Hollow Cylindrical Workpiece Forming for Thin-Wall Torque Strength
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Solution Overview
Problem
Existing methods for producing hollow-cylindrical workpieces, such as hollow shafts, often result in components that are either too heavy or lack sufficient strength, as they struggle to balance weight reduction with torque transmission requirements.
Innovation Solution
A method involving bore spinning and subsequent flow-ironing of a solid starting workpiece to create a hollow-cylindrical shape with a reduced wall thickness and increased strength, utilizing a spinning mandrel and forming rollers to produce an uninterrupted fiber flow, which is then further enhanced through targeted temperature control and shaping processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If drilling or rotary swaging is used to produce hollow shafts, then weight is reduced, but strength and torque transmission capability deteriorate
Solution Approach 1:
The process is divided into two distinct stages: bore pressing to create the hollow form, followed by flow-ironing to strengthen the wall. This segmentation allows each process to optimize for its specific function - weight reduction in the first stage and strength enhancement in the second stage - resolving the contradiction between lightweight design and torque transmission capability
Solution Approach 2:
The bore pressing process performs preliminary shaping to create the hollow cylindrical form with uninterrupted fiber orientation before the flow-ironing process. This preliminary action establishes the basic geometry and material structure, enabling the subsequent flow-ironing to focus exclusively on strengthening the wall without compromising the weight advantage
2Weight of moving object
If wall thickness is reduced to minimize weight, then moment of inertia decreases, but structural strength deteriorates
Solution Approach 1:
The flow-ironing process changes the material parameters by applying complex stress states that strengthen the grain structure and increase wall strength. This parameter change allows the thin-walled structure to maintain high strength despite reduced wall thickness, resolving the contradiction between weight minimization and structural reliability
3Strength
If chipless forming processes are used, then material structure with uninterrupted fiber orientation is created, but process complexity increases
Solution Approach 1:
The bore pressing process acts as an intermediary that creates the hollow form while preserving fiber orientation, preparing the workpiece for the subsequent flow-ironing process. This intermediary step enables the final process to achieve high strength without requiring equally complex equipment, as the material structure is already optimized from the first stage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method efficiently produces hollow-cylindrical workpieces with a relatively small wall thickness and high strength, effectively addressing the need for lightweight yet robust components by maintaining the advantageous material structure from bore spinning while enhancing it through flow-ironing.
Implementation Method 1
The application of the forming roller creates a complex stress state in the workpiece, enabling chipless forming with axial insertion of the die
Implementation Method 2
the sleeve section is stretched to a second length, which is greater than a first length, and to a second wall thickness, which is smaller than the first wall thickness
Implementation Method 3
By controlling the temperature during the individual process steps, targeted cold hardening, especially during stretching and pressure rolling, can be achieved and adjusted
Data Source
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AI summary
The invention relates to a method for producing a hollow cylindrical workpiece from a solid starting workpiece, in which a cup-shaped intermediate form is produced in the solid starting workpiece without the use of cutting tools by bore forming, whereby a die is axially pressed into the starting workpiece and at least one forming roller is simultaneously positioned against an outer surface of the outer workpiece. This intermediate form comprises a solid bottom section and an adjoining sleeve section with a first length and a first wall thickness. The cup-shaped intermediate form is then subjected to a stretching and forming process, in which the sleeve section is stretched to a second length, which is greater than the first length, and to a second wall thickness, which is less than the first wall thickness.