PSI - Issue 46

Adis J. Muminović et al. / Procedia Structural Integrity 46 (2023) 125 – 130 A.J. Muminovi ć et al. / Structural Integrity Procedia 00 (2021) 000–000

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(2020) and Dimić et al. (2018) analyzed different materials and shell thicknesses to achieve the optimal mechanical properties. Recent topics related to polymer gears include wear (Yousef et al. 2015), friction (Aziz et al. 2020), thermal characteristics (Zhang et al. 2020), service life (Glodež et al. 2018, Woo et al. 2019), durability (Hlebanja et al. 2019) and failure analysis (Trobentar et al. 2020). Ramadani et al. (2018 and 2021) applied the topology optimization of gears to obtain a lightweight and low-vibration gear body. Muminovic et al. (2019, 2020) and Pandžić et al. (2021) numerically analyzed the tooth shell thickness of spur gears as well as different tooth infill structures. In this paper, the influence of the infill volume percentage on fatigue life and failure types of 3D-printed gears made of polylactic acid (PLA) is investigated. Experimental tests were conducted using a custom-built gear test rig. Gear specimens with different infill volume percentages were tested under constant torque and speed. Analysis showed that the fatigue life of gears made of PLA increases significantly with an increasing infill volume percentage. Also, different types of failures were recorded depending on the volume percentage of gear infill. 2. Experimental analysis 2.1. Specimen material and infill definition In this study, the fatigue life and failure types of gears produced by 3D printing made of polylactic acid (PLA) are analyzed. PLA material properties are given in Table 1. Gears with 20%, 40%, 60%, 80%, and 100% of infill volume (Fig. 1) were manufactured and tested experimentally. The manufacturing parameters are listed in Table 2..

Table 1. PLA material properties (Annanto, et al. 2019)

Table 2. Additive manufacturing parameters

Units g cm � ⁄ MPA

Property Density

Value 1.24 3500 1287 0.36

Parameter Infill type

Value/Type Triangular

Elastic modulus Shear modulus Poisson’s ratio Yield strength

Shell thickness (all sides)

1 mm

MPA

Printing quality Support material

Normal (0.15 mm layer height)

-

None

MPa MPa

70 73 ~7

Printing temperature

200°C

Ultimate tensile strength

Elongation

%

40%

60%

20%

80%

100%

Fig. 1. Gears with different volume percentage of triangular infill structure