Doctor of Philosophy, The Ohio State University, 2004, Welding Engineering

During ultrasonic welding of sheet metal, normal and shear forces act on the parts to be welded and the weld interface. These forces are a result of the ultrasonic vibrations of the tool, pressed onto the parts to be welded. Furthermore they determine the weld quality and the power that is needed to produce the weld. The main goal in this study is to measure and calculate the tangential forces that act on the parts and the weld interface during ultrasonic metal welding and correlate them to weld quality. In this study a mechanics based model was developed which included a model for the temperature generation during welding and its effect on the mechanical material properties. This model was then used to calculate the interface forces during welding. The model results were in good agreement with the experimental results, which included the measured shear force during welding. With the knowledge of the forces that act at the interface it might be possible to control weld quality (strength) and avoid sonotrode welding (sticking of the sonotrode to the parts). Without a solution to these two problems USMW will never be applicable to large scale automated production use, despite its advantages. In the experiments the influence of part dimensions, friction coefficient, normal force and vibration amplitude on weld quality and sonotrode adhesion were examined. The presented model is capable of predicting and explaining unfavorable welding conditions, therefore making it possible to predetermine weld locations on larger parts or what surface preparation of the parts to be welded would lead to an improved welding result. Furthermore shear force at the anvil measured during welding could be correlated to changing welding conditions. This is a new approach of explaining the process of USMW, because it is based on mechanical considerations. The use of a shear force measuring anvil has the potential to be implemented into welding systems and the shear force would provide an addit (open full item for complete abstract)

Committee: Karl Graff (Advisor) Subjects: Engineering, Industrial

Doctor of Philosophy, The Ohio State University, 2015, Mechanical Engineering

Ultrasonic additive manufacturing (UAM) is a low temperature, solid-state manufacturing process that enables the creation of layered, solid metal structures with designed anisotropies and embedded materials. As a low temperature process, UAM enables the creation of active composites containing smart materials, components with embedded sensors, thermal management devices, and many others. The focus of this work is on the improvement and characterization of UAM aluminum structures, advancing the capabilities of ultrasonic joining into sheet geometries, and examination of dissimilar material joints using the technology. Optimized process parameters for Al 6061 were identified via a design of experiments study indicating a weld amplitude of 32.8 um and a weld speed of 200 in/min as optimal. Weld force and temperature were not significant within the levels studied. A methodology of creating large scale builds is proposed, including a prescribed random stacking sequence and overlap of 0.0035 in. (0.0889 mm) for foils to minimize voids and maximize mechanical strength. Utilization of heat treatments is shown to significantly increase mechanical properties of UAM builds, within 90% of bulk material. The applied loads during the UAM process were investigated to determine the stress fields and plastic deformation induced during the process. Modeling of the contact mechanics via Hertzian contact equations shows that significant stress is applied via sonotrode contact in the process. Contact modeling using finite element analysis (FEA), including plasticity, indicates that 5000 N normal loads result in plastic deformation in bulk aluminum foil, while at 3000 N no plastic deformation occurs. FEA studies on the applied loads during the process, specifically a 3000 N normal force and 2000 N shear force, show that high stresses and plastic deformation occur at the edges of a welded foil, and base of the UAM build. Microstructural investigations of heat treated foils confi (open full item for complete abstract)

Committee: Marcelo Dapino (Advisor); Amos Gilat (Committee Member); Blaine Lilly (Committee Member); Stephen Niezgoda (Committee Member) Subjects: Materials Science; Mechanical Engineering

Master of Science, The Ohio State University, 2008, Welding Engineering

Ultrasonic metal welding (UMW) is a solid-state joining process in which materials are held together under moderate forces while applying localized high frequency shear vibrations, creating a true metallurgical bond. While ultrasonics have been applied extensively to joining soft materials, such as copper and aluminum, applications for joining more advanced materials are limited. UMW has generally not been considered for more advanced materials due to poor tooling life and inadequate ultrasonic power levels. In a relatively short period of time, developments in UMW equipment and potential tool materials, may allow UMW to be applied to these more advanced metals. Using commercially-available ultrasonic spot welding equipment, the ultrasonic weldability of 304 and 410 stainless steel, commercially pure and 6Al-4V titanium, and Nickel-base superalloys 625 and 718 was investigated. Tool materials developed for friction-stir weld tooling were used to develop new ultrasonic tools. Tool textures and designs were also evaluated.

Committee: Karl Graff (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Welding Engineering

Whether a vehicle runs on fossil fuel, electricity, or hydrogen, one method that increases the energy efficiency of any vehicle is to decrease the weight of the vehicle body structure by using multi-material design. Multi-material design uses strong materials such as advanced high-strength steels (AHSS) for high load bearing parts, and lightweight materials such as aluminum (Al) or magnesium (Mg) for parts that experience lower loads. Traditional resistance spot welding (RSW) is unable to create adequate dissimilar metal joints between Al and steel or Mg and steel because of the differences in physical properties and the formation of brittle intermetallics (IMCs). A variety of alternative processes have been developed to solve the dissimilar metal joining challenge, but many of them require the purchase of new machinery and use complex consumables for each joint. Ultrasonic interlayered Resistance Spot Welding (Ulti-RSW) is a recently developed joining process that uses existing RSW machinery and a cheap consumable interlayer. Ulti-RSW has proven feasibility in creating strong joints between dissimilar metals such as Al and press-hardened boron steel that are difficult to join using other joining processes. To date, the qualification of Ulti-RSW joints has been completed for quasi-static shear tension testing, but there are many other qualifications that need to be met before Ulti-RSW can be incorporated into the automotive industry. The overarching goal of this dissertation is to further qualify the Ulti-RSW process in the areas of fatigue, mode 1 loading, and corrosion, and to advance the fundamental understanding of joint microstructure and properties when joining aluminum and magnesium to steel. The specific research tasks and accomplishments are summarized as follows. The Ulti-RSW joints were fatigue tested and compared to other joining processes in the literature. Previously, there was no adequate method of comparing fatigue results across various joining (open full item for complete abstract)

Committee: Wei Zhang (Advisor); Xun Liu (Committee Member); Desmond Bourgeois (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

As plastics are increasingly used for complex and demanding applications, it is critical to reliably create multi-component assemblies with joints that can meet strict strength requirements. Unfortunately, predictive engineering tools that determine the weld strength of polymers are lacking. This deficiency limits innovative design due to the necessity of lengthy development, costing tens to hundreds of thousands of dollars to complete. To alleviate some of this cost and time burden, it is important to find a way for design engineers to predict polymer weld strength. Previous research has focused on individual elements of the weld process and/or simple geometries that are not applicable for commercial development. Additionally, published approaches have not quantitatively accounted for material morphology like crystallinity and polymer chain orientation, both of which have been theorized to have a significant effect on weld strength. Further, in this work it has been established that stress concentration due to the geometry of the polymer flow has significant effect on ultrasonic weld strength, this has not been explored in any of the reviewed literature. The objective of this work was to develop a theory-consistent set of algebraic equations that can be used in engineering development to predict the tensile strength of ultrasonically welded homogenous plastic joints. It was hypothesized that weld strength can be predicted by combining established theoretical models to account for key aspects of ultrasonic welding: • Transfer of ultrasonic vibrations to the joint. • Internal heat generation rate due to ultrasonic vibration. • Intermolecular diffusion of polymer chains across the melt interface. • Effect of the temperature cycle on the crystalline structure • Effect of shear rate during flow on polymer chain orientation • Stress concentration related to extent of flow It was further hypothesized that by repurposing injection mold modeling softw (open full item for complete abstract)

Committee: Erol Sancaktar PhD (Advisor); Sadham Jana PhD (Committee Member); Ruel McKenzie PhD (Committee Chair); Abraham Joy PhD (Committee Member); Wieslaw Binienda PhD (Committee Member) Subjects: Polymers

Doctor of Philosophy, The Ohio State University, 2018, Welding Engineering

Multi-materials vehicle structures, employing light-weight metals such as advanced high strength steels (AHSS), aluminum alloys, can satisfy the ever-increasing requirement of light-weighting and fuel efficiency, as well as maintaining or improving the crash resistance of vehicles. The present research provides a fundamental understanding of the process-microstructure-mechanical properties of resistance and ultrasonic spot welding of light-weight metals. The dissertation consists of three main parts: (1) study of the relationship of process-microstructure-mechanical properties for resistance spot welded two sheets (2T) and complex stack-ups of ultra-high strength grade of AHSS, (2) development of a novel technique, namely Ultrasonic Plus Resistance Spot Welding, for dissimilar metal joining of Al to steel, and (3) investigation of the bonding mechanism of USW of Al by in-situ relative vibration measurement. In the first part, softening in subcritical heat affected zone of resistance spot welded hot-stamped boron steels is investigated by weld microstructure characterization and tempering kinetics of martensite. The local constitutive behavior of the potential failure locations is extracted and incorporated into performance model to investigate its effect on the accuracy of deformation and failure prediction. A major challenge for RSW of complex stack-ups with large thickness ratio is the limited nugget penetration into the thin sheet at the outside of the stack-up. The effect of welding current, electrode force, electrode material/size on nugget formation and the possible ways to improve nugget penetration into the thin sheet are investigated for 3T and 4T stack-ups of AHSS. The second part of the dissertation is focused on the development of a new dissimilar metal joining method, namely ultrasonic plus resistance spot welding (abbreviated as U+RSW) for Al/Steel. The bonding mechanisms have been investigated through numerical simulation to validate the (open full item for complete abstract)

Committee: Wei Zhang (Advisor); Carolin Fink (Committee Member); Xun Liu (Committee Member) Subjects: Automotive Materials; Engineering; Materials Science; Metallurgy

Master of Science, The Ohio State University, 1981, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1971, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Welding Engineering

This research focuses on the non-destructive characterization of microstructures in Grade 91 (9Cr-1Mo-V) and Grade 92 (Fe-9Cr-2W-0.5Mo) steel welds. These alloys are creep strength-enhanced ferritic (CSEF) steels commonly used in fossil-fuel-fired and nuclear power plants. The weld integrity of these two steels is crucial for power plants' safe and reliable operations. Two welding processes, cold metal transfer (CMT) and flux-cored arc welding (FCAW), were investigated for the Grade 91 steel weld test samples. For the Grade 92 weld samples, three different heat inputs (low, medium, and high) of gas tungsten arc welding (GTAW) were utilized to replicate traditional field welding processes. The non-destructive evaluation (NDE) method used for this research was immersion ultrasonic testing (UT). Using a newly patented micro-resolution ultrasonic imaging methodology specifically designed to operate in the through-transmission configuration. A 20 MHz focused probe with an ultrasonic beam focal diameter between 250-300 μm was used as the transmitter. As the receiver, a laser vibrometer with a 6-10 μm beam diameter was used to produce highly resolved ultrasonic images with longitudinal and mode-converted shear waves. Based on the micro-resolution ultrasonic C-scan images obtained during this investigation, three microstructural regions, such as weld metal (WM), heat-affected zone (HAZ), and base metal (BM), were clearly identifiable. Various levels of ultrasonic amplitudes distributed over the three regions were correlated with electron beam backscattered diffraction (EBSD) images using grain size, grain boundaries, and dislocation densities. The results showed that areas with relatively higher ultrasonic amplitude levels were associated with smaller grains and higher dislocation densities, while areas with lower amplitude levels were associated with larger grains and lower dislocation densities. In addition, ultrasonic velocity data obtained across the three differ (open full item for complete abstract)

Committee: Desmond Bourgeois (Advisor); Dave Farson (Committee Member); Xun Liu (Committee Member) Subjects: Engineering

Master of Science, The Ohio State University, 2024, Welding Engineering

The transformation of agricultural produce through various unit operations into shelf-stable, convenient, and healthy products is vital to meet consumers' dietary needs. Numerous traditional food processing and preservation methods, such as drying, frying, smoking, salting, pickling, and more, remain widely utilized for effectively handling raw food products. These methods primarily rely on the application of heat to reduce microbial growth and prevent the proliferation of foodborne pathogens, thereby ensuring food safety. However, these thermal treatments consume significant energy, resulting in low production efficiency and prolonged processing times. Thermally sensitive food items, when exposed to heat treatment, may undergo physical and chemical changes, including changes in flavor, color, and texture, they nevertheless, still pose a risk of bacterial or viral contamination, making alternatives to heat-based processing a necessity. Furthermore, in response to the growing demand for healthier dietary choices and increased consumer awareness of nutrition, ongoing research is focused on emerging technologies that can maintain high-quality attributes with extended shelf life. This study explores the application of ultrasonic compression technology in producing meal replacement bars, aiming to replace traditional binders with a more innovative approach. The research focuses on developing and optimizing ultrasonic compression processing conditions and formulations, understanding the mechanisms involved, and analyzing the resultant temperature effects during the process. Utilizing a Dukane iQ Series Ultrasonic Press System, the study experimented with various types of commercial flours and multi-ingredient system, each subjected to ultrasonic compression under different amplitudes and energy levels. Key findings include the successful transformation of discrete flour particles into cohesive bars, a nuanced understanding of the interplay between mechanical and thermal d (open full item for complete abstract)

Committee: Xun Liu (Advisor); Gönül Kaletunç (Committee Member) Subjects: Acoustics; Food Science

Doctor of Philosophy, The Ohio State University, 2020, Mechanical Engineering

Ultrasonic additive manufacturing (UAM) is a solid-state manufacturing technology that produces near-net shape metallic parts. UAM has been demonstrated to make robust structures with a variety of material combinations such as Al-Al, Al-Ti, Cu-Cu, and Al-Cu. However, UAM welding of high strength steels has proven challenging. The focus of this work is to develop a fundamental understanding of the structure-property-process relationship of UAM steel welding through experiments and modeling. Process and post-processing methods to improve UAM steel weld quality were investigated. A custom shear test was first developed and optimized to test the mechanical strength of UAM builds. The second study demonstrated the UAM fabrication of stainless steel 410 builds which possess, after post-processing, mechanical properties comparable with bulk 410 material. Fracture surface analyses confirm the weld quality improvement caused by increasing the baseplate temperature and the application of hot isostatic pressing (HIP) post weld. In the third study, a higher weld power is demonstrated by using a cobalt-based sonotrode coating, achieving shear strengths comparable to bulk 4130 material without post treatment. Weld parameters for making UAM 4130 builds were optimized via a design of experiments study. Baseplate temperature of 400 ˚F (204.4 ˚C), amplitude of 31.5 µm, welding speed of 40 in/min (16.93 mm/s), and normal force of 6000 N were identified as optimal within the selected process window. Analysis of variance and main effect plots show that normal force, amplitude, and welding speed are significant for interfacial temperature. Similar analyses show that normal force and amplitude have a statistically significant effect on shear strength. Residual stress in UAM 4130 samples was measured for the first time using neutron diffraction. The maximum tensile residual stress for UAM 4130 is found to be relatively low at 176.5 MPa, which suggests a potentially better fatig (open full item for complete abstract)

Committee: Marcelo Dapino (Advisor); David Hoelzle (Committee Member); Farhang Pourboghrat (Committee Member) Subjects: Materials Science; Mechanical Engineering

Master of Science in Engineering, Youngstown State University, 2014, Department of Mechanical, Industrial and Manufacturing Engineering

Aluminum cables are much more cost effective and lightweight when compared to standard copper wiring. Without sacrificing conductivity, aluminum wiring can offer up to a 48% weight reduction versus copper wiring. This is particularly important in vehicle wiring, since any reduction in weight will improve fuel economy which will result in reduced carbon dioxide emissions. Although replacing copper wiring with aluminum wiring offers such advantages, it does come with its own set of challenges. One such challenge is creating successful terminal connections. Connecting aluminum cables to terminals by mechanical crimping is not nearly as effective as crimping copper cables to terminals. While crimping aluminum to terminals may work for smaller cables and wires, to connect larger aluminum cables, such as battery cables in vehicles, another method of connection should be used. A potentially effective connection alternative method is through ultrasonically welding the cables to the terminals. Ultrasonic welding is a process of joining two overlapping metal pieces by applying pressure and high frequency vibrations to them, causing dynamic shear stresses high enough for plastic deformation to occur and bond the pieces. Aluminum and aluminum alloys are one of the most easily welded structural metals by this method. Since no electrical current actually passes through the aluminum being welded, the heat of the weld is not high enough to affect the mechanical properties of the welded sample. Ultrasonic welding does have some drawbacks, such as thickness limitations, but for the cables in this project, this limitation should not be a problem. An area of particular interest in this project is the ultrasonic welding of aluminum and brass for aluminum cables/brass terminals applications in electric/hybrid electric cars. The purpose of this project is to understand the materials characteristics involved in the successful ultrasonic welding of aluminum cables to (open full item for complete abstract)

Committee: Virgil Solomon PhD (Advisor); Hazel Marie PhD (Committee Member); Pedro Cortes PhD (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2014, Welding Engineering

Additive manufacturing is an emerging production technology used to create net shaped 3-D objects from a digital model. Ultrasonic Additive Manufacturing (UAM) is a relatively new type of additive manufacturing that uses ultrasonic energy to sequentially bond layers of metal foils at temperatures much lower than the melting temperature of the material. Constructing metal structures without melting allows UAM to have distinct advantages over beam based additive manufacturing and other traditional manufacturing processes. This is because solidification defects can be avoided, structures can be composed of dissimilar material and secondary materials (both metallic and non-metallic) can be successfully embedded into the metal matrix. These advantages allow UAM to have tremendous potential to create metal matrix composite structures that cannot be built using any other manufacturing technique. Although UAM has tremendous engineering potential, the effect of interfacial bonding defects on the mechanical and thermal properties have not be characterized. Incomplete interfacial bonding at the laminar surfaces due to insufficient welding energy can result in interfacial voids. Voids create discontinuities in the structure which change the mechanical and thermal properties of the component, resulting in a structure that has different properties than the monolithic material used to create it. In-situ thermal experiments and thermal modeling demonstrates that voids at partially bonded interfaces significantly affected heat generation and thermal conductivity in UAM parts during consolidation as well as in the final components. Using ultrasonic testing, elastic properties of UAM structures were found to be significantly reduced due to the presence of voids, with the reduction being the most severe in the transverse (foil staking) direction. Elastic constants in all three material directions decreased linearly with a reduction in the interfacial bonded area. The lin (open full item for complete abstract)

Committee: Wei Zhang PhD (Advisor); Sudarsanam Suresh Babu PhD (Committee Member); Glenn Daehn PhD (Committee Member); Stanislav Rokhlin PhD (Committee Member) Subjects: Aerospace Materials; Materials Science; Mechanical Engineering

Master of Science, The Ohio State University, 2012, Welding Engineering

The extension of Ultrasonic Additive Manufacturing (UAM) to dissimilar materials allows for increased application in the aerospace, automotive, electrical and power generation industries. The benefit of UAM over standard ultrasonic welding is the ability to form complex geometries, such as, honeycomb structure and internal channels and also embed wires and sensors to create smart materials. UAM has had limited success bonding dissimilar materials and thus Very High Power Ultrasonic Additive Manufacturing (VHP UAM), which increases the amplitude (from 26μm to 52μm) and normal force (from 2.5kN to 33kN), has been introduced to address this deficiency. Al3003 and Cu110 dissimilar VHP UAM builds were heat treated at 350°C for ten minutes. A measure of maximum push-pin force revealed an improvement in the heat treated condition (from 23% to 49%) for all geometries. Intermetallic phase formation was noticed using the scanning electron microscope (SEM) backscatter detector. X-ray diffraction (XRD) was utilized to characterize the intermetallic layers through peak phase analysis. Al2Cu, AlCu and Al4Cu9 were found on the fracture surface of a heat treated build. It was determined that fracture occurred between the AlCu and Al4Cu9 intermetallic layers. High resolution SEM and fractal analysis were used to verify these findings. Surface modification was evaluated as a method for improving bonding between dissimilar aluminum and copper welds. The copper foils were rolled with the sonotrode prior to welding, which increased the surface roughness from 0.175 Ra μm to 1.170 Ra μm and then placed face down before welding. The maximum force during push-pin testing showed inconclusive results. Load versus displacement curves were analyzed and it was evident that modified structures exhibited a more energetic failure compared to as-welded builds. A hypothesis was created to explain this phenomenon. It was expected that the peak load is a function of metallurgical bonding, while mecha (open full item for complete abstract)

Committee: Suresh Babu (Advisor); John Lippold (Committee Member) Subjects: Engineering; Materials Science

Master of Science, The Ohio State University, 2009, Mechanical Engineering

Nickel-Titanium (NiTi) is a shape memory alloy that, depending upon composition, can exhibit shape memory or superelastic properties, recovering up to 8% deformation. Utilizing the shape memory effect it is possible to use NiTi as an actuator replacing traditional mechanical systems with a light-weight system using a fewer number of moving parts. In addition to strain recovery, NiTi undergoes significant changes in its material properties, including elastic modulus and electrical resistivity. With these changes in material properties, it is possible to create NiTi based transducers. Currently, NiTi is limited to niche applications due primarily to difficulty in machining and joining NiTi to traditional structural materials. The goal of this thesis is to develop and characterize consistent methods of creating adaptive structures using NiTi. The research presented consists of two parts; the first deals with the development and characterization of cost-effective methods of joining NiTi and common aluminum and steel alloys. Laser welding, tungsten inert gas welding, and ultrasonic soldering were used to create joints between NiTi and itself, aluminum 2024, O1 tool steel, and 304 stainless steel. Where applicable, joints were subject to mechanical testing and analysis using optical microscopy. The second part explores the development and characterization of NiTi/Al metal matrix composite transducers constructed using Ultrasonic Additive Manufacturing (UAM), a low temperature solid-state process also referred to as ultrasonic consolidation. An aluminum UAM matrix was first characterized through mechanical testing and analysis using optical microscopy. Using UAM, aluminum matrix composites with embedded NiTi wires were created with up to a 13.4% NiTi cross sectional area ratio. The composites were tested to characterize their stiffness as a function of temperature. A model was also developed using the Brinson constitutive model in order to predict the stiffness and strain (open full item for complete abstract)

Committee: Marcelo Dapino PhD (Advisor); Somnath Ghosh PhD (Committee Member) Subjects: Engineering; Mechanical Engineering