The constitutive model was developed to describe the relationship among flow stress,strain,strain rate,and deformation temperature completely,based on the characteristics of flow stress curves for a new kind of metast...The constitutive model was developed to describe the relationship among flow stress,strain,strain rate,and deformation temperature completely,based on the characteristics of flow stress curves for a new kind of metastable β Ti2448 titanium alloy from isothermal hot compression tests,in a wide range of temperatures（1023-1123 K） and strain rates（63-0.001 s-1）.During this process,the adopted hyperbolic sine function based on the unified viscoplasticity theory was used to model the flow behavior of alloy undergoing flow softening caused by dynamic recovery（DRV） at high strain rates（≥1 s-1）.The standard Avrami equation was adopted to represent the softening mechanism attributed to dynamic recrystallization（DRX） at low strain rates（1 s-1）.Additionally,the material constants were determined by optimization strategy,which is a new method to solve the nonlinear constitutive equation.The stress—strain curves predicted by the developed constitutive model agree well with the experimental results,which con-rms that the developed constitutive model can give an accurate estimate of the-ow stress of Ti2448 titanium alloy and provide an effective method to model the flow behavior of metastable β titanium alloys during hot deformation.展开更多
There are many cracked concrete structures worldwide. Although there have been numerous efforts to eliminate cracks, some cracks are very harmful and should be repaired as soon as possible. On the other hand, some cra...There are many cracked concrete structures worldwide. Although there have been numerous efforts to eliminate cracks, some cracks are very harmful and should be repaired as soon as possible. On the other hand, some cracks are almost harmless. So, a good guideline regarding how to deal with cracks in concrete structures is needed. In this guideline, the practical investigation, repair and strengthening method of cracked concrete structures is discussed. And the detecting subjects are cracks generated immediately after casting and during the service time. This guideline targets on the owners （including managers） of concrete structure and the engineers working for the maintenance of concrete structure. JCI （Japan Concrete Institute） published first version of ＂Practical Guideline for Investigation and Repair of Cracked Concrete Structures＂ in 1980, and then the fourth version titled ＂Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures--2009＂ was published. This guideline is very practical when cracks are observed in existing concrete structures, in any other countries as well as in Japan. These three authors led the establishment of this guideline.展开更多
The development of steel bridges has been very strong for many years implementing composite structures, higher steel grades and hybrid girders, thus improving cost efficiency in bridge superstructures. As construction...The development of steel bridges has been very strong for many years implementing composite structures, higher steel grades and hybrid girders, thus improving cost efficiency in bridge superstructures. As construction moves more towards inner city, there is need for even more improvement. As global resources as scarce, and society in general expect more value for same money. With Constructional Excellence--a well defined process from steel mill to installed bridge which includes design management, new foundation solutions, the best practice of current steel bridges and intelligent installation put together in robust system solutions. This paper will show resource efficiency in three dimensions, money, time and less traffic disturbance.展开更多
文摘The constitutive model was developed to describe the relationship among flow stress,strain,strain rate,and deformation temperature completely,based on the characteristics of flow stress curves for a new kind of metastable β Ti2448 titanium alloy from isothermal hot compression tests,in a wide range of temperatures（1023-1123 K） and strain rates（63-0.001 s-1）.During this process,the adopted hyperbolic sine function based on the unified viscoplasticity theory was used to model the flow behavior of alloy undergoing flow softening caused by dynamic recovery（DRV） at high strain rates（≥1 s-1）.The standard Avrami equation was adopted to represent the softening mechanism attributed to dynamic recrystallization（DRX） at low strain rates（1 s-1）.Additionally,the material constants were determined by optimization strategy,which is a new method to solve the nonlinear constitutive equation.The stress—strain curves predicted by the developed constitutive model agree well with the experimental results,which con-rms that the developed constitutive model can give an accurate estimate of the-ow stress of Ti2448 titanium alloy and provide an effective method to model the flow behavior of metastable β titanium alloys during hot deformation.
文摘There are many cracked concrete structures worldwide. Although there have been numerous efforts to eliminate cracks, some cracks are very harmful and should be repaired as soon as possible. On the other hand, some cracks are almost harmless. So, a good guideline regarding how to deal with cracks in concrete structures is needed. In this guideline, the practical investigation, repair and strengthening method of cracked concrete structures is discussed. And the detecting subjects are cracks generated immediately after casting and during the service time. This guideline targets on the owners （including managers） of concrete structure and the engineers working for the maintenance of concrete structure. JCI （Japan Concrete Institute） published first version of ＂Practical Guideline for Investigation and Repair of Cracked Concrete Structures＂ in 1980, and then the fourth version titled ＂Practical Guideline for Investigation, Repair and Strengthening of Cracked Concrete Structures--2009＂ was published. This guideline is very practical when cracks are observed in existing concrete structures, in any other countries as well as in Japan. These three authors led the establishment of this guideline.
文摘The development of steel bridges has been very strong for many years implementing composite structures, higher steel grades and hybrid girders, thus improving cost efficiency in bridge superstructures. As construction moves more towards inner city, there is need for even more improvement. As global resources as scarce, and society in general expect more value for same money. With Constructional Excellence--a well defined process from steel mill to installed bridge which includes design management, new foundation solutions, the best practice of current steel bridges and intelligent installation put together in robust system solutions. This paper will show resource efficiency in three dimensions, money, time and less traffic disturbance.
