Academic literature on the topic 'Hardness gradient'
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Journal articles on the topic "Hardness gradient"
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Chong, Arthur C. M., and David C. C. Lam. "Strain gradient plasticity effect in indentation hardness of polymers." Journal of Materials Research 14, no. 10 (October 1999): 4103–10. http://dx.doi.org/10.1557/jmr.1999.0554.
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Plasticity in material is typically described as a function of strain, but recent observations from torsion and indentation experiments in metals suggested that plasticity is also dependent on strain gradient. The effects of strain gradient on plastic deformation in thermosetting epoxy and polycarbonate thermoplastic were experimentally investigated by nanoindentation and atomic force microscopy in this study. Both thermosetting and thermoplastic polymers exhibited hardening as a result of imposed strain gradients. Strain gradient plasticity theory developed on the basis of a molecular kinking mechanism has predicted strain gradient hardening in polymers. Comparisons made between indentation data and theoretical predictions correlated well. This suggests that strain gradient plasticity in glassy polymers is determined by molecular kinking mechanisms.
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Lengauer, W., and K. Dreyer. "Tailoring hardness and toughness gradients in functional gradient hardmetals (FGHMs)." International Journal of Refractory Metals and Hard Materials 24, no. 1-2 (January 2006): 155–61. http://dx.doi.org/10.1016/j.ijrmhm.2005.03.008.
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KURODA, Yasunobu, Masaru KITAGAWA, Akishige SATO, Eiji KUSANO, and Akira KINBARA. "Adhesion and Hardness of Compositionally Gradient." SHINKU 41, no. 3 (1998): 111–14. http://dx.doi.org/10.3131/jvsj.41.111.
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Kunioshi, Clarice Terui, Olandir Vercino Correa, and Lalgudi Venkataraman Ramanathan. "Gradient Nickel – Alumina Composite Coatings." Materials Science Forum 530-531 (November 2006): 261–68. http://dx.doi.org/10.4028/www.scientific.net/msf.530-531.261.
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Particle reinforced metal matrix composite (MMC) coatings have been developed due to property combinations such as increased hardness, high creep/fatigue resistance as well as superior wear and oxidation resistance. MMC coatings can be produced by various techniques, which include powder metallurgy (plasma spray and HVOF processes), liquid metal processes and electrodeposition. This paper presents the development of the electrodeposition process to obtain nickel-alumina composites. The process conditions were optimized and based on these gradient nickel-alumina composites were prepared. Microstructural characterization and hardness determinations were carried out. The effect of process parameters on the amount and distribution of alumina particles as well as morphology of the deposits with and without alumina gradients are presented and discussed.
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Lam, David C. C., and Arthur C. M. Chong. "Indentation model and strain gradient plasticity law for glassy polymers." Journal of Materials Research 14, no. 9 (September 1999): 3784–88. http://dx.doi.org/10.1557/jmr.1999.0512.
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Plastic deformation of metals is generally a function of the strain. Recently, both phenomenological and dislocation-based strain gradient plasticity laws were proposed after strain gradients were experimentally found to affect the plastic deformation of the metal. A strain gradient plasticity law is developed on the basis of molecular theory of yield for glassy polymers. A strain gradient plasticity modulus with temperature and molecular dependence is proposed and related to indentation hardness. The physics of the strain gradient plasticity in glassy polymer is then discussed in relation to the modulus.
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Liang, Yi Long, Li Qiong Zhong, and Zhen Yan. "Influence of Shot Peening on the Surface Hardness of TC11 Titanium Alloy after High Cycle Fatigue Test." Materials Science Forum 849 (March 2016): 302–8. http://dx.doi.org/10.4028/www.scientific.net/msf.849.302.
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This paper studied the change of surface hardness after high-cycle fatigue (HCF) test of TC11 alloy with and without Shot Peening (WSP). The results showed that the surface hardness gradient of WSP specimens increased after R=-1 and R=0.1 HCF tests. It was found that the depth and magnitude of surface hardness gradient were related to the stress intensity and cyclic times of HCF, which increased with stress intensity; however, the surface hardness gradient of Shot Peening specimens after HCF maintained the same with that before HCF tests, the values of surface hardness varied slightly after HCF. According to analysis, the surface hardness change of WSP TC11 alloy is related to their surface integrity, which, during the cyclic loading, is due to the higher stress concentration generated on the original machining marks and the cyclic softening of surface layer generated by multi-directional stress.
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Tabushi, Kenichi, Hisashi Sato, and Yoshimi Watanabe. "Effect of Casting Condition on Density and Hardness Gradients of Al-Al2Cu Alloy FGM Fabricated by Centrifugal In Situ Method." Materials Science Forum 631-632 (October 2009): 449–54. http://dx.doi.org/10.4028/www.scientific.net/msf.631-632.449.
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Functionally graded material (FGM) is a combined material that has a component gradient from one material at one surface to another material at the opposite surface. As one of the fabrication processes of FGM, centrifugal in-situ method has been proposed. Centrifugal in-situ method is a casting that centrifugal force is applied during solidification to both the primary crystal and the matrix. In a previous study, the density and hardness gradients of Al-3mass%Cu FGM ring fabricated by centrifugal in-situ method have been investigated. According to the study, Cu concentration within the FGM ring monolithically increases towards the ring's inner position, and its density also increases toward inner region. This is because the density of the primary -Al crystal is larger than that of the molten Al-Cu alloy in the early stage of solidification. Based on this solidification process, it is considered that the casting condition and the initial Cu concentration of Al-Cu master alloy affect on the density and hardness gradients in the Al-Cu FGM ring. In this study, effects of the casting condition on the density and hardness gradients of Al-Al2Cu FGM rings fabricated by the centrifugal in-situ method were investigated. It was found that density gradient of the Al-Al2Cu FGM rings increases with increasing Cu concentration of Al-Cu master alloys. Also, processing temperature for Al-Cu master alloy can control density gradient of Al-Al2Cu FGM rings. These phenomena were explained by variation of the densities of primary -Al and the molten Al matrix during the solidification.
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M. Adinarayanappa, Somashekara, and Suryakumar Simhambhatla. "Twin-wire welding based additive manufacturing (TWAM): manufacture of functionally gradient objects." Rapid Prototyping Journal 23, no. 5 (August 22, 2017): 858–68. http://dx.doi.org/10.1108/rpj-09-2015-0126.
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Purpose Twin-wire welding-based additive manufacturing (TWAM) is a unique process which uses gas metal arc welding (GMAW)-based twin-wire weld-deposition to create functionally gradient materials (FGMs). Presented study aims to focus on creating metallic objects with a hardness gradient using GMAW of twin-wire weld deposition setup. Design/methodology/approach By using dissimilar filler wires in twin-wire weld-deposition, it is possible to create metallic objects with varying hardness. This is made possible by individually controlling the proportion of each filler wire used. ER70S-6 and ER110S-G are the two filler wires used for the study; the former has lower hardness than the latter. In the current study, methodology and various experiments carried out to identify the suitable process parameters at a given location for a desired variation of hardness have been presented. A predictive model for obtaining the wire speed of the filler wires required for a desired value of hardness was also created. Subsequently, sample parts with gradient in various directions have been fabricated. Findings For dissimilar twin-wire weld-deposition used here, it is observed that the resultant hardness is in the volumetric proportion of the hardness of the individual filler wires. This aids the fabrication of FGMs using arc based weld-deposition with localized control of hardness, achieved through the control of the ratio of wire speeds of the individual filler wires. Four sample parts were fabricated to demonstrate the concept of realizing FGMs through TWAM. The fabricated parts showed good match with the desired hardness variation. Research limitations/implications This paper successfully presents the capability of TWAM for creating gradient metallic objects with varying hardness. Although developed using ER70S-6 and ER110S-G filler wire combination, the methodology can be extended for other filler wire combinations too for creating FGMs Originality/value GMAW-based twin-wire welding for additive manufacturing is a novel process which uses dissimilar filler wires for creating FGMs. This paper describes methodology of the same followed by illustration of parts created with bi-directional hardness gradient.
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Nikolaev Nikolov, Georgi, Anders Noel Thomsen, and Morten Kristiansen. "Hardening in laser forming under the temperature gradient mechanism." IOP Conference Series: Materials Science and Engineering 1135, no. 1 (November 1, 2021): 012006. http://dx.doi.org/10.1088/1757-899x/1135/1/012006.
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Abstract Laser forming is a contactless thermal forming process that can be applied for both single and double-curved geometries. When it comes to prototyping and small batch production, laser forming has the potential to compete with conventional sheet-metal forming processes; however, an investigation of the relationship between process parameters, hardness distribution and the bend rate is lacking. This study examines the influence of using different sets of processing parameters on the bend rate and the hardness distribution. ANSI 304 stainless steel samples of 1 and 3 mm thickness are laser formed up to 90° with a bend radius equal to their thickness. A theoretical discussion of the material’s hardening kinetics is used to generalize the results. Micro-Vickers hardness test is used to measure the hardness distribution along the 3 mm samples to support the theoretical discussion. The results show that the bend rate increases when using different sets of process parameters; furthermore, the bend arc length has shown to have a significant influence over the bend rate. An increase of hardness is observed on the bottom side of the laser formed samples, indicating potential strain hardening.
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Zhao, Na Na, Yun Hua Xu, Ke Song, Liu Liu Shen, and V. E. Ovcharenko. "Study on TaC Reinforced Iron Matrix Surface Gradient Composites Produced In Situ." Materials Science Forum 848 (March 2016): 38–42. http://dx.doi.org/10.4028/www.scientific.net/msf.848.38.
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Tantalum carbide (TaC) gradient composites were fabricated via in-situ fabrication method from the tantalum plate and gray cast iron. The morphology, phase constituents, micro-hardness, and relative abrasion resistance of the composites were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-hardness tester and abrasive wear testing machine. The surface layer, which was ~160μm thick, was dense ceramic layer composed by ~90% submicron TaC particulates. The highest micro-hardness value of the dense ceramic layer was 13.84 GPa. In the sub-layer, the gradient distribution of TaC particulates reflected in the volume fraction decreased from 90% to 0%. While the micro-hardness value decreased from 10.81 GPa to 4.10 GPa. The metallurgical combination of the interface between the composites and matrix was perfect. The wear resistance of TaC reinforced iron matrix surface gradient composites increased significantly.
Dissertations / Theses on the topic "Hardness gradient"
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Golombieski, Jaqueline Ineu. "PARÂMETROS DA ÁGUA ALTERAM A EXCREÇÃO DE RESÍDUOS NITROGENADOS E DE FÓSFORO E O COMPORTAMENTO DE JUVENIS DE JUNDIÁ (Rhamdia quelen)." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/3282.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoIn the first study examined ammonia, urea, creatinine, protein, nitrite, nitrate, and phosphorus (P) excretion at different water hardness, humic acid or pH levels in silver catfish (Rhamdia quelen) juveniles. The fish were exposed to different levels of water hardness (4, 24, 50, or 100 mg CaCO3 L-1), humic acid (0, 2.5 or 5.0 mg L-1) or pH (5.0, 6.0, 7.0, 8.0, or 9.0) for 10 days. The overall measured nitrogen excretions were 88.1% (244 423 μmol kg-1 h-1) for ammonia, 10.9% (30 52 μmol kg-1 h-1) for creatinine, 0.02% (0.05 0.08 μmol kg-1 h-1) for protein, 0.001% (0.002 0.004 μmol kg-1 h-1) for urea, 0.5% (0.64 3.6 μmol kg-1 h-1) for nitrite, and 0.5% (0.0 6.9 μmol kg-1 h-1) for nitrate, and these proportions were not affected by water hardness or humic acid levels. The overall P excretion in R. quelen was 0.14 2.97 μmol kg-1 h-1. Ammonia excretion in R. quelen usually was significantly higher in the first 12 h after feeding, and no clear effect of water hardness, humic acid levels and pH on this daily pattern of ammonia excretion could be observed. Water hardness only affected the ammonia and P excretion of R. quelen juveniles in the initial and fifth days after transfer, respectively. The exposure of this species to humic acid decreased ammonia excretion after 10 days of exposure but did not affect P excretion. An increase in pH decreased ammonia and increased creatinine excretion but did not change P excretion in R. quelen. Therefore, when there is any change on humic acid levels or pH in the culture of this species nitrogenous compounds must be monitored because their excretion rates are variable. On the other hand, P excretion rates determined in the present study are applicable to a wide range of fish culture conditions. The aim of the second study was to determine the preferred pH in silver catfish Rhamdia quelen acclimated to different water hardness and the effect of shelters and infection by Ichthyophthirius multifiliis. Fish were acclimated for two weeks at different water hardness levels (4, 24, 50, or 100 mg CaCO3 L-1) and then transferred to a polyethylene tube with a pH gradient ranging from 3.5 to 11.7. The position of the fish in the pH gradient was observed at 1, 2, 4, 6, 8, 10, and 12 h after transference. Acclimation to different water hardness did not change pH preference of uninfected silver catfish (pH 7.30-7.83), and the presence of a shelter at the preferred pH or outside this preferred pH did not change the chosen pH range, either. Consequently silver catfish favored the acid-base regulation over shelter seeking tendency. Juveniles infected with I. multifiliis acclimated to water hardness of 24 mg CaCO3 L-1 preferred alkaline pH (9.08-9.79). This choice is not explained by the higher Na+ levels at alkaline pH compared to neutral pH because infected and uninfected fish choose the same waterborne Na+ levels in a Na+ gradient with the same pH.
No primeiro estudo analisou-se a excreção de amônia, ureia, creatinina, proteína, nitrito, nitrato e fósforo (P) em diferentes níveis de dureza da água, ácido húmico ou pH em juvenis de jundiás (Rhamdia quelen). Os peixes foram submetidos a diferentes níveis de dureza da água (4, 24, 50 ou 100 mg CaCO3 L-1), ácido húmico (0, 2,5 ou 5,0 mg L-1) ou pH (5,0, 6,0, 7,0, 8,0 ou 9,0) durante 10 dias. A excreção nitrogenada global medida foi de 88,1% (244 423 μmol kg-1 h-1) para amônia, 10,9% (30 52 μmol kg-1 h-1) para creatinina, 0,02% (0,05 0,08 μmol kg-1 h-1) para proteína, 0,001% (0,002 0,004 μmol kg-1 h-1) para ureia, 0,5% (0,64 3,6 μmol kg-1 h-1) para nitrito e 0,5% (0,0 6,9 μmol kg-1 h-1) para nitrato, e estas proporções não foram afetadas pelos níveis de dureza da água ou ácido húmico. A excreção global de P em R. quelen foi 0,14 2,97 μmol kg-1 h-1. A excreção de amônia em R. quelen, em geral, foi significativamente maior nas primeiras 12 horas após a alimentação e nenhum efeito claro dos níveis de dureza da água, ácido húmico e do pH pode ser observado sobre este padrão diário de excreção de amônia. A dureza da água afetou apenas a excreção de amônia e de P de juvenis de R. quelen no primeiro e quinto dias após a transferência, respectivamente. A exposição desta espécie ao ácido húmico diminuiu a excreção de amônia após 10 dias de exposição, mas não afetou a excreção de P. Um aumento no pH diminuiu a excreção de amônia e aumentou a excreção de creatinina, mas não alterou a excreção de P em R. quelen. Portanto, quando houver qualquer alteração nos níveis de ácido húmico ou pH na cultura desta espécie os compostos nitrogenados devem ser monitorados, pois suas taxas de excreção são variáveis. Por outro lado, as taxas de excreção de P determinados no presente estudo são aplicáveis a uma ampla gama de condições na cultura de peixes. O objetivo do segundo estudo foi determinar o pH preferido em jundiá Rhamdia quelen aclimatados a diferentes durezas da água e o efeito de abrigos e infecção por Ichthyophthirius multifiliis. Os peixes foram aclimatados durante duas semanas em diferentes níveis de dureza da água (4, 24, 50 ou 100 mg de CaCO3 L-1) e então transferidos para um tubo de polietileno com um gradiente de pH de 3,5 a 11,7. A posição do peixe no gradiente de pH foi observada 1, 2, 4, 6, 8, 10 e 12 h após a transferência. A aclimatação a diferentes durezas da água não afetou o pH preferido de jundiás não infectados (pH 7,30-7,83) e a presença de um abrigo no pH preferido ou fora deste pH também não alterou a faixa de pH preferida. Portanto, jundiás favorecem a regulação ácido-base em detrimento a uma tendência de procurar abrigo. Em juvenis infectados com I. multifiliis aclimatados à dureza da água de 24 mg de CaCO3 L-1 o pH preferido é alcalino (9,08-9,79). Esta escolha não é explicada pelos maiores níveis de Na+ em pH alcalino que em pH neutro porque peixes infectados e não infectados escolheram os mesmos níveis de Na+ na água em um gradiente de Na+ com o mesmo pH. Palavras-chave: piscicultura, gradiente de pH, ácido húmico, dureza da água
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Lin, Ching-Te 1967. "Microstructure, texture, and hardness gradients in aluminum diffusion-bonded to aluminum oxide." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50351.
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Martinez, Nelson Y. "Friction Stir Welding of Precipitation Strengthened Aluminum 7449 Alloys." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc862775/.
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The Al-Zn-Mg-Cu (7XXX series) alloys are amongst the strongest aluminum available. However, they are considered unweldable with conventional fusion techniques due to the negative effects that arise with conventional welding, including hydrogen porosity, hot cracking, and stress corrosion cracking. For this reason, friction stir welding has emerged as the preferred technique to weld 7XXX series alloys. Aluminum 7449 is one of the highest strength 7XXX series aluminum alloy. This is due to its higher zinc content, which leads to a higher volume fraction of eta' precipitates. It is typically used in a slight overaged condition since it exhibits better corrosion resistance. In this work, the welds of friction stir welded aluminum 7449 were studied extensively. Specific focus was placed in the heat affected zone (HAZ) and nugget. Thermocouples were used in the heat affected zone for three different depths to obtain thermal profiles as well as cooling/heating profiles. Vicker microhardness testing, transmission electron microscope (TEM), and differential scanning calorimeter (DSC) were used to characterize the welds. Two different tempers of the alloy were used, a low overaged temper and a high overaged temper. A thorough comparison of the two different tempers was done. It was found that highly overaged aluminum 7449 tempers show better properties for friction stir welding. A heat gradient along with a high conducting plate (Cu) used at the bottom of the run, resulted in welds with two separate microstructures in the nugget. Due to the microstructure at the bottom of the nugget, higher strength than the base metal is observed. Furthermore, the effects of natural aging and artificial aging were studied to understand re-precipitation. Large improvements in strength are observed after natural aging throughout the welds, including improvements in the HAZ.
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Walbrühl, Martin. "ICME guided development of cemented carbides with alternative binder systems." Doctoral thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214108.
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The development of alternative binder systems for tungsten carbide (WC) based cemented carbides has again become of relevance due to possible changes in EU regulations regarding the use of Cobalt (Co). A framework for the ICME (Integrated Computational Materials Engineering) based Materials Design is presented to accelerate the development of alternative binder systems. Part one of this work deals with the design of the cemented carbide composite hardness. It has been shown that the intrinsic binder hardness is comparable to a bulk metal alloy and that based on the binder solubilities a solid solution strengthening model developed in this work can be employed. Using a method presented in this work the non-equilibrium, frozen-in binder solubilities can be obtained. Both the design of the binder phase and composite hardness is presented based on a general Materials Design approach. Part two deals with a multiscale approach to model the surface gradient formation. The experimentally missing data on liquid binder diffusion has been calculated using AIMD (Ab initio Molecular Dynamics). The diffusion through the liquid cemented carbide binder has to be reduced to an effective diffusion value due to the solid carbides acting as obstacles that increase the diffusion path. The geometrical reduction of the diffusion has been investigated experimentally using the SIMS (secondary ion mass spectroscopy) technique in WC-Nickel-58Nickel diffusion couples. The geometrical contribution of the so-called labyrinth factor has been proven by the combination of the experiments and in conjunction with DICTRA simulations using the precise liquid AIMD diffusivities. Unfortunately, despite the improved kinetic database and the geometrical diffusion reduction, the surface gradient formation cannot be explained satisfactory in complex cemented carbide grades. Additional, but so far unidentified, contributions have to be considered to predict the surface gradient thickness.QC 20170919
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Chen, Yu, and 陳昱. "Extrusion Die Design for Tubes with Hardness Gradient." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/465d3a.
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碩士國立中山大學
機械與機電工程學系研究所
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This study is focused on the analysis and experiment of hot extrusion of magnesium alloy. Porthole dies with an inclination angle leads to non-uniform velocity distributions. This kind of design can make a gradient hardness tube that grain sizes at the material surface are smaller and harder than those at the center zone. Then it can have superior hardness on surface and good toughness in internal structure. This study aims to design porthole dies and mandrel with different inclination angles and use magnesium alloy AZ31 to conduct hot extrusion. Mainly in analyze extrusion load, normal plane and bonding plane’s effective strain distributions and material flow by the finite element method. Choose best parameter to manufacture a porthole die to conduct magnesium hot extrusion experiments. Microstructures of the materials are observed to understand the effects of the die inclination angles.
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Jhuang, Kai-Siang, and 莊凱翔. "Manufacture of Gradient Microstructure and Hardness Magnesium Alloy Materials by Rotating Compression Forming." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/29990490703175754991.
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碩士國立中山大學
機械與機電工程學系研究所
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This study aims to obtain experimentally gradient microstructure and hardness materials by rotating compression forming. Specimens of Magnesium alloy AZ31 with column shape are used. One end of the specimen is fixed and the other end is compressed and rotated. Different gradient microstructure and hardness distributions are obtained by changing the compression pressures (55, 60, 62,65 MPa), rotation speeds (10, 20, 30 rpm), rotation numbers (10, 20, 30, 40 revolutions) and forming temperatures (280°C, 320°C, 360°C). The relationships between the forming parameters and the gradient microstructure and hardness distributions are discussed. Larger grain size gradients were obtained with compression pressure of 60 MPa, rotating speed of 10 rpm and rotation number of 30 revolutions. The gradient of grain size is 2.1 μm/mm at r = 8 mm. The grain size at h = 0 mm and h = 10 mm on the longitudinal cross section are 4.1 μm and 25.4 μm, respectively, and the hardnesses are 72.9 and 59.8 HV, respectively. That is a higher hardness corresponds to a smaller grain size. In addition, finite element analyses of rotating compression forming are conducted. The effective strain is maximum at the middle of the contact surface of the specimen. From the comparisons of effective strain distribution and grain size distribution, it is known that a larger effective strain corresponds to a smaller grain size. The specimen maximum diameter after rotating compression increased from 20 mm to 29.17 mm at forming temperature from 280°C to 360°C under compression pressure of 60 MPa. That is the diameter extension of the specimen increases with the forming temperature.
Books on the topic "Hardness gradient"
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Induction Heat Treatment - Phase I - Technology to Produce Monolithic Gradient Hardness Steel Armor. Storming Media, 1996.
Find full textBook chapters on the topic "Hardness gradient"
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Gordon, G. A., and B. R. Tittmann. "Surface Elastic Wave Measurements for Determination of Steel Hardness Gradients." In Review of Progress in Quantitative Nondestructive Evaluation, 1597–604. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4613-0383-1_209.
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Rama Krishna, L., and G. Sundararajan. "Corrosion and Wear Protection through Micro Arc Oxidation Coatings in Aluminum and Its Alloys." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000207.
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This article presents the brief overview of fairly recent and eco-friendly micro arc oxidation (MAO) coating technology. The weight-cost-performance benefits in general raised the interest to utilize lightweight materials, especially the aluminum and its alloys. Despite numerous engineering advantages, the aluminum alloys themselves do not possess suitable tribology and corrosion resistance. Therefore, improvements in surface properties are essential to enable developing potential industrial applications. For improving wear and corrosion resistance of Al alloys, the most demanding surface properties are high hardness and chemical inertness. The technical and technological limitations associated with traditional anodizing and hard anodizing processes have been the strongest driving force behind the development of new MAO technology. While presenting the key technological elements associated with the MAO process, the basic mechanism of coating formation and its phase gradient nature is presented. Influence of various process parameters including the electrolyte composition has been discussed. The typical microstructural features and distribution of α- and γ-Al2O3 phases across the coating thickness as a key strategy to form dense coatings with required mechanical, tribological, and corrosion properties which are vital to meet potential application demands are briefly illustrated.
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Balinski, Michel, and Rida Laraki. "Common Language." In Majority Judgment. The MIT Press, 2011. http://dx.doi.org/10.7551/mitpress/9780262015134.003.0008.
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This chapter discusses the common languages of grading used by judges in wine, figure skating, diving, and other competitions, and their connections with scales and levels of measurement of competence and performance of a competitor or an aspiring politician. When common languages are used by experts such as juries of experts who class wines and professors grading students, they have absolute meanings. Examples of common languages, including the Mohs scale of mineral hardness, the Richter scale ML, and the Mankoski pain scale, along with four levels of measurement proposed by experimental psychologist S. S. Stevens, are also described.
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"Internal Oxidation." In Carburizing, 11–36. ASM International, 1999. http://dx.doi.org/10.31399/asm.tb.cmp.t66770011.
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Abstract Gas carburizing is known to promote internal oxidation in steel which can adversely affect certain properties. This chapter discusses the root of the problem and its effect on component lifetime and performance. It explains that gas-carburizing atmospheres contain water vapor and carbon dioxide, providing oxygen that reacts with alloying elements, particularly manganese, chromium, and silicon. It examines the composition and distribution of oxides produced in different steels and assesses the resulting composition gradients. It describes how these changes influence the development of high-temperature transformation products as well as microstructure, hardenability, and carbon content and properties such as fatigue and fracture behaviors, hardness, and wear resistance. It also explains how to manage internal oxidation through material design, process control, and other measures.
Conference papers on the topic "Hardness gradient"
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Payton, Lewis N. "Orthogonal Machining of Copper Alloy With a Hardness Gradient." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87524.
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An experimental and analytical investigation of the effects of hardness upon the classical orthogonal machining geometries was conducted using copper alloy with 12 levels of hardness as measured on the Brinell hardness scale. A real time data collection method permitted the collection of a large body of data for analysis. 720 experimental runs were analyzed. The experimental results were compared to thirteen geometrical models that have been formulated including Merchant’s and Piispanen’s independently derived orthogonal machining equations of the 1940’s. One model [1] was verified by the results of the experiment in copper when a regression study of the data was conducted. Their application of the minimum energy principle in deriving an expression for the shear front angle ψ, the onset of shear plane angle ϕ, and the tool face rake angle α, provided an accurate shear strain model that is well supported by the physical evidence. The resulting relationship: ψ=45°-φ+α2 is predictive. It correlates directly and strongly with the measured material hardness.
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Tibbits, Patrick A. "Elastic-Plastic Finite Element Stress Analysis of a Carburized Shaft With Spatial Gradient in Mechanical Properties." In ASME 2006 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/detc2006-99160.
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Low core hardness in a carburized bicycle pedal shaft allows yielding in the core region when the shaft carries a bending load. Quantitatively evaluating the effect of core hardness level requires simulation of the gradient in material properties from the high-hardness thin outer case to the low-hardness core. This study develops a scheme for generating a high-resolution finite element mesh near the outside diameter of the shaft, coupled with a method for specifying elastic-plastic stress-strain curves which vary with depth below the carburized surface. The method enables examination of the stress localization and intensification in the case when yielding occurs in the core. The results show the insufficiency of the linear elastic assumption, and explain failures of shafts with anomalously low core hardness.
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Jokinen, P. "HVOF-Sprayed Functionally Gradient Coating." In ITSC 1999, edited by E. Lugscheider and P. A. Kammer. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 1999. http://dx.doi.org/10.31399/asm.cp.itsc1999p0498.
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Abstract Thermally sprayed alumina coatings are widely used to improve wear resistance and heat insulation of steel and other metals. Usually these coatings have been made by plasma or flame spraying. HVOF-sprayed alumina coatings are more wear resistant and better bonded to the base material than with plasma and flame spraying. This paper presents a functionally gradient coating (FGC) of alumina and NiAl made with HVOF. It examines the microstructure, composition, hardness, adhesion, and resistance against thermal cycling of HVOF-sprayed FGC. The performance of FG-coating was proven with reference coatings made by plasma and flame spraying. Paper includes a German-language abstract.
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Sonoda, T., A. Watazu, J. Zhu, W. Shi, A. Kamiya, K. Kato, and T. Asahina. "Enhanced Industrial Applicability of Aluminum Alloy by Coating Technique With Titanium/Carbon Compositionally Gradient Film Using Magnetron Co-Sputtering." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39382.
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Coating of Aluminium alloy substrates with Ti/C compositionally gradient films was examined by magnetron sputtering, in order to improve not only the abrasion resistance of the alloy but also the adhesion between the deposited film and the alloy substrate with preserving the high hardness of such ceramic coatings. The Ti/C compositionally gradient films were deposited by co-sputtering of 2 sputter cathodes which had a pure titanium target and a titanium carbide target respectively, and their compositionally gradient was realized by varying continuously the electric power supplied to each sputter cathode. Under visual observation, the obtained Ti/C compositionally gradient films appeared to be uniform and adhesive. According to AES in-depth profiles, the carbon (C) concentration in the film gradually decreased in depth direction from trhe surface toward the substrate, confirming that a Ti/C compositionally gradient film had formed on the alloy substrate. On the basis of XRD, it was found that titanium carbide and α-titanium phases were formed in the gradient film. Furthermore the Vickers hardness of the film reached over Hv=2600. Therefore the abrasion resistance of the alloy and the adhesion of the hard coatings were expected to be improved by this method.
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Graja, Paul, and Norbert Meyendorf. "Determination of the Case Depth by Ultrasonic Backscatter of Case and Induction Hardened Steel With a Soft Hardness Gradient." In 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/qnde2021-74995.
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Abstract Heat treatment of steel is a common industrial procedure to alter the microstructure of a component locally. Often, only the surface of a component is heat-treated to a certain thickness such that it benefits from the high durability provided by a hardened microstructure, while the core microstructure remains ductile. The nondestructive determination of this thickness, the case-hardened depth, can be performed by evaluating the slight differences of the ultrasonic backscatter from the grains of changing size in different layers. However, current methods require a small transition zone from the hardened to the core microstructure for accurate results. In this work, a different approach for the determination of the case-hardened depth of components with a large transition zone is described. This approach utilizes ultrasonic frequencies about 20 MHz in contact technique. The ultrasound is introduced in an oblique setup with a wedge and is mode converted to the transverse mode. The statistical evaluation of the backscattering shows promising results for the determination of the case-hardened depth of hardened components with a smooth decrease of the hardness over the depth.
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Mjali, Kadephi V., Annelize Els-Botes, and Peter M. Mashinini. "The Effects of Laser and Mechanical Forming on the Hardness and Microstructural Layout of Commercially Pure Grade 2 Titanium Alloy Plates." In ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-2603.
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This paper illustrates the effects of the laser and mechanical forming on the hardness and microstructural distribution in commercially pure grade 2 Titanium alloy plates. The two processes were used to bend commercially pure grade 2 Titanium alloy plates to a similar radius also investigate if the laser forming process could replace the mechanical forming process in the future. The results from both processes are discussed in relation to the mechanical properties of the material. Observations from hardness testing indicate that the laser forming process results in increased hardness in all the samples evaluated, and on the other hand, the mechanical forming process did not influence hardness on the samples evaluated. There was no change in microstructure as a result of the mechanical forming process while the laser forming process had a major influence on the overall microstructure in samples evaluated. The size of the grains became larger with increases in thermal gradient and heat flux, causing changes to the overall mechanical properties of the material. The thermal heat generated has a profound influence on the grain structure and the hardness of Titanium. It is evident that the higher the thermal energy the higher is the hardness, but this only applies up to a power of 2.5kW. Afterwards, there is a reduction in hardness and an increase in grain size. The cooling rate of the plates has been proved to play a significant role in the resulting microstructure of Titanium alloys. The scanning speed plays a role in maintaining the surface temperatures of laser formed Titanium plates resulting in changes to both hardness and the microstructure. An increase in heat results in grain growth affecting the hardness of Titanium.
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Narayan, J., H. Wang, and A. Kvit. "Mechanical Properties of Novel Nanocrystalline Materials." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/md-24806.
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Abstract We have synthesized nanocrystalline thin films of Cu, Zn, TiN, and WC having uniform grain size in the range of 5 to 100 nm. This was accomplished by introducing a couple of manolayers of materials with high surface and have a weak interaction with the substrate. The hardness measurements of these well-characterized specimens with controlled microstructures show that hardness initially increases with decreasing grain size following the well-known Hall-Petch relationship (H∝d−½). However, there is a critical grain size below which the hardness decreases with decreasing grain size. The experimental evidence for this softening of nanocrystalline materials at very small grain sizes (referred as reverse Hall-Petch effect) is presented for the first time. Most of the plastic deformation in our model is envisioned to be due to a large number of small “sliding events” associated with grain boundary shear or grain boundary sliding. This grain-size dependence of hardness can be used to create functionally gradient materials for improved adhesion and wear among other improved properties.
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Kumpaty, Subha, Esther Akinlabi, Andrew Gray, Kevin Sivak, Mutiu Erinosho, and Sisa Pityana. "Study on Functionally Gradient Materials Under International Research Experiences for Undergraduates Program: US - South Africa Collaboration." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86288.
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This paper details the ongoing research conducted by Milwaukee School of Engineering senior undergraduate students in South Africa under the third year of the Research Experiences for Undergraduates grant EEC-1460183 sponsored by the National Science Foundation (Principal Investigator Dr. Kumpaty). Andrew Gray and Kevin Sivak conducted research in summer of 2017 under advisement of Dr. Kumpaty and his South African collaborators, Dr. Esther Akinlabi, Dr. Mutiu Erinosho and Dr. Sisa Pityana. They extended the work of Paoli (reported in IMECE2017-71037), with varying percent of Mo (0–15%) in the combination of Ti64-Mo deposited on Ti64 substrate at laser powers of 1500 and 1700 W for a select scan speed. Laser metal deposition was completed at the CSIR – National Laser Center, in Pretoria, South Africa and the material characterization was performed at the University of Johannesburg as in the previous year. Hardness decreased with addition of Mo. Lowest hardness was observed in 10% Mo layers, and greater percent of Mo led some agglomeration issues due to its melting temperature being much higher than that of Ti64. Corrosion tests were also attempted. Etching challenges were present as percent of Mo varied in the same sample. Results are directly applicable to biomedical industry in evaluating functionally graded materials. An alumnus of MSOE, Peter Spyres served as a liaison for our international REU participants as he engaged them during the weekends in a cultural immersion which otherwise would not have been possible. Gray and Sivak were able to spend July 4th at the U.S. Consulate in Pretoria. While the research collaborators have generously provided support, it is the care taken by Peter’s remarkable household, which enhanced the beneficial value of this international research enterprise.
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Hayashi, Takao, and Hideo Koguchi. "Contact Analysis Considering Surface Stress and Surface Elasticity: Increase of Indentation Hardness and Yield Stress." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-86220.
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An increase in indentation hardness with decreasing indentation depth has been observed in nanoindentation studies. It is known as the indentation size effect. The indentation modulus in Molecular Dynamics (MD) contact analysis is larger than that in theoretical analysis (Hertz contact theory). In this paper, elasto-plastic contact analysis for an anisotropic elastic half-space is performed using the surface Green’s function considering surface stress and surface elasticity. A contact analysis is conducted to investigate the effect of surface stress on yield stress and indentation hardness. The discrete convolution, fast Fourier transform method and conjugate gradient method are applied to the contact analysis. The hardening model of the elasto-perfect plastic law is used in this study. The yield stress is determined so that a contact area considering surface stress is agreed with the one ignoring surface stress. Then, the yield stress ignoring surface stress and surface elasticity fixed at a constant. It is found that the yield stress considering surface stress and surface elasticity increases with decreasing the indentation depth. The indentation hardness considering surface stress and surface elasticity is calculated using the determined yield stress. The effects of surface stress and surface elasticity on the indentation hardness and the yield stress is discussed.
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Song, Mingda, Huaixiang Cao, Xiaomin Shen, Xue Song, and Hao Zhang. "Stainless Steel Tank Failure Analysis and Nondestructive Evaluation." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28475.
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Penetrating cracks were found in the head straight section of a stainless steel tank before it was put into use. Penetrant testing, chemical analysis, metallographic analysis, X-ray residual stress test, crack surface scanning electron microscopy analysis and energy spectrum analysis was applied to study the cause of the cracks. The results showed that, chloride ion stress corrosion cracking was the reason of the failure. Metal magnetic memory detection and hardness testing were also used to evaluate the stress distribution of the head. The extreme points of the magnetic field gradient, hardness and tensile stress showed high coherence to the positions of the cracks. These results indicated that the metal magnetic memory method has good application prospects for the assessment of stainless steel deformation and stress state.