Shallow Scratches Research Articles

Fracture properties of carbon/glass fiber composite laminates with surface scratch damage

Carbon/glass fiber reinforced polymer composite panels may experience minor surface scratches during processing or use. These shallow scratches can expand and potentially lead to dangerous fracture failure as the specimens are continually loaded. This study presents a closed form non-LEFM model for predicting the fracture performance of materials with slight scratches. First, 3-p-b tests and direct tensile tests were conducted on 115 carbon/glass fiber composite laminated panel specimens. A comparison of the two test methods revealed that 3-p-b tests were more suitable for analyzing quasi-brittle fracture in carbon/glass fiber composites. The tensile strength ft and fracture toughness KIC of 3-p-b specimens with and without notched were discussed using the weighted average calculation method to determine the thickness of the “composite” single-layer prepreg as the characteristic composite unit Cch. A normal distribution method was also introduced to analyze the experimental discrete points, covering almost all the experimental scatterers with desired reliability. Furthermore, the same method was applied to specimens with different layup methods, and the data analysis confirmed its effectiveness. As the seam-thickness ratio α increases within a certain range, the tensile strength ft showed an overall increasing trend and the peak load Pmax showed a decreasing trend. Additionally, the laboratory routine dimensions can be utilized to efficiently predict the fracture of large size members with defects at the same thickness, which is significant for the safe design of composite structures.

Quasi-brittle fracture criterion of CFRP with shallow surface scratch based on boundary effect model

This study investigates the quasi-brittle fracture parameters of carbon fiber composites with shallow surface scratches by considering single-layer prepreg thickness as the characteristic composite microstructure. Three-point bending fracture tests were conducted on single-edge notched specimens of various-sized carbon fiber composites. The boundary effect model was employed to establish the relationship between the microstructure and macroscopic mechanical characteristics of carbon fiber composites. The maximum fracture load was used to determine the quasi-brittle fracture characteristics. By employing normal distribution analysis, the tensile strength and fracture toughness of each specimens were determined asft = 453.28 MPa andKIC = 22.2 MPa √ m, respectively. The analysis results exhibited an error of only 0.39 % compared to the least-squares fit, and encompassed almost all discrete points of the specimens within a 95 % reliability range. Using standard laboratory dimensions, fracture intervals for different notched depths at the same thickness can be predicted. Furthermore, the fracture parameters demonstrated an increasing trend within a certain range as the crack-thickness ratio increases, which aligns with the theoretical findings.

Improving the Quality of Ceramic Products by Removing the Defective Surface Layer

The surface of ceramic products manufactured using diamond grinding is replete with shallow scratches, deep grooves and other defects. The thickness of the defective layer amounts to 3–4 µm and it must be removed to increase wear resistance of the products when exposed to intense thermomechanical loads. In this study, removal of the defective layers from samples made of ZrO2, Al2O3 and Si3N4 with a beam of fast argon atoms was carried out with a stripping rate of up to 5 µm/h. To prevent contamination of the source of fast argon atoms by the sputtered dielectric material, the beam was compressed and passed to the sample through a small hole in a wide screen. Due to the removal of the defective layer, abrasive wear decreased by an order of magnitude and the adhesion of coatings deposited on the cleaned ceramic surfaces improved significantly.

Effect of Er: YAG laser and plasma treatment on the bond strength of Y-TZP

ObjectivesThis study aimed to evaluate the effects of Er:YAG laser and plasma treatment on the bond strength between Y-TZP and resin cement. Materials and methodsSixty yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) specimens were fabricated and randomly assigned to six groups (n = 10): control group (group A); Sandblasting treatment (group B); Er:YAG laser group (group C); Ar plasma group (group D); Sandblasting + Ar plasma group (group E); and Er:YAG laser + Ar plasma group (group F). The surface of each zirconia specimen was tested using a contact angle meter, profilometer, and scanning electron microscope, and the shear bonding strength (SBS) was calculated. Statistical analysis was performed with One-way analysis of variance (ANOVA) combined with a least significant difference (LSD) test. ResultsThe surface morphology showed no difference between group A and group D, with smooth surfaces and shallow scratches after polishing. The surface roughness value of group C was 2.58 ± 0.14μm and was not significantly different from that of group F (P > 0.05), was higher than that of group A (P < 0.05). The SBS of group B was not significantly different from that of group D (P > 0.05). The hydrophilicity, carbon and oxygen contents, and SBS of group E were similar to those of group F (P > 0.05) and significantly higher than those of groups A, B, C, and D (P < 0.05). SignificanceThe Er:YAG laser and Ar plasma treatment can improve the bonding strength between zirconia and resin cement, and mechanical treatment followed by Ar plasma surface modification is more effective.

A measure of perceived quality to secure the polishability of new paint systems

The automotive industry continuously strives to reduce their environmental impact. For the paint shop it means to introduce more sustainable paint concepts, while maintaining the production rate and retain the right surface appearance that is crucial for the vehicle’s perceived quality. Today most painted parts are visually inspected and, if needed, manually repaired by abrasive polishing to eliminate spot defects. The repair process consists of one sanding step to remove the defect, and one or two rubbing/polishing steps to restore the surface, but still it tends to be a non-reliable process leaving patterns or clusters of shallow micro scratches seen as three-dimensional shapes moving over the surface when viewed from different angles like holograms. These so called ‘polishing roses’ are hard to detect in artificial light but clearly visible in Sunlight and therefore they constitute a constant quality issue. Accurate polishing procedures in combination with more objective inspection techniques would secure a high surface quality—but what is ‘accurate’? The overall scope of the study was to deepen the knowledge of paint systems to develop test routines for the polishability of coatings already during the development stage, and thereby ease the implementation of new coating systems in production. The study was based on collected process data from professional polishers to define a process window based on key parameters for successful end-of-line repairs of coated surfaces, i.e. strategies minimizing the occurrence of visible polishing traces. A CNC-machine was built up for the purpose to systematically test and evaluate new coating systems and repair procedures. The surface estimation was made by visual inspections as well as by a further developed photometric stereo system providing quantitative images of remaining repair traces.

Preparation and Characterization of Pulse Electrodeposited Ni/W-SiC Nanocomposite Coating on Mild Steel Substrate

In order to improve the performances of metal containers, furnace bodies and agricultural tools manufactured by mild steels, Ni/W-SiC nanocomposites are prefabricated on mild steel substrate by the pulse electrodeposition (PED) method. The morphology, texture, microstructure, microhardness, and wear performances of Ni/W-SiC nanocomposites are examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), dispersive X-ray spectroscopy (EDX), hardness tester, and friction wear testing. The results indicate that the SiC size in nanocomposites is ~32.4 nm when its concentration in electrolytes is 7 g/L. The S1 and S4 nanocomposites’ microstructures (the S1 composite was prefabricated at 4 g/L, and the S4 composite was deposited at 13 g/L) reveal many large cauliflower-shaped grains. However, the S2 nanocomposite (the S2 composite was obtained at 7 g/L) demonstrates the homogeneous, finest and smoothest surface morphology. The diffraction angles of S1 nanocomposite are 41.2°, 51.7°, and 71.2° depicting the sharpest diffraction peaks, corresponding to the (1 1 1), (2 0 0), and (2 2 0) crystal planes of Ni-W grains, respectively. Moreover, the S2 nanocomposite exhibits the lowest wear depth and width of 34.2 μm and 5.5 mm, respectively. Some shallow and fine scratches on the as-described nanocomposites’ surface indicate its excellent tribological performance. However, the S4 nanocomposite exhibits a wear depth of 86.3 μm and a width of 11.9 mm.

Microstructures and performances of Ni-SiC coatings manufactured by laser cladding deposition

45# steel substrates were coated with Ni-SiC by using the laser cladding deposition (LCD) method in this article. X-ray diffractometer (XRD), scanning electron microscope (SEM), micro-hardness meter, wear/friction tester and electrochemical workstation were used to examine the surface morphology, microhardness, wear and corrosion performances, and phase structure of the Ni-SiC coatings. The results indicated that the structures of Ni-10SiC and Ni-30SiC coatings were columnar dendrites and equiaxed crystals (finer in Ni-30SiC coating). The Ni-10SiC and Ni-30SiC coatings were passed through initial and stable wear stages. The average micro-hardness values of Ni-30SiC and Ni-10SiC coatings were separately about 851.3 HV and 748.4 HV. Results showed that the Ni-10SiC and Ni-30SiC coatings suffered stable and initial wear phases. Several big grooves and spalling pits were noted on the sported surface of the Ni coating. While shallow scratches were observed on the wear surface of Ni-30SiC coating. In addition, the Ni-30SiC coating had the lowest corrosion current density (6.325 ×10−6 A/cm2), demonstrating the most efficient corrosion resistance among all three coatings.

Effectiveness of Different Polishing Kits for Chairside CAD/CAM Provisional Restorative Materials.

To investigate the efficacy of three specially designed polishing kits for provisional restorations made from three chairside computer-aided design and computer-aided manufacturing (CAD/CAM) provisional resin blocks. Ninety-six chairside CAD/CAM provisional restorations were milled out of three chairside CAD/CAM provisional resin blocks: (1) ArtBloc Temp (Merz Dental); (2) Telio CAD (Ivoclar Vivadent); and (3) Vita CAD-Temp (VITA Zahnfabrik). The provisional restorations for each material were allocated into the following groups: (1) milled restorations (no polish); (2) polished with CADMaster CAD/CAM Adjustment & Polishing Kit (CM, Shofu); (3) polished with KUT Ultimate Bisacryl (Temporaries) Polishing Kit (KU, Dental Savings Club); and (4) polished with K0330 PMMA Adjusting, Finishing & Polishing (KP, Brasseler USA). Optical profilometry and atomic force microscopy (AFM) were used to assess the surface roughness (Ra) of each provisional restoration at the microscale and nanoscale, respectively, and obtain topographical images. In addition, the milled and polished restorations were visually evaluated by 16 dentists. There was a strong positive correlation with Ra values between optical profilometry and AFM. Only KP significantly improved the surface roughness of CAD/CAM provisional restorations compared to the milled equivalent, regardless of material type or measurement modality (ie, lateral length scale). Although surface topography imaging with AFM revealed some shallow scratches, even for KP polished specimens, all KP polished restorations were categorized as clinically acceptable for provisional restorations in visual inspections from dentists. Specially designed polishing kits for provisional restorations did not all improve the surface roughness of chairside CAD/CAM provisional restorations, regardless of the measurement method. KP was more consistently effective in polishing milled chairside CAD/CAM provisional restorations than CM and KU.

Morphological characteristics and formation mechanism of latent scratches in chemical mechanical polishing

Latent scratches are extremely shallow scratches inevitably introduced during chemical mechanical polishing (CMP), which deteriorates the performance of functional crystals. Although latent scratches can currently be detected by some advanced microscopes, there is still a lack of in-depth understanding of them. In this paper, we describe the morphological characteristics of latent scratches using atomic force microscopy and develop a mathematical model to explain the formation mechanism of latent scratches with YAG crystals as an example. The observations showed that the distributions of the depth and width of latent scratches were always Gaussian-like. And the pressure was positively correlated with the number of latent scratches but did not significantly affect the depth and width. The proposed mathematical model describes the contact state between the particles and the crystal surface, and identifies the formation of latent scratches resulting from plastic deformation of the crystal surface, a conclusion further supported by transmission electron microscopy observations. The model also explains that the distribution of depth and width is mainly determined by the material properties and that pressure affects the number of particles in contact with the workpiece but does not significantly change the contact stress between individual particles and the workpiece. There is an upper limit to the contact stress, resulting in scratches always below 1 nm in depth. The analysis of latent scratches is of great significance to removing latent scratches and manufacturing the ultra-smooth surface in the CMP process.

Prefabrication of two-dimensional Ni–W/TiN films on oil-gas X52 steels by pulse electrodeposition

The main aim of this investigation was to prefabricate two-dimensional Ni–W/TiN films on oil-gas X52 steel substrates via pulse electrodeposition (PE). The influences of the TiN content in the bath on the surface morphology, nano-hardness, wear, and corrosion properties of the films were also discussed. The results indicated that the TiN particle size was only ∼33 nm in 8 g/L TiN electrolyte, which was ∼2.4 times less than that of TiN in 16 g/L solution. The Ni–W/8TiN film exhibited a uniform, smooth surface, and the depression depth and protrusion height were 45.3 nm and 81.7 nm, respectively. Three diffraction peaks at 43.72, 50.78, and 75.26° in the Ni–W/4TiN film emerged as the sharpest and narrowest peaks among the four films. Three XPS peaks for the Ni 2p3/2 were present at 852.13, 856.35, and 861.87 eV in the Ni–W/8TiN film, corresponding to Ni, Ni2+ (Ni(OH)2), Ni3+ (NiOOH) species. Besides, the XPS peak of W 4f7/2, which located at 33.85 eV belonged to elemental W. The Ni–W/8TiN film had the lowest wear depth and width at 32.1 μm and 5.7 mm, respectively. Only some narrow and shallow scratches were found on the Ni–W/8TiN film surface, showing its outstanding tribological properties among the films tested. In addition, the Ni–W/4TiN film showed the highest mean frictional coefficient of 0.73, which was ∼1.6 times more than that of the Ni–W/8TiN film.

Microstructures and properties of nickel-titanium carbide composites fabricated by laser cladding

In this work, Ni/TiC composites were synthesized by the laser cladding technique (LCT). A scanning electron microscope (SEM), X-ray diffractometer (XRD), microhardness meter, electrochemical workstation, and friction and wear tester examined the microstructure, surface morphology, phase structure, microhardness, wear, and corrosion resistances of the Ni/TiC composites. These results indicated the Ni/40TiC composite contained finer equiaxed crystals than the Ni and Ni/20TiC composites. In addition, numerous TiC particles in the Ni/40TiC composite impeded growth of the nickel crystals, which resulted in the fine microstructure of the Ni/40TiC composite. The Ni, Ni/20TiC, and Ni/40TiC composites exhibited face-centered cubic (f c c) lattices. The average microhardness values of the Ni/20TiC and Ni/40TiC composites were approximately 748 HV and 851 HV, respectively. The Ni/40TiC composite had the lowest friction coefficient (0.43) among all three coatings, and only some shallow scratches appeared on the surface of the Ni/40TiC composite. The corrosion potential (E) of Ni/40TiC exceeded the Ni/20TiC composite, and both were larger than the Ni composite, which indicated the Ni/40TiC composite had outstanding corrosion resistance and the Ni composite had poor corrosion resistance. The corrosion current densities (i) of Ni, Ni/20TiC, and Ni/40TiC composites were 5.912, 4.405, and 3.248 μA/cm2, respectively.

Detection method for surface scratches of composite automotive components with high reflection and complicated background color

Abstract Current testing status have the problems that the surface background color pattern of high reflective carbon fiber auto parts is complex, the shape of scratch defects is irregular, and the shallow and micro scratches are not easy to be detected. Aiming at the problems, a scratch detection method combining innovative morphological processing and optimized Canny edge detection algorithm is proposed. The image acquired by an innovative image acquisition platform. After gray processing and open operation denoising, the self-defined oval kernel secondary expansion is introduced in the morphological processing part. When threshold segmentation and minimum connected domain screening are done, the optimized Canny edge detection algorithm is used. Through the non-maximum suppression of gradient amplitude, a wide range of dual-threshold parameters are selected to detect the edge of the target image. The results show that the detection rate of the proposed method is 18.57% higher than that of the traditional way, and the detection rate is up to 95.71%. At the same time, the proposed method can reflect the scratch morphology more intuitively.

Effect of TiN concentration on microstructure and properties of Ni/W–TiN composites obtained by pulse current electrodeposition

In this study, Ni/W–TiN composites were fabricated by the pulse current electrodeposition (PCE) method. The effects of TiN concentration on the microstructure, microhardness, and wear properties of the resulting composites were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), microhardness tester, and friction wear testing. Among the four obtained composites, Ni/W–TiN composite prepared at 8 g/L showed the densest and finest surface structure. The TiN contents in obtained Ni/W–TiN composites at 8 and 16 g/L were estimated to 8.1 and 5.4 wt%, respectively. The average Ni/W grain diameter in Ni/W–TiN composite obtained at 8 g/L TiN was recorded as 84.7 nm. The protrusion and depression heights of the composite deposited at 8 g/L were 81.8 and 45.4 nm, respectively. This composite also processed an average microhardness of 897.6 HV, with only a few shallow and narrow scratches on its worn surface, demonstrating its prominent wear resistance when compared to the other three composites.

Evaluation of fractured–vuggy reservoir by electrical imaging logging based on a de-noising method

The existence of fractures and vugs in igneous formation is a key factor to determine the productivity of oil and gas reservoirs. Fracture–vug plane porosity and porosity spectrum (fracture–vug parameters) are important parameters to evaluate the development of fractures and vugs. In the process of drilling, the bit forms shallow holes and scratches on the borehole wall which is characterized by pitting, strip and block noise in the electrical imaging logging static image. The background noise affects the identification of fractures and vugs and the extraction of parameters. It is found that the background noise mainly exists in the high-frequency conductivity data. In order to suppress the background noise, empirical mode decomposition is applied to conductivity data of electrical imaging logging, and the wavelet hard threshold de-noising is applied to high-frequency intrinsic mode function components. The de-noising fracture–vug parameters have a good correspondence with the electrical imaging logging static image, and have a better linear relationship with the core porosity. These illustrate that the application of the de-noising method in the electrical imaging logging is reasonable and effective. The de-noising porosity spectrum becomes narrower in the reservoir with poor fractures and vugs, which can reveal the development of secondary pores more clearly. In reservoir interpretation, the de-noising fracture–vug plane porosity and porosity spectrum have good consistency with conventional and acoustic logging data, which can effectively evaluate the fractures and vugs in reservoirs.

Effect of Calcium Carbonate Particle Size on the Scratch Resistance of Rapid Alkyd-Based Wood Coatings

Polymer-based wood coatings are used for aesthetic purposes as well as to protect wood surfaces, especially under external conditions. High-hardness mineral fillers are thought to enhance the resistance of these polymer coatings to wear and scratching. However, recent studies suggest that the relatively low-hardness mineral calcite (CaCO3, Mohs hardness of 3) performs similarly to harder minerals under external conditions. It can replace more expensive hard minerals, thus driving research interest in its use. In this study, CaCO3 powders with different grain sizes were applied to rapid alkyd-based coating formulations, and the effect of CaCO3 particle size on the scratch behavior of the coatings was investigated under identical test conditions. The scratch morphologies, scratch hardness, and roughness values of the scratched surfaces indicated that the surfaces of the rapid alkyd-based wood coatings including finer-grained CaCO3 experienced plastic plowing-type deformation in the form of regular, narrow, and shallow scratches, showing high scratch resistance. Coatings using coarser-grained CaCO3 experienced more extensive plastic deformation of the plowing–tearing type owing to the weaker filler–polymer interface and the breakage of larger coating pieces from the coating surface.

A simple closed-form model for fracture of CFRP panel with shallow surface scratch confirmed by comprehensive flexural/tensile tests

Comprehensive tests using more than 200 CFRP laminate specimens with and without shallow surface scratches (20 μm - 3 mm) have been performed under three-point-bending (3-p-b) and direct tensile conditions. Critical flexural loads of scratched 3-p-b specimens have been linked to the tensile strength ft of CFRPs by a simple closed-form solution of a non-Linear Elastic Fracture Mechanics (non-LEFM) model for composite failures, which models the crack tip damage using the characteristic composite microstructure Cch (ply thickness of CFRP). The average ft measured from 30 direct tensile tests is virtually identical to that from 170 different 3-p-b tests with only 2% relative error, indicating potential applications of the simple closed-form solution in structural integrity analysis for scratched CFRP components. The statistical reliability has been combined into the predictive model, which can be important when not only the mean strength but also the prediction interval is required.

EFFECT OF DIFFERENT SURFACE TREATMENTS ON BONDING OF ULTRA- TRANSLUCENT ZIRCONIA

Introduction: Introduction of ultra-translucent zirconia led to increase its indications for minimally invasive aesthetic restorations, therefore, it is important to test its adhesive potentiality. Objectives: Investigation of shear bond strength (SBS) of ultra-translucent zirconia to enamel after different surface treatments and examination of their effect on surface topography. Materials and methods: Thirty six ultra-translucent zirconia discs, (O5mm×3mm height) were divided into three groups (n=12): Control (C): as-sintered discs, Sandblasted discs (SB): discs were sandblasted by 110μm Al2O3 particles for 10 seconds, at 2.5 bar pressure, from 10mm distance, and Etched discs (ZE): discs were dipped into Zircos-E etching solution (BIO DEN CO, Korea) for thirty minutes in an ultrasonic cleaner. The surface topography of two randomly selected discs from each group were examined by scanning electron microscopy (SEM) for descriptive analysis, and the remaining discs were bonded to enamel surfaces of human central incisors for performing the SBS test. Statistical analysis of SBS results was done by Kruskal Wallis test and post hoc test with statistically significant results at (p < 0.05). Results: Morphological examination of (C) showed closely connected grains, (SB) showed a number of superficial irregularities, and shallow scratches, whereas (ZE) showed gross discontinuity of grain structure. The highest SBS value was recorded by (SB) (19.01±2.00 MPa) with insignificant difference from (ZE) (16.73± 2.13 MPa), and significant difference from (C) with the lowest SBS value (8.69±1.95 MPa). Conclusions: Etching of ultra-translucent zirconia using (Zircos-E) is a promising technique for improvement of resin bonding in comparison to control and sandblasted groups.

Critical bending load of CFRP panel with shallow surface scratch determined by a tensile strength model

Carbon fibre reinforced polymer (CFRP) composite structures may experience light surface damage such as shallow surface scratch around 50 μm or less in applications. In this study, critical bending loads of 2D woven CFRP panels with and without shallow surface scratches were assessed under three-point-bending (3-p-b) conditions and then modelled by a simple strength theory for composite fracture. This closed-form tensile strength solution is a non- Linear Elastic Fracture Mechanics (LEFM) model derived specifically for heterogeneous composites. Direct tensile tests of the CFRP panels (without shallow surface scratch) were also performed, and measured tensile strength was compared with that from 3-p-b tests. The relative error between the two different tests was only around 6.7%. The ply thickness around 140 μm was selected as the controlling composite microstructure parameter or characteristic composite unit Cch in this non-LEFM model. This simple model shows that a suitable composite characteristic microstructure measurement such as Cch = ply thickness can significantly simplify composite fracture analysis. A simple statistical analysis using a 2D normal distribution methodology for strength measurements was also introduced so that the experimental scatters can be analysed. The 95% reliability band can be conveniently used in safe design of composite structures.

Friction and wear behavior of carbon fiber reinforced lithium aluminosilicate composites sliding against GCr15 steel

Carbon fibers reinforced lithium aluminosilicate matrix composites (Cf/LAS) were prepared by slurry infiltration combined with a hot press procedure. The friction, wear behavior, and wear mechanisms of Cf/LAS composites under dry sliding conditions were investigated. The results show that the coefficient of friction (COF) initially increased with the increase in carbon fiber content, and reached the maximum value of 0.20 for the 33%Cf/LAS composite. The COF increased sharply with increasing sample temperature from RT to 300 °C. The COF remained stable in the temperature range of 300–500 °C. The two wear mechanisms of LAS glassceramics are fatigue wear and abrasive wear. The Cf/LAS composites demonstrate slight spalling and shallow scratches. These results show that carbon fibers improve the mechanical properties and wear resistance of Cf/LAS composites.

Concentric Mutual Lapping to Improve Sliding Surface Function of SiC Ceramics

Ring-shaped SiC ceramics used in sliding components were examined herein. Conventional lapping generates many shallow scratches in random directions in the surface of such SiC ceramics, and these starches extend from the inner circumference of the surface to its perimeter. The scratches affect the ability of the surface to prevent liquid from escaping from the perimeter side to the inner-circumference side of the SiC ring, and they can increase the friction force of the finished surface as a sliding material. We propose concentric mutual lapping to remove the scratches caused by conventional lapping. The surface topography of a SiC ring is evaluated quantitatively using a white light interferometer, and a vector and quantitative analysis of the surface profile is proposed. The results show that concentric mutual lapping can quickly remove the scratches caused by conventional lapping, and subsequently, circumferential scratches are generated along the lapping direction. We have also conducted sliding tests to analyze the effect of surface topography on the surface function as a sliding material. The results reveal that concentric mutual lapping suppresses the differences in surface function that occurred depending on the sliding direction.