Detection of Internal Holes in Additive Manufactured Ti-6Al-4V Part Using Laser Ultrasonic Testing

Shengnan Shen,Hongze Wang,Guoqing Zhang,Changhui Song,Jie Yu,Dongqi Zhang,Hui Li,Yongqiang Yang,Xin Zhou

doi:10.3390/app10010365

Abstract

For a non-contact, non-destructive quality evaluation, laser ultrasonic testing (LUT) has received increasing attention in complex manufacturing processes, such as additive manufacturing (AM). This work assessed the LUT method for the inspection of internal hole defects in additive manufactured Ti-6Al-4V part. A Q-switched pulsed laser was utilized to generate ultrasound waves on the top surface of a Ti-6Al-4V alloy part, and a laser Doppler vibrometer (LDV) was utilized to detect the ultrasound waves. Sub-millimeter (0.8 mm diameter) internal hole defect was successfully detected by using the established LUT system in pulse-echo mode. The method achieved a relatively high resolution, suggesting significant application prospects in the non-destructive evaluation of AM part. The relationship between the diameter of the hole defects and the amplitude of the laser-generated Rayleigh waves was studied. X-ray computed tomography (XCT) was conducted to validate the results obtained from the LUT system.

Highlights

Additive manufacturing (AM) is a type of technology in which an entity part is manufactured by means of a gradual accumulation of materials
In a B-Scan image, the travel time of the ultrasonic waves are plotted on one axis, and the X-coordinates of detection points along the scanning path are plotted on the other axis
The maximum amplitude values obtained from A-Scan signals of all scanning points are extracted to generate a plan view image (C-Scan) of the sample

Summary

Introduction

Additive manufacturing (AM) is a type of technology in which an entity part is manufactured by means of a gradual accumulation of materials. The AM process offers many advantages over conventional machining technology, such as the diversity of materials available and no limitation on the structural complexity of modeling part [1]. Despite these advantages, material discontinuities can be caused due to the complex environment of the AM process. The most common material discontinuities are voids and pores situated in the bulk of the fused material. Such defects seriously affect the mechanical properties of the workpiece, limiting the development and application of the AM process [2]. There is an urgent need for non-destructive quality evaluation technology for the process control of AM

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Conclusion