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The metal additive manufacturing (AM) process has proven its capability to produce complex, near-net-shape products with minimal wastage. However, due to its poor surface quality, most applications demand the post-processing of AM-built components. This study proposes a method that combines convolutional neural network (CNN) classification followed by electrical discharge-assisted post-processing to improve the surface quality of AMed components. The polishing depth and passes were decided based on the surface classification. Through comparison, polishing under a low-energy regime was found to perform better than the high-energy regimes with a significant improvement of 74% in surface finish. Also, lower energy polishing reduced the occurrences of short-circuit discharges and elemental migration. A 5-fold cross-validation was performed to validate the models, and the results showed that the CNN model predicts the surface condition with 96% accuracy. Also, the proposed approach improved the surface finish substantially from 97.3 to 12.62 μm.

Objectives Although at least 598 genes are involved in the development of the hypothalamo–pituitary–testicular (HPT) axis, mutations in only 75 genes have so far been shown to cause delayed puberty. Methods Six male patients with failed puberty, manifested as absence of pubertal changes by 18 years of age, underwent whole exome sequencing of genomic DNA with subsequent bioinformatics analysis and confirmation of selected variants by Sanger sequencing. Genes having plausibly pathogenic non-synonymous variants were characterized as group A (previously reported to cause delayed puberty), group B (expressed in the HPT-axis but no mutations therein were reported to cause delayed puberty) or group C (not reported previously to be connected with HPT-axis). Results We identified variants in genes involved in GnRH neuron differentiation (2 in group A, 1 in group C), GnRH neuron migration (2 each in groups A and C), development of GnRH neural connections with supra-hypothalamic and hypothalamic neurons (2 each in groups A and C), neuron homeostasis (1 in group C), molecules regulating GnRH neuron activity (2 each in groups B and C), receptors/proteins expressed on GnRH neurons (1 in group B), signaling molecules (3 in group C), GnRH synthesis (1 in group B), gonadotropins production and release (1 each in groups A, B, and C) and action of the steroid hormone (1 in group A). Conclusions Non-synonymous variants were identified in 16 genes of the HPT-axis, which comprised 4 in group A that contains genes previously reported to cause delayed puberty, 4 in group B that are expressed along HPT-axis but no mutations therein were reported previously to cause delayed puberty and 8 in group C that contains novel candidate genes, suggesting wider genetic causes of failed male puberty.

Objectives: The present study was designed to compare anthropometric parameters, sexual maturation rating (SMR) and plasma follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) levels in male delayed puberty patients and age matched healthy controls and determine whether a difference exists between these parameters before and after 18 years of age in delayed puberty patients. Methodology: Anthropometric parameters (height, weight, body mass index (BMI), bone age), SMR (penile length, testicular volume, pubic and facial hair stage) and plasma concentrations of FSH, LH and T were determined through respective ELISA in 37 sporadic delayed puberty male patients of 14-23 years and 55 age matched controls visiting Shifa International Hospitals Ltd., Islamabad, Pakistan Institute of Medical Sciences, Islamabad and Military Hospital, Rawalpindi, Pakistan. Data were interpreted using Student’s t-test and ANOVA. Results: The height of delayed puberty patients was lower than controls from 14-17 years, whereas weight of delayed puberty patients was slightly more than controls from 17-23 years; most of patients were in over-weight category. Bone age of most of patients was slightly delayed than chronological age.

Selective laser melting (SLM) of titanium–aluminium (TiAl) alloy components has gained significant attention in the modern industrial world. The flexibility of the SLM process in producing complex shapes with minimum utilization of material and energy makes it dominant over other manufacturing techniques. As aerospace and biomedical industries demand complex-shaped TiAl alloy components, part fabrication using SLM becomes the ultimate solution. However, the unacceptable level of surface integrity and anisotropic behavior of SLM components demand post processing operations such as laser polishing, chemical polishing, and conventional polishing methods. In this study, a recently developed polishing method called wire electrical discharge polishing (WEDP) is performed on TiAl alloys for obtaining a smooth and defect-free surface. This study aims to investigate the micro-layer modification occurring to the WEDP-processed surface in detail. The experimental results establish the effectiveness of WEDP method in terms of improved surface integrity. The surface finish (Sa) got enhanced by ~88% after WEDP processing. In addition, the thickness of recast layer formed by WEDP was found to be minimum. Moreover, post-processing of TiAl alloy resulted in better surface morphology specifically at lower settings of peak current. It is noteworthy that the migration of wire material was minimum with zinc-coated brass electrode compared to the normal brass electrode. Hence, coated wire electrodes are recommended for WEDP process. In short, an excellent surface integrity can be achieved using WEDP process through favorable surface modification aided by lower peak current and coated wire electrodes. Furthermore, less electrode wear observed in WEDP process enables the deployment of lower feed rates leading to minimal electrode consumption.

Deep hole drilling is a technique used for producing holes in materials at high depth to diameter (L/D > 10) ratios. Applications demanding deep holes can be extensively found in aerospace, automotive, marine and oil & gas industries. Conventional drilling techniques such as twist drilling and gun drilling are commonly used for drilling deep holes in the aforementioned applications. However, these methods can cause problems of rapid tool degradation, chip clogging, premature tool failure and undesirable sub-surface alterations to the hole surface. Moreover, these problems get aggravated when the material is difficult-to-cut (Ni/Fe/Co based superalloys) in nature. Therefore, non-conventional machining process finds scope in order to overcome the problems associated with conventional drilling. Electrical discharge drilling (EDD) can be used for fabricating dimensionally accurate holes irrespective of hardness of the material. Nevertheless, the inefficiency in flushing of debris particles at higher depths and its subsequent accumulation is a critical challenge during EDM deep hole drilling. The reason behind flushing inefficiency based on fluid physics has not been completely explored by researchers yet. In this paper, the flow behaviour of micro debris particles in the flushing channel during EDD has been analysed using CFD simulation by employing discrete phase modelling (DPM). The developed model set up is also validated with a benchmark fluid mechanics problem. The steady state CFD analysis results show the formation of multiple recirculation zones in the flushing channel. This can be attributed to the adverse pressure gradient experienced when the dielectric fluid passes from the machining gap to annular gap. Moreover, the presence of recirculation zones reduces the flow momentum and thereby debris particle velocity. This leads to accumulation of micro debris particles in the recirculation zones over time. The results also show that the trajectory of the particles is dependent on the size of the particles generated during material removal. The outcomes of numerical analysis in the present paper can serve as a foundation for the future studies in improving the performance of EDM deep hole drilling.

Fabrication of deep holes (depth to diameter ratio >10) using electrical discharge drilling (EDD) has gained momentum in the areas of aerospace, automotive and biomedical industries. However, formation of recirculation zones in flushing channel causes accumulation of debris particles at higher depths of drilling. This leads to secondary discharges within the flushing channel resulting in excessive tool wear, dimensional inaccuracy and hole tapering. The present paper proposes a novel tool geometry having orifices at the bottom end of tool electrode with an aim to improve debris evacuation. The effectiveness of proposed method is established through CFD simulations and experiments.

Additive manufacturing (AM) is a rapidly developing technology in biomedical, aerospace and automobile industries. However, adoption of this technology on a larger production scale remains limited. This is primarily due to the drawbacks of present AM processes associated with achievable dimensional accuracy and surface integrity of the fabricated component. The average surface roughness (Ra) of the component ranges from 3 μm to 10 μm with stair-stepping effects, balling on surfaces resulting in poor dimensional accuracy. Therefore, post-processing methods like abrasive flow finishing, laser polishing, chemical polishing and traditional finish machining is often used to meet the desired surface integrity and accuracy. However, some of these post-processing methods are quite expensive leading to overall increase in the production cost of the component. On the other hand, methods like etching and sand blasting are time consuming and not suitable for component with intricate geometries. In this paper, low energy wire electrical discharge polishing (WEDP) has been employed to achieve the desired surface integrity and finish. Initially, experiments were conducted to analyse the finishing achieved on planer additive manufactured stainless steel (SS316L) specimens. A significant reduction in roughness of maximum 80 % was obtained at various settings for pulse on time and servo voltage. In addition, SEM and EDS analysis were also carried out to study the microstructure and composition after WEDP. From the study, it was found that the WEDP process is a promising method to finish metallic AMed components.

In recent years, the popularity of nickel-based super alloys has been on the rise due to their widespread application in oil and gas, aerospace and automobile, marine and biomedical industries. The unique combination of superior mechanical and chemical properties like hardness, strength, temperature and corrosion resistance is responsible for the extensive application of these alloys. However, these properties pose challenges during the conventional machining of nickel-based super alloys. The low thermal conductivity and high work-hardening characteristics of Inconel 718 make it difficult to machine. To overcome the aforementioned problem, a hybrid non-contact electrical discharge and arc-machining process has been employed. In this process, an additional DC power supply is employed in conjunction with the normal EDM-pulsed power supply. Furthermore, the selection of proper electrode material plays an important role in defining the machining performance. In this study, in order to select a suitable electrode material for the newly developed process, several experimental investigations have been conducted with three different electrode materials, namely brass, copper (Cu) and copper tungsten (CuW). The results have shown that, for all the current settings, brass electrode provides the highest material removal rate (MRR), followed by Cu and CuW electrodes. However, CuW exhibited the lowest electrode wear rate (EWR). Moreover, the average surface roughness and surface characteristics of the electrodes after machining were investigated as well. Based on all the performance parameters, CuW appears to be the best choice for the hybrid process to machine Inconel 718.

The present research aimed at analyzing Reader’s digest to enhance vocabulary related to health, home, food, and travel of tertiary level Pakistani students. The study also designed to develop students’ knowledge in the vocabulary related aspects including meaning, spelling, word class, and word usage. According to Alqahtani (2015), vocabulary plays an important role in language learning and a learner may face problems in comprehension if s/he does not possess sufficient word knowledge. The present study has focused on the formal vocabulary teaching through Reader’s digest that has contributed a great deal in implementing new methods of language teaching. This mixed method research used qualitative and quantitative methods to analyze the effectiveness of Reader’s digest in developing vocabulary of BS economics’ students studying at a Pakistani university. The study used an experiment to analyze the effectiveness of Reader’s digest using a pretest-posttest design. A closed-ended questionnaire and an interview were also used to know the responses of the participants regarding the effectiveness of Reader’s digest for vocabulary enhancement. The study concludes that Reader’s digest is a useful authentic material to enhance vocabulary related tohealth, home, food, and travel of tertiary level Pakistani students. It is also concluded that Reader’s digest improves knowledge of vocabulary related aspects such as spelling, word class, and word usage, as the results of post-test demonstrate a significant improvement in students’ knowledge related to these areas.

Application of deep holes is extensively found in the oil and gas industry to manufacture downhole equipment. These deep holes are fabricated in drill collars to deploy delicate sensors downhole for obtaining vital information like temperature, pressure and other geo-physical data from the bottom of the hole. High temperature and corrosion resistant materials like Inconel 718 is often used for drill collars to shield these sensitive communication equipment from the hostile downhole environment. Gundrilling is an established hole making method known for drilling precise and high aspect-ratio (AR>10) holes in conventional materials such as steels, cast iron and aluminium alloys etc. However, gundrilling of Inconel 718 offers unprecedented challenges like excessive tool wear, hole straightness deviation due to poor thermal conductivity and work-hardening tendency of the alloy. Moreover, as the drilling depth increases the deviation is further exacerbated due to the low rigidity of long gundrill shafts. The present study in the Phase 1 introduces a dynamic model using multispan Euler-Bernoulli beam theory to evaluate the effectiveness of coolant pressure and rotation speed during deep hole fabrication in Inconel 718. In addition, experimental investigations have been conducted to validate the model by studying the effects of coolant pressure and rotation speed on straightness of the fabricated holes. It was found that the straightness deviation was 0.37 mm corresponding to 137.89 bar and 1600 rpm coolant pressure and rotation speed respectively. In Phase 2, a non-contacting EDM process was used to fabricate a straight guide hole followed by conventional gundrilling (CG) with optimum pressure (137.89 bar) and speed (1600 rpm) obtained from the Phase 1 trials. The experimental results revealed that the thrust force reduced drastically from 800 N (CG) to 250 N (EDMG). Moreover, a significant improvement in both rake wear and flank wear was also observed. Finally, a straightness deviation of 0.19 mm was recorded for a maximum drilling depth of 350 mm which is 48.65% lesser than CG. From the study, it was found that this novel EDMG process improved the drilling capability of Inconel 718 by reducing the thrust force generated, enhancing tool life and minimizing the straightness deviation.

Electrical discharge machining (EDM)—one of the unconventional manufacturing processes—has found intensive applications in high-performance engineering sectors, that is, precision manufacturing. The superior manufacturing benefits exhibited by EDM in terms of surface quality, microstructure, micron-scale manufacturability and complex profiles have established it as one of the highly used noncontact machining processes. Moreover, EDM is one of the efficient ways of machining Ti and Ni-based superalloys used in oil–gas, aerospace, and automobile industries. However, superior material properties make the conventional EDM approach difficult to machine these exotic materials. Integrating the arc machining module to the EDM system, the hybrid electrical discharge and arc drilling can increase the material removal rate and hence the machining performance. This is due to the high thermal intensity of the sparks/arcs imparted by this compound process. Additionally, ongoing research on EDM shows that further performance improvement is possible by the integration of multiple unconventional manufacturing processes. For instance, the integrated use of arc machining with EDM revealed improved machining time, part accuracy and surface integrity. As such, this chapter presents the compounding of EDM with different arcing/sparking/melting processes along with detailed working principles and examples. Moreover, the performance of these processes is evaluated in terms of multifarious criteria, that is, surface integrity, material removal rate, electrode wear ratio, machining time, precision dimension, etc. The technology assistance process (i.e., vibration) for micro-EDM to promote better machinability is also presented. Finally, the machine tool capability to lead future micromanufacturing is highlighted for the combination of various machining processes with micro-EDM in a single machine to meet the growing demand of miniaturization.

This chapter summarizes the development of Spark erosion machining (SEM)-based hybrid processes aimed at overcoming the aforesaid issues, detailing their working principles and mechanisms of material removal. In SEM, every discharge of spark over the workpiece and the tool surface removes a very small volume of material by melting and vaporization. Ejection of the molten material creates a crater on the workpiece and the tool electrode surface. The size of these craters depends on the discharge energy of the spark. The chapter presented details of various hybrid or compound processes developed using SEM as the base process, with the objective of overcoming its limitations and improving its performance. Descriptions in this chapter provide insights into and guidelines for the development of more compound processes of SEM in future.

In recent years, Inconel 718 is widely used in industries like aerospace, oil and gas, and automobile due to their unique combination of hardness, strength, temperature, and corrosion resistance properties. However, these materials pose challenges during conventional machining due to their high work hardening tendency, poor thermal conductivity, and chemical affinity towards the tool material. Consequently, rapid tool wear during the machining of Inconel 718 results in poor productivity. To overcome these issues, a non-contact hybrid electrical discharge and arc machining (HEDAM) process has been developed to machine such difficult-to-cut materials. Firstly, the design and development of the HEDAM circuit has been discussed. Subsequently, the working principle of the newly developed process has been studied followed by its performance comparison with the conventional EDM process. In addition, the material removal mechanism has also been discussed in detail. Finally, experimental results were reported, where holes were drilled using the developed HEDAM process. The HEDAM process has exhibited significant improvements in terms of material removal rate (MRR) which is around 12 times higher and electrode wear ratio (EWR) that is half when compared to conventional EDM. This high performance HEDAM process resulted in successful and efficient drilling of Inconel 718.

Electrical discharge machining (EDM) is a non-contact machining process that removes material through spark erosion and is often used for drilling holes in difficult-to-cut materials such as Nickel-based super alloys. However, this process becomes slower with the increase of the hole depth. This is because the flushing pressure becomes inefficient for the effective evacuation of process debris leading to secondary discharges and resulting in increased machining time. This study presents an innovative simultaneous flushing and vacuum-assisted debris removal system, which facilitates better debris removal for deep-hole EDM drilling. Improvement in the drilling time and better surface roughness have been achieved using the developed setup. To evaluate the performance of the vacuum-assisted debris removal system, a novel computational fluid dynamics model is also proposed in this study. Experimentally measured particle size data of full length scale act as a reference for the proposed numerical model.The analysis presented in this study provides significant insight into sizes of the debris particles in different machining conditions, in full length scale using an automated image processing technique. The presented numerical model can be used to investigate the various factors influencing the removal of debris from the machining zone. The experimental and numerical components of this research complement each other in the design of the presented vacuum-assisted debris removal system.

Metal additive manufacturing (AM) is gaining momentum among modern manufacturing techniques due to its flexibility in fabricating complex shaped components with minimum scrap. However, the technology cannot be directly employed in producing parts on a larger scale because of the poor surface integrity and average mechanical properties. This highlights the importance of post processing AM components with suitable methods that can overcome these limitations. The existing finishing methods for AM components such as laser polishing, chemical polishing, abrasive finishing, mechanical polishing and other hybrid combinations have their own limitations. Difficulty in accessing complex part surfaces, loss of dimensional accuracy and deterioration in material surface and properties are some of the major challenges related to existing finishing methods. In the present work, wire electrical discharge polishing (WEDP) technique has been proposed in improving the surface integrity and mechanical properties of metal AM components. Experiments were carried out on selective laser melted (SLM) stainless steel (SS316 L) specimens at different settings of pulse duration and servo voltage. A detailed investigation into surface finish and morphology was performed to determine the enhancement in surface integrity after WEDP. In addition, investigations were conducted to evaluate the improvement in mechanical properties such as microhardness and tribological performance. The irregularities/defects over the SLM surface were removed and a maximum finish of 0.739 μm was achieved. A negligible amount of wire material was migrated to the SS316 L workpiece surface after WEDP process. Moreover, reduction in crystallite size and microstrain was obtained based on results from XRD analysis. Martensite formation and shift in peaks were also evident from XRD pattern after WEDP process. An increase in microhardness (∼ 317 HV) at the subsurface and reduction in coefficient of friction (∼ 0.35) were also achieved. Based on aforementioned results, WEDP showed excellent capability in improving the surface integrity and mechanical properties thereby providing a promising hybrid option for combining with metal AM technology.

Inconel 718 is one of the most widely used super alloys in industries like oil and gas, aerospace and automobile. However, properties like poor thermal conductivity and work hardening tendency make it difficult to machine, using a conventional machining approach. EDM is one of the effective and efficient ways of machining this exotic material. However, the material removal rate (MRR) is very low. In an attempt to enhance the performance of EDM, an arc machining module has been integrated into the existing EDM system and the compound process is named hybrid electrical discharge and arc machining (HEDAM). Due to the high thermal intensity of the sparks/arcs imparted by this process, the material removal rate is elevated. To understand this process better, a comparative thermal modelling between HEDAM and EDM has been presented in this article. Firstly, a thermal analysis is performed for the EDM and HEDAM processes to understand their respective erosion efficiencies. Finally, the numerical simulation for MRR of both EDM and HEDAM is presented. Unlike other EDM models, in this simulation, the thermophysical properties of the material were considered to be temperature-dependent and the latent heat of fusion was incorporated into the modelling process. A comparative analysis was also performed, which showed that incorporating such variables increases the accuracy of the obtained results. The study revealed that the spark radius in HEDAM is larger in size and more stable. Consequently, this resulted in HEDAM to have about three times more erosion efficiency compared to conventional EDM.

Composition, structure and properties of the products of self-propagating high-temperature synthesis (SHS) are characterised by some distinctive features. High heating rate, fast cooling after rapid completion of the reactions and steep temperature gradients make SHS very effective in producing in situ composites with ceramic reinforcements. In the present work, hardfacing of AISI304 substrates has been done by fabricating a hard ternary ceramic matrix composite layer of Al2O3–TiB2–TiN by laser surface treatment at different scan speeds. The formation of the surface layer is due to laser-triggered SHS followed by laser melting. A mixture of Al, TiO2 and hBN has been used as a precursor for the SHS reaction. The study of the microstructure of the as-fabricated composite layer reveals the co-existence of TiB2 and TiN phases in the nanometric size range in Al2O3 matrix. The presence of all the phases has been confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transm...