Balkrishna C. Rao

This paper discusses tensile testing of small samples of nanocrystalline Al6061-T6 alloy obtained from an unusual application of machining as a severe plastic deformation process. Ultrafine grained (UFG) shavings obtained from plane-strain cutting show higher hardness than the bulk material in agreement with existing literature. Application of restricted contact tools and extrusion-machining was explored to obtain shavings with minimum curvature to aid in tensile test specimen preparation. A novel method to prepare small tensile test specimens from these shavings has been described. During the tensile testing of UFG material, strains were measured using digital image correlation of natural speckles on the specimen. Specimens made from the UFG material had higher tensile strength and yield stress than the bulk, while ductility was lower. Lower values of Young's modulus were observed during the tensile testing of small specimens made from UFG as well as bulk material. © Materials Research Society 2014.

This work is focused on the development of a dual-layered diamond-coated tungsten carbide tool for machining titanium Ti-6Al-4V alloy. A hot-filament chemical vapor deposition technique was used to synthesize diamond films on tungsten carbide tools. A boron-doped diamond interlayer was added to a microcrystalline diamond layer in an attempt to improve the interface adhesion strength. The dual-layered diamond-coated tool was employed in machining at cutting speeds in the range of 70 to 150 m min-1 with a lower feed and a lower depth of cut of 0.5 mm rev-1 and 0.5 mm, respectively, to operate in the transition from adhesion- to diffusion-tool-wear and thereby arrive at suitable conditions for enhancing tool life. The proposed tool was then compared, on the basis of performance under real-time cutting conditions, with commercially available microcrystalline diamond, nanocrystalline diamond, titanium nitride and uncoated tungsten carbide tools. The life and surface finish of the proposed dual-layered tool and uncoated tungsten carbide were also investigated in interrupted cutting such as milling. The results of this study show a significant improvement in tool life and finish of Ti-6Al-4V parts machined with the dual-layered diamond-coated tool when compared with its uncoated counterpart. These results pave the way for the use of a low-cost tool, with respect to, polycrystalline diamond for enhancing both tool life and machining productivity in critical sectors fabricating parts out of titanium Ti-6Al-4V alloy. The application of this coating technology can also be extended to the machining of non-ferrous alloys owing to its better adhesion strength.

Tensile properties of metals are typically measured using dog-bone shaped specimens having dimensions as per specifications imposed by international standards organizations. However, these properties may be influenced by the size of the specimen, especially when the cross-sectional dimensions are lower. At lower length scales, microstructure could have an effect on the mechanical behavior. In this study, tensile experiments were conducted to investigate the effect of cross-sectional dimensions on Young’s modulus of Al6061-T6 materials. Due to the small size of the specimens, digital image correlation, a non-contact measurement technique was used to obtain strain filed in the gage section of the specimen. Spray paint or toner powder were used to produce speckle pattern on the specimen surface for better correlation of the images. For specimens having the thickness of the order of a fraction of a mm, the natural gray pattern observed on the surface of the specimen was found to provide a good speckle pattern. This natural speckle pattern was used to correlate the images instead of synthetic speckles, to avoid the effect of paint on the Young’s modulus being measured on specimens with cross-sectional dimensions below 1 mm. Young’s modulus was found to be constant at about 67 GPa for specimens whose area of cross-section was more than 3 mm2. When the area of cross-section was lesser, Young’s modulus was found to decrease with a decrease in area of cross-section. Larger spread in Young’s modulus was also observed in the specimens with area of cross-section < 1 mm2.

Sustainable development necessitates the management of progress in science and technology for society's betterment while preserving Earth's resources. In this regard, the appearance in recent years of low-cost sophisticated products consuming resources economically is a force for good. This effort terms each of these products as an advanced frugal innovation to highlight the frugality in resource consumption during the realization of these innovations through advances in various scientific disciplines. Other than 25 examples of advanced frugal innovations in a wide range of sectors from rural electrification to particle physics, a framework for the systematic realization of such innovations for sustainable development has also been described. The innovations showcased bring out the use of advances in science and technology or cutting edge knowledge for creating these low-cost sophisticated products. Moreover, the need for innovators typically with training in advanced knowledge areas to handle the sophistication in technology for the successful fruition of these innovations is also discussed. This effort supports the frugal design and frugal engineering of innovations, whether grassroots or the advanced type, through sound scientific principles for the creation of robust products, especially where the human life is at stake, in various sectors for all-round sustainable development.

The conservative nature of design in engineering has typically unleashed products fabricated with generous amounts of raw materials. This is epitomized by the factor of safety whose values higher than unity suggests various uncertainties of design that are tackled through material padding. This effort proposes a new factor of safety called the factor of frugality that could be used in ecodesign and which addresses both rigors of the classical design process and quantification of savings in materials going into a product. An example of frugal shaft design together with some other cases has been presented to explain the working of the factor of frugality. Adoption of the frugality factor would entail a change in design philosophy whereby designers would constantly make avail of a rigorous design process coupled with material-saving schemes for realizing products that are benign to the environment. Such a change in the foundations of design would abet the stewardship of earth in avoiding planetary boundaries since engineering influences a significant proportion of human endeavors.

Two new steel-reinforced, metal-matrix composites (MMCs), Kirksite + 1080 and Kirksite + M2 are developed by adding 25 wt% of AISI 1080/AISI M2 steel machining chips to a zinc-based alloy, Kirksite (4% Al and 3% Cu). The sliding wear resistance of the Zn alloy and the two MMCs, against AISI 52100 steel, is determined under increasing normal load (1-10 N) and temperature (25-150°C), using a pin-on-disc configuration. The MMCs are found to exhibit superior wear performance under all test conditions. At room temperature, a maximum wear reduction in excess of 70% is obtained for the composites relative to the Zn-alloy at the highest load of 10 N. This reduction is as much as 86% at 150°C and 1 N for the Kirksite + M2. The wear-reducing ability of the steel reinforcements is generally greater at the more severe contact conditions. The stability of the MMC matrices and recommended limits to the MMC operating temperatures are established using deformation measurements made via dynamic mechanical analysis. The principal wear mechanisms are analysed based on the sliding wear measurements, complemented by optical microscopy and SEM observations, and EDX microanalysis. The results show that the steel chip reinforcements are effective in improving the wear resistance of Zn alloys under severe conditions. Implications for use of low-cost machining chips as reinforcements to create MMCs for improved wear performance, and for recycling/reuse of these chips in advanced structural material systems are discussed. © 2013 Elsevier Ltd. All rights reserved.

In the present effort, enhancement of mechanical properties of Aluminium alloy, Al6061, due to cold-rolling is compared with that due to peak-ageing. Heat treatable Al6061 was cold-rolled with different pre-rolling conditions. Since different peak-ageing conditions are given in literature, a systematic study was conducted to determine the peak-ageing conditions for the procured aluminium alloy. Micro-Vickers hardness tests as well as uniaxial tensile tests were conducted to evaluate the mechanical properties. Cold-rolling to higher thickness reductions resulted in a significant improvement in hardness and tensile strength as compared to peak-aged samples. Artificial peak-ageing before cold-rolling did not have a significant effect on the properties after cold-rolling. Enhancement of properties was comparable to the more complex severe plastic deformation process of cryo-rolling followed by warm-rolling. Cold-rolling could be used as a simpler and effective method to enhance mechanical properties of Al6061. No significant difference was found in the tensile strength between rolling and transverse directions.

The process of laser engineered net shaping (LENSTM) is an additive manufacturing technique that employs the coaxial flow of metallic powders with a high-power laser to form a melt pool and the subsequent deposition of the specimen on a substrate. Although research done over the past decade on the LENSTM processing of alloys of steel, titanium, nickel and other metallic materials typically reports superior mechanical properties in as-deposited specimens, when compared to the bulk material, there is anisotropy in the mechanical properties of the melt deposit. The current study involves the development of a numerical model of the LENSTM process, using the principles of computational fluid dynamics (CFD), and the subsequent prediction of the volume fraction of equiaxed grains to predict process parameters required for the deposition of workpieces with isotropy in their properties. The numerical simulation is carried out on ANSYS-Fluent, whose data on thermal gradient are used to determine the volume fraction of the equiaxed grains present in the deposited specimen. This study has been validated against earlier efforts on the experimental studies of LENSTM for alloys of nickel. Besides being applicable to the wider family of metals and alloys, the results of this study will also facilitate effective process design to improve both product quality and productivity.

Human ingenuity will play an ever-important role in this century and into the foreseeable future. This is because of phenomena such as globalization and climate-change that stress the need for more innovative output from developed countries. Such a picture has made it necessary to develop reliable models for quantifying innovations. The huge momentum behind the need for quantifying innovations is brought out by the research efforts of the Organization for Economic Cooperation and Development (OECD) and the United-States (US) government, which are at the forefront of the modeling activities required for this task. This effort describes some approaches, and the resulting models, for scoring individual innovations. Most of these approaches quantify innovations by considering their ensuing societal impact. In the course of this process, numerous variables have been identified that might have a significant influence from a scoring perspective. This work is the first portion of a research effort that addresses the theoretical background needed for quantifying innovations. The empirical results will follow up in a later work. © 2010 Imperial College Press.

In recent years, frugal products of the grassroots and advanced types are being widely used due to their sustainable nature and also affordability. However, despite the origins of frugality at grassroots level, grassroots innovations continue to be fabricated in an ad hoc manner that precludes application of science and are thus susceptible to premature failure. This work advocates the use of scientific principles for developing frugal products in general with emphasis on classical and new design methodologies that are rooted in science to save resources, and hence lower costs, while aiming for robust product functionality. This paper sheds light on the importance of the safety factor in frugal designs and the need, from here onwards, of a factor of frugality for the systematic realization of both grassroots and advanced frugal products. In particular, adoption of the factor of frugality, that was developed recently, has been supported in this effort with a numerical example to display the effectiveness of applying science for designing from scratch frugal products that are both streamlined and robust in their functionality.