PSI - Issue 51

Mohammed Algarni et al. / Procedia Structural Integrity 51 (2023) 185–191 M. Algarni/ Structural Integrity Procedia 00 (2022) 000–000

188 4

Fig. 1. The experiment set ( left ), a fractured specimen after being loaded (middle), different fracture patterns for specimens with 0º, 45º, and 90º RSA’s (LYT = 0.3mm and IFD = 80%) ( right ).

3. Experimental Results and Theoretical Modeling 3.1. Tensile Strength Modeling and Optimization

The tensile strength of each specimen is the maximum resistance to failure in newtons (N). The strength results for each set of the combination were averaged and recorded. The experimental results show that the strength weakens as the RSA shifts toward 90º. Moreover, the thicker the LYT, the greater the strength becomes. In addition, the strength increases as the IFD increases. The results were analyzed in MATLAB, and a second-order mathematical model was created to present the effect of each process parameter. The model is based on a quadratic equation (Snee (1975)) with the methodology described in (Snee (1985)) and the ranges of the following: 0º ≤ RSA ≤ 90º, 0.1mm ≤ LYT ≤ 0.3mm, and 30% ≤ IFD ≤ 80%. The developed model has six constants, as shown in Eq. (1), and its results are shown in Fig. 2 ( left ). Based on Eq. (1), the optimized set of process parameters for maximum tensile strength (1007 N) is RSA = 0º, LYT = 0.3mm, and IFD = 80%. � �� � � � ���� � � ��� � � ������ � � � ��������� � � ��������� � (1)

Fig. 2. The tensile strength ( left ) and strain at fracture ( right ) experimental results vs. modeling results.

3.2. Strain at Fracture Modeling and Optimization The value of the strain at fracture is the delta in the length of a specimen during the testing post fracture over to its original length. As shown in table 1. The experimental strain at fracture ranges from 1.32% to 2.45% for all sets of combinations. The lowest stain was for the set combination number one, whereas the highest was for number 27. In general, the process parameter that most significantly affected the strain behavior was the RSA. The strain at fracture increases as the RSA increases. In addition, the strain at fracture increases as the LYT increases. The specimens with higher IFD showed higher strength with high infill percentages. A second-order mathematical model was created to show the impact of the process parameters on strain at fracture with the same ranges for each process parameter. The model reads as in Eq. (2), and its results are shown in Fig. 2