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The boom is the most important working part of the truck crane. The design of the boom directly affects the lifting performance of the crane. The structural mass of the boom generally accounts for 13%~15% of the total mass of the crane. With the large

boom being the most important working part of the truck crane, the design of the boom directly affects the lifting performance of the crane. The structural mass of the boom generally accounts for 13%~15% of the total mass of the whole machine, and this proportion will be higher with the development of large tonnage truck cranes. How to reduce the weight of the boom and improve the performance of the whole machine without affecting the lifting performance is the key problem to be faced in the design of the boom. At present, there are two main methods adopted in the industry: ⑴ apply high-strength materials; (2) improve the boom structure, and adopt polygon (even large arc and oval) boom to replace quadrangular boom

with the continuous development of large tonnage crane products, researchers are developing PEU (DegraPol reg;) As support material; In orthopaedics, high-strength steel plates have been widely used, and the strength of the boom has also increased significantly. However, if the strength of all materials is exerted, the structural deformation of the boom will also add a sledgehammer sander. As a result of the increased deformation, the bending moment caused by the axial force of the boom will become a factor that can not be ignored. Therefore, under the condition of non-linear, it is necessary to apply a new algorithm to redesign the boom and calculate the cement machinery considering the deformation of the boom

nonlinear calculation of boom design

1 Geometric modeling

in order to realize the programming and generalization of the boom calculation, it is necessary to parameterize the boom geometry and physical state, which mainly includes the following three parts: ⑴ the boom section geometry is determined by the angle, side length and other dimensions; (2) determine the mass, length and center of gravity position of each arm; (3) determine performance parameters, including single rope lifting speed, lifting pulley block magnification, etc

2. Nonlinear iterative calculation process

take the jib of Liugong qy70 truck crane as an example to calculate the high-pressure pulverizer. The main jib of the crane is composed of a basic boom and four telescopic booms. The telescopic mode is sequential and synchronous

firstly, analyze the stress of the boom and the cement production process. In the luffing plane, the loads on the boom include: (1) lifting weight; (2) dead weight of boom; (3) wire rope tension of lifting mechanism. When calculating the bending moment of each dangerous section on the boom, the product of the axial component of each force and the axial force arm shall be added for high-pressure micro grinding

carry out force analysis in the rotation plane. The loads borne by the boom include: (1) the load of lifting load deflection; (2) wind load; (3) dead weight of boom; (4) lifting mechanism steel wire rope tension sand washer. Similarly, the bending moment caused by the axial component of the above load shall also be considered when calculating the bending moment of each dangerous section of the boom

in the iteration process, it is assumed that the elevation angle of the boom is unchanged, and the feedback iteration of the rod mill is carried out through the change of the deflection of the boom end

by setting the initial value, first calculate the bending moment and transverse force at each dangerous section, then calculate the deflection and rotation angle formula through material mechanics, and calculate the deflection and rotation angle of each arm section. Through accumulation, the total deflection of the boom can be calculated. Compare this deflection with the initial deflection. If the set conditions are met, the bending moment, transverse force and axial force of each section will be output. If not, this deflection will be assigned to the previous deflection, and the bending moment and transverse force will be recalculated, and the new total deflection cement mill will be calculated. In this cycle, until the deflection obtained from the previous and subsequent cycles meets the conditions we set, the boom is considered to have been balanced, and the value obtained is the value after the boom deformation is balanced. The calculation idea of the rotary plane is the same as that of the luffing plane

in the cycle process, the change of total deflection is taken as the judgment condition, and the total deflection is obtained by calculating the deflection and rotation angle of each arm, and the calculation formula of deflection and rotation angle is derived from the actual model with the formula of material mechanics

compared with the previous fiscal year 3 Check the strength and local stability

the bending moment, transverse force and axial force of each dangerous section are obtained by the nonlinear iterative method, so that the stress value of each point on the boom section can be calculated. The local stability and strength of the boom shall be calculated in strict accordance with the relevant contents of the crane design specification gb/t3811, and checked with their respective allowable stresses

finite element analysis and calculation

1 Establishment of finite element model

the establishment of finite element model should not only truthfully reflect the structural characteristics, but also try to reduce the complexity of the model. Based on this principle, we simplified the mobile crusher for the boom. Because the boom is mainly subjected to compression bending, we use beam element beam181 to model. Draw lines according to the actual arm length, lap length and slider position of each arm, and then assign the previously established two-dimensional section attribute of each arm to each arm ceramic ball mill. The boom head and pulley are simplified. The cell type and material properties of the model are defined, and then the lattice division of the high-strength pulverizer is carried out

2. Loading and adding constraints

are decomposed according to the actual force and loaded into the boom, including the axial and transverse decomposition force of the lifting load, the tension of the steel wire rope and the gravity. The three degrees of freedom in the X, y and Z directions are coupled between the arms, and the rear hinge point of the boom is constrained. Except that the degrees of freedom in the Y direction are not constrained, the other five degrees of freedom are constrained. In addition, the lower hinge point of the luffing cylinder and the steel wire rope are also constrained by the cement plant equipment. After the constraints are loaded, the general solver is used to solve the problem, and the calculation results are obtained

3. Comparison between the calculation results and the finite element calculation results

two working conditions are selected for comparison. One is the fully extended boom, that is, the boom length is 44.2m, the elevation angle is 79 °, the lifting weight is 10t, and the magnification of the lifting pulley block is 3; The other is the case that the first oil cylinder is fully extended, and the second oil cylinder is extended by 1/3, that is, the arm length is 27.5m, the elevation angle is 79 °, the lifting weight is 20t, and the lifting pulley block magnification is 4 (see Table 1 and table 2 for the comparison results). Through comparison, it can be found that the results obtained by the nonlinear calculation method and the finite element simulation are similar. It can be used in shell and trim, medical devices, precision manufacturing, aerospace and other aspects to show that the calculation results are accurate

experimental verification

when carrying out experimental verification on site, it is necessary to selectively stick resistance strain gauges on the boom to measure the strain of the boom. The arrangement of strain gauges is consistent with the points on the dangerous section selected by the program calculation (see Table 3 for the comparison between the measured results and the calculated results), and the maximum error is not more than 20%. Considering the wind load, weight, boom warping The accumulation of various error factors, such as the complete accuracy of the position of the strain gauge, the calculated results and the measured results are acceptable, which shows that the calculated results of the program are true and reliable, and provide great help to the design and development

in this paper, the crane boom design software developed by nonlinear iterative algorithm is used to calculate the crane boom of Liugong qy70 crane, and the finite element simulation is carried out under the same working conditions. The final comparison results show that the error between the two is 5%. Through the field test, the results are also consistent. This shows that the calculation method is feasible

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