In my journey through the field of manufacturing, I have delved into the structural design and finite element analysis of large forging hydraulic presses. These powerful machines are essential for producing high-strength components, and their design requires careful consideration of various factors to ensure reliability and efficiency. By utilizing finite element analysis, I have been able to identify potential weaknesses in the structure and optimize performance. In this article, I will explore the key aspects of large forging مكبس هيدروليكي structural design and the role of finite element analysis in enhancing their effectiveness and durability in industrial applications.

1. What is Large Forging Hydraulic Press

The working cylinder is an important actuator of the hydraulic machine. It converts the pressure energy of the liquid into mechanical energy. It is divided into plunger type, piston type, swing type and telescopic type according to the structure type. The working cylinder of the 200MN forging مكبس هيدروليكي adopts a plunger type, which has a simple structure and is easy to manufacture. It is a structural form commonly used in large hydraulic machines. The traditional design theory of hydraulic press is the main basis for the structural design of the working cylinder.

ABAQUS is skilled in solving complex problems and has achieved world-leading finite element analysis software. It is widely used in machinery, military, chemical, automotive and other industrial fields. Using ABAQUS to numerically simulate the hydraulic cylinder, the stress distribution of the working cylinder can be accurately determined, and the rationality of its structural design can be analyzed.

2. Structural design of the working cylinder

In order to save energy, especially to reduce power consumption, the 200MN largeforging hydraulic press uses six working cylinders in three rows. The 6 working cylinders can generate 200 MN of pressure at the same time, and the 4 small working cylinders on both sides can generate 80 MN of pressure, and the middle 2 large working cylinders can generate 120 MN of pressure. The working cylinders with different movements can generate 3 levels of pressure, and different forgings can be produced to select the corresponding pressure level, which greatly saves the cost. The structure of the body and the layout of the working cylinder are shown in Picture 1 and Picture 2.

In order to improve the life of the working cylinder, the design directly uses the bolt to fix the cylinder block on the upper beam, that is, the bottom support is used. This not only improves the rigidity and strength of the upper beam, but also reduces the cylinder wall stress of the working cylinder.

The single ball hinge connection is suitable for the slider and the four small cylinder plungers on the side, and the double ball hinge connection is the best connection method for the slider and the middle two master cylinder plungers, as shown in Picture 3a, b .

When the working pressure of the working cylinder is higher than 20 MPa, carbon steel forging is the main production mode of the working cylinder. The working cylinder of 200MN forging hydraulic press works under the high pressure of 31.5MPa, and the structure is large, it is difficult to forge integrally. Therefore, it is forged by welding of 35 steel, and it is normalized and tempered, and its yield strength is 240MPa.

The plunger reciprocates in the cylinder and has a great influence on the wear of the guide sleeve and the seal, so the plunger surface must have sufficient hardness and good surface finish. In order to meet this requirement, the plunger is generally made of carbon forged steel with a high carbon content and subjected to surface strengthening treatment after machining. The hydraulic machine plunger is forged from 45 steel.

The nominal working pressure of the intermediate working cylinder is 120MN, and the design calculation of its structural parameters is as follows:

According to the nominal total pressure F(N) that the hydraulic cylinder should produce and the selected liquid working pressure P (MPa), the plunger diameter D is determined by the following formula:

From formula (1), D=1557.7mm is calculated, and after rounding, D=1560mm is taken, and the inner diameter D1 of the hydraulic cylinder is connected with the plunger.

It is related to the gap Δt of the inner wall of the cylinder, and it is preferable to take 15mm according to the experience Δt.

According to the above formula (2), the inner diameter D1 of the hydraulic cylinder is determined to be 1590 mm. According to the empirical formula, the hydraulic cylinder outer diameter D2 is:

[σ] take 120MPa, according to the above formula (2), find the outer diameter D2 of the hydraulic cylinder is 2153mm, and according to the formula:

  r1———Cylinder inner radius (mm)

  r2———External radius of hydraulic cylinder (mm)

  Calculated by equation (4), r2≥1076.5mm, take D2=2*r2 = 2250mm.

Cylinder bottom thickness: t=(1.5~2)*(r2-r1)       (5)

The nominal pressure of the four working cylinders on the side is 80 MPa. Similarly, the structural parameters of the side working cylinder can be preliminarily obtained as follows:

Plunger diameter D=900mm, Δt=10mm, hydraulic cylinder inner diameter D1=920mm, outer diameter D2=1360mm, cylinder bottom thickness t=300mm.

3. Numerical simulation and result analysis of working cylinder

At present, most of the large forging hydraulic presses cylinders use the empirical algorithm of elastic mechanics. According to the basic design parameters, the basic design parameters are determined with reference to relevant data, and then the strength check is performed according to the simplified mechanical model. However, due to the complex structure of the hydraulic cylinder, it is difficult to establish accurate mechanical and mathematical models, especially in the stress concentration zone. Using the finite element method to calculate the hydraulic cylinder, the stress distribution of the hydraulic cylinder can be accurately determined, and then the structural design rationality is analyzed. The main dimensions of the working cylinder are shown in Picture 4.

3.1 Establishment of finite element model

3.1.1 Structural model and unit division

In order to make the calculation of the working cylinder closer to the actual working condition, the six working cylinders are assembled with the upper beam according to the actual conditions. Considering that the deformation of the lower beam has little effect on the working cylinder, the column model is intercepted to half the height.

The working cylinder grid type is selected as the tetrahedral unit C3D4, and the details of the cylinder bottom fillet, the oil inlet and the threaded hole are meshed and subdivided. The four side cylinders are divided into 940,000 units, and the middle 2 The master cylinders are divided into 1.2 million units.

3.1.2 Boundary conditions

(1) A uniform pressure of 31.5 MPa is applied to the inner wall surface of the working cylinder, and the liquid pressure is distributed below the inner wall of the working cylinder.

(2) The friction coefficient μ is set to 0.1, and the contact type is selected as a standard surface-surface contact.

(3) Set the material properties of the working cylinder: Poisson’s ratio λ is 0.3, and elastic modulus E is 206,000 MPa.

(4) The upper beam block lever is pre-tightened: φ200mm (10 pieces), the single pre-tightening force is set to 4000kN, and the pre-tightening mode adopts Bolt load.

(5) Pre-tightening of the column rod: The pre-tightening force should be moderate, and the pre-tightening force will destroy the tie rod; on the contrary, the contact part of the beam and the column will be opened due to the pre-tightening force being too small. The overall preload is taken as 1.4 times the nominal pressure, 280MN is more suitable. Among them, the single preload of 10 φ400mm drawbars is set to 17500kN; the single preload of 12 φ320mm drawbars is set to 11200kN; the preloading method uses Bolt load.

(6) The boundary condition of the solid section is applied to the middle section of the column.

Its numerical model is shown in Picture 5:

3.2 Simulation results and analysis

After the calculation of the numerical model of the working cylinder, the equivalent stress cloud of the working cylinder is observed and analyzed.

3.2.1 Simulation results and analysis of intermediate main working cylinder

The main working cylinder is cut open to observe the internal and external stress distribution of the working cylinder. The equivalent stress cloud diagram of the intermediate main working cylinder is shown in Picture 6:

The analysis of the equivalent stress distribution cloud of the main working cylinder shows the following results:

(1) The average value of the equivalent stress distribution near the inner filling port of the working cylinder is the highest, between 105 and 120 MPa. The highest point of the equivalent stress is 119MP, and the position is on the inner wall of the working cylinder near the lower part of the liquid filling port.

(2) The equivalent stress value of the inner wall of the thick-walled cylindrical part of the working cylinder is relatively high, and the equivalent stress distribution is relatively uniform between 95 and 115 MPa.

(3) The equivalent stress value at the bottom of the working cylinder is relatively low, between 68 and 85 MPa.

(4) The outer wall of the thick-walled cylindrical part of the working cylinder has the lowest equivalent stress value, and the maximum equivalent stress value is only 60MP.

The numerical results show that the maximum equivalent stress of the main working cylinder occurs near the liquid filling port of the inner wall, the value is 119MP, and the working cylinder cylinder material 35 steel has a yield strength of 240MPa after heat treatment, and its safety factor is greater than 2. It can be further proved that the strength of the main working cylinder meets the design requirements.

3.2.2 Side working cylinder simulation results

Picture 7 shows the equivalent stress cloud of the side cylinder.

The analysis of the equivalent stress distribution cloud of the side working cylinder is carried out, and the following results are obtained:

(1) The maximum equivalent stress is generated near the liquid filling port, and its equivalent stress value is 129.5 MPa.

(2) The equivalent stress distribution of the thick-walled cylindrical part of the inner wall of the cylinder is relatively uniform, and the equivalent stress value is higher, and the equivalent stress value is 85~110MPa.

(3) The inner wall of the side working cylinder and the outer surface of the cylinder have uniform stress distribution, and the equivalent stress is low, and the equivalent stress value is mostly below 75MPa.

The side working cylinder material is made of 35 steel. After heat treatment, the yield strength is 240MPa. The numerical calculation results show that the maximum equivalent stress of the side working cylinder is 130MPa, and the safety factor is calculated to be 1.85. Therefore, the strength of the side working cylinder meets the design requirements. 

4. Conclusion

In this paper, the traditional design theory of large forging hydraulic presses is used to calculate the working cylinder of 200 MN forging hydraulic press by formula calculation. Then the finite element analysis software ABAQUS is used to model the working cylinder assembly in three dimensions, and it is used for static finite element simulation calculation. Through the analysis of the equivalent stress of the working cylinder simulation results, the strength of the working cylinder meets the design requirements, which further proves that the calculation result of the traditional formula is correct and feasible in the hydraulic cylinder working cylinder design specification.