Asymmetrical Die Bending for Pipes with Low Radius-to-Diameter Ratio
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Solution Overview
Problem
Conventional bending methods are unsuitable for pipes with bending radius to outer diameter ratios less than 3, and the presence of integral radial branches complicates precise bending, especially in high-risk applications like nuclear power stations where welding is not allowed.
Innovation Solution
An asymmetrical die with a top die half and bottom die half, featuring an asymmetrically arranged punch and seat, allows for precise bending of pipes with integral radial branches by performing asymmetrical bending and multi-step deformation processes, including heating and machining, to achieve the required curvature and branch formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional bending machines are used, then bending can be performed on standard pipes, but bending with R/D ratio less than 3 cannot be achieved
Solution Approach 1:
The patent employs an asymmetrical die configuration where the top die half and bottom die half have different geometries. The top die half includes a punch with a specific profile while the bottom die half has a corresponding seat, creating an asymmetrical bending zone that enables precise control of the bending process for low R/D ratios. This asymmetry allows the pipe to be bent to tight radii while maintaining dimensional accuracy and preventing deformation of integral branches.
2Reliability
If integral radial branches are present during bending, then continuity and leak prevention are ensured, but bending precision deteriorates especially when branch base is adjacent to curvature start
Solution Approach 1:
The asymmetrical die design creates different local conditions along the pipe circumference during bending. The top die half applies controlled pressure through the punch while the bottom die half provides support through the seat, creating a localized bending zone that spares the integral branches from excessive stress. This local differentiation of loading conditions allows precise bending even when branch bases are adjacent to the curvature start, maintaining both reliability and precision.
3Device complexity
If symmetrical bending is performed, then simple die design is achieved, but precise control for low R/D ratios and integral branches is not possible
Solution Approach 1:
The patent deliberately introduces asymmetry into the die structure with the top die half containing a punch of specific profile and the bottom die half containing a corresponding seat. This asymmetrical configuration, while increasing device complexity, provides the necessary control mechanisms to achieve precise bending for low R/D ratios and pipes with integral branches, demonstrating that the increased complexity is justified by the significant improvement in manufacturing precision.
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
Enables reliable and precise bending of pipes with low bending radius to outer diameter ratios and forms integral transverse branches, ensuring continuity and avoiding leaks, even when bending starts near the branch base, which was not achievable with prior methods.
Implementation Method 1
heating said straight article
Implementation Method 2
bending of the article by means of closing of the two die halves
Data Source
AI summary
Method for bending tubular articles with a relative ratio of the bending radius (R) and the outer diameter (D) of the finished pipe which is less than 3, comprising the following steps: forging an article made of material with a predefined composition depending on the final use and with a predefined length (L) in the longitudinal direction and an outer diameter (D); providing a die having an asymmetrical bottom die half with seat for the pipe; and a top die half with punch asymmetrically arranged in the longitudinal direction (X-X) with respect to the vertical center axis of the die; heating the article in an oven to the required temperature for forging depending on the specific composition of the material; positioning the article inside the bottom die half in the longitudinal direction; closing of the two die halves so as to start bending of the article; opening the die; and extracting the bent article.