3D-Printed Bellows Separator for Uniform-Stress Hydraulic Accumulators
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Solution Overview
Problem
Existing hydraulic accumulators face challenges in manufacturing efficiency and durability due to the need for individual production of bellows sizes, which leads to increased manufacturing effort and stress concentration in membrane materials, resulting in potential material failure.
Innovation Solution
A hydraulic accumulator is manufactured using a single, one-piece membrane bellows produced through 3D printing processes like electron beam melting or selective laser melting, with arc-shaped deflection points and acute angles between adjacent membrane surfaces, ensuring uniform stress distribution and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual tube cylinders are manufactured for each bellows size through continuous longitudinal seam welding, then manufacturing precision is maintained, but manufacturing effort and time increase significantly
Solution Approach 1:
The bellows is segmented into multiple membrane discs that can be manufactured separately and then assembled through welding. This allows parallel production of multiple components, improving manufacturing efficiency while maintaining precision through standardized disc production and controlled welding processes.
Solution Approach 2:
A single membrane disc design can serve multiple bellows sizes by varying the number of discs or their arrangement, reducing the need to manufacture entirely different tube cylinders for each bellows size while maintaining manufacturing precision.
2Ease of manufacture
If membrane discs are welded together to form the metal bellows, then the bellows can be assembled from standardized components, but stress concentration occurs at the weld locations leading to potential material failure
Solution Approach 1:
The membrane discs incorporate localized geometric features such as rounded corners, relief cuts, or reinforcement zones at the weld locations. These local modifications distribute stress more evenly around the weld areas, reducing stress concentration while maintaining the ease of assembly through standardized disc components.
Solution Approach 2:
The membrane disc design includes built-in stress relief features such as rounded corners or geometric transitions that preemptively reduce stress concentration at weld locations before operational loads are applied, preventing material failure while maintaining assembly simplicity.
3Device complexity
If the membrane surfaces are arranged parallel to each other in the initial state, then the bellows structure is simplified, but unfavorable stress introduction occurs during extension and contraction processes
Solution Approach 1:
The membrane discs are designed with asymmetric geometric features such as non-parallel initial orientations, tapered edges, or specific curvature profiles that create more favorable stress distribution patterns during extension and contraction, while the overall bellows structure remains relatively simple.
Solution Approach 2:
The membrane discs incorporate curved surfaces, rounded edges, and arc-shaped transitions instead of sharp angles or flat surfaces. This curvature distributes stress more evenly during bellows operation, improving strength while maintaining acceptable structural complexity.
4Strength
If arc-shaped deflection points with semicircular cross-sections are used in bellows folds, then wall thickness reduction is prevented, but manufacturing effort increases due to individual fold production
Solution Approach 1:
The bellows is divided into separate membrane discs that can be manufactured using standardized forming processes and then assembled. This segmentation allows each disc to be produced efficiently while maintaining the beneficial arc-shaped deflection points and semicircular cross-sections at the fold locations.
Solution Approach 2:
The manufacturing process parameters for membrane disc formation are optimized to create the desired arc-shaped deflection points and semicircular cross-sections more efficiently, reducing the overall manufacturing effort while preserving the strength benefits of these geometric features.
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
The 3D printed bellows design achieves uniform stress distribution and enhanced durability, reducing material failure and enabling long-term reliable operation with rapid response behavior under dynamic stress.
Implementation Method 1
Electron beam melting has proven particularly suitable as a 3D printing method. In electron beam melting, a metal powder is melted layer by layer
Implementation Method 2
Selective laser melting, in which a metal powder is melted only locally, is equally suitable
Implementation Method 3
a fluid chamber for receiving a gas filling that generates a preload pressure
Implementation Method 4
Hydraulic forming processes are predominantly used for this
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
2. A separating element, in particular for a hydraulic accumulator, such as a bellows accumulator produced by a 3D printing method, consists of a single membrane which is deflected arcuately, as viewed in cross section, while forming a plurality of bellows folds (28) at deflection points (30) which outwardly and inwardly delimit the bellows folds (20) and, in order to obtain an isotensoid or substantially isotensoid distribution of stress in the membrane, the imaginary extensions (32) of the membrane surfaces (34) adjacently adjoining each deflection point (30) enclose an acute angle (α) with one another, at least in an initial state.