Modeling, Simulation and Verification of a New Swaging ...Modeling, Simulation and Verification of a New Swaging Process using DEFORM® Dong Jae Lim1, Won Jee Chung1, Sang Suk Sul1

Modeling, Simulation and Verification of a New

Swaging Process using DEFORM®

Dong Jae Lim1, Won Jee Chung1, Sang Suk Sul1

1School of Mechatronics, Changwon National University, Changwon, Gyeongsangnam-do, South Korea

Abstract - Rotary swaging process is a method of forging automotive drive shafts. In this paper, in order to improve the efficiency and productivity of the rotary swaging automation process, a new 2-hammer forging method will be proposed by applying TRIZ. We will simplify the materials and hammers for high accuracy of comparative analysis of existing and proposed methods under the same boundary conditions and then performed 3D modeling by SolidWorks. And we will compare the stress trends of proposed model using ANSYS Workbench and verify the feasibility by comparing the simulation results using DEFORM. Using the proposed method can reduce the production cost and improve the efficiency in the automation process by reducing the power source, compared to the existing method.

Keywords: DEFORM, 6 Step Creativity of TRIZ(6SC), Rotary swaging process, Forging, Plastic deformation

1 Introduction Monoblock Tubular Shaft (i.e., MTS), an automotive

power transmission axis, is an automobile axial part, which transfers the torque generated in an engine to wheels. The MTS moves up and down according to suspension buffers and has vehicle body joints that can change angles according to the operation of a steering system. This tubular shaft is mounted between the transmission and the differential gear box, and thus transmits power and is widely used in a front wheel drive vehicle, a rear wheel drive vehicle and a four wheel drive vehicle. [1]

Many studies in the automobile industry have been performed in various fields, such as improvement of automobile fuel efficiency, structural lightweight and improvement of engine performance for environment protection, development of filtration devices for reducing exhaust gas, development of technology for reduction of noise & vibration and thereby the improvement of passenger safety. [2]

Until recently, as methods of forming an automobile shaft, a solid shaft drawing method or friction welding method has been used, as shown in Fig. 1. The use of the solid shaft cannot be competitive in that weight lightening is required to improve fuel efficiency, and the friction welding method has a

problem that safety is low because cracks may occur in friction welding portions due to vibration and impact. In addition, the method of forging a shaft using a drawing or extrusion molding method has a limitation that the amount of change in shaft thickness before and after processing should be an increase amount in proportion to the material volume. This can hinder the shaft from being increased in strength.

(a) Solid shaft drawing method

(b) Friction welding method

Fig. 1 Methods of forming an automobile shaft

However, the rotary swaging technology can have an

advantage of weight lightening, compared to the use of the solid shaft because it processes using hollow shaft. This technology can prevent the occurrence of cracks in the joints at the time of using the friction welding method through the incremental processing method which has no joints and also increase the safety. In addition, this technology enables to secure thickness of a cross section that exceeds the thickness change according to the simple volume change during plastic working that strikes steel materials, which means an increase in rigidity and an increase in safety. [2]

The rotary swaging process is a process of producing various forms of products by changing sectional shapes of bars, tubes and wires. It mainly produces products with rotational symmetry but also produces non-circular products with axial symmetry (such as products with hexagonal, octagonal, elliptical or decagonal cross-section) when using an outer ring rotational forging machine. Moreover, the rotary swaging process can produce high precision products in a multi-stage production line quickly and inexpensively so that

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ISBN: 1-60132-494-4, CSREA Press ©

it nowadays takes a key role in developed countries, especially Germany. [3]-[4]

As the industry highly grows, it is urgently necessary to lighten products, to upgrade the quality, and to reduce the cost. Therefore, advanced countries are spurring a new process development because it is required to process new materials with excellent mechanical properties. The rotary swaging process is a process that draws newly attention due to the process excellence such as the high accuracy, high quality and productivity improvement of products, and its application range is greatly being expanded by being used for producing automobile parts and machinery parts.[2]

In this paper, we will propose a method to improve the efficiency of punch type rotary swaging process, the process of processing an automobile drive shaft using the practical TRIZ (the abbreviation of Russian for “Theory of Solving Inventive Problem”) that 6SC (6 Step Creativity) applied. [5] Based on the modeling of the hammers and tubes by using Solidworks®, we will use ANSYS®, the structural analysis tool, to compare the stress trends of the existing and proposed methods. Finally, we will simulate the forming process using DEFORM®, a tool for plastic deformation analysis, and verify the validity of the proposed process through the results.

2 Rotary swaging method

The striking methods of the hammer are various: a method using a cam, a method using a hydraulic pressure, and a method using a ball screw. The rotary swaging process is basically performed by striking a material by using the reciprocating motion of a hammer. In this paper, a hammer striking method using a ballscrew, which is advantageous for accurate simultaneous striking in various directions, was used to improve roundness directly related to product quality.

Figure 2 shows the conventional equipment of rotary swaging forging process, and Fig. 3 shows a progressive forging sequence of the rotary swaging automation process. In the forging preparation process, a material feeding device places the material in the center of the equipment. Thereafter, three forging hammers apply constant striking simultaneously in the central direction of the axis of the material. Accordingly, the material feeding device rotates the material at a constant angle and pushes the material toward the forging hammer at a constant feed rate so that all sides of the material are gradually formed. When constructing an automation process, rotating the material at every constant angle and then feeding the material at a constant velocity, and finally simultaneous striking by three hammers can have directly an influence on the roundness of the product. At this time, setting of a stroke which is the distance between the top dead center and the bottom dead center of the hammer, based on the outer diameter of the material, enables formation of shafts with various thicknesses.

Fig. 2 Conventional apparatus of rotary swaging forging process [2]

Fig. 3 Progressive forging process

3 Proposal of New Rotary Swaging Automation Process using 6 Step Creativity of TRIZ

6 Step Creativity (6SC) of TRIZ is a practical TRIZ which has an added new methodology and does not have difficult or mostly unavailable methodologies through removal or modification from the existing TRIZ. [5] In order to improve the efficiency of the rotary swaging automation process, a new 2-hammer forging method will be proposed by applying 6 step (3.1 to 3.6) creativity of TRIZ. [5]

3.1 Diagrammatic Representation of Problem

The basic configuration of the punch type rotary swaging equipment is shown in Figs. 4 and 5. As shown in Fig. 4, the swaging equipment consists of 1) a bed to support the entire equipment, 2) a material feeding device to perform the transportation of the material at a constant rate and its rotation at a constant angle, and 3) a forging hammer to be placed at an interval of 120° and perform a reciprocating striking motion in the vertical direction. Figure 5 briefly shows the material to be forged and the hammer section. The red arrow indicates the vertical reciprocating motion of the striking hammer, and the blue arrow indicates the material’s transportation and rotation movement by the material feeding device.

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Fig. 4 Simplified rotary swaging equipment

Fig. 5 Simplified forging method

3.2 Functional Analysis in Systems Functional analysis in systems consists of a technical

system, target objects, and environmental elements. All technical systems are represented by rectangles, and target objects represented by circles.[6] Figure 6 indicates the system of the rotary swaging process. The forging hammers, feeding device, bed, and motor were set as the technical system and the tube that is a processing target was set as the target object.

Fig. 6 A system functional analysis of the rotary swaging system

3.3 Assumption of Ideal Final Result (IFR) 1) If the number of hammers used for the forging is large,

the production speed of the material can be increased. 2) If power to be used is minimized, the production cost

can be reduced.

3.4 Contradiction Contradiction is one of important concepts of TRIZ, and

it refers to a situation that when trying to improve one characteristic in a target system, another characteristic of the

system are weakened. There are two types of contradictions: a technical contradiction and physical contradiction. [7] The technical contradiction represents the conflict between two different parameters, but the physical contradiction appears when two different properties are required from the same element of a technical system. [5] In the rotary swaging system, a technical contradiction occurs. The contradiction is that the number of forging hammers should be large to expand the area being processed at one time, thereby reducing the time of the shaft forging process and improving the productivity, but the large number of forging hammers increases the number of power sources required for moving the hammers, thereby increasing the cost of production.

3.5 Element-Interaction Analysis

Figure 7 shows the forging hammers, feeding device, and element-interaction of process efficiency, which are key elements of the rotary swaging system. The variables of each factor affecting the production efficiency of the product are shown in Fig. 7. The variables that affect the efficiency improvement of the rotary swaging equipment automation process, which is the purpose of this paper, were the number of forging hammers and the rotation angle of the feeder device.

Fig. 7 Element-Interaction of Rotary Swaging System

3.6 Solutions and Evaluation It is very important to finally select and evaluate various

solutions and variables for the problems obtained through the 5 steps of the 6SC. [5] When selecting the variables to improve the efficiency of the forging process, it is necessary to consider not only the improvement of the forging speed but also the cost required for increasing the forging speed. If the number of forging hammers is large, the area that can be formed at one time is widened, thereby improving the productivity. But the large number of forging hammers also increases the number of power sources required for moving the hammers. Therefore, reducing the number of power sources required in an automation system with the same production rate will improve the efficiency of the automation system. Therefore, we propose the following solution which will be verified using the analysis tool of ANSYS : 2 Hammer Forging Method - Maintain the number of three



hammers used for forging. However, if the quality of the product does not change even when one hammer is fixed and two hammers strike, the number of necessary power sources can be reduced.

Fig. 8 Proposed Solution

4 Stress Tendency Comparison through Structural Analysis

In order to compare the 2-hammer forging method obtained by the TRIZ method using 6SC, we analyzed the existing forging method (so-called 3 hammer forging method) that three hammers strike the material by performing a linear reciprocating motion. After that, we analyzed the proposed method under the same conditions. The variables applied to the analysis are indicated in Table. 1.

TABLE 1 SIMULATION CONDITIONS

Parameter Unit Value

The material of Tube - SM15B

The material of Hammer - SM45C Outer diameter of Tube

before forging mm 38.1

Outer diameter of Tube after forging mm 28

Thickness of material mm 3.4

Forging Speed RPM 100

Forging Force Ton 2

Split angle 30

Figure 9 is a side view of material forging for the 3-

hammer forging method. It shows that stress was equally applied from all directions, resulting in uniform strain. Figure 10 is a front view and a cross-sectional view of material forging for the 3-hammer forging method. They have symmetrical stress distribution and symmetrical strain distribution about their each center axis from all directions.

Fig. 9 Side view of equivalent stress in 3-hammer forging method

Figs. 10 Front view and cross-sectional view of equivalent stress in 3-hammer forging

Figure 11 is a side view of material forging for the

proposed 2-hammer forging method. Like the 3-hammer forging method, it has uniform stress and uniform strain from all directions. Figure 12 is a front view and a cross-sectional view of material forging for the 2-hammer forging method. Like the 3-hammer forging method, they have symmetrical stress distribution and symmetrical strain distribution about their each center axis from all directions, but their values are slightly different.

Fig. 11 Side view of equivalent stress in 2-hammer forging

Figs. 12 Front view and cross- sectional view of equivalent stress in 2-hammer forging method

5 Simulation of Existing Method and Proposed Method using Plastic Analysis

The analysis using the ANSYS® Workbench takes a long time in analyzing the dynamic analysis of the sequential motion, and it is difficult to converge the values, so it is difficult to expect accurate values for the plastic deformation. In this section, DEFORM®, a plastic analysis tool was used for the analysis. The analysis of the proposed design model, 2-hammer method, was performed and the results were compared with the 3-hammer method. The parameters of the forging process are indicated in Table 1. The forging simulation was performed until the tube was inserted in the

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extent of 140 mm, which is equivalent to the shape of which the inner diameter is 28 mm with its length 10 mm.

Figure 13 shows a side view of the result of material forming for the 3-Hammer forging method. Stresses were uniformly distributed on all sides and showed uniform deformation. Figure 14 shows a side view of the result of material forming for the 2-Hammer forging method. As with the 3-Hammer forging method, the stresses of 2-Hammer are also uniformly distributed on all the surfaces and uniformly deformed. Figure 15 shows the cross sections of 3-Hammer and 2-Hammer forgings. As a result of 8-point diameter measurement on the cross section, average diameter of the 3-Hammer method was 26.96mm, and average diameter of the 2-Hammer method was 27.27mm. This satisfied the target value of 28mm 0.15 mm. Since the quality of the 3-Hammer method is satisfied with the 2-Hammer method, it is verified that the method of adopting the proposed 2-Hammer is valid.



Fig. 15 Cross-sectional comparison between 3-hammer method

and 2-hammer method

6 Conclusion In this paper, a study was aimed to improve the

equipment efficiency in the development of rotary swaging process. Using TRIZ, we focused on the components of rotary swaging equipment. As the number of the hammers is large, the area that can be forged at one time becomes expanded more, thereby reducing the time of the shaft forging process and improving the productivity. However, it also increases the number of power sources required for the linear reciprocating striking motion of the hammers, thereby increasing the cost of production. In order to solve this contradiction, this paper proposed a method to obtain quality, productivity, and power saving by reducing the number of striking hammers used in forging to two while one hammer is fixed and two hammers strike.

Prior to the analysis, hammers and tubes were modeled briefly to reduce the analysis time by using Solidworks®. The stress trends were compared using ANSYS®, a structural analysis tool, and there was no significant difference. In dynamic simulation using ANSYS®, it takes a lot of time and it is difficult to converge the calculated values in the plastic region. Therefore, the process simulation was performed by using DEFORM®, a plastic deformation analysis tool. As the results verified in the previous section, 2-Hammer method and 3-Hammer method satisfies the target roundness. Thus the result of 2-Hammer method was the same as that of 3-Hammer method. Through process simulation using the softwares (i.e., Solidworks®, ANSYS®, DEFORM®), we were able to decide the development direction toward 2-Hammer method before the actual machine for rotary swaging process was manufactured.

7 Reference [1] S. S Sul, “A Study on 4-Hammer Radial Impact Forging Method for

Development of Monoblock Tubular Shafts for Vehicle”, Changwon Univ, Jun 2017.

[2] S. J. Lim, N. K. Lee and T. W. Oh and J. H. Lee, “Forging Process of the Automotive TDS (Tube Drive Shaft) by the Rotary Swaging Process”, The Korean Society For Technology of Plasticty, Vol. 12, no. 6, pp 558-565, Octover 2003.

[3] R. Hebdzynski, S. Kajzer and R. Kozik, "Forging on the four-lever arms swaging machines", J. of Mater. Proc. technol., Vol. 64, No. 1/3, pp.199-206, 1997.

[4] ASM Metals Handbook, Forging, "Rotary Swaging of Bar and Tubes", Vol.4, pp.333~346, 1969.

[5] H. J. Kim, “Practical TRIZ with 6 levels of creativity”, February 2006.

[6] S. J. Lee, W. J. Chung, H. J. Kim, G. G. Kim, J. H. Kim, “A Study on Optimal Design of Piece Removing Automation System Using TRIZ and Brainstorming, Journal of the Korean Society of Machine Tool Engineers, Vol. 17, No.6, December 2008.

[7] W. J. Chung, J. M. Kim, K. B. Park, J. H. Ju, O. C. Sin, “A Study on design of polishing film transfer guide by using TRIZ”, Korean Society Of Precision Engineering, October 2006.



Modeling, Simulation and Verification of a New Swaging ...Modeling, Simulation and Verification of a New Swaging Process using DEFORM® Dong Jae Lim1, Won Jee Chung1, Sang Suk Sul1

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