Analysis of the load-bearing system of the loader according to the results of dynamic tests in the environment of Ansys motion

Annotation. Problem. The T-156B hinge frame of the loader, which is an upgraded frame of an agricultural tractor, creates loads during work operations for which it was not designed. Such loads lead to breakdowns and further shorten the life of the entire machine. The frame is the basic element around which the machine is built. The loader that had just been removed from the conveyor did not have built-in durability and reliability. While designing a road construction machine, an account of the features, nature, and conditions of its operation should be taken. Goal. The goal is to develop a hinge frame design technique that takes into account the loads experienced by the frame with a virtual simulation of real-world situations during the loader process. Methodology. The adopted approach is based on the use of a Solidworks computer program with three-dimensional modeling and an Ansys motion program for calculating the dynamics of multicomponent bodies taking into account the hinge and contact interaction. Results. In the work three cases of technological operations of the loader were considered. 1. Lifting a full bucket. 2. Collision with an obstacle that is difficult to overcome 3. Movement over an uneven surface with the raised loader arm. The results of the calculations provided forces and torques in the hinge of the half-frames, as well as the effort of the frame. Based on the results obtained, the endurance of the frame in the Ansys motion software package was calculated. Originality. The analysis of load-bearing systems with a virtual simulation of the machine’s actual behavior with the help of Ansys motion software allows to obtain more accurate results, significantly reducing the time for the design and cost of field testing. Practical value. This approach to the analysis of the carrier system behavior can be recommended for designing and determining the technological capabilities of wheeled, tracked, and special machines.


Introduction
When designing units of articulated machines, in particular tractors, there is a question of ensuring the strength characteristics and durability of the load-bearing system (frame). When designing the frame considered several design modes: hanging, rotation on the spot, and plowing (for agricultural machines). In the next stage, bench and field tests shall be carried out in all these modes [1][2][3].
Designing of the loader T-156B frame went by upgrading the serial frame with retaining unification with the agricultural tractors ( Fig. 1), since there were no methods to fully analyze the loader's behavior during the design phase, and testing of each new model was very expensive and time-consuming. This design method is not effective because the upgrade of the serial frame did not consider the working conditions and purpose of the designed machine. The main disadvantage of the production frame is the presence in the design of the horizontal hinge, which critically affects the stability of the machine, as well as the presence of a rear axle spring suspension, resulting in the rocking of the loaded machine during the execution of work operations.

Analysis of publications
Nowadays the problem of rational design and durability of carrier systems is solved by the finite elements method (FEM) [4][5][6][7][8][9] and specialized complex calculation programs. Analysis and calculation of the hinge frame with the help of the Ansys design complex were considered in the works [10][11][12][13].
The loads obtained during natural experimental studies [14] were applied to the serial frame. Based on the results of load calculations, a prototype welded frame was designed taking into account all tension [15,16]. But to get acting on the frame loads is not enough for a complete analysis of the carrier system. The durability of the structure plays an important role. The issue of durability was considered in the works [17][18][19], during which the Ansys calculation complex was also used in conjunction with nCode DesignLife. The results of the calculation showed that during the operation of the loader there are weaknesses in the structure of the frame, which start to break down when they are affected by the workload.

Purpose and tasks
To create a method of strength and durability testing with the help of modern calculation complexes for the newly designed bearing systems by computer model analyzing with modeling the machine working operations. For this purpose, a created computer model of the loader should be the most relevant to the real machine. To determine the workflow load.

Methods of strength assessment of the bearing system based on the results of virtual tests simulation.
Ansys Motion is a specialized dynamic analysis program that contains a range of tools for simulating and designing kinematic systems.
ANSYS Motion combines four closely integrated solutions: rigid bodies, deformable bodies, modal analysis, and EasyFlex. This, taken together, provides a great opportunity to analyze systems and mechanisms.
In the work simulated several similar to the real one's situations of the workflow of the loader T-156B: 1. Lifting the filled bucket. 2. Collision of the bucket with an insurmountable obstacle when filling the bucket. 3. Movement on an uneven surface with a full bucket (loader arm raised maximum).
The T-156B loader model built by Solidworks CAD is used for calculation. The model is imported into Ansys motion, then the model is prepared for calculation. Defined hinges, involved in the calculation, relationships between the units, and written function expression for bodies that will move in the calculation (wheels, loader arm), set the total calculation time, and a number of calculation steps. After all the settings, the calculation starts. After the strength calculation, the fatigue resistance of the structure is calculated and it is possible to determine the areas that are prone to damage.

Strength evaluation of the load-bearing system
In the beginning, the case when the loader on the spot (Fig. 2) performs lifting the loader arm up to the maximum position with the filled bucket was considered. Total lift time -4 seconds.

Fig. 2. Postprocessor configuration window for full bucket lifting situation
At the end of the calculation were obtained the graphs of active forces and torque in the hinge joint of the half-frames (Fig. 3-4). Automobile transport, Vol. 51, 2022 After stopping the bucket in the elevated position, there are residual vibrations from the inertia of the filled bucket lifting, which also fade out. In order to better visualize the tension flow in the frame, loads on the VonMises scale are displayed. According to the results of the calculation, it can be seen that the maximum tension falls on the portal of the front half-frame at the points of the loader arm attachment to the frame (Fig. 5), (Fig. 6), and reaches 820 N/mm 2 . Loads in the hinge and at the junction of the half-frames range from 200 N/mm 2 to 300 N/mm 2 . This mode of the loader operation is the least loaded as there are no impact loads. Next, we considered the case of impact load on the frame. The loader moves on a flat horizontal surface at a speed of 5 km/h, the loader arm is lowered, and the bucket in the lower position with the impact interaction of the bucket edge into an obstacle that is difficult to overcome (Fig. 7). At the end of the calculation were obtained graphs of active forces (Fig. 8) and torque ( Fig. 9) in the hinge joint of the half-frames. During the start of the movement, there are attenuating vibrations caused by inertial forces due to the movement of the half-frame mass with the bucket and the force of the resistance to moving the bucket over the surface. Short-term surges in load and torque occur at the moment of impact. The force increases at 0.78 s to 1,200 kN and the torque increases to 100 kN·m, at 0.9 s to 590 kN and 45 kN·m, and at 1.1 s to 690 kN and 38 kN·m. In order to make the tensions in the frame more visible, we will display the load on the VonMises scale at the moment of collision with an insurmountable obstacle. The hinge joint (Fig. 10), (Fig. 11) has the highest loads which reach up to 1.2 kN/mm 2 .
The third calculated case is the movement of the loader on an uneven surface. The loader will move at a speed of 3.6 km/h with the full bucket raised to the maximum position on the platform simulating the pit and potholes (Fig. 12). At the end of the calculation were obtained graphs of active forces (Fig. 13) and torque (Fig. 14) in the hinge joint of the half-frames. During the start of the movement, there are oscillations arising from inertia forces due to the movement of the half-frame mass and the full bucket in the upper position. At 2.4 s during the drive of the front left wheel into the pit, there is a hanging of the rear right wheel. The rear half-frame has a large length, which in turn creates a larger shoulder, and thus the hung rear right wheel creates the most force in the hinge of the half-frames. The force is 460 kN and 50 kN m. of torque. This display gives maximum load on the frame. Further roll-ups from the pit to the pothole and exit to a flat surface create less effort. To make the tensions flow in the frame more visible, we will display the load on the VonMises scale with the rear right wheel hanging when the loader drives the front left wheel into the pit. The most heavily loaded elements are the hinges for fixing the loader arm to the front half-frame, where the loads reach 800 N/mm 2 with extension to the portal sidewalls and lower anchorages of the hinge joints of the half-frames, where the load reaches up to 500 N/mm 2 with extension to the entire hinge assembly and the lengths of the front half-frame (Fig. 15) and (Fig. 16). is calculated by applying the resultant load to the structure of 1,000,000 repetitions. At the end of the cycle, a calculation is made of which element can withstand how many repetitions, and on the color scale it is possible to analyze which areas need to be strengthened or weakened to optimize the mass characteristics.
In the first situation, when the fixed loader is calculated, the frame does not experience serious loads. In general, the design can withstand a cycle of 1,000,000 repetitions, only at 358,760 cycle repetitions there are small cracks in the sides of the hinge attachment (Fig. 17). The second situation in which the loader is impacted is the most dangerous for the frame. The hinge joint unit, the portal sidewall at the point of attachment of the loader arm hinge to the portal, and the front half-frame spars are already inoperable after less than 100,000 cycle repetitions (Fig. 18) and (Fig. 19). With all this damage, the loader is completely out of order. In the third situation, the loader frame is tested by time-varying loads from the beginning of the wheel collision into the pit to the exit to the flat surface. Although in the third situation, the frame is affected by a lower impact load, but still, they are critical.
The least durable is the side of the portal at the point of the loader arm attachment to the portal and the bottom attachment of the hinge of the half-frame joint. These elements fail after less than 100,000 iterations of the cycle. The top attachment of the half-frame hinge is slightly more durable, withstanding 200,000 cycle repetitions (Fig. 20) and (Fig. 21). With such damage, the loader is also completely out of order.

Conclusion
The article presents a method of calculation of the loader frame in dynamics on the example of real working processes of the loader. The results of the calculations are obtained vulnerabilities of the frame that need to be improved.
The most critical is the case of a loader collision with an insurmountable obstacle. The vertical hinge experiences the biggest short-term breaking loads up to 1,200 kN, which negatively affects the reliability of the entire frame.
Fatigue life calculations show that in all three cases, critical frame elements do not go through a full cycle of 1,000,000 repetitions. The frame receives maximum damage in the event of a collision with an insurmountable obstacle. Shock loads greatly reduce the reliability of the frame Автомобільний транспорт, Вип. 51, 2022 and already at 100,000 repetitions there is significant damage to the vertical hinge, as well as other important components, such as loader arm attachment points and spars.
This method makes it possible to identify the weaknesses of the designed structures in the shortest possible time and without significant costs.