Optimization of Molten Salt Cleaning Process for Surface Roughness of Remanufactured 27SiMn Hydraulic Support Column

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.

Simplified design method and seismic performance of space trusses with consideration of the influence of the stiffness of their lower supporting columns

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.