| With the constant development of Chinese society,the demand for fossil energy is increased;therefore,by virtue of unique characteristics,pipeline transportation stands out from numerous transportation modes.Since pipelayer is a professional machine that is exclusively applied to pipeline construction,can lift heavy pipeline and walks with load,its special status is becoming more prominent.Throughout global pipelayer market,the corporations accounting for larger share are US Caterpillar,Japan Komatsu and Poland Dresser;the products manufactured by these foreign corporations are in complete specifications,which basically meet various operating demands with lifting mass at 18t-130 t.However,the pipelayer industry starts relatively late,and the pipelayers manufactured by domestic corporations mostly are the small and medium sized pipelayers with lifting mass at 18t-130 t.Nevertheless,the large-scale pipelayers with lifting mass above 70 t are immature.This paper originates from Shanghai Alliance Plan Subsidy Program.Taking the DG70 crawler crane pipelayer actually manufactured by certain company as prototype,started with the actual problems encountered by enterprises when manufacturing and using pipelayer,replying on university technological advantages in design and simulation optimization,it jointly enhances the overall performance of pipelayer.Before that,aimed at the problems of DG70 pipelayer caused by lifting operation with derricking cylinder driving crane jib,such as poor stability(lower wind resistance shaking force)and smaller crane jib amplitude variation angle,it has been optimized into the working mode using winch to make crane jib change amplitude,which increased crane jib amplitude variation angle,enhanced stability of wind resistance shaking force,and reduced pipelayer production cost.Since the change of structure in crane jib side destroyed balance of complete machine,it is necessary to optimize counterweight system again to guarantee the stability.The most serious accident in crawler crane pipelayer is “turnover”,which is fundamentally caused by the stability lose of complete machine;it is necessary to check the corresponding crane design manual for stability parameter.When lifting and walking,pipelayer maintains balance completely by mechanical self weight,so counterweight system plays the vital role.The calculation of counterweight mass shall consider limiting conditions,which are that the counterweight completely spreads when crane jib is empty and counterweight not completely spreads when in full load.Only the maximum value of counterweight mass determined in this way can guarantee that,pipelayer will not generate overturn due to stability lose caused by misoperation,poor operation condition or other reasons.The major research contents and achievements are as follows:(1)Under the condition of reasonable optimal weight reduction in crane jib side,taking the crawler center closer to crane jib side as overturn point,the calculation of counterweight mass required by complete machine is implemented again with method of moment,which obtained the counterweight mass.Meanwhile,by referring to crane design standard Moverturn/ Mstability<0.78,the stability calculation of complete machine is carried out.(2)The mapping and motion analysis of counterweight mechanism are implemented firstly,then,the calculation and type selection of counterweight oil cylinder of counterweight mechanism are conducted,the simulation result indicated that the oil cylinder which is after optimization can be used on counterweight structure,and drive by the cylinder,the counterweight structure can spread and withdraw stably under the drive of hydraulic cylinder.(3)The pipelayer 3D model is imported into ADAMS software with imposing constraint relation.Meanwhile,hydraulic circuit is established in AMEsim software to define the parameters related to counterweight oil cylinder and hydraulic oil pump.The relevance between ADAMS software and AMEsim software is utilized for joint simulation,by means of which,the conclusion that the centroidal displacement meets the anti-overturn requirement calculated by theoretical mechanics is obtained;the cylinder strength of hydraulic ram meets the demands of working stress;the flow relationship between rodless chamber and rod chamber in counterweight cylinder is acquired,which meets the operating demand of counterweight mechanism;during the process of spreading and withdrawing counterweight mechanism,the point and position of maximum stress in larger and smaller rocker arms are summarized.The results verify the feasibility of optimized counterweight system design and offer reference value for similar product structure optimization.(4)The maximum stresses of larger rocker arm and smaller rocker arm are acquired by extracting joint simulation and combining with stress experimental data,Ansys workbench is adopted for analyzing larger and smaller rocker arms respectively;based on central composite algorithm and taking weight as target,the structural optimization of larger and smaller rocker arms is carried out,and the most appropriate size parameters of larger and smaller rocker arms are concluded. |
