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How should one compare material fatigue strength in thin film area?

Submitted by Yunfei Ma on

For several common electroplated materials: Ni, Cu, Au and Al, which one has strongest fatigue strength? We know the mechanical properties of thin films are different with their bulk counterparts due to the so called "size effect", and material properties depends largely on the microstructure and processing technique. But is there some mateiral laws or guidelines for designers to choose the "best material" as for fatigue resistant? Yield limit? ultimate tensile strength? or elongation? How could one compare material candidates without doing time-consuming test?

What are the criteria for the decomposition of the total strain into elastic and plastic parts?

Submitted by Kamyar M Davoudi on

We know that total strain is the symmetric part of the displacement gradient. Total strain can be represented by the sum of the elastic and plastic (eigen) strains. Let consider a dislocation in an arbitrary solid. Suppose we computed the displacement filed, therefore the total strain can be obtained immediately. What are the criteria for the decomposition of the total strain into elastic and plastic parts?

 

Academic Positions in the Department of Mechanical Engineering, Curtin University Sarawak

Submitted by Aaron Goh on
Applications are invited for full-time, continuing academic positions in a number of areas in the Department of Mechanical Engineering, Curtin University Sarawak.
Please see website for information : www.curtin.edu.my

Nice and low-cost introductory texts

Submitted by Konstantin Volokh on

There are two very nice companion texts on continuum mechanics and nonlinear elasticity printed by Dover recently: "Continuum mechanics" by Spencer and "An introduction to the theory of elasticity" by Atkin and Fox. Great and fairly affordable reading!

Noncovalent bonds dictate cell rheology

Submitted by Ning Wang on

Over the last ten years, a peculiar behavior of living cells is revealed: their modulus increases weakly with loading frequency (the so-called weak power law behavior) (for a pure elastic solid, the slope is 0; for a viscous fluid, the slope is 1).  The underlying mechanism is not clear at all; although a phenomenological soft glass rheology model (a model based on a disordered structure system) has been proposed, it cannot explain the multi-power laws at different loading frequencies (see Stamenovic et al, Biophys J Letter, 2007). 

The Change of Microstructure at low temperature

Submitted by Shaomin Xiong on
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Recently, we do some work about the dynamic strain aging. In order to investigate the function of solute clouds and precipitates in DSA, we do some experiments. The solution treated LY12 alloys are tested on MTS at low temperature (173K), and the Portevin-Le Chatelier phenomenon disappeared as we expected. But, we need more information about the change of microstructure under the low temperature, what is more the micro-optical observation should be finished in a very short time when we consider the effect of natural aging. Obviously the TEM can not meet our needs.

Equilibrium and stability of dielectric elastomer membranes undergoing inhomogeneous deformation

Submitted by Tianhu He on

Dielectric elastomers are capable of large deformation subject to an electric voltage, and are promising for uses as actuators, sensors and generators. Because of large deformation, nonlinear equations of state, and diverse modes of failure, modeling the process of electromechanical transduction has been challenging.  This paper studies a membrane of a dielectric elastomer deformed into an out-of-plane, axisymmetric shape, a configuration used in a family of commercial devices known as the Universal Muscle Actuators. 

Recommending a book on FSI with recent discussion on Immersed Boundary/Continuum Methods

Submitted by xwang on

I am writing to recommend my book “Fundamentals of Fluid-Solid Interactions-Analytical and Computational Approaches” recently published by Elsevier Science.  The book is available in amazon.com webpage  or Elsevier Science webpage.  The following is