of its comparatively low temperature coalescence. Three friction stir welding samples were prepared at 500, 710 and 1000 rpm with a welding speed of 40 mm/min on AA 6101-T6. After analysis, it was found that the sample prepared at 500 rpm and with welding speed of 40 mm/min produces a surface fit for industrial applications in terms of surface roughness and dimensional accuracy. It has also been observed that unlike other conventional or non-conventional processes, no HAZ is generated during the cutting of FSW joints by using the AWJ technology.

Metrological changes in the surface morphology of cereal grains in the mixing process

Abstract The paper presents a new idea of approach to the analysis of surface morphology of cereal grains. In this paper, the surfaces of maize were analyzed using an optical 3D measurement system to determine the surface morphology and parameters of surface topography. It was established how changes in the moisture influence on the surface characteristics. Comprehensive parametric analysis was conducted for maize grains with different moisture contents. The objective of this study was to comprehensively characterize the surface morphology of maize in contact area using standardized 3D roughness parameters as well as other characteristics such as structure direction and isotropy. This is the first study that has presented, elucidated, and discussed the relationships between some morphological parameters of cereal grains. This research contributes to better understanding of the mixing process. The main findings are: the values of roughness parameters kurtosis and skewness are characterized by higher values for maize grains with lower moisture, compared with maize grains with higher moisture content; there is a close relationship between the maize grain moisture content and the surface roughness parameters of kurtosis and skewness; maize grains have an anisotropic structure.

Metrological changes in surface morphology of high-strength steels in manufacturing processes

In this paper the surfaces of high-strength steels were analyzed using an optical 3D measurement system to investigate into the surface morphology and parameters of surface topography. Analyzed surfaces were generated by the most commonly used in the production facilities of manufacturing processes. The study was conducted for 400 HB plates. It was established that the behavioral changes in the manufacturing process influence the surface characteristics to a great extent. Comprehensive parametric analysis was conducted for dry production conditions. It has been observed that there exists a close correlation between mesh grit size and parameters of surface roughness Ssk and Sku in abrasive blasting processes. Furthermore the results show that the surface morphology in turning process depends to a large extent on the direction of feed motion. The study was performed within a production facility during the machining of components subject to wear.