Timothy G. Gutowski

An Environmental Analysis of Machining

This paper presents a system-level environmental analysis of machining. The analysis presented here considers not only the environmental impact of the material removal process itself, but also the impact of associated processes such as material preparation and cutting fluid preparation. This larger system view results in a more complete assessment of machining. Energy analyses show that the energy requirements of actual material removal can be quite small when compared to the total energy associated with machine tool operation. Also, depending on the energy intensity of the materials being machined, the energy of material production can, in some cases, far exceed the energy required for machine tool operation.Copyright

The consolidation of laminate composites

A general mathematical model wich allows for three dimensional flow, and one dimen sional consolidation of the composite, is developed. The model assumes that the fibers make up a deformable, nonlinear elastic network. The resin flow is modelled using Darcys Law for an anisotropic porous medium, with a resin of time varying viscosity. The general case is then solved for two important molding situations: 1) Compression Mold ing, and 2) Bleeder Ply Molding.

Remanufacturing and energy savings.

Remanufactured products that can substitute for new products are generally claimed to save energy. These claims are made from studies that look mainly at the differences in materials production and manufacturing. However, when the use phase is included, the situation can change radically. In this Article, 25 case studies for eight different product categories were studied, including: (1) furniture, (2) clothing, (3) computers, (4) electric motors, (5) tires, (6) appliances, (7) engines, and (8) toner cartridges. For most of these products, the use phase energy dominates that for materials production and manufacturing combined. As a result, small changes in use phase efficiency can overwhelm the claimed savings from materials production and manufacturing. These use phase energy changes are primarily due to efficiency improvements in new products, and efficiency degradation in remanufactured products. For those products with no, or an unchanging, use phase energy requirement, remanufacturing can save energy. For the 25 cases, we found that 8 cases clearly saved energy, 6 did not, and 11 were too close to call. In some cases, we could examine how the energy savings potential of remanufacturing has changed over time. Specifically, during times of significant improvements in energy efficiency, remanufacturing would often not save energy. A general design trend seems to be to add power to a previously unpowered product, and then to improve on the energy efficiency of the product over time. These trends tend to undermine the energy savings potential of remanufacturing.

Propagation of Ground Vibration: A Review

A review of the current state of the art of ground vibration propagation is presented herein. First the theoretical models of vibration attenuation are reviewed and then measurement techniques are discussed. Finally, measurement and theory are combined into predictive models, whose validity is discussed.

An Environmental Analysis of Injection Molding

This environmental analysis of injection molding highlights a few important points. The choice of injection molding machine type (hydraulic, hybrid or all-electric) has a substantial impact on the specific energy consumption (SEC). The SEC values for hydraulic, hybrid and all-electric machines analyzed are 19.0, 13.2 and 12.6 MJ/kg respectively (including auxiliaries, compounding and the inefficiency of the electric grid). For hydraulic and hybrid machines SEC seems to exhibit a decreasing behavior with increasing throughput. This derives from spreading fixed energy costs over more kilograms of polymer as throughput increases. For all-electric machines SEC is constant with throughput. When the polymer production stage is included in the analysis, the energy consumption values increase up to 100 MJ/kg. The overall injection molding energy consumption in the U.S. in a yearly basis amounts to 2.06 times 108 GJ. This value is of similar magnitude to the overall U.S. energy consumption for sand casting, and to the entire electricity production of some developed countries

Life Cycle Analysis of Conventional Manufacturing Techniques: Sand Casting

Conventional manufacturing techniques have not been subject to much scrutiny by industrial ecologists to date. Many newer techniques and products draw more attention as they rise quickly from research to global scales, amplifying their environmental consequences. Despite the presence of new technologies and increased overseas production, casting activity continues to have a strong presence in the US, and represents a stable component in the national economy. Data from the US government, US industry groups, and UK mass balance profiles facilitate an understanding of sand casting and comparison across manufacturing processes. The figures in the US and UK are similar in terms of diversity of metals (where the US is 72%, 13%, 10% and the UK 76%, 13%, 8% for iron, aluminum, and steel, respectively), energy per ton of saleable cast metal (10.1 and 9.3 million Btu/ton in the US and UK), and overall emissions, with notable similarities in benzene and particulate emissions. One notable discrepancy is in sand use, where the US sends to waste 0.5 tons of sand per ton of cast metal, whereas the UK sends 0.25 tons to landfill.Copyright

Thermodynamics and the destruction of resources

This book is a unique, multidisciplinary effort to apply rigorous thermodynamics fundamentals to problems of sustainability, energy, and resource uses. Applying thermodynamic thinking to problems of sustainable behavior is a significant advantage in bringing order to ill-defined questions with a great variety of proposed solutions, some of which are more destructive than the original problem. The chapters are pitched at a level accessible to advanced undergraduate and graduate students in courses on sustainability, sustainable engineering, industrial ecology, sustainable manufacturing, and green engineering. The timeliness of the topic and the urgent need for solutions make this book attractive to general readers as well as specialist researchers. Top international figures from many disciplines, including engineers, ecologists, economists, physicists, chemists, policy experts, and industrial ecologists, make up the impressive list of contributors.

Material efficiency: providing material services with less material production

Material efficiency, as discussed in this Meeting Issue, entails the pursuit of the technical strategies, business models, consumer preferences and policy instruments that would lead to a substantial reduction in the production of high-volume energy-intensive materials required to deliver human well-being. This paper, which introduces a Discussion Meeting Issue on the topic of material efficiency, aims to give an overview of current thinking on the topic, spanning environmental, engineering, economics, sociology and policy issues. The motivations for material efficiency include reducing energy demand, reducing the emissions and other environmental impacts of industry, and increasing national resource security. There are many technical strategies that might bring it about, and these could mainly be implemented today if preferred by customers or producers. However, current economic structures favour the substitution of material for labour, and consumer preferences for material consumption appear to continue even beyond the point at which increased consumption provides any increase in well-being. Therefore, policy will be required to stimulate material efficiency. A theoretically ideal policy measure, such as a carbon price, would internalize the externality of emissions associated with material production, and thus motivate change directly. However, implementation of such a measure has proved elusive, and instead the adjustment of existing government purchasing policies or existing regulations— for instance to do with building design, planning or vehicle standards—is likely to have a more immediate effect.

The energy required to produce materials: constraints on energy-intensity improvements, parameters of demand

In this paper, we review the energy requirements to make materials on a global scale by focusing on the five construction materials that dominate energy used in material production: steel, cement, paper, plastics and aluminium. We then estimate the possibility of reducing absolute material production energy by half, while doubling production from the present to 2050. The goal therefore is a 75 per cent reduction in energy intensity. Four technology-based strategies are investigated, regardless of cost: (i) widespread application of best available technology (BAT), (ii) BAT to cutting-edge technologies, (iii) aggressive recycling and finally, and (iv) significant improvements in recycling technologies. Taken together, these aggressive strategies could produce impressive gains, of the order of a 50–56 per cent reduction in energy intensity, but this is still short of our goal of a 75 per cent reduction. Ultimately, we face fundamental thermodynamic as well as practical constraints on our ability to improve the energy intensity of material production. A strategy to reduce demand by providing material services with less material (called ‘material efficiency’) is outlined as an approach to solving this dilemma.

Development of a theoretical cost model for advanced composite fabrication

Abstract This paper outlines the development of a theoretical approach to the estimation of processing time for the fabrication of advanced composite parts. The model, termed ‘first-order model’, assumes that all subprocess steps can be modelled as having first-order dynamics. The steps are then linearized and summed according to their ‘extensive’ variables. Part complexity is handled using an information theoretic approach. The result for hand lay-up is a simple linear equation which compares favourably with experiments and with other very detailed cost estimation models. The model is very general, and appears applicable to all additive (composites) as well as subtractive (machining) processes.