Master of Science in Engineering (MSEgr), Wright State University, 2006, Mechanical Engineering

Models to capture the physics of jointed structures have been proposed for over 40 years. These models approximate the behavior of the joint under carefully developed operating conditions. When these conditions change, the model has to be changed. Recent developments in numeric codes like finite elements have created interest in incorporating joint models into the design process but joint models need to represent the joined structure over a broader operating range. This work investigates the dynamic response of a structure with a joint. Isolation of a few dominant effects may give way to a model able to capture a broader operating range. To isolate the effects of the joint two specimens were created. A specimen that is without a joint serves as a control. The second specimen is geometrically similar and contains a double lap joint with a bolt fastener. The differences between the specimens represent the effects of the bolt. Control variables of bolt tension, excitation level and sampling time were chosen. Amplitude response and hysteresis curves were recorded. This data was used to examine the non-linear response of the bolted specimen. Qualitative observations are included. The control specimen shows little effect from non-linear behavior in the frequency response. The bolted specimen shows non-linear behavior in the frequency response. When the joint is introduced to the geometry the system drops in amplitude, drops in resonant frequency, and demonstrates a non-linear softening effect. As the initial bolt tension is reduced the magnitudes of these changes increase. In addition when the system is allowed to dwell with a single sine wave at resonance the amplitude of the response often increases. Hysteresis curves reveal that more than a softening non-linearity affects the response. The curve shows a softening affect when displacing in one direction and a hardening affect when displacing in the opposite direction. This may be affected by the geometry as the control (open full item for complete abstract)

Committee: Joseph Slater (Advisor) Subjects: Engineering, Mechanical

Master of Science (MS), Ohio University, 2003, Mechanical Engineering (Engineering)

This thesis has presented kinematics, hardware construction, and control architecture for the planar parallel 3-RPR manipulator built at Ohio University. This three-dof manipulator is actuated by three active pneumatic cylinder prismatic joints. The revolute joints are all passive. The workspace computation and analysis have also been presented in chapter 2. In a limited workspace the robot can reach general planar poses (translation and rotation). Applications for this type of robot include manufacturing and assembly where high speed and accuracy are required in a relatively small workspace. Other applications are planar motion simulators and haptic interfaces. The 3-RPR hardware is controlled in real-time via a PC with a Simulink model reading LVDT feedback and commanding solenoid valves via the Quanser Multi-Q boards and Wincon software. The control architecture controls the three pneumatic cylinder lengths independently but simultaneously in this environment. The coordinated Cartesian control of the 3-RPR planar parallel robot via linearized independent prismatic link length control has been implemented. The Simulink block diagram is built, based on this control architecture. The control routine for the Cartesian control modes (inverse pose control or resolved rate control) has been proposed and can be implemented as suggested in the concluding chapter. Future work suggests hardware improvements should be made to improve accuracy. Also, workspace optimization can be done for future work.

Committee: Robert Williams, II. (Advisor) Subjects: Engineering, Mechanical

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

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

Committee: Not Provided (Other) Subjects:

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

Committee: Not Provided (Other) Subjects:

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

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

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

Reducing the weight of vehicles can help automotive manufacturers meet emissions standards and improve the performance of their vehicles. This weight could be shed by using lightweight materials such as carbon fiber or aluminum, but these materials require more complex joining solutions than traditional materials. The goal of this experiment was to develop techniques that improve the joints between these lightweight materials. The first technique attempted to reduce the amount of damage that carbon fiber sustained from mechanical fasteners. Carbon fiber composites were created in which the fibers were moved around the location of where a multiridged fastener would go to join the composite with aluminum 7075-T6 in a single lap-shear configuration. The hypothesis was that these fibers would not be fractured during fastening, and reducing the number of broken fibers would increase the amount of force that the joint could hold and the amount of energy that it could absorb. The second technique was designed to repair sustained by carbon fiber composites during the fastening process. This was attempted by combining the premade hole in the carbon fiber with an adhesive between the interface of the carbon fiber and the aluminum being joined. The hypothesis was that the pressure from the fastening process iii would force the adhesive to run through the premade hole and repair any damage that the fastener caused while being inserted. These joining techniques were evaluated with a tension test that pulled the joints to failure. The tests showed that moving the fibers around the location of the fastener had no effect on the amount of force the joint could hold or the amount of energy that it absorbed. However, combining this movement of fibers with adhesive between the interface of the joint showed an interaction between the treatments that increased the amount of force that the joint could hold but not the amount of energy that i (open full item for complete abstract)

Committee: Alok Sutradhar (Committee Member); Anthony Luscher (Advisor) Subjects: Mechanical Engineering

MS, Kent State University, 2024, College of Architecture and Environmental Design

Transformability in structures presents opportunities to challenge traditional spatial programming and form-making concepts. Unlike conventional static buildings, deployable structures provide dynamic solutions to changing environmental conditions, adaptive locations, functional transformations, and emergency relief scenarios. This thesis aims to analyze and design dynamic, movable joints to produce a transformable, free-form structure. Adolfo Perez-Egea notes that the “study of deployable structures has been carried out traditionally by simplifying their constituent elements—joints and rods—to ideal entities.” (Perez-Egea, A. et al., 2021) Exploring constituent elements offers an opportunity to understand the dynamics between components as well as identify opportunities for novel material assemblies and detailing methods. In transformable structures, joints provide needed support among interdependent elements (rods) while also enabling a family of intersecting conditions. This study will explore these types of flexibilities and the spatial morphologies movable joints can produce. The small-scale toy 'Magic Torus' (Nishihara A., 2014) will serve as design inspiration and a translated case study in the development of prototypes for an inhabitable environment. Flexible glass fiber-reinforced polymers (GFRP) rods have been selected for this study due to their combined high tensile and flexural strength, low bending stiffness, and large deformations to make free-form structures.

Committee: Diane Davis-Sikora (Advisor); Nick Safley (Committee Member); Rui Liu (Committee Member) Subjects: Architectural; Architecture

Master of Science, University of Toledo, 2023, Civil Engineering

Beam-column joints play a critical role in transferring forces between beam and column elements and maintaining structural integrity during severe loading. While the nonlinear behaviors of beams and columns are commonly modelled in global frame analyses through the use of plastic hinges, the behavior of joints through the use of rigid end offsets is often omitted. The objective of this study is to develop an artificial neural network and derive the plastic hinge curves required for modeling beam-column joints in global frame analyses. As the first step, a feed-forward artificial neural network (FFNN) is developed to predict the shear strengths of beam-column joints. A comprehensive dataset of 598 experimental joint specimens is compiled from 153 previously published research studies. The 555 data points which passed the exploratory data analysis are used to train, test, and validate the proposed network for applicability to a wide range of input variables and joint configurations. The accuracy and reliability of the proposed FFNN were evaluated using a comprehensive set of evaluation metrics in comparison with three existing networks from the literature. The network predicted shear strength is used to derive shear stress-strain and moment-rotation curves for joint hinges. A spreadsheet tool is developed to execute the network formulations, calculate joint shear strength, and derive joint hinge curves for practical use by engineers and researchers.

Committee: Serhan Guner (Committee Chair); Luis Alexander Mata (Committee Member); Douglas Karl Nims (Committee Member) Subjects: Civil Engineering

Master of Science, University of Akron, 2023, Geology

Rocks develop cracks (joints) to relieve internal stresses as they are depressurized. Joints increase the permeability in rocks, which affects fluid and contaminant flow in the formation. There are three possible causes of joint formation in Northeastern Ohio: tectonics, glaciation, and valley relief. The thoroughly jointed formations exposed in NE Ohio are part of the Appalachian Plateau which has experienced unloading stresses due to the Alleghanian Orogeny (315-270 mya), a more recent series of glaciation events in the Pleistocene (700,000-14,000 years ago) and valley formation by erosion. I measured joint orientations in formations exposed in Northeastern Ohio that were deposited before and during the Alleghanian Orogeny to determine if their orientations reflect stresses during the Alleghanian Orogeny, the Pleistocene ice age, or valley unloading processes. Joint spacing was also measured to determine if a relationship exists between lithology and the joint spacing. I measured joints in the Olmsted siltstone bed of the Ohio Shale (n=131), Cleveland Member of Ohio Shale (n=131), Bedford Shale (n=209), Berea Sandstone (n=137), Orangeville Shale Member (n=27), Sharpsville Sandstone Member (n=203), and the Meadville Shale Member (n=203). I also analyzed measurements of joint orientations in coal seams, the Ohio Shale, the Black Hand Sandstone Member and Sharon Sandstone from previous studies by Ver Steeg (1942), Miller (1996), Filiano (2014), Ritter (2016), and Rieman (2017). The data suggests that the joints in all formations were predominantly formed due to tectonics during the main stage of the Alleghanian Orogeny based on the orientation of the primary joint set, which was oriented parallel to maximum compression direction during this event.

Committee: Caleb Holyoke III (Advisor); Molly Witter-Shelleman (Committee Member); Ira Sasowsky (Committee Member) Subjects: Geology

Master of Science (MS), Ohio University, 2022, Civil Engineering (Engineering and Technology)

This research reviewed the current and future uses of Ultra-High Performance Concrete (UHPC) for bridge applications in the state of Ohio. Since most designers, owners and contractors are unfamiliar with the material and only a small percentage of all bridges utilize it, UHPC is still considered a relatively new material. Monitoring and understanding its performance in current applications will undoubtedly provide useful insights for future applications. Advantages of UHPC discussed include rapid strength gain that can be utilized in Accelerate Bridge Construction, fiber content which provides post cracking strength, high bond strength which shortens development lengths of reinforcement, and the flowable material which allows UHPC to better penetrate tighter spaces. Disadvantages of UHPC such as material cost, increased labor and time are also discussed. In addition, recommendations for future UHPC applications are provided that would benefit designers, owners and contractors through valuable insight that was gained during these research objectives. The first objective was to review the performance of UHPC in the Sollars Road adjacent prestressed concrete box beam bridge in Fayette County. The design of the UHPC longitudinal joint (shear keys) included dowel bars but eliminated intermediate diaphragms, transverse post-tensioning, and a composite deck. Comparing truck loading data from 2014 shortly after bridge construction was completed and 2017 during this study, the load distribution has improved to some extent and the bridge is responding to loading in a similar manner which implies minimal to no cracking of the UHPC shear keys. This simplified design may be a realistic alternative to solve the typical issue of cracking in the longitudinal joints (shear keys) and associated reflective cracking in composite decks for adjacent prestressed concrete box beam bridges. This improved behavior with UHPC joints may result i (open full item for complete abstract)

Committee: Eric Steinberg Ph.D. P.E. (Advisor) Subjects: Civil Engineering

Master of Science, The Ohio State University, 2020, Mechanical Engineering

A primary goal for an automobile manufacturer is to increase the fuel economy in the case of IC engines or increase the battery life in the case of electric vehicles. Light-weight automotive design, without sacrificing the strength, stability and crash safety worthiness, is one of the ways to achieve this. Light-weight vehicle structures are trending toward a multi-material solution which requires, in many cases, novel mechanical fastening solutions. This thesis investigates several variations of multi-ridged fasteners. The depth of the ridges, the smoothness of the nails, and two novel nail topologies are all investigated. Al 6061 T6 and Al 6061 T4 were used as test materials with RIVTAC® nails acting as a control group for this study. The load carrying capacity of the joints were studied with respect to changes in the smoothness of the nails. It was determined that as the smoothness of the nail increases, the strength of the joint reduces. Another study was performed to see the effect of reducing the ridge depth of the control group by half. It was found that, the strength of the joints with the full scale ridge depth is higher than the half scale ridge depth. Then, a unique topology of a nail is researched such that rotating the nail by a certain angle after insertion leads to better ridge engagement. But that lead to loosening of the joint ultimately reducing the joint's retention strength. At the end of the study, it was concluded that, ridges are critical in the performance of the joint and the formation of the petals has to be controlled in order to create a better joint.

Committee: Anthony Luscher (Advisor); Alok Sutradhar (Committee Member) Subjects: Experiments; Mechanical Engineering

Master of Science, The Ohio State University, 2019, Welding Engineering

Brazing is a unique process capable of joining materials with minimal damage to the base material properties. Ni-base superalloy brazed joints are used for the manufacture and repair of high temperature gas turbine engines. However, the mechanical behavior of the brazed joint microstructure is still not fully understood. In addition, there are no standard test methods that include correction factors for the stress concentrations, high tri-axial stress, and potential defects that can reduce the strength of a brazed joint. This project's goal was to develop a multi-scale model including the damage zone method for the prediction of brazed joint mechanical behavior by investigating shear and tensile loading conditions. The study investigated the impact of a variable braze joint geometry (lap, butt, and pin-in-collar), type of loading (tensile or shear), and form of braze filler metal (foil or paste) had on the mechanical performance of IN718/BNi-2 braze joints. The damage zone method was applied to model and predict the strain concentrations and joint strength of the brazed test samples using finite element analysis in Abaqus software and was validated through digital image correlation measurements. Ultrasonic immersion non-destructive flaw inspection and scanning election microscope fractography work was also completed to better understand the failure mechanisms and their correlation to the microstructure and quality of the brazed joints. Although all sample sets increased in strength with increasing joint area, changes in sample geometry, microstructure, and joint quality impacted the magnitude of the strength. Thermal cycle testing determined that a brazing temperature of 1065oC, a hold time of 10 minutes, and a joint gap of 75 um or lower is required to maintain a volume of fraction of brittle eutectic intermetallics below 10%. Applying the damage zone model to the foil type experimental results, the failure load was predicted for both double lap and pin-in- (open full item for complete abstract)

Committee: Boian Alexandrov Dr. (Advisor); Avraham Benatar Dr. (Advisor); Wei Zhang Dr. (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2019, Welding Engineering

This research seeks to understand the low-cycle fatigue performance of welds for the repair of Coke Drums. These are pressure vessels that experience failure due to constant exposure to cyclic thermal and mechanical loads. Weld repair procedures are often performed on these vessels; however, re-cracking within less than 10.000 operating cycles is a common issue in the repaired regions. Failures have been associated with the low-cycle fatigue phenomenon at elevated temperatures, which usually involves plastic strain accumulation of the material every operation cycle. The downtime costs for repair these units in the refineries are elevated; therefore, improving the fatigue strength of the repair joints is of paramount importance, and is an active topic of research. This study was divided into an experimental evaluation and a numerical analysis. The experimental evaluation consisted of studying the low-cycle fatigue performance of 1.25Cr-0.5Mo steel base plates and weld metal samples, which were obtained using matching ferritic and Ni-base filler materials. First, it was necessary to design the sample geometry and implement a testing procedure in the Gleeble, to produce a strain-controlled low-cycle fatigue test at elevated temperatures. Then, weld repair mockups were produced following procedures used in real repair conditions, from which samples were extracted for microstructure characterization, fatigue testing, and failure analysis. The microstructure and failure analysis were performed using optical microscopy, scanning electron microscopy, and electron back-scattered diffraction; additionally, mechanical properties were measured using micro-hardness, instrumented indentation testing, nano-indentation, and uniaxial strain-controlled cyclic loading. The numerical analysis consisted of studying the cyclic plasticity behavior of the joint using the finite element method. Material properties were obtained from cyclic testing using non-linear isotropic/kinematic hard (open full item for complete abstract)

Committee: Antonio Ramirez (Advisor); Carolin Fink (Committee Member); Herman Shen (Committee Member); Jinghua Li (Committee Member) Subjects: Materials Science; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2019, Mechanical Engineering

Mechanical connection of parts through jointed connections are prolific throughout modern engineering applications; however, precision analysis and design of these systems remains difficult. Experimental findings have revealed a myriad of nonlinear properties of these systems such as nonlinear damping, hysteresis, etc., and these complex effects lead to extreme difficulties in the characterization and modeling of these common structural elements. To exacerbate matters, high-fidelity numerical analysis of these systems is often impractical due to disparate length and time-scales between microslip in the joint and macro-scale effects of interest. In this dissertation, original research on the analysis of damping of jointed structures is presented. This includes theoretical work in advancement of reduced-order modal models as well as practical development of Abaqus subroutines to implement cutting-edge damping models into finite element models. This work culminates in the study of a practical problem of interest to Sandia National Labs involving a jointed structure under blast loading, and important conclusions are draw about the nature of jointed structures under complex loads.

Committee: Donald Quinn (Advisor); Graham Kelly (Committee Member); Xiaosheng Gao (Committee Member); Ernian Pan (Committee Member); Kevin Kreider (Committee Member) Subjects: Aerospace Engineering; Applied Mathematics; Mathematics; Mechanical Engineering; Mechanics

MS, University of Cincinnati, 2018, Engineering and Applied Science: Mechanical Engineering

Different type of joints such as bolted joint, screw joint, riveted joint, sleeve joint and welded joints are used in mechanical assembly to join two or more parts. The selection of a joint type and design depends on the primary function. While performing the primary function of joint, these joints also introduce nonlinearity in the assembly and makes it difficult to predict vibration response of structure. Amplitude dependent modal frequencies and amplitude dependent damping are observed nonlinearities in vibration measurements. Current finite element analysis approaches assume the joint as linear connection when predicting modal frequencies and mode shapes. This can lead to errors in estimation of vibration response, stress calculations and life of the component. A bolted joint connection is considered under present work. The work focuses on analysis of different design and assembly parameters of bolted joint connection. Bolt size, bolt preload, bolt tightening method, flange thickness, grip length are various bolt parameters, that may have effect on dynamic characteristics of structure. Any variation in contact pressure and residual stress state of bolted joint would change vibration behavior of structure. These joint parameters are varied with in practical, design margins and their effect on estimation of modal frequencies and mode shapes are quantified using finite element analysis. A high-fidelity modelling approach is used for finite element parametric study. Residual stress at the joint is another important factor that effects contact pressure and interface nonlinearity. This cannot be modelled using linear modal analysis methods. Residual stress type of tension, compression and shear loads are applied and effect of these loads on modal frequencies of structure are analyzed using high fidelity modelling (HFM) method. Bolted joints behave differently for cold application and hot application. Increase in temperature causes preload variation in the bol (open full item for complete abstract)

Committee: Randall Allemang Ph.D. (Committee Chair); David Thompson Ph.D. (Committee Member); Yongfeng Xu Ph.D. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Materials Engineering

In practice, adjacent preform sandwich cores are joined with a simple butt joint without special precautions. When molded, this gap is filled with resin and creates a resin rich area. Stress risers will be amplified under cyclic load, and consequently, the serviceability of the structure will be affected. Designers and researchers are aware of this problem; however, quantifying this effect and its intensity and consequence on the service life of the structures has not yet been developed. Despite pervious findings, limited experimental data backed by a comprehensive root cause failure analysis is available for sandwich under axial static, fatigue and post-fatigue. If such a comprehensive experimental characterization is conducted, specifically understanding the nature of the damage, intensity, and residual strength, then a valid multi-scale damage model could be generated to predict the material state and fatigue life of similar composite structures with/without core joints under in-plane static and fatigue load. This research study characterized the effect of scarf and butt core joints in foam core sandwich structures under in-plane static and fatigue loads (R=0.1 and R= -1). Post-Fatigue tensile tests were also performed to predict the residual strength of such structures. Nondestructive Evaluation Techniques were used to locate the stress concentrations and damage creation. A logical blend of experimental and analytical prediction of the service life of composite sandwich structures is carried out. The testing protocol and the S-N curves provided in this work could be reproducible and extrapolated to any kind of core material. This research study will benefit composite engineers and joint designers in both academia and industry to better apprehend the influence of core joints and its consequence on the functionality of sandwich structures.

Committee: Elias Toubia (Advisor); Paul Murray (Committee Member); Thomas Whitney (Committee Member); Youssef Raffoul (Committee Member) Subjects: Aerospace Engineering; Aerospace Materials; Civil Engineering; Composition; Design; Engineering; Materials Science; Mechanical Engineering; Polymers

Doctor of Philosophy, The Ohio State University, 2017, Welding Engineering

Brazed joints are commonly used in the manufacture and repair of aerospace components including high temperature gas turbine components made of Ni-base superalloys. For such critical applications, it is becoming increasingly important to account for the mechanical strength and reliability of the brazed joint. However, material properties of brazed joints are not readily available and methods for evaluating joint strength such as those listed in AWS C3.2 have inherent challenges compared with testing bulk materials. In addition, joint strength can be strongly influenced by the degree of interaction between the filler metal (FM) and the base metal (BM), the joint design, and presence of flaws or defects. As a result, there is interest in the development of a multi-scale computational model to predict the overall mechanical behavior and fitness-for-service of brazed joints. Therefore, the aim of this investigation was to generate data and methodology to support such a model for Ni-base superalloy brazed joints with conventional Ni-Cr-B based FMs. Based on a review of the technical literature a multi-scale modeling approach was proposed to predict the overall performance of brazed joints by relating mechanical properties to the brazed joint microstructure. This approach incorporates metallurgical characterization, thermodynamic/kinetic simulations, mechanical testing, fracture mechanics and finite element analysis (FEA) modeling to estimate joint properties based on the initial BM/FM composition and brazing process parameters. Experimental work was carried out in each of these areas to validate the multi-scale approach and develop improved techniques for quantifying brazed joint properties. Two Ni-base superalloys often used in gas turbine applications, Inconel 718 and CMSX-4, were selected for study and vacuum furnace brazed using two common FMs, BNi-2 and BNi-9. Metallurgical characterization of these brazed joints showed two primary microstructural regions; a s (open full item for complete abstract)

Committee: Boian Alexandrov Ph.D. (Advisor); Avraham Benatar Ph.D. (Advisor); Carolin Fink Ph.D. (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2000, Graduate School

Committee: Not Provided (Other) Subjects: Engineering