Autofrettage Apparatus for Prechamber Fatigue Strength
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Solution Overview
Problem
Internal combustion engine prechambers, particularly drilling edges or nozzles, are prone to crack initiation due to harsh pressure and temperature conditions, leading to operational issues and the need for frequent replacement.
Innovation Solution
An autofrettage apparatus comprising two body parts that form a sealed space with a fluid conduit to apply high pressure incompressible fluid, inducing plastic deformation on the inner surface of prechamber elements, thereby increasing fatigue strength and preventing crack initiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If prechamber elements operate under harsh pressure and temperature conditions, then combustion efficiency is improved, but crack initiation and fatigue failure occur more frequently
Solution Approach 1:
The autofrettage process applies preliminary plastic deformation to the prechamber element before actual service use. High pressure fluid causes the inner surface layer to yield plastically while the outer surface remains elastic, creating compressive residual stresses that counteract tensile stresses during operation, thereby preventing crack initiation at drilling edges and nozzles
2Reliability
If autofrettage treatment is applied to increase fatigue strength, then durability is improved, but device complexity increases due to specialized apparatus requirements
Solution Approach 1:
The autofrettage apparatus body is divided into at least two separable body parts that can be assembled to form an enclosed space. This segmentation allows the prechamber element to be inserted and removed easily, and the apparatus to be disassembled for maintenance or reconfiguration, thereby reducing operational complexity while maintaining the fatigue strength benefits
Solution Approach 2:
The apparatus body is designed with a fluid conduit that can be connected to various fluid sources, and the enclosed space can accommodate different prechamber element configurations. This multi-functionality allows a single apparatus design to serve multiple autofrettage applications, reducing the need for specialized equipment for each specific case
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 significantly enhances the durability of prechamber elements by inducing compressive stresses over 250 MPa, preventing crack growth and improving operational reliability.
Implementation Method 1
the inner surface layer is plastically deformed and the outer surface is subjected to elastic deformation. More specifically, the plastic deformation is an irreversible process whereas the elastic deformation is a reversible process
Implementation Method 2
the hydraulic fluid is guided with a very high pressure into a drilling or alike space of a work piece so as to generate material internal stresses in the inner walls of the drilling or alike
Implementation Method 3
the outer surface is subjected to elastic deformation. More specifically, the plastic deformation is an irreversible process whereas the elastic deformation is a reversible process
Data Source
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AI summary
Invention relates to an autofrettage apparatus (10) for and a method of increasing a fatigue strength a prechamber element (50). The apparatus (10) comprises at least two body parts (20, 30) attachable pressure tight- ly together so as to form a body (203) having a substantially enclosed space (22, 32) therein, wherein a form and dimensions of the enclosed space (22, 31) are chosen so that the prechamber element (50) can be arranged firmly and non-movably inside the body (203) when enclosing the prechamber element (50) by attaching the at least two body parts (20, 30) pressure tightly together, and wherein the body (203) is provided with an at least one conduit (35) opening into the space (22,31) arranged connectable with a fluid source (40) such that an incompressible fluid from the fluid source may be arranged to apply pressure against an inner surface (52) of the prechamber element (50) when enclosed by the body (203), for causing plastic deformation and increasing the fatigue strength of the inner surface layer of the prechamber element (50).