Manufacturing of composite materials is usually accompanied with residual stresses.These stresses should be evaluated and assessed.To this end,a micromechanical model for periodic material whose temperature dependent ...Manufacturing of composite materials is usually accompanied with residual stresses.These stresses should be evaluated and assessed.To this end,a micromechanical model for periodic material whose temperature dependent constituents behave as thermorheologically complex materials(TCM)has been developed.This model,referred as the high fidelity generalized method of cells(HFGMC),takes into account the detailed interaction between the fiber and resin,their volume ratios,the fibers distribution and their waviness.This model is linked,in conjunction with a special UMAT subroutine,to the ABAQUS finite element code for prediction of the response of thermoviscoelastic composite structures during cool down process.The present investigation shows the effect of the cool down rate on the residual stress developed in the composite cylindrical structures.展开更多
Between the 1940s and the 1960s there was a significant lowering of the surface temperatures of the central North Pacific. This cool-down is discussed on the basis of analyses of a very large surface temperature data ...Between the 1940s and the 1960s there was a significant lowering of the surface temperatures of the central North Pacific. This cool-down is discussed on the basis of analyses of a very large surface temperature data base, covering most of the North Pacific, which began in 1947 and continued for at least 30 years afterwards. A surface area more than 20 degrees of latitude by approximately 70 degrees of longitude, centered on 40°N, cooled down within about a ten year period by typically 0.5℃ and by as much as 1.0℃. Previously a permanent surface and near surface circulation was proposed in which a shallow very broad warm surface layer flows northeastward at mid-latitudes on the eastern side of the North Pacific while colder water returns southward to the east, west and underneath the warm surface current. It is suggested that variations in this hypothesized circulation, due to natural causes not yet completely understood, potentially provide a mechanism for producing a cooling down (or warming up) of a large region of the central North Pacific at mid-latitudes in a relatively short period of time (ten years or less).展开更多
文摘Manufacturing of composite materials is usually accompanied with residual stresses.These stresses should be evaluated and assessed.To this end,a micromechanical model for periodic material whose temperature dependent constituents behave as thermorheologically complex materials(TCM)has been developed.This model,referred as the high fidelity generalized method of cells(HFGMC),takes into account the detailed interaction between the fiber and resin,their volume ratios,the fibers distribution and their waviness.This model is linked,in conjunction with a special UMAT subroutine,to the ABAQUS finite element code for prediction of the response of thermoviscoelastic composite structures during cool down process.The present investigation shows the effect of the cool down rate on the residual stress developed in the composite cylindrical structures.
文摘Between the 1940s and the 1960s there was a significant lowering of the surface temperatures of the central North Pacific. This cool-down is discussed on the basis of analyses of a very large surface temperature data base, covering most of the North Pacific, which began in 1947 and continued for at least 30 years afterwards. A surface area more than 20 degrees of latitude by approximately 70 degrees of longitude, centered on 40°N, cooled down within about a ten year period by typically 0.5℃ and by as much as 1.0℃. Previously a permanent surface and near surface circulation was proposed in which a shallow very broad warm surface layer flows northeastward at mid-latitudes on the eastern side of the North Pacific while colder water returns southward to the east, west and underneath the warm surface current. It is suggested that variations in this hypothesized circulation, due to natural causes not yet completely understood, potentially provide a mechanism for producing a cooling down (or warming up) of a large region of the central North Pacific at mid-latitudes in a relatively short period of time (ten years or less).
