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Power transmission machine elements such as gears, cams, and bearings, are subjected to Hertzian contact stress. Ansys is a widely used FEA tool to analyze the Hertzian contact stress problems. In this work, 2D FEA analysis was carried out to understand two cylindrical contacts stress behaviour under plane strain, plane stress, and plane stress with 100 mm thickness using ANSYS 16.2. An initial convergence study was carried out to obtain the optimum mesh and compared with the theoretical value. The simulation was performed using the optimum mesh size between two identical cylinders with appropriate boundary conditions and a load of 5000 N. Von-mises stress, and normalized stress was plotted under plane strain, plane stress, and plane stress with 100 mm thickness. Subsurface stress was observed under plane strain condition, whereas surface stress was achieved from the plane stress and plane stress with 100 mm thickness. The behaviour of a normalized stress plot for plane stress condition is almost similar when compared to the plane strain condition. A gradual decrement in normalized stresses was observed with an average slope range of 2.37–12.38 for both plane strain as well as plane stress conditions. In contrast, rapid decrement in normalized stresses was observed with an average slope range of 15.96–32.85 under plane stress with 100 mm thickness.

Short fibre reinforced thermoplastics are being considered for light- and medium-duty engineering applications because of their improved mechanical strength combined with cost-effective advantages. In recent years, the carbon nanotube reinforced thermoplastics are being preferred over the short fibre reinforced thermoplastics because of the absence of directional shrinkage characteristics, directional mechanical and tribological properties. In this work, 1 wt% carbon nanotube–polypropylene material was injection-moulded to spur gears and evaluated for the durability using in-house developed power absorption gear test rig. During testing, the net surface temperature of the test gears and in-line torque available at the driver and driven shafts were continuously measured. The measured torque was used to evaluate the transmission efficiency of the test-steel gear pair. The measured net surface temperature was correlated with the gear failure mode. Test gears were run up to failure or up to 8.6 × 105 cycles, whichever occurred first. Worn-out gear tooth surfaces were observed using an optical and scanning electron microscope to understand the wear mechanism. In the initial stage of service, test gears exhibited less wear near the pitch region compared to the tip and root regions. This behaviour is due to the maximum sliding velocities at the tip and root regions compared to the pitch region. The carbon nanotube–polypropylene gears exhibited lower surface temperature (5−10 ℃), improved service life (30%−80%) and higher transmission efficiency (1−1.5%) compared to the polypropylene gear.

In the recent years, utilization of non-standard gears have increased due to the improved load carrying capacity and improved durability. However, these non standard gears are manufactured by non-conventional manufacturing process including wire cut electric discharging machining (WEDM). Standard gears are manufactured by conventional machining process, hobbing. This work reported the performance of injection molded polymer gear paired with a steel gear manufactured by conventional hobbing and wire cut electric discharge machining process. WEDM steel gear surface exhibited poor surface topology and higher hardness when compared to that of conventional machined steel gear. Measured net surface temperature of polymer gear at various loads (2-3 Nm) confirmed a temperature rise of 10-15°C when paired with WEDM gear compared to that of hobbed and ground gear. Polymer gear paired with WEDM exhibited inferior fatigue performance when compared to the polymer gear paired with hobbed and ground gear.

Polymer gears can replace metallic gears in many engineering applications; however, thermal sensitive mechanical properties of the polymers limit its wide application. Gear tooth surface interaction as well as material hysteresis generates heat in the gear operation. There have been many attempts to improve the gear performance by design modifications as well as with new materials to withstand against thermal damages. In this work, compressed air cooling method is adopted to improve the wear resistance of injection molded polypropylene spur gears. For the chosen gear and test conditions, continuous measurement of gear surface temperature confirmed that compressed air cooling lowers the temperature up to 15 ℃. Periodical measurement of gear tooth thickness confirms that wear resistance increases up to 100%. Continuous measurements of torque available in driver and driven end confirmed that a 2% increase in transmission efficiency of the gear pair. Test gear tooth surface after a finite number of cycles also confirms the effect of compressed air cooling on wear resistance. Mao model is used to predict the gear surface temperature and found to be in close agreement with experimental results.

The measurement from the indentation process depends on the amount of pile-up or sink-in around the contact impressions. In this paper, finite element concept is utilized to study the pile-up and sinkin behaviour for the wide range of materials with different young\'s modulus, yield stresses, strain-hardening exponents and co-efficient of friction values. The exact indentation model is created by using the two dimensional axisymmetrical model for simulating the spherical indentation process on the lines of Taljat and Pharr (2004) work. The result shows that during spherical indentation process the amount of pile-up is greatly influenced by the strain hardening exponents in addition to other material properties and depth of penetration. The numerical results from the finite element analysis are also validated using the exact multilinear material properties obtained from the tensile testing for the materials like mild steel, brass and aluminium.

Gear performance is significantly influenced by the interacting surface conditions; however, very few attempts have been made to understand the effect of mating surface condition. In this work, injection molded polypropylene gears were meshed with machined metal gears having different surface conditions. Bearing characteristics of the machined gears were obtained through non-contact profile meter and correlated with real area of contact and friction. Injected molded gears were run against metallic gears at various loads and net surface temperature due to the surface interaction was measured with non-contact temperature sensor and correlated with friction.

In this work, abrasive wear performance of multi-walled carbon nanotube (CNT) reinforced polypropylene (PP) has been studied. Various weight percentage of CNT/PP nanocomposites were prepared through melt intercalation with the aid of twin screw extruder. Prepared composites were subjected to sliding wear against silicon carbide abrasive paper with the aid of pin-on-disc configuration. Worn out surface morphology were observed under microscope and non-contact profilometer to understand the wear mechanism. Since the dominant friction mechanism observed to be is ploughing, no lubrication effect of CNT was observed. CNT/PP composite exhibits inferior wear resistance than unfilled PP due to its brittleness. With increased CNT, wear resistance found to decreases.

Asymmetric tooth profiles with different pressure angle at drive and coast sides are being considered to enhance the gear performance. In this work, experimental investigations were carried out to evaluate the fatigue and wear performance of injection moulded asymmetric polypropylene spur gears using the power absorption gear test rig. Test gears exhibited wear failure at lower loads and tooth bending failure at higher loads. Periodic measurement of gear tooth thickness and weight loss was carried out to quantify gear tooth wear. Sudden rise in measured gear temperature and failure morphology confirmed bending failure at higher loads. The results revealed that asymmetric gears exhibited inferior performance than that of symmetric gears. This behaviour is due to the reduced contact ratio, increased normal load and increased height at which worst load act on the gear tooth profile for the considered test conditions.