Bolted Joint Load Distribution via Elastic Modulus Gradient

Solution Overview

Problem

Conventional bolted joint structures face challenges in evenly distributing load among bolts, particularly when using composite materials, which can compromise strength and require complex machining, making it difficult to meet design standards and manufacturing efficiency.

Innovation Solution

A bolted joint structure with a load transfer member having a lower elastic modulus on the outer end side, allowing for even load distribution among bolts without altering the thickness or configuration of the joinable plates, using materials with varying elastic moduli or reinforcing plates/sleeves to reduce shared load on outer end bolts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the thickness of plates is reduced at outer parts to decrease elastic modulus, then load distribution among bolts is improved, but plate strength is compromised and manufacturing complexity increases

Engineering Contradiction:

Improveload distribution uniformityVSAvoidplate strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies local quality by providing the elastic modulus lowering treatment (such as holes, grooves, or material removal) only at specific locations near the bolt holes, particularly at the outer end side of the joint part. This localized modification reduces the elastic modulus only where needed to improve load distribution, while maintaining the original plate thickness and strength in other critical areas. The treatment is applied selectively rather than uniformly across the entire plate.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs asymmetry by concentrating the elastic modulus lowering treatment primarily at the outer end side of the joint part rather than distributing it symmetrically. This asymmetric approach addresses the specific load distribution issue at the outer bolts more effectively, creating an intentional imbalance in the structure to achieve better overall load sharing among all bolts.

Inventive Principle:

Principle #4Asymmetry

2Manufacturing precision

If the thickness of plates is reduced at outer parts to decrease elastic modulus, then load distribution among bolts is improved, but machining time and complexity increase

Engineering Contradiction:

Improveload distribution uniformityVSAvoidmachining efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies local quality by providing the elastic modulus lowering treatment (such as holes, grooves, or material removal) only at specific locations near the bolt holes, particularly at the outer end side of the joint part. This localized modification reduces the elastic modulus only where needed to improve load distribution, while maintaining the original plate thickness and strength in other critical areas. The treatment is applied selectively rather than uniformly across the entire plate.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by implementing the elastic modulus lowering treatment only in specific regions (near bolt holes and at outer end side) rather than across the entire plate. This partial treatment is sufficient to achieve the desired load distribution improvement without the excessive machining time and cost that would result from treating the whole plate.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If the width of joinable plate is reduced toward the end to decrease elastic modulus, then load distribution among bolts is improved, but design standards such as required strength are not satisfied

Engineering Contradiction:

Improveload distribution uniformityVSAvoidjoint part strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies local quality by providing the elastic modulus lowering treatment (such as holes, grooves, or material removal) only at specific locations near the bolt holes, particularly at the outer end side of the joint part. This localized modification reduces the elastic modulus only where needed to improve load distribution, while maintaining the original plate thickness and strength in other critical areas. The treatment is applied selectively rather than uniformly across the entire plate.

Inventive Principle:

Principle #3Local quality

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 approach ensures even load distribution among bolts, increasing transferable load proportional to the number of bolts, simplifies manufacturing, and maintains design standards without additional processing, making it suitable for lightweight and high-strength applications like aircraft components.

Implementation Method 1

the joint parts or a load transfer member for transferring the load applied to the joint parts to the joining bolts is made of a material having an elastic modulus lower at the joint part disposed on an outer end side of the joinable members so that shared load is applied evenly to each of the joining bolts

Methodology Applied

Scientific EffectElastic modulus variation: Elasticity

Data Source

PatentUS9157462B2Bolted joint structure

Publication Date: 2015.10.13 MITSUBISHI HEAVY IND LTD

AI summary

Joint parts of joinable plates to be joined to each other are joined by a plurality of joining bolts. The joining bolts are arranged in a direction of a tensile load F. The joint parts of the plate members have four sections T1 to T4 that vary in elastic modulus. The elastic modulus (E1 to E4) of these sections T1 to T4 have a relationship of E1(T1)>E2(T2)>E3(T3)>E4(T4).