In the traditional blast furnace(BF)ironmaking process in China,a notable deviation exists between the theoretical and actual yield of hot metal,leading to unexpected iron loss and restricting the improvement of produ...In the traditional blast furnace(BF)ironmaking process in China,a notable deviation exists between the theoretical and actual yield of hot metal,leading to unexpected iron loss and restricting the improvement of production capacity,which cannot adapt to the increasingly intensified smelting rhythm.Focusing on a BF in a Chinese steel enterprise,a deep neural network algorithm was designed to model the impact of multiple parameters on actual yield of hot metal in a single BF smelting cycle,successfully accomplishing the theoretical computation and real-time prediction of yield of hot metal for subsequent,unknown BF smelting cycle.Test results show that the proposed algorithm demonstrates an impressive prediction accuracy of 86.7% within an error range of±10 t and can swiftly complete the training and convergence process in 32.5 s.By integrating prediction results with Nomogram,a regulatory mechanism was engineered to minimize the deviation between theoretical and actual yield of hot metal.This mechanism ensures the yield enhancement of hot metal through dynamic adjustments of BF operational parameters.Industrial-scale application experiments confirmed that the intelligent operation and optimization system,developed in the laboratory,can maintain the yield deviation of hot metal within a stable range of 30 t,achieving a maximum reduction in iron loss rate of 17.65%compared to that before system operation.The findings provide robust support for the yield increase and efficiency improvement of the experimental BF.展开更多
Soil amendment with fly ash（FA） and combined supplementation with N_2-fixing cyanobacteria masses as biofertilizer were done in field experiments with rice. Amendments with FA levels, 0, 0.5, 1.0, 2.0, 4.0, 8.0 and ...Soil amendment with fly ash（FA） and combined supplementation with N_2-fixing cyanobacteria masses as biofertilizer were done in field experiments with rice. Amendments with FA levels, 0, 0.5, 1.0, 2.0, 4.0, 8.0 and 10.0 kg/m2, caused increase in growth and yield of rice up to 8.0 kg/m2, monitored with several parameters. Pigment contents and enzyme activities of leaves were enhanced by FA, with the maximum level of FA at 10.0 kg/m2. Protein content of rice seeds was the highest in plants grown at FA level 4.0 kg/m2. Basic soil properties, p H value, percentage of silt, percentage of clay, water-holding capacity, electrical conductivity, cation exchange capacity, and organic carbon content increased due to the FA amendment. Parallel supplementation of FA amended plots with 1.0 kg/m2 N_2-fixing cyanobacteria mass caused further significant increments of the most soil properties, and rice growth and yield parameters. 1000-grain weight of rice plants grown at FA level 4.0 kg/m2 along with cyanobacteria supplementation was the maximum. Cyanobacteria supplementation caused increase of important basic properties of soil including the total N-content. Estimations of elemental content in soils and plant parts（root and seed） were done by the atomic absorption spectrophotometry. Accumulations of K, P, Fe and several plant micronutrients（Mn, Ni, Co, Zn and Cu） and toxic elements（Pb, Cr and Cd） increased in soils and plant parts as a function of the FA gradation, but Na content remained almost unchanged in soils and seeds. Supplementation of cyanobacteria had ameliorating effect on toxic metal contents of soils and plant parts. The FA level 4.0 kg/m2, with 1.0 kg/m2 cyanobacteria mass supplementation, could be taken ideal, since there would be recharging of the soil with essential micronutrients as well as toxic chemicals in comparative lesser proportions, and cyanobacteria mass would cause lessening toxic metal loads with usual N_2-fixation.展开更多
Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface ...Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron（SE） and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.展开更多
A pot experiment was conducted to determine the potential of AM fungi in phytoremediation of heavy metals and its effect on yield of wheat crop. The experiment was conducted in CR Design with four replications during ...A pot experiment was conducted to determine the potential of AM fungi in phytoremediation of heavy metals and its effect on yield of wheat crop. The experiment was conducted in CR Design with four replications during rabi 2012-13. Data showed no increase in grain and shoot yields by AMF inoculation with Zn, Cu, Fe, Mn at different levels but increased root yield, plant height, spike length and hundred grains weight of wheat as compared with uninoculated crop. Post-harvest soil Zn, Cu, Fe and Mn contents of 2, 4.4, 2.8 and 2.9 mg·kg-1, respectively were maximum in uninoculated plants treated with Zn, Cu, Fe, Mn at triple of recommended level. No increases in plant P, N, Zn, Cu, Fe and Mn uptakes were observed by the inoculation of AMF when compared with uninoculated crop. Maximum plant Zn, Cu, Fe and Mn uptakes of 160.5, 206, 1914.6 and 2653 g·ha-1, respectively were recorded in uninoculated plants applied with Zn, Cu, Fe, Mn at triple of recommended levels. Wheat roots infection intensity by AMF increased with higher AMF soil spores density. Results suggest the potential of phytoremediation of contaminated soil to be improved by the inoculation of crops with AMF.展开更多
Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was f...Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was fabricated by squeezing cast, were investigated by using continuous loading method on an Instron 5569 tester with a special extensometer with an accuracy of 10?7. The results show that MYS of MMC decreases with the increase of volume fraction and length of the alumina silicate short fibers in the metal matrix composite, respectively. MYS of quenched Al2O3-SiO2(sf)/Al-Si MMC is the lowest, MYS of the MMC through peak-aging treatment is higher than that through other heat treatment methods. And before the peak-aging, MYS of MMC aging treated gradually increases with the increase of the aging time. Aging treatment after solution treatment is a preferred way that enhances micro and macro-yield strength of Al2O3-SiO2(sf)/Al-Si MMC.展开更多
Using large strain two dimension axisymmetric elasto plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal mat...Using large strain two dimension axisymmetric elasto plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal matrix composite and their dependencies on the material structure parameters (fiber volume fraction, fiber aspect ratio and fiber end distance) were studied. It is demonstrated that the stress strain partition parameter can be used to describe the stress transfer from the matrix to the fiber. The variation of the second derivation of the stress strain partition parameter can be used to determine the elastic modulus, the proportion limit, the initial and final yield strengths. In the presence of thermal residual stress, these yielding properties are asymmetric and are influenced differently by the material structure parameters under tensile and compressive loadings.展开更多
A new modification for the shear lag model is given and the expressions for the stiffness and yield Strength of short fiber metal matri×composite are derived. These expressions are then compared with our experime...A new modification for the shear lag model is given and the expressions for the stiffness and yield Strength of short fiber metal matri×composite are derived. These expressions are then compared with our experimental data in a SiCw/Al-Li T6 composite and the published experimental data on different SiCw/Al T6 composites and also compared with the previous shear lag models and the other theoretical models.展开更多
The modified shear lag model proposed recently was applied to calculate thermal residual stresses and subsequent stress distributions under tensile and compressive loadings. The expressions for the elastic moduli and ...The modified shear lag model proposed recently was applied to calculate thermal residual stresses and subsequent stress distributions under tensile and compressive loadings. The expressions for the elastic moduli and the yield strengths under tensile and compressive loadings were derived which take account of thermal residual stresses. The asymmetries in the elastic modulus and the yield strength were interpreted using the derived expressions and the obtained results of the stress calculations. The model predictions have exhibited good agreements with the experimental results and also with the other theoretical predictions展开更多
Over the past few years a number of low cost metallic foams have been produced and used as the core of sandwich panels and net shaped parts.The main aim is to develop lightweight structures which are stiff,strong,able...Over the past few years a number of low cost metallic foams have been produced and used as the core of sandwich panels and net shaped parts.The main aim is to develop lightweight structures which are stiff,strong,able to absorb large amount of energy and cheap for application in the transport and construction industries.For example,the firewall between the engine and passenger compartment of an automobile must have adequate mechanical strength,good energy and sound absorbing properties,and adequate fire retardance.Metal foams provide all of these features,and are under serious consideration for this applications by a number of au- tomobile manufacturers(e.g.,BMW and Audi).Additional specialized applications for foam-cored sandwich panels range from heat sinks for electronic devices to crash barriers for automobiles,from the construction panels in lifts on aircraft carriers to the luggage containers of aircraft,from sound proofing walls along railway tracks and highways to acoustic absorbers in lean premixed combustion chambers.But there is a problem.Before metallic foams can find a widespread application,their basic properties must be measured,and ideally modeled as a function of microstructural details,in order to be included in a design.This work aims at reviewing the recent progress and presenting some new results on fundamental research regarding the mi- cromechanical origins of the mechanical,thermal,and acoustic properties of metallic foams.展开更多
A series of Ti2ZrHf0.5VNbx( x = 0, 0.25, 0.5, 0.75 and 1.0) refractory high-entropy alloys were prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties.All the alloys display...A series of Ti2ZrHf0.5VNbx( x = 0, 0.25, 0.5, 0.75 and 1.0) refractory high-entropy alloys were prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties.All the alloys displayed a simple BCC structure.The microstructures of the alloys changed from the initial single-phase columnar structure( x = 0) to dendrite microstructure( x > 0).At room temperature, all the alloys exhibited high ductility(with the compressive strains of more than 50%).With the increase in Nb content, the yield strength slightly decreased from 1160 to 980 MPa and the hardness dropped from 338 to 310 HV.Moreover, the alloys exhibited low density from 6.47 to 6.84 g/cm3 and high specific yield strength(SYS) from 143 to 179 kPa m3/kg.The comprehensive performance of ductility and SYS was superior to most of the reported highentropy alloys.The yield strength of the alloys increased from 405 to 859 MPa and from 85 to 195 MPa with the addition of Nb element at 873 K and 1073 K, respectively.展开更多
Degradation of soil and water from discharge of untreated industrial effluent is alarming in Bangladesh. Therefore, buildup of heavy metals in soil from contaminated effluent, their entry into the food chain and effec...Degradation of soil and water from discharge of untreated industrial effluent is alarming in Bangladesh. Therefore, buildup of heavy metals in soil from contaminated effluent, their entry into the food chain and effects on rice yield were quantified in a pot experiment. The treatments were comprised of 0, 25%, 50%, 75% and 100% industrial effluents applied as irrigation water. Effluents, initial soil, different parts of rice plants and post-harvest pot soil were analyzed for various elements, including heavy metals. Application of elevated levels of effluent contributed to increased heavy metals in pot soils and rice roots due to translocation effects, which were transferred to rice straw and grain. The results indicated that heavy metal toxicity may develop in soil because of contaminated effluent application.Heavy metals are not biodegradable, rather they accumulate in soils, and transfer of these metals from effluent to soil and plant cells was found to reduce the growth and development of rice plants and thereby contributed to lower yield. Moreover, a higher concentration of effluent caused heavy metal toxicity as well as reduction of growth and yield of rice, and in the long run a more aggravated situation may threaten human lives,which emphasizes the obligatory adoption of effluent treatment before its release to the environment, and regular monitoring by government agencies needs to be ensured.展开更多
This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum ...This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum yield (△F/F′m),photosynthetic pigments and antioxidative enzymes like superoxide dismutase (SOD),guaiacol peroxidase (POD) were also examined.Cadmium was the most highly accumulated metal.Meanwhile,high metals levels led to a remarkable breakdown of photosynthetic parameters.Especially,△F/F′m,chlorophyll and carotenoid were significantly low during prolonged Cu exposure.Besides,△F/F′m was more severely depressed by Cu and Zn than Pb and Cd.However,T.hemprichii had positive response by increasing the activity of SOD and POD.The results indicate that T.hemprichii is the most sensitive to Cu,and the antioxidative protection mechanisms of T.hemprichii are more efficiently activated to avoid damage of Zn,Cd and Pb stress. Finally,due to the high Cd-accumulation and strong Cd-tolerance capacity,T.hemprichii can be used for phytoremediation in Cd-contaminated areas.展开更多
The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro...The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition,and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore,they exhibit more kinematic hardening.展开更多
Tensile tests and notch toughness tests were conducted on Zr61Ti2Cu25Al12 glass （ZT） at room temperature and liquid-nitrogen temperature. The tensile strength of ZT was improved from 1.63 GPa at room temperature to ...Tensile tests and notch toughness tests were conducted on Zr61Ti2Cu25Al12 glass （ZT） at room temperature and liquid-nitrogen temperature. The tensile strength of ZT was improved from 1.63 GPa at room temperature to 1.72 GPa at liquid-nitrogen temperature. Micro-notches with a root radius of 1-3μm were introduced to test the notch toughness of ZT at room temperature and liquid-nitrogen temperature. The test results revealed that the notch toughness of ZT at liquid-nitrogen temperature is comparable to that of ZT at room temperature. The combination of high yield strength and notch toughness of ZT at liquid-nitrogen temperature is comparable to that of the best cryogenic engineering materials.展开更多
The corresponding positions of different metal plastic working processes in the plane stress state on a Mises yield ellipse are described.The paper points out that the forming of a workpiece inside its die is correspo...The corresponding positions of different metal plastic working processes in the plane stress state on a Mises yield ellipse are described.The paper points out that the forming of a workpiece inside its die is corresponding to a mass point moving along the ellipse and that its dimensional variation tendency in all directions can be judged according to a correspondence rule of the stress-strain order offered by the author.In addition,the paper also presents the corresponding three-dimensional positions of different metal plastic working processes on the Mises cylinder,from which the deformation force and technological plasticity required in different processes can be compared,and the dimensional variation tendency can be predicted.The analysis method used in this paper is not to calculate the variation of each stress component(σx,σy,σz) by convention,but to emphasize the variation of the stress state in the typical position,which is expressed correspondingly as the varying locus of points in principal stress space,and then based on the analysis the strain result is judged.展开更多
Cottonseed hull substrates blended with different ratios of Castanea mollissima Blume shell were prepared and used for the cultivation of Pleurotus geesteranus. The effects of the chestnut shell content on the mycelia...Cottonseed hull substrates blended with different ratios of Castanea mollissima Blume shell were prepared and used for the cultivation of Pleurotus geesteranus. The effects of the chestnut shell content on the mycelial growth rate, yield, nutritional composition and contents of heavy metals of the cultivated Pleurotus geesteranus were investigated. The results suggest that the Castanea mollissima Blume shell in substrate can increase the mycelial growth rate, yield, biological efficiency and the contents of protein, crude fiber, amino acids and essential amino acids of Pleurotus geesteranus. Further investigation suggests that the tannin and saponin in Castanea mollissima Blume shell and the C/N ratio of substrate significantly influence the mycelial growth rate. The crude fat content of Pleurotus geesteranus decreased, while the contents of heavy metals including mercury (Hg), arsenic (As), cadmium (Cd) and lead (Pb) increased with the increase of the Castanea mollissima Blume shell content in substrate. Based on these results, the content of Castanea mollissima Blume shell was optimized to be less than 30% for the cultivation of Pleurotus geesteranus.展开更多
基金the financial supports from the National Natural Science Foundation of China(52004096)Natural Science Foundation of Hebei Province(E2024209101)+2 种基金Hebei Province Science and Technology R&D Platform Construction Project(23560301D)Tangshan Science and Technology Bureau Project(23130202E)Graduate Student Innovation Fund of North China University of Science and Technology(CXZZBS2025150).
文摘In the traditional blast furnace(BF)ironmaking process in China,a notable deviation exists between the theoretical and actual yield of hot metal,leading to unexpected iron loss and restricting the improvement of production capacity,which cannot adapt to the increasingly intensified smelting rhythm.Focusing on a BF in a Chinese steel enterprise,a deep neural network algorithm was designed to model the impact of multiple parameters on actual yield of hot metal in a single BF smelting cycle,successfully accomplishing the theoretical computation and real-time prediction of yield of hot metal for subsequent,unknown BF smelting cycle.Test results show that the proposed algorithm demonstrates an impressive prediction accuracy of 86.7% within an error range of±10 t and can swiftly complete the training and convergence process in 32.5 s.By integrating prediction results with Nomogram,a regulatory mechanism was engineered to minimize the deviation between theoretical and actual yield of hot metal.This mechanism ensures the yield enhancement of hot metal through dynamic adjustments of BF operational parameters.Industrial-scale application experiments confirmed that the intelligent operation and optimization system,developed in the laboratory,can maintain the yield deviation of hot metal within a stable range of 30 t,achieving a maximum reduction in iron loss rate of 17.65%compared to that before system operation.The findings provide robust support for the yield increase and efficiency improvement of the experimental BF.
基金supported by the project from Council of Scientific and Industrial Research,New Delhi,India (Grant No.21 (0859)/11/EMR-Ⅱ)
文摘Soil amendment with fly ash（FA） and combined supplementation with N_2-fixing cyanobacteria masses as biofertilizer were done in field experiments with rice. Amendments with FA levels, 0, 0.5, 1.0, 2.0, 4.0, 8.0 and 10.0 kg/m2, caused increase in growth and yield of rice up to 8.0 kg/m2, monitored with several parameters. Pigment contents and enzyme activities of leaves were enhanced by FA, with the maximum level of FA at 10.0 kg/m2. Protein content of rice seeds was the highest in plants grown at FA level 4.0 kg/m2. Basic soil properties, p H value, percentage of silt, percentage of clay, water-holding capacity, electrical conductivity, cation exchange capacity, and organic carbon content increased due to the FA amendment. Parallel supplementation of FA amended plots with 1.0 kg/m2 N_2-fixing cyanobacteria mass caused further significant increments of the most soil properties, and rice growth and yield parameters. 1000-grain weight of rice plants grown at FA level 4.0 kg/m2 along with cyanobacteria supplementation was the maximum. Cyanobacteria supplementation caused increase of important basic properties of soil including the total N-content. Estimations of elemental content in soils and plant parts（root and seed） were done by the atomic absorption spectrophotometry. Accumulations of K, P, Fe and several plant micronutrients（Mn, Ni, Co, Zn and Cu） and toxic elements（Pb, Cr and Cd） increased in soils and plant parts as a function of the FA gradation, but Na content remained almost unchanged in soils and seeds. Supplementation of cyanobacteria had ameliorating effect on toxic metal contents of soils and plant parts. The FA level 4.0 kg/m2, with 1.0 kg/m2 cyanobacteria mass supplementation, could be taken ideal, since there would be recharging of the soil with essential micronutrients as well as toxic chemicals in comparative lesser proportions, and cyanobacteria mass would cause lessening toxic metal loads with usual N_2-fixation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1537211 and 11675278)the China Postdoctoral Science Foundation(Grant No.2016M602944XB)
文摘Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron（SE） and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.
文摘A pot experiment was conducted to determine the potential of AM fungi in phytoremediation of heavy metals and its effect on yield of wheat crop. The experiment was conducted in CR Design with four replications during rabi 2012-13. Data showed no increase in grain and shoot yields by AMF inoculation with Zn, Cu, Fe, Mn at different levels but increased root yield, plant height, spike length and hundred grains weight of wheat as compared with uninoculated crop. Post-harvest soil Zn, Cu, Fe and Mn contents of 2, 4.4, 2.8 and 2.9 mg·kg-1, respectively were maximum in uninoculated plants treated with Zn, Cu, Fe, Mn at triple of recommended level. No increases in plant P, N, Zn, Cu, Fe and Mn uptakes were observed by the inoculation of AMF when compared with uninoculated crop. Maximum plant Zn, Cu, Fe and Mn uptakes of 160.5, 206, 1914.6 and 2653 g·ha-1, respectively were recorded in uninoculated plants applied with Zn, Cu, Fe, Mn at triple of recommended levels. Wheat roots infection intensity by AMF increased with higher AMF soil spores density. Results suggest the potential of phytoremediation of contaminated soil to be improved by the inoculation of crops with AMF.
基金Project(19972021)supported by the National Natural Science Foundation of China
文摘Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was fabricated by squeezing cast, were investigated by using continuous loading method on an Instron 5569 tester with a special extensometer with an accuracy of 10?7. The results show that MYS of MMC decreases with the increase of volume fraction and length of the alumina silicate short fibers in the metal matrix composite, respectively. MYS of quenched Al2O3-SiO2(sf)/Al-Si MMC is the lowest, MYS of the MMC through peak-aging treatment is higher than that through other heat treatment methods. And before the peak-aging, MYS of MMC aging treated gradually increases with the increase of the aging time. Aging treatment after solution treatment is a preferred way that enhances micro and macro-yield strength of Al2O3-SiO2(sf)/Al-Si MMC.
文摘Using large strain two dimension axisymmetric elasto plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal matrix composite and their dependencies on the material structure parameters (fiber volume fraction, fiber aspect ratio and fiber end distance) were studied. It is demonstrated that the stress strain partition parameter can be used to describe the stress transfer from the matrix to the fiber. The variation of the second derivation of the stress strain partition parameter can be used to determine the elastic modulus, the proportion limit, the initial and final yield strengths. In the presence of thermal residual stress, these yielding properties are asymmetric and are influenced differently by the material structure parameters under tensile and compressive loadings.
文摘A new modification for the shear lag model is given and the expressions for the stiffness and yield Strength of short fiber metal matri×composite are derived. These expressions are then compared with our experimental data in a SiCw/Al-Li T6 composite and the published experimental data on different SiCw/Al T6 composites and also compared with the previous shear lag models and the other theoretical models.
文摘The modified shear lag model proposed recently was applied to calculate thermal residual stresses and subsequent stress distributions under tensile and compressive loadings. The expressions for the elastic moduli and the yield strengths under tensile and compressive loadings were derived which take account of thermal residual stresses. The asymmetries in the elastic modulus and the yield strength were interpreted using the derived expressions and the obtained results of the stress calculations. The model predictions have exhibited good agreements with the experimental results and also with the other theoretical predictions
文摘Over the past few years a number of low cost metallic foams have been produced and used as the core of sandwich panels and net shaped parts.The main aim is to develop lightweight structures which are stiff,strong,able to absorb large amount of energy and cheap for application in the transport and construction industries.For example,the firewall between the engine and passenger compartment of an automobile must have adequate mechanical strength,good energy and sound absorbing properties,and adequate fire retardance.Metal foams provide all of these features,and are under serious consideration for this applications by a number of au- tomobile manufacturers(e.g.,BMW and Audi).Additional specialized applications for foam-cored sandwich panels range from heat sinks for electronic devices to crash barriers for automobiles,from the construction panels in lifts on aircraft carriers to the luggage containers of aircraft,from sound proofing walls along railway tracks and highways to acoustic absorbers in lean premixed combustion chambers.But there is a problem.Before metallic foams can find a widespread application,their basic properties must be measured,and ideally modeled as a function of microstructural details,in order to be included in a design.This work aims at reviewing the recent progress and presenting some new results on fundamental research regarding the mi- cromechanical origins of the mechanical,thermal,and acoustic properties of metallic foams.
基金supported financially by the National Natural Science Foundation of China (Nos.51671044, 51822402 and 51574058)the Dalian Support Plan for Innovation of High-level Talents (Top and Leading Talents, No.2015R013)+1 种基金the Fundamental Research Funds for the Central Universities (No.DUT16ZD206)the Dalian Support Plan for Innovation of Highlevel Talents (Youth Technology Stars, No.2016RQ005)
文摘A series of Ti2ZrHf0.5VNbx( x = 0, 0.25, 0.5, 0.75 and 1.0) refractory high-entropy alloys were prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties.All the alloys displayed a simple BCC structure.The microstructures of the alloys changed from the initial single-phase columnar structure( x = 0) to dendrite microstructure( x > 0).At room temperature, all the alloys exhibited high ductility(with the compressive strains of more than 50%).With the increase in Nb content, the yield strength slightly decreased from 1160 to 980 MPa and the hardness dropped from 338 to 310 HV.Moreover, the alloys exhibited low density from 6.47 to 6.84 g/cm3 and high specific yield strength(SYS) from 143 to 179 kPa m3/kg.The comprehensive performance of ductility and SYS was superior to most of the reported highentropy alloys.The yield strength of the alloys increased from 405 to 859 MPa and from 85 to 195 MPa with the addition of Nb element at 873 K and 1073 K, respectively.
基金supported by the Fellowship Program of National Science Information and Communication Technology (NSICT) under Ministry of Science Information and Communication Technology, Bangladesh (code no.- 3-2605-3965-5901)
文摘Degradation of soil and water from discharge of untreated industrial effluent is alarming in Bangladesh. Therefore, buildup of heavy metals in soil from contaminated effluent, their entry into the food chain and effects on rice yield were quantified in a pot experiment. The treatments were comprised of 0, 25%, 50%, 75% and 100% industrial effluents applied as irrigation water. Effluents, initial soil, different parts of rice plants and post-harvest pot soil were analyzed for various elements, including heavy metals. Application of elevated levels of effluent contributed to increased heavy metals in pot soils and rice roots due to translocation effects, which were transferred to rice straw and grain. The results indicated that heavy metal toxicity may develop in soil because of contaminated effluent application.Heavy metals are not biodegradable, rather they accumulate in soils, and transfer of these metals from effluent to soil and plant cells was found to reduce the growth and development of rice plants and thereby contributed to lower yield. Moreover, a higher concentration of effluent caused heavy metal toxicity as well as reduction of growth and yield of rice, and in the long run a more aggravated situation may threaten human lives,which emphasizes the obligatory adoption of effluent treatment before its release to the environment, and regular monitoring by government agencies needs to be ensured.
基金The Chinese Nature Science Foundation (CNSF) Project under contract Nos 40776086 and 41076069Forefront Program of the Knowledge Innovation Project,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No. LYQY200706the National 908 Special Project under contract No. GD908-02-08
文摘This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum yield (△F/F′m),photosynthetic pigments and antioxidative enzymes like superoxide dismutase (SOD),guaiacol peroxidase (POD) were also examined.Cadmium was the most highly accumulated metal.Meanwhile,high metals levels led to a remarkable breakdown of photosynthetic parameters.Especially,△F/F′m,chlorophyll and carotenoid were significantly low during prolonged Cu exposure.Besides,△F/F′m was more severely depressed by Cu and Zn than Pb and Cd.However,T.hemprichii had positive response by increasing the activity of SOD and POD.The results indicate that T.hemprichii is the most sensitive to Cu,and the antioxidative protection mechanisms of T.hemprichii are more efficiently activated to avoid damage of Zn,Cd and Pb stress. Finally,due to the high Cd-accumulation and strong Cd-tolerance capacity,T.hemprichii can be used for phytoremediation in Cd-contaminated areas.
基金supported by the Danish Research Council for Technology and Production Sciences in a project entitled Plasticity Across the Scales
文摘The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition,and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore,they exhibit more kinematic hardening.
基金supported by ARO-W911NF-12-1-0022 with partial support from DTRA-1-11-1-0064
文摘Tensile tests and notch toughness tests were conducted on Zr61Ti2Cu25Al12 glass （ZT） at room temperature and liquid-nitrogen temperature. The tensile strength of ZT was improved from 1.63 GPa at room temperature to 1.72 GPa at liquid-nitrogen temperature. Micro-notches with a root radius of 1-3μm were introduced to test the notch toughness of ZT at room temperature and liquid-nitrogen temperature. The test results revealed that the notch toughness of ZT at liquid-nitrogen temperature is comparable to that of ZT at room temperature. The combination of high yield strength and notch toughness of ZT at liquid-nitrogen temperature is comparable to that of the best cryogenic engineering materials.
文摘The corresponding positions of different metal plastic working processes in the plane stress state on a Mises yield ellipse are described.The paper points out that the forming of a workpiece inside its die is corresponding to a mass point moving along the ellipse and that its dimensional variation tendency in all directions can be judged according to a correspondence rule of the stress-strain order offered by the author.In addition,the paper also presents the corresponding three-dimensional positions of different metal plastic working processes on the Mises cylinder,from which the deformation force and technological plasticity required in different processes can be compared,and the dimensional variation tendency can be predicted.The analysis method used in this paper is not to calculate the variation of each stress component(σx,σy,σz) by convention,but to emphasize the variation of the stress state in the typical position,which is expressed correspondingly as the varying locus of points in principal stress space,and then based on the analysis the strain result is judged.
文摘Cottonseed hull substrates blended with different ratios of Castanea mollissima Blume shell were prepared and used for the cultivation of Pleurotus geesteranus. The effects of the chestnut shell content on the mycelial growth rate, yield, nutritional composition and contents of heavy metals of the cultivated Pleurotus geesteranus were investigated. The results suggest that the Castanea mollissima Blume shell in substrate can increase the mycelial growth rate, yield, biological efficiency and the contents of protein, crude fiber, amino acids and essential amino acids of Pleurotus geesteranus. Further investigation suggests that the tannin and saponin in Castanea mollissima Blume shell and the C/N ratio of substrate significantly influence the mycelial growth rate. The crude fat content of Pleurotus geesteranus decreased, while the contents of heavy metals including mercury (Hg), arsenic (As), cadmium (Cd) and lead (Pb) increased with the increase of the Castanea mollissima Blume shell content in substrate. Based on these results, the content of Castanea mollissima Blume shell was optimized to be less than 30% for the cultivation of Pleurotus geesteranus.
