Nondestructive Material Evaluation of Gray Cast Iron Using DC Bias Alternating Magnetic Field

The gray cast iron is used in many machine parts such as pulleys, since it has excellent vibration damping, wear resistance, and castability. Material evaluation of this cast iron is important for quality assurance of machine products. This research proposes a method to identify defective products mixed with good products. Currently, test methods such as Brinell hardness and tensile strength tests are commonly used to check the quality of cast irons. However, these methods are not suitable for inspecting all products in terms of time required. Therefore, it is important to establish an electromagnetic nondestructive test that enables non-contact and fast measurement. It has been found that the use of AC magnetic fields in nondestructive testing methods can be used to measure defective gray cast iron. In this paper, we propose an electromagnetic nondestructive testing method that uses a DC-biased sinusoidal magnetic field, which enables measurements with higher sensitivity than those obtained with AC magnetic fields. The effectiveness of the proposed method is demonstrated through electromagnetic field finite element method (FEM) analysis using the play model method and corroborated by verification experiments.