Magnesium(Mg)alloys despite being the ideal candidate for structural applications,owing to their high specific strength and low density,are not widely used due to lack of active slip systems at room temperature in the...Magnesium(Mg)alloys despite being the ideal candidate for structural applications,owing to their high specific strength and low density,are not widely used due to lack of active slip systems at room temperature in their hexagonal close-packed crystal structure,eliciting poor ductility and formability.Amongst the various series of Mg alloys,the AZ and ZK series alloys have been standouts,as they inherit better room temperature strength and flow characteristics through their solute elements.Grain refinement,as well as eliminating casting defects through metal processing techniques are vital for the commercial viability of these alloys since they play a key role in controlling the mechanical behaviour.As such,this review highlights the effect of different Bulk-deformation and Severe Plastic Deformation techniques on the crystal orientation and the corresponding mechanical behaviours of the AZ31 alloy.However,every process parameter surrounding these techniques must be well thought of,as they require specially designed tools.With the advent of finite element analysis,these processes could be computationally realized for different parameters and optimized in an economically viable manner.Hence,this article also covers the developments made in finite element methods towards these techniques.展开更多
For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200 mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching proces...For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200 mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching processes of AISI P20 steel block such as oil quenching, direct water quenching, water quenching with precooling and water quenching with pre-cooling and self-tempering were numerically investigated by computer simulation based on the detailed discussion on the mathematical models of quenching processes including partial differential equations of heat transfer, thermal physical properties, latent heat, heat transfer coefficient and calculation of phase transformation, The results show that the water quenching with pre-cooling and self-tempering process can not only effectively avoid quenching cracks, but also obtain deeper harden depth than oil quenching.展开更多
A mathematical model that described the strains growth, product formation and medium consumption was presented to predict the performance of batch fermentation of Zoogloea sp.GY3 which was screened from activated slud...A mathematical model that described the strains growth, product formation and medium consumption was presented to predict the performance of batch fermentation of Zoogloea sp.GY3 which was screened from activated sludge and could synthesize PHAs.A simple model was proposed by using the Logistic equation for growth, the Luedeking-Piret equation for PHAs production and the Luedeking-Piret-like equation for sucrose consumption.The model appeared to provide a reasonable description for each parameter during the growth phase.The production of PHAs was growth-associated.The models were in good agreement with the measured data in experiments.展开更多
文摘Magnesium(Mg)alloys despite being the ideal candidate for structural applications,owing to their high specific strength and low density,are not widely used due to lack of active slip systems at room temperature in their hexagonal close-packed crystal structure,eliciting poor ductility and formability.Amongst the various series of Mg alloys,the AZ and ZK series alloys have been standouts,as they inherit better room temperature strength and flow characteristics through their solute elements.Grain refinement,as well as eliminating casting defects through metal processing techniques are vital for the commercial viability of these alloys since they play a key role in controlling the mechanical behaviour.As such,this review highlights the effect of different Bulk-deformation and Severe Plastic Deformation techniques on the crystal orientation and the corresponding mechanical behaviours of the AZ31 alloy.However,every process parameter surrounding these techniques must be well thought of,as they require specially designed tools.With the advent of finite element analysis,these processes could be computationally realized for different parameters and optimized in an economically viable manner.Hence,this article also covers the developments made in finite element methods towards these techniques.
文摘For large-sized AISI P20 steel block used as plastic die with a thickness of more than 200 mm, appropriate quenching processes are the key to obtain much thick hardened layer. In this paper, different quenching processes of AISI P20 steel block such as oil quenching, direct water quenching, water quenching with precooling and water quenching with pre-cooling and self-tempering were numerically investigated by computer simulation based on the detailed discussion on the mathematical models of quenching processes including partial differential equations of heat transfer, thermal physical properties, latent heat, heat transfer coefficient and calculation of phase transformation, The results show that the water quenching with pre-cooling and self-tempering process can not only effectively avoid quenching cracks, but also obtain deeper harden depth than oil quenching.
文摘A mathematical model that described the strains growth, product formation and medium consumption was presented to predict the performance of batch fermentation of Zoogloea sp.GY3 which was screened from activated sludge and could synthesize PHAs.A simple model was proposed by using the Logistic equation for growth, the Luedeking-Piret equation for PHAs production and the Luedeking-Piret-like equation for sucrose consumption.The model appeared to provide a reasonable description for each parameter during the growth phase.The production of PHAs was growth-associated.The models were in good agreement with the measured data in experiments.
