Sintered Body Density Gradient Mold Design
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Solution Overview
Problem
Existing methods for producing sintered bodies with complex shapes and reduced weight and cost are limited by the need for uniform density and the risk of mold damage during compaction.
Innovation Solution
A method involving the creation of powder compacts with high-density and low-density portions, where the powder compact is compressed into a mold with a controlled stress distribution to prevent mold damage, allowing for efficient machining and sintering into a sintered body with varying densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the powder compact is compressed into a mold with complex cavity shape, then the sintered body can have complex shapes, but the maximum stress on the mold inner perimeter surface increases causing mold damage
Solution Approach 1:
The patent changes the geometric parameters of the mold cavity by introducing protrusions and recesses that modify the stress distribution. By optimizing the shape parameters (protrusion depth, recess depth, width) relative to the compact dimensions, the maximum stress ratio is controlled to be 2.6 or less, preventing mold damage while enabling complex cavity shapes.
Solution Approach 2:
The patent employs curved surfaces in the mold cavity design, particularly in the protrusions and recesses, to distribute stress more evenly. The rounded transitions and curved geometries avoid sharp corners that would concentrate stress, thereby reducing the maximum stress ratio on the mold inner perimeter surface.
2Strength
If the entire powder compact is compressed to high density, then the sintered body has high strength, but the weight increases and material usage is inefficient
Solution Approach 1:
The patent applies different compaction densities to different regions of the powder compact. The protrusions are compressed to high density (≥93% relative density) to provide strength-critical areas, while the recesses maintain lower density to reduce weight. This local differentiation of density achieves both high strength and weight reduction.
Solution Approach 2:
The patent segments the powder compact into distinct high-density and low-density portions by incorporating protrusions and recesses during compaction. This segmentation allows the high-density regions to be localized only where mechanical strength is required, while other portions can be lighter, optimizing the overall weight-strength ratio.
3Manufacturing precision
If the mold cavity has sharp corners and complex geometry, then the sintered body can have precise shapes, but the stress concentration causes mold damage
Solution Approach 1:
The patent uses curved surfaces and rounded transitions in the mold cavity design, particularly at the protrusions and recesses, to eliminate sharp corners. These curved geometries distribute stress more evenly across the mold inner perimeter surface, preventing stress concentration while still enabling precise complex shape formation.
Solution Approach 2:
The patent optimizes the dimensional parameters of the protrusions and recesses (depth, width, spacing) to control stress distribution. By adjusting these parameters, the maximum stress ratio is kept at 2.6 or less, preventing mold damage while maintaining the ability to form precise complex shapes.
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 enables the production of sintered bodies with complex shapes and reduced weight by minimizing mold damage and optimizing material usage, while maintaining mechanical characteristics such as high rigidity and abrasion resistance.
Implementation Method 1
compressing the raw material powder injected into a mold
Implementation Method 2
sintering the machined compacted part to make a sintered body
Data Source
AI summary
A powder compact containing powder of inorganic material having a shape of a circular cylinder, a circular tube, an elliptical cylinder, or an elliptical tube, wherein a high-density portion situated on one of an inner circumference side and an outer circumference side of the powder compact and a low-density portion situated on another one of the inner circumference side and the outer circumference side of the powder compact are provided, wherein a relative density of the high-density portion is greater than or equal to 95%, and a relative density of the low-density portion is less than 93%, and wherein a difference in relative density between the high-density portion and the low-density portion is greater than or equal to 3%.