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Hardness Test (hardness + test)
Selected AbstractsApplication of a Depth Sensing Indentation Hardness Test to Evaluate the Mechanical Properties of Food MaterialsJOURNAL OF FOOD SCIENCE, Issue 5 2002N. ÖZkan ABSTRACT: A depth sensing indentation hardness test with an associated analysis is described as a convenient and simple technique for characterizing mechanical properties of food materials, such as hardness (H), elastic modulus (E), and an elasticity index (IE), which represents the ratio of elastic to total deformation. Storage modulus (G,) and loss tangent (tan§) of the selected model food material, a whey protein concentrate (WPC) gel, have also been determined using an oscillatory dynamic testing. Fractal dimension (D) and strain rate (or frequency) exponent (n) of the WPC gels were determined using both the indentation and dynamic test results. A good correlation between the results from the indentation and the dynamic tests was established. The effects of protein concentration, deformation rate, and chemical treatment on the mechanical properties of the WPC gels were clearly illustrated using the indentation test. [source] Enamel microhardness and bond strengths of self-etching primer adhesivesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2010Olabisi A. Adebayo Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self-etching primer adhesives. Eur J Oral Sci 2010; 118: 191,196. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (,SBS). Buccal and lingual mid-coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self-etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One-half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15-s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37º°C, the ,SBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min,1 until bond failure occurred. The mean ,SBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and ,SBS. The weights used were the inverse of the variance of the ,SBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the ,SBS. These results suggest that the ,SBS of the self-etch adhesive systems are not influenced by enamel surface microhardness. [source] The chemical and pharmaceutical equivalence of sulphadoxine/pyrimethamine tablets sold on the Tanzanian marketJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 6 2005Y. Hebron BPharm MSc Summary This study investigated chemical and pharmaceutical equivalence of 11 brands of pyrimethamine,sulphadoxine combination tablets sold on the Tanzanian market. Physical and chemical tests were performed for all the 11 brands. These tests included hardness test, friability, disintegration, dissolution, weight uniformity and assay for the active components. All the brands passed all the quality specifications of the United States Pharmacopoeia (USP) and British Pharmacopoeia (BP) in terms of hardness, friability, disintegration, assay and dissolution test, except for three brands that failed the hardness, disintegration or friability tests. One brand failed both the hardness and disintegration test; one failed the hardness test, whereas another one failed the friability test. The percentage content of pyrimethamine in the brands was in the range of 91·04,100·20% whereas that of sulphadoxine ranged from 91·53% to 99·88%. There were no major differences between the different brands of tablets containing pyrimethamine and sulphadoxine and the innovator product (Fansidar®), and all brands were physically and chemically equivalent. The results indicate that the post-market surveillance and registration process in Tanzania is having an impact on product quality as there was no brand which could be considered of very poor quality. Impurity profiling of all the locally produced brands indicated that they all contained the same sulphadoxine impurity, which was absent in the innovator product, suggesting a common source of generic raw material. [source] Application of a Depth Sensing Indentation Hardness Test to Evaluate the Mechanical Properties of Food MaterialsJOURNAL OF FOOD SCIENCE, Issue 5 2002N. ÖZkan ABSTRACT: A depth sensing indentation hardness test with an associated analysis is described as a convenient and simple technique for characterizing mechanical properties of food materials, such as hardness (H), elastic modulus (E), and an elasticity index (IE), which represents the ratio of elastic to total deformation. Storage modulus (G,) and loss tangent (tan§) of the selected model food material, a whey protein concentrate (WPC) gel, have also been determined using an oscillatory dynamic testing. Fractal dimension (D) and strain rate (or frequency) exponent (n) of the WPC gels were determined using both the indentation and dynamic test results. A good correlation between the results from the indentation and the dynamic tests was established. The effects of protein concentration, deformation rate, and chemical treatment on the mechanical properties of the WPC gels were clearly illustrated using the indentation test. [source] Effect of light source and time on the polymerization of resin cement through ceramic veneersJOURNAL OF PROSTHODONTICS, Issue 3 2001Flavio H. Rasetto Odont Purpose The purpose of this study was to evaluate the efficiency of 3 different light sources to polymerize a light curing resin cement beneath 3 types of porcelain veneer materials. Materials and Methods A conventional halogen light, a plasma arc light, and a high intensity halogen light were used to polymerize resin cement (Variolink II; Ivoclar North America Inc, Amherst, NY) through disks of veneer materials. Equal diameter and thickness disks of feldspathic porcelain (Ceramco II; Ceramco Inc, Burlington, NJ), pressable ceramic (IPS Empress; Ivoclar North America Inc), and aluminous porcelain (Vitadur Alpha; Vident Inc, Brea, CA) were used as an interface between the curing light tips and the light polymerized resin cement. The resin cement/veneer combinations were exposed to 4 different photopolymerization time protocols of 5 seconds, 10 seconds, 15 seconds, and 20 seconds for high intensity light units (Apollo 95E [Dental Medical Diagnostic Systems Inc, Westlake Village, CA] and Kreativ 2000 [Kreativ Inc, San Diego, CA]), and 20 seconds, 40 seconds, 60 seconds, and 80 seconds for conventional halogen light (Optilux; Demetron Research Inc, Danbury, CT). A surface hardness test (Knoop indenter) was used to determine the level of photopolymerization of the resin through the ceramic materials with each of the light sources. The data were analyzed by one-way analysis of variance and a post-hoc Scheffe test (p < .05). Results The data indicates that the Variolink II Knoop Hardness Number values vary with the light source, the veneer material, and the polymerization time. For a given light and veneer material, Knoop Hardness Number increases with longer polymerization times. The Kreativ light showed statistically significant differences (p < .05) between all test polymerization times. Use of this light required a polymerization time of greater than 20 seconds to reach maximum resin cement hardness. For samples polymerized with the Apollo light, there were statistically significant (p < .05) differences in surface hardness between samples polymerized at all times, except for the 15-second and 20-second times. Samples polymerized with the halogen light showed no statistically significant (p < .05) differences in hardness between polymerization times of 60 seconds and 80 seconds. Conclusions High intensity curing lights achieve adequate polymerization of resin cements through veneers in a markedly shorter time period than the conventional halogen light. However, the data in this report indicate that a minimum exposure time of 15 seconds with the Kreativ light and 10 seconds with the Apollo 95E light should be used to polymerize the Variolink II resin, regardless of the composition of the veneer. Conventional halogen lights required a correspondingly greater polymerization time of 60 seconds. [source] COMPARISON OF INSTRUMENTAL METHODS FOR MEASURING SEED HARDNESS OF FOOD-GRADE SOYBEANJOURNAL OF TEXTURE STUDIES, Issue 1 2008BO ZHANG ABSTRACT Breeding specialty soybeans for the soyfood market requires proper methodology in evaluation of seed quality attributes. In this study, efficient methods that could be potentially used for testing soybean seed hardness were developed by examining different instruments and seed parameters. Five food-grade soybean genotypes with different seed sizes were used to determine seed water-absorption capacity and hardness. Water absorption capacity was expressed by swell ratios for seed weight, seed dimension, and volume of water changes before and after soaking. Seed hardness test was conducted by a one-bite method using a food texture analyzer equipped with five different probes. The results showed that hardness testing by a 75 mm cylinder with 10 steamed seeds, single blade with five steamed seeds, and shear cell with 30 g steamed seeds produced dependable and consistent results with low coefficient of variance. However, shear cell may not be practical for early plant selection in a breeding program due to a relatively large sample requirement. Seed size can be used as indirect selection indicators for seed hardness. PRACTICAL APPLICATIONS Seed hardness is an important factor in determining soybean suitability for natto production. This study used two texture analyzers equipped with five different probes to test hardness of five soybean genotypes with different seed size. The methodologies for testing the seed texture of soybean have been established, which can help regulate the seed hardness testing for commercial production and provide consistent hardness references for natto breeding programs and the seed industry. [source] Beurteilung von Loten und Lötverbindungen unter dem Einfluss steigender Kupfergehalte in verunreinigten bleifreien LotbädernMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 1 2008B. Wielage Lead-free solders; phase selection; deep-etching; intermetallic compounds Abstract Zuverlässigkeit und Degradationsverhalten bleifreier Lote sind aufgrund von Widersprüchlichkeiten und notwendiger Problemlösungen nach wie vor Aspekte weiterer Untersuchungen. Die vorliegende Arbeit zeigt anhand von Phasenselektion der intermetallischen Phasen Ag3Sn und Cu6Sn5 sowie (Cu,Ni)6Sn5 und (Ni,Cu)3Sn4 morphologisch-mikrostrukturelle Zusammenhänge in Verbindung mit mechanischen Eigenschaften auf. Dazu wurden insbesondere das metallografische Tiefätzen und die instrumentierte Eindringprüfung genutzt. Die Lotlegierungen SnAg3,8CuX und SnCuXNi0,07 und deren Lötverbindungen wurden durch verschiedene Methoden komplex evaluiert. Es konnte nachgewiesen werden, dass das Zulegieren von Nickel als degradationsvermindernde Maßnahme des Kupfer-Leachings zur Versprödung der Legierung durch das Wachstum der Phase (Cu,Ni)6Sn5 führen kann. Evaluation of solders and solder joints processed in lead free solder baths with increasing copper content Reliability and degradation behavior of lead-free solders are due to contradictions and necessary problem solving remaining aspects of further investigations. This paper shows morphologic and microstructural relationships in conjunction with mechanical properties on the intermetallic phases Ag3Sn and Cu6Sn5 as well as (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4. In particular, the methods of metallographic deep-etching and the instrumented indentation hardness test were applied. The solders SnAg3,8CuX and SnCuXNi0,07 and their solder joints were comprehensively evaluated by various methods. It has been shown that alloying with nickel as a method of decreasing copper-leaching can induce embrittlement by growth of the (Cu,Ni)6Sn5 phase. [source] Messunsicherheit in der WerkstoffprüfungMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2007T. Polzin Dr.-Ing. Uncertainty; tensile test; charpy test; hardness test Abstract Bei der Werkstoffprüfung muss bei jedem Messwert die jeweilige Messunsicherheit angegeben werden. Aus der 1995 erschienenen GUM [1] wurde 2000 der Uncert Report für verschiedenen Messverfahren entwickelt und als Code of Practice (COP) [2,4]. veröffentlicht. Diese sollen in Zusammenhang mit den in den Normen empfohlenen Verfahren und der praktischen Umsetzung dargestellt werden. Measurement uncertainty in testing of materials For the testing of materials the respective uncertainty has to be indicated for each measured value. From the 1995 published GUM [1] 2000 the Uncert report for different measuring methods was developed and published as Code of Practice (COP) [2,4]. These are to be represented in connection with the procedures recommended in the standards and the practical implementation. [source] Preparation and properties of polyhedral oligomeric silsesquioxane,polysiloxane copolymersAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2010Takahiro Gunji Abstract All siloxane-type siloxane,polyhedral oligomeric silsesquioxane [(HSiO3/2)8, T8H] copolymers were synthesized by the dehydrogenative condensation of T8H with diphenylsilanediol, tetraphenyldisiloxane-1,3-diol or silanol-terminated polydimethylsiloxanes in the presence of diethylhydroxylamine followed by trimethylsilylation. Coating films were prepared by spin-coating of the coating solutions prepared from the dehydrogenative condensation products. The hardness of the coating films was evaluated by a pencil hardness test and was found to increase up to 6H with increases in the curing temperature. Silica gels were prepared by concentrating the coating solution following by pyrolysis. These silica gels showed a specific surface area 449 m2/g at 650 °C corresponding to the formation of a silica network in response to combustion of the phenyl groups. Copyright © 2009 John Wiley & Sons, Ltd. [source] About 200 years after Mohs , Nanoscratching LiB3O5CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2008P. Paufler Abstract Though simple scratch hardness tests after Mohs are still used today, the development of diamond nanoscratching equipment offers new possibilities to meet demands of modern nanotechnology. Preceding approaches to assign hardness values to materials are briefly reviewed, and scratch hardness is related to indentation hardness. Taking single-crystalline LiB3O5 as an example, the dependence of scratch morphology on the direction of scratching is demonstrated quantitatively. The coefficient of friction depends on normal load and varies between 0.25 and 0.37. Moreover, it is oscillating during scratching thus reflecting processes at nanoscale. Dislocation etch pits were observed due to scratching. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Defects formed within hardness indenter interaction zone in Al2O3,ZrO2 compositeJOURNAL OF MICROSCOPY, Issue 3 2006M. SZUTKOWSKA Summary The Al2O3,10 wt% ZrO2 composites were subjected to hardness tests using a Vickers diamond indenter up to 98.1 N. The microstructure observation using a transmission electron microscopy technique helped to identify up to four zones differing in defect level and character. The densest dislocation tangles, twins accumulation and frequent presence of three slip systems were found in regions that were in contact with the sides of the diamond pyramid. The second zone, characterized by two, or at least one, active slip systems, started at the bottom of the indentation mark and extended up to a distance comparable with the depth of indentation. In the third zone, with a thickness comparable to that above, only some ,-Al2O3 crystallites showed the presence of dislocations, whereas other crystallites were defect free. In the last zone the alumina crystals were left unaffected but the ZrO2 crystallites showed twinning characteristic of strain-induced transformation. [source] | |||||||||||||