<p> Tool life during the precision stamping of stainless steel sheet (AISI 301) has been studied with particular emphasis on reduction in the punch diameter and part hole size due to tool wear. Two analytical models for predicting tool life in terms of number of quality parts that could be stamped between two re-grindings have been proposed using a combination of Archard's wear model and punching force. The proposed tool life models have been verified by experiment trials with a round M2 punch and die. The trials were carried out on a precision progressive die in an industrial environment.</p> <p> The first tool life model calculates the pierced hole diameter variation for a given tool from sheet material properties and gives an estimation of number of parts that could be stamped for a given tolerance on a hole size. The second tool life model calculates number of parts with respect to the allowed burr height. Both of the proposed models are derived using sheet material properties such as sheet thickness, strength coefficient (K), strain hardening index (n) and material elongation (A); process parameters such as die clearance and friction coefficient; punch characteristics such as normalized wear rate, punch diameter and punch edge radius. Finite element analysis was also employed to simulate the hole piercing process to predict burr height. The results from the proposed tool life models, FE modeling and the experiments are in good agreement.</p> / Thesis / Master of Applied Science (MASc)

The presented doctoral thesis is focused on environmental impact assessment of basic engineering materials used in a production machine construction. Ecological profile of the machine itself develops already in the phase of its design. It is not only about the choice of future machine parameters and materials that it is built from, but also about technologies used for its manufacture and operation conditions of the finished machine (consumption of energy and service fluids). The thesis occupies in detail with environmental impact analysis of the production machine design from the viewpoint of material production that mentioned machine consists of. The output from the performed analysis is methodology for evaluating of machine design from the viewpoint of greenhouse gas emissions. Created methodology enables evaluating of machine ecological profile and its possible adjustments even during pre-production stage. In the first part of the thesis the analysis of current legislation in the field of fighting against climate changes, reducing of products energy consumption and increasing of production machines energy efficiency is presented. Also in this part of the thesis description of methods that were used to achieve thesis goals is stated. Furthermore analysis of production machine as a system of structural components that fulfil the certain functions and description of used basic engineering materials are presented. The second part of the thesis is devoted to environmental impact analysis of the production machine design process. There the design process and environmental impact of machine design are described. This is followed by description of production machine life cycle and detailed analysis of undesirable substances emissions emitted during pre-production phases of machine life cycle (i.e. during the raw materials extraction and materials production). From this analysis the particular constituents’ pre-production phases which are sources of undesirable substances emissions (e.g. greenhouse gas emissions) were derived. The thesis also includes analysis of these constituents’ life cycles and description of electric power generation as a basic constituent of any phase of product life cycle. In this part of the thesis calculations of particular fuel type’s amounts that is required to produce 1 MWh of electric power and carbon dioxide amount produced during electric power generation are presented. The third part of the thesis contains created models of manufacturing processes of basic engineering materials and calculations of related emissions of selected greenhouse gases. The practical output from this part of the thesis is methodology that enables environmental impact assessment of machine design from the viewpoint of engineering materials used in its construction.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In a move towards cleaner and more sustainable energy systems, hydrogen as an energy carrier and hydrogen fuel cells as energy converters are receiving increasing global attention. Considering the vital role that platinum plays in the operation of hydrogen fuels cells, South Africa stands to gain enormously as the world’s leading platinum group metals supplier. Therefore, in order to benefit across the whole value chain, it is imperative to develop the capability to manufacture hydrogen fuel cell stacks locally. This project addresses this imperative, in part, by building a framework to evaluate the manufacturing performance of one of the more costly components of the hydrogen fuel cell stack. More specifically, this project builds a cost evaluation model (or cost model) for the manufacture of bipolar plates using micro milling. In essence, the model characterises manufacturing cost (and time) as a function of relevant inputs. The model endeavours to be flexible in accommodating relevant contributing cost drivers such as tool life and manufacturing time. Moreover, the model lays the groundwork, from a micro milling perspective, for a comparison of different manufacturing methods for bipolar plates. The approach taken in building the cost model is a fundamental one, owing to the lack of historical cost data for this particular process. As such, manufacturing knowledge and experimentation are used to build the cost model in a structured way. The process followed in building the cost model begins with the formulation of the cost components by reviewing relevant examples from literature. Thereafter, two main cost drivers are comprehensively addressed. Tool life is characterised experimentally as a function of cutting parameters and manufacturing time is characterised as a function of relevant inputs. The work is then synthesized into a coherent cost model. Following the completion of the cost model, analysis is done to find the near-optimal combination of machine cutting parameters. Further, analysis is done to quantify the sensitivity of manufacturing cost to design changes and production volumes. This attempts to demonstrate how typical managerial issues can be addressed using the cost model format. The value of this work must be seen in terms of its practical contribution. That is, its contribution to the development of the capability to manufacture hydrogen fuel cells locally. By understanding the effect of relevant input factors on manufacturing cost, ‘upstream’ design and development activities can be integrated with ‘downstream’ manufacturing activities. Therefore, this project supports the development of manufacturing capability by providing a mechanism to control cost throughout the process. / AFRIKAANSE OPSOMMING: In die soeke na skoner, meer volhoubare energie bronne word die fokus op waterstof, as energie draer, en waterstof brandstofselle, as energie omskakelaars, al meer verskerp. Deur die sleutelrol van platinum in die werking van waterstof brandstofselle in ag te neem, word Suid-Afrika, as die wêreld se grootste platinum verskaffer, in `n uitstekende posisie geplaas om voordeel te trek uit hierdie geleentheid. Om dus as land voordeel te trek uit die proses in geheel, is dit van kardinale belang om die vermoë te ontwikkel om waterstof brandstofsel stapels op eie bodem te vervaardig. Hierdie projek adresseer gedeeltelik hierdie noodsaaklikheid, deur `n raamwerk te bou wat die vervaardigingsoptrede van een van die meer duursame komponente van die waterstof brandstofsel stapel evalueer. Meer spesifiek, bou hierdie projek `n koste evaluerings model (of koste model) vir die vervaardiging van bipolêre plate deur die gebruik van mikro-masjienering. In wese kenmerk hierdie model vervaardigings kostes (en tyd) as `n funksie van relevante insette. Hierdie model poog om buigsaam te wees met die in ag neming van relevante bydraende kostedrywers soos buitelleeftyd en vervaardigingstyd. Daarbenewens lê hierdie model die grondwerk, vanuit `n mikro masjienerings oogpunt, vir die vergelyking van verskillende vervaardingings metodes vir bipolêre plate. Die benadering wat gevolg word in die bou van die koste model is fundamenteel as gevolg van die gebrek van historiese data vir hierdie spesifieke proses. As sodanig word vervaardigings kennis en eksperimentering gebruik om die koste model in `n gestruktueerde wyse te bou. Die proses gevolg in die bou van die koste model begin met die formulering van die koste komponente deur die hersiening van relevante voorbeelde vanuit die literatuur. Daarna word twee hoof koste drywers deeglik geadresseer. Buitelleeftyd word ekperimenteel gekenmerk as funksie van masjieneringsparameters en vervaardigingstyd word gekenmerk as `n funksie van relevante insette. Die werk word dan gesintetiseer in `n samehangende koste model. Wat volg op die voltooiing van die koste model is `n analise om die optimale kombinasie masjieneringsparameters te vind. Daaropvolgens word analises gedoen om die sensitiwiteit van vervaardigingskoste onderworpe aan ontwerpsveranderings en produksie volumes te kwantisfiseer. Dit poog om te demostreer hoe tipiese bestuursproblem geadresseer kan word deur die koste model formaat te gebruik. Die waarde van hierdie werk moet in die lig van die praktiese bydrae daarvan gesien word, menende, die bydrae tot die ontwikkeling van die vermoë om waterstof brandstofselle in Suid-Afrika te vervaardig. Deur die effek van relevante inset faktore op vervaardigingskoste te verstaan, kan ‘stroom-op’ ontwerp en ontwikkelings aktiwiteite geïntegreer word met ‘stroom-af’ vervaardigings aktiwiteite. Dus, hierdie projek ondersteun die ontwikkeling van vervaardigingsvermoëns deur `n meganisme te voorsien om kostes oor die omvang van die proses te beheer.

Titanium is one of fourth most abundant structural metal in earths soil. It is in a composition with other elements, forming titanium alloys. These alloys are used in many different areas, such as medical, energy and sports, but is most commonly used in aerospace applications. Titanium alloys have different solid phases, α, α+β and β depending on temperature and the amount of α and β-stabilizers.When machining titanium alloys, one of the most important factors to control is the temperature in the cutting zone. The built-up heat in the cutting edge of the tool, are connected to titanium alloys low thermal conductivity and high heat capacity, which means that the alloy has low heat conduction from the cutting zone. The temperature is strongly depending on the cutting speed, which is the relative speed difference between the cutting tool and the workpiece. Many studies and research work have been conducted surrounding this fact, focusing on the physical and chemical quantities, to model tool wear progression and how this affects the tool life and the metal removal. These models are often implemented and analyzed in finite element software providing detailed but time-consuming solutions.The focus for this work have been on developing a suitable tool life expectancy model, using design of experiments in combination with metamodeling to establish a model connecting cutting parameters and measured responses in terms of tool life, from a conducted milling experiment. This models where supposed to provide a platform for customer recommendation and cutting data optimization to secure reliable machining operations. The study was limited to focus on the common α+β titanium alloy 6Al-4V. The outcome and conclusion for this study, is that the tool life is strongly connected to the choice of cutting speed and the radial width of cut and that these parameters can be predicted by the two models that have been develop in this project. The models ensure the highest possible metal removal rate, to selected parameters.

The thesis is focused on the characteristic of coating methods and their division, on the morphology of defects and cause of wear in coated cutting tools of sintered carbides. The experimental part is focused on a comparing cutting performance testing of indexable cutting inserts coated with nanocrystaline composite TiAlSiN at the longitudinal turning.

The presented diploma thesis is devided into two parts. The theoretical part deals with types of milling, the choice of the cutters, choice of material of exchangeable cutting plates and also with types of wear and their classification. The second part of the thesis deals with experiments where the power load of the tool was measured. The observed data were processed and graphs of power load were created by software. Conclusions are based on these graphs.

The presented doctoral thesis is focused on environmental impact assessment of basic engineering materials used in a production machine construction. Ecological profile of the machine itself develops already in the phase of its design. It is not only about the choice of future machine parameters and materials that it is built from, but also about technologies used for its manufacture and operation conditions of the finished machine (consumption of energy and service fluids). The thesis occupies in detail with environmental impact analysis of the production machine design from the viewpoint of material production that mentioned machine consists of. The output from the performed analysis is methodology for evaluating of machine design from the viewpoint of greenhouse gas emissions. Created methodology enables evaluating of machine ecological profile and its possible adjustments even during pre-production stage. In the first part of the thesis the analysis of current legislation in the field of fighting against climate changes, reducing of products energy consumption and increasing of production machines energy efficiency is presented. Also in this part of the thesis description of methods that were used to achieve thesis goals is stated. Furthermore analysis of production machine as a system of structural components that fulfil the certain functions and description of used basic engineering materials are presented. The second part of the thesis is devoted to environmental impact analysis of the production machine design process. There the design process and environmental impact of machine design are described. This is followed by description of production machine life cycle and detailed analysis of undesirable substances emissions emitted during pre-production phases of machine life cycle (i.e. during the raw materials extraction and materials production). From this analysis the particular constituents’ pre-production phases which are sources of undesirable substances emissions (e.g. greenhouse gas emissions) were derived. The thesis also includes analysis of these constituents’ life cycles and description of electric power generation as a basic constituent of any phase of product life cycle. In this part of the thesis calculations of particular fuel type’s amounts that is required to produce 1 MWh of electric power and carbon dioxide amount produced during electric power generation are presented. The third part of the thesis contains created models of manufacturing processes of basic engineering materials and calculations of related emissions of selected greenhouse gases. The practical output from this part of the thesis is methodology that enables environmental impact assessment of machine design from the viewpoint of engineering materials used in its construction.

No description available.

In der Dissertation wurde der Stand der Technik zum Fertigungsverfahren Druckgießen mit dem Fokus auf die Druckgießwerkzeuge recherchiert und strukturiert aufbereitet. Der Stand der Technik mündet in der Systematik zur Optimierung des Druckgießens. Darin wurde die Problematik ganzheitlich aufgearbeitet, konkretisiert und wesentliche Handlungsfelder, wie das Temperierkonzept, der Werkstoff sowie die Auslegung, herausgearbeitet. Das Handlungsfeld Temperierkonzept wurde fokussiert und daraus das Konzept des mehrteiligenWerkzeuges erarbeitet. DiesesWerkzeugkonzept ermöglicht durch seinen Aufbau eine Maximierung der Wärmeübertragungsfläche, eine Reduzierung des Abstandes der Temperierung zum Gussteil und eine Erhöhung des Wärmeübergangskoeffizienten. Der mehrteilige Aufbau wurde in einem Versuchswerkzeug für das Druckgießen umgesetzt, sukzessive ausgelegt und virtuell abgesichert. Abschließend zeigte die thermische Simulation des Prozess Druckgießen ein Potential zur Reduzierung der Zykluszeit von 12,9s (14%) mit dem mehrteiligen Werkzeug auf. Im Dauerbetrieb konnte prozesssicher, reproduzierbar und dauerhaft eine Zykluszeitreduzierung um 20,5s (23%) nachgewiesen werden.

In der Dissertation wurde der Stand der Technik zum Fertigungsverfahren Druckgießen mit dem Fokus auf die Druckgießwerkzeuge recherchiert und strukturiert aufbereitet. Der Stand der Technik mündet in der Systematik zur Optimierung des Druckgießens. Darin wurde die Problematik ganzheitlich aufgearbeitet, konkretisiert und wesentliche Handlungsfelder, wie das Temperierkonzept, der Werkstoff sowie die Auslegung, herausgearbeitet. Das Handlungsfeld Temperierkonzept wurde fokussiert und daraus das Konzept des mehrteiligen Werkzeuges erarbeitet. Dieses Werkzeugkonzept ermöglicht durch seinen Aufbau eine Maximierung der Wärmeübertragungsfläche, eine Reduzierung des Abstandes der Temperierung zum Gussteil und eine Erhöhung des Wärmeübergangskoeffizienten. Der mehrteilige Aufbau wurde in einem Versuchswerkzeug für das Druckgießen umgesetzt, sukzessive ausgelegt und virtuell abgesichert. Abschließend zeigte die thermische Simulation des Prozess Druckgießen ein Potential zur Reduzierung der Zykluszeit von 12,9s (14%) mit dem mehrteiligen Werkzeug auf. Im Dauerbetrieb konnte prozesssicher, reproduzierbar und dauerhaft eine Zykluszeitreduzierung um 20,5s (23%) nachgewiesen werden.