Research of stresses in metal structure of the tractor frame by semi-trailer scraper

Autors
Kovalevskyi S. G., Yaryzhko A. V., Krasnokutskyi V. M.
Issue
Hoisting and transport equipment, 2019, №2(61)
Pages
93-103
DOI
10.15276/pidtt.2.61.2019.08
Abstract
A design scheme of a semi-trailer scraper was developed during the knife immersion into the soil, on the basis of which, taking into account reasonable restrictions and boundary conditions, a two-mass mathematical model was created, which has degrees of freedom in horizontal and vertical directions. In order to simplify the mathematical model, the angular oscillations of the tractor and the scraper were not taken into account, due to their small influence on the actual loads during bucket depth. The implementation of the mathematical model allowed us to obtain graphs of the dynamic changes in the horizontal and vertical force acting in the hinges of the traction frame. The oscillatory nature of the loads showed that the maximum values are reached in almost the same period of time in the first half period, and the horizontal and vertical efforts increase with increasing intensity of resistance to digging, reaching maximum values of 150 and 60 kN, respectively. It is established that the rate of increase of the maxima of the horizontal force is uneven, so with increasing intensity from 50 to 150 kN / m, the highest value increases by 19%, and from 150 to 250 kN / m - by 11%, which makes it possible to conclude that the work is expedient with lower speeds of dipping the bucket knives into the ground, taking into account the load on the metal structure. The growth rate of the maxima of the vertical force can be considered uniform with an increase in the speeds of movement and the category of soil being developed. The results of the force load allowed us to study the stress-strain state of the semi-trailer scraper frame at the beginning of the ground collection, for which a computer model was created taking into account the mechanical characteristics of the steel from which the frame was made. Computer simulations performed showed that the most intense section of the front part of the frame is the junction of the arch with the transverse beam, in which the maximum stress values reach 175 MPa when immersed with an intensity of 250 kN / m. The stresses that occur at the junctions of the lower arch sheet with the lateral ones, as well as at the upper lugs, are much smaller and are within 70 - 105 MPa. The margin on yield strength in the most stressful place is 1.9, which is not enough for normal operation of the traction frame at such design loads. An increase in the radius of the side arch sheet connection with the transverse beam from 2 mm to 4 mm made it possible to reduce the maximum stresses by 68% to 120 MPa, and the introduction of a connection with a radius of 6 mm provided a stress value of 80 MPa Thus, the conducted studies have shown the need to refine the metal structure of the trailer frame of the semi-trailer scraper in order to reduce the stress state and increase its durability.
Keywords
scraper, modeling, working process, loading, metal construction, traction frame
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