Transition-Thread Bolt Structure for Fatigue Load Distribution
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Solution Overview
Problem
Conventional bolts experience uneven force distribution and high fatigue fracture rates, particularly at the first few threads, leading to connection failures under dynamic loads, which existing solutions fail to adequately address for industrial equipment subjected to harsh conditions.
Innovation Solution
A bolt design featuring a screw cap, a bolt bar with a positioning bar, a flexible bar, and a threaded portion that includes standard and transition threads with a truncated crest and varying thread height, along with an anti-shearing stand, optimized for uniform force distribution and enhanced shearing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard threads are used in conventional bolts, then the bolt structure is simple and easy to manufacture, but the force distribution is uneven and fatigue fracture occurs easily at the first few threads
Solution Approach 1:
The threaded portion is segmented into two distinct types: standard threads for the majority of the engagement length and transition threads at the beginning. This segmentation allows the first few threads to have modified geometry that redistributes stress, while the remaining threads maintain standard geometry for simplicity and compatibility
Solution Approach 2:
The transition threads are designed with locally modified properties - specifically, the thread height is reduced and the root radius is increased only in the first few threads where stress concentration occurs. This local modification addresses the fatigue problem at critical locations without changing the entire thread structure
2Reliability
If high-strength materials are used to manufacture flexible bolts, then the tensile strength is improved, but the anti-fatigue performance and service life are insufficient under frequently fluctuating loads
Solution Approach 1:
The invention changes the geometric parameters of the threads - specifically reducing thread height and increasing root radius in the transition threads. These parameter changes reduce stress concentration and improve fatigue resistance without requiring changes to material strength or bolt flexibility
3Reliability
If the thread height is reduced in transition threads, then the force distribution becomes more uniform, but the tensile force capacity of individual threads is reduced
Solution Approach 1:
The transition threads with reduced height perform the preliminary function of stress distribution optimization at the beginning of the thread engagement. By handling the high-stress region first with specialized geometry, the standard threads can then carry the remaining load uniformly, achieving both uniform distribution and adequate total capacity
Data Source
Figure 1A~2
Figure 3A~4
Figure 5A~6C
AI summary
A bolt and a method for manufacturing the bolt are provided according to the present application. The bolt includes a screw cap and a bolt bar, the bolt bar includes a positioning bar, a flexible bar and a threaded portion, the positioning bar is connected to one end of the screw cap, and the flexible bar is connected to the positioning bar and the threaded portion respectively. Wherein, an anti-shearing stand is formed on the flexible bar. The threaded portion includes standard threads and transition threads, the transition threads are formed between the flexible bar and the standard threads, and a thread height of the transition threads is smaller than a thread height of the standard threads, wherein the thread height (H0) of the standard threads (1241) keeps constant. According to the present application, the force distribution of the threads (especially the force distribution of the first three threads) can be optimized, and the threads can effectively cooperate with the threads of the nut, and moreover the manufacturing process is simple and the cost is low.