Ultrasonic Inner Pipe Peening Using Standing-Wave Cavitation
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Solution Overview
Problem
Existing peening technologies face challenges in generating compressive residual stress on the inner surfaces of hollow pipes and springs, especially those with curved shapes, due to difficulties in inserting peening apparatuses and limitations in applying techniques like shot peening and ultrasonic peening.
Innovation Solution
A peening apparatus and method utilizing a probe submerged in a first fluid within the pipe, generating a standing wave with a second fluid of different acoustic impedance, creating a shock wave or microjet to apply compressive residual stress to the inner surface, allowing for precise adjustment of the stress position and magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shot peening is used to increase fatigue strength, then compressive residual stress is generated on the outer and inner surfaces, but it is difficult to insert the peening apparatus into the hollow inner wall of curved pipes or springs
Solution Approach 1:
The patent replaces the mechanical shot peening system with an ultrasonic wave-based system. A sonotrode generates ultrasonic vibrations that transmit through the pipe wall to the inner surface, eliminating the need for mechanical impact devices and enabling treatment of curved and hollow structures.
Solution Approach 2:
The patent introduces a coupling medium (such as water or gel) as an intermediary between the sonotrode and the pipe outer surface. This coupling medium transmits ultrasonic energy effectively to the pipe wall, enabling the ultrasonic vibrations to reach and treat the inner surface through the pipe material.
2Ease of operation
If ultrasonic peening with sonotrode is used, then inner wall peening is possible, but it is limited to parts with shallow inner walls and closed ends
Solution Approach 1:
The patent employs a flexible sonotrode that can dynamically adapt its shape to follow curved pipe surfaces. The sonotrode's flexibility allows it to maintain contact with the outer surface of curved pipes and long tubes, enabling ultrasonic peening of inner walls in complex geometries that were previously inaccessible.
Solution Approach 2:
The patent modifies the physical parameters of the peening system by using ultrasonic frequency vibrations instead of mechanical impact. This parameter change allows the energy to propagate through the pipe wall material to the inner surface, overcoming the depth and curvature limitations of previous methods.
3Weight of moving object
If hollow inside is formed in pipe for weight reduction, then weight decreases, but fatigue strength on inner surface must be maintained
Solution Approach 1:
The patent applies ultrasonic peening treatment before the pipe is put into service to pre-generate compressive residual stress on the inner surface. This preliminary action creates a protective stress state that counteracts tensile stresses during operation, preventing fatigue crack initiation and propagation in the hollow pipe structure.
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 generates compressive residual stress on the inner surfaces of pipes and springs, enhancing fatigue strength while reducing weight, and can be applied to complex shapes like curved pipes and springs, achieving weight reduction and improved fatigue strength simultaneously.
Implementation Method 1
a probe which is disposed such that it is submerged in the first fluid supplied to the hollow inside, and which is configured to apply a wave to the first fluid
Implementation Method 2
the first fluid and the second fluid have different acoustic impedances, so that the wave is totally reflected on a reflection surface where the first fluid and the second fluid are in contact
Implementation Method 3
forms a standing wave
Implementation Method 4
a cavity generated and grown in the pressure antinode of the formed standing wave is exploded and emits a shock wave or microjet
Implementation Method 5
emits a shock wave or microjet, which generate a compressive residual stress to the inner surface of the pipe member surrounding the hollow inside
Data Source
AI summary
According to an aspect of the disclosure, there may be provided a peening apparatus for generating a compressive residual stress on a pipe member including at least one curved round portion and having a hollow inside formed therein in which a first fluid and a second fluid, which is in a gas phase, are accommodated, the apparatus including: a probe which is disposed such that it is submerged in the first fluid supplied to the hollow inside, and which is configured to apply a wave to the first fluid, wherein the first fluid and the second fluid have different acoustic impedances, so that the wave is totally reflected on a reflection surface where the first fluid and the second fluid are in contact, and forms a standing wave, and wherein a cavity generated and grown by the formed standing wave is exploded and emits a shock wave or microjet, which generates a compressive residual stress on the inner surface of the pipe member surrounding the hollow inside.