In order to find an effective and environmentally friendly method to fix compressive deformation of wood, we determined or measured the recovery ratio, surface hardness, modulus of elasticity （MOE） and the modulus o...In order to find an effective and environmentally friendly method to fix compressive deformation of wood, we determined or measured the recovery ratio, surface hardness, modulus of elasticity （MOE） and the modulus of rupture （MOR） of poplar （Populus cathayana Rehd.） samples pretreated by 40-60% glycerin solutions and then compressed at 160℃ for 10-120 min. We analyzed the data statistically by using two-factor analysis of variance. The chemical compositions of thermal treated wood were also analyzed and compared with untreated control samples. The results showed that the compressive deformation of wood can be properly fixed by glycerin pretreatment. The recovery ratio of compressed wood decreased with prolonging compression time and increasing concent-ration of the glycerin solution. However, the mechanical properties of compressed wood decreased after a long time of compression. The optimal fixation of compressive deformation is to pretreat the wood by a solution of 50% glycerin and compression at 160℃ for 60 min. The analysis of chemical composition showed that glycerin displayed an accelerating effect on degradation of hemicelluloses and lignin during heat-treatment, which explains the main reason of the effect of acceleration of glycerin on deformation fixation of compressed wood.展开更多
The independently designed and manufactured ultra-high-strength aluminum alloy Al-12.18 Zn-3.31 Mg-1.43 Cu-0.20 Zr-0.04 Sr was investigated via scanning electron microscopy observations, X-ray diffraction analysis, ha...The independently designed and manufactured ultra-high-strength aluminum alloy Al-12.18 Zn-3.31 Mg-1.43 Cu-0.20 Zr-0.04 Sr was investigated via scanning electron microscopy observations, X-ray diffraction analysis, hardness tests, electrical conductivity tests, tensile tests, intergranular corrosion tests, and exfoliation corrosion tests. The effect of pre-recovery on the microstructure and mechanical properties of this aluminum alloy was also studied. The results show that the pre-recovery heat treatment releases deformation energy, inhibits recrystallization, and decreases the dislocation density. Although the pre-recovery heat treatment has little effect on the hardness, electrical conductivity, and elongation of this aluminum alloy, it can dramatically improve the alloy's tensile strength(the maximum tensile strength increased from 785.0 MPa to 809.2 MPa). Moreover, the tensile properties of this aluminum alloy have a certain degree of isotropy, and the pre-recovery heat treatment does not affect this property. In addition, the rolled aluminum alloy exhibits good corrosion resistance, but the effect of the pre-recovery heat treatment on the alloy's resistance to intergranular and exfoliation corrosion is negligible.展开更多
In this paper, the authors aim to propose the use of waste plastics as a binder in a coconut shell reinforcement for the development of an 8/6 size composite rafter to replace the natural 8/6 size backbone in construc...In this paper, the authors aim to propose the use of waste plastics as a binder in a coconut shell reinforcement for the development of an 8/6 size composite rafter to replace the natural 8/6 size backbone in construction. Following a study into the choice of the best proportions, a total of 30 size 8/6 composite rafters with different proportions of 20%, 25%, 30%, 35%, 40% and 50% plastic content were developed. All the 8/6 composite rafters were subjected to mechanical (3-point bending strength and Monnin hardness) and physical (bulk density and water absorption) characterization analyses. The results show that flexural strength increases from 27.56 MPa to 33.30 MPa for proportions ranging from 20% to 35% plastic content. Above 35% plastic, the strength drops to 19.60 MPa for a 50% plastic content. Similarly, the Monnin hardness drops from 9 mm to 5 mm when the plastic content varies from 20 to 50%. As for the results of the physical characterisation, the values obtained for apparent density vary from 0.89 to 1 for proportions varying from 20% to 35% plastic content and drop to 0.94 for 50% plastic content. As for water absorption, values drop from 6.82% to 2.45% when the plastic content increases from 20% to 50%. These mechanical strengths stabilise at 35% plastic content. The development of an 8/6 chevron composite material based on plastic and coconut shell could therefore be a way of recovering waste and solving the problem of deforestation.展开更多
The effects of rolling driving methods and technical factors on the microstructures and mechanical properties of aluminum foils based on the industrial trials were studied by TEM, tensile test and texture analysis. Th...The effects of rolling driving methods and technical factors on the microstructures and mechanical properties of aluminum foils based on the industrial trials were studied by TEM, tensile test and texture analysis. The results show that there exist obvious dynamic recovery and primary location re crystallization phenomena in the aluminum foils during high speed rolling. Meanwhile the phenomena become more obvious as the rolling speed or the reduction increases, especially in the asymmetrical rolling process with single roller driving, the dynamic primary location recrystallization is more likely to come into being. The effects of the dynamic recovery phenomena and the dynamic primary location recrystallization on the comprehensive final product ratio and the quality of aluminum foils were discussed.展开更多
In the present work,the microstructure features,martensitic transformation,mechanical properties and strain recovery characteristics of Ti-Ta based shape memory alloys were tailored by changing Hf contents.The single...In the present work,the microstructure features,martensitic transformation,mechanical properties and strain recovery characteristics of Ti-Ta based shape memory alloys were tailored by changing Hf contents.The singleα"martensite phase was dominated in Ti-Ta alloy with 2 at.%H f.Upon Hf content exceeded2 at.%,βphase started to appear.Moreover,the amount ofβphase gradually increased with Hf content increasing.The martensitic transformation temperatures continuously decreased with the increased Hf content,which was attributed to the rising of valence electron concentration.Meanwhile,Hf addition improved the thermal cycling stability of Ti-Ta alloys due to the suppression ofωprecipitation.The yield stress of Ti-Ta based alloys firstly decreased and then increased with Hf content increasing.In addition,the completely recoverable strain of 4%can be obtained in Ti-Ta alloy with 6 at.%Hf as a consequence of the higher critical stress for dislocation slip.Besieds,the Ti-Ta based alloy containing 8 at.%Hf had the superior superelasticity behavior with the fully recoverable strain of 2%at room temperature.展开更多
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No.30500386)
文摘In order to find an effective and environmentally friendly method to fix compressive deformation of wood, we determined or measured the recovery ratio, surface hardness, modulus of elasticity （MOE） and the modulus of rupture （MOR） of poplar （Populus cathayana Rehd.） samples pretreated by 40-60% glycerin solutions and then compressed at 160℃ for 10-120 min. We analyzed the data statistically by using two-factor analysis of variance. The chemical compositions of thermal treated wood were also analyzed and compared with untreated control samples. The results showed that the compressive deformation of wood can be properly fixed by glycerin pretreatment. The recovery ratio of compressed wood decreased with prolonging compression time and increasing concent-ration of the glycerin solution. However, the mechanical properties of compressed wood decreased after a long time of compression. The optimal fixation of compressive deformation is to pretreat the wood by a solution of 50% glycerin and compression at 160℃ for 60 min. The analysis of chemical composition showed that glycerin displayed an accelerating effect on degradation of hemicelluloses and lignin during heat-treatment, which explains the main reason of the effect of acceleration of glycerin on deformation fixation of compressed wood.
基金financially supported by the Jiangsu Provincial Industrial Science and Technology Support Program (No. BE2008118)the Basic Research on Isotropic Ultra-high Strength Aluminum Matrix Composite (No. 6140922010201)
文摘The independently designed and manufactured ultra-high-strength aluminum alloy Al-12.18 Zn-3.31 Mg-1.43 Cu-0.20 Zr-0.04 Sr was investigated via scanning electron microscopy observations, X-ray diffraction analysis, hardness tests, electrical conductivity tests, tensile tests, intergranular corrosion tests, and exfoliation corrosion tests. The effect of pre-recovery on the microstructure and mechanical properties of this aluminum alloy was also studied. The results show that the pre-recovery heat treatment releases deformation energy, inhibits recrystallization, and decreases the dislocation density. Although the pre-recovery heat treatment has little effect on the hardness, electrical conductivity, and elongation of this aluminum alloy, it can dramatically improve the alloy's tensile strength(the maximum tensile strength increased from 785.0 MPa to 809.2 MPa). Moreover, the tensile properties of this aluminum alloy have a certain degree of isotropy, and the pre-recovery heat treatment does not affect this property. In addition, the rolled aluminum alloy exhibits good corrosion resistance, but the effect of the pre-recovery heat treatment on the alloy's resistance to intergranular and exfoliation corrosion is negligible.
文摘In this paper, the authors aim to propose the use of waste plastics as a binder in a coconut shell reinforcement for the development of an 8/6 size composite rafter to replace the natural 8/6 size backbone in construction. Following a study into the choice of the best proportions, a total of 30 size 8/6 composite rafters with different proportions of 20%, 25%, 30%, 35%, 40% and 50% plastic content were developed. All the 8/6 composite rafters were subjected to mechanical (3-point bending strength and Monnin hardness) and physical (bulk density and water absorption) characterization analyses. The results show that flexural strength increases from 27.56 MPa to 33.30 MPa for proportions ranging from 20% to 35% plastic content. Above 35% plastic, the strength drops to 19.60 MPa for a 50% plastic content. Similarly, the Monnin hardness drops from 9 mm to 5 mm when the plastic content varies from 20 to 50%. As for the results of the physical characterisation, the values obtained for apparent density vary from 0.89 to 1 for proportions varying from 20% to 35% plastic content and drop to 0.94 for 50% plastic content. As for water absorption, values drop from 6.82% to 2.45% when the plastic content increases from 20% to 50%. These mechanical strengths stabilise at 35% plastic content. The development of an 8/6 chevron composite material based on plastic and coconut shell could therefore be a way of recovering waste and solving the problem of deforestation.
文摘The effects of rolling driving methods and technical factors on the microstructures and mechanical properties of aluminum foils based on the industrial trials were studied by TEM, tensile test and texture analysis. The results show that there exist obvious dynamic recovery and primary location re crystallization phenomena in the aluminum foils during high speed rolling. Meanwhile the phenomena become more obvious as the rolling speed or the reduction increases, especially in the asymmetrical rolling process with single roller driving, the dynamic primary location recrystallization is more likely to come into being. The effects of the dynamic recovery phenomena and the dynamic primary location recrystallization on the comprehensive final product ratio and the quality of aluminum foils were discussed.
基金financially supported by the National Natural Science Foundation of China(Nos.51871080,51931004 and 51571073)the Talent Training Program for Shandong Province Higher Educational Youth Innovative Teams(2019)。
文摘In the present work,the microstructure features,martensitic transformation,mechanical properties and strain recovery characteristics of Ti-Ta based shape memory alloys were tailored by changing Hf contents.The singleα"martensite phase was dominated in Ti-Ta alloy with 2 at.%H f.Upon Hf content exceeded2 at.%,βphase started to appear.Moreover,the amount ofβphase gradually increased with Hf content increasing.The martensitic transformation temperatures continuously decreased with the increased Hf content,which was attributed to the rising of valence electron concentration.Meanwhile,Hf addition improved the thermal cycling stability of Ti-Ta alloys due to the suppression ofωprecipitation.The yield stress of Ti-Ta based alloys firstly decreased and then increased with Hf content increasing.In addition,the completely recoverable strain of 4%can be obtained in Ti-Ta alloy with 6 at.%Hf as a consequence of the higher critical stress for dislocation slip.Besieds,the Ti-Ta based alloy containing 8 at.%Hf had the superior superelasticity behavior with the fully recoverable strain of 2%at room temperature.
