Threaded Hole Densification for Fatigue-Resistant Cut Threads

Solution Overview

Problem

Conventional methods for manufacturing threaded holes are deficient in terms of fatigue resistance, load retention strength, and manufacturing efficiency, particularly in high-volume production processes.

Innovation Solution

A method and system that involves cutting threading in a workpiece and independently densifying the region around the hole to reduce material porosity, which can include radially expanding the hole before threading, using a hybrid tap with both cutting and forming capabilities, or burnishing the threads to enhance the quality of the threaded hole.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional threading methods are used, then manufacturing simplicity is maintained, but fatigue resistance and load retention strength are insufficient

Engineering Contradiction:

Improvefatigue resistanceVSAvoidmanufacturing process complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The hole is radially expanded before threading is performed. This preliminary expansion densifies the material in the hole region, creating a more favorable stress state that improves fatigue resistance and load retention strength of the subsequent threads.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The material density and stress state parameters are changed by radially expanding the hole before threading. This parameter change transforms the material structure to achieve superior mechanical properties in the threaded region.

Inventive Principle:

Principle #35Parameter changes

2Strength

If conventional threading methods are used, then manufacturing speed is maintained, but load retention strength is insufficient

Engineering Contradiction:

Improveload retention strengthVSAvoidmanufacturing speed

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The hole is radially expanded before threading is performed. This preliminary expansion densifies the material in the hole region, creating a more favorable stress state that improves fatigue resistance and load retention strength of the subsequent threads.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The radial expansion and threading operations are combined into a single integrated process sequence. The expansion tool simultaneously prepares the hole and initiates thread formation, improving load retention strength without significantly impacting manufacturing speed.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If material porosity is not reduced, then manufacturing simplicity is maintained, but fatigue resistance deteriorates

Engineering Contradiction:

Improvefatigue resistanceVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The hole is radially expanded before threading is performed. This preliminary expansion densifies the material in the hole region, creating a more favorable stress state that improves fatigue resistance and load retention strength of the subsequent threads.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The material density and stress state parameters are changed by radially expanding the hole before threading. This parameter change transforms the material structure to achieve superior mechanical properties in the threaded region.

Inventive Principle:

Principle #35Parameter changes

4Productivity

If multiple separate operations are used for threading and densifying, then each operation can be optimized, but manufacturing efficiency decreases

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidthread quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The radial expansion and threading operations are combined into a single integrated process sequence. The expansion tool simultaneously prepares the hole and initiates thread formation, improving load retention strength without significantly impacting manufacturing speed.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The expansion tool is designed to perform multiple functions: radial expansion of the hole, densification of the material, and initiation of thread formation. This multi-functionality improves manufacturing efficiency while maintaining thread quality through controlled material flow.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach results in threaded holes with improved fatigue resistance, high load retention strength, and increased manufacturing efficiency, reducing costs and improving the overall quality of the threaded attachments.

Implementation Method 1

radially expanding the hole includes radially expanding the hole via cold working

Methodology Applied

Scientific EffectCold working: Cold-forming

Implementation Method 2

cutting the threading includes providing a plurality of cut threads at a minor diameter

Methodology Applied

Scientific EffectMaterial removal through cutting:

Implementation Method 3

rolling the plurality of cut threads includes rolling the plurality of cut threads with the forming portion

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 4

densifying the region includes burnishing the plurality of cut threads

Methodology Applied

Scientific EffectBurnishing:

Data Source

PatentUS11577331B2Methods of manufacturing part with hole having cut threads

Publication Date: 2023.02.14 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method of manufacturing a threaded hole in a workpiece includes providing the workpiece having a region with a hole. The method also includes cutting a threading for the hole. Furthermore, the method includes, independent of cutting the threading, densifying the region proximate the hole to reduce material porosity in the region.