# Investigation of the Mechanical Properties of Spur Involute Gearing by Infrared Thermography
## 1 Introduction
The bending strength of the wheel tooth was experimentally tested, where the specific value for Nylon was a maximum of 4.6 kN, and for steel it was up to 65 kN. In a study [11], stress analysis was carried out and the stress values that were calculated for composite materials are approximately the same compared to structural steel, grey cast iron and aluminum alloy. So, from these analysis results, we concluded that the induced stress and strain of composite spur gear are almost equal compared to spur gear made of structural steel, grey cast iron and aluminium alloy. In this paper, they further publish the claim that substituting gears made by conventional methods for gears made of composite materials is a relevant alternative. After considering a number of input factors, this is an interesting claim that defies standard notions. In this paper [12], tooth contact analyses of spur gears are carried out through finite element analysis for the materials: glass fiber/epoxy composite, PEEK (Polyetheretherketone) and steel. A general finite element model has been developed to evaluate the contact stress in spur gears of the same geometry. From the result, it can be concluded that the deformation of the gear made of composite material is a little higher compared to the steel gear but it is lower than the values determined for the plastic gear. Since the rotational speed of the gear affects the analyzed mechanical properties of the materials such as stress and strain, so these analyses were performed for 2 different rotational speeds. It was concluded that the composite material has better alternative for steel and plastic material. In this publication [13], gears were printed from four polymeric materials namely ABS, Nylon 12, PC (Polycarbonate) and PLA. The result confirmed that Nylon wheel has 35% better mechanical properties compared to the other mentioned materials. In terms of durability and operational ease, lubrication of Nylon is usually not necessary which is its advantage over other plastic materials. It has good strength, elasticity and, compared to other plastic gears mentioned, a high durability. This material has a low coefficient of friction, high melting point and high interlayer adhesion. The disadvantage of nylon is the tendency to absorb moisture, where the material deteriorates [14]. It should be noted that gear lubrication in low speed, low frequency applications is not necessary. However, if a more severe environment application is contemplated, a white lithium, PTFE or silicone based lubricant should be used. PLA and PETG are predominantly made of organic substances, i.e., they respond better to less viscous vegetable oils [14]. In the vast majority of scientific publications, composite gears printed on a 3D printer are considered as a suitable alternative to gears made by conventional methods from metallic materials. For polymer gears printed from a single material type, Nylon is the most suitable material according to several studies. For the dimensional properties of gears, it is important to note that in general, gears are very sensitive to manufacturing precision. Therefore, wheels with a smaller modulus may have a problem with manufacturing accuracy. Wheels that are dimensionally larger are stronger and better able to handle the tolerance errors of a two-wheel shot [15]. When applying printed gears to practice in the long term, it is important to define the basic parameters and knowledge by which the gear should be evaluated, in case one would like to use it as an alternative for a metal gear: the 3D printing production technology, the original parameters and material of the gear, the dimensions and module of the gear, the operational lifetime of the gear. The technology of gear production using 3D printing is crucial in the first phase. Table 1 gives an overview of the most used 3D printing technologies and their tolerance limitations.