Threaded High-Pressure Gas Container for Fatigue Fracture Prevention
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Solution Overview
Problem
High pressure gas containers face issues with fatigue fracture at the thread portion due to high stress concentration, especially in screw-type lid structures, and require effective stress alleviation to prevent deformation and ensure durability.
Innovation Solution
Applying residual compressive stress to the vicinity of the thread bottom in the high pressure gas container by controlled internal pressure during production, ensuring the maximum value of residual compressive stress is within the material's tensile and yield stress limits to offset tensile stress and prevent fatigue fracture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a screw-type lid structure is used to reduce container size and cost, then device complexity is reduced, but stress concentration at the thread portion increases causing fatigue fracture
Solution Approach 1:
The patent applies preliminary action by introducing residual compressive stress to the thread portion before the container is put into service. This is achieved through controlled plastic deformation during manufacturing, where the thread portion is subjected to excess pressurization that creates permanent compressive stress. This preliminary stress state counteracts the tensile stress that will occur during normal operation, preventing fatigue fracture and improving reliability while maintaining the simple screw-type lid structure
Solution Approach 2:
The patent changes the stress state parameter of the thread portion by transforming it from a purely tensile stress condition to a combined state with residual compressive stress. Through controlled plastic deformation during manufacturing, the material's stress-strain relationship is altered, creating a favorable residual stress distribution that reduces the net tensile stress during operation, thereby preventing fatigue failure
2Reliability
If high internal pressure is applied to create residual compressive stress, then fatigue resistance is improved, but the risk of exceeding material strength limits increases
Solution Approach 1:
The patent applies partial or excessive action by subjecting the thread portion to excess pressurization that temporarily exceeds the material's yield strength, creating controlled plastic deformation. This excessive action is localized to the thread portion through careful design of the pressing mechanism, ensuring that only the intended area undergoes plastic deformation while the rest of the container remains within elastic limits. The result is residual compressive stress that improves fatigue resistance without compromising overall structural integrity
Solution Approach 2:
The patent applies local quality by creating residual compressive stress specifically in the thread portion where fatigue fracture is most likely to occur, rather than uniformly throughout the entire container. The pressing mechanism is designed to concentrate the plastic deformation and resulting residual stress in the critical thread area, providing targeted fatigue protection where it is most needed while maintaining the overall strength and design of the container
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 alleviates stress on the thread portion, preventing fatigue fracture and allowing the container to withstand higher pressures and larger cross sections without deformation.
Implementation Method 1
a maximum value of residual compressive stress at a position of 0.4 mm in a depth direction from a plurality of thread bottoms of the female thread portion and the male thread portion is 100 MPa or more, less than or equal to tensile strength of a material of the metallic cylinder, and less than or equal to tensile strength of a material of the lid
Data Source
AI summary
To alleviate stress exerted on a thread portion of a high pressure gas container including a metallic container to prevent fatigue fracture, there is provided a high pressure gas container comprising a metallic container, wherein the metallic container includes: a metallic cylinder; a female thread portion on an inner peripheral surface of the metallic cylinder at at least one end; and a lid having, on an outer peripheral surface, a male thread portion configured to screw into the female thread portion, and a maximum value of residual compressive stress at a position of 0.4 mm in a depth direction from a plurality of thread bottoms of the female thread portion and the male thread portion is 100 MPa or more, less than or equal to tensile strength of a material of the metallic cylinder, and less than or equal to tensile strength of a material of the lid.