Ibrahim Guven, Ph.D.

Associate Professor, Department of Mechanical and Nuclear Engineering VCU College of Engineering

  • Engineering East Hall, Room E3234, Richmond VA

Professor Guven specializes in fracture and failure analysis using peridynamics.

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Spotlight

6 min

The Sky’s the Limit: Researching surface impacts to improve the durability of aircraft

Associate professor Ibrahim Guven, Ph.D. from the Department of Mechanical and Nuclear Engineering is conducting a research project funded by the Department of Defense (DoD) that explores building aircraft for military purposes and civilian transportation that can travel more than five times the speed of sound. Guven’s role in this project is to consider the durability of aircraft surfaces against elements such as rain, ice, and debris. His research group is composed of Ph.D. students who assist with the study and has collaborated with other institutions, including the University of Minnesota, Stevens Institute of Technology and the University of Maryland. Why did you get involved with this research project? The intersection of need and our interests decides what we research. I’m interested in physics and have been working on methods to strengthen aircraft exteriors against the elements for 12 years. We started with looking at sand particle impact damage, and then we graduated from that to studying raindrop impact because that’s a more challenging problem. Sand impact is not as challenging in terms of physics. A liquid and a solid behave differently under impact conditions. The shape of the raindrop changes prior to the impact due to the shock layer ahead of the aircraft. Researching this impact requires simulating the raindrop-shock layer interaction that gives us the shape of the droplet at the time of contact with the aircraft surface. Unlike with sand, analyzing raindrop impact starts at that point, which requires accurate modeling of the pressure being applied. As the aerospace community achieves faster speeds, there’s a need to understand what will affect a flight’s safety and the aircraft’s structural integrity. That need is what I’m helping to fulfill. Were there any challenges you and your research group faced while working on this study? How did you overcome them? Finding data was hard. I’m a computational scientist, meaning I implement mathematical differential equations that govern physics to write computer code that predicts how something will behave. My experiments are virtual, so to ensure that my models work well, I need experimental data for validation. However, conducting experiments on this problem is extremely challenging. That’s the roadblock. Currently, we refer to data from the seventies and eighties. Beyond that, this kind of information is not available. We are working to generate data that my computational methods need for their validation. An example is the nylon bead impact experiment. Some researchers found that if you shoot a nylon bead at a target, it leads to damage similar to that from a raindrop of the same size. It is much easier and cheaper to shoot nylon beads compared to the experiments involving raindrops. However, this similarity vanishes as we go into higher velocities. How do you typically gather data for a project of this nature? We are working with a laboratory under the U.S. Navy. They can accelerate specimens to relevant speeds, meaning they can shoot them into the air at the desired velocity. A colleague at Stevens Institute of Technology also came up with a droplet levitator. He uses acoustic waves emitted by tiny speakers to play a certain sound at a certain frequency to create enough air pressure to suspend droplets midair. To an untrained eye, it looks like magic. They levitate droplets and use a railgun to shoot our samples at the droplets. Our samples hitting the droplets are stand-ins for the aircraft surface material. Once this is done successfully, they shoot a sample with high-speed cameras that can take ten million frames per second. As a result, we get a good, high-fidelity picture of this impact event. That is the type of data I’m seeking, and this is how I get it from my collaborators. What was your overall experience working with the students in your research group? I like to think it was positive. I try to be a nice advisor and give them space to explore, fail, and bring their own ideas. Even if I feel like we’re at a dead-end, I step back and let them figure it out. My role is to help them grow. Teach them, train them and help them along the way. That’s the experience. Did you notice any personal changes in your students during this project? Yeah, I have. When they’re just out of their undergraduate programs, confidence is lacking sometimes. You see them become more sure of themselves as they learn more and more. Often, regardless of whether English is their native language or not, writing is a big issue for every student. How one presents ideas in written form is a persistent problem in engineering. I see the most growth in that area. Again, an advisor has to be a guide and also have patience. Eventually, after working on multiple paper drafts, I can see tremendous improvement. You must allow them to see their shortcomings. It’s important to work with students to refine how they frame a problem, explain it to a wide audience in concise terms, and use neutral language without leading them to certain conclusions. Why do you think that this research is important? Somebody has to do it, right? I believe that I’m the right person because of my background. Personally, I think if this research makes for safer travel conditions, and if I have something to offer, then why not? If we can accurately simulate what happens in these conditions, we can use our methods to test out designs for damage mitigation. For example, we can perform simulations with different surface materials for the aircraft to see if using a different material or layered coating system leads to less damage. In a bigger picture, we’re working on a very narrow problem in our field, but we don’t know how useful that’s going to be in 10, 15 or 30 years from now. Whatever we study and put out there in terms of publications, it may help some other researcher in a different context many years later. This could be space research, modeling an atmosphere on a different planet, or something that is related to our bodies. There are parts of physics in this problem that do not necessarily only apply to high-speed flight. It could be many different things. One has to understand that what is studied may seem obscure today, but because the universe is more or less governed by the same physics, everything should be put in a theoretical framework, done right and shared with the community. People may learn things that could become relevant in the future. It’s not uncommon. What is another subject that you plan to study? The next natural step is coming up with strategies to mitigate damage in these scenarios. If avoiding a risk is not an option, can we actually come up with a solution? We have to determine how to modify an aircraft’s design to prevent a catastrophe. Another extension of my research would be to examine the landing of spacecraft on dusty planetary bodies. During landing on Earth, aircraft approach and reach the ground very smoothly. On the other hand, a spacecraft comes down slowly and needs a lot of reverse propulsion for a soft landing. As it does, it kicks up a large amount of dust, which blows back and hits the spacecraft. Taking into account the damage that occurs due to particle impact is a direct connection to my work. This again is an open area, and because we have ambitions to have a permanent presence on dusty places like the moon and Mars, we have to nail down the concept of landing safely. That is where my research could help.

Ibrahim Guven, Ph.D.

2 min

Mission to Mars – Pack Light on Materials and Heavy on Innovation

On Tuesday May 09, the Humans to Mars Summit kicks off in Washington D.C. This will be a meeting of some of the most powerful, brilliant, creative, scientific and corporate minds on earth. Together they are working on a way that someday soon we will visit Mars. Since 2010 this expanding group is realizing that exploring the red planet is within their grasp and possible during our lifetime. To get there, it will take innovations in science, technology and engineering like we have not seen in generations. Virginia Commonwealth University’s School of Engineering is part of a team that is making this trip a reality. The NASA-sponsored multidisciplinary Space Technology Research Institute (STRI) is working on new a composite material that makes use of engineered carbon nanotubes and will be much lighter—but much stronger—than what is currently available. Space craft need to exit and re-enter atmospheres. To do so, they need to be strong or the results are disastrous. Space travel and the concept of exploring other planets is high science and not easy for most earthly mortals to comprehend. That’s where the experts at VCU’s School of Engineering can help. Ibrahim Guven, Ph.D., assistant professor in the VCU School of Engineering Department of Mechanical and Nuclear Engineering, is an expert on peridynamics, a branch of mechanics that looks at the effect of deformities and fractures. Peridynamics is essential to planning for space travel and to understanding what it takes to get from Earth to Mars. He can explain these concepts in a simple manner and is available to speak with media. Simply click on his profile to arrange an interview. Source:

Ibrahim Guven, Ph.D.

Media

Industry Expertise

Research
Education/Learning

Areas of Expertise

Fracture and failure analysis using Peridynamics
Impact and penetration mechanics
Finite element method
Boundary element method
Multi-scale modeling of physical phenomena
Micro/nano-scale testing and measurement techniques
Stress and failure analysis of electronic components
Fatigue reliability of solder joints in electronic packages

Education

University of Arizona

Ph.D.

Mechanical Engineering

2000

Middle East Technical University

M.S.

Engineering Sciences

1994

Middle East Technical University

B.S.

Civil Engineering

1991

Selected Articles

Drop-Shock Failure Prediction in Electronic Packages by Using Peridynamic Theory

IEEE Transactions on Components, Packaging and Manufacturing Technology

2012

Peridynamic (PD) theory is used to investigate the dynamic responses of electronic packages subjected to impact loading arising from drop-shock. The capability of the PD theory to predict failure is demonstrated by simulating a drop test experiment of a laboratory-type package. The failure predictions and observations are exceptionally similar. For the drop test simulation of a production-type package, the finite element method (FEM) and PD theory are coupled via a submodeling approach. The global modeling is performed using the FEM while the PD theory is employed for the submodeling and failure prediction. The analysis yielded the outermost solder joint as the critical joint, with failure at the interface between the solder and copper pad on the printed circuit board side.

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Simulations of Nanowire Bend Tests for Extracting Mechanical Properties

Theoretical and Applied Fracture Mechanics

2011

Mechanical properties of nickel nanowires are characterized based on the numerical simulations of bend tests performed with a customized atomic force microscope (AFM) and scanning electron microscope (SEM). Nickel nanowire specimens are subjected to bending loads by the tip of the AFM cantilever. The experimental force versus bending displacement curves are compared against simulations from finite element analysis and peridynamic theory, and the mechanical properties are extracted based on their best correlations. Similarly, SEM images of fractured nanowires are compared against peridynamic failure simulations. The results of this study reveal that nickel nanowires have significantly higher strengths than their bulk counterparts, although their elastic modulus values are comparable to bulk nickel modulus values.

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Predicting Crack Propagation with Peridynamics: A Comparative Stud

International Journal of Fracture

2011

The fidelity of the peridynamic theory in predicting fracture is investigated through a comparative study. Peridynamic predictions for fracture propagation paths and speeds are compared against various experimental observations. Furthermore, these predictions are compared to the previous predictions from extended finite elements (XFEM) and the cohesive zone model (CZM). Three different fracture experiments are modeled using peridynamics: two experimental benchmark dynamic fracture problems and one experimental crack growth study involving the impact of a matrix plate with a stiff embedded inclusion. In all cases, it is found that the peridynamic simulations capture fracture paths, including branching and microbranching that are in agreement with experimental observations. Crack speeds computed from the peridynamic simulation are on the same order as those of XFEM and CZM simulations. It is concluded that the peridynamic theory is a suitable analysis method for dynamic fracture problems involving multiple cracks with complex branching patterns.

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