Composite Alloy Screw Thread Structure to Prevent Bolt Loosening
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Solution Overview
Problem
Bolts formed from combined alloys, such as aluminum cladding, face issues with reliability and durability, particularly experiencing loosening during repeated use, despite efforts to reduce weight.
Innovation Solution
A fastening member design featuring a screw thread with a thick and thin portion in the outer peripheral area, where the thick portion is maximized in the circumferential direction and the thin portion is minimized, using a first alloy material, while the root of the screw thread is formed from a second alloy material with higher tensile strength, optimizing material distribution for improved engagement and load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a bolt is formed of a material combined of two types of alloys, such as a cladding material including aluminum, then weight reduction is achieved, but reliability and durability deteriorate due to loosening occurring during repeated use
Solution Approach 1:
The invention applies different material properties to different regions of the fastening member. The outer peripheral portion (including screw thread crest) uses a first alloy material optimized for weight reduction, while the inner peripheral portion (including screw thread root) uses a second alloy material with higher tensile strength optimized for reliability. This local differentiation allows the structure to simultaneously achieve weight reduction and improved reliability by placing each material where it is most effective.
Solution Approach 2:
The invention employs a composite structure combining two different alloy materials within a single fastening member. The cladding layer (first alloy) and base material (second alloy) work together synergistically - the lighter outer layer reduces overall weight while the stronger inner layer provides the necessary mechanical strength and resistance to loosening, achieving both weight reduction and reliability improvement through material composition.
2Weight of moving object
If the outer peripheral portion is made thinner to reduce weight, then weight reduction is achieved, but the screw thread engagement strength deteriorates
Solution Approach 1:
The invention creates a thickness gradient in the outer peripheral portion, with the thickest section located at the screw thread root (inner peripheral side) and progressively thinner sections toward the outer periphery. This local variation in thickness ensures that the critical screw thread engagement area maintains sufficient strength while other portions of the fastening member are optimized for weight reduction.
Solution Approach 2:
The invention systematically varies the thickness parameter of the outer peripheral portion across different radial positions. By controlling the thickness distribution - making it thicker where screw thread engagement is critical and thinner where weight reduction is prioritized - the design optimizes the balance between weight and engagement strength through parameter optimization.
Data Source
AI summary
A fastening member includes a screw thread formed therein. A portion including a crest portion of the screw thread is formed of a first alloy material and includes: a thick portion where the portion is maximized in thickness in a circumferential direction; and a thin portion where the portion is minimized in thickness in the circumferential direction. A portion including a root of the screw thread is formed of a second alloy material having a tensile strength higher than that of the first alloy material.