During molten salt cleaning of remanufactured 27SiMn hydraulic support column,oxidation occurs on the surface of metal substrate.This results in a change of the surface roughness of metal substrate after cleaning,whic...During molten salt cleaning of remanufactured 27SiMn hydraulic support column,oxidation occurs on the surface of metal substrate.This results in a change of the surface roughness of metal substrate after cleaning,which affects subsequent remanufacturing process.To decrease the effect is very important.This paper analyzed the oxidation mechanism of molten salt cleaning,explored the oxidation reaction that occurred during cleaning,and determined the key process parameters of cleaning that affecting oxidation reaction.By using central composite experimental design method and taking surface roughness variation of 27SiMn steel samples before and after molten salt cleaning as response variable to optimize the key process parameters,the optimal parameters of molten salt for cleaning remanufactured 27SiMn hydraulic support column could be obtained.The results show that the oxidation reaction of cleaning paint dirt can protect metal substrate from oxidation to a certain extent,and cleaning temperature and placement depth of metal substrate have a direct impact on the degree of oxidation reaction.When the cleaning temperature is 300℃and the distance between paint dirt and free surface of molten salt is 0.5 times the height of the parts,the surface roughness variation is minimal.Therefore,the cleaning quality will be improved under such parameters.展开更多
Static and dynamic force performance of two types of space truss structures i.e. square pyramid space truss（SPST） and diagonal on square pyramid space truss（DSPST）, are studied to determine the effect of stiffness...Static and dynamic force performance of two types of space truss structures i.e. square pyramid space truss（SPST） and diagonal on square pyramid space truss（DSPST）, are studied to determine the effect of stiffness of their lower supporting members. A simplified model for the supporting columns and the equivalent spring mass system are presented. Furthermore, the feasibility of the simplified model is demonstrated through theoretical analysis and examples of comparative analysis of the simplified model with the entire model. Meanwhile, from the elastic analysis under frequently occurring earthquakes and elasto-plastic analysis under seldom occurring earthquakes subjected to TAFT and EL-Centro seismic oscillation it is shown that the simplified method can be encompassed in the results from the normal model. It also showed good agreement between the two methods, as well as greatly improved the computational efficiency. This study verified that the dynamic effect of the supporting structures was under considered in space truss design in the past. The method proposed in the paper has important significance for other space truss structures.展开更多
Spherical pressure vessels in large sizes are generally supported on legs or columns evenly spaced around the circumference. The legs are attached at or near the equator of the sphere. This research work focussed on f...Spherical pressure vessels in large sizes are generally supported on legs or columns evenly spaced around the circumference. The legs are attached at or near the equator of the sphere. This research work focussed on flexural-torsional buckling of beam-column supports of field fabricated spherical pressure vessels using finite element analysis. Flexuraltorsional buckling is an important limit state that must be considered in structural steel design and it occurs when a structural member experiences significant out-of-plane bending and twisting. This research has therefore considered the total potential energy equation for the flexural-torsional buckling of a beam-column element. The energy equation was formulated by summing the strain energy and the potential energy of the external loads. The finite element method was applied in conjunction with the energy method to analyze the flexural-torsional buckling of beam-column supports. To apply the finite element method, the displacement functions are assumed to be cubic polynomials, and the shape functions used to derive the element stiffness and element geometric stiffness matrices. The element stiffness and geometric stiffness matrices were assembled to obtain the global stiffness matrices of the structure. The final finite element equation obtained was in the form of an eigenvalue problem. The flexural-torsional buckling loads of the structure were determined by solving for the eigenvalue of the equation. The resulting eigenvalue equation from the finite element analysis was coded using FORTRAN 90 programming language to aid in the analysis process. To validate FORTRAN 90 coding developed for the finite element analysis and the methodology, the results given by the software were compared to existing solutions and showed no significant difference P > 0.05.展开更多
基金supported by the National Natural Science Foundation of China(No.51375278)。
文摘During molten salt cleaning of remanufactured 27SiMn hydraulic support column,oxidation occurs on the surface of metal substrate.This results in a change of the surface roughness of metal substrate after cleaning,which affects subsequent remanufacturing process.To decrease the effect is very important.This paper analyzed the oxidation mechanism of molten salt cleaning,explored the oxidation reaction that occurred during cleaning,and determined the key process parameters of cleaning that affecting oxidation reaction.By using central composite experimental design method and taking surface roughness variation of 27SiMn steel samples before and after molten salt cleaning as response variable to optimize the key process parameters,the optimal parameters of molten salt for cleaning remanufactured 27SiMn hydraulic support column could be obtained.The results show that the oxidation reaction of cleaning paint dirt can protect metal substrate from oxidation to a certain extent,and cleaning temperature and placement depth of metal substrate have a direct impact on the degree of oxidation reaction.When the cleaning temperature is 300℃and the distance between paint dirt and free surface of molten salt is 0.5 times the height of the parts,the surface roughness variation is minimal.Therefore,the cleaning quality will be improved under such parameters.
基金National Technology Research and Development Program of the Ministry of Science and Technology of China under Grant No.2015BAK17B03National Natural Science Foundation of China(General Program)under Grant No.51278152
文摘Static and dynamic force performance of two types of space truss structures i.e. square pyramid space truss（SPST） and diagonal on square pyramid space truss（DSPST）, are studied to determine the effect of stiffness of their lower supporting members. A simplified model for the supporting columns and the equivalent spring mass system are presented. Furthermore, the feasibility of the simplified model is demonstrated through theoretical analysis and examples of comparative analysis of the simplified model with the entire model. Meanwhile, from the elastic analysis under frequently occurring earthquakes and elasto-plastic analysis under seldom occurring earthquakes subjected to TAFT and EL-Centro seismic oscillation it is shown that the simplified method can be encompassed in the results from the normal model. It also showed good agreement between the two methods, as well as greatly improved the computational efficiency. This study verified that the dynamic effect of the supporting structures was under considered in space truss design in the past. The method proposed in the paper has important significance for other space truss structures.
文摘Spherical pressure vessels in large sizes are generally supported on legs or columns evenly spaced around the circumference. The legs are attached at or near the equator of the sphere. This research work focussed on flexural-torsional buckling of beam-column supports of field fabricated spherical pressure vessels using finite element analysis. Flexuraltorsional buckling is an important limit state that must be considered in structural steel design and it occurs when a structural member experiences significant out-of-plane bending and twisting. This research has therefore considered the total potential energy equation for the flexural-torsional buckling of a beam-column element. The energy equation was formulated by summing the strain energy and the potential energy of the external loads. The finite element method was applied in conjunction with the energy method to analyze the flexural-torsional buckling of beam-column supports. To apply the finite element method, the displacement functions are assumed to be cubic polynomials, and the shape functions used to derive the element stiffness and element geometric stiffness matrices. The element stiffness and geometric stiffness matrices were assembled to obtain the global stiffness matrices of the structure. The final finite element equation obtained was in the form of an eigenvalue problem. The flexural-torsional buckling loads of the structure were determined by solving for the eigenvalue of the equation. The resulting eigenvalue equation from the finite element analysis was coded using FORTRAN 90 programming language to aid in the analysis process. To validate FORTRAN 90 coding developed for the finite element analysis and the methodology, the results given by the software were compared to existing solutions and showed no significant difference P > 0.05.
