Theoretical Analysis and Numerical Simulation of Dynamic Characteristics of Hydrostatic Guides for Heavy NC Machine Tool
Based on analysis of hydrostatic bearing with circular pocket, equations of static pressure, volvme pressure and squeezing pressure which influence dynamic characteristics of hydrostatic guides with rectangle pocket have been deduced. The function and their influencing factors of the three kinds pressure mentioned above are clarified. The amplitude-phase-frequency characteristics of the hydrostatic guides system have been analyzed qualitatively and quantitatively, it is indicated that the sensitive oil volume has greater effect on the stability of the guide, the volume should be reduced as small as possible while the hydrostatic guides meet the needs of the field working situation. To increasing the oil visosity properly is also helpful to improve the dynamic performance of hydrostatic guides.
Dynamic Properties Analysis of the Hybrid Journal Bearing in Machine Tools
The dynamic characteristics of the hybrid journal bearing under step load were analyzed and some calculations were done.Some viewpoints were raised when choosing the parameters of hybrid journal bearing.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.