Irregular Surface Compression via Virtual Control Path

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Solution Overview

Problem

Existing methods for inducing compressive residual stress on components with irregular surfaces are inefficient and unreliable, particularly for automated processing, as they struggle to achieve precise control over depth and magnitude of compression, often leading to incomplete coverage and excessive cold working, which can soften hardened steels and cause unacceptable changes in critical dimensions.

Innovation Solution

A method and apparatus utilizing a CNC-controlled robot or machine tool with a precision positioning system and a flexible arm assembly to guide a tool head with a controlled compression element, allowing it to follow a virtual control surface below the actual surface, ensuring consistent contact and minimizing random impacts, thus achieving controlled compression with minimal cold working.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional peening methods (shot peening, ultrasonic peening, etc.) are used on irregular surfaces, then compressive residual stress can be introduced, but the positioning accuracy deteriorates making automated processing difficult

Engineering Contradiction:

Improvecompressive residual stressVSAvoidpositioning accuracy

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the fundamental parameter of how compression is applied - from random/repeated impacts (shot peening, ultrasonic peening) to a single controlled impact per location. The tool head delivers compression in one definitive action, eliminating the need for multiple passes and positioning adjustments, thereby maintaining positioning accuracy while achieving the required compressive residual stress on irregular surfaces

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces complex mechanical positioning and control systems required for repeated peening operations with a simpler single-impact mechanism. The force application system is designed to deliver the complete required compression in one action, substituting the need for sophisticated control of multiple mechanical impacts with a more straightforward single-impact delivery system

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If repeated impacts are used to ensure full coverage of irregular surfaces, then compression coverage improves, but excessive cold working occurs causing surface softening

Engineering Contradiction:

Improvecompression coverageVSAvoidsurface hardness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies the principle of partial action by delivering exactly the required amount of compression in a single impact rather than excessive repeated impacts. The single impact is calibrated to provide sufficient compression coverage without over-working the surface, thereby maintaining surface hardness while achieving reliable compression coverage on irregular surfaces

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If automated processing is implemented on irregular surfaces, then productivity increases, but process repeatability deteriorates

Engineering Contradiction:

Improveprocessing efficiencyVSAvoidprocess repeatability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the compression process into discrete single-impact events at each location rather than continuous or repeated peening. This segmentation allows automated systems to precisely control and repeat the exact same single-impact parameters across all locations and multiple workpieces, thereby maintaining process repeatability while achieving high productivity through automation

Inventive Principle:

Principle #1Segmentation

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 enables reliable and efficient induction of compressive residual stress on irregular surfaces, improving fatigue strength and damage tolerance while minimizing surface softening and dimensional changes, achieving deeper and more uniform compression compared to conventional methods.

Implementation Method 1

The introduction of compressive residual stress is achieved in all practical cases by introducing non-uniform cold work, or plastic strain, into the workpiece

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 2

a compression element for impacting the surface of a workpiece

Methodology Applied

Scientific EffectImpact force: Impact Force

Data Source

PatentUS9789582B2Method and compression apparatus for introducing residual compression into a component having a regular or an irregular shaped surface

Publication Date: 2017.10.17 SURFACE TECHNOLOGY HOLDINGS LTD

AI summary

A method and apparatus for improving the fatigue and stress corrosion cracking performance of irregular surfaces, such as welds assemblies of components, using a positioning system, such as a robotic or CNC machine, to position a tool head for inducing compression along and into the surface of a workpiece to automatically follow the surface irregularities. The method and apparatus operates to follow a virtual control surface located below the actual surface of the workpiece thereby allowing the irregular topography surface to be uniformly processed with closed loop process control.