Universal Hardness Tester Research Articles

Time-Dependent Austempering of High Carbon Steel using Epoxidized Cotton Seed Oil

The work seeks to ascertain the potential of austempering time on the microstructure and mechanical properties of high carbon steel using epoxidized cotton seed oil bath. Five sets of high carbon steel (HCS) samples were heated to an austenitizing temperature of 830°C in the furnace, soaked at that temperature for 1 hour and quenched interruptedly at a temperature of 310°C in epoxidized cotton seed oil (ECO) bath for 15 – 75 minutes (at regular intervals of 15 minutes for different samples’ sets). Subsequently, samples air-cooled at ambient temperature. Hounsfield tensometer, Indentec universal hardness tester and Izod impact tester were used to determine the mechanical properties of the austempered samples. From the outcome of the investigation, appreciable improvement was noted in tensile strength (1210 N/mm2), hardness (397 HBN) and impact strength (12.1 J/mm) of the austempered samples. Further, samples were subjected to metallographic sample preparation, succeeded by microstructural examination using scanning electron microscope (SEM). The structures observed to be majorly bainite. The austempering time of 15 minutes produced the outstanding combination of mechanical properties.

Comparative assessment of enamel remineralisation on the surface microhardness of demineralized enamel - an in vitro study.

ObjectiveThe main objective of the study was to compare two different remineralising materials containing casein phosphopeptide-amorphous calcium phosphate, bioactive glass on enamel surface microhardness.Materials and MethodsThirty premolars were used for specimen preparation. Group 1 (the control group) consisted of intact enamel samples, group 2: CPP-ACPF (Tooth Mousse Plus), group 3: bioenamel remineralising gel (Prevest DenPro). All specimens were subjected to demineralisation except the control group, followed by which remineralising agents were applied. A universal hardness tester was used to assess the surface microhardness of all samples. Results were analysed using one-way ANOVA test and comparison was analysed using Scheffe’s post hoc least significant difference (LSD) test.ResultsBoth remineralising agents used in groups 2 and 3 have shown significant outcome in terms of improving the surface microhardness in comparison with the control group. Group 2 increased the enamel hardness by 8.34 where P = 0.023 whereas group 3 increased the hardness by 5.87, where P = 0.01.ConclusionGroup 2 has a superior hardness value than group 3; however, no statistically significant results were obtained between both the groups.

Characteristics of hardness at local propellers with variations of timing by using sandblasting method

Sandblasting is one method of surface treatment that aims to improve the characteristics of material properties, such the hardness materials. This process was done by spraying abrasive material onto the surface of the object with the pressure. The purpose of this study was to increase the hardness of local propellers as a result of the sandblasting process. In this study, the material used aluminum alloys in the form of propellers of local fishing boats. While abrasive material used aluminum oxide with size 100 mesh. Then the pressure used 3, 4, and 5 bars with 25, 50, and 75 seconds in shooting times by angle 90. Measurement of hardness value used Universal Hardness Tester by macro-Vickers with load parameters 5 Kgf and indentation time of 10 seconds. The results showed that the longer the shooting time, the hardness of the propeller be increased 32.4% from the material that has not been carried out by the sandblasting process. The factor of time variation and shooting pressure has a significant effect on the results of the hardness in the specimen.

The effectiveness of betel leaf (piper betle Linn) extract gel and cocoa bean (theobroma cacao L) extract gel application against the hardness of enamel surface in vitro

Objective : Nowadays several ways have been evolved to increase the hardness of the enamel surface as an effort to prevent caries. One of the alternatives that can be used is application of gel with herbal basic material.Material and Methods : The use of herbal basic material is preferred by people because the side effects are relatively small compared to synthetic drugs. Piper betle and cocoa beans are medicinal plants that is often used by people to inhibit caries. This is because piper betle and cocoa beans contain hardness that may influence the enamel surface. The purpose of this research was to determine the effect of piper betle extract gel and cocoa bean extract gel against the hardness of enamel surface. The samples, maxillary first premolar teeth, which has been extracted and does not have caries, were divided into 3 treatment groups: piper betle extract gel, cocoa bean extract gel, and distilled water as a negative control. Each treatment group consisted of 8 samples. The samples are decoronated in cemento-enamel junction (CEJ) areas and planted on orthoplast blocks with labial surface facing up. Samples were applied in labial enamel surface to 5, 15 and 35 minutes period times. Samples before and after the application in each treatment group were measured using Universal Hardness Tester. Data were collected and analyzed using ANNOVA Repeated test.Results : Showed there were significant differences (p <0.05) of enamel surface hardness before and after the application of cocoa bean extract gel. There were no significant differences (p> 0.05) of enamel surface hardness before and after the application of piper betel extract gel and distilled water.Conclusion : Therefore it can be concluded that cocoa been extract gel is more effective to increase the hardness of email surface.

Effect of Storage Medium and Aging Duration on Mechanical Properties of Self-Adhesive Resin-Based Cements

The aim of this study was to investigate the effects of storage medium and aging duration on Martens hardness (HM) and indentation modulus (EIT) of self-adhesive resin-based cements (SARCs). A total of 416 discs were fabricated from 8 SARCs (n = 52 per SARC): (i) BeautyCem (BEA), (ii) Bifix SE (BIF), (iii) Clearfil SA Cement Automix (CLE), (iv) RelyX Unicem2 Automix (RXU), (v) SeT (SET), (vi) SmartCem 2 (SMC), (vii) SoloCem (SOC) and (viii) SpeedCEM (SPC). The specimens were ground and stored in (a) physiological saliva, (b) artificial saliva, (c) sodium chloride and (d) distilled water, at 37°C for 1, 7, 14, 28, 90 and 180 days. Non-aged specimens (3 hours after photo-initiation) of each SARC acted as control groups. HM and EIT were assessed using a universal hardness testing machine. Data were analyzed using Kolmogorov-Smirnov and Kruskal-Wallis tests and paired t-test, and 3-, 2- and 1-way ANOVA with post hoc Scheffé test (p<0.05). SARC materials exerted the highest influence on HM and EIT values (p<0.001, partial eta squared [ηP²] = 0.753 and 0.433, respectively), closely followed by aging duration (p<0.001, ηP² = 0.516 and 0.255) and storage medium (p<0.001, ηP² = 0.043 and 0.033). The interaction effect of the combinations of the 3 independent parameters was also significant (p<0.001, ηP² = 0.163 and 0.133). The lowest initial HM and EIT was presented by CLE, followed by SET and SPC; highest HM was for BIF, followed by RXU and SMC. SET gave a greater HM and EIT percentage decrease than SOC, SPC, BEA, SMC, RXU or CLE. Aging duration is a major factor affecting the micromechanical properties of SARCs, while storage medium was shown to have a significant but minor role.

The effect of Curcuma domestica Val - Tamarindus indica L mixed solution (“kunyit asam”) on microhardness and roughnessof human tooth enamel

Nowadays,peoples tendto seekan alternative treatment from traditional plants because it is side effects relatively less than synthetic drugs. One of the famous traditional medicinedrinks in Indonesia is “kunyit asam”. People was make it with mixed both Curcuma domestica Val and Tamarindus indica L. Beside it has many advantages for health such as increasing stamina, it also has a good taste, so many people consumed it. However, the acid content in this drink maycause enamel erosion. Therefore the aim of this present study is to determine the in vitro effect of “kunyit asam” solution towards microhardness and roughness of human enamel tooth. The pH of solutionwas measure using a digital pH meter, while the calcium content measure using the Atomic Absorption Spectroscopy (AAS). This study used 40 permanent maxillary first incisor that has been extracted from the patient who came to dental polyclinic of hospitals in Polewali Mandar regency, West Sulawesi Province during February 2015-April 2015 period. The roots of the teeth were removed at the cementoenamel junction. Tooth crowns placed on blocks orthoplast with labial surface facing up. Samples were randomly divided into 2 groups equally andimmersed in aquadest solution pH 7.0 (negative control) (Group I) or “kunyit asam” solution pH 3.0 (Group II) for 14, 28, 42 and 56 minutes respectively. An Universal Hardness Tester (Affri® Universal Hardness Tester, Japan) was used to measure enamel surface microhardness, while to measure enamel surface roughness wasused a Roughness Tester (Surftest 301 Mitutoyo, Japan). Both measure were done before and after immersed in solution. Data were statistically analyzed using Levene, paired-t one-way Analysis of Variance (ANOVA) and Least Significance Different (LSD) tests. The results of present study showed that there was no significant difference (p>0.05) microhardness but significant differences (p<0.05) for the roughness of tooth enamelbefore and after immersion in both group. In conclusion, pH (3.0) “kunyit asam” decreased of microhardness, meanwhile it is calcium content (794.23 µg) increased roughness of human enamel tooth in vitro .

EFFECT OF POST-WELD HEAT TREATMENT ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ARC WELDED MEDIUM CARBON STEEL

Effect of post- weld heat treatment on the microstructure and mechanical properties of arc welded medium carbon steel was investigated. Medium carbon steel samples were butt- welded by using the shielded metal arc welding technique and, thereafter, heat treated by annealing, normalising and quench hardening in water. The microstructure of the as- welded and post- weld heated samples was characterised by means of optical microscopy while the hardness, toughness and tensile properties of the samples were determined by using Indentec universal hardness testing machine, Izod impact testing machine and Denison tensile testing machine respectively. The results of the optical microscopic test show that fine grains of pearlite in ferrite were obtained in normalized samples and martensite was also observed in quenched samples. On the other hand, mechanical property tests indicated that normalized welded specimens gave good combination of mechanical properties. http://dx.doi.org/10.4314/njt.v35i2.14

Grain refinement of C-Mn steel through thermo-mechanical processing

Purpose – The application of new technologies requires, however, modern rolling mills. Indeed, in manufacturing plants of older types, strict compliance with the developed rolling regimes is not always feasible. Improving the mechanical properties in such cases is possible only by means of cooling. Compressive deformation behavior of carbon–manganese (C-Mn) grade has been investigated at temperatures ranging from 800-900°C and strain rate from 0.01-50 s−1 on Gleeble-3800, a thermo-mechanical simulator. Simulation studies have been conducted mainly to observe the microstructural changes for various strain rate and deformation temperatures at a constant strain of 0.5 and a cooling rate of 20°C s−1. Design/methodology/approach – The project begins with simulation of a hot rolling condition using the thermo-mechanical simulator; this was followed by microstructural examination and identification of phases present by using an optical microscope for hot-rolled coil and simulated samples; grain size measurement and size distribution studies; and optimization of finishing temperature, coiling temperature and cooling rate by mimicking plant processing parameters to improve the mechanical properties. Findings – As the strain rate and temperature increase, pearlite banding decreases gradually and finally gets completely eliminated, thereby improving the mechanical properties. True stress–strain curves were plotted to extrapolate the effect of strain-hardening and strain rate sensitivity on austenite (γ) and austenite–ferrite (γ-a) regions. To validate the effect of strain rate and temperature over the grain size, the hardness of simulated samples was measured using the universal hardness tester and the corresponding tensile strength was found from the standard hardness chart. Practical implications – The results of the study carried out have projected a new technology of thermo-mechanical simulation for the studied C-Mn grade. These results were used to optimize the plant processing parameter like finishing and coiling temperature and finishing stands strain rate. Originality/value – By controlling the hot rolling conditions like finishing, coiling temperature and cooling rate, structures differing in mechanical properties can be obtained for the same material. Accurate understanding of a structure being formed when different temperatures are applied enables the control of the process that assures intended structures and mechanical properties are achieved.

Corrosion Behavior of Copper in Biodiesel-Diesel-Bioethanol (BDE)

The present study aims to investigate the impact of biodiesel-diesel-bioethanol (BDE) fuel blend on the corrosion behavior of copper. Static immersion tests in B45D35E20 (45% biodiesel, 35% diesel and 20% bioethanol) were carried out at room temperature (25°C) and 50° for 408 hours. Mechanical, physical and chemical properties of copper were investigated before and after immersion tests. Investigations were carried out on the change in morphological properties using optical microscope; change in chemical structure using FTIR; change in mass and volume by weight loss measurement; and hardness changes using universal hardness tester. The changes of fuel properties of the blend such as total acid number (TAN) and color changes were also investigated. The results showed that the corrosion rate of copper in B45D35E20 at high temperature (50°C) is comparatively lower than the previous studies reported for pure biodiesel (B100).

Setting characteristics of a resin infiltration system for incipient caries treatment

ObjectivesThis study investigated the curing efficiency, the extent of atmospheric oxygen inhibition to the polymerization reaction and the mechanical properties of a new resin-infiltration system for caries treatment. MethodsThe curing efficiency was estimated by measuring the percentage degree of cure (%DC) of thin resin films (h: 150μm, Ø: 5mm, n=3), 10min after 40s exposure to a quartz halogen bulb (750mW/cm2) light curing unit (Optilux 501, Demetron/Kerr, USA), in the absence of O2, by micro ATR-FTIR spectroscopy. The extent of O2 inhibition on resin film setting (width in μm) was assessed by transmission optical microscopy on thin films (h: 150μm, Ø: ∼7mm, n=5) placed between two transparent cover slips and exposed to air from lateral sites. For each sample the extent of inhibition was measured at 5 different locations. The mechanical properties were tested employing Instrumented Indentation Testing according to ISO 14577:2002. Resin specimens (h: 2mm, Ø: 10mm, n=5) were prepared employing cylindrical teflon moulds enclosed in transparent matrix strips and glass slides as before. The measurements were performed employing a Vickers indenter attached to a universal hardness testing machine (ZHU2.5/Z2.5 plus test Xpert software, Zwick/Roell, Ulm, Germany). The parameters tested were Martens Hardness (MH), Vickers Hardness (VHN), Indentation Elastic Modulus (EIT) and elastic to total ratio of indentation work (ηIT). For all these tests, specimens of a conventional light-curing bonding resin (HB-Heliobond, Ivoclar-Vivadent, FL) prepared as above were used as control. Student t-test was used to identify statistically significant differences between the two materials in the parameters tested (a: 0.05). ResultsThe results of the materials tested were: (a) [% DC]; IC: 57.4±1.5, HB: 59.8±2.4, (b) [Width of O2 inhibition/μm]; IC: 33.1±6.5, HB: 23.6±4.4, (c) [MH/N/mm2] IC; 116±16, HB: 261±35, (d) [VHN]; IC; 15.4±2.5, HB: 22.1±1.8, (e) [EIT/(GPa)]; IC; 2.3±0.4, HB: 7.5±0.5, and (g) [ηIT (%)] IC; 50.3±3.4, HB: 35.1±1.9. The IC presented no significant difference in terms of % DC, higher thickness of the inhibited layer, lower MH, VHN, EIT and greater ηIT values than HB. Conclusions and Clinical SignificantThe resin-infiltrating system for incipient caries treatment demonstrated the same curing efficiency with a conventional unfilled bonding resin, but exhibited higher extent of oxygen inhibition, lower hardness, lower elastic modulus and higher plastic to elastic indentation energy.

Corrosion Characteristics of Copper in Malaysian Bioethanol and Gasoline Blends

The present study aims to investigate the corrosion characteristics of copper commonly encountered in the spark ignition (SI) engine fuel system with Malaysian bioethanol and gasoline blends. Static immersion tests in E0 (gasoline), E10 and E85 were carried out at room temperature for 1320 h. Mechanical, physical and chemical properties of copper was investigated before and after immersion tests. Investigations were carried out on change in morphological properties using optical microscope; change in chemical structure using FTIR; change in mass and volume by weight loss measurement; hardness changes using universal hardness tester; and change of chemical properties of the fuel blends using total acid number titration method. The test results showed that corrosion of copper was increased with the high concentration of ethanol in the blends.

The effect of acrylamide incorporation on the thermal and physical properties of denture resins

PURPOSEPolymethyl methacrylate (PMMA) is the most commonly used denture base material despite typically low in strength. The purpose of this study was to improve the physical properties of the PMMA based denture base resins (QC-20, Dentsply Ltd., Addlestone, UK; Stellon, AD International Ltd, Dentsply, Switzerland; Acron MC; GC Lab Technologies Inc., Alsip, Japan) by copolymerization mechanism.MATERIALS AND METHODSControl group specimens were prepared according to the manufacturer recommendations. In the copolymer groups; resins were prepared with 5%, 10%, 15% and 20% acrylamide (AAm) (Merck, Hohenbrunn, Germany) content according to the moleculer weight ratio, respectively. Chemical structure was characterized by a Bruker Vertex-70 Fourier transform infrared spectroscopy (FTIR) (Bruker Optics Inc., Ettlingen, Germany). Hardness was determined using an universal hardness tester (Struers Duramin, Struers A/S, Ballerup, Denmark) equipped with a Vickers diamond penetrator. The glass transition temperature (Tg) of control and copolymers were evaluated by Perkin Elmer Diamond DSC (Perkin Elmer, Massachusetts,USA). Statistical analyses were carried out using the statistical package SPSS for Windows, version 15.0 (SPSS, Chicago, IL, USA). The results were tested regarding the normality of distribution with the Shapiro Wilk test. Data were analyzed using ANOVA with post-hoc Tukey test (P<.01).RESULTSThe copolymer synthesis was confirmed by FTIR spectroscopy. Glass transition temperature of the copolymer groups were higher than the control groups of the resins. The 10%, 15% and 20% copolymer groups of Stellon presented significantly higher than the control group in terms of hardness. 15% and 20% copolymer groups of Acron MC showed significantly higher hardness values when compared to the control group of the resin. Acrylamide addition did not affect the hardness of the QC-20 resin significantly.CONCLUSIONWithin the limitation of this study, it can be concluded that copolymerization of PMMA with AAm increased the hardness value and glass transition temperature of PMMA denture base resins.

Responses of Austenitic Stainless Steel American Iron and Steel Institute (AISI) 303 (1.4305) Subjected to Different Environmental Conditions

Abstract In this paper some experimentally obtained results regarding mechanical properties at both low and elevated temperatures as well as short-time creep behavior of American Iron and Steel Institute (AISI) 303 (1.4305) austenitic stainless steel are presented. These results can be of importance in the design procedure for engineering components made of the considered material. The mentioned properties/strengths and short-time creep behavior were determined by uniaxial tests at different temperatures using materials testing machine. Impact energy was determined using the Charpy impact machine, while material hardness was determined using a universal hardness testing machine. For appropriate stress levels at selected temperatures, creep behavior modeling is displayed. Engineering fracture toughness assessment is based on experimentally obtained Charpy V-notch impact energy.

On elastic properties of steam-treated PM materials

The elastic and plastic properties of some ferrous base materials, before and after steam treatment, have been evaluated by means of a rather new testing method, named universal hardness testing. This test makes it possible to record continuously the instantly applied load and the indentation depth. The plotted curves enable to get indications on elastic and plastic deformation works, on sintering degree and on the Young's modulus as well. The elastic properties have been compared with the results achieved by means of strain gages in four-point bending tests. The influence of oxide layers on the elastic behaviour of steam-treated ferrous materials has been evaluated. The observation of tested areas at optical microscope helps to understand the features of oxide layers and their adhesion to the metallic matrix. The results may be useful to refine the design choice of powder metallurgy materials to be steam treated, in order to fulfil specific requirements of demanding applications, and to rate the correctness of the oxidation process.

UFG Microstructure Processing by ECAP from Double Electron-Beam Melted Rare Metal

High purity (99.99, wt %) niobium ingots were received by double electron beam melting technology. The specimens of pure metals with cast microstructure were processed using cold equal-channel angular pressing (ECAP) followed by a heat treatment at around 1080 °C in vacuum furnace for 2 h. Shear bands and microstructure evolution was studied in shear region at first pass and at next passes of ECAP. Microstructure processing characterization was performed using light optical and field emission scanning electron microscopy. Accompanied to microstructure the changes of mechanical properties were determined by micro- and universal hardness testing. The shear bands forming, evolution of large crystals to elongated laminar and dislocation fine-grain structures during processing was characterized and discussed in view of metal hardening-softening and viscoplastic behavior under subsequent hard cyclic straining.

Kalibrierung von Universalhärte-Prüfmaschinen, Eindringkörpern und Härtevergleichsplatten / The Calibration of Universal Hardness Testing Machines, Indenters and Hardness Reference Blocks

The testing and calibration procedures specified in the proposed standards for the test machines and hardness reference blocks for Universal hardness testing are compared with those specified in the current standards for the hardness testing of metallic materials. The calibration of the indenters used for Universal hardness testing, the measurement of the angles between their surfaces and the identification of possible defects on the surfaces of the indenter are all described. In addition, information is also given regarding possible methods of correcting the measurements obtained, the calibration requirements and newly developed types of hardness reference blocks (glass and advanced ceramics).

Fracture toughness and fracture surface energy of sintered uranium dioxide fuel pellets

The fracture properties of sintered uranium dioxide fuel pellets for thermal reactors play an important role in the formation of stress-induced cracks and fission-gas swelling during the reactor operation. The fracture toughness or critical stress intensity factor, K~c, and the fracture surface energy, 7~, (energy required to create unit area of fractured surface) are two parameters which can be used for predicting the mechanical behaviour of the fuel pellets. The reported values of fracture surface energy, 7s, for uranium dioxide pellets show a large variation (0.4 to 8 J m-Z) [1, 2]. An attempt was made to study the variation of Kit and 7s in sintered uranium dioxide pellets in the density (4) range of 9.86 to 10.41 g cm 3 using Vickers indentation technique, now commonly used for determination of fracture parameters of brittle and ceramic materials [3-6]. Half-penny shaped cracks are developed in ceramics and the crack length is related to the fracture parameters (K~c and 7s). A new parameter called fracture modulus Ef = (Klc):/7s was also calculated from the experimental data. Uranium dioxide pellets of different densities (90 to 95% theoretical density) were made from a single batch of green powder (ammonium diuranate route) by cold compaction and sintering at an average temperature of 1680°C for 5h. The geometric density of the pellets was measured as specified by ASTM standard C-766-79 for standard uranium dioxide pellets. The height of the pellets varied from 14 to 16mm and the average diameter of the pellets was 12.35 mm. Vickers hardness indentation was made on metallographically polished specimens using a universal hardness tester (Eseway, Type: DVRB-M) and the hardness was determined. A load of 294N was applied and the radial crack lengths in the four directions were measured using an optical microscope at x 400 immediately after the indentation. The ratio of the crack length (C) to half diagonal of indentation (a) made on the samples was greater than 2. Fig. la presents a photomicrograph of a specimen showing the cracks when viewed in an optical microscope. Fig. l b shows the crack tip ending when viewed through a scanning electron microscope. A minimum of four indentations were made on each of the samples and the average crack length (C) of each indentation and the average of hardness values were used for the calculation. Indentations resulting in chipping were discarded and fresh indentations were made. It was confirmed that there was no change in crack length as a function of time after the indentation was made. The overall average crack-length (C) and the volume fraction porosity (p) in the pellets were plotted (Fig. 2). The data were fitted to a straight line C(#m) = 1073 to 3990p, withacoefficientofregression r = 0.96. The fracture toughness, KIo, was calculated from the average crack length and the hardness using the equation Kjc = f(E/H)~/2(p/c3/2) (1)

Basic Studies of Plastic Working with Vibration : 3rd Report, Hardness Testing of Specimen with Induced Ultrasonic Vibration Using a Specially-Made Universal Hardness Tester

Basic Studies of Plastic Working with Vibration : 3rd Report, Hardness Testing of Specimen with Induced Ultrasonic Vibration Using a Specially-Made Universal Hardness Tester

A Magnetic Means of Monitoring Hardness Due to Heat Treatment in Steel Production

A number of researchers have reported work of varying degrees of success in determining mechanical hardness by magnetic means. The methods reported fall into the two categories of static testing (dc) or dynamic testing (ac). This paper describes a method of testing which is named the differential method. Since mechanical hardness is affected by many factors, several of which have no effect on magnetic properties, a universal hardness tester operating on magnetic properties would be impossible to develop; however, this paper describes how a magnetic means is employed to compare the hardness of a given material to a sample of the same material of known hardness. Test results are presented for carbon steel (AISI 1095) and alloy steel (AISI 4150).