Laser Shock and Ultrasonic Mandrel Strengthening for Small Holes
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Solution Overview
Problem
Current hole strengthening methods, such as cold extrusion and laser shock, face limitations in effectively enhancing small holes due to issues like mandrel breakage, complex processes, and uneven stress distribution, particularly for holes with diameters less than 3.5 mm, and fail to comprehensively strengthen the hole angle and inner wall.
Innovation Solution
A synergistic method combining laser shock and ultrasonic vibration extrusion, where a mandrel with axial tensile force and radial ultrasonic vibration is used to create a three-dimensional compressive stress distribution within the hole, overcoming the limitations of single technologies by simultaneously performing laser shock strengthening and ultrasonic vibration extrusion on opened holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mandrel direct cold extrusion is used to strengthen holes, then residual compressive stress is introduced on the hole wall surface, but the mandrel breaks due to large friction and severe plastic flow
Solution Approach 1:
A lubricating layer is introduced as an intermediary between the mandrel and the hole wall to reduce friction and prevent direct contact. This lubricating layer allows the mandrel to pass through while still enabling plastic deformation of the hole wall, thus preventing mandrel breakage while maintaining the strengthening effect.
Solution Approach 2:
The patent replaces part of the mechanical direct-contact system with a lubricating mechanism. Instead of relying solely on mechanical friction between mandrel and hole wall, the lubricating layer substitutes for direct mechanical interaction, reducing wear and breakage while preserving the necessary plastic deformation for strengthening.
2Reliability
If slotted bushing is added between hole wall and mandrel to reduce friction, then mandrel breakage is prevented, but the process becomes complicated and processing cost increases substantially
Solution Approach 1:
The patent extracts the lubricating function from the complex slotted bushing system and applies it directly to the mandrel surface. Instead of using a separate bushing component, the lubricating layer is applied directly to the mandrel, simplifying the process while maintaining the benefit of reduced friction and prevented mandrel breakage.
Solution Approach 2:
The mandrel with lubricating layer serves multiple functions: it provides the necessary mechanical pressure for plastic deformation, prevents friction-induced breakage, and simplifies the process by eliminating the need for separate bushing components. This multi-functional approach reduces device complexity while maintaining reliability.
3Strength
If double-sided laser shock strengthening is used to eliminate mid-wall tensile stress, then stress distribution is improved, but the process becomes difficult to realize for complex workpiece shapes and application is limited
Solution Approach 1:
The mandrel acts as an intermediary tool that can be inserted into the hole from one side only. It transmits the extrusion force to the hole wall, creating compressive stress in the middle of the wall without requiring access from both sides. This intermediary approach achieves uniform stress distribution while maintaining ease of operation for complex workpiece shapes.
Solution Approach 2:
Instead of applying laser shock from both sides of the workpiece (which is difficult for complex shapes), the patent inverts the approach by using a mandrel inserted from one side to create the necessary compressive stress. This inverted method achieves the same stress distribution benefit while being accessible for any hole shape.
4Strength
If ordinary mandrel cold extrusion is used for small holes, then hole wall is strengthened, but friction is large causing scratches on hole wall surface and mandrel breakage
Solution Approach 1:
A lubricating layer is introduced as an intermediary between the mandrel and the hole wall to prevent direct contact. This lubricating layer reduces friction during the extrusion process, preventing scratches on the hole wall surface while still allowing sufficient plastic deformation for strengthening. The lubricating layer acts as a protective mediator that preserves surface quality.
Solution Approach 2:
The patent changes the friction parameter by introducing lubrication. By modifying the friction coefficient between mandrel and hole wall through the lubricating layer, the process achieves both adequate plastic deformation for strengthening and reduced friction to prevent surface scratches and mandrel breakage.
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
This method enhances the fatigue resistance and surface quality of the hole, effectively strengthening holes of any size by forming reasonable stress distribution, improving the hole angle and inner wall, and reducing the risk of mandrel breakage, while maintaining a simple process.
Implementation Method 1
the laser beam irradiates the absorbing layer, so that the absorbing layer generates shock wave to strengthen the hole on the upper surface of the metal sheet by laser shock
Implementation Method 2
the piezoelectric ceramic generates ultrasonic vibration, so that the mandrel vibrates in radial direction through ultrasonic vibration extrusion
Implementation Method 3
a mandrel with axial tensile force and radial ultrasonic vibration is used to create a three-dimensional compressive stress distribution within the hole
Data Source
AI summary
A laser shock and supersonic vibration extrusion co-strengthening device and method. The device comprises a laser assembly, a vibration assembly, a hydraulic assembly and a connecting assembly. The method strengthens a hole (7) formed in a metal sheet (5) simultaneously by laser shock strengthening and supersonic vibration extrusion strengthening; a mandrel (1) is in clearance fit with the hole to constrain the hole, so as to avoid distortion of the hole and a hole angle when the laser shock is performed on an outer surface of a workpiece and to improve the strengthening effect of a hole wall; when the laser shock is performed on the outer surface of the metal sheet, supersonic vibration is applied by the mandrel in the hole; and a three-dimensional pressure stress distribution nearby the hole wall at a certain depth is formed under an interaction produced by power ultrasound and laser shock waves having a certain frequency, amplitude and modality, so that an inner surface having higher anti-fatigue performance and being smoother is provided to the hole. Defects of a traditional strengthening process are overcome, and the problem in strengthening the hole separately through the laser shock or supersonic vibration extrusion is solved.