Surface Roughness Rz Research Articles

Effect of different surface treatments on shear bond strength of zirconia with various yttria contents

BackgroundAchieving a stable bond with zirconia requires mechanical and chemical bonding methods. Information regarding the optimal treatment method for zirconia with varying yttrium content is scarce. This study evaluated the effect of different surface treatments on the shear bond strength of zirconia with various yttria contents.Materials and methodsA total of 168 disc-shaped zirconia specimens were classified into 12 groups based on the surface treatment method, including airborne-particle abrasion (APA), selective infiltration etching (SIE), hot etching (HE), and control group with no treatment; and yttria contents including Zolid Zi (4.5–5.6 wt% yttrium), Zolid HT White (6.7–7.2 wt% yttrium), and Ceramill Zolid FX (9.15–9.55 wt% yttrium). The surface roughness (Ra and Rz) of the specimens and the shear bond strength was measured (α = 0.05).ResultsThe results indicated that the mean bond strength of all specimens was higher after different surface treatments compared to the control group, of which the APA method resulted in higher bonding strength in all kinds of zirconia than other methods (P < 0.05). In all types of zirconia, a significant difference was observed in surface roughness (Ra and Rz) resulting from various surface treatment methods (P < 0.001). Interaction of surface treatment methods and zirconia type significantly affected shear bond strength and surface roughness (P < 0.05).ConclusionAPA significantly enhanced shear bond strength and surface roughness across all zirconia types and yttria contents. The SIE and HE methods also showed promising results. Zolid Zi showed superior bond strength, whereas Zolid FX demonstrated reduced bond strength.

Effect of Dual Shot Peening on Microstructure and Wear Performance of CNT/Al-Cu-Mg Composites.

This work systematically investigated the effect of dual shot peening (DSP) and conventional shot peening (CSP) on the microstructure, residual stress and wear performance of the CNT/Al-Cu-Mg composites. The results indicated that compared with CSP, DSP effectively reduced surface roughness (Rz) from 31.30 to 12.04 μm. In parallel, DSP introduced a smaller domain size (33.1 nm) and more dislocations, higher levels compressive residual stress and a stiffer deformation layer with deeper affected zones. Moreover, DSP effectively improved the uniformity of the surface layer's microstructure and residual stress distribution. The improvement is mainly due to secondary impact deformation by microshots and fine grain strengthening. In addition, the transformation of the hard second phases such as Al4C3 and CNT and its effects on improving the surface strength and deformation uniformity were discussed. Significantly, DSP improved the wear resistance by 31.8% under the load of 6 N, which is attributed to the synergistic influence of factors including hardness, compressive residual stress, surface roughness, and grain size. In summary, it can be concluded that DSP is an effective strategy to promote the surface layer characteristics for CNT/Al-Cu-Mg composites.

An assessment of PLA/wood with PLA core sandwich multilayer component tensile strength under different 3D printing conditions

Material extrusion is increasingly used to make functional parts in small batches that are challenging to produce with traditional machining. Also, intensive efforts are being made to develop new eco–friendly materials. This work investigates the strength of multilayer samples made in sandwich form with 4–5–4 layers of 0.3 mm layer thickness, externally with polylacticacid wood (PLA/wood, 61.5 % of specimens' material) and internally with pure PLA (38.5 % of specimens' material), under tensile loads. The intent is to investigate the possibility of manufacturing biocompatible components that take advantage of the excellent surface properties of wood externally and the durability properties of PLA internally. For this purpose, a designed experiment following the Taguchi L9 orthogonal array was prepared, and nine samples were fabricated: three with pure PLA, three with a sandwich PLA/wood–PLA–PLA/wood form, and three with composite PLA/wood form. Printing speed and temperature were varied during the experiment, and the results were examined using the analysis of means and residuals. Sandwich specimens improve tensile strength and elastic modulus by 100 % and 50 % compared to PLA/wood components while exhibiting slightly better surface roughness parameters, i.e., Ra and Rz, about ∼10 % lower values. Additionally, even if PLA parts showed better strength and surface texture than sandwich parts (∼100 % and ∼56 % higher tensile strength and elastic modulus), they had lower performance in terms of PLA–PLA/wood material ratio, i.e., 160 % more PLA than sandwich parts. The findings of this research, with the potential to design functional and sustainable new products with optimal performance, are significant and can be exploited in various industries.

In Vitro Comparison of Titanium Disc Surface Roughness and Bacterial Colonization After Ultrasonic Instrumentation With Three Different Tips.

During implant maintenance, preserving a smooth surface on the machined transmucosal abutment is critical to reduce biofilm attachment and colonization. The present study compared the surface roughness and bacterial colonization of machined titanium surfaces after instrumentation with various materials. Forty-four machined grade 23 titanium discs were instrumented with a round polyether ether ketone (PEEK) tip, a plastic curette tip, or a pure titanium curette tip with piezoelectric devices. Before and after instrumentation, the surface roughness (Ra and Rz) values were analyzed with a profilometer and scanning electron microscopy (SEM). Streptococcus sanguinis was cultured and incubated for 24 hours on the instrumented discs, and colony-forming units per milliliter were obtained for each group. Samples instrumented with the metal ultrasonic tip significantly increased surface roughness compared with the other groups. This resulted in greater colonization by S. sanguinis than surfaces instrumented with PEEK tips or the negative control. Samples instrumented with PEEK and plastic tips did not exhibit any statistically significant increase in surface roughness, and SEM analysis revealed a significantly rougher surface of discs instrumented with metal compared with discs instrumented with plastic or PEEK tips despite the possibility of debris from tip dissolution. Our results suggest that instrumentation with metal ultrasonic tips with piezoelectric devices significantly increased machined titanium's surface roughness and elicited higher biofilm formation in vitro. Meanwhile, instrumentation of machined titanium with PEEK or plastic ultrasonic tips did not affect the surface roughness or bacterial adhesion.

Investigation of Nano Cutting Oil Effects on Hard Milling Under Minimum Quantity Lubrication

The presented work aims to investigate minimum quantity lubrication (MQL) using cutting oil with/without Al2O3 nanoparticles for hard milling of 60Si2Mn steel (50-52 HRC) using carbide inserts. The effects of three different types of based cutting oils including emulsion, soybean oil and rapeseed oil on surface roughness Ra, Rz and tool life were studied and investigated. The experimental results show that the use of Al2O3 nano cutting oil has improved lubrication capability compared to base cutting oil, contributing to improve machined surface quality and tool life. Al2O3 emulsion-based nanofluid exhibited the best performance among the three surveyed oils, followed by rapeseed oil and finally soybean oil. Furthermore, the cutting speed of the carbide inserts was improved and the tool life was significantly increased with the help of nano cutting oil due to the improvement in lubrication effects in the cutting zone, thereby helping to reduce cutting forces and cutting heat.

Experimental Study on Surface Residual Stress and Surface Roughness of Inconel718 Cutting

Abstract This thesis focused on the experimental study of surface residual stress and surface roughness of Inconel718 for cutting processing. Based on cutting theory, the cutting parameters’ effects on surface residual stress and roughness were analyzed through single-factor cutting experiments. The experimental results showed that: in the experimental parameters under constant conditions, Inconel718 processing surface residual stress with a rise in cutting speed in gradual decrease, with a rise in feeding speed and cutting depth in gradual increase; processing surface roughness Ra and Rz value with a rise in cutting speed in gradual decrease, with a rise in feeding speed and cutting depth in gradual increase. Consequently, the experimental results for Inconel718 cutting and processing technology provide a process basis.

Experimental Study on Dry Milling of Stir-Casted and Heat-Treated Mg-Gd-Y-Er Alloy Using TOPSIS

This study examines the dry milling process of a rare-earth-based magnesium alloy, emphasizing the optimization of the milling parameters and their impact on the surface quality, cutting forces, and the rate of material removal. The objective is to improve our comprehension of the milling behavior of the Mg-Gd-Y-Er alloy. The Taguchi technique is adopted to formulate the experimental design. This study methodically investigates the influence of heat treatment (T4 and T6) on milling performance, and the effects of speed, feed rate, and depth of cut. The output variables considered for this investigation are the surface roughness (Ra, Rz, Sa, and Sz), material removal rate (MRR), and cutting force. To optimize the milling parameters and achieve superior outcomes, the multi-objective optimization technique TOPSIS is used. At a feed rate of 150 mm/min, a spindle speed of 1500 rpm, and a depth of cut of 1 mm, the T4-treated sample exhibits a minimum surface roughness value of 0.0305 µm. The highest resultant force values of 96.4416 N and 176.1070 N for 200 °C and 225 °C T6-treated alloys are obtained by combining process parameters such as a spindle speed of 1500 rpm, a feed rate of 50 mm/min, and a depth of cut of 1.5 mm. Furthermore, the maximum closeness coefficient value is achieved by combining a spindle speed of 1000 to 1500 rpm, a feed rate of 150 mm/min, and a depth of cut of 0.5 mm to 1 mm. The closeness coefficient value is significantly influenced by the most significant process parameters, as indicated by the ANOVA results.

Prediction of surface roughness at the machining of densified wood surfaces

ABSTRACT In this research, modeling and interpretation of the effects of the machining parameters on surface roughness (Rz) using artificial neural networks (ANN) and analysis methods (MLP, LVQ and Taguchi Design analysis) werw studied. Black poplar (Populus nigra) was selected as the experimental material. Specimens, which were transversal densified by a thermo-mechanical (TM) process at 0%, 20% and 40% compression ratios. The densified wood was processed at 1000, 1500 and 2000 mm/min feed speeds and in 12,000, 15,000, and 18,000 rpm rotation speeds in a CNC machine by using two different cutters. Rz surface-roughness values were measured. The modeling of Rz with artificial neural networks (ANN) is discussed. While 97% success was achieved in the classification made with multilayer perceptron (MLP) in estimating Rz, this success rate is 100% in the classification made with learning vector quantization (LVQ). MLP and LVQ are operations in the MATLAB R2019b software. Taguchi values were compared with the experimental data results, it was seen that the MSE value was 4.6%, the MAE value was 1.8%, and the RMSE value was 2.1%. These results showed that the presented models can accurately determine the appropriate parameters for the desired Rz. The prediction results and presented models can be applied for targeted industrial applications.

Meso-level surface modification of Hastelloy C276 by WS2 powder mixed electrical discharge alloying process through micro-EDM setup

The present research provides a rigid, wear-resistant lubricating localized layer on Hastelloy C276 (HC 276) surface at meso level by tungsten disulphide (WS2) powder suspended electrical discharge alloying (EDA) process through micro-electrical discharge machining (μ-EDM) setup. The performance characteristics of the coated surface were evaluated in terms of material deposition rate (MDR), surface morphology, surface roughness (Ra, Rz and Rq), recast layer thickness (RLT), compositional analysis, micro-hardness & indentation depth, wear test and water contact angle analysis. Maximum MDR has been achieved at 15 g/L WS2 concentration and 80 V of gap voltage whereas The RLT varies from 6.87 μm to 18.91 μm and is enhanced with the increase in WS2 concentration. The critical surface characterization confirms higher WS2 concentration reduces the crater dimensions and the presence of micro-cracks and micro-voids on the coated surface. The surface roughness has been increased with the gap voltage and capacitance, whereas higher WS2 concentration provides lower surface roughness. X-Ray diffraction analysis (XRD) confirms the presence of hard and wear resistance phases like WC, WO3, ZnO, and MoO2 on the coated surface. Energy-Dispersive X-Ray Spectroscopy (EDS) analysis along with elemental mapping justifies tool, dielectric materials, and powder particles migration on the coated surface. The micro-hardness of the coated surface (402 HV to 1166 HV) is enhanced by 3–4 times compared to the base material (299 HV) whereas the indentation depth has been reduced with the rise in WS2 concentration and lies within the RLT of the coated surface. The wear rate of the WS2 coated surface is drastically reduced compared to the base material with a lower value of coefficient of friction (COF). The coated surface became hydrophobic in nature with a contact angle of 109.6° compared to the hydrophilic base HC 276.

Analysis of the Surface Roughness of Different Denture Teeth Materials: A Quantitative In-Vitro Study.

The surface roughness of denture teeth materials significantly influences their clinical performance and patient satisfaction. Understanding the variations in surface roughness among different materials is crucial for optimizing denture fabrication processes. In this quantitative in-vitro study, three commonly used denture teeth materials, namely acrylic resin, composite resin, and porcelain, were evaluated for surface roughness. Twenty samples of each material were prepared and subjected to profilometric analysis. The surface roughness parameters Ra and Rz were measured using a contact profilometer. Statistical analysis was performed to compare the surface roughness among the different materials. The mean surface roughness (Ra) values were found to be 0.32 μm for acrylic resin, 0.25 μm for composite resin, and 0.18 μm for porcelain. Similarly, the mean Rz values were 2.45 μm for acrylic resin, 1.98 μm for composite resin, and 1.62 μm for porcelain. Statistical analysis revealed significant differences in surface roughness among the three materials (P < 0.05). Porcelain denture teeth exhibited the smoothest surface, followed by composite resin and acrylic resin. These findings suggest that material selection plays a crucial role in determining the surface roughness of denture teeth. Porcelain may offer superior aesthetics and reduced plaque accumulation compared with acrylic and composite resin materials. Clinicians should consider these differences when choosing denture materials to achieve optimal clinical outcomes and patient satisfaction.

An Experimental Study on Hard Turning Performance of DIN 17350 Tool Steel

The main objective is to investigate the effects of cutting speed, feed rate and depth of cut on surface roughness Rz in hard turning process of DIN 17350-tool steel (60÷62HRC) under dry condition. The full factorial experimental planning design with the help of Minitab 19 software was applied to evaluate the main effects and interaction effects of input machining parameters. The experimental results indicate that feed rate and depth of cut cause the stronger impact on the objective function Rz than cutting speed. In addition, the interaction effects of cutting speed and feed rate as well as the cutting speed and depth of cut have significant influences on the output, but the interaction effect between the feed rate and depth of cut has little impact. Furthermore, cutting speed of 1400 rpm, feed rate of 0.05 mm/rev, and cutting depth of 0.1 mm should be recommended for the smaller surface roughness Rz values.

Advanced Support Structures in Metal Additive Manufacturing: A Comparative Analysis of Porous Media for Enhanced Part Quality and Removal Efficiency

In laser powder bed fusion additive manufacturing support, structures are crucial for constructing overhang features and maintaining dimensional accuracy. However, traditional support structures exhibit inherent drawbacks, including compromised surface quality, prolonged post‐processing times, and other challenging requirements. This study investigates innovative approaches to address these issues by analyzing two types of specimens—cuboid and lap shear. The cuboid samples explore the manipulation of process parameters to adjust energy densities, transitioning from powder to porous support structures, with porosity measurement assessment. Subsequently, a shear test specimen objectively evaluates porous support parameters alongside traditional block‐type support, analyzing their impact on removal force, distortion, and surface quality. Results reveal that optimized porous support structures surpass traditional counterparts, showcasing superior surface quality, reduced removal forces, and minimized part distortion. Specifically, the shear test demonstrates a 94.25% reduction in removal forces and a 33.67% decrease in upper part distortion. Moreover, the maximum surface roughness (Rz) improves by 22.8% with the implementation of porous supports. By introducing a methodology for comparative analyses of measurable performance indicators, this research enhances understanding of support structure dynamics in additive manufacturing, facilitating advancements in efficiency and quality within the field.This article is protected by copyright. All rights reserved.

Tailoring the structural, morphological, surface wettability and hardness features of Makrofol HS for surface applications: effect of DBD treatment

ABSTRACT In current research, Makrofol HS polymeric films have been utilized to evaluate the alterations in the surface properties under an atmospheric-pressure dielectric barrier discharge (DBD) plasma source. Upon DBD plasma exposure with various exposure durations ranging from 10 min to 120 min, the structural, surface wettability, surface free energy, surface roughness, and hardness features of Makrofol HS films have been studied and analyzed using different techniques. The FTIR spectra demonstrated that small changes in the band intensities correspond to the C-O-C as well as C=O bonds. Further, the changes in the absorption bands are correlated to the treatment time, leading to two critical processes, degradation, and crosslinking. The results of surface wettability displayed that the liquids' contact angle decreased from 84 ± 3o, 77 ± 3o and 62 ± 2o for water, glycerol, and dimethyl to 45 ± 1o, 42 ± 1o, and 36 ± 1o for untreated and treated samples at the highest treatment time, respectively. Also, the surface free energy significantly amended with increasing plasma exposure time. This modification in the treated surface indicates the increase in the polar groups on the treated surfaces, which then become hydrophilic surfaces. The samples' surface roughness parameters Ra, Rq, and Rz increased from 0.057 ± 0.003, 0.084 ± 0.004 and 0.366 ± 0.02 mm for untreated samples to 1.463 ± 0.073, 1.707 ± 0.085, and 6.839 ± 0.34 mm for treated samples at the highest treatment time, respectively. The Vickers hardness measurements showed an increase in the Vickers hardness from 12.31 ± 0.61 kgf/mm2 for the untreated sample to 44.89 ± 2.24 kgf/mm2 for the treated sample at the highest duration.

Influence of cutting tool design on ultrasonic-assisted drilling of fiber metal laminates

Ultrasonic-assisted drilling (UAD) is a machining process that is known to improve the hole quality and reduce cutting forces. Previous studies focused on optimizing cutting parameters to improve the hole quality in conventional drilling (CD) and UAD, as well as to finding the optimum vibration parameters (frequency and amplitude) that will increase the effectiveness of the UAD process. However, the influence of cutting tool type during UAD has been largely overlooked. This research aims to address this gap by analyzing the effect of cutting tool type during UAD on the cutting forces and hole quality in GLARE (Glass Laminate Aluminum-Reinforced Epoxy) laminates. Four types of drills, namely, twist drill (TD), double cone drill (DCD), a step drill type 1 (SD1), and step drill type 2 (SD2) with different step length, were selected for this study. The lowest thrust force (47.04 N) and torque (0.079 Nm) were achieved using twist drill, while DCD, SD1, and SD2 exhibited higher thrust forces (12.81%, 20.69%, 41.3%) and torques (94%, 92%, 91%), respectively. In addition, TD produced high-quality holes with lowest surface roughness (Ra 1.66 μm, Rz 10.58 μm) and minimal burr formation (entry burr height 152.3 μm, exit burr height 69.22 μm). Conversely, DCD, SD1, and SD2 showed higher surface roughness Ra (23%, 16%, 24%) and Rz (16%, 37%, 29%), respectively, compared to the TD. Holes drilled using SD1 and SD2 generally had smaller burr height. Overall, UAD system effectively reduced cutting forces at low spindle speed and feed rate. To achieve higher drilling quality, specifically to reduce the surface roughness and exit burr height, a medium spindle speed of 3000 rpm, a feed rate of 225 mm/min is recommended. Drilling at higher cutting parameters using UAD resulted in a decline in hole quality, except for entry burr height.

The Selection of Cutting Speed to Prevent Deterioration of the Surface in Internal Turning of C45 Steel by Small-Diameter Boring Bars

The turning of small-diameter deep holes is usually critical when the process of machining is unstable and the use of a special boring bar is often necessary. This paper is focused on the influence of cutting speed with a combination of cutting conditions such as feed and tool overhang on chatter marks, surface roughness and roundness of machined holes. In the experiment, two types of tool material for indexable boring bars were used, namely cemented carbide and steel. These are a group of boring bars used for the internal turning of holes of small diameters with indexable cutting inserts. Monolithic carbide boring bars are already used for internal turning of holes of even smaller diameters. Uncoated turning inserts made of cermet were used. The cutting tests were performed on the DMG CTX alpha 500 turning center. In the case of the steel boring bar, decreasing the cutting speed really led to an increase in the quality of the surface roughness and reduced the formation of chatter marks and large chatter marks. The cemented carbide boring bar also followed a similar trend, but it should be noted that the overall effect was not so great. This means that increasing the cutting speed makes the cutting process less stable and, vice versa, lower values of cutting speed reduce the formation of chatter marks and the related deterioration of the surface quality. The occurrence of chatter is directly related to the increase in the surface roughness parameters Ra and Rz of the machined surface. It can be stated that the dependence of roundness deviations on cutting speed values has a similar character to the results of the measured surface roughness values. Therefore, if the cutting speed is increased, it will make the cutting process less stable; this is also indirectly reflected in larger roundness deviations. However, it is necessary to state that this phenomenon can be observed in turning holes with small diameters using the steel boring bar, where the unstable cutting conditions materialized in the form of chatter marks.

A process chain study for manufacturing nitinol stents

Nitinol is a commonly used alloy for manufacturing medical devices (i.e., stents). This study examines the process chain for manufacturing nitinol stents, focusing on the effects of laser cutting, heat treatment, and electropolishing processes on the stent’s final surface roughness, strut thickness, weight, and recoil. The laser cutting’s experimental results showed an optimal surface roughness (Ra) under 1.20 μm at 65% and 95% spot overlap, corresponding to feed rates of 300 mm/min and 749 mm/min, respectively. Heat treatment experiments on expanded stent samples revealed the lowest recoil of 0.78 mm achieved at 550°C for 720 s for 0.2 mm strut thickness. Electropolishing using 18V for 20 s provided the greatest reduction in surface roughness (Ra and Rz), along with a decrease in the weight and wall thickness. The results highlight the importance of optimizing process parameters to obtain desired surface quality, shape setting, and dimensional characteristics for functional nitinol stents. The research provides insights into enhancing the manufacturing of self-expanding nitinol stents for improved clinical outcomes.

Influence of surface polishing on the degradation behavior of biodegradable Magnesium alloy

Mechanical polishing can significantly improve the surface integrity of Mg alloys to reduce the corrosion rate (CR) by minimizing the galvanic corrosion sites. In this study, an emery-polishing attachment on a lathe machine has been used for surface polishing of as-turned cylindrical ZM21 Mg alloy. Using Taguchi’s L9 orthogonal array, three process variables with three levels were investigated and optimized for minimum surface roughness (Ra and Rz values) of Mg-alloy samples. The minimum surface roughness values of Ra; 195 nm and Rz; 1481 nm were obtained corresponding to emery paper (EP) grade; 2000, rotational speed; 250 rpm, and polishing time; 2 min. An in-vitro immersion study was conducted in simulated body fluid (SBF) for up to 28 days to investigate the degradation behavior of as-turned and as-polished Mg alloy samples. In-vitro study showed that the as-turned samples (surface roughness; Ra: 640 nm, Rz: 4640 nm) had a higher degradation rate (CR: 3.9 mm year−1 after 28 days) with a higher volume of H2 evolution rate, whereas the polished sample with the minimum surface roughness (Ra: 195 nm, Rz: 1481 nm) exhibited lower weight loss, H2 release rate, degradation rate (CR: 0.95 mm year−1 after 28 days) and minimum loss of mechanical strength. Based on the present study, polishing is recommended as a secondary operation after machining of Mg alloy to reduce the corrosion rate for biodegradable implant applications.

The analysis of the effect of varying feed values in each pass on tool wear and surface roughness in turning of AISI 4140

Machining is a complex process between the cutting tool and the workpiece, and in this process, the cutting tool constantly wears out with various wear mechanisms. Tool-wear estimation in turning is a complicated process; thus, there is a need for a study to reveal the time-dependent behavior of tool wear. In this study, tool wear and surface roughness change during the turning process of AISI 4140 steel at low cutting speeds were examined in detail with variable feed values for the first time. For this purpose, a half-minute cutting time was applied for each pass to analyze the tool wear as gradually as possible. Tool wear (flank, notch, and nose), surface roughness (Ra, Rz, and Rt), and chip morphologies were examined after each turning operation. The flank wear reached 0.3 mm, which is one of the tool life criteria according to ISO 3685, and the experiments were terminated at the 149th minute. Initially, a significant surface improvement (approx. 300%) was observed due to the decrease in feed values. In subsequent experiments, the effect of feed was significantly reduced due to increased tool wear, and limited surface roughness improvement (approx. 30%) was observed. At the beginning of the experiment, the chip breaker function of the cutting insert was successful at almost all feeds. However, in subsequent experiments, it was found that even at higher feeds, the chip breaker geometry of the insert deteriorated due to tool wear, causing changes in chip morphology, and resulting in long and undesirable chips.

Surface properties and flexural fatigue strength of an advanced lithium disilicate

The aim of this study was to evaluate the surface properties and fatigue mechanical behavior of an advanced lithium disilicate ceramic in comparison to lithium disilicate and zirconia. First, discs (n = 15, diameter = 13.5 mm and thickness = 1.2 mm) were made from the following materials: 4Y-PSZ – 4% mol yttria-stabilized zirconia (IPS e.max ZirCAD A2); LD - lithium disilicate (IPS e.max CAD); ALD - advanced lithium disilicate (CEREC Tessera). The specimens were crystalized/sintered and subsequently analyzed by a rugosimeter (Mitutoyo SJ-410) to determine surface roughness (parameters Ra and Rz). Specimens were subjected to biaxial flexural fatigue testing using the step-test method (20 Hz; 10,000 cycles per step; initial stress of 200 MPa; and step size of 25 MPa) until specimen fracture. Statistical analyses included Shapiro-Wilk, Kruskal-Wallis, and post-hoc tests for roughness data, while survival analysis (Kaplan-Meier and Mantel-Cox) and reliability analysis (Weibull modulus) were applied to flexural fatigue strength data. Hardness (Vickers) results were submitted to analysis of variance (1-way ANOVA) and Tukey's test. Zirconia (4Y-PSZ) showed higher FFS, CFF (467 MPa and 115216 cycles) and survival compared to the other materials. ALD had the lowest FFS, CFF (215 MPa and 11,908 cycles) and survival. ALD showed lower Weibull modulus (m = 6.63 for FFS; m = 1.27 for CFF) than LD for FFS (m = 17.33), and lower than LD (m = 4.64) and 4Y-PSZ (m = 6.69) for CFF. ALD showed the lowest Ra (0.07 μm) and Rz (1.05 μm) values, while 4Y-PSZ (Ra = 0.22 μm; Rz = 1.91 μm) and LD (Ra = 0.21 μm; Rz = 2.17 μm) showed higher and similar values. Zirconia (4-YPSZ) was the hardest material, while lithia-based ceramics (LD and ALD) presented the lowest and similar hardness values. Fractures originated in surface defects in the tensile stress concentration region. ALD has lower flexural fatigue strength compared to the other tested materials, along with higher variability (lower structural reliability).

Optimization and Mathematical Modelling of Surface Roughness Criteria and Material Removal Rate when Milling C45 Steel using RSM and Desirability Approach

This work consists of studying the workability of C45 steel in face milling by using coated carbides (GC4040). The objective is to investigate the evolution of surface roughness (Ra, Ry, and Rz) and Material Removal Rate (MRR) according to cutting speed, feed rate, and depth of cut. A full-factorial design (43)was adopted in order to analyse the obtained experimental results via bothAnalysis of Variance (ANOVA) and Response Surface Methodology (RSM)design. The levels of cutting speed were as follows: Vc1=57 m/min; Vc2=111m/min; Vc3=222 m/min and Vc4=440 m/min. The ranges of feed rate werefz1=0.024 mm/tooth; fz2=0.048 mm/tooth; fz3=0.096 mm/tooth and fz4=0.192mm/tooth. As for the depth of cut levels, they included ap1=0.2 mm; ap2=0.4mm; ap3=0.6 mm, and ap4=0.8 mm. To determine mathematical models tomake predictions, a statistical analysis of the results by using RSM was appliedto obtain the main effects and interactions plot of the answer. Furthermore, amulti-objective optimization procedure for minimizing Ra and maximizing themetal removed rate using the desirability approach was also implemented.Therefore, the developed models can be effectively used to predict the surfaceroughness criteria and the material removal rate in machining C45 steel. Theresults indicated that feed rate is a significant factor affecting surfaceroughness (Ra: 52.37%, Ry: 80.97%, and Rz: 54.96%), followed by cuttingspeed (Ra: 37.88%, Ry: 12.90%, and Rz: 24.43%). Meanwhile, cutting speedand feed rate are the most significant parameters on the MRR with a contribution of 29.5% followed by the depth of cut with 11.62%.