Sintered Ceramic Body Stress Control During Cooling
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Solution Overview
Problem
Ceramic processing is labor-intensive, and sintered bodies with residual compressive stress deform easily, leading to detachment issues when covered or joined with materials having different thermal expansion coefficients, limiting design flexibility and durability.
Innovation Solution
A sintered body with a ceramic base material is manufactured using a method that eliminates residual compressive stress by applying a pressure load during cooling, resulting in tensile stress, which enhances durability and adhesion while allowing for flexible design of surface layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If net-molded articles are produced with sintered surfaces used as functional surfaces, then processing labor is reduced, but compressive stress due to heat contraction is retained in the surface causing deformation
Solution Approach 1:
The patent applies a compressive load during the cooling phase before the sintered body is removed from the mold. This preliminary action counteracts the tensile stress that will develop during cooling due to thermal contraction, preventing surface deformation before the functional surface is even exposed. The load is applied in advance during manufacturing to preemptively eliminate the harmful stress.
Solution Approach 2:
The patent changes the stress state parameter in the sintered body by applying an external compressive load during cooling. This transforms the internal stress distribution from tensile (harmful) to compressive (beneficial), thereby improving surface stability and preventing deformation while maintaining the net-molded manufacturing approach.
2Ease of manufacture
If compressive stress is retained in the surface layer, then net-molded production is simplified, but the surface readily deforms when used as a functional surface
Solution Approach 1:
The compressive load is applied during cooling as a preliminary action to establish the desired stress state before the sintered body is removed from the mold and before any subsequent processing or use. This ensures the surface is pre-stabilized against deformation from the outset.
Solution Approach 2:
The patent converts the naturally occurring tensile stress (harmful) into a beneficial compressive stress state by applying an external compressive load during cooling. The harmful thermal contraction stress is transformed into a beneficial compressive residual stress that prevents surface deformation and improves durability.
3Reliability
If a covering layer is applied to improve corrosion resistance, then protection is enhanced, but the covering layer detaches due to thermal expansion mismatch and internal stress
Solution Approach 1:
The patent converts the harmful tensile stress that causes detachment into a beneficial compressive stress state. By applying compressive load during cooling, the sintered body develops compressive residual stress that counteracts the tensile stresses generated during subsequent heating cycles, preventing covering layer detachment and improving long-term adhesion.
Solution Approach 2:
The compressive residual stress is established in advance during manufacturing to counteract the future tensile stresses that will arise from thermal expansion mismatch between the sintered body and the covering layer. This preliminary anti-action prevents the detachment problem before it occurs during service.
4Manufacturing precision
If polishing is performed to create a functional surface, then surface quality is improved, but an altered layer with compressive stress is formed
Solution Approach 1:
The patent extracts or eliminates the harmful compressive stress from the altered layer by applying a tensile load during cooling. This removes the problematic stress component that would otherwise remain trapped in the surface layer after polishing, preventing deformation while preserving the high surface quality achieved through polishing.
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 method produces a sintered body that does not deform readily and allows for high flexibility in surface layer design, improving adhesion and durability, especially when used in optical components.
Implementation Method 1
compressive stress due to heat contraction is retained in the surface
Implementation Method 2
heating is performed under applied pressure followed by cooling under low pressure so that the die can be removed with minimal complication
Data Source
AI summary
There is provided a sintered body that does not readily deform during use and that allows a high flexibility for the design of surface layers, a method for manufacturing the sintered body, and an optical component including the sintered body. The method for manufacturing a sintered body includes a sintered body having a predetermined shape, the sintered body having a ceramic base material, the method for manufacturing a sintered body comprising a step for preparing a ceramic preform, a step for using a predetermined mold having an upper die and a lower die to hot-press the ceramic preform to form a pressure-sintered body, and a step for cooling the pressure-sintered body while applying a pressure load of approximately 5% or more and 100% or less (and preferably approximately 20% or more and 40% or less) of the pressure load applied during the step for forming the pressure-sintered body.