Virtual vibration test rig for fatigue analysis of dozer push arms

To obtain accurate fatigue life results for construction machinery components,acquiring load spectra is crucial,as their authenticity and validity directly determine the precision of the analysis.In working conditions,component attitudes change continuously,but they remain static on the vibration test rig(VTR),so the acquired target signals should match with the actual component attitudes in the driving signal generation.This paper proposes an efficient and economical simulation-based virtual VTR for fatigue analysis of dozers.First,the relationship between the push arm rotation angle and the cylinder stroke is established,since the cylinder strokes can be measured easily in data acquisition experiments.Second,load decomposition is used to determine the attitude relationship between virtual VTR conditions and actual conditions,and target signals are calculated based on this attitude relationship and measured data.According to the system's frequency response function,the driving signals are iterated until the system's response signals converge with the target signals.Finally,the iteratively obtained load spectra are utilized for fatigue life analysis.The results show that the virtual VTR can effectively and accurately obtain the results of fatigue analysis and has engineering application significance.

Quantitatively assessing the pre-grouting effect on the stability of tunnels excavated in fault zones with discontinuity layout optimization:A case study

Pre?grouting is a popular ground treatment strategy utilized to enhance the strength and stability of strata during the excavation of a tunnel through a fault zone.Two important questions need to be answered during such an excavation.First,how should the grouting size be determined?Second,when should excavation begin after grouting?These two questions are conventionally addressed through empirical experience and standard criteria because a reliable quantitative approach,which would be preferable,has not yet been developed.To address these questions,we apply a recently proposed numerical approach known as discontinuity layout optimization,an efficient node-based upper bound limit analysis method.A case study is provided utilizing a tunnel located in a stratum characterized by complicated geological conditions,including soft soil and a fault zone.The factor of safety is used to quantitatively assess the stability of the tunnel section.The influences of the grouted zone thickness and the time-dependent material properties of the grouted zone on the stability of the tunnel section are evaluated,thereby assisting designers by quantitatively assessing the effects of pre-grouting.