Reciprocating Wear Test Fixture Preload for Backlash-Free Force Sensing

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Solution Overview

Problem

Conventional reciprocating wear test systems suffer from backlash due to assembly tolerance or preload issues, leading to inaccurate friction force measurements, especially when the sample holder changes movement direction.

Innovation Solution

The reciprocating friction and wear test apparatus incorporates a frame unit with an abrader unit, featuring an abrader fixture, sensor members, and adjustment members that allow for preload cancellation and accurate force transmission through threaded connections, using piezoelectric sensors to measure friction and normal forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the sample holder and force sensor are fixed relative to each other, then the structural stability is improved, but assembly tolerance and insufficient preload cause backlash resulting in reduced measurement accuracy

Engineering Contradiction:

Improvestructural stabilityVSAvoidfriction force measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The adjustment member applies preliminary action by preloading the force sensor against the sample holder before testing begins. This preliminary preload eliminates backlash and ensures tight coupling between components, preventing relative movement during subsequent friction force measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The adjustment member changes the preload parameter of the force sensor assembly. By increasing the contact force between the force sensor and sample holder through the adjustment member, the system transitions from a loose assembly with backlash to a tightly coupled assembly with improved measurement accuracy.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the sample holder changes movement direction during testing, then the reciprocating wear test function is achieved, but backlash becomes more pronounced reducing measurement accuracy

Engineering Contradiction:

Improvereciprocating motion capabilityVSAvoidfriction force measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The adjustment member applies preliminary action by preloading the force sensor against the sample holder before reciprocating motion begins. This preliminary preload eliminates backlash and ensures tight coupling between components, preventing relative movement during subsequent friction force measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The adjustment member creates preliminary anti-action by applying a preloading force that counteracts the tendency for backlash to occur during direction changes. This pre-applied compressive force ensures that the force sensor remains in firm contact with the sample holder even when reciprocating motion causes direction reversals.

Inventive Principle:

Principle #9Preliminary anti-action

3Measurement precision

If assembly tolerance is reduced to eliminate backlash, then measurement accuracy is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvefriction force measurement accuracyVSAvoidassembly complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The adjustment member serves as an intermediary element between the force sensor and the sample holder. Rather than requiring tight tolerances on the force sensor mounting, the adjustment member provides a mechanism to achieve the necessary preload, simplifying the overall assembly requirements while maintaining measurement accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

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 apparatus achieves enhanced accuracy in friction and wear testing by minimizing backlash and ensuring precise force measurement, thereby improving the reliability of test results.

Implementation Method 1

using piezoelectric sensors to measure friction and normal forces

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS12467840B2Reciprocating friction and wear test apparatus

Publication Date: 2025.11.11 NATIONAL TAIWAN OCEAN UNIVERSITY

AI summary

A reciprocating friction and wear test apparatus includes a frame unit and an abrader unit. The frame unit includes a frame that has a bottom wall formed with an opening and two side walls extending upwardly from the bottom wall. The abrader unit includes an abrader fixture, an abrader, two first sensor members, and two adjustment members. The abrader fixture extends through the opening and is pivotable relative to the bottom wall. The abrader is affixed to the abrader fixture. The two first sensor members are respectively mounted to the side walls. The two adjustment members are respectively connected to the first sensor members, extend respectively through the first sensor members, extend respectively through the side walls, and are movable toward the abrader fixture to tightly abut against the abrader fixture.