Engineering Science and Materials Commons^™

Stress Analysis Of Ramberg-Osgood And Hollomon 1-D Axial Rods, Ronald J. Giardina Jr

University of New Orleans Theses and Dissertations

In this paper we present novel analytic and finite element solutions to 1-D straight rods made of Ramberg-Osgood and Hollomon type materials. These material models are studied because they are a more accurate representation of the material properties of certain metals used often in manufacturing than the simpler composite linear types of stress/strain models. Here, various types of loads are considered and solutions are compared against some linear models. It is shown that the nonlinear models do have manageable solutions, which produce important differences in the results - attributes which suggest that these models should take a more prominent place …

Creep, Fatigue And Creep-Fatigue Interactions In Modified 9% Cr - 1% Mo (P91) Steels, Valliappa Kalyanasundaram

Graduate Theses and Dissertations

Grade P91 steel, from the class of advanced high-chrome ferritic steels, is one of the preferred materials for many elevated temperature structural components. Creep-fatigue (C-F) interactions, along with oxidation, can accelerate the kinetics of damage accumulation and consequently reduce such components' life. Hence, reliable C-F test data is required for meticulous consideration of C-F interactions and oxidation, which in turn is vital for sound design practices. It is also imperative to develop analytical constitutive models that can simulate and predict material response under various long-term in-service conditions using experimental data from short-term laboratory experiments. Consequently, the major objectives of the …

Analysis Of Bolted Joints Under Medium And High Impact Loading, Deepak Sankar Somasundaram, Mohamed Trabia, Brendan J. O'Toole

College of Engineering: Graduate Celebration Programs

• Develop test fixture for medium impact study on bolted joints
• Create FEA model that can replicate the experiment
• Develop test fixture for high impact loading
• Create FEA model and select material properties that can produce results that
  closely match experiments.
• Compare different modeling techniques for high impact loading

Plastic Deformation Of Astm A36 Steel Using Two-Stage Light Gas Gun, Shawoon Kumar Roy

College of Engineering: Graduate Celebration Programs

To characterize material deformation in high velocity impact. To validate material models for computation simulation purposes.

This ongoing research is an attempt to study the plastic deformation of A36 steel plate (0.5” thick) under hypervelocity impact. Plastic deformation of the target plate was simulated using finite element software LS-DYNA.

A Resistance Based Structural Health Monitoring System For Composite Structure Applications, Dennis N. Boettcher

Master's Theses

This research effort explored the possibility of using interwoven conductive and nonconductive fibers in a composite laminate for structural health monitoring (SHM). Traditional SHM systems utilize fiber optics, piezoelectrics, or detect defects by nondestructive test methods by use of sonar graphs or x-rays. However, these approaches are often expensive, time consuming and complicated.

The primary objective of this research was to apply a resistance based method of structural health monitoring to a composite structure to determine structural integrity and presence of defects.

The conductive properties of fiber such as carbon, copper, or constantan - a copper-nickel alloy - can be …

Finite Element Modeling Of Ballistic Impact On A Glass Fiber Composite Armor, Dan M. Davis

Master's Theses

Finite Element Modeling of Ballistic Impact on a Glass Fiber Composite Armor

Dan Davis

Experiments measuring the ballistic performance of a commercially available fiberglass armor plate were used to guide the development of constitutive laws for a finite element model of the impact. The test samples are commercially available armor panels, made from E-glass fiber reinforced polyester rated to NIJ level III. Quasi-static tensile tests were used to establish material properties of the test panels. These properties were then used to create models in the explicit finite element code LSDYNA.

Ballistic impact testing of the panels was conducted using a …

Peridynamic Model For Dynamic Fracture In Unidirectional Fiber-Reinforced Composites, Wenke Hu, Youn Doh Ha, Florin Bobaru

Department of Mechanical and Materials Engineering: Faculty Publications

We propose a computational method for a homogenized peridynamics description of fiber-reinforced composites and we use it to simulate dynamic brittle fracture and damage in these materials. With this model we analyze the dynamic effects induced by different types of dynamic loading on the fracture and damage behavior of unidirectional fiber-reinforced composites. In contrast to the results expected from quasi-static loading, the simulations show that dynamic conditions can lead to co-existence of and transitions between fracture modes; matrix shattering can happen before a splitting crack propagates. We observe matrix–fiber splitting fracture, matrix cracking, and crack migration in the matrix, including …

Experimental Verification Of The Linear Relationship Between Stress And The Reciprocal Of The Peak Barkhausen Voltage In Astm A36 Steel, Orfeas Kypris, Ikenna Nlebedim, David Jiles

Orfeas Kypris

This study presents an experimental validation of a model theory for determining the relationship between a nondestructive measurement parameter and a property of interest. It was found that the reciprocal of the peak envelope amplitude of the Barkhausen emission voltage follows a linear relationship with stress. A linear relationship between stress and the reciprocal of the root mean square voltage was also obtained. These observations represent an important step towards improving the use of Barkhausen signals for magnetic non-destructive evaluation of stress as a function of depth in ferromagnetic load bearing structures.

The Effects Of Damage Arrestment Devices In Composite Plate Sandwiches With Fastener Holes, Mark Anderson, Nancy Hung Choy, Lacey Jones, Rita Kourskaya

Aerospace Engineering

Composite materials such as a carbon fiber are used in a variety of new technologies including aircraft, spacecraft, and motor vehicles. Carbon fiber has a high strength to weight ratio, a key advantage over other material options. This report discusses the use of composite damage arrestment devices (DADs) in composite sandwich panels with a foam core. There are three different curing cycles tested for the DADs: pressure only, vacuum only, and vacuum with 1000 lbs of pressure. Using a Tetrahedron Heat Press to cure the composite specimen and an Instron Machine to perform tensile testing, data was collected for each …

Design, Fabrication, Structural Testing, And Numerical Analysis Of A Small Scale Composite Wing, Jacob David Gaunt, Juan Carlos Flores, Vincent Andrew Perry

Aerospace Engineering

A small scale composite wing based on a design found on an experimental aircraft was designed, constructed, and tested dynamically and statically. The wing was constructed similarly to an experimental aircraft wing. The performed static test was intended to produce pure bending. Strain gages were used to measure strains on the wing structure. The strains were converted to stresses to aid in analysis. The static test results suggested that the wing was actually under torsion. Four structural modes were found from the static test. A finite element analysis model was made to compare experimental results to numerical analytical results. The …

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

Multiscale Transformation Field Analysis Of Progressive Damage In Fibrous Laminates, Yehia Bahei-El-Din, Ritesh Khire, Prabhat Hajela

Centre for Advanced Materials

As part of an ongoing effort to model uncertainty propagation across multiple scales in fibrous laminates, this paper presents a deterministic transformation field analysis for modeling damage progression under membrane forces and bending moments. In this approach, equivalent eigenstresses are computed in the phases and/or plies such that their respective stress components that satisfy the underlying failure criteria are reduced to zero. Superposition of the solutions found for the undamaged laminate under applied loads and under the eigenstress field provide the entire response. Failure criteria are based on stress averages in the fiber and matrix. Damage mechanisms considered are frictional …

Modified Sandwich Structures For Improved Impact Resistance Of Wind Turbine Blades, Yehia Bahei-El-Din, Mostafa Shazly, I. El-Habbal, Y. Elbahy

Centre for Advanced Materials

Wind turbine blades are susceptible to damage due to fatigue as well as impact by flying objects and parts broken off failed blades of nearby wind towers. Localized, permanent compression of the foam core and delamination of the fibrous composite face sheets are typical damage modes and can lead to progressive structural failure. Sandwich structures modified by inclusion of flexible polyurethane (PU) layers within the cross section are examined under both impact and dynamic loads. Finite element models of sandwich structures with conventional and modified designs show that sandwich designs modified with PU interlayes exhibit reduced foam core crushing and …

Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Multiscale computational techniques play a major role in solving problems related to viscoelastic composite materials due to the complexities inherent to these materials. In the present work, a numerical procedure for multiscale modeling of impact on heterogeneous viscoelastic solids containing evolving microcracks is proposed in which the (global scale) homogenized viscoelastic incremental constitutive equations have the same form as the local scale viscoelastic incremental constitutive equations, but the homogenized tangent constitutive tensor and the homogenized incremental history dependent stress tensor depend on the amount of damage accumulated at the local scale. Furthermore, the developed technique allows the computation of the …

Development Of Low Temperature Alpha Alumina Coatings By Ac Magnetron Sputtering, Andrew Cloud

Mechanical Engineering Undergraduate Honors Theses

Alpha-phase aluminum oxide thin films were created using an Isoflux ICM-10 dual target inverted cylindrical magnetron sputtering system using mid-frequency AC power supplies. Alpha alumina films were deposited at a magnetron power of 6 kW, 50% oxygen partial pressure by volume, and -35 V DC bias. Film thickness, substrate material, and position and orientation within the deposition chamber were varied. To ensure the deposition conditions are suitable for alloys, the substrate temperature was measured using temperature indicating liquids. The experimental results, supported by Explicit Euler numerical analysis, revealed a steady state temperature of ~480°C at 6kW. Transmission electron microscopy (TEM) …

Residual Stress Characterization In Structural Materials By Destructive And Nondestructive Techniques, Ajit K. Roy, Anand Venkatesh, Vikram Marthandam, Satish Dronavalli, Douglas P. Wells, Ronald Rogge

Mechanical Engineering Faculty Research

Transmutation of nuclear waste is currently being considered to transform long-lived isotopes to species with relatively short half-lives and reduced radioactivity through capture and decay of minor actinides and fission products. This process is intended for geologic disposal of spent nuclear fuels for shorter durations in the proposed Yucca Mountain repository. The molten lead-bismuth-eutectic will be used as a target and coolant during transmutation, which will be contained in a subsystem vessel made from materials such as austenitic (304L) and martensitic (EP-823 and HT-9) stainless steels. The structural materials used in this vessel will be subjected to welding operations and …

Comparative Study Of Lightweight And Normal Weight Concrete In Flexure, Mohammad Zareh

Dissertations and Theses

This investigation represents a comparative study of the flexural behavior of lightweight and normal weight concrete. Both theoretical and experimental moment-curvature characteristics of the tested specimens were used to study the flexural behavior.

A generalized computer program to determine the moment-curvature relationships of a singly reinforced rectangular concrete beam was developed.

For this limited study it was observed that lightweight concrete beams when compared to normal concrete beams achieve comparable moment capacity (about 92% of normal weight concrete) but exhibit higher deflections (about 40% more than normal weight concrete).

Concrete In Dairies, D Roger Buchanan

Journal of the Department of Agriculture, Western Australia, Series 4

PRIME requirements for exposed concrete surfaces in dairies are that they should be easily cleansed and should not deteriorate in contact with milk and milk products.

In milking stalls, animal races and on loading platforms hardwearing surfaces which offer good foothold are also necessary.