Bonded Element for Honeycomb Structure Thermal Stress
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Solution Overview
Problem
Conventional honeycomb structures for diesel particulate filters face challenges in thermal shock resistance during regeneration, leading to cracking and defects due to insufficient stress relaxation and bonding material properties.
Innovation Solution
A bonded element with a bonding material layer having a Young's modulus of 2-18% and an average linear thermal expansion coefficient of 70% or less than the honeycomb segments, composed of fillers and a matrix with specific thermal expansion coefficients and porosities, is used to integrate honeycomb segments, reducing thermal stress and preventing cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bonding material layers are used to integrate honeycomb segments, then the structure can be assembled and bonded together, but thermal stress causes cracking and defects during regeneration
Solution Approach 1:
The bonding material layer's physical parameters are specifically controlled: Young's modulus set at 2-18% of the honeycomb segment material and thermal expansion coefficient at 70% or less of the segment material. These parameter changes enable the bonding layer to flexibly accommodate thermal expansion differences, reducing thermal stress while maintaining bonding strength.
Solution Approach 2:
The bonding material is designed as a composite material with specific filler content (30-70 mass%) and controlled porosity (20-80%). This composite structure combines the benefits of fillers (for strength and thermal stability) with the matrix material, creating a bonding layer that simultaneously provides strong adhesion and effective stress relaxation.
2Reliability
If the Young's modulus of bonding material is lowered to relax thermal stress, then thermal shock resistance improves, but bonding strength may be insufficient
Solution Approach 1:
The Young's modulus is precisely controlled within the range of 2-18% of the honeycomb segment material's Young's modulus. This optimized parameter range ensures the bonding layer is soft enough to relax thermal stress yet maintains sufficient stiffness to provide adequate bonding strength.
Solution Approach 2:
By formulating the bonding material as a composite with 30-70 mass% fillers and controlled porosity, the material achieves an optimal balance between softness (for stress relaxation) and strength (for bonding). The filler network provides structural support while the matrix and porosity provide flexibility.
3Strength
If filler content in bonding material is increased to improve strength, then bonding strength increases, but thermal expansion coefficient increases reducing stress relaxation
Solution Approach 1:
The thermal expansion coefficient of the bonding material is controlled to be 70% or less of the honeycomb segment material, regardless of filler content. This is achieved by selecting fillers with appropriate thermal expansion properties and optimizing the filler-matrix composition ratio.
Solution Approach 2:
The composite formulation with 30-70 mass% fillers creates a synergistic effect where the filler network provides strength while the matrix material (occupying 30-70 mass%) controls the thermal expansion behavior, ensuring the overall thermal expansion coefficient remains low for effective stress relaxation.
4Reliability
If porosity of bonding material layer is increased to reduce Young's modulus, then thermal stress relaxation improves, but bonding strength decreases
Solution Approach 1:
Porosity is controlled within the optimal range of 20-80% to achieve the right balance. Within this range, the bonding material layer's Young's modulus is reduced for stress relaxation while sufficient bonding strength is maintained through the filler network and matrix material.
Solution Approach 2:
The composite structure with distributed fillers and controlled porosity creates a hierarchical architecture where the filler network provides structural support and bonding strength while the porous matrix provides flexibility and stress relaxation capability.
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 effectively lowers thermal expansion and enhances bonding strength, significantly inhibiting cracking and maintaining structural integrity under thermal stress, thus improving the thermal shock resistance of the honeycomb structure.
Implementation Method 1
a bonding material layer having a Young's modulus of 2-18% and an average linear thermal expansion coefficient of 70% or less than that of the honeycomb segments
Implementation Method 2
the bonding material layer having a Young's modulus of 2-18% of that of the honeycomb segment material, whereby an only small thermal stress is generated during actual use
Data Source
Figure 1~2
Figure 3~4
AI summary
There is disclosed a bonded element manufactured from a bonding material composition being capable of contributing to the lowering of thermal expansion of a bonding material layer sufficiently to relax any thermal stress generated in a honeycomb structure and largely inhibiting the cracking of the resultant honeycomb structure as well. In a bonded element in which two or more objects to be bonded are integrated via a bonding material layer, the bonding material layer having a Young's modulus of 20% or less of that of the objects to be bonded and having an average linear thermal expansion coefficient of 70% or less of that of the objects to be bonded, the bonding material layer being prepared from a bonding material composition composed mainly of fillers and a matrix in which fillers having an average linear thermal expansion coefficient of 2.0×10-6•K-1 or less are contained.