Steel Coupons Research Articles

A comparison of persistence of SARS-CoV-2 variants on stainless steel

SummaryThe survival of newer variants of SARS-CoV-2 on a representative surface has been compared to the established UK circulating isolate to determine whether enhanced environmental stability could play a part in their increased transmissibility. Stainless steel coupons were inoculated with liquid cultures of the three variants, with coupons recovered over seven days and processed for recoverable viable virus using plaque assay. After drying, there was no significant difference in inactivation rates between variants, indicating that there is no increased environmental persistence from the new variants.

Formation of Iron Sulfides on Carbon Steel in a Specific Cement Grout Designed for Radioactive Waste Repository and Associated Corrosion Mechanisms.

Carbon steel coupons were buried in a specific low-pH cement grout designed for radioactive waste disposal and left 6 months in anoxic conditions at 80 °C. The corrosion product layers were analyzed by µ-Raman spectroscopy, XRD, and SEM. They proved to be mainly composed of iron sulfides, with magnetite as a minor phase, mixed with components of the grout. Average corrosion rates were estimated by weight loss measurements between 3 and 6 µm yr−1. Corrosion profiles revealed local degradations with a depth up to 10 µm. It is assumed that the heterogeneity of the corrosion product layer, mainly composed of conductive compounds (FeS, Fe3S4, and Fe3O4), promotes the persistence of corrosion cells that may lead to locally aggravated degradations of the metal. New cement grouts, characterized by a slightly higher pH and a lower sulfide concentration, should then be designed for the considered application.

Bacteriocin-Like Inhibitory Substance (BLIS) Activity of Enterococcus faecium DB1 Against Biofilm Formation by Clostridium perfringens.

The antibiofilm effect of bacteriocin-like inhibitory substance (BLIS) from Enterococcus faecium DB1 against Clostridium perfringens was investigated in the present study. BLIS of E. faecium DB1 significantly reduced biofilm formation by C. perfringens in a dose-dependent manner for 24 and 48h. In particular, treatment with BLIS of E. faecium DB1 significantly inhibited biofilm formation by C. perfringens on chicken meat and stainless steel coupon surfaces. Moreover, BLIS of E. faecium DB1 decreased the viability of C. perfringens biofilm and planktonic cells, indicating that the reduction of biofilm formation by C. perfringens might be achieved by killing the bacterial cells. Taken together, the present results suggest that BLIS of E. faecium DB1 can be a promising antibiofilm agent to eradicate C. perfringens.

THERMODYNAMIC AND KINETIC STUDIES OF THE CORROSION INHIBITION OF MILD STEEL IN 0.5 M HCl USING NAPOLEONAE IMPERIALIS LEAVES EXTRACT.

Thermodynamics and kinetics of the inhibitory behaviour of Napoleonae imperialis leaves extract on the corrosion of mild steel in 0.5MHCl solution were examined using gravimetric technique at different concentrations of the extract and temperatures (303, 313 and 323 K). Results show that increase in extract concentration and temperature increased the inhibition efficiency of the extract. However, inhibition efficiency decreased with time of immersion of the mild steel coupons. Activation energy of adsorption values obtained at different extract concentrations were positive at all concentrations but higher than that of the blank. Thermodynamic and kinetic data obtained conform to Langmuir adsorption isotherm. The adsorption mechanism suggests physisorptive adsorption process and aligned with the first order kinetics. The highest extract concentration (2.5g/l) showed maximum inhibition efficiency of 84.15% at 323K. The overall results suggest that the leaves extract of Napoleonae imperialis acts as a good inhibitor for the corrosion of mild steel in 0.5MHCl solutions.

Bayesian inference for calibration and validation of uniaxial reinforcing steel models

With ever-advancing structural design and evaluation techniques becoming available for structural engineers, the required level of knowledge about nonlinear material behavior in civil structures has increased accordingly over recent years. In the context of finite element (FE) modeling, constitutive material models play a crucial role in the computation of the structural response. Although significant research has focused on characterizing the stress–strain relationship in reinforcing steel, most of these efforts have considered experimental response data from monotonic tests. In this paper, results from experimental cyclic tests conducted on 36 reinforcing steel coupons obtained from three major manufacturers encompassing two widely used steel grades are employed to gain a deep understanding of the relationship between model formulation and response, for three well-known hysteretic reinforcing steel one-dimensional constitutive stress–strain relationships. Initially, the three models are briefly described. Then, a local sensitivity analysis (LSA) is performed to provide an insight on the influence of each model parameter in model response, followed by a global sensitivity analysis (GSA) performed to further understand the composition of response variability due to parameter uncertainty. Model calibration is then carried out in a probabilistic manner, using the Bayesian estimation (BE) framework through the use of Markov Chain Monte Carlo (MCMC), and informed by LSA and GSA results. Parameter estimation results for each model are discussed, with an emphasis on the level of accuracy of predictions achieved with estimated sets of parameters in each case. The amount of information extracted about each parameter during calibration is assessed, leading to a performance comparison between the three constitutive laws under study.

Biofilm growth by Listeria monocytogenes on stainless steel and expression of biofilm-related genes under stressing conditions.

This research was carried out to investigate the differences in adhesion and growth during biofilm formation of L. monocytogenes from different sources and clonal complexes. Biofilm by L. monocytogenes (isolates CLIST 441 and 7: both lineage I, serotype 1/2b, CC3; isolates 19 and 508: both lineage II, serotype 1/2c, CC9) was grown on stainless steel coupons under different stressing conditions (NaCl, curing salts and quaternary ammonium compounds-QAC), to determine the expression of different genes involved in biofilm formation and stress response. CLIST 441, which carries a premature stop codon (PMSC) in agrC, formed high-density biofilms in the presence of QAC (7.5% w/v) or curing salts (10% w/v). Reverse Transcriptase-qPCR results revealed that L. monocytogenes isolates presented differences in transcriptional profile of genes related to biofilm formation and adaptation to environmental conditions. Our results demonstrated how L. monocytogenes can survive, multiply and form biofilm under adverse conditions related to food processing environments. Differences in transcriptional expression were observed, highlighting the role of regulatory gene networks for particular serotypes under different stress responses.

Investigations on Corrosion Inhibitory Effect of Newly Quinoline Derivative on Mild Steel in HCl Solution Complemented with Antibacterial Studies

This study analyzed the corrosion inhibitory effects and the antibacterial action of the quinoline derivative, namely N'-(2-hydroxybenzylidene)-2-(quinolin-8-yloxy)acetohydrazide (NHQA). NHQA prevention of corrosion behavior was investigated using weight loss experiments on mild steel coupons in hydrochloric acid. Weight loss tests achieved improved inhibition performance for NHQA, and the high inhibitor efficiency was reached at 303 K, of 93.4 percent at 500 ppm NHQA. Moreover, the effect of immersion time on carbon steel corrosion was investigated using strategies for weight loss. The NHQA mechanism for corrosion inhibition was also examined. These findings confirm that the NHQA molecules can be used in industrial applications as a possible corrosion inhibitor. In an aqueous solution, the synthesized compound (NHQA) can also be used as an antimicrobial agent. The microbial inhibitive efficacy of NHQA against Gram-positive (Staphyloccocus aureus) and Gram-negative bacteria (Escherichia coli, Proteus vulgaris, Klebsiella pneumoniae, and Pseudomonas aeruginosa) was evaluated employee a disc diffusion technique. NHQA has considerable inhibition efficacy toward all investigated bacteria.

Air Permeability of Maraging Steel Cellular Parts Made by Selective Laser Melting.

Additive manufacturing, such as selective laser melting (SLM), can be used to manufacture cellular parts. In this study, cellular coupons of maraging steels are prepared through SLM by varying hatch distance. Air flow and permeability of porous maraging steel blocks are obtained for samples of different thickness based on the Darcy equation. By reducing hatch distance from 0.75 to 0.4 mm, the permeability decreases from 1.664 × 10−6 mm2 to 0.991 × 10−6 mm2 for 4 mm thick coupons. In addition, by increasing the thickness from 2 to 8 mm, the permeability increases from 0.741 × 10−6 mm2 to 1.345 × 10−6 mm2 at 16.2 J/mm3 energy density and 0.14 MPa inlet pressure. Simulation using ANSYS-Fluent is conducted to observe the pressure difference across the porous coupons and is compared with the experimental results. Surface artifacts and the actual morphology of scan lines can cause the simulated permeability to deviate from the experimental values. The measured permeability of maraging steel coupons is regression fit with both energy density and size of samples which provide a design guideline of porous mold inserts for industry applications such as injection molding.

Non-Linear through-Hole Fabrication By Electrochemical Machining

Electrochemical machining (ECM) is a manufacturing technology that precisely removes material from metallic workpieces by electrochemical oxidation and dissolution into a working electrolyte. ECM is especially well suited for workpieces to be fabricated from "difficult to cut" materials, and is able to produce parts with complicated/intricate geometries. In ECM, an electrochemical cell is established with the workpiece as the anode and a shaped tool as the cathode; after engaging a suitable electrical potential, the shaped tool is advanced into the workpiece and a mirror image of the tool is formed. Compared to mechanical or thermal machining processes, where material is subtracted by cutting or by electric/laser discharges, respectively, ECM does not suffer from tool wear or introduce a heat-affected surface layer to the workpiece. As a result, ECM has strong utility as a manufacturing technology for a wide variety of workpiece materials and ultimate part geometries, and encompasses machining, deburring, boring, radiusing and polishing processes, among others. As noted, ECM provides particular value when applied to high-strength/tough, brittle, and/or work-hardening materials such as high strength steel, chrome-copper alloy (C18200), nickel alloy (IN718), cobalt-chrome alloy (Stellite 25), tantalum-tungsten alloy (Ta10W), molybdenum and tungsten, since the material removal process involves no mechanical interaction between the tool and the part.This talk will summarize recent work performed to demonstrate the feasibility of non-linear through-hole machining in tubular metallic substrates by ECM, through application of a multi-step forming process. One category of feature that is often challenging to fabricate in hard-to-machine materials is a non-linear passage or through-hole. This is in contrast to a straight passage, which is generally uncomplicated to achieve with many methods, whereas in general non-linear through-holes in tube walls must be machined from both the inner and outer diameter of the wall. For easily-machined materials, machining steps taking place on the inner diameter of the workpiece can be accomplished with a sufficiently advanced multi-axis CNC mill, but for hard-to-machine materials it is difficult or impossible to achieve the necessary bearing force and/or angle of approach of the tool. Thermal machining methods (electric discharge machining, etc.) are viable in some cases, but as noted above will result in a heat-affected layer on the machined surface that is problematic in many applications. Experimental ECM results will be presented for fabrication of "chevron" through-hole features (~90° path axis deflection) in both planar and annular workpieces, embodying a proof-of-concept demonstration and an early step in development of an ECM methodology for fabricating integrated muzzle brake vane apertures directly into the barrel wall of large-bore cannon. Figure Caption (Top left) Patent drawing of modular muzzle brake concept for cannon, showing overall design and cross-section of a single vane, with vane passage geometry highlighted in orange. (Bottom left) Schematic 3D model of a cannon barrel with integrated muzzle brake vanes. (Top right) Schematic of two-sided ECM fabrication of nonlinear “chevron” passage in a composite stack of flat coupons. (Bottom right) Photographs of cross-sectioned flat steel coupons with fabricated “chevon” passages. Reference (from figure) Cler, D.L. and D. Forliti. U.S. Patent No. 7,600,461, issued 13 Oct 2009. Figure 1

Fast-cycle hydrogen peroxide nebulization against frequent healthcare-associated micro-organisms: efficacy assessment

Hydrogen peroxide (H2O2)-based technology is currently used with the aim of controlling microbial contamination in hospital settings. However, the long cycles required result in prolonged room turnover time, thus precluding a wider implementation of the technology. To assess the efficacy of a shorter cycle of nebulized H2O2 against healthcare-associated micro-organisms, further comparing among multidrug-resistant and multidrug-susceptible strains. The efficacy of a standard cycle (1h) and of a faster cycle (15min) of a 7% H2O2 nebulized solution was compared against bacteria and yeasts. MDR and MDS strains were inoculated on polyvinyl chloride, stainless steel, linoleum, napa leather, and formica coupons, and their growth ability was compared. Globally, the mean efficacy of the standard cycle ranged between 82.5% (±17.0) and 95.9% (±8.3), while the efficacy of the fast cycle ranged between 84.4% (±17.0) and 95.7% (±10.5). No statistically significant differences were found for the majority of the tested cycles and materials. For all the tested strains, no differences were found regarding the efficacy of cycles. The very high disinfection efficacy of the fast cycle was found to be similar to that of the standard cycle. Moreover, a similar efficacy was also demonstrated when comparing between multidrug-resistant and multidrug-susceptible strains. This study supports a wider implementation of the technology, with the expected advantages of reducing room turnover time, costs, and indirect infection transmission. Further assessment of the efficacy of this faster cycle against other emergent microbial global threats would be highly recommended.

Time-dependent reliability of corroded circular steel tube structures: Characterization of statistical models for material properties

The tubular steel structure is one of the most commonly used structural forms exposed in corrosive environments and its structural reliability should be addressed accordingly. However, the materials properties of corroded steel tubes were implicitly represented by those of corroded steel plates in previous studies. Experimental data and reliability analysis regarding the properties of corroded steel tubes (rather than plates) are still inadequate for reliability study. In response to these issues, this study conducted 96 tensile tests with respect to the different degrees of corrosion in circular steel tubes. Results demonstrated that the fracture mode of the corroded steel coupons changed to brittle fracture, and the necking phenomenon in the failure area gradually disappeared. Ultimate strength, yield strength and corresponding strain were remarkably degraded, and the yield plateau shortened and even disappeared as the degree of corrosion increased. Moreover, normal distribution can represent the yield strength of corroded steel tubes, and this distribution was verified by five hypothesis tests in this study. The mean yield strength of corroded steel presented a quadratic declining tendency at increasing corrosion rates. The time-dependent reliability analysis of corroded steel tubes was conducted in two corrosion scenarios (i.e. atmospheric and marine environments) and six levels of applied loadings (reflecting different safety levels). Finally, a set of trial material safety factors for ensuring sufficient safety margin was assessed, which can provide a reference for related specifications of steel tube structures subjected to atmospheric corrosion and/or marine environments.

Evaluation of Arginine‐Modified Polyepoxysuccinic Acid as Anti‐scaling and Anti‐corrosion Agent

AbstractArginine‐modified polyepoxysuccinic acid (Arg‐PESA) was used as a scale inhibitor to study its anti‐scaling and anti‐corrosion performance. The existence of arginine groups enhances the adsorption and chelation of calcium substances, thus inhibiting the formation of a calcium scale. The effects of temperature, scale inhibitor concentration, pH, and calcium ion concentration on scale inhibition performance were studied. The morphologies and structures of the calcium scale and carbon steel coupons were observed and characterized by spectroscopic and microscopic methods. The interaction between Arg‐PESA and different crystal surfaces of calcium carbonate was simulated by molecular dynamics to elucidate the anti‐scaling mechanism. The addition of Arg‐PESA also significantly enhanced the dispersion of iron oxide.

Mechanical properties of low yield point steels subjected to low-cycle structural damage

This paper focuses on the effects of prior cyclic loading on the subsequent monotonic tensile properties of low yield point (LYP) steels compared to that of virgin material. Carefully designed axial steel coupons machined from LYP steel plates were tested under various cyclic loading protocols to model seismic-induced damage and then monotonically tensioned until fracture to obtain their remaining mechanical properties. The experimental results indicate that a prior history of cyclic loading caused an increase in strength but a decrease in both ductility and stiffness of LYP steels. Moreover, significant cyclic hardening was observed in LYP steels, which could be characterized as combined isotropic and kinematic hardening, of which the former component played an overwhelmingly dominant role.

Growth and Survival of Attached Listeria on Lettuce and Stainless Steel Varies by Strain and Surface Type

The foodborne pathogen Listeria monocytogenes lives as a saprophyte in nature and can adhere to and grow on surfaces as diverse as leaves, sediment, and stainless steel. To discern the mechanisms used by L. monocytogenes for attachment and growth on various surfaces, we studied interactions between the pathogen on lettuce and stainless steel. A panel of 24 strains (23 L. monocytogenes and 1 Listeria innocua) were screened for attachment and growth on lettuce at 4 and 25°C and on stainless steel at 10 and 37°C. Overnight growth of attached cells resulted in a 0- to 3-log increase on lettuce, depending on the strain and the temperature. Among the worst-performing strains on lettuce were two from a large cantaloupe outbreak, indicating that factors important for interactions with cantaloupe may be different from those required on lettuce tissue. Strains that grew the best on lettuce belonged to serotypes 1/2a, 1/2b, and 4b and were from cheese, potatoes, and water-sediment near produce fields. Confocal microscopy of L. monocytogenes tagged with constitutively expressed green fluorescent protein indicated associations with the cut edges and veins of lettuce leaves. On stainless steel coupons, there was a 5- to 7-log increase at 10°C after 7 days and a 4- to 7-log increase at 37°C after 40 h. Statistically, surface growth on stainless steel was better for serotype 1/2a than for serotype 4b strains, even though certain serotype 4b strains grew well on the coupons. The latter included strains that originated from produce and water-sediment. Some strains were fit in both environments, whereas others showed variability between the two different surfaces. Further analysis of these strains should reveal molecular factors needed for adherence and surface growth of L. monocytogenes on different biotic and abiotic surfaces.

Concentration Dependent Effects of Green Inhibitors on Gravimetric Indices of Corrosion Linked Metal Integrity

The use of plant phytochemicals as anti-corrosion agents is gaining widespread acceptance. This study was designed to evaluate the concentration dependent effects of green inhibitors from Pennisetum purpureum (elephant grass) Mangifera indica (mango leaves) and Heveabrasiliensis (rubber leaves) on some gravimetric indicators of corrosion linked metal stability. The material strength, weight loss, corrosion rate of the metal coupons and the inhibition efficiency of the green inhibitors were determined after 3 days. Our findings revealed a slight increase (p=0.05) in material strength (MS) of Pennisetum purpureum inhibitor treated - iron and steel at 100% inhibitor relative to their controls (minus Pennisetum purpureum -iron and steel coupons) and also relative to the (+Mangifera indica inhibitor and + Heveabrasiliensis -treated iron and steel coupons at 50% concentration. The material strength for P. purpureum-treated aluminium was slightly increased (p>0.05). There was also a slight decrease (p>0.05) in the weight loss of P. purpureum exposed iron coupon at a 100% inhibitor when compared to the controls, 50% P. purpureum exposed iron coupon and at 50 and 100% H. brasiliensis and M. indica-treated iron coupon in 15% acid medium. Pre-treatment of test metals with the combined green inhibitors at 50 and 100% concentration caused a significant (p≤0.05) decreases in weight loss and increases in material strength of all three test metals when compared to their respective inhibitor-free controls, and when treatment was done with a single green inhibitor. There was a slight decrease in the corrosion rate of iron, aluminium and steel coupons in acid medium treated with 50% P. purpureum inhibitor when compared to the same parameter of other green inhibitors evaluated in this study, albeit, the reduction was not significant (p>0.05). There was a further decreases (p≤0.05) in the corrosion rate of iron and steel when the combined green inhibitors at 100% concentration(+All green inhibitors (PAGI) at 100%) were used relative to when treatment was done using individual green inhibitors separately. The inhibition efficiency of the combined green inhibitors at 50% concentration on aluminium, iron and steel was 86% 57% and 60% respectively. While the treatment of the same coupons with combined inhibitors (+PAGI at100% concentration) increased the inhibition efficiency to 88% 75% and 74% for aluminium, iron and steel respectively. Overall, the study revealed the possible anti-corrosion effects of the extracts of H. brasiliensis, P. purpureum and M. indica on aluminium, iron and steel coupons and the synergism in anti-corrosion characteristics of these green inhibitors when combined. This study establishes the anticorrosion effects of H. brasiliensis, P. purpureum and M. indica extracts.

Prediction of tungsten insert gas welding process parameter using design of experiment and fuzzy logic

The focus of this study is to predict tungsten inert gas (TIG) welding process parameter such as heat input for stabilizing heat and removing post weld crack formation in mild steel weldment. The main input parameters examined are the welding current, voltage and speed whereas the measured (response) parameter is heat input. Statistical design of experiment was done by means of central composite design method using the range and levels of independent variables. The experiment was carried out 20 times (with 5 specimens per run) using 60 mm x 40 mm x 10 mm mild steel coupons. The plate samples were cut longitudinally with a Single-V joint preparation, with the edges beveled. The welding process utilizes 100% pure argon as a protecting gas to shield the weld specimen from external interaction. The interaction between the input and response variables was analyzed using a fuzzy logic system. The result showed that for a welding current, voltage and speed of 190 A, 21 V, and 2.0 mm/s respectively, the predicted heat input was 0.912 kJ/mm whereas for input parameters of (170 A, 25 V, and 2.0 mm/s) and (180 A, 23 V, 0.98 mm/s), the predicted heat inputs were 1.07 kJ/mm and 1.380 kJ/mm, respectively.

The characterization of deformation stage of metals using acoustic emission combined with nonlinear ultrasonics

This paper introduces a new acoustic emission (AE) characteristic to determine the deformation stage of metals under quasi-static loading. The AE characteristic is extracted from the derivative of the cumulative AE energy with respect to time. The reproducibility of the developed feature is demonstrated on a set of A572 Grade 50 steel coupons loaded up to different levels of plastic deformation, and then evaluated using the AE data recorded from aluminum 1100. To address the prior load-dependence of AE data, nonlinear ultrasonics is studied to quantify the presence of plastic deformation as a way to determine the initiation strain during quasi-static load testing typically used for evaluating metallic structures with the AE method. The sensitivity of nonlinear ultrasonics is compared with the linear ultrasonics showing the higher sensitivity of third harmonic nonlinearity coefficient to plastic deformation. The microstructural changes affecting ultrasonics are identified with metallographic characterizations.

Detecting Bacterial Biofilms Using Fluorescence Hyperspectral Imaging and Various Discriminant Analyses.

Biofilms formed on the surface of agro-food processing facilities can cause food poisoning by providing an environment in which bacteria can be cultured. Therefore, hygiene management through initial detection is important. This study aimed to assess the feasibility of detecting Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurium) on the surface of food processing facilities by using fluorescence hyperspectral imaging. E. coli and S. typhimurium were cultured on high-density polyethylene and stainless steel coupons, which are the main materials used in food processing facilities. We obtained fluorescence hyperspectral images for the range of 420–730 nm by emitting UV light from a 365 nm UV light source. The images were used to perform discriminant analyses (linear discriminant analysis, k-nearest neighbor analysis, and partial-least squares discriminant analysis) to identify and classify coupons on which bacteria could be cultured. The discriminant performances of specificity and sensitivity for E. coli (1–4 log CFU·cm−2) and S. typhimurium (1–6 log CFU·cm−2) were over 90% for most machine learning models used, and the highest performances were generally obtained from the k-nearest neighbor (k-NN) model. The application of the learning model to the hyperspectral image confirmed that the biofilm detection was well performed. This result indicates the possibility of rapidly inspecting biofilms using fluorescence hyperspectral images.

Data on electrochemical deterioration of mild steel in rice husk agro-waste developed nano-coolant

Investigation of the electrochemical deterioration of mild steel in rice husk agro-waste developed nano-coolant is presented in this study. Corrosion rates of mild steel versus nano-coolant concentration are presented. Linear polarization test data was also covered. Mild steel coupons were immersed in different concentrations (ten concentrations and the control as a reference) of the developed nano-fluid for a period of 24, 48, 72, 96, 120, 144 and 168 h. Corrosion rate was calculated based on ASTM Standard G1–03 standard practice for preparing, cleaning and evaluation of corrosion test specimens. Open circuit potential measurements (OCP) were also carried out. The potential of the steel samples in the nano-fluid with respect to time was investigated. This dataset could be used in evaluating the performance of mild steel in rice husk based nano-coolant.

Experimental Analysis of Corrosion Rate of Developed Nanocutting Fluid from Admixture Nanoparticles

This study is an evaluation of the performance of mild steel coupons in developed silica nanofluid from rice husk ash. Gravimetric and electrochemical measurement methods were used for the experimental work. The chemical composition of silica was confirmed by SEM/EDS graph. The gravimetric test result shows that sample F (1.00 g/L RHA) gave the lowest corrosion rate of 1.8E−05 mm/year at 168 h. It was also observed that better protection of the material was achieved with increase in exposure time, hence lower corrosion rates. From the results of electrochemical tests, there was significant change in corrosion potential and corrosion rate with change in nanofluid concentration. Corrosion rate was positively slowed down by lower concentration of silica nanofluid. Sample C (0.25 g/L RHA) revealed the lowest instantaneous corrosion rate of 0.02876 mm/year. Silica nanofluid developed from rice husk ash may be better suited for cutting mild steel than the conventional cutting fluid.