Final Hardness Research Articles

Effect of Freezing Temperature on the Thermal, Rheological, and Gelatinization Properties of Freeze-Thaw-Dehydrated Potato Powder.

To promote the application of freeze-thaw-dehydrated (FTD) potatoes and their gels, this study aimed to investigate the effects of freezing temperature on the physicochemical and gel properties of FTD potato powder and their correlation. The results revealed that, as the freezing temperature decreased, the solubility exhibited an overall downwards trend resulting from soluble solids and amylose liberation. Owing to the better cell integrity at -20 °C, the solubility was greater than that of the other treatment groups. In contrast, the trough viscosity and melting enthalpy increased, and the final viscosity, and setback first increased but then decreased. Regarding the properties of the FTD potato powder gel, the storage modulus, loss modulus, hardness, adhesiveness, chewiness, and consistency first increased but then decreased with decreasing freezing temperature. At a moderate freezing temperature (-20 °C), the solubility and stability of the FTD potato powder were well maintained, and the final viscosity, setback, and hardness reached their highest values. Correlation analysis revealed that, with decreasing freezing temperature, the amount of FTD potato powder initially increased, followed by a decrease in the final viscosity and setback. This trend was positively correlated with the hardness of the FTD potato gel (r = 0.98, r = 0.93).

Assessing melt pool temperature independence from hardness via photodiode-based plank thermometry (PDPT)

Directed Energy Deposition (DED) has emerged as a promising metal additive manufacturing technique due to its ability to create components comparable or superior to traditional fabrication. Although industrial adoption of this technology is underway, there exists a considerable need to improve the predictability of the components it manufactures to promote wider adoption of this technology. Currently, melt pool temperature is the primary metric for build monitoring and control. However, stronger correlations must be established between the process parameters, including melt pool temperature, and resulting material outcomes to determine if melt pool control is a sufficient metric to control part quality. The goal of this research is to establish correlations between laser power (W), scanning speed (mm/s), powder flow rate (g/min), average melt pool temperature (C), and hardness. The average melt pool temperature was measured through Photodiode-based Planck thermometry (PDPT) with dual on-axis photodiodes. To obtain the correlation between these factors, 54 samples of Inconel 718 were printed, cross-sectioned, and tested using a Vickers diamond indenter. The resulting correlations exhibited extremely low R2 values and validated the findings of previous studies in that process parameters are exceedingly poor predictors of component properties. Average melt pool temperature lacked a significant correlation with hardness, instead process scanning speed demonstrated a more significant impact on the final material hardness. Since hardness is largely dictated by average grain size which in turn is controlled primarily by solidification rate, solidification rate should be the focus of future work to control material properties. The results of this study indicate that melt pool thermal control is not a sufficient metric to control part quality, and a solution is needed that can oversee the build process in such a way that solidification rate can be monitored and controlled in addition or instead of melt pool temperature. Future work must be done to apply the PDPT methodology to real time calibrated indirect measurement of melt pool solidification rates to improve prediction and control of final part mechanical properties.

Influence of the as quenched state and tempering temperature on the final microstructure and hardness of a high strength medium carbon steel

The present study aimed to investigate the impact of the as-quenched microstructure and tempering temperature on the final microstructure and hardness of a medium-carbon, low-alloy steel using dilatometry, Electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM). The results revealed substantial differences in the continuous heating stage of tempering in bainitic and martensitic samples, primarily attributed to the auto-tempering process during cooling. Tempering was carried out at 550 and 620 °C, and dilatometry results, along with microstructure analysis, indicated incomplete decomposition of retained austenite (RA) at both temperatures during a 30-min hold in the bainitic sample. The results show that non-decomposed RA, following the tempering of bainite, transformed into blocky fresh martensite, while no evidence of fresh martensite was observed in the martensitic sample. A new approach using EBSD and SEM images revealed that the decomposition of M/A (martensite/austenite constituent) zones in the bainitic sample resulted in the formation of a chain of aggregated chromium carbide zones at the grain boundaries. In contrast, the martensitic zone exhibited a uniform distribution of carbides in the microstructure. The stability of the phases was examined using the TCFE10 (thermodynamics) and MOBFE5 (mobility) modules of the DICTRA Themo-Calc software. Hardness measurements on all samples indicated decreases by about 18–24 % in the martensitic sample after tempering, while the bainitic sample exhibited a 5 % increase in hardness after tempering, attributed to secondary hardening and fresh martensite formation.

Evaluation of the cumulative effect of photodynamic therapy and local fluoride on the microhardness and topography of demineralized enamel and cementum surfaces

BackgroundThe present study aimed to determine the cumulative effect of two photodynamic therapy methods with methylene blue and indocyanine green and two topical fluoride therapy methods with fluoride varnish and silver diamine fluoride alone and in combination on the microhardness and topography of demineralized enamel and cementum surfaces. Materials and methodsSeventy-two sound human teeth were selected, and their buccal and lingual surfaces were assigned to two main groups of enamel and cementum using simple randomization. The initial surface hardness (SH) of the enamel and cementum in each sample was determined using a micro-Vickers hardness tester using a 200-g force in 10 s. Then artificial caries was induced by immersion in a demineralizing/remineralizing solution (i.e., each tooth provided two samples, one on the buccal aspect and the other on the lingual aspect). Each enamel/cementum main group was divided into two subgroups using simple randomization based on the local fluoride type (fluoride varnish and silver diamine fluoride) and the type of the photosensitizer agent (methylene blue and indocyanine green). Finally, 16 groups were achieved (n = 9). The final surface hardness of the enamel and cementum samples was determined as described above. Finally, the sample surfaces were prepared for the surface topography evaluation under a scanning electron microscope. The baseline microhardness was compared between the 16 study groups in the first step using one-way ANOVA. Then, three-way ANOVA was used to evaluate the effect of fluoride, laser, and surface (enamel and cementum) on microhardness. ResultsAll the groups exhibited decreased microhardness due to the induction of artificial caries. In both main groups of enamel and cementum, the lowest decrease in microhardness was recorded with combined photodynamic therapy and methylene blue photosensitizer material and fluoride varnish (15.1 % for cementum and 16.7 % for enamel), and the highest decrease in microhardness was recorded in the methylene blue group (35.7 % for cementum and 34.9 % for enamel). ConclusionThe combination of photodynamic therapy with the photosensitizer substance methylene blue or indocyanine green together with fluoride varnish or silver diamine fluoride is effective on the remineralization of demineralized enamel and cementum. Although there is no difference between the combination of photodynamic therapy with fluoride varnish compared to fluoride varnish alone, both of these treatments are more effective than using photodynamic therapy alone.

Inorganic Phosphate Effect in a Hydrogen Peroxide-based Bleaching Agent: Physicochemical, Mechanical, and Morphological Properties of Dental Enamel.

This in vitro study aimed to assess the impact of incorporating calcium glycerophosphate (CaGP) and sodium fluoride (NaF) in addition to 35% hydrogen peroxide concerning the enamel mechanical and morphological properties. Specimens of bovine enamel were chosen based on their initial surface hardness (SHi) and subsequently divided into five gel groups (n=12): 1) 35% Hydrogen Peroxide (HP) Gel; 2) HP + 0.1% NaF Gel (HP/NaF); 3) HP + 0.25% CaGP Gel (HP/CaGP); 4) HP + 0.1% NaF + 0.25% CaGP Gel (HP/NaF/CaGP) and 5) HP Blue 35% Gel (HP Blue). The bleaching gels were applied thrice, for 40 min, at intervals of 7 days each. After 21 days, the final surface hardness (SHf), integrated hardness (IH), Polydispersity Index (PdI) and Zeta Potential (Zp), surface roughness (Ra, after and before), and surface/structural analysis by Scanning Electron Microscopy (SEM) were determined. The data were submitted to ANOVA (one-way and two-way) followed by the Student-Newman-Keuls test (α=0.05). The addition of NaF to HP reduced demineralization by 11.5% in relation to HP (p<0.05). The NaF/CaGP association reduction is 22.8 and 20% higher in comparison to HP/NaF/CaGP and HP Blue, respectively. The IH when the PH/NaF/CaGP bleaching gel was applied, was 14% higher compared to HP and HP Blue groups. It can be concluded that the association of NaF and CaGP with the 35% hydrogen peroxide gel (HP/NaF/CaGP) significantly changed tooth enamel demineralization in terms of surface, depth, roughness, and enamel morphology.

A methodological study of the hardness of cooked Chinese noodles based on the texture analyzer

Abstract A generic instrumental analysis method, matched with sensory evaluation, for the hardness test of Chinese dried noodles after cooking, was established in this study. The cut and compression mode was compared at first, followed by an analysis of the hardness response curve obtained from cut code with three-stage. Then the reliability of this method was verified with 20 commercially available noodles. Results showed that the hardness difference between the two samples obtained using compression mode was only 0.087 %. In contrast, a 6.34 % difference was obtained using cut mode with the hardness value of 296.12 ± 6.10 g and 278.47 ± 12.22 g, respectively. Three parameters, including initial hardness (F 1), material hardness (K), and final hardness (F 2), were extracted from the shear curve to characterize the hardness of cooked noodles. A ranking difference of F 1, F 2, and K between 20 commercially available noodles was found, which illustrated various characteristics of cooked noodles. In summary, the cut mode was more suitable for determining the hardness of cooked noodles; F 1, F 2, and K, obtained from a three-stage analytical method for the inner and outer hardness of cooked noodles characterization, had excellent performance to match with sensory evaluation.

A detailed study on the cooking kinetics of fresh and hard to cook common beans (Phaseolus vulgaris L.): A case study on bean accessions of different market classes

A large-scale study was conducted to obtain a more holistic understanding of the cooking behavior for different bean accessions in terms of cooking kinetics and time to cook. Fresh and aged soaked beans from twenty-four accessions were assessed for texture evolution during cooking at 95 °C using the most informative objective compression texture analysis method. Texture evolution was modelled by the conventional fractional conversion model as well as modified three-parameter models to capture the lag phase. The initial texture varied across bean accessions and is significantly positively related to bean size. Significant but limited differences in initial texture on ageing were observed, the difference being accession dependent. The texture evolution during cooking, cooking kinetics and time to cook varied across bean accessions and storage conditions and all bean accessions developed the hard to cook defect. The softening rate constants for fresh beans were significantly higher (0.026–0.053) and more variable than for aged beans (0.008–0.014, almost similar values). Fresh and aged beans of a given accession softened to similar levels of final relative hardness. The lag phase was more prominent in aged beans (up to ≈25 min) than non-aged beans (0–7 min). Therefore, the difference in time to cook for fresh beans across accessions is mainly determined by the difference in initial hardness and cooking rate constant, while for aged beans these differences depend on initial hardness and lag time and to a lesser extent on the cooking rate constant.

Identifying the sensory profiles of naturally fermented table olives and their application to industrially processed cultivars

The study examines the sensory profile of industrially processed, naturally fermented table olives. A detailed set of descriptors crunchiness, hardness, bitter, fibrousness, saltiness, chewiness, sourness, green fruit, ripe fruit, flesh/stone separation, piquant, and musty was developed for green and turning colour Manzanilla and Gordal products, using Quantitative Descriptive Analysis (QDA). Green Gordal (GG) was characterised by higher than average chewiness (scores 7.0–7.1), crunchiness (7.5–8.2), hardness (scores 7.7–8.0) and fibrousness (6.2–6.4). In contrast, turning colour Gordal was lower than average in bitter (2.9–3.4), crunchiness (4.1–4.9), hardness (4.5–5.1) and fibrousness (4.4–4.7). Initially, the green Manzanilla was characterised by higher than average levels of bitter (6.5–7.1), crunchiness (7.2–7.4), hardness (6.9–7.0), and saltiness (3.2–3.3). However, they diminished to about average levels by the end of the fermentation process. The turning colour Manzanilla was initially associated with elevated bitter (5.6–5.9) and lower-than-average final crunchiness (4.6–4.9), hardness (5.1–5.7) and fibrousness (4.5-4.6). However, the final product resulting from this treatment had relatively high significant values for acetic/vinegar (3.5), astringent (3.5), musty (2.0), piquant (2.5), rancid (1.8) and ripe fruit flavour (3.3). The Hotelling T2 test, PCA, and the correlation circle reinforced the specific sensory profile associated with cultivars and maturation stages. Minimal changes were observed over time. PLS-R revealed associations between physicochemical characteristics and sensory profiles such as bitter with phenol content (standardised coefficient; 0.881) and texture (0.755) or ripe fruit with bitter index (0.475), among others.

Monitoring of the heating rate of a motorized gear system using UV-curable resin containing Y2WO6:Yb3+-Er3+ up-converting nanoparticles as optical temperature sensor

The ability to create various three-dimensional objects and precisely deposited layers has enabled manufacturers using UV-curable resins to produce customized and complex composite parts with greater efficiency and precision. There are many products used in this photo-induced solidification process, and one of them is a mixture of organic compounds forming a resin, which is cured using ultraviolet light to achieve the desired final hardness. In addition, the combination of this resin with innovative materials has led to the creation of interesting elements with a wide variety of applications. For this reason, this work describes the implementation of lanthanide-based luminescent nanoparticles Y2WO6 doped with Yb3+ and Er3+ and admixed in a resin, for deposition on a metallic gear surface via painting and UV curing. The as-prepared luminescent gears start to generate heat due to the occurrence of mechanical friction when they start to work. Analyzing the ratio between the thermalized Er3+ emissions at 525 nm (2H11/2 → 4I15/2) and 550 nm (4S3/2 → 4I15/2) we could remotely detect small temperature variations that gears undergo through friction. This technique is especially useful in monitoring temperature in elements where measurements with thermographic cameras or with direct contact is inaccurate or is not possible. This work can open new horizons in monitoring of heat flow in various scientific and industrial processes, utilizing the benefits of non-invasive temperature detection via luminescence thermometry technique.

Hardening of Cylindrical Bars with Water Impinging Jet Quenching Technique

Hardening of carbon steel products by austenitization and immersion in a quenching medium is a widely used heat treatment to obtain a hard and strong martensitic structure. To avoid the undesired consequences, such as residual stresses or insufficient hardening depth, the cooling rates must be accurately measured and controlled. This can be achieved using the impinging water jet quenching technique. The aim of this work is to perform hardening of four low‐alloyed 70 mm cylindrical carbon steel bars, using impinging water jet quenching technique with different jet flow rates, and to analyze its effect on thermal evolution and residual stresses. The temperature evolution during quenching experiments is recorded and used as input to a comprehensive quenching model to predict phase transformations, final hardness, and residual stresses of cylindrical bars. All four quenching experiments result in a fully hardened martensitic state. Furthermore, a decrease in jets’ flow rate, within a certain interval, results in different thermal histories and in lower compressive residual stresses on the surface. The results from quenching simulations show promising hardness, microstructure, and residual stress predictions that are validated by hardness measurements, optical microscopy, and residual stress analysis using X‐Ray diffraction method.

Experimental Investigation of Flexural Behavior of Hybrid Self-Compacting Pozzo-Lime Reinforced Concrete Beams

The main goal of this research is to investigate the effect of using hybrid self-compacting Pozzo-lime concrete on the bending behaviour of reinforced concrete beams. To achieve this objective, a set of eight laboratory samples comprised of reinforced concrete beams measuring 1400 mm in length and 150 x 250 mm in dimensions were subjected to two-point bending testing. These beams were constructed using hybrid self-compacting Pozzo-lime concrete at varying depths. The samples' ultimate strength, ductility, cracking pattern, and mode of failure, as well as the load-displacement diagram, are subsequently assessed. The laboratory sample of the P75C25 beam exhibited the greatest final strength, hardness, and ductility, according to the findings of this study.

Effect of nanometric β-calcium glycerophosphate supplementation in conventional toothpaste on enamel demineralization: An in vitro study

The aim of this study was to evaluate the effects of supplementing toothpastes containing 1100 ppm F with micrometric or nanometric [beta]-calcium glycerophosphate (β-CaGPm/β-CaGPn) on artificial enamel demineralization, using a pH cycling model. Bovine enamel blocks (4 mm × 4 mm, n = 120) selected using initial surface hardness were randomly allocated to ten toothpaste groups (n = 12): without fluoride or β-CaGPm or β-CaGPn (Negative control), 1100 ppm F (1100 F), and 1100 ppm F plus 0.125%, 0.25%, 0.5%, and 1.0% of β-CaGPm or β-CaGPn. Blocks were treated two times per day with toothpaste slurry and subjected to five pH cycles (demineralizing and remineralizing solutions) at 37 °C. The final surface hardness, percentage of surface hardness loss (%SH), cross-sectional hardness (ΔKHN), and profile analysis and lesion depth subsurface were analysed using polarized light microscopy (PLM). Fluoride (F), calcium (Ca), and phosphorus (P) concentrations were also measured. Data were analysed using ANOVA and Student-Newman-Keuls tests ([alpha] = 0.001). Blocks treated with 1100 F toothpaste containing 0.5%β-CaGPm or 0.25%β-CaGPn showed with reduced %SH values when compared with those treated with 1100 F alone (p < 0.001). Reduced lesion depths (ΔKHN and PLM) were observed for the slurry made up of 1100 F and 0.25%β-CaGPn (p < 0.001). The addition of β-CaGPm and β-CaGPn did not influence the enamel F concentration, with the 1100 F/0.25%β-CaGPn group exhibiting the highest Ca and P enamel concentrations (p < 0.001). Based on the findings of this in vitro study, we can conclude that the fluoride toothpaste produced a superior effect when combined at an appropriate β-CaGP molar ratio. This effect was achieved with a lower proportion of β-CaGP in the form of nanometric particles.

Nutritional composition and staling properties of gluten-free bread-added fermented acorn flour.

The present study aimed to improve the nutritional quality of gluten-free bread with the addition of acorn flour and to determine the characteristics of the final product. Formulations were adjusted with separately non-fermented and two different fermented acorn flours at different levels (0, 15, 30, and 45%). The breads were assessed in terms of their chemical and physical properties, and their staling characterization was also estimated. Results showed that the fermentation of acorn flour before adding it to the formulation affected some chemical properties, and the addition of increasing amounts of acorn flour generally had a positive effect on the chemical composition. Furthermore, the highest protein, total phenolic content, Ca, K, Mg, Mn, and Fe values were obtained from breads, including fermented acorn flour with chickpea yeast (FAC). However, compared to non-fermented acorn flour (AF), FAC and fermented acorn flour without chickpea yeast (FA) addition caused decreases in weight and volume of breads. Both crust L* and crumb L* values showed a significant reduction with increased acorn addition levels (from 71.88 and 77.22 to 42.26 and 41.15, respectively). The highest initial and final hardness values (T 0 and T ∞) were observed with FAC-added samples, and Avrami exponent n was higher than 1 for only FAC-added breads. Although fermented acorn addition had positive effects on the nutritional profile of breads, the sensory properties of the samples were negatively affected.

Gel Rheological Properties and Storage Texture Kinetics of Starches Isolated from Anchote (Coccinia abyssinica (Lam.) Cogn.) Cultivars.

Anchote is a tuber crop indigenous to Ethiopia. Starch hydration properties and important gel characteristics which include: color, gel rheological properties (at 2, 4, 6, 8, and 10% starch:water w/w) and gel texture evolution (at 10% starch:water w/w), during 0 to 192 h storage (at 4 °C), of anchote starches isolated from four anchote cultivars (Desta 01, Desta 24, white and red) were evaluated and compared with potato and cassava starches (PS and CS). The lightness (L*) and whiteness scores of the anchote starch ranged up to >95, with slight differences among the cultivars, making them pure starches. Swelling power (SP) and water solubility index (WSI) of the anchote starches increased with increasing cooking temperature (40, 50, 60, 70, 80 and 90 °C), and their rate of increase varied significantly with the control starches, as follows: CS < anchote starches < PS. Anchote starch gels resisted higher stresses before breaking their structure and showed higher elasticity with lower (tan δ)1 values than PS and CS gels. They also had greater viscoelastic moduli even at lower concentrations than the PS and CS gels, and their stability increased with increasing concentration. The study of the gels' texture evolution during storage revealed that anchote starch gels had significantly higher (≥40%) initial and final (after 192 h) hardness and were less adhesive than the PS gel. Despite some significant differences in the studied starch gel quality parameters among the starches from the anchote cultivars, the results suggested their promising potential as additional new materials in the development of food products, specifically as a functional ingredient for the formulation of gel-like products.

Hot-forming of a 980 MPa third generation advanced high strength steel

This paper considers the effect of processing route on the final microstructure hardness and tensile behavior of a 980 MPa third generation advanced high strength steel (3G-AHSS). Of particular interest is the use of a hot stamping thermal schedule that mimics a quench and partition (Q&P) heat treatment process normally used to produce Q&P grade steel sheet. For comparison purposes, samples were also produced using a quench and temper (Q&T) processing history. The experiments were performed using a Gleeble 3500 thermo-mechanical simulator system. Large coupons were produced using both processing routes from which microstructure, hardness, and tensile samples were extracted. Mechanical properties results were compared with the as-received material. Both processing routes resulted in strength levels that were close to that of the as-received material; however, the total elongation of the Q&P processed samples was 52% higher than that of the Q&T processed material.

Numerical Modeling for the Prediction of Microstructure and Mechanical Properties of Quenched Automotive Steel Pieces.

In this work, we present an efficient numerical tool for the prediction of the final microstructure, mechanical properties, and distortions of automotive steel spindles subjected to quenching processes by immersion in liquid tanks. The complete model, which consists of a two-way coupled thermal-metallurgical model and a subsequent (one-way coupled) mechanical model, was numerically implemented using finite element methods. The thermal model includes a novel generalized solid-to-liquid heat transfer model that depends explicitly on the piece's characteristic size, the physical properties of the quenching fluid, and quenching process parameters. The resulting numerical tool is experimentally validated by comparison with the final microstructure and hardness distributions obtained on automotive spindles subjected to two different industrial quenching processes: (i) a batch-type quenching process with a soaking air-furnace stage prior to the quenching, and (ii) a direct quenching process where the pieces are submerged directly in the liquid just after forging. The complete model retains accurately, at a reduced computational cost, the main features of the different heat transfer mechanisms, with deviations in the temperature evolution and final microstructure lower than 7.5% and 12%, respectively. In the framework of the increasing relevance of digital twins in industry, this model is a useful tool not only to predict the final properties of quenched industrial pieces but also to redesign and optimize the quenching process.

Experimental investigation on the impact of mechanical properties of SiC, Al2O3 and ZrSiO4 particles on AA6063 composites

In this research, processing temperature and the addition of micro-sized SiC, Al2O3, and ZrSiO4 to AA6063 metal matrix composites affects the mechanical properties investigated. A stir casting technique was used to evenly disperse SiC, ZrSiO4, and Al2O3 particles in an AA6063 matrix composite. Because the bonding between the ceramic and AA6063 interfaces reduced the mobility of the grain and twin boundaries, ceramic/aluminum composites could withstand greater external loads. The results show that reinforcing quantities of AA6063- ZrSiO4 composites were softer than AA6063- Al2O3 and AA6063-SiC composites. The results reveal a sweet spot for ceramic content in composites where the final tensile strength and hardness are optimal. The numbers proved to be percentages: 6–12 % for AA6063-SiC composites, 6–12 % for AA6063- ZrSiO4 composites, and 18 % for AA6063-Al2O3 composites. These experiments show that ceramic-reinforced composites have greatly improved tensile strength and hardness. The most beneficial additions are ZrSiO4 and Al2O3, which boost tensile strength by 53 % and hardness by 127 %, respectively.

A comparative evaluation of effect of denture cleansers on color stability, surface roughness and hardness of polyamide denture base material.

Different denture cleansers have an effect on color and different surface properties of polyamide denture base material. Thus, selecting a denture cleanser solution for polyamide denture base materials should be based on the properties of the denture cleanser itself. The present in vitro study is aimed to evaluate and compare the effect of different denture base cleansers on color, surface roughness and hardness of polyamide denture base material. Thirty specimens of commercially available polyamide denture base material were fabricated and divided into three groups of 10 each. Specimens from each group were immersed in different denture cleansers (sodium perborate, thyme oil and ozonated water) for 10 mins per day for 180 days. Initial and final color, surface roughness and surface hardness of each specimen were measured and the difference was calculated. Data was tabulated and subjected to statistical analysis using One way ANOVA for pair wise comparison. Polyamide denture base resin exhibited some degree of change in color, surface roughness, and surface hardness in all denture cleansers but was not statistically significant. The choice of denture cleanser for different denture base resins should be based on the chemistry of resin and the cleanser, denture cleanser concentration and duration of immersion.

Effect of Intercritical Annealing on the Properties of Dual Phase Steel via Finite Element Method

Dual phase (DP) steels are rapidly becoming more and more popular for automotive applications. They offer a weight reduction with a combination of energy absorption for crash zones. Rails, reinforcements, back panels, cross members, and pillars can be given as application examples. DP steels microstructure consists of a soft ferrite matrix with hard martensite islands. The hard martensite islands provide strength while the ductile ferrite provides formability. The strength level of DP steel is related to the amount of martensite in the microstructure, and the martensite amount can be arranged via intercritical annealing. In this work, thermodynamic analysis of St52 steel was carried out with Thermo-Calc software. A1 and A3 temperatures were determined by calculating the temperature-dependent phase fractions. Intercritical annealing temperatures were determined according to the calculated critical temperatures (A1 and A3). The intercritical annealing process was modelled by using Simheat NxT software. In this modelling and simulation work, the effect of intercritical annealing temperature on the final microstructure and hardness of DP steel was investigated.

Nanoindentation test of a DLC coated high-speed steel substrate using a two-dimensional axisymmetric finite element method

Diamond-Like Carbon is a thin coating that has high hardness, chemical inertia and low coefficient of friction characteristics that can improve the performance of cutting tools and mechanical components. To identify the characteristics of this film it is important to carry out mechanical tests, such as nanoindentation, which can provide important information in understanding and improving coating techniques and, when combined with the finite element method, leads to more detailed results of material behavior during testing. Considering this, the present work aimed to study and apply a nanoindentation test simulation of a Diamond-Like Carbon coated high-speed steel specimen. The results of the indenter penetration versus load were compared with experimental data seeking correlation of the model. A great proximity was observed between the experimental results and the results obtained in the simulation. When comparing the final indentation force, a proximity of 93.9 % and 95.5 % was found for the model with only one indentation and with partial indentations, respectively, thus validating the created model. The impact of modifying the indenter tip radius for the partial indentation method was also evaluated. The tip radius variation did not have a significant impact on the results of final indentation force and material hardness. The material hardness was also obtained in the simulation, which was equal to the experimental: 9.25 GPa.