Reusable Mandrel Assembly for One-Sided Cold Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mandrel systems for cold expansion of openings in structural workpieces require disposable split sleeves, leading to high inventory costs and inefficiency, as they can only be used once and necessitate access from both sides of the workpiece.
Innovation Solution
A mandrel assembly with a multi-use expandable outer member that can be slidably supported along a tapered portion, allowing for radial expansion of openings from one side of the workpiece without the need for disposable sleeves, utilizing a biasing member and tool-coupling mechanism for repeated use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a disposable split sleeve is used with a tapered mandrel for cold expansion, then the opening can be expanded from one side of the workpiece, but the split sleeve must be replaced after each use, leading to high inventory costs and inefficiency
Solution Approach 1:
The mandrel is divided into a reusable core mandrel and a replaceable outer member. The outer member can be removed and replaced after each use, while the expensive core mandrel remains in service. This segmentation allows the system to achieve one-sided access capability without requiring complete disposal of the entire mandrel assembly.
Solution Approach 2:
The core mandrel assembly is designed to be reusable across multiple operations by retaining the functional tapered portion and interchangeably mounting different outer members. This multi-functionality eliminates the need for disposable complete mandrels while maintaining the one-sided access capability for cold expansion.
2Strength
If a tapered mandrel with split sleeve is used for cold expansion, then residual compressive stress is created around the opening, but both sides of the workpiece must be accessible for operation
Solution Approach 1:
Instead of requiring the mandrel to be inserted from the blind side and pulled through, the system inverts the approach by inserting the outer member from the accessible side and using the tapered portion to expand the opening in reverse, eliminating the need for two-sided access while maintaining stress induction capability.
3Manufacturing precision
If a disposable split sleeve is used for each opening expansion, then proper radial expansion can be achieved, but a large inventory of split sleeves must be maintained
Solution Approach 1:
The core mandrel assembly serves multiple operations by retaining its precise tapered geometry and interchangeably mounting outer members for different opening sizes. This eliminates the need for inventorying multiple complete mandrel assemblies while maintaining manufacturing precision for radial expansion.
Solution Approach 2:
By segmenting the mandrel into a reusable core and replaceable outer members, the system maintains precision components in service while only requiring replacement of simpler outer members, dramatically reducing inventory requirements while preserving radial expansion accuracy.
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 efficient and cost-effective cold expansion of multiple openings from one side of the workpiece, reducing waste and inventory needs, while maintaining the benefits of residual compressive stresses without plastic deformation of the mandrel.
Implementation Method 1
an outer member (46) slideably supported along a tapered portion (56) of the rod (40) and biased by a biasing member (44)
Implementation Method 2
The cold expansion process usually employs a tapered mandrel forcibly drawn through the opening to cause a radial plastic flow of material in an annular zone around the opening
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A mandrel assembly has a mandrel, a biasing member, and a outer member. The biasing member biasly maintains the outer member in a first position, which corresponds to a contoured portion of the mandrel, when the outer member is either on the access or the blind side of a workpiece. The biasing member is compressible to allow the outer member to move into a second position as the outer member is moved through an opening in the workpiece. In the first position, the outer member includes a maximum outer circumference that is larger than the opening of the structural workpiece. In the second position, the outer member includes a maximum outer circumference that fits within the opening of the structural workpiece.