Cylinder as a key component of the hydraulic press, the working life depends not only on its own quality design, but also to a large extent by the working conditions, especially large tonnage fast forging press, due to forging load, fast, Machine hydraulic control system design is irrational, will inevitably make the case under the fast forging conditions weakened, affecting its service life.
Hydraulic press control system of the main working process for the fast drop, electric cookware press pressure, pressure relief, return four processes. After the end of pressure, before returning, should be high-pressure large-capacity hydraulic cylinder storage of a large number of slow energy release, that is, a pressure relief process, pressure relief time can not be too short, suddenly pressure will produce a greater pressure shock, it will not only damage Sealing devices, pipes and hydraulic components, but also cause vibration and noise; pressure relief time can not be too long, otherwise it will extend the entire operating cycle, reduce efficiency. So the rational design of the direction of fast forging for the material processing and forging equipment.
It is important to improve the working quality of the whole press, ensure the quality of forging products, improve the working efficiency, reduce the impact vibration and prevent premature failure of the cylinder.
For the 80MN fast forging hydraulic press system, the frequency is the largest under the fast forging condition, and the hydraulic actuator element is directly related to the fast forging working device. The vibration is also the biggest, so in order to design the Forging presses to meet the minimum pressure relief time of pressure vibration, research and analysis of the pressure relief time on the side of the tank stress, strain is a key link. In this paper, the finite element method is used to analyze the lower cylinder of the 80MN fast forging press under different pressure relief time. Through the stress and strain cloud diagram, the main part of the stress and concentration of the side cylinder are obtained, The impact of strain.
1 to determine the minimum pressure relief time in the hydraulic system, if the flow rate u limited to 4.5m / s or less, so that the impact pressure Ap5MPa, you can think that the system is safe. So we can analyze the high pressure pipe connected to the side cylinder so as to meet the minimum pressure relief time that is not estimated by the pressure relief time that does not produce the impact pressure.
Object of study. Pipe material with 16Mn / Q345B, material elastic modulus E = 2.06e11; oil using N68, oil volume elastic modulus, take k = 1400MPa; forging pressure to 42MN, the side cylinder movement speed 5 ~ 150mm / s; side Cylinder plunger diameter 790mm, stroke 2 according to the pipeline flow velocity caused by the impact of sudden changes in the impact of the formula: c shock wave propagation speed in the official, take c Au from the beginning to the end of the pressure, the flow of the pipeline variable 2.1 Constraints to determine the hydraulic cylinder In the work, the high-pressure liquid through the plunger reaction to the cylinder at the end of the hydraulic pressure through the cylinder wall to the flange part of the flange and the balance beam bearing surface to support the reaction force to balance, assuming that the beam support reaction force A concentrated force on the circumference of the average radius of the flange contact surface, the size of the total load on the entire circumference; flange support, because the hydraulic cylinder with bolts and beams fixed, And the pressure on the upper part of the flange is constrained by the vertical direction of the joints on the upper surface of the flange. The inner wall of the cylinder is assumed to be uniformly applied to the part above the bottom of the cylinder at the same time, 16 min triangular cloth decremented down to 0 lower pressure drop, the pressure at the sealing is not only a function of time, it is also related to a location. In addition, for safety reasons, to limit the plunger out of the state to analyze, as long as the side of the cylinder at this position to meet the strength, stiffness and other performance requirements, in other position state can meet the performance requirements.
2.2 Parameter loading From the finishing time 75 times / min, the loading cycle: T = 0.8s., Respectively, for the pressure relief time of 0.03s, 0.06s press fast forging four working process of the approximate loading curve and The maximum load of the finite load model 3 to solve the stress during the loading process, the maximum value of the corresponding response time part of the stress, strain cloud and side cylinder stress, the maximum value of the corresponding node at different pressure time results of the results of the time curve, For the sake of saving space, only a few of them are listed.
0.06s pressure relief time under the side of the cylinder stress, strain cloud diagram We will be two pressure relief time under the fluctuation peak list shown in Table
Table 1 fluctuations in the results after the end of the peak results of the results of the results 0.03s pressure relief time 0.06s pressure relief time time fluctuations maximum time fluctuation minimum time fluctuation maximum time fluctuation minimum value Y-displacement 0.720.214 by e know, 0.03s pressure time, the equivalent stress of the side cylinder reaches the maximum value at 0.59s during the loading cycle of the whole cylinder, which is 0.01s ahead of the maximum loading time of the load, and the maximum value of the equivalent stress is 177.371MPa. By the time of 0.06 s pressure relief time, the equivalent stress of the side cylinder reaches the maximum value at 0.56 s during the whole cylinder loading cycle, electric screw presses and it is 0.01 s ahead of the maximum load load time. The value of 176.933MPa; Similarly, other results can be compared, can be drawn as long as the side of the cylinder in the loading process of the maximum load value of the same, the pressure relief time basically does not affect the side of the cylinder stress, strain the maximum value of the results, and ⑷ The stress and strain time curves can be seen in the stress and strain time curves of the stress time of 0.06s under the stress period of 0.03s. When the two pressure relief times, the X-direction maximum deformation occurs in the middle of the cylinder; To the maximum Shape occurs at the inlet, this is because the hydraulic cylinder in the internal high-pressure oil under the action of the liquid hole to the outer flared deformation caused by the integrated deformation occurred in the middle of the cylinder near the bottom of the cylinder, followed by At the bottom of the cylinder. The maximum principal stress occurs in the middle of the cylinder at the flange; X, Y to the maximum stress occurs at the beginning of the sealing ring, followed by the bottom of the cylinder, which is mainly because the sealing site and the bottom of the cylinder The maximum value of the equivalent stress occurs at the transition arc of the flange to the cylinder, and the load time of the maximum load is advanced, and it can be seen that the equivalent stress value under the two pressure relief times Are within the allowable stress range, so the side cylinder meets (on page 14) BP neural network simulation diagram strength requirements. In short, the side of the cylinder prone to stress concentration of the site (ie, easy to failure parts) are mainly concentrated in three parts, one flange and cylinder connected to the arc part; the second is the cylinder wall at the end of the transition arc; The location of the seal.
The axial deformation, X, Y stress and the third principal stress of the side cylinder are mainly affected by the pressure relief time, and the radial deformation and equivalent stress of the opposite cylinder are not affected. The Y-displacement fluctuation amplitude increases by 73%, the X-stress fluctuation amplitude increases by 54%, and the Y-stress fluctuation amplitude increases by 54% compared to the pressure relief time of 0.03 s and 0.06 s. The third principal stress fluctuation amplitude will increase by 156%. It can be seen that the shorter the pressure relief time, the more stress after stress relief, the more severe the strain fluctuation, so it can meet the stress and strain fluctuation range as the initial design minimum pressure Time condition. At the same time can also be considered a reasonable design of the hydraulic control system pressure relief time, to improve the dynamic quality of the side cylinder is very important.
5 Conclusion Pressure relief time as a fast forging press a dynamic performance index, the value of the size of the system directly affect the performance, the specific value in addition to the system structure, valve structure, design parameters, but also with the assembly quality and experimental environment, It is difficult to accurately determine its size. This article from the pressure relief time film 1 hydraulic system failure table system pressure unloading valve dispatch 1 pressure oil temperature failure cause lower normal high hydraulic pump failure higher normal high flood valve set higher high overflow Oil Block Blocking Table 2 Neural Network Training Sample Set Sample Number Sample Input Target Output Table 3 Test Sample Output Result Test Sample Expect 1 Out BP Network Output itPSD-BP Output Compressor Shock Vibration Angle Starting from the initial determination of minimum pressure relief Based on the time, the paper analyzes the influence of different pressure relief time on the stress and strain of the side cylinder under the fast forging condition, and obtains the conclusion that the pressure relief time does not affect the stress and strain maximum of the side cylinder, but reduces the pressure relief time, But also the axial strain, X, Y stress and other performance indexes of the side cylinder after the pressure relief are more fluctuating, which can provide the theoretical basis for further determination of the minimum pressure relief time.
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