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National Medal of Science

Submitted by Ken P. Chong on

The nomination of colleagues for awards is one of the most important and gratifying aspects of participating in the scientific community. Help celebrate the contributions of your colleagues by submitting a nomination for The National Medal of Science.

The National Medal of Science was established in 1959 as a Presidential Award to be given to individuals "deserving of special recognition by reason of their outstanding contributions to knowledge in the physical, biological, mathematical, or engineering sciences." In 1980 Congress expanded this recognition to include the social and behavioral sciences. The National Medal of Science is the highest honor the President bestows on scientists. A Committee of 12 scientists and engineers is appointed by the President to evaluate the nominees for the Award. Since its establishment, the National Medal of Science has been awarded to 425 distinguished scientists and engineers whose careers spanned decades of research and development.

Michael Petralia

Submitted by Michael T. Petralia on

I completed my undergraduate degree in Mechanical Engineering at The Cooper Union for the Advancement of Science and Art, in New York City. At the undergraduate level, I have taken two courses related to solid mechanics: Solid Mechanics and Stress & Applied Elasticity. Though these courses covered most of the same topics, the focus was not on working with developing the equations for different situations. The majority of the work was in knowing when to apply the equations and coming up with quantitative solutions. Thus my weaknesses will be related to coming up with equations to model various stress situations.

Concerning my research, I am working with Prof. Robert Wood in the microrobotics laboratory. My focus will be on aquatic robots on the order of several centimeters in length. Because of the restrictions inherent in working at this scale, it will be important not to over-design the systems. From studying solid mechanics, I hope to gain the ability to analyze the states of stress and strain in materials such that I can effectively develop efficient systems for microrobotics.

will adams

Submitted by Will Adams on

My name is Will Adams and I am a first year grad student in BME. I have no previous courses in solid mechanics or strength of materials but I have taken two fluid mechanics courses, ES220 and ES123, as an undergrad which contain many of the same lines of thinking. Hopefully the math formalisms of these classes will help in ES240 but having no solids background leaves me with little intuition about experimental results. Hopefully I can acquire this here. I was a BME major as an undergrad here in DEAS.

Adrian Podpirka

Submitted by Adrian Podpirka on

My name is Adrian Podpirka and I am a first year grad student studying applied physics. I came to Harvard after finishing my Bachelors in Material Science and Engineering at Columbia University. As an undergraduate I took Mechanics of Solids with Professor Xi Chen and Mechanical Properties of Materials with Professor Noyan.



Related to this course, my main weakness is the mathematics involved since it has been more then 3 years since I took differential equations. Also, both my undergraduate courses were not tensor based. My main strength in this course would be my understanding of material properties and the phenomenas involved.


My likely research direction will probably be in the field of fuel cell membranes with Professor Ramanathan.

Solid Mechanics Homework 11-15

Submitted by Zhigang Suo on

This set of homework relies on a few elementary facts of the algebra of vectors and tensors.  If you are vague about these facts, see some old notes I wrote when I taught ES 240 in 2006:  node/205/revisions/1385/view

11. Positive-definite elastic energy density

12. The coefficient of thermal expansion (CTE) is a second-rank tensor.

13. Hooke's law for anisotropic, linearly elastic solids

14. Invariants of a tensor

15. A "derivation" of the Mises (1913) yield criterion

Pushing Mechanics to the Up Front of Design

Submitted by Xiao-Yan Gong on

When a mechanical engineer and a material scientist were asked for the root cause of an in-vivo fracture. Mechanical engineer pointed to the loading and the material scientist pointed to the processing. While they both are correct, they both also missed the real ROOT cause, the design.

It is very common that medical device design engineers are so focused on the device functionality that often the very basic mechanics is overlooked. Lack of knowledge on the in-vivo environment (Design Requirements) is another subject to blame. However, it is common that even technology driven companies have gaps between design department and duarability deparment. Up front design engineers do not necessarily keep up with the fast paces of material advances. On the other hand, downstram subject matter experts, device tesing teams or often the R&D departments are not informed of design changes before the design is fixed. The problem is worse often in industrial leaders than in start-ups, but the sympton is the same, problem found in animal studies and/or clinical trials before they reached industrial subject matter experts.

Mechanics in Medical Implant Industry

Submitted by Xiao-Yan Gong on

The major challenge in medical implant industry is the knowledge about human body. Had we know the human body and its functions better, we can make better and reliable implants. Below are two examples that I have learned.

Let's start from stent, a small, lattice-shaped, metal tube that is inserted permanently into an artery. The stent opens the narrowed artery so that an adequate supply of blood can be restored. See this FDA site for further detail.

Stent has revolutionized the treatments for cardiovascular disease and the interventional system. However, stent fractures are commonly observed in-vivo in the past years and has become a concern for patient wellness and therefore a challenge/opportunity for mechanical engineering. Both the engineering and the medical care societies have to work together to solve this issue. It is very surprising that little publications are available to study the key issues such as artery deformation, motion, its mechanical properties and its variations among patient age, race, and other factors. As a result, current stents, even they have been proven to be lifesavers for many patients, they are not necessarily a satisfactory product for a mechanical engineer. We can not wait for the medical care society to give us the information because they often concern and focus on different issues than us. In addition, they can not work alone to come up with the necessary equipments. Therefore, we need proactive to interact and help each other to get what we want. The day we know our interventional system better is the day that we can make better stents because stents can only be as good as our knowledge to the interventional system.

University of Michigan, tenure-track faculty positions

Submitted by Xuanhe Zhao on

 University of Michigan, tenure-track faculty positions

The Department of Mechanical Engineering, University of Michigan, Ann Arbor, invites applications for tenure-track faculty positions in various areas of mechanical engineering including design and manufacturing, dynamics, systems and controls, materials and solid mechanics and thermal/fluid sciences. Candidates with research interests in automotive engineering, biotechnology, eco/sustainable systems, energy-systems, manufacturing, and micro/nano systems are particularly encouraged to apply.

Applicants should have an earned Ph.D. in Mechanical Engineering or related fields, a demonstrated record for conducting independent research, and the potential for leadership and impact in teaching and research. Appointments at all levels will be considered. For best consideration, candidates should apply by February 28, 2007, but the positions will remain open until filled.

Prediction of femoral head collapse in osteonecrosis

Submitted by Konstantin Volokh on

OSTEONECROSIS is the death of bone that results in the collapse of the bony structure, leading to joint pain, bone destruction, and loss of function. Destruction of the bone frequently is severe enough to require joint replacement surgery. Osteonecrosis is a common disorder and accounts for 10% or more of the 500,000 total joint replacement procedures performed annually in the United States. Approximately 75% of patients with osteonecrosis are between 30 and 60 years of age.

From the point of view of mechanics, osteonecrosis means deterioration of mechanical properties of the bone. Decrease of the magnitude of the elastic modulus of the bone leads to its inability to bear the external load and culminates in bone damage and fracturing. For a couple of decades the engineers were trying to estimate the critical stress-strain state of the femoral head using the available data on the osteonecrotic bone properties, finite element analysis based on 3D elasticity, and Von Mises stress as a criticality condition. The fact that the cortical shell of the femoral head is significantly stiffer than the underlying cancellous bone did not attract much attention yet. However, from the solid mechanics point of view the difference in the stiffness of the cortical and cancellous parts of the femoral head under both normal and necrotic conditions is important. This difference allows for considering the femoral head as an elastic cortical shell on an elastic cancellous foundation. This, in its turn, suggests the buckling of the cortical shell as a possible starting point of the overall head collapse. The purpose of the study, described here, was to assess the cortical shell buckling scenario as a possible mechanism of the femoral head collapse at the various stages of osteonecrosis.