###### Abstract  
This study demonstrated the potential of a non-destructive evaluation (NDE) method to assess the elastic properties of materials printed under various parameters. A database was created documenting the relationship between the elastic properties (Young's modulus, shear modulus, and Poisson's ratio) of PLA (polylactic acid) materials and selected printing parameters such as temperature, speed, and layer height. PLA, which is widely used in additive manufacturing, offers convenient testing conditions due to its less demanding control compared to materials like metals. Ultrasonic testing was conducted on specimens printed under different nozzle temperatures, speeds, and layer heights. The results indicated that an increase in the printing temperature corresponded to an increase in material density and elastic properties of the material. In contrast, an increase in layer height led to a decrease in both density and the elastic properties of the material. Variations in the nozzle speed had a negligible effect on density and did not show a notable effect on the elastic moduli. This study demonstrated that ultrasonic testing is effective in measuring the elastic properties of PLA materials and shows the potential of real-time ultrasonic NDE. NDE; elastic properties; material characterization; 3D printing; PLA; ultrasonic testing; UT; FDM +
Footnote †: journal: Applied  
Article  
Application of Ultrasonic Testing for Assessing the Elastic Properties of PLA Manufactured by Fused Deposition Modeling  
[PERSON], [PERSON], [PERSON], [PERSON], B.  
the mechanical properties was shown in [10; 11]. One of the reasons why the final properties of a material may differ from the expected ones is the presence of defects. Defects, such as voids, layer debonding, and surface roughness, can arise from various factors, such as the parameters of the process and their combinations, the properties of the raw material, environmental factors, etc. [12; 13]. Defects could negatively affect the mechanical properties of the part [14; 15]. Finally, the layer-by-layer deposition approach may result in possible anisotropy of the material. Given the broad range of variables affecting the quality of the fabricated part, it is important to explore the influence of process parameters on the mechanical properties of the printed material. Nondestructive evaluation (NDE) methods are widely employed for material characterization and do not damage the material itself [16; 17; 18]. Some nondestructive techniques permit inspection during the printing process (in situ) [19]. One of the leading methods of quality assessment of additively manufactured parts is X-ray computed tomography (CT). This is an ex situ method used in defect characterization and classification after the manufacturing process is completed [20; 21; 22]. Although it permits the assessment of defect sizes and locations, it may not provide information on the elastic properties of the printed material. This nondestructive technique is also used for assessing the mechanical and thermo-mechanical properties of PLA-based composites [23; 24]. Infrared imaging relies on analyzing thermal radiation variances, enabling the identification of defect shapes and contours within materials. This method can also be employed to capture thermal gradients across the surface of the printed part. Nevertheless, this method may not effectively detect small defects and does not provide information regarding the material's properties [25]. Ultrasonic testing (UT) is one of the most robust NDE techniques. UT is capable of detecting both surface and sub-surface defects, and identifying their locations and sizes. Additionally, ultrasonic testing can be employed to measure material properties [26; 27; 28]. This NDE technique could be used for both ex situ and in situ measurements. In situ implementation of this method and subsequent signal acquisition enable a qualitative evaluation of residual stresses and porosity [29; 30].