Multiscale Design for Solid Freeform Fabrication

One of the advantages of solid freeform fabrication is the ability to fabricate complex structures on multiple scales, from the macroscale features of an overall part to the mesoscale topology of its internal architecture and even the microstructure or composition of the constituent material. This manufacturing freedom poses the challenge of designing across these scales, especially when a part with designed mesostructure is part of a larger system with changing requirements that propagate across scales. A setbased multiscale design method is presented for coordinating design across scales and reducing iterative redesign of SFF parts and their mesostructures. The method is applied to design a miniature unmanned aerial vehicle system. The system is decomposed into disciplinary subsystems and constituent parts, including wings with honeycomb mesostructures that are topologically tailored for stiffness and strength and fabricated with selective laser sintering. The application illustrates how the design of freeform parts can be coordinated more efficiently with the design of parent systems.Mechanical Engineerin

The Faithful Scribe: A Story of Islam, Pakistan, Family, and War

A journalist explores his family’s history to reveal the hybrid cultural and political landscape of Pakistan, the world’s first Islamic democracy. Shahan Mufti’s family history, which he can trace back fourteen hundred years to the inner circle of the prophet Muhammad, offers an enlightened perspective on the mystifying history of Pakistan. Mufti uses the stories of his ancestors, many of whom served as judges and jurists in Muslim sharia courts of South Asia for many centuries, to reveal the deepest roots—real and imagined—of Islamic civilization in Pakistan. More than a personal history, The Faithful Scribe captures the larger story of the world’s first Islamic democracy, and explains how the state that once promised to bridge Islam and the West is now threatening to crumble under historical and political pressure, and why Pakistan’s destiny matters to us all.https://scholarship.richmond.edu/bookshelf/1252/thumbnail.jp

Reducing the effects that cumulative maternal allostatic load poses on mother-infant interactions through mindfulness based family therapy in African American women

This proposed research project will use a mindfulness based intervention, namely, the Mindfulness-Based Childbirth and Parenting (MBCP) program that has been shown to have significantly reduced the stress and anxiety that mothers associate with pregnancy, parturition and postnatal care. Therefore, the present research study aims to use the MBCP model within the framework of family therapy in order to determine if such intervention is successful for reducing the effects of cumulative allostatic load on mother-infant interactions in primiparous mothers. Furthermore, if there is a reduction in the effects of the allostatic load on the mother, then it is expected that this should lead to a more healthy relationship between the mother and the infant, in addition to creating a secure attachment between them. Older African American women who are pregnant for the first time were found to be the most vulnerable to the negative effects of high allostatic load and thus, out of any other social, ethnic and racial group, they will gain the most out of the mindfulness based family therapy sessions if the therapy is found to be as successful as is being hypothesized

Ultrasonic Spot Welding of Thin Walled Fibre-Reinforced Thermoplastics

Das Ultraschall-Punktschweißen von faserverstärkten thermoplastischen Kunststoffen hat in der letzten Zeit bei Forschern in der Luftfahrt- und Automobilindustrie großes Interesse hervorgerufen. Es bietet eine effiziente Lösung zum Verbinden großer thermoplastischer Verbundbauteile durch Punktschweißen mit einem hohen Automatisierungsgrad. In der vorliegenden Arbeit wurde eine neue Technik zum Fokussieren der Ultraschallschwingungsenergie an der gewünschten Fügestelle zwischen zwei Fügepartnern aus thermoplastischen Verbundlaminaten untersucht. Bei diesem untersuchten Verfahren waren keine zusätzlichen Energierichtungsgeber zwischen den Fügepartnern erforderlich, um die Vibrationsenergie zu fokussieren. Es wurde festgestellt, dass es durch Schweißen der Laminate zwischen einer Sonotrode und einem Amboss möglich war, eine lokalisierte Wärme durch Reibung zu erzeugen in dem die Sonotrode eine größere Kontaktfläche mit dem Laminat als mit dem Amboss aufwies. In der Anfangsphase des Schweißens wurden die Grenzflächenschichten durch die reibungsverursachte Erwärmung abgeschwächt. Folglich zentrierte sich die zyklische Verformung in diesen abgeschwächten Grenzflächen. Die Annahme des Vorhandenseins der Reibung und ihres Einflusses auf die Wärmeerzeugung wurde mittels mechanischer FEM-Analyse untersucht. Die mikroskopische Analyse des Schweißpunktes lieferte schließlich den Beweis für die Schmelzauslösung an einem Ring um den Schweißpunkt und das anschließende Punktwachstum. Um die räumliche Verteilung der Temperatur und ihre zeitliche Entwicklung in der Schweißzone während des Ultraschallschweißprozesses besser zu verstehen, wurde das thermische Problem numerisch modelliert. Zur Verifizierung der mathematischen Modelle wurden die berechneten Zeitverläufe der Temperatur im Schweißpunktzentrum mit den experimentell ermittelten Werten unter vergleichbaren Bedingungen gegenübergestellt. Es wurde festgestellt, dass nach einer bestimmten Schweißzeit die Temperatur im Schweißzentrum plötzlich anstieg und das Polymer an der Schweißstelle überhitzt und die Zersetzung begann. Es wurde beobachtet, dass der Zeitverlauf der verbrauchten Leistungskurve durch das Schweißgerät einem ähnlichen Muster folgte, wie der Zeitverlauf der Temperatur in der Schweißpunktmitte. Basierend auf dieser Beobachtung wurde ein Steuerungssystem entwickelt. Die zeitliche Ableitung der Schweißleistung wurde in Echtzeit überwacht. Sobald ein kritischer Wert überschritten wurde, wurde die Ultraschallschwingungsamplitude aktiv durch einen Mikrocontroller eingestellt. Bei diesem Ansatz wurde die Temperatur im Schweißpunkt indirekt gesteuert, um während der gesamten Schweißdauer in einem optimalen Bereich zu bleiben. Die Ergebnisse des gesteuerten Schweißprozesses wurden mittels Temperaturmessungen und Computertomographie bewertet. Aus der Studie wurde der Schluss gezogen, dass das leistungsgesteuerte Ultraschall-Punktschweißverfahren eine effiziente und stabile Methode zum automatischen Verbinden von faserverstärkten thermoplastischen Teilen ist.:1 Introduction 1.1 Motivation 1.2 State of the Art 1.3 Statement of the Theses and Methods 2 Theoretical Background 2.1 Ultrasonic Welder 2.1.1 Ultrasonic Stack 2.1.2 Working Principle of the Ultrasonic Welder 2.2 Viscoelasticity 2.2.1 Viscoelasticity of Continuous Fibre-Reinforced Laminates 2.2.2 Viscoelastic Heating of CFRTP during the DUS Welding 2.3 Frictional heating at the Weld Interface during the DUS Welding 2.4 Fusion Mechanism during the USW 2.4.1 Contact of the Matrix at the Weld Interface 2.4.2 Healing of the Weld Interface through Autohesion 3 Experimental Analysis of the DUS Process 3.1 Experimental Setup 3.2 Experimental Procedure, Results and Discussions 3.2.1 Weld Progress and Formation Analysis 3.2.2 The Influence of the Amplitude and Static Force on the DUS 3.2.3 Computed Tomography Analysis of the DUS Welded Spots 3.2.4 Influence of the Weld Parameters on the Weld Force at Break 3.2.5 Influence of the Main Process Variables on the Weld Strength 4 Process Modelling and Simulation 4.1 Dynamic Mechanical 3D Finite Element Analysis 4.1.1 Woven Fabric Laminate Models 4.1.2 Laminate Properties and Meshing 4.1.3 FEM Analysis Procedure 4.1.4 Results of the Dynamic Analysis 4.2 Numerical Analysis of the Temperature Temporal and Spatial Development 4.2.1 The Numerical Method 4.2.2 Matrix Loss Modulus Calculation at the Welding Frequency 4.2.3 Model Validation 4.2.4 Analysis of the Spatial and Temporal development of the Temperature 4.2.5 Influence of Uncontrollable Factors on the DUS Process 5 Logical Control Method and Industrialisation 5.1 Process Controlling Hypothesis 5.2 Control System and Instruments 5.3 Experimental Procedure for Analysing the Control System 5.4 Analysis of the Controlled DUS Process 5.5 Control System Validation and Industrialisation 5.6 Automation of the Ultrasonic Spot Welding Process 6 Summary and Outlook 6.1 Conclusions 6.2 Outlook References AppendixThe ultrasonic spot welding of fibre-reinforced thermoplastic composites has recently received strong interest among researchers mainly in the fields of aerospace and automotive industries. It offers an efficient solution to join large thermoplastic composite parts through the spot welding approach with a high level of automation. In this study, a new technique for focusing the ultrasonic vibration energy at the desired spot between two mating thermoplastic composite laminates was investigated. In this method, no additional energy directing protrusions between the weldments were required to focus the vibration energy. It was found that by welding the laminates amid an ultrasonic sonotrode and an anvil in which the prior had a larger contact surface with the laminate as the latter, it was possible to generate a localised frictional heating. In the initial phase of the welding, the frictional heating softened the interfacial layers and thus caused the focusing of the strain energy in the weld spot centre. The assumption for the presence of the friction and its influence on the heat generation was investigated by means of finite element method analysis. Microscopic analysis of the weld spot delivered the proof for the melt initiation at a ring around the weld spot and subsequent inwards growth of the weld spot. In order to gain a better understanding of the temperature spatial distribution and its temporal development in the weld zone during the ultrasonic welding process, the thermal problem was analysed using the explicit finite difference method. The mathematical model was verified through a comparison between the calculated temperature curves and the experimentally obtained counterparts. It was found that after a certain weld duration the temperature in the weld centre underwent a sudden increase and caused the overheating and decomposition of the polymer in the weld spot. It was observed that the time trace of the consumed power curve by the welder followed a similar pattern as the time trace of the temperature in the weld spot centre. Based on this observation, a control system was developed accordingly. The time derivative of the weld power was monitored in real time and as soon as it exceeded a critical value, the ultrasonic vibration amplitude was actively adjusted through a microcontroller. In this approach, the temperature in the weld spot was indirectly controlled to remain within an adequate range throughout the welding duration. The results of the controlled welding process were evaluated by means of temperature measurements and computed tomography scans. It was concluded from the study that the power-controlled differential ultrasonic spot welding process could be an efficient method to fusion bond the fibre-reinforced thermoplastic parts in an automated manner.:1 Introduction 1.1 Motivation 1.2 State of the Art 1.3 Statement of the Theses and Methods 2 Theoretical Background 2.1 Ultrasonic Welder 2.1.1 Ultrasonic Stack 2.1.2 Working Principle of the Ultrasonic Welder 2.2 Viscoelasticity 2.2.1 Viscoelasticity of Continuous Fibre-Reinforced Laminates 2.2.2 Viscoelastic Heating of CFRTP during the DUS Welding 2.3 Frictional heating at the Weld Interface during the DUS Welding 2.4 Fusion Mechanism during the USW 2.4.1 Contact of the Matrix at the Weld Interface 2.4.2 Healing of the Weld Interface through Autohesion 3 Experimental Analysis of the DUS Process 3.1 Experimental Setup 3.2 Experimental Procedure, Results and Discussions 3.2.1 Weld Progress and Formation Analysis 3.2.2 The Influence of the Amplitude and Static Force on the DUS 3.2.3 Computed Tomography Analysis of the DUS Welded Spots 3.2.4 Influence of the Weld Parameters on the Weld Force at Break 3.2.5 Influence of the Main Process Variables on the Weld Strength 4 Process Modelling and Simulation 4.1 Dynamic Mechanical 3D Finite Element Analysis 4.1.1 Woven Fabric Laminate Models 4.1.2 Laminate Properties and Meshing 4.1.3 FEM Analysis Procedure 4.1.4 Results of the Dynamic Analysis 4.2 Numerical Analysis of the Temperature Temporal and Spatial Development 4.2.1 The Numerical Method 4.2.2 Matrix Loss Modulus Calculation at the Welding Frequency 4.2.3 Model Validation 4.2.4 Analysis of the Spatial and Temporal development of the Temperature 4.2.5 Influence of Uncontrollable Factors on the DUS Process 5 Logical Control Method and Industrialisation 5.1 Process Controlling Hypothesis 5.2 Control System and Instruments 5.3 Experimental Procedure for Analysing the Control System 5.4 Analysis of the Controlled DUS Process 5.5 Control System Validation and Industrialisation 5.6 Automation of the Ultrasonic Spot Welding Process 6 Summary and Outlook 6.1 Conclusions 6.2 Outlook References Appendi

Shahan Mufti - Edward C. and Mary S. Peple Library Lecture

Professor Shahan Mufti, Associate Professor of Journalism, is the author of The Faithful Scribe: A Story of Islam, Pakistan, Family, and War, published in 2013 by Other Press. The Faithful Scribe is deeply relevant to the world and to our campus today and the book was chosen as the 2017-2018 “One Book” for the university campus. On February 18, 2018, Professor Mufti delivered the university\u27s Edward C. and Mary S. Peple Library Lecture for the One Book, One Richmond Program culminating event. The lecture text is available by using the above download button

Identifying Landscape-Level Trends In Prairie Songbirds With Fragmented Habitats

Grassland songbirds are experiencing significant population declines due to habitat loss and degradation. This study investigated the relationship between landscape-level patterns and prairie-level patterns in presence/absence, richness, and diversity for seven individual species, the total grassland songbird community, and three community subgroups. Overall, grassland songbirds did respond to landscape-level variables, although the strength of the relationship and the variables involved differed by species and functional group