Study On Fatigue Life Analysis And Lightweight Of Construction Machinery Wheel

Construction machinery wheel is an important transmission component of construction machinery,its structural strength directly affects the safety and stability of the whole machine.As a kind of typical welding structure,the construction machinery wheel contains many different kinds of welding seams.In the process of wheel cornering and radial fatigue test,the welding seam is subjected to large disturbance stress,and the stress concentration at the weld toe is easy to initial crack and expand rapidly,which eventually leads to wheel fatigue fracture,thus the fatigue analysis of welding seams cannot be ignored.In order to study the effect of welding seams fatigue on the cornering and radial fatigue life of wheel,this paper takes a certain type of construction machinery wheel as the research object.Firstly,the 3D solid model of the construction machinery wheel which including weld seams is established by using the reverse engineering technique,and then set up the wheel cornering and radial fatigue analysis of finite element model,the static analysis of the wheel is carried out;secondly,combined with the static stress analysis results,choose the nominal stress method to analyze the fatigue of wheel,especially for the weld zone of wheel,two kinds of standard are raised to evaluate the fatigue of weld zone,Code of practice for fatigue design and assessment of steel structures BS7608:1993 and International Institute of Welding Recommendations for fatigue design of welded joints and components;finally,contrasted the cornering and radial fatigue life of wheel attached weld seams and the wheel that doesn't attached weld seams,the results shows that for the evaluation of fatigue life of a same weld seam,the IIW standard is more conservative than the BS7608:1993 standard;the most dangerous position of wheel cornering fatigue is the fillet weld seam of rim and disc,and the minimum life is 406,000 times;the most dangerous position of wheel radial fatigue is the girth weld seam of the middle and lower segment of the rim,and the minimum life is 4,102,000 times.In order to verify the correctness of cornering simulation,the wheel cornering fatigue test is carried out,the test results show that the fatigue crack of the wheel is produced at the fillet weld seam of rim and disc,which is consistent with the simulation results;in order to find out the possibility of wheel radial fatigue,the Goodman fatigue limit diagram was used to evaluate the radial fatigue risk point.The results show that the stress of fatigue dangerous point is within the range of Goodman curve,and there is a great quantity of optimization space.According to the results of construction machinery wheel cornering and radialfatigue life analysis,the wheel cornering fatigue life is up to the requirements of national standard,but the radial fatigue life value is far more than the standard value100,000 times,therefore,under the condition of radial fatigue test,the wheel structure has a large potential for optimization.As the middle segment of rim thickness is 8mm,the lower segment of rim and the retaining seat thickness is 11 mm,after the welding connection of middle and lower segment of rim,there is a great stress concentration at the weld seam,in order to reduce the influence of stress concentration on the fatigue life of wheel,the optimization of lower segment of rim and retaining seat are considered,but the shape of the wheel is relatively fixed,so the optimization scheme is to optimize the size of these two components.Firstly,size optimization of the finite element model of the wheel is established,then use the element thickness of lower segment of rim and retaining seat as optimization design variables,weights as objective function,displacement as constraint conditions to optimize,the optimization results show that the thickness of the lower segment of rim and the retaining seat is changed from 11 mm to 9mm.secondly,the cornering and radial fatigue life of the wheel after lightweight design is analyzed,the calculation results shows that the most dangerous position of wheel cornering fatigue is the fillet weld seam of rim and disc,and the minimum life is 439,000 times;the most dangerous position of wheel radial fatigue is the girth weld seam of the middle and lower segment of the rim,and the minimum life is 2,178,000 times,both of the cornering and radial fatigue life meets the requirements of national standard.Lastly,the simulation results are verified by fatigue test.