Non-Destructive Testing Device With Three-Coil Magnetic Field Arrangement
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Solution Overview
Problem
Existing methods for non-destructive testing of metallic workpieces using the magnetic powder method require multiple passes or rotations to detect both longitudinal and transverse defects effectively, leading to inefficiencies and incomplete defect detection, especially in areas where magnetic fields are perpendicular to the workpiece.
Innovation Solution
A device with a cross-coil arrangement supplemented by a third coil oriented axially, allowing every surface point of the workpiece to be reached by magnetic field components for comprehensive defect detection, utilizing a combination of three-phase current and direct current to generate a homogeneous magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cross-shaped coil arrangement is used to detect both longitudinal and transverse defects, then defect detection coverage is improved, but the magnetic fields in intersection areas become perpendicular to the workpiece resulting in inadequate defect detection in these areas
Solution Approach 1:
The invention introduces a third coil arranged perpendicular to the plane of the first two cross-shaped coils, adding a spatial dimension to the magnetic field generation. This third coil creates magnetic field components that are parallel to the workpiece surface in intersection areas, complementing the perpendicular fields from the cross-shaped arrangement and enabling reliable defect detection in previously problematic zones.
Solution Approach 2:
The invention combines multiple coil arrangements (cross-shaped coils plus perpendicular third coil) into a composite testing system. This composite configuration generates a combined magnetic field that has both perpendicular and parallel components relative to the workpiece, ensuring comprehensive defect detection across all surface areas including intersection zones.
2Measurement precision
If the workpiece is rotated during inspection to detect defects from all sides, then complete defect detection is achieved, but the inspection process becomes more complex and time-consuming
Solution Approach 1:
Instead of rotating the workpiece mechanically, the invention creates a three-dimensional magnetic field environment using coils arranged in multiple orientations. This allows the magnetic field to interact with defects from all directional perspectives while the workpiece remains stationary, eliminating the need for rotation mechanisms and simplifying the inspection process.
Solution Approach 2:
The invention replaces the mechanical rotation system with an electromagnetic field system. Rather than physically rotating the workpiece to expose different surfaces to the magnetic field, the field itself is configured to envelop the workpiece from all directions, substituting mechanical motion with a stationary multi-directional field configuration.
3Measurement precision
If multiple coils are used to generate magnetic fields in all directions, then comprehensive defect detection is achieved, but the number of current-carrying conductors increases leading to higher heat losses
Solution Approach 1:
The invention employs alternating current to generate alternating magnetic fields from the coil arrangement. This periodic field generation allows for efficient energy utilization and reduces continuous power consumption, mitigating heat losses while maintaining comprehensive defect detection capabilities through the multi-directional field configuration.
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 the detection of both longitudinal and transverse defects in a single pass without rotating the workpiece, improving defect detection coverage and reducing the number of current-carrying conductors and heat losses, suitable for large workpieces like railway wagon frames and turbine shafts.
Implementation Method 1
A magnetic field can be generated either by passing an electric current through a yoke applied to the workpiece or by contactless field generation using current-carrying coils positioned relatively close to the workpiece
Implementation Method 2
The coil thus forms the shape of a saddle coil. As the workpiece passes through the coil and rotates during this process, defects on the surface of the workpiece are essentially completely detected
Implementation Method 3
A magnetic powder is then applied to the surface of the workpiece, and the resulting distribution of the powder is measured. This method can detect cracks in the workpiece that are located on or directly beneath the surface
Implementation Method 4
To improve the visibility of the magnetic powder, it can be mixed with fluorescent substances, causing it to stand out clearly from the background under UV radiation and thus highlighting the cracks
Data Source
Figure 1
AI summary
The invention relates to a device for the non-destructive testing of metallic workpieces (4) for surface defects using a magnetic particle method. In this method, a magnetic powder-containing agent is applied to the surface of the workpiece (4), and the distribution of the magnetic powder at defects in the workpiece is determined when the workpiece is magnetized by means of electrical coils (1, 2). The first and second coils (1, 2), positioned at an angle of 90° to each other in their axial plane, encircle the workpiece in a ring-like manner and induce the magnetization. The axial directions of the coils (1, 2) are each at an angle of 45° to the longitudinal axis of the workpiece (4). According to the invention, a third coil (3, 6) extends with its axial direction perpendicular to the plane of the axes of the first and second coils (1, 2), and the workpiece is guided substantially parallel to the plane of the third coil (3, 6) during the test.