Quality assessment of friction-stir-welded aluminum alloy welds via three-dimensional force signals

An online detection technology must be developed for realizing the real-time control of friction stir welding.In this study,the three-dimensional force exerted on a material during friction stir welding was collected synchronously and the relationship between the forces and welding quality was investigated.The results indicated that the fluctuation period of the traverse force was equal to that of the lateral force during the stable welding stage.The phase difference between two horizontal forces wasπ/2.The values of the horizontal forces increased with welding speed,whereas their amplitudes remained the same.The proposed force model showed that the traverse and lateral forces conformed to an elliptical curve,and this result was consistent with the behavior of the measured data.The variational mode decomposition was used to process the plunge force.The intrinsic mode function that represented the real fluctuation in the plunge force varied at the same frequency as the spindle rotational speed.When tunnel defects occurred,the fluctuation period features were consistent with those obtained during normal welding,whereas the ratio parameter defined in this study increased significantly.

Civil gas energy accidents in China from 2012-2021

In this study,civil gas energy accidents reported by the China Gas Network and related organizations from 2012 to 2021 were collected,and a comprehensive multidimensional correlation analysis was conducted considering factors such as accident timing,geography,causes,and casualties.The results identified July and August,Mondays and Sundays,and the morning,mid-day,and evening cooking times as the high-incidence months,days,and times for gas accidents,respectively.Gas accidents were found to occur more frequently in eastern coastal areas,provincial capitals,and larger cities,while residential and construction sites were identified as high-risk areas for gas accidents.Explosions were the most prevalent type of gas accident,followed by leaks,fires,and poisoning.Third-party construction and valve issues were identified as the primary factors contributing to gas leakage,whereas cooking was identified as the most common ignition source.An analysis of the Pearson correlation coefficient indicated a significant correlation among the gas accident factors.Moreover,a time-series prediction model was developed to forecast gas accidents in China,with the results demonstrating fluctuating gas accidents.This study proposes targeted preventive measures in terms of publicity,education,equipment,and facilities to provide scientific support to government units to improve civil gas energy security measures.