Rotationally Shifted Magnetic Sheets for Thermal Expansion Mismatch
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Solution Overview
Problem
Two-component magnetic sheets produced using stencil printing processes face challenges with differing thermal expansion coefficients, leading to mechanical stresses, warping, and reduced mechanical and magnetic properties due to incompatible material pairings.
Innovation Solution
The development of a laminated core with rotationally shifted material layers, each with the same layout, forms a magnetic sheet that mitigates thermomechanical stresses by creating a gradient thermal expansion coefficient, enhancing mechanical strength and reducing torque fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If different material components with different thermal expansion coefficients are sintered together to form a magnetic sheet, then mechanical strength is improved, but thermal expansion mismatch causes high mechanical stresses, warping, and cracks during cooling
Solution Approach 1:
The magnetic sheet is divided into multiple material layers, each containing different material components arranged in a specific layout. By segmenting the sheet into layers with identical layouts that are rotationally shifted relative to each other, the patent creates a structure where thermal expansion stresses are distributed and compensated across layers, preventing warping and cracks while maintaining mechanical strength
Solution Approach 2:
The patent introduces rotational asymmetry by shifting the layout of material components in each layer by a specific angle relative to adjacent layers. This asymmetric arrangement creates overlapping regions where the thermal expansion coefficients effectively average out, reducing thermal stress concentration and improving structural reliability during temperature changes
2Reliability
If multiple material layers with identical layouts are rotationally shifted by an angle α, then thermal expansion stresses are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent changes the angular parameter of material layer layouts, specifying that adjacent layers are rotated by an angle α between 5° and 15° relative to each other. This parameter change creates overlapping regions that average thermal expansion coefficients, reducing stresses while maintaining manufacturability through defined angular ranges
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 solution results in a magnetic sheet with increased mechanical strength, reduced intrinsic stresses, and improved tolerance to high temperatures, enabling higher operational speeds and stability in electrical machines.
Implementation Method 1
the printing paste contains metal powder that plays a functional role in the final component. The screen printing technique produces a green body which, after further thermal treatment, is usually first debindered and then subjected to a sintering process at a higher temperature. During this process, the metallic powder grains sinter together to create a structured sheet, the magnetic sheet.
Implementation Method 2
these different thermal expansion coefficients lead to the formation of high mechanical stresses in the connection or seam areas between these material components, particularly during cooling from the sintering temperatures to room temperature.
Data Source
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AI summary
The invention relates to an additively manufactured rotationally symmetrical magnetic sheet (2), comprising at least two material layers 4, 6, for a laminated core (8) of an electric machine (10), wherein in each material layer 4, 6 at least two material components (12, 14) separated from each other in planar extent are present - a first material component (12) and a second material component (14) wherein - the material components 12, 14 form a material layer layout 16 characterized in that - the at least two material layers 4, 6 have the same material layer layout 16 of the two material components 12, 14 and the layout 16 of the at least two material layers 4, 6 is rotationally shifted by an angle α.