Additive manufacturing can bring several advantages in tooling applications especially hot working tooling as high pressure die casting. Printing of conformal cooling channels can lead to improved cooling and faster solidification, which, in turn, can possibly result in better quality of the cast part. However, few studies on advantages of additive manufactured tools in high pressure die casting are published.The aim of this study was to investigate and quantify the effect of conformal cooling on microstructure and mechanical properties of high pressure die cast aluminum alloy. Two tools each consisting of two die inserts were produced with and without conformal channels using additive manufacturing. Both tools were used in die casting of aluminum alloy. Aluminum specimens were then characterized microstructurally in light optical microscope for secondary arm spacing measurements and subjected to tensile and hardness testing. Cooling behavior of different inserts was studied with a thermal camera and by monitoring the temperature change of cooling oil during casting. Surface roughness of die inserts was measured with profilometer before and after casting.Thermal imaging of temperature as a function of time and temperature change of oil during casting cycle indicated that conformal insert had faster cooling and lower temperature compared to conventional insert. However, thermal imaging of temperature after each shot in a certain point of time showed higher maximum and minimum temperature on conformal die surface but no significant difference in normalized temperature gradient compared to the conventional insert.The average secondary dendrite arm spacing values were fairly similar for samples from conventional and conformal inserts, while more specimens from conventional insert demonstrated coarser structure. Slower cooling in conventional insert could result in the coarser secondary dendrite arm spacing.Tensile strength and hardness testing revealed no significant difference in mechanical properties of the specimens cast in conventional and conformal die inserts. However, reduced deviations in hardness was observed for samples cast with conformal insert. This is in agreement with secondary dendrite arm spacing measurements indicating improved cooling with conformal insert.Surface roughness measurement showed small wear of the inserts. More castings are needed to observe a possible difference in wear between the conventional and conformal inserts.Small observed differences in cooling rate and secondary arm spacing did not result in evident difference in mechanical properties of the aluminum alloy but the variation in properties were reduced for samples cast with conformal cooling. Future work may include more accurate measurement of cooling behavior with a thermocouple printed into the die insert, casting of thicker specimen for porosity evaluation and fatigue testing and longer casting series to evaluate the influence of conformal cooling on tool wear.

No description available.

Am Anfang des Entwicklungsprozesses eines Gussbauteils für die Automobilbranche steht klassischerweise die konstruktive Ausarbeitung und die Auslegung auf Zielgrößen, wie Festigkeit, Steifigkeit bzw. die Erfüllung der Crashlasten. Im nächsten Entwicklungsschritt wird, oftmals in Zusammenarbeit mit externen Lieferanten, das Werkzeugkonzept entwickelt und die Herstellbarkeit mit Hilfe von Gießsimulationen abgesichert. Bei der Fertigung verursachen streuende Prozessgrößen, wie etwa Geschwindigkeits- oder Temperaturniveaus, Schwankungen in der Leistungsfähigkeit des Endprodukts (z. B. lokale Bruchdehnung oder Zugfestigkeit). Maßnahmen zur Erhöhung der Prozessstabilität und zur Reduktion des Verschleißes konzentrieren sich oftmals auf die erfahrungsbasierte Verbesserung des Fertigungsprozesses und Anpassungen des Anguss- und Überlaufsystems. Größere Änderungen der Bauteilgeometrie sind häufig aus zeitlichen Gründen nicht mehr möglich. Das Ziel dieser Arbeit ist es daher, optimierte modularisierte Grundgeometrien, wie Rippen oder Umlenkungen, mit Hilfe von numerischen Formoptimierungen zu entwickeln, um diese schon von Anfang an in der Bauteilentwicklung zu berücksichtigen. Als Zielfunktionen dienen strömungs- und strukturmechanische Kenngrößen, um einerseits verschleißfördernde Mechanismen und füllungsbedingte Defekte zu reduzieren und andererseits die Beanspruchbarkeit zu erhöhen. Bei den Untersuchungen wird zusätzlich die Robustheit des Ergebnisses analysiert, um Verbesserungspotenziale auch bei streuenden Randbedingungen realisieren zu können. / The virtual development process of an automotive casting part usually begins with classical design tasks and analyses of material strength, stiffness and crash load cases. In the next step, often in cooperation with external suppliers, the tooling concept is developed and casting simulations are used to ensure manufacturability. During manufacturing there is a scatter in process parameters, such as flow velocity or temperature levels, which in turn cause a scatter in the performance of the final product (e.g. local elongation at fracture or ultimate tensile strength). Means to increase process stability and yield are often limited to knowledge-based improvements of the manufacturing process parameters and adaptations of the gating and overflow system. Major changes to the part geometry are usually no longer possible due to project time constraints. Therefore it is the goal of this thesis to optimize modularized basic geometries, like ribs or bends, by using numerical shape optimizations and employ them right from the beginning of the part development process. For the objective functions of the optimizations the disciplines of fluid dynamic filling and the resulting structural behaviour are considered. In addition, the resulting shape is analyzed with regards to robustness towards scatter in manufacturing operating conditions. By using these new modularized geometries the overall robustness of the final product is expected to be increased.

While Aluminium has lots of unique properties and is seen as a material of the future, its production and manufacturing has significant environmental impacts. For complex and dimensional shapes casting remains the main manufacturing method and in this study the environmental pressure of different casting techniques is compared. A screening LCA is conducted to determine the environmental impacts of plaster mould castings in a case study at the Ventana Hackås AB foundry in Mid Sweden. The findings are compared to models of sand, pressure die and lost wax castings, based on literature datasets. The most relevant factors for the environmental performance are identified as the production of the aluminium alloy and the amount and source of energy. For plaster mould castings additionally the plaster consumption is significant, while lost wax castings are dominated by the mould production and general processes. Under similar circumstances a relatively similar performance was found for all casting techniques except the lost wax process, which is at least 3 times more emission intensive. Of the remaining techniques pressure die castings performed the best and plaster mould castings the worst, but different sources of uncertainties have been identified in this comparison. In addition a carbon footprint interface is created based on these findings, to enable specific comparisons of different casting method setups. Customizable variables allow the adaptation of three scenarios to real world conditions. As the main influencing factors the aluminium alloy, source of electricity and casting technique have been identified. / <p>2018-10-10</p>

Am Anfang des Entwicklungsprozesses eines Gussbauteils für die Automobilbranche steht klassischerweise die konstruktive Ausarbeitung und die Auslegung auf Zielgrößen, wie Festigkeit, Steifigkeit bzw. die Erfüllung der Crashlasten. Im nächsten Entwicklungsschritt wird, oftmals in Zusammenarbeit mit externen Lieferanten, das Werkzeugkonzept entwickelt und die Herstellbarkeit mit Hilfe von Gießsimulationen abgesichert. Bei der Fertigung verursachen streuende Prozessgrößen, wie etwa Geschwindigkeits- oder Temperaturniveaus, Schwankungen in der Leistungsfähigkeit des Endprodukts (z. B. lokale Bruchdehnung oder Zugfestigkeit). Maßnahmen zur Erhöhung der Prozessstabilität und zur Reduktion des Verschleißes konzentrieren sich oftmals auf die erfahrungsbasierte Verbesserung des Fertigungsprozesses und Anpassungen des Anguss- und Überlaufsystems. Größere Änderungen der Bauteilgeometrie sind häufig aus zeitlichen Gründen nicht mehr möglich. Das Ziel dieser Arbeit ist es daher, optimierte modularisierte Grundgeometrien, wie Rippen oder Umlenkungen, mit Hilfe von numerischen Formoptimierungen zu entwickeln, um diese schon von Anfang an in der Bauteilentwicklung zu berücksichtigen. Als Zielfunktionen dienen strömungs- und strukturmechanische Kenngrößen, um einerseits verschleißfördernde Mechanismen und füllungsbedingte Defekte zu reduzieren und andererseits die Beanspruchbarkeit zu erhöhen. Bei den Untersuchungen wird zusätzlich die Robustheit des Ergebnisses analysiert, um Verbesserungspotenziale auch bei streuenden Randbedingungen realisieren zu können.:1 Einleitung 1.1 Motivation und Problemstellung 1.2 Zielsetzung und Vorgehensweise 1.3 Stand von Wissenschaft und Technik 2 Grundlagen 2.1 Leichtmetallgussbauteile im Automobil 2.2 Geometrische Gestaltung von Gussbauteilen 2.3 Modellierung gießtechnischer Fertigungsverfahren 2.4 Strukturmechanische Modellierung von Gussbauteilen 2.5 Numerische Optimierung 3 Modellaufbau und -analyse 3.1 Geometrische Entwurfsmodelle 3.2 Strömungsmodellbildung zur Abbildung der Fertigungseinflüsse 3.3 Strukturberechnungsmodell unter Berücksichtigung materieller Defekte 4 Optimierung der Umlenkung 4.1 Optimierungsstrategie und -prozesskette 4.2 Zielfunktionen 4.3 Optimierung mit Entwurfsmodell I 4.4 Optimierung mit Entwurfsmodell II 4.5 Diskussion der Ergebnisse 5 Optimierung der Rippe 5.1 Optimierungsstrategie und -prozesskette 5.2 Ziel- und Restriktionsfunktionen 5.3 Multidisziplinäre Optimierung 5.4 Diskussion der Ergebnisse 6 Zusammenfassung 7 Ausblick Anhang Abkürzungs- und Symbolverzeichnis Literatur- und Quellenverzeichnis / The virtual development process of an automotive casting part usually begins with classical design tasks and analyses of material strength, stiffness and crash load cases. In the next step, often in cooperation with external suppliers, the tooling concept is developed and casting simulations are used to ensure manufacturability. During manufacturing there is a scatter in process parameters, such as flow velocity or temperature levels, which in turn cause a scatter in the performance of the final product (e.g. local elongation at fracture or ultimate tensile strength). Means to increase process stability and yield are often limited to knowledge-based improvements of the manufacturing process parameters and adaptations of the gating and overflow system. Major changes to the part geometry are usually no longer possible due to project time constraints. Therefore it is the goal of this thesis to optimize modularized basic geometries, like ribs or bends, by using numerical shape optimizations and employ them right from the beginning of the part development process. For the objective functions of the optimizations the disciplines of fluid dynamic filling and the resulting structural behaviour are considered. In addition, the resulting shape is analyzed with regards to robustness towards scatter in manufacturing operating conditions. By using these new modularized geometries the overall robustness of the final product is expected to be increased.:1 Einleitung 1.1 Motivation und Problemstellung 1.2 Zielsetzung und Vorgehensweise 1.3 Stand von Wissenschaft und Technik 2 Grundlagen 2.1 Leichtmetallgussbauteile im Automobil 2.2 Geometrische Gestaltung von Gussbauteilen 2.3 Modellierung gießtechnischer Fertigungsverfahren 2.4 Strukturmechanische Modellierung von Gussbauteilen 2.5 Numerische Optimierung 3 Modellaufbau und -analyse 3.1 Geometrische Entwurfsmodelle 3.2 Strömungsmodellbildung zur Abbildung der Fertigungseinflüsse 3.3 Strukturberechnungsmodell unter Berücksichtigung materieller Defekte 4 Optimierung der Umlenkung 4.1 Optimierungsstrategie und -prozesskette 4.2 Zielfunktionen 4.3 Optimierung mit Entwurfsmodell I 4.4 Optimierung mit Entwurfsmodell II 4.5 Diskussion der Ergebnisse 5 Optimierung der Rippe 5.1 Optimierungsstrategie und -prozesskette 5.2 Ziel- und Restriktionsfunktionen 5.3 Multidisziplinäre Optimierung 5.4 Diskussion der Ergebnisse 6 Zusammenfassung 7 Ausblick Anhang Abkürzungs- und Symbolverzeichnis Literatur- und Quellenverzeichnis

<p>Proučavane su koroziona postojanost i tendencija lepljenja različitih<br />materijala u kontaktu sa tečnom Al&ndash;Si&ndash;Cu legurom. Ispitivanjem su<br />obuhvaćeni čelik za rad na toplo, plazma nitrirani čelik i dupleks<br />slojevi sa CrN, TiAlN, TiAlSiN i CrAlN prevlakama, različitog nivoa<br />površinske hrapavosti. Za ispitivanja pomenutih fenomena<br />primenjena je metoda izvlačenja, koja je unapređena kako bi se povećale<br />njena tačnost i verodostojnost simulacije procesa livenja. Korozioni<br />efekti su pojačani tako što su uzorci osim kratkog kontakta sa odlivkom<br />zadržavani i u dužim periodima u kontaktu sa tečnom legurom (5 i 20<br />min). Uprkos opštim stavovima, za ispitivane materijale je<br />ustanovljeno da su sile izvlačenja uzoraka iz Al&ndash;Si&ndash;Cu odlivaka<br />nezavisne od njihovog hemijskog sastava. Uticaj hrapavosti je izražen<br />kod uzoraka sa prevlakama kod kojih pri smanjenju hrapavosti dolazi do<br />povećanja sile izvlačenja. Sve ispitane prevlake su sklone mehaničkom<br />lepljenju Al&ndash;Si&ndash;Cu legure za svoje površine, ali sa aspekta korozije u<br />tečnom metalu značajno prevazilaze performanse čelika i plazma<br />nitriranog sloja. Duži kontakt livene legure sa površinama prevlaka<br />uzrokovao je niže vrednosti sila izvlačenja, što je posledica<br />oksidacije površina prevlaka. Ustanovljeno je da su ispitivane<br />prevlake inertne ka tečnoj leguri aluminijuma. Međutim, dolazi do<br />oksidacije i korozije materijala podloge kroz greške rasta koje su<br />prisutne u prevlakama. Stečena znanja o identifikovanim<br />mehanizmima habanja i propadanja zaštitnih slojeva prevlaka<br />poslužiće daljem razvoju dupleks slojeva namenjenih za zaštitu alata<br />za livenje pod pritiskom.</p> / <p>Corrosion resistance and soldering tendency of different materials in molten<br />Al&ndash;Si&ndash;Cu alloy were studied. Hot-working tool steel, plasma nitrided steel and<br />duplex layers with CrN, TiAlN, TiAlSiN and CrAlN top coatings, which were<br />produced to various degree of surface roughness, were covered by the study.<br />An ejection test was employed for investigation of the concerned phenomena.<br />The ejection test was improved in order to increase its accuracy and the<br />reliability of process simulation. Samples were examined in both short and<br />extended periods of contact (5 and 20 min) with liquid casting. Casting<br />solidification was extended in order to intensify the corrosion effects. Contrary<br />to common findings, it was found that the ejection force of the investigated<br />materials does not depend on their chemical composition. For the coated<br />samples, a pronounced dependence of the ejection force on the surface<br />roughness was found. The ejection force increases with decrease in surface<br />roughness. All investigated coatings are prone to mechanical soldering by Al&ndash;<br />Si&ndash;Cu alloy. Still, their corrosion resistance substantially exceeds the corrosion<br />resistance of steel and plasma nitrided layer. Longer exposure of coated<br />samples to cast alloy induced lower ejection forces, which is a consequence<br />of coatings oxidation. It was found that the investigated coatings are inert to<br />liquid aluminium. However, the underlying material undergoes oxidation and<br />corrosion through coating growth defects. The findings concerning the wear<br />mechanisms of protective layers support further development of duplex layers<br />intended for die casting tools protection.</p>