Manufacturing Engineering

Static and dynamic performance parameters of three-lobe fluid film bearing, operating with TiO₂-based non-Newtonian lubricant, are obtained. The Krieger–Dougherty model of effective is used to obtain the viscosity of nanolubricant for a fixed concentration of nanoparticle dispersed in base lubricant. Reynolds equation is modified to incorporate couple stress effect, and then, finite difference method (FDM) is used to solve it to obtain different performance parameter. For varying concentration of nanoparticle in base lubricant, direct and cross-coupled dynamic coefficients (stiffness and damping) are obtained. Results show that flow coefficient and load carrying capacity increases, whereas friction variable decreases, but it does not disturb the stability of three-lobe fluid film bearing working with TiO₂-based non-Newtonian lubricant. Dynamic coefficients and attitude angle do not vary with the concentration of solid nanoparticle for a fixed couple stress parameters.

DH36 is commonly known hull structure steel widely used in shipbuilding industries. Fusion joining of this high-strength steel results in degradation of weld quality. This article focuses on friction stir welding of DH36 steel. Single-pass butt joints were performed on 4-mm thick plates of DH36 steel using tungsten carbide (WC-10 wt.% Co) alloy tool. Welding was carried out at rotational speed of 300 and 450 rpm keeping traverse speed of 132 mm/min as constant. Transient thermal history was recorded using K-type thermocouples. It was observed that the temperature on the advancing side was higher than that of the retreating side. Peak hardness values were observed in the stir zone. No heat-affected zone softening was observed in the welded joints. The welds were obtained with superior tensile strength and comparable ductility to the base material. During fractography analysis for the tensile sample, dimples were observed which indicated the ductile mode of fracture. Tensile properties and microhardness were correlated with the microstructure obtained in the stir zone. Tool wear was observed during welding which was characterized by visual inspection, FESEM-EDS analysis, and surface roughness of the tool pin. From the investigation, it was observed that sound-quality welds could be produced in DH36 steel with superior tensile strength and comparable ductility.

In this experimental investigation, the end milling operations were carried out on an aluminium alloy at three machining conditions (dry, wet and cryogenic CO₂). The machining input parameters of the end milling processes were the depth of cut, cutting speed and feed rate. The cutting temperature (T_c), axial force (F_z), normal force (F_y), feed force (F_x), the surface roughness (Ra), surface morphology, chip morphology and shape were analysed. The experimental results showed cryogenic CO₂ reduced the cutting temperature (T_c) by about 8–9% and 38–39% in comparison with wet and dry conditions, respectively. The high axial force (F_z) values were recorded in CO₂ coolant condition. The surface roughness and morphology, and chip shapes were compared. In a higher feed rate, the better surface roughness (Ra) values were obtained using CO₂ coolant. In addition, the absence of black spots on the chip surface was obtained by cryogenic CO₂ coolant condition.

In present study, experimental and numerical analysis on CO₂ laser welding of AISI 304 stainless steel sheet’s thickness of 1 mm was performed. Prediction of transient thermal history is essential while designing the welded joints. A 3D finite element (FE) model was developed using ANSYS 14.5 finite element package to determine the effect of welding process parameters, i.e., laser power and welding speed on thermal history of laser-welded joints. The influence of weld bead geometry obtained from experiment was considered in this 3D finite element (FE) model to simulate the moving volumetric heat source. The element birth and death technique was used in FE thermal analysis to simulate the progression of the laser weld zone. It was observed that the cooling rate was significantly affected by the varying laser power and welding speed. It was also observed that increasing laser power and decreasing welding speed lead to increase in size of fusion zone and heat-affected zone. The transient thermal analysis results obtained from FE model and experimental results were validated, fairly well, with maximum percentage error of 6.47% for the peak temperature.

In this analysis, a 3D finite element transient thermal model of friction stir welding (FSW) has been proposed. The heat generation in FSW consists of two main phenomena, i.e., heat generation due to friction between the tool and the workpiece and due to plastic deformation inside the material that is often termed as sliding and sticking conditions, respectively. A new heat source model is proposed in the article that accounts for both the heat generation conditions. The temperature distribution profile has been studied on the FSW butt joint of AA6061 plates. From the comparative study, a significant difference has been observed between the temperatures which have been obtained by only sliding heat source and the proposed heat source model in peak temperature. The proposed heat source model has been validated with the experiments and the error range in peak temperature lies within 5% with the experimental results.

The turning and boring scraps obtained on machining of aluminium is increasing day by day and these scraps are utilised for degraded applications in its next cycle of usage due to declined level of properties. Hence, recycling of aluminium machining scraps without compromising mechanical properties is highly essential to make it as alternative for primary aluminium made components. Therefore, the present study focused on production of the secondary aluminium alloy by recycling H30 aluminium turning and blocky scraps. Weight loss and energy consumption during production of the secondary aluminium alloy is measured. Chemical composition, porosity examination and mechanical properties were assessed on the secondary aluminium alloys and compared with the properties of the virgin H30 aluminium alloy. The mechanical properties of the secondary aluminium alloy are found lower than that of virgin H30 aluminium alloy. Therefore, alloying elements are added during recycling of blocky and turning scraps, and found that improved mechanical properties are attained. Thus the secondary aluminium alloy developed with better performance can be utilised for the automotive components and other applications wherever high strength is essential.

Mechanical components are subjected to wear during their functionality, which decreases the life of such components. The mechanical strength plays a major role for the same. Different heat treatments had been used to improve the mechanical strength of such components. In this paper, DCT (Deep cryogenic treatment) with post-tempering treatment was conducted on austenitic steel SS316 and its effect on mechanical as well as metallurgical properties was investigated through experimental testing’s. For post-tempering, two temperatures were selected (T₁: 350 °C and T₂: 250 °C). It was observed that the DCT samples with post-tempered treatment at T₂: 250 °C possess good tensile strength and hardness. The reason behind the same can be refinement of grains after DCT with tempered at T₂: 250 °C as seen from the microstructural analysis. Further, decrease in toughness was also observed for both the DCT samples. The conversion from austenitic grains to martensitic grains was also observed after DCT.

Titanium and its alloys especially Ti–6Al–4V and its ELI grade exhibit a unique combination of mechanical, physical, and corrosion resistance properties, which have led to their desirable response for critical and demanding aerospace, industrial, chemical, medical, and energy industry services. The mechanical properties of Ti–6Al–4V ELI can be altered significantly when subjected to different heat treatment cycles. β annealing of Ti–6Al–4V is one such heat treatment that finds extensive applications in industry. β annealing leads to formation of lamellar microstructure that has many desirable mechanical properties. In this work, microstructure and mechanical properties of lamellar Ti–6Al–4V ELI have been investigated.

Machining of stainless steel materials is known to be very difficult due to the formation of BUE, low heat conductivity, high ductility, high tensile strength, high fracture toughness, high work-hardening rates, and high modulus of elasticity and reactivity at high cutting speed with most tool materials. This work aims to study the influence of process parameters such as spindle speed, feed rate, point angle and cutting tool on surface roughness, hole diameter error, burr height, and chip study during dry drilling of 304L stainless steel. Dry drilling is considered to be environmentally friendly drilling process. The cutting tools considered was M2 HSS drills and these drills were subjected to deep cryogenic treated at −191 ℃ for 20 h and post-tempered at 180 ℃ for 2 h. Experiments have been conducted according to full factorial design. From analysis of variance (ANOVA), the most dominant parameters for surface roughness, burr height, and hole diameter error were found to be cutting tools. Furthermore, experiments have been conducted to evaluate tool life of untreated drill, cryogenic treated one-tempered drills, and cryogenic treated two-tempered drills at a constant speed of 650 rpm, feed rate = 15 mm/min, and point angle 118 ℃. Compared to untreated drills, the enhancement in tool life was 53.84% for DCT1T drills and 92.30% for DCT2T drills. Compared to DCT1T, enhancement in tool life was 23.8% for DCT2T drills.

Boron addition to 9–12%Cr steels has proved to be attractive for improving creep properties. In current work, mechanisms pertaining to enhanced creep performance on addition of 100 ppm boron in standard P91 steel were investigated with the use of scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM). Parent metals of boron free P91 steel (P91) and boron-added P91 steel (P91B) were subjected to impression creep at a stress of 410 MPa and 625 ℃ by keeping depth of penetration as same for both cases. The deformed plastic zones formed on the corner of indenter and beneath the indenter were examined. TEM analysis revealed a high coarsening rate of precipitates in impression crept P91 steel than P91B. Geometrically necessary dislocation density as determined by EBSD analysis was same in P91B steel after impression creep. The recrystallized fraction of grains was considerably higher in P91B steel as measured through grain average misorientation (GAM). Pinning of dislocations by precipitates was poor in P91 steel after an impression creep test as observed in TEM.

In recent years, micro-textured cutting tools have shown great potential to eliminate the use of cutting fluids and move towards dry machining at least for limited applications. Even then, at higher load, severe friction exists at dry sliding contacts, resulting in large amount of heat generation, high temperature and wear. There is a vast scope to further enhance the tribological performance of micro-textured surfaces during dry sliding contact for heavy load applications. One such way is to coat the micro-textured surface with solid lubricants. In this work, mechanical micro-textures were fabricated on the surface of the high-speed steel (HSS) pins using the scratch tester. Mechanical micro-textured HSS pins were coated with graphite, calcium fluoride (CaF₂) and molybdenum disulphide (MoS₂). Tribological performance of untextured, uncoated mechanical micro-textured and solid lubricant (graphite, CaF₂ and MoS₂)-coated mechanical micro-textured HSS pins were investigated using pin-on-disc tribometer in terms of wear, coefficient of friction, weight loss and wear coefficient of pins. Afterwards, worn-out surfaces of pins were observed under field-emission scanning electron microscope, optical microscope, non-contact surface profilometer and energy-dispersive spectroscopy to understand the wear mechanism as well as the elemental composition of the sliding surface. Machining performance was also compared with untextured, uncoated textured and solid lubricant (graphite, CaF₂ and MoS₂)-coated mechanical micro-textured HSS cutting tools. The results show that MoS₂-coated mechanical micro-textured HSS pins and cutting tools provided the best tribological and machining performance among all.

Acrylic heat resistant (BS-476) glass is highly demanded material in aerospace and automobile industries. It is also used in boiler and furnace, because of its unique properties like; excellent transparency, good dimensional stability, hardness, poor thermal conductivity etc. In the present research, the impact of various input machining parameters (Slurry concentration (% in ltr.), type of abrasive, power rate (Percentage), grit size (µm), HF acid Concentration (% in ltr.) and tool materials on output response material removal rate (mm³/min), tool wear rate (mm³/min), surface roughness (micron) and hole deviation (mm) has been investigated and optimized by Grey Relational Analysis (GRA). The experiments have been performed by using Taguchi’s L₂₇ orthogonal array. Through analysis, it concludes that GRA optimum parameters give 100, 168, 72 and 48% improvement in material removal rate, tool wear rate, surface roughness and hole deviation.

This chapter discusses the distribution of temperature resulted by frictional heat during friction stir welding (FSW) butt-joint of aviation grade AA6082. Experimental investigation has been conducted with varying rotational speed and welding speed. Eight L-shaped k-type thermocouples are employed to measure the resulting temperature. Least square method is employed to quantify the temperature of nugget zone (NZ). After that, a thermal map of friction heat has been developed to study the temperature at different locations. Furthermore, it is attempted to establish a correlation between frictional heat and joint properties.