Lightweight Design Of Lower Part Of Crawler Crane And Study On Buckling Stability Of Truss Arm

Crane is one of the most important mechanical equipment in the process of Urbanization.Especially,the crawler crane is quickly favored by the market for its advantages of less ground pressure,big lifting capacity,higher operation height and large steering range,no lifting weight and carrying capacity.There are two major problems in crane products at present.The first problem is that the size and weight of the crawler crane are increasing with the increase of the lifting capacity of the product,thus leading to a substantial increase in production costs,transportation costs,and usage costs and a decline in market competitiveness.Secondly,the truss arm structure will occur buckling failure during the working process,and such damage had no sign of happening before it happened,however,The consequences of the damage are very serious.It poses a great threat to the personal safety of operators.In order to solve these two problems,this paper proposes a lightweight design scheme for the lower part of crawler crane,and performs analysis and verification for the buckling stability of truss arms,respectively.Finally,the weight of the whole structure has an obvious decline under the premise that the performance and service life of the whole machine does not decrease.This paper has proposed an overall improvement work of QUY450 crawler cranes based on the cooperation project of XCMG Research Institute and whose group company.The lightweight design of the product structure is carried out by the finite element method,and the correctness of the product design is verified through comparing with the test.Finally,the structure has a significant weight lost.The stability coefficients of the truss arm are modified and applied to the improvement of the truss arm by numerical simulation,bench test and comparison with the criterion.The main contents of this paper include:(1)The structural model of the track crane is built by using the finite element method,and the rigidity and strength of track frame,rotating platform and frame are analyzed in detail under all working conditions.The high stress zone and low stress range of track frame,rotating platform and frame under different working conditions are determined,which provides a detailed design basis for the subsequent topology optimization scheme.(2)Topology and size optimization are employed to make the lightweight design of track,frame and turntable.Among these structures,the design of track and turntable are mainly based on size optimization.For the frame part,considering that the structure is relatively complex and the improvement space is relatively large,hence topology optimization based on SIMP method is firstly used to make the basic design.In order to improve the computational efficiency on the premise of guaranteeing the accuracy of calculation,the super-element(SE)algorithm is employed to deal with the frame model in the optimization process.Then,in order to make the finally result more accurate,free shape optimization is used to deal with the result of post-processing of topology optimization,which can avoid design errors caused by engineering designers' experience.(3)The parametric language(APDL)is used to establish the FE model of circular tube and standard section of truss arm.The software ANSYS is employed to make the buckling stability analysis for high strength steel circular tube of different lengths and standard section of truss arm,then the buckling failure load of high strength steel circular tube and standard section of truss arm can be obtained and the pressure stability coefficient can be calculated.The rationality of failure load and pressure stability coefficient can be validated by buckling stability tests of circular tubes and standard section of various sizes.Finally,the standard section of the truss arm with better buckling stability is designed.(4)Field measurements of the whole arms of the crawler crane are carried out,and three test conditions are determined by discussions with the engineers.The results show that the performance of the new modified standard section is greatly improved compared with the previous one.The overall performance of the truss arm is raised by more than 10%.Based on the Goodman criterion,the durability analysis of the structure is carried out.Taking the most common working condition and the most dangerous working condition during the working period as the basis of force analysis,the fatigue life prediction of the structure was carried out by using the finite element simulation technology.The results show that the durability of the new designed structure meets the design requirements.(5)In this paper,the lightweight design of crawler crane has been applied to the production and sale of real vehicles,and achieved good weight reduction and energy saving effect.The topology optimization technology and parametric design method applied in this paper can be applied to the lightweight design of different types of cranes because of the traceability of the design process.This paper plays an important role in improving the forward development,design capability and lightweight level of domestic crawler cranes,saving production costs and enhancing market competitiveness.