Dynamic Performance Research Of Large-scale Crawler Cranes Boom-lifting Process

With the advantage of large lifting capability, low ground pressure, various ofboom combination ways and ability of driving with load, crawler crane is widely usedin a variety of large projects such as petrochemical, wind power, water conservancy andrailway construction projects. With the rapid development of national economicconstruction, more and more large-scale construction work need to be done, which needto transport goods with greater weight and volume to higher lifting height. In that case,the large-scale crawler crane’s advantage is more outstanding in the way of lifting goodswith large weight, volume and lifting height. The crawler crane market is booming forthe increasing demand for large-scale crawler cranes in domestic market.Due to the rapid development of large-scale projects, it’s an inevitable trend forcrawler cranes to development direction of large weight and high lifting-height. We’dlike to increase the boom length or take the combination of main boom and the jib toobtain higher lifting height and greater operating range with high performance. Theconnected joint between the bottom boom section and the turntable is high from theground, while the boom head is placed on the ground before the boom-lifting process.The boom will produce flexible with part of it placing on the ground under its ownweight. In the process of boom-lifting, the luffing ropes are stretched, and it will applyan axial component of force to the boom, which will exacerbate deformation of theboom. Nonlinear effect is obvious for long boom, and in that case, axial force on theboom will increase dramatically, which will cause the instability of the boom andresulting the boom damage.The longer the boom is, the more dangerous the boom-lifting process is. We take alarge-scale crawler crane of XCMG as a model, and take the boom combination of lightmain boom, light main boom with superlift and luffing fly jib with superlift as the studyobjects. And do the static and dynamic analysis of the boom-lifting process.This paper is based on the finite element analysis software named ANSYS. Weselect the appropriate element type to modeling the basic boom sections and assemblethem together by using the special APDL language provided by ANSYS. Settingsupporting rods at the joint between different boom sections in the symmetrical positionto modelling the mechanotheropy of ground support the boom. We select the element type of LINK10to simulate the derricking pulling board. Making use of its deformationcharacter under temperature loads, the length of the element will be shortened by aconstant speed. If we set appropriate linear expansion coefficient and the temperatureloads, the boom head will be pulled up. In this paper, we have solved the problem ofdefining load steps by taking the method of deformation constraint instead of thecommon load-constraint method, as the value and direction of the pull-plate forcechange all the time when we simulate the boom lifting process.Use the static calculation module of ANSYS to do static analysis of the boom in allangles. Extract the main chord axial forces in all boom angles and fit a curve. Then,extract the extreme value of the main chord axial stresses and compared them with itsallowable stress limits to confirm the operating condition’s degree of safety. The resultcan be the reference for the subsequent transient analysis.The ANSYS structural dynamic analysis module contains the submodule oftransient analysis, what can model the crawler crane’s dynamic boom-lifting process.By setting different boom-lifting time and doing transient analysis, we can get differentTimeHist Curves of the main chords at different cross sections. If the limits of the mainchord axial stresses are under the allowable stress limits, we take the lifting time as thesafety boom-lifting time. Then, we optimize the boom-lifting way of the boomcombination of light main boom with superlift, who’s boom-lifting time is very long, toshorten its boom-lifting time.At last, we carried out a stress test for the boom-lifting process of the boomcombination of main boom of QUY70to verify the correctness of the calculationmethod of this paper. Sampling the dynamic strain data for the boom-lifting processtrough the dynamic strain gauge and doing the data processing. Then, compare the testdata with the static and transient analysis results to verify the correctness of thecalculation methods.In this paper, we have modeled dynamic boom-lifting process of large-scalecrawler cranes, and putted forward the method of simulate the boom partly supported bythe ground as well as control the boom-lifting process by temperature loads, whatprovide a new ideal of the boom-lifting process controlling methods. And we have alsoverified the correctness of this method, and the results can be references for the actualdesign and the boom-lifting debugging processes of the cranes.