Mastering Electromagnetic NDT Techniques with EMWorks Solutions

Non-destructive Testing (NDT)
By Asma Jlassi | 02/09/2022

Non-Destructive Testing (NDT) Inspection 

NDT refers to an array of inspection methods that allow inspectors to evaluate and collect data about a material, system, or component without permanently altering it. NDT is divided into various methods of non-destructive testing, each based on a particular physical phenomenon such as the Electromagnetic NDT: EM NDT. 

Electromagnetic inspection is a non-destructive testing method that includes magnetic fields and electric currents. It allows measuring a response caused by a defect on a metallic test object. Below are the most common electromagnetic-based NDT methods: 

  • Eddy Current Testing (ECT), 
  • Alternating Current Field Measurement (ACFM), 
  • Eddy Current Pulsed Thermography (ECPT), 
  • Magnetic Flux Leakage for Tube Crack Inspection (MFL). 

EMWorks Solution for EM NDT Applications 

Design Challenges  

CAD design and simulation process solves design challenges posed by NDT devices. It saves time and money, reduces the manufacturing cycle, and provides innovative and efficient solutions. 

The main design challenges posed by EM NDT devices are:  

  • Computation of static and time-varying magnetic fields, 
  • Calculate eddy currents in conductive components, 
  • Optimization of inductor shapes and magnet arrangements to improve crack detection, 
  • Calculate the inductance, resistance, and impedance of the sensor coil, 
  • Predict the voltage and current of the coil sensor, 
  • Test several configurations and design scenarios, 
  • Compute temperature caused by eddy currents and other electromagnetic losses. 

Electromagnetic NDT Inspection Tools 

EMWorks Solution 

EMWorks offers a powerful and comprehensive solution to efficiently design and analyze NDT applications based on electromagnetics. This package includes the following: 

  • 2D and 3D electromagnetic analysis, 
  • Static and time-varying magnetic and electric field calculations, 
  • Eddy currents, skin, and proximity effects, 
  • Circuit parameters calculation,  
  • Sensor voltage and current prediction, 
  • Integrated circuit simulator, 
  • Embedded Multiphysics options, 
  • CAD integration for better and easier geometry handling and manipulation, 
  • Single platform for 2D and 3D simulations, 
  • Parametric analysis, multiconfiguration simulations. 

ECT Method 

Eddy current testing (also known as eddy current inspection) is a method used in non-destructive testing, employing electromagnetic induction to detect surface defects and slightly sub-surface flaws in materials. The main areas where ECT is used include crack and corrosion detection, non-conductive coating thickness measurement, material identification, and heat treatment conditions. This method is efficient for non-magnetic material inspection used in both surface and sub-surface defects; able to identify and quantify cracks under plates; measure the thickness of non-conductive paint and coating; investigate changes in material and microstructure properties.

The main steps of ECT inspection involve: 

  • Eddy current coil generates a primary magnetic field, 
  • The primary magnetic field induces eddy currents in the material, 
  • Eddy currents generate a secondary magnetic field in the opposite direction, 
  • Coil impedance changes, as a result, 
  • Hence, the impedance change is measured, analyzed, and correlated to defect dimensions.

ECT Working Principle [1] 

Case Study1: TEAM Problem 15 [2] 

ECT Team Problem 15 Model 

Current Density Animation with Crack Presence 

Current Density Animation without the Crack Presence 

Impedance Variation with Crack Presence 

Resistance Variation with Crack Presence 

Inductance Variation with Crack Presence 

ACFM Method 

ACFM is an electromagnetic inspection technique that introduces an alternating current in the surface of a component to detect surface defects. The presence of a crack disturbs the electromagnetic field; the variation in the magnetic field is captured and analyzed by a sensor placed above the specimen; the operator is instantly alerted to the presence of defects. This technique is suitable for both magnetic and non-magnetic material inspection.  

The working principle of the ACFM method includes the following steps:  

  • The ACFM sensor, which is composed of one or more coils, creates eddy currents on the tested specimen, 
  • These eddy currents are disturbed in the presence of a crack, which also causes a disturbance in the magnetic field above the surface, 
  • This variation in the magnetic field is captured and analyzed by a sensor that measures the location and size of the crack.

ACFM Principle 

Case Study 2: ACFM Device [3] 

ACFM Probe Model [3]