A three-dimensional finite element analysis of process-induced residual stress in resin transfer molding (RTM) process is presented. The finite element method (FEM) was employed to solve the coupled equations involved...A three-dimensional finite element analysis of process-induced residual stress in resin transfer molding (RTM) process is presented. The finite element method (FEM) was employed to solve the coupled equations involved in the transient heat transfer and the cure kinetics of the resin, and the distributions of internal temperature and cure degree of the composite at any instant time were obtained. The self-consistent field micro-mechanics model was used to predict the cure-dependent mechanical properties of the composites. Thermal expansion and cure shrinkage were included in the analysis. The thermo-elastic mechanical governing equations were solved using the incremental stress-strain relationship based FEM and the residual stress development was predicted. The present results were validated by the comparisons with the pertinent literature. The numerical example of a half cylinder was presented. The results show that it is necessary to carry out the three-dimensional analysis due to the complex distributions of temperatures, cure degrees and process-induced stress for thick parts, which can be predicted at any point within composite structures in the present analysis.展开更多
This Article presents a three dimensional numerical model investigating thermal performance and hydrodynamics features of the confined slot jet impingement using slurry of Nano Encapsulated Phase Change Material(NEPCM...This Article presents a three dimensional numerical model investigating thermal performance and hydrodynamics features of the confined slot jet impingement using slurry of Nano Encapsulated Phase Change Material(NEPCM)as a coolant.The slurry is composed of water as a base fluid and n-octadecane NEPCM particles with mean diameter of 100 nm suspended in it.A single phase fluid approach is employed to model the NEPCM slurry.The thermo physical properties of the NEPCM slurry are computed using modern approaches being proposed recently and governing equations are solved with a commercial Finite Volume based code.The effects of jet Reynolds number varying from 100 to 600 and particle volume fraction ranging from 0% to 28% are considered.The computed results are validated by comparing Nusselt number values at stagnation point with the previously published results with water as working fluid.It was found that adding NEPCM to the base fluid results with considerable amount of heat transfer enhancement.The highest values of heat transfer coefficients are observed at H/W=4 and C_m=0.28.However,due to the higher viscosity of slurry compared with the base fluid,the slurry can produce drastic increase in pressure drop of the system that increases with NEPCM particle loading and jet Reynolds number.展开更多
As the size of the electronic system continuously reduces, characteristics of small volume, light weight, high energy it is very important to develop micro power generator, which has density and continuous energy supp...As the size of the electronic system continuously reduces, characteristics of small volume, light weight, high energy it is very important to develop micro power generator, which has density and continuous energy supplying. Vibration energy exists widely in daily environment. Micro vibration power generator can harvest and exchange the vibration energy to the electrical energy. Micro electret power generator is one kind of the power generators for harvesting vibration energy and has been paid much attention by researchers. This paper describes the development and status of micro electret power generators, including electret materials and charging methods, vibration energy harvesting structures and conversion efficiency improvement.展开更多
基金the National Natural Science Foundation of China(Grant No.10502016)Development Program for Outstanding Young Teachers in Harbin Institute of Technology(Grant No.HITQNJS.2006.020)
文摘A three-dimensional finite element analysis of process-induced residual stress in resin transfer molding (RTM) process is presented. The finite element method (FEM) was employed to solve the coupled equations involved in the transient heat transfer and the cure kinetics of the resin, and the distributions of internal temperature and cure degree of the composite at any instant time were obtained. The self-consistent field micro-mechanics model was used to predict the cure-dependent mechanical properties of the composites. Thermal expansion and cure shrinkage were included in the analysis. The thermo-elastic mechanical governing equations were solved using the incremental stress-strain relationship based FEM and the residual stress development was predicted. The present results were validated by the comparisons with the pertinent literature. The numerical example of a half cylinder was presented. The results show that it is necessary to carry out the three-dimensional analysis due to the complex distributions of temperatures, cure degrees and process-induced stress for thick parts, which can be predicted at any point within composite structures in the present analysis.
基金supported by the National Natural Science Foundation of China(No.51322604)
文摘This Article presents a three dimensional numerical model investigating thermal performance and hydrodynamics features of the confined slot jet impingement using slurry of Nano Encapsulated Phase Change Material(NEPCM)as a coolant.The slurry is composed of water as a base fluid and n-octadecane NEPCM particles with mean diameter of 100 nm suspended in it.A single phase fluid approach is employed to model the NEPCM slurry.The thermo physical properties of the NEPCM slurry are computed using modern approaches being proposed recently and governing equations are solved with a commercial Finite Volume based code.The effects of jet Reynolds number varying from 100 to 600 and particle volume fraction ranging from 0% to 28% are considered.The computed results are validated by comparing Nusselt number values at stagnation point with the previously published results with water as working fluid.It was found that adding NEPCM to the base fluid results with considerable amount of heat transfer enhancement.The highest values of heat transfer coefficients are observed at H/W=4 and C_m=0.28.However,due to the higher viscosity of slurry compared with the base fluid,the slurry can produce drastic increase in pressure drop of the system that increases with NEPCM particle loading and jet Reynolds number.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2009CB320300)
文摘As the size of the electronic system continuously reduces, characteristics of small volume, light weight, high energy it is very important to develop micro power generator, which has density and continuous energy supplying. Vibration energy exists widely in daily environment. Micro vibration power generator can harvest and exchange the vibration energy to the electrical energy. Micro electret power generator is one kind of the power generators for harvesting vibration energy and has been paid much attention by researchers. This paper describes the development and status of micro electret power generators, including electret materials and charging methods, vibration energy harvesting structures and conversion efficiency improvement.
