bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propensity for Fatigue Failure of the FCBGA UF-Substrate Interface After Prolonged Storage
Authors: Lall Pradeep , Choudhury Padmanava 
Published: November 2023

Abstract
Electronics in automotive applications may be exposed the thermal excursions owing to environmental temperature changes and power-on/off cycling. Temperatures may range from −40C to +200C depending on the location of electronics in the automotive underhood. Flip-chip Ball-Grid Arrays (FCBGAs) are finding applications for advanced driver assistance systems on the automotive platform. Failure of the chip-underfill interface or the substrate-underfill interface is often the precursor for the failure of the flip-chip solder joints. Depending on the power output of the FCBGA package — the top of the chip may have a thermal-interface material to form a low thermal-resistance connection to the lid of the package. Interface reliability under monotonic and repetitive loads after long durations of storage are thus needed for the assessment of the thermo-mechanical reliability of the FCBGA architecture in the automotive underhood environments. In this study UF-Substrate interface reliability has been investigated as a function of Paris’ Constants developed from the samples subjected to 4-point bend fatigue loading. The samples were tested till catastrophic failures, and the critical stress intensity factor (ΔK) was correlated with cycles to failure (da/dN). The slope and the intercept parameters were studied as a function of 4 months’ aging time and 2 temperatures (100°C and 150°C). The evolution of these constants shows the effect of sustained high-temperature operation on the fatigue reliability of 4 underfill interfaces. Several cycles to failure were measured to rank the underfills for future applications in field-deployed electronics.
Optimization of a Air-Cooled Heatsink for Immersion Cooling Application
Authors: Gupta Gautam , Nair Vivek , Pundla Sai Abhideep , Bansode Pratik , Suthar Rohit , Herring Joseph , Lamotte-Dawaghreh Jacob , Sivaraju Krishna Bhavana , Agonafer Dereje , Mynampati Poornima , Sweeney Mike 
Published: November 2023

Abstract
Data centers have started to adopt immersion cooling for more than just mainframes and supercomputers. Due to the inability of air cooling to cool down recent high-configured servers with higher Thermal Design Power, current thermal requirements in machine learning, AI, blockchain, 5G, edge computing, and high-frequency trading have resulted in a larger deployment of immersion cooling. Dielectric fluids are far more efficient at transferring heat than air. Immersion cooling promises to help address many of the challenges that come with air cooling systems, especially as computing densities increase. Immersion-cooled data centers are more expandable, quicker installation, more energy-efficient, allows for the cooling of almost all server components, save more money for enterprises, and are more robust overall. By eliminating active cooling components such as fans, immersion cooling enables a significantly higher density of computing capabilities. When utilizing immersion cooling for server hardware that is intended to be air-cooled, immersion-specific optimized heat sinks should be used. A heat sink is an important component for server cooling efficacy. This research conducts an optimization of heatsink for immersion-cooled servers to achieve the minimum case temperature possible utilizing multi-objective and multidesign variable optimization with pumping power as the constraint.
A high-density server of 3.76 kW was modeled on Ansys Icepak that consists of 2 CPUs and 8 GPUs with heatsink assemblies at their Thermal Design Power along with 32 Dual In-line Memory Modules. The optimization is conducted for Aluminum heat sinks by minimizing the pressure drop and thermal resistance as the objective functions whereas fin count, fin thickness, and heat sink height are chosen as the design variables in all CPUs, and GPUs heatsink assemblies. Optimization for the CPU and the GPU heatsink was done separately and then the optimized heatsinks were tested in an actual test setup of the server in ANSYS Icepak. The dielectric fluid for this numerical study is EC-110 and the cooling is carried out using forced convection. A Design of Experiment (DOE) is created based on the input range of design variables using a full-factorial approach to generate multiple design points. The effect of the design variables is analyzed on the objective functions to establish the parameters that have a greater impact on the performance of the optimized heatsink. The optimization study is done using Ansys OptiSLang where AMOP (Adaptive Metamodel of Optimal Prognosis) as the sampling method for design exploration. The results show total effect values of heat sinks geometric parameters to choose the best design point with the help of a Response Surface 2D and 3D plot for the individual heat sink assembly.
Polarization Curves, Package-Level Multiphysics Simulation of Cu85Al15 and Cu94Al6 WB Corrosion for Automotive and Rugged Environment Applications
Authors: Lall Pradeep , Jung Sungmo 
Published: November 2023

Abstract
Copper wire bonding has increasingly being preferred in place of the more expensive gold wire for chip-to-substrate or chip-to-leadframe interconnects. The copper wire has a higher propensity for corrosion, higher hardness, narrow process window, thinner intermetallics and a higher propensity for cratering owing to a highe splash. Electronics in automotive underhood applications may be routinely expected to function reliability for 10-years, 100K miles. There is lack of foundational data for the assessment of Cu-Al wirebond reliability under humidity and contaminants including Bromine and Chlorine. Exposure to high temperature has been shown to appearance of two new intermetallics Cu85Al15 and Cu94Al6 never studied before for their propensity for corrosion. In this paper, the Cu85Al15 and Cu94Al6 intermetallics have been methodically fabricated using an arc-melter. Polarization curves of the intermetallics have been measured versus operating temperature, annealing duration at 250C, and changes in the pH. For each use-case, the effect of open circuit corrosion current density, open circuit corrosion potential, anodic and cathodic slopes have been quantified. Corrosion rate has been computed for both the intermetallics. The experimental data has been used to formulate a Multiphysics model for the prediction of propensity for corrosion using the Butler-Volmer and Nernst Planck Equations.
Energy Analysis of Rear Door Heat Exchangers in Data Centers With Spatial Workload Distribution
Authors: Simon Vibin Shalom , Karajgikar Saket , Mulay Veerendra , Pundla Sai Abhideep , Sivaraju Krishna Bhavana , Gupta Gautam , Bansode Pratik , Agonafer Dereje 
Published: November 2023

Abstract
Data centers have complex environments that undergo constant changes due to fluctuations in IT load, commissioning and decommissioning of IT equipment, heterogeneous rack architectures and varying environmental conditions. These dynamic factors often pose challenges in effectively provisioning cooling systems, resulting in higher energy consumption. To address this issue, it is crucial to consider data center thermal heterogeneity when allocating workloads and controlling cooling, as it can impact operational efficiency. Computational Fluid Dynamics (CFD) models are used to simulate data center heterogeneity and analyze the impact of two different cooling mechanisms on operational efficiency. This research focuses on comparing the cooling based on facility water for Rear Door Heat Exchanger (RDHx) and conventional Computer Room Air Conditioning (CRAH) systems in two different data center configurations. Efficiency is measured in terms of ΔT across facility water. Higher ΔT will result in efficient operation of chillers. The actual chiller efficiency is not calculated as it would depend on local ambient conditions in which the chiller is operated.
The first data center model represents a typical enterpriselevel configuration where all servers and racks have homogeneous IT power. The second model represents a colocation facility where server/rack power configurations are randomly distributed. These models predict temperature variations at different locations based on IT workload and cooling parameters. Traditionally, CRAH configurations are selected based on total IT power consumption, rack power density, and required cooling capacity for the entire data center space. On the other hand, RDHx can be scaled based on individual rack power density, offering localized cooling advantages. Multiple workload distribution scenarios were simulated for both CRAH and RDHx-based data center models. The results showed that RDHx provides a uniform thermal profile across the data center, irrespective of server/rack power density or workload distribution. This characteristic reduces the risk of over- or under-provisioning racks when using RDHx. Operational efficiency is compared in terms of difference in supply and return temperature of facility water for CRAH and RDHx units based on spatial heat dissipation and workload distribution. RDHx demonstrated excellent cooling capabilities while maintaining a higher ΔT, resulting in reduced cooling energy consumption, operational carbon footprint (?), and water usage.
Numerical Study of a Piezoelectric Vibration Energy Harvester Without and With an Ortho-Planar Spring Using a Modified H-Shape Structure
Authors: Taufan Ibnu , Punch Jeff , Nico Valeria 
Published: November 2023

Abstract
The demand for low-power electronic devices in wireless sensor networks (WSNs) has been continuously increasing. Most WSNs rely on battery power, however, and batteries need replacement regularly, resulting in direct and indirect pollution to the environment. Because of its abundance in many environments, kinetic energy, in the form of ambient vibrations, could be used as alternative to batteries by using vibrational energy harvesting techniques. Piezoelectric materials are one of the most common form of transducers and, traditionally, piezoelectric vibrational energy harvesters (PVEHs) are based on a cantilever beam, with one or more piezoelectric layers. However, the drawbacks of such designs are single vibration mode and narrow frequency bandwidth.
In this paper, we propose a novel PVEH design based on a modified H-shape structure without and with an ortho-planar spring to solve the issues of single vibration mode and narrow frequency bandwidth. This structure comprises a double clamped beam, with four arms which act like cantilever beams. The centre of the structure is coupled with a compliant ortho-planar spring to create low natural frequency and multiple peaks in the frequency response. A proof mass is placed on the spring to induce high stresses in the structure.
A numerical model using finite element analysis (FEA) was developed using the solid mechanics, electrostatics, and electrical circuit modules in COMSOL Multiphysics to compare the output voltage and power of the modified H-shape structure without (baseline) and with an ortho-planar spring (design 1) in the x, y, z axes. The H-shape structure was made of polylactide (PLA) as a substrate. The configuration used six PZT-5H piezoelectric materials connected in parallel, a 17.78 kΩ load resistor, and 0.4 g (g = 9.81 m/s2) base excitation.
The results show that: (i) the first three modes of design 1 are 8.9, 15.6, and 17.2 Hz, while the baseline design’s modes are 11.8, 15.3, and 17.6 Hz; (ii) both of designs show a multi-modal response, and that design 1 has three peaks, while the baseline has two peaks in the frequency range (0–50 Hz) in the z axis; (iii) both designs can only harvest energy efficiently in the z axis; and (iv) the baseline design achieves maximum voltage and power values of 34.5 V and 33.5 mW respectively, whereas design 1 produces 31.3 V and 27.6 mW respectively in the z axis.
Aero-Structural Response of a Slitted Bistable Laminate
Authors: Boddapati Karthik , Boston D. Matthew , Rivas-Padilla Jose R. , Arrieta Andres F. 
Published: November 2023

Abstract
Compliant morphing structures have been explored in aircraft as potential alternatives to rigid hinge-based mechanisms because of their ability to undergo large deformations without complicated assemblies. The simple geometry, high strength-to-weight ratio, and selective stiffness of bistable composite laminates make them highly suitable for use in morphing structures. However, rectangular asymmetric laminates with one edge clamped lose their bistability at low aspect ratios (free edge length to clamped edge length). Introducing multiple slits parallel to the free edge of these laminates has previously been shown to enable natural curving, thereby preserving their bistability. In this work, we characterize the behavior of a slitted bistable laminate under aerodynamic loading. The laminate is mounted to a bluff body leading edge inside a wind tunnel. The lift and drag forces acting on the two stable states of the slitted laminate are measured at two different flow speeds of 10 m/s and 20 m/s, and angles of attack ranging from −10 degrees to +10 degrees. We compare these results to those of a conventional bistable laminate with the same geometry to understand how the addition of slits affects the associated aerodynamics.
In Situ Actuation of Shape Memory Alloy Using Focused Ultrasound
Authors: Chipana Aldo , Hill Jeffrey R. , Dillon Christopher R. 
Published: November 2023

Abstract
Nitinol (NiTi) shape memory alloy exhibits excellent characteristics for use in biomedical engineering. The material has excellent biocompatibility, corrosion resistance, and wear characteristics, which has increased its use in biomedical applications, including stents and guidewires. While NiTi is becoming more common in medical procedures, most of the use has relied on the superelasticity of the wire, rather than its hysteretic qualities. One reason for this is the difficulty in heating NiTi wire in situ, without damaging adjacent tissue. This research explores the use of focused ultrasound to noninvasively heat NiTi wire above its transition temperature. To demonstrate the memory effect, the wire is strained at low temperature, then placed between porcine muscle samples to mimic an in situ biological environment. Using focused ultrasound, the wire is heated until the NiTi actuates and its shape memory is recovered. Embedded thermocouples located close to the wire measure the local temperature. The study found that higher ultrasonic power resulted in (1) faster actuation of the Nitinol, (2) more complete Nitinol actuation, and (3) lower temperatures in the surrounding tissue with less thermal damage.
Experimental Study on Gradually Varying Thickness Patch for Elastic Wave Manipulation Using Piezo Disk Actuators
Authors: Park Hyun-Su , Hwang Dae-Hyun , Han Jae-Hung 
Published: November 2023

Abstract
In recent years, there have been several studies focused on manipulating elastic waves in thin plate structures to achieve shock reduction or energy harvesting, without being limited by frequency. An elastic patch is a promising method for such manipulation, as it can be easily applied to practical structures without compromising their stiffness or strength. Refraction of the bending wave is achieved by mismatching the effective stiffness between the host plate and the region where the patch is attached. In this study, we explored the characteristics of GVT (Gradually Varying Thickness) patches for elastic wave manipulation, modeling various types of patches (such as triangular wedge/pyramid and circular cone) and predicting wave paths using ray-tracing and density estimation algorithms. For experimental investigation, an out-of-plane vibration scanning system with a 2D auto-stage and an LDV (Laser Doppler Vibrometer) was built, and a 1-D array of 15 piezoelectric-disk actuators was attached to the host plate for generating bending waves. All the patches showed excellent performance for shock reduction in specific areas, and their propagation paths were compared with ray-tracing results. The proposed method has potential applications in protecting sensitive components from intensive shock or noise without any degradation of structural stiffness or strength.
Fabrication and Characterization of Flexible Matrix Composite Wafers
Authors: Hada Masaki , Philen Michael 
Published: November 2023

Abstract
Flexible Matrix Composites (FMCs) are high performance actuators that exhibit a high mechanical advantage when pressurized. These actuators rely on symmetric layers of carbon fiber surrounding a flexible rubber tube. When the fiber angle is less than 55 degrees with respect to the longitudinal axis, these actuators expand radially and contract in length when pressurized. When these actuators are coiled in a disk-shaped wafer, the radial volume change within the composite actuator can be utilized to create a compressive force through the thickness. By varying the actuation pressure, matrix material, fiber winding angle, and inner tubing diameter, the actuation and stiffness properties can be widely varied and suited to the desired application. This research aims to determine the impact on wafer performance by the variation of design parameters. It has been found that increasing the matrix material modulus will increase the overall stiffness of the wafer, while also increasing the maximum load that can be applied. Inversely, a lower modulus matrix will decrease the overall stiffness of the wafer, with the benefit of greater actuation volume. For each combination of fiber and matrix selection, there exists a stratum of pressures allowing for active stiffness and force management during use. From this comprehensive evaluation, a characterization of the wafer performance through experimentation will be reported.
Embedded Sensing and Localization of Pressure in Silicone Skin Using Sensors Printed From CNF/TPU Filament
Authors: Meier Joseph L. , Turnbull Steven A. , Hernandez Julio A. , Maynard Cole , Rodriguez David , Newell Brittany , Tallman Tyler N. 
Published: November 2023

Abstract
Additive manufacturing (AM) provides a near-infinite design space to create unique and custom components. Recent advances have enabled the development of novel self-sensing materials for fused filament fabrication (FFF) AM, which have potential applications in areas such as soft robotics, smart textiles, embedded structural sensing, and, among others, biomedicine. Sensing in these fields is often done using traditional strain sensors that have limited capability for large deformations and little-to-no customizability. Through the use of piezoresistive filaments, AM has the potential to create highly customizable, application-specific sensors. However, the widespread adoption of self-sensing filament has been constrained due to developmental challenges, such as low conductivity and inconsistent or highly variable electrical properties. To address these issues, in this work, we manufacture a modified thermoplastic polyurethane (TPU) filament with 10 wt.% carbon nanofiber (CNF) inclusions using a novel wet-mixing technique previously developed within our research group. This CNF/TPU filament is flexible and has consistent electrical properties. Building on the extensive use of self-sensing composites in soft robotic applications, the CNF/TPU filament was embedded into a soft silicone skin to demonstrate sensing and localization of pressure points applied to the skin via simple electrical measurements taken from the printed and embedded CNF/TPU sensors. These preliminary results highlight the incredible potential and far-reaching design space of AM-produced sensors.
An Integrated Audio-Tactile Interface Based on Dielectric Elastomer Actuators for User Interaction
Authors: Gratz-Kelly Sebastian , Holz Benedikt , Krüger Tim , Seelecke Stefan , Rizzello Gianluca , Motzki Paul , Moretti Giacomo 
Published: November 2023

Abstract
Due to their high actuation energy density, high stretchability and self-sensing capability, dielectric elastomer actuators (DEAs) and sensors are very attractive for the field of user interaction and communication. The possibility of using the same element to perform actuation (feedback) and sensing (user input detection), in particular, opens up possibilities towards highly integrated interaction elements.
Here, we present an integrated prototype of a DEA user interface that can produce different feedbacks (acoustic, vibrotactile) in response to a user’s touch. Touch detection is achieved by means of capacitive sensing, whereas multi-sensory actuation (tactile and acoustic feedbacks) is produced leveraging on the dynamic modal response of the DEA membrane, whose different vibration modes are used to produce linear actuation (used to convey vibrotactile stimulations) at low frequencies, and structural vibrations (for generating sound) at higher frequencies. The prototype includes an acoustic enclosure, compact sensing/control electronics, and a custom-built low-cost compact high voltage (HV) power amplifier.
We characterize the coupled system response (DEA + custom amplifier) in terms of linear actuation (in the range 0–180 Hz) and sound pressure output (in the range 500–2500 Hz) and compare results with those obtained with a commercially available HV bench power supply. The performance of the proposed system is comparable to that obtained with commercial electronics in terms of linear displacements and sound pressure level, while it introduces higher harmonic distortions in specific ranges of the acoustic response.
The concept and results presented here represent a step forward towards further integration and down-scaling of DEA user interfaces.
Hybrid Soft-Rigid Joint With Inherent Sensing and Actuation Capabilities Based on Rolled Dielectric Elastomers
Authors: Meyer Andreas , Schmidt Christian Johannes , Motzki Paul 
Published: November 2023

Abstract
Traditionally the tension structures are built by passive wires unable to give information about the state of the system or to excite an actuation from within. Using dielectric elastomers (DEs) to distribute tension forces, both can be achieved within the structure itself. DEs are thin silicone membranes that are printed with a flexible, conductive electrode on both sides, resulting in a capacitor with variable geometry. To integrate slim DEs that can not only be used as actuators and sensors but also assume the role of passive tension elements, the membrane is being rolled up to be used as a stiffer, centrical elastomer beam which is called a rolled dielectric elastomer (RDE). These smart elements are characterized by capacitance-displacement and force-displacement measurements. Especially the linearity of the sensor signal in relation to the applied stretch allows for a good displacement reconstruction, while this work concentrates on the first design and feasibility investigation. Here a first table like tensegrity structure has been designed based on RDEs as soft displacement elements. The structure has been built and tested with an integrated sensing electronic for simultaneous sensor monitoring.