In the last few years,substantial experimental simulation and mumerical modelling hare been carried out in IMMPETUS to characterise the interfacial heat transfer and friction conditions during hot forging and rolling ...In the last few years,substantial experimental simulation and mumerical modelling hare been carried out in IMMPETUS to characterise the interfacial heat transfer and friction conditions during hot forging and rolling of steels. Emphasis has been placed on the influence of the oxide scale which forms on the steel workpiece. In the present paper, the experimental methods used for investigating interfacial heat transfer and friction conditions are described. Theses include hot flat rolling of steel slabs and hot axi- symmetric forging of steel cylinders and rings.Temperature measurements and computations demon- strate that for similar conditions, similar conditions, the effective interfacial heat transfer coefficients (IHTC) derived for hot rolling are significantly higher than those for forging, mainly due to the contribution of scale cracking during rolling. On the basis of experimental observations and numerical analysis,physical models for interfacial heat transfer in forging and rolling have been established. In addition, hot' sandwich' rolling and hot tensile tests with finite element modelling have been carried out to evaluate the hot ductility of the oxide scale.The results indicate that the defomation, cracking and decohesion behaviour of the oxide scale depend on deformation temperature, strain and relative strengths of the scale layer and scale - steel interface.Finaly, friction results from hot ring compression tests and from hot rolling with forward/backward slip measurements are reported.展开更多
The real in time computerized tomography (CT) testing of the meso damage propagation law of the whole sandstone failure process under triaxial compression has been completed using the newest specified triaxial loading...The real in time computerized tomography (CT) testing of the meso damage propagation law of the whole sandstone failure process under triaxial compression has been completed using the newest specified triaxial loading equipment corresponding to the CT machine. Through the CT scanning, the clear CT images which include from the microcracks compressed stage to growth stage, bifurcation stage, development stage, crack fracture stage,the rock sample failure until to unloading stage in the different stress states were obtained. The CT values, CT images and the other data have been analyzed. Based on the results of the CT testing of meso damage evolution law of rock,the stress threshold value of meso damage of rock is given, and the stress strain complete process curve of rock is divided into some sections. The initial rock damage propagation law is given in this paper.展开更多
文摘In the last few years,substantial experimental simulation and mumerical modelling hare been carried out in IMMPETUS to characterise the interfacial heat transfer and friction conditions during hot forging and rolling of steels. Emphasis has been placed on the influence of the oxide scale which forms on the steel workpiece. In the present paper, the experimental methods used for investigating interfacial heat transfer and friction conditions are described. Theses include hot flat rolling of steel slabs and hot axi- symmetric forging of steel cylinders and rings.Temperature measurements and computations demon- strate that for similar conditions, similar conditions, the effective interfacial heat transfer coefficients (IHTC) derived for hot rolling are significantly higher than those for forging, mainly due to the contribution of scale cracking during rolling. On the basis of experimental observations and numerical analysis,physical models for interfacial heat transfer in forging and rolling have been established. In addition, hot' sandwich' rolling and hot tensile tests with finite element modelling have been carried out to evaluate the hot ductility of the oxide scale.The results indicate that the defomation, cracking and decohesion behaviour of the oxide scale depend on deformation temperature, strain and relative strengths of the scale layer and scale - steel interface.Finaly, friction results from hot ring compression tests and from hot rolling with forward/backward slip measurements are reported.
基金FundofStateKeyLaboratoryofFrozenSoilEngineeringofChina !(No 980 2 No 2 0 0 3 )
文摘The real in time computerized tomography (CT) testing of the meso damage propagation law of the whole sandstone failure process under triaxial compression has been completed using the newest specified triaxial loading equipment corresponding to the CT machine. Through the CT scanning, the clear CT images which include from the microcracks compressed stage to growth stage, bifurcation stage, development stage, crack fracture stage,the rock sample failure until to unloading stage in the different stress states were obtained. The CT values, CT images and the other data have been analyzed. Based on the results of the CT testing of meso damage evolution law of rock,the stress threshold value of meso damage of rock is given, and the stress strain complete process curve of rock is divided into some sections. The initial rock damage propagation law is given in this paper.
