Leaf Spring Eye Portion Shot Peening Reflection Member
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Solution Overview
Problem
The existing shot peening method for the inner surface of the eye portion in leaf springs fails to provide adequate compressive residual stress to the facing portion, leading to durability issues and increased production costs due to material yield deterioration and necessary cutting processes.
Innovation Solution
A production method that forms a gap portion between the leading end and facing portions of the eye portion, allowing for effective shot peening by positioning a reflection member inside the eye portion such that the shots are reflected and projected to the entire surface, including the outside boundary, without colliding with the leading end portion, thereby ensuring comprehensive residual stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shot peening is performed on the inner surface of the eye portion using a reflection member, then compressive residual stress is provided to the surface, but the shots do not reach the leading end portion and the facing portion, resulting in inadequate durability improvement
Solution Approach 1:
The eye portion inner surface is divided into multiple regions (leading end portion, facing portion, and intermediate portions). The reflection member is positioned to create multiple reflection paths, ensuring that shots reach all segmented regions uniformly. This segmentation approach allows targeted shot peening coverage for each critical area.
Solution Approach 2:
The reflection member is positioned asymmetrically within the eye portion rather than at the center. This asymmetric positioning creates optimal reflection angles that direct shots toward the leading end portion and facing portion, which are the critical areas requiring compressive residual stress. The asymmetric arrangement compensates for the geometric asymmetry of the eye portion structure.
2Strength
If the leading end portion is cut to ensure parallelism with the facing portion, then the strength for resisting pullout load is improved, but material yield deteriorates and production cost increases
Solution Approach 1:
The leading end portion is pre-formed during the eye portion forming process to achieve the required parallelism with the facing portion. This preliminary action eliminates the need for subsequent cutting operations, preventing material loss while ensuring the structural strength required for resisting pullout loads is maintained.
Solution Approach 2:
The forming parameters (pressure, temperature, tool geometry) are optimized during the eye portion forming process to achieve the desired geometric precision of the leading end portion. By controlling these parameters, the parallelism between the leading end portion and facing portion is ensured without requiring material removal, thus maintaining material yield.
3Productivity
If the eye portion is formed with high stress and weight reduction, then the leaf spring performance is improved, but the generated stress at the eye portion increases, requiring more extensive shot peening
Solution Approach 1:
The shot peening process applies compressive residual stress locally to critical areas of the eye portion (leading end portion and facing portion) where stress concentration occurs during high-load operations. This local quality enhancement targets specific regions requiring improved durability without adding overall weight, maintaining the weight reduction efficiency while enhancing local strength.
Solution Approach 2:
Compressive residual stress is introduced into the eye portion surface through shot peening before the leaf spring undergoes high-stress operations. This beforehand cushioning creates a protective compressive stress field that counteracts the tensile stresses generated during service, preventing crack initiation and propagation in the high-stress regions of the lightweight eye portion.
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 enhances the durability of the leaf spring by ensuring residual stress is evenly applied to the entire surface, reduces production costs by eliminating unnecessary cutting, and improves productivity by maintaining the integrity of the material during the eye portion formation.
Implementation Method 1
shots are injected from an impeller 25 of a shot peening apparatus to a surface (a surface at which the eye portions 3 are formed) of the leaf portion 2 of the leaf spring 10, and the surface of the leaf portion 2 is subjected to shot peening
Implementation Method 2
the reflection member 32 is disposed inside the eye portion 3, the shots 33 are injected from the nozzle 31 to the reflection member 32, and the shots 33, which are reflected by the reflection surface 32A of the reflection member 32, are projected to the inner surface of the eye portion 3
Implementation Method 3
one end portion of the steel 1 is abutted and pressed by a bending member 13 from one end of a curved portion of the dice 11 to the other end thereof. Thus, the one end portion of the steel 1 is bent, and a curved portion 1 A is formed
Implementation Method 4
while an upper surface of the one end portion side of the steel 1 is pressed by a pressing member 21, the curved portion 1A of the steel 1 is pressed and is wound toward the inside of the curved portion 1A by using a dice 22. Thus, as shown in Fig. 1C, an eye portion 3 is formed
Implementation Method 5
the steel 1 is subjected to heating processing (quenching and tempering), so that a leaf spring 10 is obtained
Data Source
Figure 1A~2
Figure 3~4
Figure 5~6
AI summary
A production method for a leaf spring, which can improve the durability of the eye portion and the productivity and which can reduce the production cost, is provided. In forming of a gap portion 115, a leading end portion 113 of an eye portion 112 faces a facing portion 114 such that each straight line L1 and L2 does not cross the leading end portion 113 of the eye portion 112, the straight line L1 connecting an intersection point T1 and a center point S1 of a reflection surface of a reflection member, the straight line L2 connecting an intersection point T1 and a center point S2 of a reflection surface of a reflection member, the intersection point T1 being between a perpendicular line H1 and a surface of the facing portion 114, the perpendicular line H1 extending from a leaf portion 111 side end point 113A of the leading end portion 113 of the eye portion 112 to the facing portion 114. Thus, shots, which are reflected by the reflection surface of the reflection member in the shot peening to the eye portion 112 inner surface, are projected to the entire surface of the facing portion 114 at the gap portion 115. In forming of the eye portion 112, cutting of a leading end portion thereof is unnecessary.