No description available.

With increasing fuel costs and the current drive to reduce greenhouse gas emissions and fuel consumption, a need to reduce vehicle weight is apparent. Weight reduction can be achieved by replacing conventionally stamped structural members with hydroformed parts. The weight reduction can be further enhanced by reducing the thickness of the hydroformed members through the use of advanced high strength steel (AHSS). A primary limitation in hydroforming AHSS, is the limited ductility or formability of these materials. This limitation becomes acute in multi-stage forming operations in which strain path changes become large making it difficult to predict formability. Thus, the focus of the current work is to study the effects of pre-bending on the subsequent hydroformability of Dual-Phase DP600 steel tubes. As part of this effort, the effect of key bending and hydroforming process parameters, bending boost and hydroforming end-feed, have been studied in a parametric fashion. <br /><br /> Multi-step pre-bending and hydroforming experiments were performed on 76. 2 mm (3. 0") OD tubes with a wall-thickness of 1. 85mm (DP600). Experiments were also performed on 1. 74mm Interstitial Free (IF) steel tube, which provided a low strength, high formability baseline material for comparison purposes. A fully instrumented servo-hydraulic mandrel-rotary draw tube bender was used in the pre-bending experiments in which various levels of boost were applied. The results showed that increased boost reduced the major (tensile) strain and thinning at the outside of the bend. At the inside of the bend, the compressive minor strain became larger and thickening increased. <br /><br /> Hydroforming of the straight and pre-bent tubes was conducted using various levels of load-control end-feed (EF). For both straight and pre-bend tube hydroforming, an increase in hydroforming EF resulted in increased burst pressure and corner-fill expansion (CFE). The effect of bending boost on CFE was also measured. For a given hydroforming EF case, a tube bent with greater boost achieved a higher burst pressure and consequently a greater CFE which increased the hydroformability of the material. Pre-bending was shown to consume a considerable amount of the formability of the tube in the hydroforming experiments. For the same EF case, the pre-bent tubes could only achieve a fraction of the straight tube CFE at burst. <br /><br /> The pre-bending and hydroforming experiments were complimented by finite element simulation in the hope of providing additional insight into these processes. The finite element (FE) models were able to accurately predict the strain and thickness changes imposed during pre-bending. The models were able to accurately predict the CFE, EF displacement, and strain and thickness distributions after hydroforming. <br /><br /> The extended stress-based forming limit curve (XSFLC) failure criterion was applied to predict failure (onset of necking) during hydroforming, which was measured as the burst pressure in the experiments. For straight tube hydroforming, the XSFLC predicted the correct failure pressure versus hydroforming EF load trend, but over predicted the failure pressures. In pre-bend hydroforming, the models were able to capture the effect of bending boost and hydroforming EF on the hydroformability of the tubes. The XSFLC was able to capture the drop in formability for bending versus straight tube hydroforming, but was unable to capture the failure pressure versus hydroforming EF load trend or magnitude. Further work is required to make the XSFLC applicable to straight and pre-bend hydroforming.

With increasing fuel costs and the current drive to reduce greenhouse gas emissions and fuel consumption, a need to reduce vehicle weight is apparent. Weight reduction can be achieved by replacing conventionally stamped structural members with hydroformed parts. The weight reduction can be further enhanced by reducing the thickness of the hydroformed members through the use of advanced high strength steel (AHSS). A primary limitation in hydroforming AHSS, is the limited ductility or formability of these materials. This limitation becomes acute in multi-stage forming operations in which strain path changes become large making it difficult to predict formability. Thus, the focus of the current work is to study the effects of pre-bending on the subsequent hydroformability of Dual-Phase DP600 steel tubes. As part of this effort, the effect of key bending and hydroforming process parameters, bending boost and hydroforming end-feed, have been studied in a parametric fashion. <br /><br /> Multi-step pre-bending and hydroforming experiments were performed on 76. 2 mm (3. 0") OD tubes with a wall-thickness of 1. 85mm (DP600). Experiments were also performed on 1. 74mm Interstitial Free (IF) steel tube, which provided a low strength, high formability baseline material for comparison purposes. A fully instrumented servo-hydraulic mandrel-rotary draw tube bender was used in the pre-bending experiments in which various levels of boost were applied. The results showed that increased boost reduced the major (tensile) strain and thinning at the outside of the bend. At the inside of the bend, the compressive minor strain became larger and thickening increased. <br /><br /> Hydroforming of the straight and pre-bent tubes was conducted using various levels of load-control end-feed (EF). For both straight and pre-bend tube hydroforming, an increase in hydroforming EF resulted in increased burst pressure and corner-fill expansion (CFE). The effect of bending boost on CFE was also measured. For a given hydroforming EF case, a tube bent with greater boost achieved a higher burst pressure and consequently a greater CFE which increased the hydroformability of the material. Pre-bending was shown to consume a considerable amount of the formability of the tube in the hydroforming experiments. For the same EF case, the pre-bent tubes could only achieve a fraction of the straight tube CFE at burst. <br /><br /> The pre-bending and hydroforming experiments were complimented by finite element simulation in the hope of providing additional insight into these processes. The finite element (FE) models were able to accurately predict the strain and thickness changes imposed during pre-bending. The models were able to accurately predict the CFE, EF displacement, and strain and thickness distributions after hydroforming. <br /><br /> The extended stress-based forming limit curve (XSFLC) failure criterion was applied to predict failure (onset of necking) during hydroforming, which was measured as the burst pressure in the experiments. For straight tube hydroforming, the XSFLC predicted the correct failure pressure versus hydroforming EF load trend, but over predicted the failure pressures. In pre-bend hydroforming, the models were able to capture the effect of bending boost and hydroforming EF on the hydroformability of the tubes. The XSFLC was able to capture the drop in formability for bending versus straight tube hydroforming, but was unable to capture the failure pressure versus hydroforming EF load trend or magnitude. Further work is required to make the XSFLC applicable to straight and pre-bend hydroforming.

Unternehmen stehen zunehmend vor der Herausforderung, dem drohenden Wissensverlust durch demografischen Wandel und Mitarbeiterabgang zu begegnen. In Zeiten voranschreitender Digitalisierung gilt es, große Datenmengen beherrschbar und nutzbar zu machen, mit dem Ziel, einerseits die Ressourceneffizienz innerhalb des Unternehmens zu erhöhen und anderseits den Kunden zusätzliche Dienstleistungen anbieten zu können. Vor dem Hintergrund, ein effizientes Qualitätsmanagement und eine vorausschauende Instandhaltung mit ein und demselben System zu realisieren, sind zunächst technologische Kennzahlen und die Prozessführung zu bestimmen. Im Bereich der intelligenten Instandhaltung ist es jedoch nicht immer möglich, Fehlerzustände von physischen Anlagen im Serienbetrieb als Datensatz abzufassen. Das bewusste Zulassen von Fehlern unter realen Produktionsbedingungen könnte zu fatalen Ausfällen bis hin zur Zerstörung der Anlage führen. Auch das gezielte Erzeugen von Fehlern unter stark kontrollierten Bedingungen kann zeitaufwendig, kostenintensiv oder sogar undurchführbar sein.

Companies are increasingly challenged by the impending loss of knowledge due to demographic change and employee loss. In times of advancing digitalization, it is important to make large datasets accessible and usable, aiming at increasing resource efficiency within the company on the one hand and being able to offer customers additional services on the other. Given the background of implementing efficient quality management and predictive maintenance with the same system, technological key figures and process control must first be determined. In the field of intelligent maintenance, however, it is not always possible to record error states of physical systems in series operation as a data set. Deliberately allowing faults to occur under real production conditions could lead to fatal failures or even the destruction of the system. The targeted generation of faults under highly controlled conditions can also be timeconsuming, cost-intensive, or even impractical.

No description available.

Die Anwendungsmöglichkeiten und Potenziale des temperierten Innenhochdruck-Umformens mit flüssigen Wirkmedien (T-IHU) von Rohren aus verschiedenen Magnesium- und Aluminiumknetlegierungen werden in der vorliegenden Arbeit aufgezeigt. Neben der Werkstoff- und Halbzeugcharakterisierung, der Auslegung von temperierten Innenhochdruck-Umformanlagen und –werkzeugen, den Thermografiemessungen am Halbzeug unter Realbedingungen und der Verifizierung der Simulationsergebnisse des T-IHU-Werkzeuges war der inhaltliche Schwerpunkt die systematische experimentelle Bestimmung der maximalen Umfangserweiterung ∆u_max in Anhängigkeit von der Umformtemperatur ϑ_u, dem Werkstoff und der Wanddicke s₀ im Temperaturbereich von 22°C bis 300°C an drei Versuchsgeometrien T-Stück, Zylinder und Quader bei Innendrücken bis 800 bar. Neben dem Einfluss der Prozessparameter, der Werkstoff- und Halbzeugeigenschaften und der Ausgangswanddicke wurde der signifikante Einfluss der Umformtemperatur und der Umformgeometrie auf die erreichbaren Umfangserweiterungen herausgearbeitet und systematisch dargestellt. Es wurden Umfangsdehnungen von bis zu 120 % (bei ϑ_u = 300°C) erzielt. Die experimentelle Bestimmung der minimal auszuformenden Bauteilaußenradien erfolgte unter Anwendung der statistischen Versuchsplanung. Aus den Regressionsgleichungen wurde eine neue Berechnungsgleichung für den maximalen Innendruck p_imax generiert. Durch die Verifikation dieser Gleichung konnte die hohe Genauigkeit bei der Vorausberechnung des erforderlichen Innendruckes bei einem vorgegebenen minimalen Bauteilaußenradius R_min in Abhängigkeit von der Zugfestigkeit R_m als f (Umformtemperatur) und der Wanddicke s₀ nachgewiesen werden. Die Auslegung der T-IHU-Werkzeug- und Anlagentechnik kann damit wesentlich genauer er­folgen. Durch die Bauteilanalysen nach dem T-IHU-Prozess konnten die hohe Maß- und Formgenauigkeit und die hohe und gleichmäßigere Oberflächengüte nachgewiesen werden. Trotz der beginnenden dynamischen Rekristallisation lag bei allen Versuchswerkstoffen eine Erhöhung der Werkstofffestigkeit in der Umformzone vor. Bei den Untersuchungen bzgl. des T-IHU des Realbauteiles „PKW-Querträger vorn“ konnten die Kenntnisse der Grundlagenuntersuchungen auf ein komplex geformtes Realteil übertragen und erweitert werden. Es zeigte sich, dass der Einsatz von T-IHU-Magnesiumbauteilen ein erhebliches Potenzial für weitere Gewichtsreduzierungen von Leichtbaukonstruktionen besitzt. / This paper presents the potential applications of temperature-supported hydroforming of various magnesium and aluminium alloy tubes using active liquid media. It includes details of material and semi-finished product characterisation, the design of temperature-supported hydroforming equipment and tools, thermography measurements on the semi-finished product under real conditions and verification of simulation results for the temperature-supported hydroforming tool. The main focus, however, was the systematic, experimental approach to determining the maximum increase in perimeter ∆u_max as a function of the forming temperature ϑ_u, the material and the wall thickness s₀ in the temperature range 22°C to 300°C for three trial geometries (T‑piece, cylinder and cuboid) at internal pressures of up to 800 bar. In addition to studying the effect of process parameters, material properties, semi-finished product characteristics and initial wall thickness, the paper also presents the finding that forming temperature and forming geometry have a significant impact on achievable increases in perimeter. Perimeter expansions of up to 120 % were attained (at ϑ_u = 300°C). Statistically designed experiments were used to determine the minimum component outside-radii to undergo the forming process. A new equation for calculating the maximum internal pressure p_imax was generated from regression equations. By verifying this equation, it was possible to demonstrate the high level of accuracy in predicting the internal pressure required for a given minimum component outside-radius R_min as a function of the tensile strength R_m as f(forming temperature) and of the wall thickness s₀. This means that the temperature-supported hydroforming tool and system equipment can be designed far more accurately. Component analyses after the temperature-supported hydroforming process demonstrated the high level of dimensional and geometrical accuracy and the high quality and more consistent surface finish. Despite the onset of dynamic re-crystallisation, the strength of the material was increased in the forming zone in all the materials tested. The knowledge gained from researching the fundamental principles was applied to a real component with a complex shape in studies of temperature-supported hydroforming of the "front car cross-member", which provided further useful insights. It was found that the use of temperature-supported hydroforming magnesium components has considerable potential for further weight reduction in lightweight constructions.

Die Anwendungsmöglichkeiten und Potenziale des temperierten Innenhochdruck-Umformens mit flüssigen Wirkmedien (T-IHU) von Rohren aus verschiedenen Magnesium- und Aluminiumknetlegierungen werden in der vorliegenden Arbeit aufgezeigt. Neben der Werkstoff- und Halbzeugcharakterisierung, der Auslegung von temperierten Innenhochdruck-Umformanlagen und –werkzeugen, den Thermografiemessungen am Halbzeug unter Realbedingungen und der Verifizierung der Simulationsergebnisse des T-IHU-Werkzeuges war der inhaltliche Schwerpunkt die systematische experimentelle Bestimmung der maximalen Umfangserweiterung ∆u_max in Anhängigkeit von der Umformtemperatur ϑ_u, dem Werkstoff und der Wanddicke s₀ im Temperaturbereich von 22°C bis 300°C an drei Versuchsgeometrien T-Stück, Zylinder und Quader bei Innendrücken bis 800 bar. Neben dem Einfluss der Prozessparameter, der Werkstoff- und Halbzeugeigenschaften und der Ausgangswanddicke wurde der signifikante Einfluss der Umformtemperatur und der Umformgeometrie auf die erreichbaren Umfangserweiterungen herausgearbeitet und systematisch dargestellt. Es wurden Umfangsdehnungen von bis zu 120 % (bei ϑ_u = 300°C) erzielt. Die experimentelle Bestimmung der minimal auszuformenden Bauteilaußenradien erfolgte unter Anwendung der statistischen Versuchsplanung. Aus den Regressionsgleichungen wurde eine neue Berechnungsgleichung für den maximalen Innendruck p_imax generiert. Durch die Verifikation dieser Gleichung konnte die hohe Genauigkeit bei der Vorausberechnung des erforderlichen Innendruckes bei einem vorgegebenen minimalen Bauteilaußenradius R_min in Abhängigkeit von der Zugfestigkeit R_m als f (Umformtemperatur) und der Wanddicke s₀ nachgewiesen werden. Die Auslegung der T-IHU-Werkzeug- und Anlagentechnik kann damit wesentlich genauer er­folgen. Durch die Bauteilanalysen nach dem T-IHU-Prozess konnten die hohe Maß- und Formgenauigkeit und die hohe und gleichmäßigere Oberflächengüte nachgewiesen werden. Trotz der beginnenden dynamischen Rekristallisation lag bei allen Versuchswerkstoffen eine Erhöhung der Werkstofffestigkeit in der Umformzone vor. Bei den Untersuchungen bzgl. des T-IHU des Realbauteiles „PKW-Querträger vorn“ konnten die Kenntnisse der Grundlagenuntersuchungen auf ein komplex geformtes Realteil übertragen und erweitert werden. Es zeigte sich, dass der Einsatz von T-IHU-Magnesiumbauteilen ein erhebliches Potenzial für weitere Gewichtsreduzierungen von Leichtbaukonstruktionen besitzt. / This paper presents the potential applications of temperature-supported hydroforming of various magnesium and aluminium alloy tubes using active liquid media. It includes details of material and semi-finished product characterisation, the design of temperature-supported hydroforming equipment and tools, thermography measurements on the semi-finished product under real conditions and verification of simulation results for the temperature-supported hydroforming tool. The main focus, however, was the systematic, experimental approach to determining the maximum increase in perimeter ∆u_max as a function of the forming temperature ϑ_u, the material and the wall thickness s₀ in the temperature range 22°C to 300°C for three trial geometries (T‑piece, cylinder and cuboid) at internal pressures of up to 800 bar. In addition to studying the effect of process parameters, material properties, semi-finished product characteristics and initial wall thickness, the paper also presents the finding that forming temperature and forming geometry have a significant impact on achievable increases in perimeter. Perimeter expansions of up to 120 % were attained (at ϑ_u = 300°C). Statistically designed experiments were used to determine the minimum component outside-radii to undergo the forming process. A new equation for calculating the maximum internal pressure p_imax was generated from regression equations. By verifying this equation, it was possible to demonstrate the high level of accuracy in predicting the internal pressure required for a given minimum component outside-radius R_min as a function of the tensile strength R_m as f(forming temperature) and of the wall thickness s₀. This means that the temperature-supported hydroforming tool and system equipment can be designed far more accurately. Component analyses after the temperature-supported hydroforming process demonstrated the high level of dimensional and geometrical accuracy and the high quality and more consistent surface finish. Despite the onset of dynamic re-crystallisation, the strength of the material was increased in the forming zone in all the materials tested. The knowledge gained from researching the fundamental principles was applied to a real component with a complex shape in studies of temperature-supported hydroforming of the "front car cross-member", which provided further useful insights. It was found that the use of temperature-supported hydroforming magnesium components has considerable potential for further weight reduction in lightweight constructions.