Fatigue Behavior of a Box-Type Welded Structure of Hydraulic Support Used in Coal Mine
Hydraulic support is the main supporting equipment of the coal mining systems, and they are usually subjected to fatigue failure under the high dynamic load. The fracture positions are generally at welded joints where there is a serious stress concentration. In order to investigate and further improve the fatigue strength of hydraulic support, the present work first located the possible position where fatigue failure occurs through finite element analysis, and then fatigue tests were carried out on the different forms of welded joints for the dangerous parts. Finally, Fatigue strength-life (S-N) curves and fracture mechanism were studied. This research will provide a theoretical reference for the fatigue design of welded structures for hydraulic support.
Hydro-Pneumatic Suspension System Hybrid Reliability Modeling Considering the Temperature Influence
Hydro-pneumatic suspension systems have been widely used in many fields for their variable stiffness characteristics that effectively improve the comfort and operation stability of a vehicle. However, due to poor environmental conditions, hydro-pneumatic suspension is frequently subjected to the influence of transient impact and environmental temperature changes, which results in sealing failure and gas leakage problems and reduces the reliability of the system. In this paper, a method combining parametric modeling and probability analysis is adopted to establish the reliability model of a hydro-pneumatic suspension system considering the influence of temperature variations. First, the working principle and failure mode of the hydro-pneumatic suspension system are analyzed, and then the reliability of the hydro-pneumatic suspension system is defined. On this basis, for the key failure modes of the hydro-pneumatic suspension system, a reliability model based on the allowable height and a reliability model based on the allowable stiffness are established. The system reliability model of the hydro-pneumatic suspension system is obtained synthetically. Finally, the single-chamber hydro-pneumatic suspension system is selected as the experimental object. Comparative tests of different design parameters of the hydro-pneumatic suspension system under temperature effect are conducted. The accuracy is verified for the failure mode analysis and reliability model of the hydro-pneumatic suspension system.
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.