Tubular Specimen Testing via Hydraulic Pressure
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Solution Overview
Problem
Conventional all-pipe tensile testing devices face challenges in testing large pipes due to the need for high load capacity, limiting tests to small pipes, and often rely on coupon tests that do not accurately represent the entire pipe's properties, leading to mischaracterization of load capacity.
Innovation Solution
A material testing technique using fluid pressure to perform tensile tests on entire pipes, allowing for the determination of load capacity and tensile properties independently of pipe size, using a pressure-stable housing with a fluid pressure chamber and a sample carrier to apply pressure and measure parameters such as pressure and displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional whole-pipe tensile testing devices are used, then tensile tests can be performed on small pipes, but the equipment requires high load-bearing capacity and cannot test large pipes
Solution Approach 1:
The patent applies hydraulic pressure to inflate the tubular specimen during tensile testing. By introducing liquid into the specimen under pressure, the test can be conducted using lower axial tensile stresses while achieving equivalent load-bearing characteristics. This hydraulic approach replaces the need for high load-capacity mechanical equipment, enabling testing of large pipes that would otherwise require prohibitively expensive testing infrastructure.
2Ease of manufacture
If coupon tests are used for large pipes, then testing can be performed with lower equipment requirements, but the pipe properties are mischaracterized as coupons do not represent the entire pipe
Solution Approach 1:
The patent creates a testing method that works for tubular specimens of any size by using hydraulic pressure combined with axial tensile loading. The method is universal across different pipe dimensions and materials, eliminating the need to switch between coupon testing for large pipes and whole-pipe testing for small pipes. The hydraulic system adapts to various specimen sizes while maintaining accurate measurement of tensile properties.
3Measurement precision
If conventional mechanical tensile testing is used for whole pipes, then tensile properties can be measured, but the equipment complexity and cost increase significantly for large pipes
Solution Approach 1:
The patent introduces liquid under hydraulic pressure as an intermediary medium to apply distributed internal pressure to the tubular specimen during tensile testing. This intermediary hydraulic system replaces the need for complex high-capacity mechanical loading equipment. The liquid pressure acts as a mediator that uniformly distributes stress across the specimen wall, simplifying the overall testing apparatus while maintaining measurement accuracy.
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
Enables accurate and simple tensile testing of entire pipes with lower axial tensile stresses, achieving equivalent load-bearing characteristics at proportionally lower tensile forces, and is applicable to pipes of various sizes, including those above 250 mm, using common pressure values like 50-100 bar.
Implementation Method 1
The tubular specimen is expanded as further pressurized liquid is introduced into the hollow space and the annular volume
Implementation Method 2
A pressure-resistant housing is provided which has or forms a housing passage... A fluid pressure chamber is separated within a portion of the housing passage... The liquid in the fluid pressure chamber is pressurized
Implementation Method 3
The wall of the tubular specimen is subjected to an overpressure on the outer radial wall and an overpressure on the inner radial wall. This creates a compressive stress in the radial direction.
Implementation Method 4
The force acting on the cross-section of the first and second partitions... causes a displacement and in particular an elongation of the tubular specimen. This enables a tensile test to be carried out on the tubular specimen.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a material testing technique involving a material testing method, a test piece carrier, and a material testing device. The material testing technique is used to test the load-bearing capacity of a tubular test piece (200). A pressure-stable housing (110) with a housing passage (E) is provided, and a tubular test piece (200) is introduced into the housing passage (E). A fluid pressure chamber (F) is separated within a part of the housing passage (E), in particular by using a test piece carrier (K, K '), wherein the fluid pressure chamber (F) comprises a cavity (F1) in the tubular test piece (200) and an annular volume (F2) between the radial outer surface of the test piece (200) and the housing passage (E). Two end sections of the test piece (200) are secured on the fluid pressure chamber (F) separations (H1, H2), which lie opposite each other in the axial direction (A, B) of the test piece (200), in particular on one test piece carrier or on a respective test piece carrier (K, K'). A liquid (L) is introduced into the fluid pressure chamber (F) such that both the cavity (F1) as well as the annular volume (F2) are filled with liquid (L). A positive pressure (P+) is applied to the liquid (L) in the fluid pressure chamber (F), and the tubular test piece (200) is expanded in the axial direction (A, B) while further introducing liquid under positive pressure (P+) into the cavity (F1) and the annular volume (F2). The volume of the fluid pressure chamber (F) expands, and at least one separation (H1, H2) of the fluid pressure chamber (F), in particular at least one test piece carrier (K, K'), is moved in the axial direction (A, B), thereby entraining the end section of the test piece (200) secured to the separation. At least one parameter is measured or monitored in order to evaluate a load-bearing property of the test piece (200) while the pressure is being applied.