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
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
Twelve lactating Friesian Cows with body weight of 450 to 550 kg and in the second to fifth lactating season were used after 8 weeks of cal- ving in a complete switch-back design. The cows were fed a basal ration of 3...Twelve lactating Friesian Cows with body weight of 450 to 550 kg and in the second to fifth lactating season were used after 8 weeks of cal- ving in a complete switch-back design. The cows were fed a basal ration of 35% concentrate feed mix-ture with 40% berseem and 25% rice straw （ on a dry matter （DM） basis） without supplementation （ G1 ） or supplemented with 5 and 10 g zinc methionine per head per day （G2 and G3, respectively）. Nutrient digestibility coefficients and nutritive values were significantly increased （P 〈0.05） by zinc methionine supplementation. Cows in G2 had the highest feed intake of total digestible nutrients （TDN） and digestible crude protein （DCP）, followed by Ga and G1, respectively （ P 〈 0.05 ）. The ruminal total volatile fatty acid concentration increased and ammonia nitrogen decreased significantly （ P 〈 0.05 ） by zinc methio-nine supplementation. Cows in G3 showed the highest plasma total protein, albumin, and globulin concen- trations （ P 〈 0.05 ）. Zinc methionine supplementa- tion led to significant decreases （ P 〈 0.05 ） in the activities of aspartate aminotransferase and alanine aminotransferase. A significant increase （ P 〈 0.05 ） was observed in the milk yield for G2 （2.54 kg/d or 18. 1% ） and G3 （ 1.95 kg/d or 14.2% ） compared with the control group. The corresponding increase in 4% fat-corrected milk （FCM） was 2.85 and 2.03 kg/d （21.63% and 15.74% ） for G2 and G3, respectively. Cows in G2 had the highest fat, total protein, and total solids contents, and the yield of all milk constitu- ents and animals in G3 showed the highest lactose, solids-not-fat, and ash contents. Zinc methionine sup- plementation improved feed conversion, reducing the quantities of DM, TDN, and DCP required to pro- duce 1 kg of 4% FCM （P〈0.05）. The average dai- ly feed cost per kilogram of 4% FCM decreased and the average income from milk production increased with zinc methionine supplementation （ P 〈 0.05 ）. Quadratic analysis showed that the optimal level of zinc methionine supplementation is 6 g per head per day in terms of milk yield and net revenue.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
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Twelve lactating Friesian Cows with body weight of 450 to 550 kg and in the second to fifth lactating season were used after 8 weeks of cal- ving in a complete switch-back design. The cows were fed a basal ration of 35% concentrate feed mix-ture with 40% berseem and 25% rice straw （ on a dry matter （DM） basis） without supplementation （ G1 ） or supplemented with 5 and 10 g zinc methionine per head per day （G2 and G3, respectively）. Nutrient digestibility coefficients and nutritive values were significantly increased （P 〈0.05） by zinc methionine supplementation. Cows in G2 had the highest feed intake of total digestible nutrients （TDN） and digestible crude protein （DCP）, followed by Ga and G1, respectively （ P 〈 0.05 ）. The ruminal total volatile fatty acid concentration increased and ammonia nitrogen decreased significantly （ P 〈 0.05 ） by zinc methio-nine supplementation. Cows in G3 showed the highest plasma total protein, albumin, and globulin concen- trations （ P 〈 0.05 ）. Zinc methionine supplementa- tion led to significant decreases （ P 〈 0.05 ） in the activities of aspartate aminotransferase and alanine aminotransferase. A significant increase （ P 〈 0.05 ） was observed in the milk yield for G2 （2.54 kg/d or 18. 1% ） and G3 （ 1.95 kg/d or 14.2% ） compared with the control group. The corresponding increase in 4% fat-corrected milk （FCM） was 2.85 and 2.03 kg/d （21.63% and 15.74% ） for G2 and G3, respectively. Cows in G2 had the highest fat, total protein, and total solids contents, and the yield of all milk constitu- ents and animals in G3 showed the highest lactose, solids-not-fat, and ash contents. Zinc methionine sup- plementation improved feed conversion, reducing the quantities of DM, TDN, and DCP required to pro- duce 1 kg of 4% FCM （P〈0.05）. The average dai- ly feed cost per kilogram of 4% FCM decreased and the average income from milk production increased with zinc methionine supplementation （ P 〈 0.05 ）. Quadratic analysis showed that the optimal level of zinc methionine supplementation is 6 g per head per day in terms of milk yield and net revenue.
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.
