Bachelor of Science (BS), Ohio University, 2017, Biological Sciences

Osteoporosis is a disease characterized by diminished bone strength, resulting in an increased risk for fracture with minimal trauma. Though osteoporotic fractures present severe consequences for patients and health communities alike, there remains to be an accurate diagnosis for this disease. There are many characteristics that influence bone strength, ranging from mechanical, microstructural, to geometrical in nature. This project specifically aimed to assess cortical porosity, diameter, and bending stiffness as predictors of bending strength in the human radius. Data was collected from thirty cadaveric human radii from men and women between the ages of 17-99 years. Bending strength and bending stiffness were measured by the gold standard three-point bending method, quasi-static mechanical testing (QMT). Interosseous diameter was measured from both higher resolution µCT and lower resolution CT scans. Finally, cortical porosity was measured from µCT scans in the NIH image-processing software ImageJ. These measurements were guided by 3D Avizo models. Simple linear regression analyses revealed that bending stiffness predicted bending strength with the least amount of uncertainty (SEE=3.2 Nm). Cortical porosity demonstrated the weakest relationship with bending strength (SEE=12.0 Nm). Predictions of bending strength by µCT diameter were not different from those made by CT diameter (p=0.37). In comparisons of cortical porosity in the radius and ulna as imaged from the same arms, porosity at the 55%L of the ulna was the only unbiased predictor of radius porosity adjacent to the QMT fracture site (p=0.12). Thus, at the midshaft, cortical porosity of the ulna and radius appear to be indistinguishable.

Committee: Anne B Loucks PhD (Advisor) Subjects: Anatomy and Physiology; Biology; Cellular Biology; Endocrinology; Kinesiology; Medical Imaging; Molecular Biology; Morphology; Physiology

Master of Science in Engineering, University of Akron, 2015, Biomedical Engineering

Orthopedic implants are used as medical devices that are surgically implemented into the body and designed to replace a missing joint, a bone or to support a damaged structure. Even though orthopedic implants have excellent outcomes such as restoring mobility and increasing the quality of lives, the failure of these implants occasionally takes place. This thesis examines a process called “superfinishing” as an alternative surface modification method for use on orthopedic implants that may yield better patient outcomes. It is believed that superfinishing may improve desired properties such as bending stress, fatigue strength, resistance to bacteria adhesion, wear resistance, chemical inertness, low coefficient of friction, and similar or better adhesion characteristics than stainless steels/titanium. The focus of this thesis is to show improvement in bending strength. In this study, specimens were superfinished in two different types of abrasives: aluminum oxide (Al3O2) and silicon carbide (SiC). The results demonstrated that roughness value of stainless steel rods in Al2O3 powder/walnut shell mix decreased to 0.156µm from 0.221µm and roughness value of stainless steel rods in SC powder/walnut shell mix decreased to 0.100µm from 0.184µm which is 36-44% decrease in roughness value. The experiment indicated that roughness value of these rods becomes stable after 21 minutes of superfinishing process but the maximum average load results were collected after 9 minutes of superfinishing process. This study showed that the longer superfinishing process does not necessarily increase the bending strength. This study also showed that the bending strength of superfinished Ti-6Al-4V rods was increased by 3.81% with SiC abrasives. In addition, bending strength of superfinished 316L rods were increased by 3.35% in Al3O2 abrasives and by 6.49% in SiC abrasives after 9 minutes of superfinishing process. Residual stresses should be studied as the future work to g (open full item for complete abstract)

Committee: Ajay Mahajan Dr. (Advisor) Subjects: Biomedical Engineering

Doctor of Philosophy, The Ohio State University, 2019, Industrial and Systems Engineering

Edge fracture, defined simply as fracture originated from the edge, is a common problem in sheet metal forming, especially when forming Advanced High Strength Steels (AHSS). The increase of AHSS in the automotive industry has derived into substantial efforts in order to predict and prevent the edge fracture phenomenon. Nearly every sheet metal forming operation includes cutting of the material at some point and, depending on the cutting process, the damage produced at the edge reduces its formability in subsequent operations. The edge fracture has been approached from various perspectives: observation of the cut edges in order to correlate their geometries to edge fracture occurrence, methods to evaluate edge stretchability, Finite Element (FE) simulations to predict it, design of new cutting methods (i.e. tool geometries or configurations) or post-processing of the edge to eliminate residual stresses (i.e. annealing or machining). Nevertheless, there is not a consensus in the field regarding which ones are the most important factors that should be considered in sheet metal cutting. Furthermore, researchers, very often, overlook practical parameters during laboratory test (e.g. non-uniform cutting clearances, tool wear, etc.); hence, these laboratory tests, generally, do not represent the cutting conditions found in the practice. This project aims to propose guidelines that could be considered to evaluate, maintain and improve a given cutting process for a required edge stretchability. In order to achieve this objective, four cases studies, which include most of the of the typical challenges in sheet metal cutting, were conducted: trimming along a straight line, piercing of a round hole, blanking of an irregular geometry and use of shaving (two-stage cutting) to improve edge stretchability. Chapter 1 of this study gives a brief introduction to the edge fracture problem and the available sheet metal cutting techniques. Chapter 2 summarizes the research objec (open full item for complete abstract)

Committee: Taylan Altan Dr. (Advisor) Subjects: Industrial Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Bending operations such as U-bending, hat bending, V-bending etc. are commonly used operations in the sheet metal forming industry. Springback is one of the most difficult and important challenges to forming good quality parts in these operations, especially for materials like Advanced High Strength Steels, Copper and Aluminum. Currently, dies are modified and re-cut three to five times in the industry to compensate for springback and ensure part quality. Improving the accuracy of prediction and reduction of springback would reduce the time and cost for die development and tryout. Existing mathematical models for springback prediction are complicated and require various material parameters that are difficult or expensive to obtain. This study aims to develop a simple method for accurate prediction and reduction of springback in the U-bending and Wipe bending processes. Experiments were carried out for U-bending of AHSS and Aluminum using Shiloh die and S shaped die and wipe bending of Copper alloy using a die designed at CPF. The materials were bent to different angles. Simulations were carried out using DEFORM and PAM-STAMP for same conditions as experiments. The springback results of simulation and experiments were compared and inverse analysis was carried out to find the value of apparent E-moduli that would accurately predict the springback in different materials for the different bending angles. Experiments were conducted to investigate the effect of ram speed and ram motion on springback of AHSS and Aluminum alloys in the U-bending process. Simulations were conducted in PAM-STAMP to study the effect of variation of pad force on springback in U-bending with crunching operation. Inverse analysis was successfully applied to predict springback accurately in different materials with different part geometries. An apparent E-modulus vs strain curve was developed which can be input to FE software for the analysis of forming operations and springback. Ram speed a (open full item for complete abstract)

Committee: Dr. Taylan Altan (Advisor); Dr. Blaine Lilly (Committee Member) Subjects: Engineering; Mechanical Engineering

Bachelor of Sciences, Ohio University, 2017, Biological Sciences

Osteoporosis is a systemic, skeletal disease characterized by decreased bone strength that predisposes individuals to an increased risk of fracture. Unfortunately, there is no clinical device able to measure bone strength. Instead, osteoporosis is diagnosed on the basis of bone mineral density (BMD) as measured by dual-energy X-ray absorptiometry (DXA). However, research has shown that BMD does not predict fractures well. Bone strength has been shown to be predicted accurately by bone stiffness (EI), but no clinical device measures bone stiffness either. Ohio University is developing Mechanical Response Tissue Analysis (MRTA) to measure EI of the human ulna in vivo. Accurate predictions of ulna bending strength are of limited clinical importance, however, unless the ulna is representative of other long bones. The radius is of further clinical importance because a fracture of the radius often precedes and could predict fractures at more serious sites such as the hip. This project used cadaveric radius specimens, of which the ipsilateral ulna was previously tested, to determine the accuracy with which radius bending strength was predicted by various predictors from both mechanical testing of the radius and ulna and DXA measurements of the radius. Mechanical testing methods included MRTA of the ulna in vivo and quasistatic mechanical testing (QMT) of the ulna and radius ex vivo. DXA measurements included scans of the standard UD and 1/3 sites of the radius. Linear regression analyses revealed that ulna EI measured by MRTA is a more accurate predictor of radius bending strength than BMD measurements, but is not the most accurate predictor. Radius EI and BMC at the 1/3 site were the most accurate predictors of radius bending strength, though not significantly different from each other. The most accurate predictor of radius EI was BMC at the 1/3 site.

Committee: Anne Loucks Ph.D (Advisor); Lyn Bowman Engr (Other) Subjects: Anatomy and Physiology; Biomechanics; Medical Imaging

Master of Science, Miami University, 2016, Geology and Environmental Earth Science

We examine the along-strike transition from flat to steeper subduction in Oaxaca, Mexico to provide a better understanding of what controls the slab morphology. Prior studies have suggested the slab tends to tear along the transitions in dip as the slab rolls back. We determine the slab geometry based on local seismicity, nonvolcanic tremor (NVT), and slow slip utilizing a deployment of broadband seismometers and continuous GPS receivers distributed in and around Oaxaca. We construct depth contours of the subducting slab surface down to 100 km, which illustrate that the transition from flat to steeper subduction occurs rapidly via a sharper flexure than previously recognized. The prior catalog of NVT in Oaxaca is extended using the same method and additional stations that extend further west. The band of NVT follows the new slab contours, widening towards the west with the downdip extent gradually moving inland. The amount of NVT also correlates with the strength of an ultra slow velocity layer. There are no gaps in seismicity, NVT, or slow slip across the rapid transition in slab dip, further supporting the notion that the slab is not currently torn in the updip region. We propose that the sharp flexure is possible in this region due to bending moment saturation that leads to greater curvature in both the down-dip and along-strike directions. A similar set of observations in southern Peru suggests this is a viable alternative to tearing that accommodates the large strains from variable rates of slab rollback.

Committee: Michael Brudzinski (Advisor); Brian Currie (Committee Member); Elisabeth Widom (Committee Member) Subjects: Geophysics; Plate Tectonics

Bachelor of Science (BS), Ohio University, 2015, Biological Sciences

Osteoporosis is a disease characterized by a decline in bone strength leading to an increased risk of fracture, but no clinical device measures bone strength. Bone strength is strongly associated with bone stiffness (EI), but no clinical device measures EI either. Mechanical Response Tissue Analysis (MRTA) is being developed to measure EI in human ulna bones in vivo. Bone EI depends strongly on bone interosseous diameter (ID), and cortical porosity (CP) has been proposed for assessing fracture risk. This project compared the accuracies with which ulna bending strength was predicted by CP, ID, and EI in 35 cadaveric arms from men and women ranging widely in age (17-99 yrs.) and BMI (13-40 kg/m2). ID was obtained by computed tomography (CT). Ulna EI was measured noninvasively by MRTA on intact arms, while EI and bending strength were measured on excised ulnas by the gold standard method, Quasistatic Mechanical Testing (QMT), which cannot be employed in vivo. ID and CP were obtained in fractured ulnas by micro-computed tomography (µCT) by ImageJ using Avizo® 3D models to locate the endosteum. Simple and forward stepwise multiple regressions revealed that CP was the least accurate predictor of bending strength (SEE≥235N). ID as more accurate (SEE≤163N, p=0.02). Accuracies of predictions by ID from CT and µCT images were indistinguishable (p=0.35). Accuracies of predictions by EI measured by QMT and MRTA (SEE≤91N) were more accurate than CP and ID alone or together (p≤0.02) and indistinguishable from one other (p=0.12). Age was the only predictor to explain any (1%) variance not explained by EI. No model with >2 predictors was significant.

Committee: Anne Loucks (Advisor); Lyn Bowman (Other) Subjects: Anatomy and Physiology; Biology; Biomechanics; Biomedical Engineering; Biomedical Research; Health; Scientific Imaging

Master of Science, The Ohio State University, 2014, Mechanical Engineering

This Thesis is regarding the Flanging and Bending of Advanced High Strength Steels (AHSS)- a class of High Strength Steels being increasingly used by the automotive industry today. Four processes are under study here: wipe bending, shrink flanging, stretch flanging and hat-shape bending. Each of the above processes are used in many automotive parts, and each process has its own challenges- springback, wrinkling or thickening of material, material failure by thinning or edge-cracking. The Thesis describes the use of Finite Element Analysis (FEA) by means of commercially available software called PamStamp to simulate the above processes for a number of AHSS grades to predict part quality. Experiments were designed based on the FEA simulations. Experiments for hat-shape bending process were successfully conducted. A roadmap for conducting experiments for wipe bending, shrink flanging & stretch flanging is also described. Upon the completion of hat-shape bending experiments for four materials: DP590, DP980, CP800 & TRIP1180- the profiles of the formed parts were digitized into co-ordinates, and the corresponding springback angles were measured. The results were analyzed and interpreted, with the aid of post-experimental simulations.

Committee: Taylan Altan (Advisor); Blaine Lilly (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2014, Welding Engineering

High strength alloys, such as titanium alloys and steels have been widely used for armor applications. However, high strength materials have poor formability at room temperature and are prone to cracking during welding. It is necessary to develop alternative manufacturing methods that can replace conventional welding technologies. The main objectives of this project are: 1) development of a testing procedure for evaluation of the response of high strength alloys to hot induction bending, and 2) development of optimal process control windows for hot induction bending of three high strength materials: alloy Ti-6Al-4V and armor steels Armox 440 and ARL XXX. A testing procedure has been developed that combines hot ductility testing, high temperature straining using a GleebleTM thermo-mechanical simulator, high temperature straining followed by room temperature tensile testing, evaluation of response to tempering, phase transformation analysis, thermodynamic simulations, and metallurgical characterization. Hot ductility testing indicates a gradual increase in ductility of the three tested alloys as temperature increases. Strain rate has no significant effect on hot ductility of alloy Ti-6Al-4V and ARL XXX steel. During hot ductility testing, extensive void formation is observed in alloy Ti-6Al-4V between the starting temperatures of alpha and beta transformation and the recrystallization temperature, and in Armox 440 steel between the A1 and A3 temperatures. No voids were found above beta solvus temperature in Ti-6Al-4V and above the A3 temperature in Armox 440. Limited void formation occurs below the start of alpha and beta transformation in Ti-6Al-4V and below the A1 temperature in Armox 440. High temperature straining tests show that strain-induced porosity in Ti-6Al-4V can be avoided if strain is limited below 24% at 430 degrees Celsius and below 7% at 650 degrees Celsius. In Armox 440 and ARL XXX steels, voids were only observed in samples strained to failure. High (open full item for complete abstract)

Committee: John Lippold (Advisor); Boian Alexandrov (Committee Member); David Phillips (Committee Member) Subjects: Engineering; Metallurgy

Master of Science, The Ohio State University, 2012, Industrial and Systems Engineering

The design of lightweight sheet metal part components requires an understanding of material characteristics and their manufacturing processes. Increasing use of Advance High Strength Steels (AHSS) and Commercially Pure (CP) titanium sheets accompanied by many challenges due to their unique mechanical properties and low formability. Thus, developing fundamental understanding of mechanical properties is critical for successful process and tool design. FE simulations are powerful tool in identification of challenges in forming of these materials and product realization. Therefore, FE model inputs, including flow stress data, play important role for obtaining accurate results. However, obtaining the flow stress curve near production conditions (state of stress strain) might be challenging and requires material characterization test that emulates near production conditions. In this study, uniaxial tensile and biaxial Viscous Pressure Bulge (VPB) tests were conducted at room temperature to obtained material properties and flow stress for sheet materials: • DP780 (AHSS) (Thickness= 1 mm) • CP-Ti (Grade: 2) = Material A (Thickness = 1.8 mm and heat lot = HT 884971-02-00) • CP-Ti (Grade: 2) = Material B (Thickness = 0.5 mm and heat lot= KX16EM) • CP-Ti = Material C (Thickness = 1 mm and heat lot = W58KEM) Flow stresses obtained from tensile and VPB tests were compared. The strain ratios (R-values) were determined by conducting tensile tests and they were used to correct flow stress curves that obtained from VPB test for anisotropy. In VPB test, it is obvious that flow stress data can be obtained to higher strain values compared to tensile tests. Therefore, the state of stress strain from VPB test emulates real sheet metal forming conditions where process is almost always biaxial. The objective of this study was to predict springback angles in air bending process by using flow stress curves that obtained from both tensile and VPB tests. Air bending process was successfully (open full item for complete abstract)

Committee: Taylan Altan Dr. (Advisor); Jerald Brevick Dr. (Committee Member); Prasad Mokashi Dr. (Committee Member) Subjects: Industrial Engineering

Master of Science, The Ohio State University, 2011, Mechanical Engineering

As improvements in vehicle safety decrease the number of crash fatalities, research in extremity injury is becoming increasingly important (Lund and Ferguson, 1995). Lower extremity injuries, while generally not life threatening, can cause severe impairment and permanent disability. The pediatric population is especially sensitive to these injuries due to potential damage to growth plates and developmental delays during long recovery periods (Winthrop et al, 2005). Currently, little is known about the nature of pediatric lower extremity injuries. This area is lacking due to the deficiencies of pediatric Anthropomorphic Test Devices (ATDs) and the infrequency of pediatric Post Mortem Human Subject (PMHS) testing. The following two studies provide a basis for pediatric lower extremity investigation. In the first study, a pediatric ATD was subjected to knee bolster airbag deployments. The results indicated that long bone injury was possible due to axial tibia loads over 2.5 kN and bending moments over 70 Nm in certain seating positions. In addition, the study revealed important limitations of the ATD itself, such as insufficient instrumentation and the lack of biofidelity of the ankle joint. The results also highlighted the importance of using accurate injury threshold data for pediatric extremities. The second study addresses the need to develop injury criteria directly from pediatric tissue specimens. Pediatric tibiae will soon be available for testing, but the specimens will not be accompanied by surrounding musculature or the fibula. Adult PMHS studies have established that these structures affect the bending strength of the long bones (Kerrigan et al, 2003; Rupp et al, 2008). This study evaluates the difference in mechanical properties between adult tibiae with naturally attached musculature and fibulae vs. artificially attached musculature without fibulae. Three-point bend tests indicate that the artificial attachment of musculature and the absence of the fibula (open full item for complete abstract)

Committee: John Bolte IV (Advisor); Ajit Chaudhari (Committee Member) Subjects: Biomechanics; Mechanical Engineering