Self-propelled Crane Research Articles

Методология выявления и оценка значимости факторов, влияющих на аварийность грузоподъемных кранов

Analysis of the sources of scientific and technical literature shows that the main factors that cause the accident rate of lifting structures are factors of manmade, natural and «human» characters. The article proposes a methodology for identifying and assessing the significance of factors that are, at first glance, indirect, but have a significant impact on the causes of the accident rate of boom self-propelled cranes. The proposed methodology consists of three stages, each of which separately is quite well tested by other authors. At the first stage, based on the analysis of expert assessment according to the Hay method, it is proposed to identify significant factors. At the second stage, on the basis of the chi-squared criterion, the significance of the factor is assessed. At the third stage, a methodology for conducting a numerical experiment is proposed to assess the significance of factors based on the use of neural networks. Obviously, the proposed methodology can also be used in assessing the significance of factors of other events, and not only in case of accident rate of lifting structures.

Экспериментальные исследования колебаний груза при перемещении грузоподъёмного крана ДЭК-251

Measurement of the parameters of vibrations of the load moved by a self-propelled crane with a flexible rope suspension when the crane moves along an unprepared construction site with irregularities is an urgent task, since it will allow using the obtained numerical values of the vibration parameters to improve the accuracy of the crane’s operation in terms of moving loads. Based on the solution of this problem, it is possible to create systems for automatic damping of cargo vibrations. This will reduce the time spent on performing a work step when moving a load. This also solves the problem of reducing the dynamic loads on the elements of the crane. The article discusses one of the methods for determining the angles of deviations of the point of the load and the point of suspension of the load on the boom when moving the DEK-251 mobile crane along the unevenness of the construction site using the projection-polynomial mathematical model of the optoelectronic system. As an example, the article presents a number of graphs of time dependences of changes in the values of the angles of deviations of the load and the point of suspension of the load when moving over the unevenness of the site of a crane with a boom length of 22 meters and an angle of inclination of the boom of 48 degrees. The cargo was at a height of 4.8 meters, the weight of the cargo was 200 kilograms. The graphical time dependences of the load fluctuations and the load suspension point in the longitudinal plane are given in the form of angles of deviations from the lens center, taking into account the microrelief. The data allows you to calculate the linear coordinates of objects in space. Moreover, the results were obtained taking into account the camera errors.

Mathematical modeling of the joint movement of mechanisms for lifting, turning and changing the crane's departure"

It was determined that the load on the crane from the load that is swinging depends onthe scheme of its suspension and the inertial characteristics of the cargo.The research was carried out using mathematical methods that describe the transientprocesses that occur when the lifting, rotating and changing mechanisms of the crane DEC251 are moving together.When examining the fluctuations of cargo on suspensions according to schemes 1 and2, the following assumptions were accepted: the rope is an ideal, weightless thread; masslessblocks roll over ropes without slipping; there is no energy dissipation in vibrations; the lengthof the suspension is constant.The dynamic workload of the system was evaluated by the method of comparativeanalysis of the graphs of forces, displacements, and velocities of reduced masses of the boom system. In our work, we also constructed calculation schemes for the joint movement of thelifting and turning mechanisms of the self-propelled crane, and considered particular cases ofoperation of the crane mechanism.The research resulted in receiving expressions for calculating the load on the cranefrom the cargo, which is swinging on the ropes, which take into account the suspensionscheme of the cargo and its inertial characteristics. When the load on the suspension isoscillating according to scheme 1, there is a redistribution of the tension in the ropes, andunder appropriate conditions one of them may weaken.

Determination of inertial loads of the rota-ry boom of a self-propelled crane

Self-propelled jib cranes are most widely used in construction for loading and unloading operations, the main advantage of which, among other types of cranes, is high mobility. The share of self-propelled jib cranes in construction is more than 60%.
 An important element of the construction of self-propelled jib cranes is the boom, the strength of the structure of which largely depends on the safety of the crane and the prevention of accidents that lead to injuries and death of maintenance personnel. When calculating the crane boom for strength, power of electric motors for changing the departure of the boom and turn, the brakes of these mechanisms must take into account all types of loads acting on the rotary boom with load, including inertial, which account for a significant share among other loads.
 The paper considers the calculation of the following moments of inertia forces: created by vertical inertial forces during braking of the load lifting mechanism; arising from the mass of the load and the boom during the period of unstable movement of the mechanism of change of the boom departure during start-up and braking; the load created by centrifugal force which arises at rotation of a rotary part of the crane; arising from the mass of the load and the boom during the period of unstable movement of the crane rotation mechanism. When calculating these moments of inertia, the following initial data are taken into account: geometric dimensions of the crane, weight and length of the boom, weight and height of the load, angle of the self-propelled crane in the construction area, radius of the crane boom, boom and load speeds, start and braking times mechanisms for lifting the load, changing the departure of the boom and turning the crane.
 The obtained dependences for determining the inertial loads of the rotary boom of a self-propelled crane will allow more accurately taking into account multiple factors to calculate the values of these loads in order to perform strength calculations of the boom, selection of components for lifting, changing the boom and turning the crane.

Stability Control of a Self-Propelled Crane in Dynamic Loading

A stability control system is developed for a self-propelled crane in dynamic loading. The simulation of crane operation takes account of the flexural deformation of the elements and the operation of the hydraulic drive, along with interactive control. The simulation is based on the integration of Matlab Simulink, Fuzzy Logic Toolbox, and SolidWorks CAD 3D modeling software.

ТЕОРЕТИЧЕСКОЕ И ЭКСПЕРИМЕНТАЛЬНОЕ ОБОСНОВАНИЕ ИЗМЕНЕНИЯ УСИЛИЙ В ОПОРАХ СТРЕЛОВОГО САМОХОДНОГО КРАНА

In the paper on the basis of the Rostechnadzor report data there is revealed the topicality of the work connected with stability loss of boom self-propelled cranes during the work on weak load-bearing soils. The fulfilled out theoretical investigations of effort distribution in supports depending upon the angle of a boom pitch (boom extension), the angle of boom rotation in a horizontal plane and the weight of the load to be lifted allowed offering a practical realization of measures for boom self-propelled cranes updating at the expense of the introduction of underlying mechanisms allowing not only the assurance of surface horizontal positioning, but the change of soil bearing capacity (supporting surface). 
 For the determination of the effectiveness of the device offered ensuring a table work on weak load-bearing soils there was developed a procedure for the fulfillment of experimental investigations consisting of two stages. At the first stage there were defined efforts in crane supports depending upon a weight of the load to be lifted and sp-acial boom position. At the second stage there was carried out an estimate of crane support subsidence into soil of different state for basic and updated machines. The investigation results are confirmed with confidence probability of 0.95 by Cochran, Student and Fisher criteria. 
 As a result of experimental investigation carrying out there was defined that the application of an updated design allows increasing self-propelled crane stability by 1.41… 2.27 times.

Management The Safety of Exploitation of the Rotation Mechanism in a Self-Propelled Crane

Abstract The article analyzes of the load capacity of the rotation mechanism of the boom arm sub-assembly for a self-propelled crane. The uneven flexibility of systems supporting structures of the machine was taken into account in the identification of the load. The consideration are illustrated by the example slewing bearing from self-propelled crane. FEM method was used for calculations. The basic problems of construction of numerical model were discussed. Sample calculations of bearing carrying capacity has been done taking into account flexibility of bearings supporting structures, which also allowed to define the internal load distribution in the bearing. On example of the supporting structure of the mobile crane DST 5050 the internal load distribution in the crane bearing at different positions of the crane machine body were defined. During the rotation of the crane body priority angels were indicated. It has been shown that the deformations of the supporting frames are so large that they significantly change the distribution of forces transmitted by the individual bearing rollers.

Research of rational placement of damper in boom system of self-propelled crane

During the operation of boom cranes, the longitudinal dynamic fluctuations appear in metalware and in ropes of the boom system. This leads to the reduction of fatigue strength and impairs the conditions of the normal operation of the crane. One of the criteria for assessing the quality indices of the transients is a dynamism coefficient, which has the greatest values when lifting a load from a stiff foundation. To study the dynamic processes a mathematical model was developed. It permitted to take into account the peculiarities of the design of suspension of the load and boom, the reduced strength of the drive, the effect of dissipative forces and the coefficient of damping of oscillation absorbers. After the solution of the differential equations we have obtained the dependences of formations of forces in the elements of metalware. Due to these dependencies we have determined that installation of the damper in the suspension of the load increased significantly the qualitative indices of the transients. Also the dependences showed that the installation of the damper in the system of the boom suspension had had no significant effect on the damping of oscillations and had been ineffective.