Деформівно-напружений стан несучої системи грейферного навантажувача ПЕА-1А

Abstract

Розглянуто плоску просторово-навантажену рамну конструкцію навантажувача-eкскаватора самохідного ПЕА-1А модифікованим методом мінімуму потенціальної енергії деформації для розв’язку задач пошукового конструювання та оптимізації геометричних параметрів несучих систем за повним напруженим станом. Отримано рекомендації для раціональнішого взаємного розміщення найбільш навантажених елементів, що призвело до підвищення їх міцності при одночасному зниженні матеріаломісткості.

Space-loaded frame structure of agricultural grab loaders and theirs components need improvements. Besides, constructional system of the grab loader tends to change from the considerable differences of rigidity. Planar space-loaded frame structure of the self-propelled excavator is analyzed in the article using the modified method based on the principle of minimum potential energy of deformation to solve the problems of design and optimization of geometrical parameters of the frame structure in complete tension. The calculation of simple frames with help of other methods is extremely bulky and takes much time, but this method simplifies even the calculation of the complicated frame structure. Metalwork of grab loader consists of longitudinal longerons with five different profiles. The main loads acting on the frame structure of grab loader are the external forces from the engine and gear-box, driving axle, speed-reducer and rear wheels, turning cylinders and boom of loader. These forces are counterbalanced by reactions of five fulcrums of the grab loader. The investigation of the stressed-strained state of frame structure of the grab loader begins with the design of the main scheme of calculation. Conditional intersection along the frame symmetry plane is used for construction of basic model of the grab loader and the action of the first part on the second is substituted by the internal unknown force factors. If the frames are composed of elements of an open section, the energy of torsional deformation is only taken into consideration that does not influence the final results. Potential energy of deformation of the frame of this type is equal to the sum of potential energies of its parts: potential energy of the first part of the frame of its elements under torsion and potential energy of the second part in the same condition of deformation. The expression of potential energy of deformation of both parts of the frame of its elements under torsion is formed on the basis of the following assumptions:  units of conjunction of traverse with longitudinal longerons are left unchanged before and after the deformation;  power of deformation of shear and distension is not taken into consideration;  the influence of moving power on distribution of internal forces in elements of frame of pull-type machines is neglected. Suitable quantity of unknown forces is excluded from the function of potential energy with the help of the equations of statics. Integrands of functions of potential energy of deformation are differentiated using the Leibniz’s rule. Definite integrals are calculated. According to the theorem on the smallest work each of derivatives of the potential energy of deformation equals to zero. As the result, a system of linear canonical equations is aggregated. Received canonical equations are divided into two independent systems for calculation of space-loaded frame structure. The first is used for the determination of symmetric and antisymmetric unknown values. It results in simplification of computation of this system. The second is used for algorithmization of calculation. As the result the internal unknown force characteristics are found. Tensity of the most dangerous section of the frame structure is determined using the numerical values of internal unknown values and predicted external loads. Recommendations for more efficient mutual locations of loaded elements are obtained the result of which is the increase of their strength while reducing material capacity.