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1
Niitsu, Y., and K. Ikegami. "Effect of Temperature Variation on Cyclic Elastic-Plastic Behavior of SUS 304 Stainless Steel." Journal of Pressure Vessel Technology 112, no. 2 (May 1, 1990): 152–57. http://dx.doi.org/10.1115/1.2928601.
Повний текст джерелаАнотація:
The cyclic elastic-plastic behavior of SUS 304 stainless steel was investigated experimentally under various temperatures and temperature-changing conditions. The specimens were cyclically loaded between fixed axial strain limits at constant temperatures in the range from room temperature to 600°C. The effects of the cyclic strain amplitude on the saturation property of cyclic hardening were obtained at various temperatures. The effects of temperature variations on the cyclic hardening were examined under the temperature conditions of changing between two different temperatures. From these experimental results, the effects of the temperature variation on the saturation properties were found under several temperature conditions. The three different hardening models accounting for these cyclic hardening properties were proposed. The experimental results were compared with the results calculated by those three cyclic hardening models.
2
Kirakevych, Iryna, Myroslav Sanytsky та Igor Margal. "Self-Сompacting Сoncretes, which hardening at different temperature conditions". Theory and Building Practice 2020, № 2 (20 листопада 2020): 107–12. http://dx.doi.org/10.23939/jtbp2020.02.107.
Повний текст джерелаАнотація:
In the article the features of reinforced concrete hardening at different temperature conditions and the current issues of preparation technology of Self-Сompacting Сoncretes (SCC) on the basis of superplasticized cementitious systems, combining knowledge of structure and modifying Portland cement compositions "Portland cement – active mineral additives – microfiller – superplasticizer – accelerator of hardening" to search for rational making provision of technical and building properties of concrete in the changing factors of its composition, technology and exploitation are shown. The physico-chemical peculіarities of hydration and hardening processes of superplasticized cementitious systems were established. The problem of obtaining Self-Compacting mixtures and Rapid-Hardening Concretes on their basis by the direct structure formation of cementitious matrix was solves. The optimization of Self-Compacting Concretes composition on the base of superplasticized cementitious systems with high early strength was carried out. The quality parameters of developed concretes were investigated and the effectiveness of their using in different temperature conditions was shown. The results of the studies found that the use of the superplasticized cementitious systems allows to influence on technological properties and kinetics of structure formation and create concrete structure with improved construction and technical properties at a different temperature conditions. Technological solutions designing of superplasticized cementitious systems that solves the problem of obtaining the Self-Сompacting Сoncretes (SCC) on their basis with using non-vibration technology are established. This creates an opportunity allows to solve the problem of obtaining for enabling early loading, reducing the production cycle, increasing turnover and formwork acceleration of monolithic buildings and structures at different temperature conditions.
3
Rusynko, A. K. "Creep with temperature hardening." Materials Science 33, no. 6 (November 1997): 813–17. http://dx.doi.org/10.1007/bf02355560.
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4
Ohno, Nobutada, Ryohei Yamamoto, and Dai Okumura. "Thermo-Mechanical Cyclic Plastic Behavior of 304 Stainless Steel at Large Temperature Ranges." Key Engineering Materials 725 (December 2016): 275–80. http://dx.doi.org/10.4028/www.scientific.net/kem.725.275.
Повний текст джерелаАнотація:
Thermo-mechanical cyclic experiments on 304 stainless steel were performed at several temperature ranges which had maximum temperatures ranging from 350°C to 1000°C and a minimum temperature of 150 °C. Related isothermal cyclic experiments were also performed. Temperature-history dependent cyclic hardening significantly occurred under thermo-mechanical cyclic loading with maximum temperatures around 600°C, whereas almost no cyclic hardening was observed when the maximum temperature was 1000°C. The observed thermo-mechanical cyclic plastic behavior in the saturated state of cyclic hardening was then simulated using a cyclic viscoplastic constitutive model, leading to the following findings. It was difficult to predict the saturated thermo-mechanical cyclic behavior using only the isothermal cyclic experimental data. The saturated thermo-mechanical cyclic behavior was simulated well by introducing a cyclic hardening parameter depending on the maximum temperature. This means that the cyclic hardening parameter should not change with temperature but depend on the maximum temperature in the saturated state of cyclic hardening under thermo-mechanical cyclic loading.
5
Bauer, A., and K. Schreiner. "Dimensional Stability of Low Temperature Surface Hardened Stainless Steel Components*." HTM Journal of Heat Treatment and Materials 77, no. 1 (December 24, 2021): 16–28. http://dx.doi.org/10.1515/htm-2021-0022.
Повний текст джерелаАнотація:
Abstract Stainless steels are commonly used for high precision components, which often are exposed to corrosive media. However, their inferior tribological behaviour restrict the use of these materials in many technical applications. Thermochemical surface hardening is one way to overcome these weaknesses. Solution nitriding in the austenitic range above 1000 °C is mainly used for hardening martensitic and ferritic stainless grades. In austenitic and duplex stainless grades, however, the hardening effect is limited. Additionally, the high process temperatures combined with a necessary rapid cooling may lead to non-desired dimensional changes. Low temperature surface hardening processing below 500 °C here offers interesting alternatives for increasing the wear properties, while maintaining the corrosion resistance. This paper demonstrates the influence of high and low process temperatures of thermochemical surface hardening treatments on the tight dimensional tolerances of a rotationally symmetrical precision component made from cold worked AISI 304. Based on these results, current and new industrial applications, which benefit from low temperature surface hardening, will be discussed.
6
Lloyd, David J. "The Work Hardening of some Commercial Al Alloys." Materials Science Forum 519-521 (July 2006): 55–62. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.55.
Повний текст джерелаАнотація:
The work hardening of Al alloys is very important in regards to their formability and their deformation behavior in service. The majority of the work in the literature has considered relatively pure materials, and has tended to concentrate on room temperature and elevated temperature behavior. In Al alloys there is interest in work hardening at lower temperatures since they are quite restricted in terms of the elevated temperatures at which they can be used. In this paper the work hardening of commercial 1000, 3000 and 5000 alloys have been investigated from room temperature down to 85°K. The work hardening has been analyzed using the Voce approach, and it is shown that this enables the work hardening of the different alloys to be related to their basic physical metallurgy.
7
Geissler, E., and H. W. Bergmann. "Temperature Controlled Laser Transformation Hardening." Key Engineering Materials 46-47 (January 1991): 121–32. http://dx.doi.org/10.4028/www.scientific.net/kem.46-47.121.
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8
Li, L., X. J. Zhu, L. Zhang, and F. Z. Tian. "Damage constitutive model of pure copper at different annealing temperatures." Journal of Physics: Conference Series 2045, no. 1 (October 1, 2021): 012013. http://dx.doi.org/10.1088/1742-6596/2045/1/012013.
Повний текст джерелаАнотація:
Abstract Aiming at the problem of damage evolution of pure copper during the plastic deformation, the normalized shape factor is introduced based on the RO model (Ramberg-Osgood model). The mesoscopic damage constitutive model of pure copper at different annealing temperatures is established and the tensile deformation of industrial pure copper at different annealing temperatures is analyzed. The results show that the error between the calculated value and the experimental value of the damage constitutive model, based on normalized shape factor, at different annealing temperatures, is less than 10%. The model can effectively reveal the tensile damage evolution behavior of industrial pure copper and accurately predict the plastic tensile flow stress of industrial pure copper at different annealing temperatures. The hardening coefficient and hardening exponent in the model are closely related to the annealing temperature of the material. The annealing temperature has little effect on the hardening exponent and has a significant effect on the hardening coefficient and the hardening coefficient decreases with the increase in annealing temperature.
9
Zhu, Jun, and Yin Zhong Shen. "Irradiation Hardening in Ferritic/Martensitic Steel P92 during Ar-Ions Irradiation at Elevated Temperature." Applied Mechanics and Materials 378 (August 2013): 289–92. http://dx.doi.org/10.4028/www.scientific.net/amm.378.289.
Повний текст джерелаАнотація:
The irradiation hardening behavior in a commercial ferritic/martensitic steel P92 has been investigated through 250KeV Ar-ions irradiations to a dose of 10dpa at 473, 673 and 973K combined with nanoindentation techniques. The results show that irradiation-induced hardening was observed at the all irradiation temperatures. There appear to have no previous reports of the irradiation-induced hardening at the temperature higher than 873K in ferritic/martensitic steels. Irradiation-induced hardening at elevated temperature of 973K has been found, for the first time, in ferritic/martensitic steel. The irradiation-induced hardening at 973K in the ferritic/martensitic steel P92 may be ascribed to the defects in the steel generated by Ar-ions irradiation.
10
Odlum, K. D., and T. J. Blake. "A comparison of analytical approaches for assessing freezing damage in black spruce using electrolyte leakage methods." Canadian Journal of Botany 74, no. 6 (June 1, 1996): 952–58. http://dx.doi.org/10.1139/b96-118.
Повний текст джерелаАнотація:
To compare different methods of quantifying shoot frost damage during controlled plant freezing tests, frost hardening of black spruce (Picea mariana (Mill.) BSP) seedlings exposed to three temperature hardening regimes over 16 weeks was assessed using electrolyte leakage and intact seedling methods. Electrolyte leakage was expressed as index of injury and was quantified either as the temperature needed to induce an index of injury of 5% (DT5) or as the critical temperature (CT), the mildest temperature at which damage was first detected statistically. Damage to intact shoots was expressed as percent shoot browning and was quantified as the temperature at which 50% of needle tissue on the shoots was damaged (sLT50) or as the temperature at which 50% of terminal buds were killed (bLT50). Seedling response to hardening temperature varied, depending on the method used to quantify frost hardiness. When expressed as critical temperature, hardening continued over the 16 weeks at a constant rate with no differences detected between treatments. Intact seedling shoot damage, sLT50 and bLT50, described a hardening process in which there was a large initial increase in hardening in the first 8 weeks, with less hardening occurring during the subsequent 8 weeks. Also, significant temperature effects were detected, with the greatest hardening occurring in a cool temperature (4 °C), the least in a warm temperature (20 °C), and an intermediate amount in a moderate temperature (10 °C). When quantified as DT5, the pattern of hardening was somewhat intermediate to the other two. Methods of determining frost hardiness were highly correlated, with the strongest correlation being between sLT50 and bLT50 (r2 = 0.903). Both electrolyte leakage methods, DT5 and CT, were linearly related to one another (r2 = 0.666) and were more sensitive than the intact seedling methods, since they both detected damage at warmer temperatures. DT5 was better correlated to intact measures of hardiness than was CT. Keywords: black spruce, index of injury, frost hardiness, critical temperature, damaging temperature, LT50.
11
Xiao, Bing, Hong Hua Su, Shu Sheng Li, and Hong Jun Xu. "Research on Grind-Hardening Temperature and Cooling Rate of 48MnV Microalloyed Steel." Key Engineering Materials 359-360 (November 2007): 148–52. http://dx.doi.org/10.4028/www.scientific.net/kem.359-360.148.
Повний текст джерелаАнотація:
The temperature, time and cooling rate are key factors in the hardening process using the grinding heat instead of the high frequency induction heat source. Thus, this paper established the mathematical model estimating the grind-hardening temperature, experimentally determined the grinding temperature and the cooling rate of different grinding parameters for 48MnV microalloyed steel using the conventional aluminum grinding wheel on a surface grinder, and investigated the grind-hardening effects and the forming mechanism of grind-hardening layer. The results show that the estimating temperatures are comparatively close to the measuring ones and hence the model could be utilized to optimize the processing parameters, and the satisfactory grind-hardening temperature and cooling rate could be achieved under the optimized processing parameters. The microstructure of the grind-hardening layer, the fine needlelike martensite in the entirely hardened zone, the martensite and ferrite in the transitional region is similar to that acquired through the high frequency induction technique. Especially, the average hardness of the entirely hardened zone is 740HV and the depth of the hardened layer is adjacent to 1.5mm, which indicate that the grind-hardening effects are very excellent. Different from the forming mechanism of the high frequency induction hardened layer, higher grind-hardening temperature is needed to compensate shorter time austenitization, and because of thermo-mechanical loading induced during grinding, from surface to inside, the morphology of martensite changes from fine to thicker, then to finer, other than from thick to finer.
12
James, L. A. "Ramberg-Osgood Strain-Hardening Characterization of an ASTM A302-B Steel." Journal of Pressure Vessel Technology 117, no. 4 (November 1, 1995): 341–45. http://dx.doi.org/10.1115/1.2842133.
Повний текст джерелаАнотація:
The Ramberg-Osgood strain-hardening exponents and coefficients are characterized for an unirradiated ASTM A302-B steel over a wide range of temperatures from −129 to 260°C. The strain-hardening exponent increases only slightly with temperature over this range, while the coefficient decreases with increasing temperature. Tensile specimens irradiated to 0.002, 0.029, and 0.046 dpa exhibited significant increases in the strain-hardening exponent with increasing neutron irradiation level.
13
Kang, Dae H., D. W. Kim, S. Kim, Geun Tae Bae, K. H. Kim, and Nack J. Kim. "Room Temperature Formability of Mg Alloys." Materials Science Forum 618-619 (April 2009): 463–66. http://dx.doi.org/10.4028/www.scientific.net/msf.618-619.463.
Повний текст джерелаАнотація:
Room temperature formability of twin-roll cast Mg alloys has been investigated and correlated with their work hardening behavior. Tensile properties of these alloys were measured and their work hardening behaviour was analysed by using constitutive equations. Room temperature formability of the alloys was evaluated by the limiting dome height (LDH) value, obtained by the Erichsen cupping test. It shows that there is a linear relationship between LDH value and the inverse of yield ratio, which is a function of work hardening exponents. An increase in grain size increases work hardening exponent and concurrently increases LDH.
14
Samuel, E. Isaac, Neeta Paulose, M. Nandagopal, S. Panneer Selvi, S. N. Narendra Babu, and S. L. Mannan. "Tensile Deformation and Work Hardening Behaviour of AISI 431 Martensitic Stainless Steel at Elevated Temperatures." High Temperature Materials and Processes 38, no. 2019 (December 19, 2019): 916–26. http://dx.doi.org/10.1515/htmp-2019-0028.
Повний текст джерелаАнотація:
AbstractTensile deformation and fracture behaviour of AISI 431 martensitic stainless steel, over the temperature range of 300-823 K, has been examined. Yield and ultimate tensile strength values decreased gradually from room temperature to intermediate temperatures, followed by a rapid decrease at high temperatures. At the intermediate temperatures (523-673 K), the steel exhibited jerky/serrated flow and anomalous variations in terms of a plateau in flow stress/strength and work hardening parameters and minima in ductility. These manifestations were identified to be the signatures of dynamic strain ageing, operating at these temperatures. At high temperatures, a rapid decrease in flow stress/strength values and increase in ductility with increasing temperature indicated the dominance of dynamic recovery. The fracture remained transgranular ductile at all temperatures. Work hardening relations that best described the flow behaviour of AISI 431 steel were identified. Variations of the work hardening parameters with temperature were consistent with the variations exhibited by strength and ductility values.
15
Ohashi, Y., M. Kawai, and T. Kaito. "Inelastic Behavior of Type 316 Stainless Steel Under Multiaxial Nonproportional Cyclic Stressings at Elevated Temperature." Journal of Engineering Materials and Technology 107, no. 2 (April 1, 1985): 101–9. http://dx.doi.org/10.1115/1.3225781.
Повний текст джерелаАнотація:
The stress-range and path-shape dependencies of multiaxial nonproportional cyclic hardening were studied for annealed type 316 stainless steel at 600°C by means of stress controlled tests. Cyclic experiments along circular stress paths with constant effective stresses in the axial-torsional stress plane were first performed. The significant cyclic hardening and its stress-range dependency observed for the circular stress cyclings were quantitatively shown in reference to the cyclic stress-strain curves resulted from uniaxial stress cyclings. Then, to discuss the effect of path-shape, the cyclic tests along square stress paths inscribed by the above circular paths, as well as the tests where uniaxial cyclings and torsional ones were alternated, were also carried out. As a result of these tests, the cyclic hardenings for square paths were found to be almost equivalent to those for their circumscribed circular paths. The other type of stress cyclings caused almost the same amount of cyclic hardenings as those for the circular cyclings of the identical stress-ranges.
16
Rusanescu, Carmen Otilia, and Marin Rusanescu. "Process Design in the Manufacturing of Pipes for Chemical and Petrochemical Industry." Revista de Chimie 69, no. 9 (October 15, 2018): 2357–60. http://dx.doi.org/10.37358/rc.18.9.6533.
Повний текст джерелаАнотація:
In the present study the influence of vanadium microalloy on kinetics of transformation in medium carbon steel is studied. In order to choose the thermal treatment temperatures at optimal values, the steel transformation points were determined by dilatometric analysis. The bainitic transformation point was obtained under fast cooling conditions. The industrial experiments on the hardening and tempered of steel were performed in five variants of the oil hardening and reversing treatment, with austenitizing temperatures for hardening and the tempered temperature. The steel quality was determined, the influence of the temperature on the microalloyed steel structure with vanadium was highlighted. The mechanical characteristics of the pipes after the thermal hardening and tempering were analyzed after the traction test and the shock break. Electron microscopy analysis on extraction replicas revealed aspects of precipitation, globular constituent after return is finely and uniformly distributed, austenitization at lower temperature, resulted in a finer austenitic grain [20]. The finer structure obtained after hardening resulted in heat treatment to return to precipitation of fine and uniformly distributed carbides. It has been found that the influence on bainitic transformation depends on temperature; the steel structure after the quenching and tempering treatment was analyzed by optical and electronic microscopy. The development of welding consumables is permanently challenged with matching the increasing strength and toughness of thermomechanically treated or hardening and tempered steels.
17
Mirzaev, D. A., and A. N. Makovetskii. "Intercritical Quench Hardening of Structural Pipeline Steels." Materials Science Forum 843 (February 2016): 248–52. http://dx.doi.org/10.4028/www.scientific.net/msf.843.248.
Повний текст джерелаАнотація:
The paper considers the effect of low-carbon pipeline steels initial condition on their mechanical properties and structure after quench hardening at different temperatures in the intercritical temperature range Ac1–Ac3 (ITR) followed by tempering at 600 °C. If the prior heat treatment is annealing or normalizing , which produces the ferrite-pearlite structure, then quenching from temperatures just above Ac1 causes very strong embrittlement due to the formation of a high-carbon austenite film at ferrite/pearlite boundaries. Increasing quenching temperature in the intercritical range increases impact toughness and ductile fracture fraction for both types of prior treatment, though normalizing provides higher impact toughness than annealing. On the contrary, if the prior heat treatment is quench hardening, then the highest impact toughness is observed when the second quenching temperature lies a little above Ac1. Impact toughness and ductile fraction for preliminarily quenched samples gradually decreases along with the increase in austenitization temperature in the intercritical range.
18
Venkatesh, Vasisht, and H. J. Rack. "Elevated temperature hardening of INCONEL 690." Mechanics of Materials 30, no. 1 (September 1998): 69–81. http://dx.doi.org/10.1016/s0167-6636(98)00020-9.
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19
Petrenec, Martin, Karel Obrtlík, Jaroslav Polák, and Jiří Man. "Effect of Temperature on the Low Cycle Fatigue of Cast Inconel 792-5A." Key Engineering Materials 345-346 (August 2007): 383–86. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.383.
Повний текст джерелаАнотація:
Cyclic strain control tests have been performed on cylindrical specimens of cast polycrystalline Inconel 792-5A superalloy at 23, 500, 700 and 800 °C in laboratory atmosphere to study the effect of temperature on the fatigue behavior. Cyclic hardening-softening curves and fatigue life curves were measured. Scanning electron microscopy was used to investigate the surface relief. Low amplitude straining was characterized by saturation of the stress amplitude. In room temperature high amplitude straining cyclic hardening was followed by marked saturation. Pronounced continuous hardening until failure was observed at 500 °C. Initial cyclic hardening was followed by softening at 800 °C. A systematic shift of the Manson-Coffin and of the Basquin curves to lower fatigue lives was found when temperature was increased. Fatigue cracks were observed to initiate from surface slip markings at all temperatures.
20
Tesar, J., P. Vacikova, O. Soukup, and S. Houdkova. "Infrared Camera Analysis of Laser Hardening." Advances in Optical Technologies 2012 (December 9, 2012): 1–6. http://dx.doi.org/10.1155/2012/593893.
Повний текст джерелаАнотація:
The improvement of surface properties such as laser hardening becomes very important in present manufacturing. Resulting laser hardening depth and surface hardness can be affected by changes in optical properties of material surface, that is, by absorptivity that gives the ratio between absorbed energy and incident laser energy. The surface changes on tested sample of steel block were made by engraving laser with different scanning velocity and repetition frequency. During the laser hardening the process was observed by infrared (IR) camera system that measures infrared radiation from the heated sample and depicts it in a form of temperature field. The images from the IR camera of the sample are shown, and maximal temperatures of all engraved areas are evaluated and compared. The surface hardness was measured, and the hardening depth was estimated from the measured hardness profile in the sample cross-section. The correlation between reached temperature, surface hardness, and hardening depth is shown. The highest and the lowest temperatures correspond to the lowest/highest hardness and the highest/lowest hardening depth.
21
Wang, X. B. "Peak and Average Temperatures in Adiabatic Shear Band for Thermo-Viscoplastic Metal Materials." Key Engineering Materials 345-346 (August 2007): 133–36. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.133.
Повний текст джерелаАнотація:
Gradient-dependent plasticity considering the microstructural effect is introduced into Johnson-Cook model to calculate the nonuniform temperature distribution in adiabatic shear band (ASB) and the evolutions of average and peak temperatures in ASB. Effects of initial static yield stress, strain-hardening coefficient, strain-hardening exponent, strain-rate parameter and thermal-softening parameter are numerically investigated. The calculated peak temperature in ASB considering both the plastic work and the microstructural effect is always greater than the average temperature calculated only using the plastic work. For much lower flow shear stress, the peak temperature approaches two times the average temperature. The occurrence of phase transformation in ASB is easier in metal material with higher initial static yield stress, strain-hardening coefficient, strain-rate parameter and thermal-softening parameter. At much lower flow shear stress or much higher average plastic shear strain, the phase transformation occurs more easily in material with a lower strain-hardening exponent. Traditional elastoplastic theory without the microstructural effect underestimates the peak temperature in ASB so that the experimentally observed phase transformations cannot be explained.
22
Juijerm, P., I. Altenberger, U. Noster, and Berthold Scholtes. "Residual Stress Relaxation and Cyclic Deformation Behavior of Deep Rolled AlMg4.5Mn (AA5083) at Elevated Temperatures." Materials Science Forum 490-491 (July 2005): 436–41. http://dx.doi.org/10.4028/www.scientific.net/msf.490-491.436.
Повний текст джерелаАнотація:
The cyclic deformation behavior of deep rolled and polished aluminium wrought alloy AlMg4,5Mn in the temperature range 20-300°C has been investigated. Results of quasistatic tension and compression tests of untreated specimens in the temperature range 20-300°C are presented. To characterize the fatigue behavior for stress-controlled tests as a function of test temperature, s-n curves, cyclic deformations curves and mean strains as a function of number of cycles are given. The residual stress- and work hardening states near the surface of deep rolled aluminium alloy AlMg4.5Mn before and after fatigue tests were investigated by X-ray diffraction methods. The investigated AlMn4.5Mn aluminium alloy shows cyclic hardening until fracture at all stress amplitudes in stress-controlled fatigue tests at 25-150°C. With increasing temperature the deformation behavior shifts from cyclic hardening to cyclic softening. Below a certain stress amplitude at a given temperature deep rolling led to a reduction of the plastic strain amplitude as compared to the untreated state through cyclically stable near-surface work hardening as indicated by stable FWHM-values. This reduction in plastic strain amplitude is associated with enhanced fatigue lives. The effectiveness of deep rolling is governed by the cyclic and thermal stability of nearsurface work hardening rather than macroscopic compressive residual stresses. Since nearsurface work hardening is known to retard crack initiation, deep rolling is also effective in temperature- and stress ranges where macroscopic compressive residual stresses have relaxed almost completely, but where near-surface work hardening prevails. Above certain stress amplitudes and temperatures, deep rolling has no beneficial effect on the fatigue behavior of AlMg4.5Mn. This is a consequence of instable near-surface microstructures, especially instable near-surface work hardening.
23
Obrtlík, Karel, Alice Chlupová, Martin Petrenec, and Jaroslav Polák. "Low Cycle Fatigue of Cast Superalloy Inconel 738LC at High Temperature." Key Engineering Materials 385-387 (July 2008): 581–84. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.581.
Повний текст джерелаАнотація:
Cylindrical specimens of cast polycrystalline nickel base superalloy Inconel 738LC were cyclically strained under total strain control at 23 and 800 °C to fracture. Cyclic hardening/softening curves, cyclic stress-strain curves, and fatigue life curves were obtained at both temperatures. Surface relief was studied in specimens fatigued to failure using scanning electron microscopy. Cyclic hardening/softening behaviour depends both on temperature and strain amplitude. Low amplitude straining was characterized by saturation of the stress amplitude. In high amplitude straining a pronounced hardening was found which was followed by saturation at room temperature and by cyclic softening at 800 °C. The cyclic stress-strain curves can be fitted by power law. They are shifted to lower stresses with increasing temperature. Fatigue life curves can be approximated by the Manson- Coffin and Basquin laws. The Manson-Coffin and Basquin curves are shifted to lower lives with increasing temperature. Slip markings were detected on specimen surface at all test temperatures. When temperature grows the density of slip markings is reduced.
24
Shveikin, V. P. "Thermomechanical Hardening of Steels." Solid State Phenomena 284 (October 2018): 507–12. http://dx.doi.org/10.4028/www.scientific.net/ssp.284.507.
Повний текст джерелаАнотація:
The methods of the hot working of metals by pressure are discussed. The features of the hot plastic deformation of the metal which determine the formation of the structure and properties of steel are noted. The definition of thermomechanical treatment is given. The definitions of a variety of thermomechanical and high-temperature thermomechanical processes are given. The features of the thermomechanical treatment of steels toughened to martensite are discussed. The temperature, deformation-velocity and time parameters of high-temperature thermomechanical processing are given. Their influence on the structure and properties of steels is analyzed
25
Lee, Keum Oh, Sam Son Yoon, Soon Bok Lee, and Bum Shin Kim. "Low Cycle Fatigue Behavior of 429EM Ferritic Stainless Steel at Elevated Temperatures." Key Engineering Materials 261-263 (April 2004): 1135–40. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.1135.
Повний текст джерелаАнотація:
In recent, ferritic stainless steels are widely used in high temperature structure because of their high resistance in thermal fatigue and low prices. Tensile and low cycle fatigue(LCF) tests on 429EM stainless steel were performed at several temperatures from room temperature to 600°C. Elastic modulus, yield stress and ultimate tensile strength(UTS) decreased with increasing temperature. Considerable cyclic hardening occurred at 200°C and 400°C. 475°C embrittlement observed could not explain this phenomenon but dynamic strain aging(DSA) observed from 200°C to 500°C could explain the hardening mechanism at 200°C and 400°C. And it was observed that plastic strain energy density(PSED) was useful to predict fatigue life when large cyclic hardening occurred. Fatigue life using PSED over elastic modulus could be well predicted within 2X scatter band at various temperatures.
26
Çavusoglu, Onur, Hakan Gürün, Serkan Toros, and Ahmet Güral. "Strain rate sensitivity and strain hardening response of DP1000 dual phase steel." Metallurgical Research & Technology 115, no. 5 (2018): 507. http://dx.doi.org/10.1051/metal/2018016.
Повний текст джерелаАнотація:
In this study, strain hardening and strain rate sensitivity behavior of commercial DP1000 dual phase steel have been examined in detail at temperatures of 25 °C, 100 °C, 200 °C and 300 °C, at strain rates of 0.0016 s−1 and 0.16 s−1. As the strain rate has increased, the yield strength has increased but no significant change in tensile strength and strain hardening coefficient has been observed. As the temperature has increased, the yield and tensile strength has decreased in between 25 and 200 °C but it has showed an increase at 300 °C. The strain hardening coefficient has increased in parallel with temperature increase. It has been seen that the strain rate sensitivity has not been affected by temperature. No significant difference in the hardening rate has appeared in between 25 and 200 °C, but the highest value has been calculated at 300 °C. It has been determined that the fracture behavior has occurred earlier and load carrying capacity on necking has reduced with the increase of strain rate and not significantly affected by temperature.
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Herrera, C., R. L. Plaut, and Angelo Fernando Padilha. "Microstructural Refinement during Annealing of Plastically Deformed Austenitic Stainless Steels." Materials Science Forum 550 (July 2007): 423–28. http://dx.doi.org/10.4028/www.scientific.net/msf.550.423.
Повний текст джерелаАнотація:
The phenomena of strain hardening, strain induced martensite formation, recovery, martensite reversion and recrystallization have been studied in austenitic stainless steels of the AISI 304L and 316L types, after solution annealing, followed by rolling at different temperatures (-196, 25, 100 and 200°C) and subsequent annealing of the worked samples. Strain hardening and the percentage of α’ martensite formed showed strong dependency with the deformation temperature and with the austenite chemical composition. As expected, both strain hardening as well as the amount of the martensite formed was higher in the 304L steel and for lower temperatures. Reversion temperature of the α’ martensite was close to 550°C for both steels, independent of the amount of martensite. The 316L steel presented a higher resistance to recrystallization when compared to the 304L steel. The recrystallization temperature of both steels was about 150°C higher than the α’ phase reversion temperature. Rolling temperature did not influence significantly the recrystallization temperature. Proper thermal and mechanical treatments lead to interesting combinations of mechanical properties in both steels with values such as yield strength YS of about 1000 MPa, with an elongation around 10%.
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Westermann, Ida, Odd Sture Hopperstad, and Magnus Langseth. "Mechanical Behaviour of an AA6082 Aluminium Alloy at Low Temperatures." Materials Science Forum 794-796 (June 2014): 532–37. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.532.
Повний текст джерелаАнотація:
Aluminium alloys are known to have good cryogenic properties. However, little work is reported on aluminium alloys in the temperature range from room temperature and down to-100°C, which are likely operating temperatures in arctic regions. This work is an experimental study of the low temperature mechanical properties of an extruded AA6082 aluminium alloy in the T6 condition approved for marine applications. Quasi-static and dynamic tensile testing has been carried out at different temperatures from room temperature and down to-70°C. This decrease in temperature leads to a 10 % increase in yield strength. No significant influence of temperature was found on the area reduction to fracture. The work-hardening behaviour has been analysed for different temperatures and strain rates by fitting a generalized Voce rule to the tensile data. The initial work-hardening rate is found to depend weakly on the temperature and strain rate.
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Tibbits, WN, and JB Reid. "Frost Resistance in .Eucalyptus nitens (Deane & Maiden) Maiden: Physiological Aspects of Hardiness." Australian Journal of Botany 35, no. 3 (1987): 235. http://dx.doi.org/10.1071/bt9870235.
Повний текст джерелаАнотація:
The effects of photoperiod, temperature regime and differential root and shoot temperatures on frost resistance were examined in both hardening and dehardening Eucalyptus nitens seedlings. Frost resist- ance was primarily determined by measuring the relative loss of electrolytes from frosted leaf discs. This method of assessing frost resistance compares favourably with the frosting of whole seedlings since the critical temperatures producing 50% leaf death in whole seedlings and the leakage of 50% of cellular electrolytes (T50) agreed to within 0.6°C after 14 and 28 days' hardening. Unhardened seedlings had T50 values of - 3.4°C. Seedlings hardening over a 56 day period, at night temperatures of 3°C for 16 h and days of 13-25°C, steadily increased in frost resistance to T50 values of -7.5°C. Reducing the daily amount of hardening temperature from 16 to 8 h produced seedlings that were over 1.0°C less frost resistant at the end of 42 days' hardening. On the other hand, seedlings exposed to a constant 3°C, day and night, suffered considerable water stress and were unable to harden beyond -5.8°C, even after 77 days. Heating seedling roots to between 6 and 18°C throughout the 3°C regime maintained high plant water status but did not confer any increased frost resistance. Rates of dehardening in well hardened seedlings increased with increasing day and 1 or night tempera- ture in the range 6-20°C. Seedlings exposed to 14 h nights at 6.0°C, just 3°C warmer than the hardening temperatures used, were unable to maintain T50 levels of -7.5°C and dehardened by 2.5°C over a 3-week period. The dehardening rate of leaves from seedlings exposed to an air temperature of 18°C day and night was significantly reduced if roots were exposed to 3°C.
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Eagles, C. F. "Temperature-induced changes in cold tolerance of Lolium perenne." Journal of Agricultural Science 113, no. 3 (December 1989): 339–47. http://dx.doi.org/10.1017/s0021859600070027.
Повний текст джерелаАнотація:
SUMMARYResponses of cultivars of Lolium perenne with contrasting winter hardiness to hardening and dehardening at different temperatures were studied in controlled-environment experiments in 1984/85. After hardening at 2 °C, the hardy cultivars Premo and S23 had faster initial rates of change of LT50 (lethal temperature at which 50% of plants were killed), measured on seedlings in an artificial freezing test, and achieved a greater degree of cold tolerance than the susceptible cultivar Grasslands Ruanui. When acclimated at higher temperatures (4–10 °C), the hardier cultivars were better able to develop increased cold tolerance than Grasslands Ruanui. Plants of Premo and S23, previously hardened at 2 °C, maintained their cold tolerance when transferred to warmer temperatures (4–12 °C) better than Grasslands Ruanui, which dehardened even at 4 °C.The responses of the cultivars to hardening and dehardening temperatures under controlled-environment conditions were reflected in seasonal changes in hardiness, measured as cold tolerance of tillers sampled during fluctuating temperatures of a typical maritime winter (1977/78) at Aberystwyth, UK.
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Vourlias, G., N. Pistofidis, and K. Chrissafis. "High-temperature oxidation of precipitation hardening steel." Thermochimica Acta 478, no. 1-2 (November 2008): 28–33. http://dx.doi.org/10.1016/j.tca.2008.08.006.
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Fukumoto, Yohei, Keiji Yamada, Akira Hosokawa, Takashi Ueda, and Mahfudz Al Huda. "Fundamental Study on Temperature of Laser Hardening." Proceedings of Conference of Hokuriku-Shinetsu Branch 2002.39 (2002): 315–16. http://dx.doi.org/10.1299/jsmehs.2002.39.315.
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Shin, I. G. "Temperature in contact zone during shot hardening." Russian Engineering Research 30, no. 1 (January 2010): 61–63. http://dx.doi.org/10.3103/s1068798x10010132.
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Song, K. J., Y. H. Wei, Z. B. Dong, K. Fang, W. J. Zheng, and R. Ma. "Visco-Elastic-Plastic Constitutive Model for A7N01-T6 Alloy Welding and Analytical Solutions with Finite Element Codes." Applied Mechanics and Materials 446-447 (November 2013): 284–87. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.284.
Повний текст джерелаАнотація:
This paper has established a viscoelasticplastic constitutive model for A7N01T6 alloy welding, which is temperature and deformation history dependent. The model uses elasticmixed hardening plastic and creep equation to describe the strain hardening at low temperatures and strain softening at high temperatures, respectively. Then it is applied for finite element numerical simulation of the welding process. By comparison with the conventional temperature dependent elasticperfectly plastic model, the overall longitudinal residual compressive plastic strain and the maximum deformation of welding sheet are larger. This is because that the plastic strain is mostly produced in high temperature range. Strain softening has great influence on the evolution of plastic strain. The compressive plastic strain during heating is larger than the tensile plastic strain during cooling. Strain hardening effect on welding residual strain and stress is almost negligible. Using the established constitutive model, welding residual stress and strain are in good agreement with the theoretical results.
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Kim, B. J., S. M. Son, K. S. Park, and Young Hoon Moon. "The Effects of the Heating Conditions on the Hydro-Formability of the Aluminum Alloys at High Temperatures." Materials Science Forum 475-479 (January 2005): 3307–10. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3307.
Повний текст джерелаАнотація:
Modern automobiles are built with a steadily increasing variety of materials and semifinished products. The traditional composition of steel sheet and cast iron is being replaced with other materials such as aluminum and magnesium. But low formability of these materials has prevented the application of the automotive components. The formability can be enhanced by conducting the warm hydroforming using induction heating device which can raise the temperature of the specimen very quickly. The specimen applied to the test is AA6061 extruded tubes which belong to the age-hardenable aluminum alloys. But in the case of AA6061 age hardening occurs at room temperature or at elevated temperatures before and after the forming process. In this study the effects of the heating condition such as heating time, preset temperature, holding time during die closing and forming time on the hydroformability are analyzed to evaluate the phenomena such as dynamic strain hardening and ageing hardening at high temperatures after the hydroforming process.
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Ma, Sheng Qiang, Jian Dong Xing, Ya Ling He, Ye Fei Li, Han Guang Fu, Zhi Fu Huang, and Yi Min Gao. "Effect of Heat Treatment on Microstructures and Mechanical Properties of Al-Modified Boron High Speed Steel." Key Engineering Materials 732 (March 2017): 24–31. http://dx.doi.org/10.4028/www.scientific.net/kem.732.24.
Повний текст джерелаАнотація:
Boron-bearing high speed steels are widely used in roller materials because of their improved wear resistance and toughness. In present work, aluminum was added into boron high speed steel and the aging-hardening behavior and microstructures of tempered boron high speed steel at various tempering temperatures were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy dispersive spectrometry (EDS) and HR-150A Rockwell hardness tester. The results show that the bulk hardness of boron high speed steel gradually enhances with the increasing destabilized temperature. Aluminum addition cuts down the bulk hardness and delays the hardening process, thus leading to high the hardening value of boron high speed steel shifting to higher destabilized temperature. After tempering process, boron-bearing high speed steel displays precipitate-hardening behavior at the tempered temperature of about 520°C. The bulk hardness of boron-bearing high speed steel achieves 60.5 HRC as a maximum value when the aluminum addition is 0.6 wt.%. More aluminum addition can result in lower precipitate-hardening rate and bulk hardness. The microstructures of boron high speed steel tempered at 520°C consist of eutectic borides and tempered martensite dispersed a lot of secondary precipitates. XRD and TEM results indicate that the precipitate-hardening properties of boron high speed steel depend on precipitates and square degree of martensite
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Dzhusoev, German, Michael Orlov, Olga Vasileva, and Alexey Slavin. "Ensuring the rational temperature conditions for concrete hardening." E3S Web of Conferences 91 (2019): 02020. http://dx.doi.org/10.1051/e3sconf/20199102020.
Повний текст джерелаАнотація:
One of the important aspects of the production technology of monolithic reinforced concrete is to ensure the rational temperature hardening of concrete that can provide high-quality concrete with a minimum duration of heat treatment and minimize energy costs. The article contains ways to solve the problem of ensuring a rational temperature setting of hardening. The task requires the development of a general method for calculating the temperature field of concrete in a hardening reinforced concrete structure. The proposed method of calculating considers a mathematical model of the temperature field in a hardening concrete structure of any shape with different conditions on the heat exchange surfaces and can be applied in various ways of heat treatment of concrete. For solving the equations of thermal conductivity and kinetics of heat release of concrete, the initial and boundary conditions must be specified. Moreover, the influence of reinforcing and simulation of heat distribution in the frozen basis is studied.
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Hung, Tsung-Pin, Chao-Ming Hsu, Hsiu-An Tsai, Shuo-Ching Chen, and Zong-Rong Liu. "Temperature Field Numerical Analysis Mode and Verification of Quenching Heat Treatment Using Carbon Steel in Rotating Laser Scanning." Materials 12, no. 3 (February 11, 2019): 534. http://dx.doi.org/10.3390/ma12030534.
Повний текст джерелаАнотація:
Temperature history and hardening depth are experimentally characterized in the rotational laser hardening process for an AISI 1045 medium carbon steel specimen. A three-dimensional finite element model is proposed to predict the temperature field distribution and hardening zone area. The laser temperature field is set up for an average distribution and scanned along a circular path. Linear motion also takes place alongside rotation. The prediction of hardening area can be increased by increasing the rotational radius, which in turn raises the processing efficiency. A good agreement is found between the experimental characterized hardness value and metallographic composition. The uniformity of the hardening area decreases with increasing laser scanning speed. The increased laser power input could help to expand the hardening depth.
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Yamabe-Mitarai, Yoko, Tomohiro Maruko, Tomoaki Miyazawa, and Tosiyuki Morino. "Solid Solution Hardening Effect of Ir." Materials Science Forum 475-479 (January 2005): 703–6. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.703.
Повний текст джерелаАнотація:
Solid solution hardening effects of Ir was investigated to develop high temperature materials at 2223 K. Pt, Rh, Hf, and Zr were chosen as second elements because their solubility into Ir at 2223 K is over 2at% and the melting temperatures of Ir solid solution are above 2273 K. Compressive strength of Ir solid solution at 2223K were investigated. Solid solution hardening effect of Ir is discussed in terms of lattice parameter change and solubility,
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Liu, Shuaiyang, Aiqin Wang, and Jingpei Xie. "Effect of Deformation Temperature, Strain Rate and Strain on the Strain Hardening Exponent of Copper/Aluminum Laminated Composites." Advanced Composites Letters 27, no. 4 (July 2018): 096369351802700. http://dx.doi.org/10.1177/096369351802700401.
Повний текст джерелаАнотація:
In order to investigate the strain hardening behaviour of Cu/Al laminated composites, isothermal compression tests were conducted in the temperature range of 300–450 °C and stain rate range of 0.01–1 s−1. Based on the experimental data, stain hardening exponent n was calculated to evaluate the strain hardening ability of Cu/Al laminated composites during the deformation process. The results show that deformation temperature, strain rate, strain and laminated structure are all responsible for the evolution of flow stress during the isothermal compression. The highly non-linear character of Ln σ - Ln ε curves shows the dynamic competition between work hardening and dynamic softening, and dynamic softening gradually plays a dominant role with the increase of strain. Furthermore, strain hardening exponent n is more sensitive to deformation temperature than strain rate. Lower deformation temperature and higher strain rate contribute to the enhancement of strain hardening exponent n.
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Davari, Mohammad, and Mehdi Mansouri Hasan Abadi. "Investigation of intercritical heat treatment temperature effect on microstructure and mechanical properties of dual phase (DP) steel." Metallurgical and Materials Engineering 23, no. 2 (June 30, 2017): 143–52. http://dx.doi.org/10.30544/293.
Повний текст джерелаАнотація:
In the present study, the effect of intercritical heat treatment temperature on the tensile properties and work hardening behavior of ferritic-martensitic dual-phase steel have been investigated utilizing tensile test, microhardness measurement and microscopic observation. Plain carbon steel sheet with a thickness of 2 mm was heat treated at 760, 780, 800, 820 and 840 °C intercritical temperatures. The results showed that martensite volume fraction (Vm) increases from 32 to 81%with increasing temperature from 760 to 840 °C. The mechanical properties of samples were examined by tensile and microhardness tests. The results revealed that yield strength was increased linearly with the increase in Vm, but the ultimate strength was increased up to 55% Vm and then decreased afterward. Analyzing the work hardening behavior in term of Hollomon equation showed that in samples with less than 55% Vm, the work hardening took place in one stage and the work hardening exponent increased with increasing Vm. More than one stage was observed in the work hardening behavior when Vm was increased. The results of microhardness test showed that microhardness of the martensite is decreased by increase in heat treatment temperature while the ferrite microhardness is nearly constant for all heat-treated samples.
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Angella, Giuliano. "Flow Curve Modelling of an Austenitic Stainless Steel at High Temperatures Starting from the One-Parameter Model of Strain Hardening." Materials Science Forum 706-709 (January 2012): 1361–66. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1361.
Повний текст джерелаАнотація:
The flow curves of an austenitic stainless steel deformed at temperatures 700-1000°C with strain rates 10-5-10-2s-1were modelled with the Voce equation. The parameters needed to draw the Voce equation, are the saturation stressσVthat defines the height of the flow curve, the critical strainεCthat defines the velocity to achieveσV, and the stressσo, namely the back-extrapolated flow stress to zero strain. A modified strain hardening analysis based on the one-parameter model was used to analyze the strain hardening rate dσ/dεvs. the flow stressσin order to obtainσVandεC. The modified approach was based on the assumption that the dislocation multiplication component of strain hardening was temperature and strain rate dependent through the thermal activation termsof flow stress. A parameters’ proportional toswas obtained from the strain hardening analysis and a relationship betweens’ and temperature and strain rate was found. Relationships betweenσV,σo,εCands’ were finally established and at this stage the Voce equation could reproduce the experimental flow curves at any imposed deformation conditions of temperature and strain rate.
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Angella, Giuliano. "Work Hardening and Tensile Behaviour of an Austenitic Stainless Steel at High Temperature." Materials Science Forum 638-642 (January 2010): 2973–78. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.2973.
Повний текст джерелаАнотація:
The work hardening and tensile behaviour of AISI 316L austenitic stainless steel deformed at temperatures between 600 and 1000°C has been investigated. The alloy has been heat-treated according two different roots: the first solutioning treatment was imposed at 1100°C and the second was designed at 875°C to reduce the dynamic ageing that occurs at temperatures up to 650°C in AISI 316L. In the solutionised material the work hardening data presented two linear regions: at high stresses the linearity has been described as the conventional Stage III of work hardening, whilst at low stresses the linearity has not been rationalised in any conventional stage of work hardening. In the second heat treatment alloy the work hardening data showed a single linear region at high stresses, whilst no linear stage occurred at low stresses. Therefore, the work hardening and tensile behaviour of AISI 316L has resulted to be significantly affected by the two different heat treatments and dynamic aging has been proved to influence work hardening behaviour well beyond the range of temperatures in which serrated yielding occurs.
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Medhurst, Tim, Alfons Esderts, and Rainer Masendorf. "Fatigue Life Calculation Concepts for Structures with Locally Modified Properties." Advanced Materials Research 137 (October 2010): 317–46. http://dx.doi.org/10.4028/www.scientific.net/amr.137.317.
Повний текст джерелаАнотація:
The influence of forming on the cyclic behaviour of various thin sheet metals with austenitic phases is looked into, with the main focus lying on the variation of cyclic parameters and the progression of work hardening over the materials’ fatigue life. There is a marked interaction of hardening due to increased dislocation density resulting from forming and hardening due to cyclic straining under varying strain amplitudes of strain controlled LCF testing. This is strongly dependant on the degree of forming and the amplitude of the following cyclic loading. Also, the temperature influence during forming of addtional forming elements in a temperature controlled die on the fatigue performance of austenitic and complex three phase steels was analysed, showing a marked influence of the forming temperature on the fatigue performance, enabling positive effects to be achieved by choosing suitable material specific forming temperatures.
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Hung, Tsung-Pin, Hao-En Shi, and Jao-Hwa Kuang. "Temperature Modeling of AISI 1045 Steel during Surface Hardening Processes." Materials 11, no. 10 (September 25, 2018): 1815. http://dx.doi.org/10.3390/ma11101815.
Повний текст джерелаАнотація:
A Coupled thermo-mechanical finite element model was employed to simulate the possible effects of varying laser scanning parameters on the surface hardening process for AISI 1045 and AISI 4140 steels. We took advantage of the high-power density of laser beams to heat the surface of workpieces quickly to achieve self-quenching effects. The finite element model, along with the temperature-dependent material properties, was applied to characterize the possible quenching and tempering effects during single-track laser surface heat treatment. We verified the accuracy of the proposed model through experiments. The effects of laser surface hardening parameters, such as power variation, scanning speed, and laser spot size, on the surface temperature distribution, hardening width, and hardening depth variations during the single-track surface laser treatment process, were investigated using the proposed model. The analysis results show that laser power and scanning speed are the key parameters that affect the hardening of the material. The numerical results reveal that the proposed finite element model is able to simulate the laser surface heat treatment process and tempering effect of steel.
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Qin, Shuang, Muxin Yang, Fuping Yuan, and Xiaolei Wu. "Simultaneous Improvement of Yield Strength and Ductility at Cryogenic Temperature by Gradient Structure in 304 Stainless Steel." Nanomaterials 11, no. 7 (July 19, 2021): 1856. http://dx.doi.org/10.3390/nano11071856.
Повний текст джерелаАнотація:
The tensile properties and the corresponding deformation mechanism of the graded 304 stainless steel (ss) at both room and cryogenic temperatures were investigated and compared with those of the coarse-grained (CGed) 304 ss. Gradient structures were found to have excellent synergy of strength and ductility at room temperature, and both the yield strength and the uniform elongation were found to be simultaneously improved at cryogenic temperature in the gradient structures, as compared to those for the CG sample. The hetero-deformation-induced (HDI) hardening was found to play a more important role in the gradient structures as compared to the CG sample and be more obvious at cryogenic temperature as compared to that at room temperature. The central layer in the gradient structures provides stronger strain hardening during tensile deformation at both temperatures, due to more volume fraction of martensitic transformation. The volume fraction of martensitic transformation in the gradient structures was found to be much higher at cryogenic temperature, resulting in a much stronger strain hardening at cryogenic temperature. The amount of martensitic transformation at the central layer of the gradient structures is observed to be even higher than that for the CG sample at cryogenic temperature, which is one of the origins for the simultaneous improvement of strength and ductility by the gradient structures at cryogenic temperature.
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Zhao, Qing-Long, Tong-Tong Shan, Run Geng, Yang-Yang Zhang, Hong-Yun He, Feng Qiu, and Qi-Chuan Jiang. "Effect of Preheating Temperature on the Microstructure and Tensile Properties of 6061 Aluminum Alloy Processed by Hot Rolling-Quenching." Metals 9, no. 2 (February 3, 2019): 182. http://dx.doi.org/10.3390/met9020182.
Повний текст джерелаАнотація:
The present work investigates the microstructure and tensile properties of a hot rolled 6061 alloy quenched by cold rolls (RQ) at different preheating temperatures. The preheating temperature strongly affects microstructure evolution and mechanical properties. Low preheating temperature (490 °C) resulted in both low strength and low elongation. The RQ alloy preheated at 540 °C exhibited improved ductility compared to those subjected to T6 and T8 temper, and comparable strength to that after T8 temper. The dynamic recovery during hot rolling contributed to the improved tensile elongation and retained work hardening. High preheating temperature also led to pronounced ageing hardening during short-term ageing.
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Frerichs, Friedhelm, Yang Lu, Thomas Lübben, and Tim Radel. "Process Signature for Laser Hardening." Metals 11, no. 3 (March 11, 2021): 465. http://dx.doi.org/10.3390/met11030465.
Повний текст джерелаАнотація:
During many manufacturing processes for surface treatment of steel components heat will be exchanged between the environment and the workpiece. The heat exchange commonly leads to temperature gradients within the surface near area of the workpiece, which involve mechanical strains inside the material. If the corresponding stresses exceed locally the yield strength of the material residual stresses can remain after the process. If the temperature increase is high enough additionally phase transformation to austenite occurs and may lead further on due to a fast cooling to the very hard phase martensite. This investigation focuses on the correlation between concrete thermal loads such as temperature and temperature gradients and resulting modifications such as changes of the residual stress, the microstructure, and the hardness respectively. Within this consideration the thermal loads are the causes of the modifications and will be called internal material loads. The correlations between the generated internal material loads and the material modifications will be called Process Signature. The idea is that Process Signatures provide the possibility to engineer the workpiece surface layer and its functional properties in a knowledge-based way. This contribution presents some Process Signature components for a thermally dominated process with phase transformation: laser hardening. The target quantities of the modifications are the change of the residual stress state at the surface and the position of the 1st zero-crossing of the residual stress curve. Based on Finite Element simulations the internal thermal loadings during laser hardening are considered. The investigations identify for the considered target quantities the maximal temperature, the maximal temperature gradient, and the heating time as important parameters of the thermal loads.
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Jia, Bin, Zheng Liang Li, Jun Lin Tao, and Chun Tao Zhang. "Mechanical Behavior and Constitutive Equation of Concrete under High-Temperature Dynamical Conditions." Advanced Materials Research 228-229 (April 2011): 303–8. http://dx.doi.org/10.4028/www.scientific.net/amr.228-229.303.
Повний текст джерелаАнотація:
SPHB tests of concrete under different temperatures and various loading conditions are completed, and high-temperature dynamical behavior of concrete is obtained. Dynamical mechanical behavior of concrete with high temperature is affected by not only the strain rate effect, but also the high temperature weakening effect, and the strain rate hardening effect is coupled with high temperature weakening effect, but the latter has greater influence. Concrete failure evolution is described on basis of the damage factor, the intercoupling strain rate hardening effect and temperature weakening effect are simply set as mutually independent factors, each parameter is respectively fitted with test data, finally, concrete constitutive equation under high-temperature dynamical conditions is established, and comparative analysis with test data are conducted, indicating good coincidence with test results.
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Belykh, Irina, Viktor Sopov, Larisa Butska, Lidiya Pershina, and Olga Makarenko. "Predicting the strength and maturity of hardening concrete." MATEC Web of Conferences 230 (2018): 03001. http://dx.doi.org/10.1051/matecconf/201823003001.
Повний текст джерелаАнотація:
When predicting the growth of strength and maturity of hardening concrete, the role of the temperature factorshould be taken into account. Taking into account the temperature factor requires at the initial stage of hardening of concrete low positive temperatures and low speed of heating concrete. The level of maximum heating of concrete will depend not only on the exothermy of the cement, but also on the amplitude of the fluctuations in the ambient temperature. The contribution to the cracking of concrete of various types of cements from the point of view of heat release during their hydration is analyzed. The existing models for predicting the character of the set of strength and maturity of concrete on the basis of data on heat dissipation during hydration of cement in concrete structures are analyzed. It is shown that laboratory tests are insufficient to evaluate the nature of heat generation. To effectively predict the physical and mechanical properties, it is necessary to conduct temperature-time monitoring during the concrete hardening in the design to take into account the influence of external factors.