Friction Coatings for Bolted Joints With Reduced Clamp Load Loss

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Solution Overview

Problem

Bolted joints in machines experience failures due to reduced friction between compressed interfaces, leading to slippage and clamp load loss, which can cause equipment damage and increased maintenance costs, as existing solutions like friction members may fail or introduce additional parts that increase costs and complexity.

Innovation Solution

Applying friction coatings with interstitial spaces to the surfaces of components in bolted joints, using materials like tungsten/carbide alloys or aluminum oxide particles, which are deposited using high-velocity processes to create elevated surfaces that increase friction and resist deformation, thereby maintaining contact and reducing slippage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a friction member is inserted between mating surfaces to reduce friction loss, then the friction between compressed interfaces is maintained, but additional parts are introduced which increase costs and complexity

Engineering Contradiction:

Improvefriction maintenanceVSAvoidnumber of parts

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The friction-enhancing function is merged directly into the mating surfaces through coating applications. Instead of using a separate friction member, the coatings are applied to the surfaces themselves, combining the structural component with the friction management function. This eliminates the need for additional friction members while maintaining the desired friction characteristics.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The friction-enhancing material is extracted from a separate component form and applied directly to the mating surfaces as a coating. This removes the need for a distinct friction member component while preserving the friction management function. The coating material is taken out from being a separate part and integrated into the surface treatment of existing components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If a friction member is used to maintain friction between interfaces, then slippage is reduced, but damage to the friction member can introduce pieces into equipment causing additional failures

Engineering Contradiction:

Improveslippage preventionVSAvoiddebris introduction

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The friction-enhancing function is merged with the mating surfaces themselves through coating applications. By integrating the friction management function directly into the surface treatment of existing components, the patent eliminates separate friction members that could potentially damage and shed debris. The coating becomes an integral part of the surface, preventing the separation and fragmentation issues associated with discrete friction members.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If friction coatings are applied to increase friction, then clamp load loss is reduced, but the coating materials must withstand high operating conditions without failing

Engineering Contradiction:

Improveclamp load maintenanceVSAvoidcoating durability

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent employs composite coating materials that combine multiple properties to address both friction enhancement and durability requirements. These composite coatings are designed to withstand high operating conditions including temperature, pressure, and mechanical stress while maintaining their friction-enhancing characteristics. The composite nature of the materials allows them to provide both the desired friction increase and the necessary structural integrity under operating conditions.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent explores different coating material compositions and properties to optimize performance under specific operating conditions. By changing parameters such as material composition, coating thickness, and application methods, the coatings are tailored to withstand the specific thermal, mechanical, and chemical environments while maintaining friction enhancement. This parameter optimization ensures the coatings survive operating conditions without failing.

Inventive Principle:

Principle #35Parameter changes

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 friction coatings effectively increase the coefficient of friction and reduce clamp load loss, enhancing the stability of bolted joints by embedding particles into the surfaces, thus requiring higher shear loads to slip, thereby reducing equipment damage and maintenance costs.

Implementation Method 1

Methodology Applied

Scientific EffectHigh-velocity deposition: Deposition (physical)

Implementation Method 2

Methodology Applied

Scientific EffectEmbedding:

Data Source

PatentUS20240344542A1Surface coatings for decreasing clamp load loss

Publication Date: 2024.10.17 CATERPILLAR INC

AI summary

A machine, such as a hauler at a mining site, includes one or more bolted (clamped) joints. Friction coatings are applied to surfaces of two or more materials being clamped to reduce clamp load loss. The friction coatings include one or more coated surfaces and one or more interstitial spaces between the coated surfaces. Various materials may be used as the friction coating including, but not limited to, a tungsten/carbide or stellite/carbide alloy, iron base alloys such as POLYMET alloys, including PMET 290 (an alloy of iron, chromium, boron, manganese, silicone, and nickel), a nickel chromium alloy, e.g., Ni-20Cr, aluminum oxide (Al2O3) particles, and various combinations of these and other suitable materials.