Tensile Test Coupon Template for Plastic Pipe Joints
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Solution Overview
Problem
Current tensile test methods for heat-fused plastic pipe joints are not suitable for field use, as they require expensive and cumbersome equipment, are dependent on uncontrolled variables, and consume excessive material, making them costly and uncertain in determining joint quality.
Innovation Solution
A method and template for producing a tensile test coupon by drilling an array of holes and making straight-line cuts in a plastic pipe, using a template with symmetrical hole patterns and additional holes for precise tensile force application, allowing for efficient and precise extraction of coupons that fail at the joint, reducing material consumption and enabling field evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bend back test is used for field evaluation, then field testing capability is provided, but material cost becomes prohibitive and test reliability is reduced due to uncontrolled variables
Solution Approach 1:
The invention extracts a specific segment or coupon from the pipe joint rather than testing the entire assembled structure. The coupon is a isolated test specimen that contains the fusion joint section, allowing targeted testing of the joint quality without requiring long strap sections of pipe material, thereby reducing material consumption while maintaining field testing capability
Solution Approach 2:
The invention changes the test parameters by using a standardized coupon geometry with controlled dimensions and a specified fusion joint length (e.g., 25mm). This standardization controls the test variables that were previously uncontrolled in the bend back test, improving reliability while using less material
2Ease of operation
If the bend back test is used, then field evaluation is enabled, but test precision is reduced due to uncontrolled bend radius and tooling variables
Solution Approach 1:
The coupon is prepared in advance with precise dimensions, hole patterns, and fusion joint length before testing. The fusion joint is created with controlled parameters during coupon fabrication, ensuring that the test specimen has known and controlled properties that will yield reliable and repeatable test results
Solution Approach 2:
The invention controls critical test parameters including coupon length, width, fusion joint length, and hole positions. By standardizing these parameters, the test eliminates the uncontrolled variables (bend radius, strap length) that plagued the bend back test, thereby improving measurement precision and reliability
3Measurement precision
If laboratory tensile test methods are used, then test precision is improved, but device complexity and portability are reduced making field use impossible
Solution Approach 1:
The invention extracts the essential testing function from complex laboratory equipment by using a simple handheld tensile tester that pulls on the coupon. The complex sample preparation and testing apparatus of laboratory methods is replaced with a portable device that applies tensile force directly to the extracted coupon, maintaining test precision while enabling field use
Solution Approach 2:
The coupon serves as a simplified copy or representative sample of the actual pipe joint that can be tested with simple equipment. Instead of requiring complex laboratory apparatus to test the full-scale joint, the coupon replicates the joint's critical features in a miniaturized form that can be tested with portable equipment, thereby transferring laboratory-level precision to the field
4Length of moving object
If longer straps are used for larger pipe diameters, then adequate test length is achieved, but material cost becomes prohibitive
Solution Approach 1:
The invention segments the pipe joint into a smaller testable coupon that contains only the essential fusion joint section and minimal additional material. This segmented approach provides adequate test length to evaluate joint quality without requiring long strap sections proportional to the pipe diameter, thereby reducing material cost for testing larger diameter pipes
Data Source
AI summary
A method and template enable the testing of fusion joints of plastic pipes to be conducted by a single operator in the field at the welding site by the efficient and precise extraction from the joints to be tested of a number of high quality tensile coupons. The coupons are tested to failure in a field-suitable, well controlled, self contained, tensile testing apparatus. A narrowing bow-tie-like pattern of the coupon ensures that the failure of the coupon in the tensile test will occur at the narrowest section of the coupon. The template can be visually aligned with the joint to ensure that it is the joint that will be tested.