Submitted master’s thesis deals with rotary draw bending of tubes as a subprocess of automobile’s stabilizer bar production. The main goal of the thesis is to clarify the influence of the process parameters of the bend on the resulting shape and properties of the product. Submitted thesis includes theoretical description of the chosen tube bending technology, description of defects and possibilities of their removal. The description of the bending machine used for stabilizer bars production is done afterwards. Practical part of the thesis includes experiments clarifying influence of parameters on the resulting shape of the stabilizer bar.

Plastic  deformation of tubes can be achieved in numerous ways. One of the most useful type is CNC tube bending machines which is used in many industries such as aerospace, automotive, HVAC systems and so on. It is important that all components of system should mate properly after producing and because of this bend shaping requires sensitive operation on each components to ensure regularity of production processes with high quality end-product. Thus, the CNC tube bending industry to become widespread. However it brings some troubleshooting like wrinkling, springback, breakage and ovalisation. This failures depends on geometry of the material such as bending radius, tube thickness and also friction factor between dies and the tube. Effects of all parameters should be examined before generating the theory for a best solution. Therefore, prediction of the required moment for the proper bending process with low cost and shortened production time is needed. All of these requirements can be achieved through a C++ form application program.

The bottleneck of forming small radius tube is that traditional processing methods can¡¦t effectively produce smaller bend radius tube in domestic industry now. First, this study will propose methods without mandrel, based on traditional bending way of rotary draw bending to form small bending radius tubes. This paper investigate results of traditional bending mode without mandrel in second part. By using finite element analysis, find the effects on wall-thinning, wall-thickening and ovility with different processing parameters. Also using the research results to obtain forming ranges. Through heating tubes we explore the possibility of hot forming of parameters and to find the impacts on bending tubes which heating under different parameters. We use the results above to find out the hot forming ranges. In heating and quenching of rotary draw bending experiments, we found that heating tubes under the same processing parameter can effectively enhance the formability and successfully derive better products of small radius bending tubes, to accomplish non-mandrel rotary bending process of small bending radius.

Currently, rotary draw bending is frequently used method in industry. Nevertheless, it has been limited for long time by different types of defects. Submitted thesis deals with the study of the influence the bending radius and wall thickness on the quality of bent. Practical part of the thesis includes experimental rotary draw bending of tubes. The work also solves determining actual values of the wall thickness; ovality, bent shapes, the section modulus in bending and the neutral axis of the tube On the basis of evaluation of criteria are then set the parameters of permissible bend

Master thesis analyzes rotary draw bending of the tubes without using a mandrel. Bending process is accompanied by many defects due to large displacement of formed material. One of the major defects is flattering of the cross section also called ovality. In order to decrease ovality comes up a proposal of the changes to the tool design. Modifications of tool’s geometry are numerically analyzed by finite element method in software ANSYS. According to the results of the simulations an optimized pressure die is manufactured. Several experimental tests are accomplished to verify the effect of the optimized tool design. Approximately 100 bends confirm a decrease of ovality using modified pressure die.

Intensive competition on the global market puts great pressure on manufacturing companies to develop and produce products that meet requirements from customers and investors. One key factor in meeting these requirements is the efficiency of the product development and the production preparation process. Design automation is a powerful tool to increase efficiency in these two processes. The benefits of automating the production preparation process are shortened led-time, improved product performance, and ultimately decreased cost. Further, automation is beneficial as it increases the ability to adapt products to new product specifications with production preparations done in few or in a single step. During the automation process, knowledge about the production preparation process is collected and stored in central systems, thus allowing full control over the design of production equipments. Three main topics are addressed in this thesis: the flexibility of design automation systems, knowledge bases containing conflicting rules, and the automation of the finite element analysis process. These three topics are discussed in connection with the production preparation process of rotary draw bending. One conclusion drawn from the research is that it is possible to apply the concept of design automation to the production preparation process at different levels of automation depending on characteristics of the implemented knowledge. In order to make design automation systems as flexible as possible, the concept of object orientation should be adapted when building the knowledge base and when building the products geometrical representations. It is possible to automate the process of setting up, running, and interpreting finite element analyses to a great extent and making the automated finite element analysis process a part of the global design automation system.

Rotary draw bending, which has very good flexibility and easy tooling, is one of the most preferred bending types for tubular profiles. Cross-section distortion and the spring-back phenomena are commonly faced problems in bending processes. Spring-back is the inevitable problem that is to be solved by manufacturer, generally by overbending. For hollow tubes cross-section distortion is another difficulty since using hollow tubes results in higher strain rates and distortions. During the process the thickness of the hollow tube at the inner surface, which is contacting with the die, increases and the thickness of the tube at the outer surface decreases. Wrinkling is another important defect that occurs at the inner surface of the tube in large diameter thin walled tube bendings. This research compares the experimental results with the finite element analysis of the rotary draw bending process. The aim is to obtain bending characteristics of the two material types, SS304 and St37 and so, to reduce the number of the bending in manufacturing. The main parameters in rotary draw bending process are the bending angle, bend radius, material properties and the geometry of the tube that is to be bent. In this study, to deal with the process, two different materials, three different bending angles and three different tube geometries are used in experiments as well as in finite element analysis. In finite element analysis explicit method is used. It is seen that the experimental results are in good agreement with the numerical results.

Bending process is an important forming process in most industrial fields. Springback and cross-section distortion are commonly faced problems in bending process. Springback behavior of closed and open section beams changes with different parameters such as cross-section type, cross-section dimensions, bend radius and bend angle. For closed sections like tube, the dominating problem is cross-section distortion. The thickness of the tube at intrados (inner surface of tube being in contact with die) increases, whereas the thickness of the tube at extrados (outer surface of tube) decreases. Furthermore, another cross-section distortion type for tubes is flattening at extrados which is undesirable in some manufacturing operations. The present research, using finite element method, focuses on investigating the springback behavior of commonly used aluminum beams which are T-Shaped, U-Shaped and tubular for different cases. A series of analyses is performed for a beam and the changing parameters in the analyses are bend radius and thickness. Furthermore, for tubes, the effects of axial force on springback behavior are investigated. It is seen that the axial force causes stretching and the springback angles are decreased. Moreover, in order to overcome cross-section distortion in flattening for tubes, different internal pressures are used and the effects of internal pressure are investigated. By applying appropriate internal pressure, the flattening distortion is mostly eliminated. Conclusions are drawn revealing springback behaviors and cross-section distortions with respect to bend radius, bend angle, thickness, axial pull and internal pressures. They are in good agreement with other published researches and experimental results. Therefore, the models can be used to evaluate tooling and process design in bending operations.

<p>Intensive competition on the global market puts great pressure on manufacturing companies to develop and produce products that meet requirements from customers and investors. One key factor in meeting these requirements is the efficiency of the product development and the production preparation process. Design automation is a powerful tool to increase efficiency in these two processes.</p><p>The benefits of automating the production preparation process are shortened led-time, improved product performance, and ultimately decreased cost. Further, automation is beneficial as it increases the ability to adapt products to new product specifications with production preparations done in few or in a single step. During the automation process, knowledge about the production preparation process is collected and stored in central systems, thus allowing full control over the design of production equipments.</p><p>Three main topics are addressed in this thesis: the flexibility of design automation systems, knowledge bases containing conflicting rules, and the automation of the finite element analysis process. These three topics are discussed in connection with the production preparation process of rotary draw bending.</p><p>One conclusion drawn from the research is that it is possible to apply the concept of design automation to the production preparation process at different levels of automation depending on characteristics of the implemented knowledge. In order to make design automation systems as flexible as possible, the concept of object orientation should be adapted when building the knowledge base and when building the products geometrical representations. It is possible to automate the process of setting up, running, and interpreting finite element analyses to a great extent and making the automated finite element analysis process a part of the global design automation system.</p>

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