Creep-Resistant Direct Tension Indicating Washer
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Solution Overview
Problem
Conventional direct tension indicating washers made from steel struggle to indicate proper bolt tension at lower loads, and softer materials like thermoplastics face long-term compressive creep issues, making them unsuitable for structural applications.
Innovation Solution
A direct tension indicating washer is constructed using a softer material like plastics or thermoplastics with internal metal inserts of higher hardness to prevent deformation and creep, allowing indication of lower bolt tensions while maintaining bolt tension integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If softer materials like thermoplastics are used to indicate lower bolt tensions, then the indication capability at lower loads is improved, but long-term compressive creep increases making the material unsuitable for structural applications
Solution Approach 1:
The washer is constructed as a composite structure combining a softer plastic body (providing indication capability at lower loads) with embedded harder metal inserts (providing creep resistance). This composite approach allows the washer to simultaneously achieve both low-load indication precision and long-term structural reliability under compressive loads.
2Reliability
If steel material is used to ensure long-term creep resistance, then reliability is improved, but the ability to indicate proper bolt tension at lower loads deteriorates
Solution Approach 1:
Different regions of the washer are assigned different material properties: the body is made of softer plastic for indication functionality, while strategic locations contain harder metal inserts for structural support. This local differentiation allows each region to optimize its function without compromising the other.
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 solution effectively indicates proper bolt tension at lower loads and prevents long-term creep, ensuring consistent bolt tension and potential electrical conductivity, while also providing a sealing effect against corrosion.
Implementation Method 1
such materials have long term compressive creep concerns that would exclude their suitability
Implementation Method 2
The indentation 16 is filled with an indicating material 64... the amount of plastic deformation required to provide the appropriate user feedback
Data Source
AI summary
A direct tension indicating washer includes a body having a first surface having a protuberance formed thereon; the body having a second surface having an indentation formed opposite the protuberance; and an insert positioned internal to the body, the body and the insert being made from materials of different hardness.