The capability to sense and respond to external mechanical stimuli at various timescales is essential to many physiological aspects in plants, including selfprotection, intake of nutrients and reproduction. Remarkably, some plants have evolved the ability to react to mechanical stimuli within a few seconds despite a lack of muscles and nerves. The fast movements of plants in response to mechanical stimuli have long captured the curiosity of scientists and engineers, but the mechanisms behind these rapid thigmonastic movements are still not understood completely.
Recrystallization is one of the most important physical phenomena in condensed matter that has been utilized for materials processing for thousands of years in human history. It is generally believed that recrystallization is thermally activated and a minimum temperature must be achieved for the necessary atomic mechanisms to occur. Here, using atomistic simulations, we report a new mechanism of dynamic recrystallization that can operate at temperature as low as T = 10 K in metals during deformation.
I am currently a M.Tech (Mechatronics, Department of Mechanical Engineering) student in IIT Patna. I have strong interests in Applied Mechanics with special focus on Dielectric Elastomer Actuators. I am expecting to graduate by May 2016. Currently i am working on dielectric elastomer actuators and want to continue this in my PhD also. Are there any opportunities for PhD positions available at Harvard Solid Mechanics? What are the essentials needed for the above.
Cracks generate the largest strain gradients that any material can withstand. Flexoelectricity (coupling between strain gradient and polarization) must therefore play an important role in fracture physics. Here we use a self-consistent continuum model to evidence two consequences of flexoelectricity in fracture: the resistance to fracture increases as structural size decreases, and it becomes asymmetric with respect to the sign of polarization. The latter phenomenon manifests itself in a range of intermediate sizes where piezo- and flexoelectricity compete.
Additive manufacturing (AM) has emerged as a powerful technique for manufacturing of various types of biomaterials and implants. Using AM, it is now possible to fabricate biomaterials with arbitrarily complex shapes at different scales. The inventory of biomaterials that can be used in this way continues to increase, extending the possible range of products and applications.
Adhesion between soft matter is a universal mechanical problem in bio-engineering and bio-integration. The Johnson–Kendall–Roberts (JKR) method is widely used to measure the work of adhesion and work of separationbetween soft materials.
When laminating a thin elastic membrane on a substrate with surface roughness, three scenarios can happen: 1) fully conformed, i.e., the membrane completely follows the surface morphology of the substrate without any interfacial gap; 2) partially conformed; and 3) nonconformed, i.e., the membrane remains flat if gravity is not concerned.
The composite strength of Reinforced Concrete which is a mixture of two main materials can be calculated by the formula given by Tsai : X=(vf+vm*Em/Ef)*Xf where vf is the fiber (steel) fraction and vm is the concrete (cement+sands+gravels) fraction. Xf is the yield strength of Steel and Xm is the compressive strength of the Concrete matrix. For the application case: vf=0.01911, vm=0.98089, Xf=270 MPa, Xm=40 MPa, Ef=207.000 GPa, Em=30.798 GPa we obtain X=44.563 MPa.
Under the actions of internal pressure and electric voltage, a spherical dielectric elastomer balloon usually keeps a sphere during its deformation, which has also been assumed in many previous studies. In this article, using linear perturbation analysis, we demonstrate that a spherical dielectric elastomer balloon may bifurcate to a nonspherical shape under certain electromechanical loading conditions.
EML Special Issue on 3D Assembly by Cutting, Bending and Folding
When patterned with different materials, gradients or cut-outs, thin structures such as sheets and rods can bend or fold either spontaneously or by actuation in response to a force or stimulus to form a pre-designed three dimensional structure. This special issue addresses the design and mechanics of these structures with a special emphasis on programmability and non-linearity.
The J-integral based criterion is widely used in elastic-plastic fracture mechanics. However, it is not rigorously applicable when plastic unloading appears during crack propagation. One difficulty is that the energy density with plastic unloading in the J-integral cannot be defined unambiguously.
Soft materials including elastomers and gels are pervasive in biological systems and technological applications. Whereas it is known that intrinsic fracture energies of soft materials are relatively low, how the intrinsic fracture energy cooperates with mechanical dissipation in process zone to give high fracture toughness of soft materials is not well understood. In addition, it is still challenging to predict fracture energies and crack-tip strain fields of soft tough materials.
After several years of research in the area of additive manufacturing, biofabrication, and additively manufactured biomaterials and implants, I finally put up the first version of the website of my lab. I will gradually improve the website, but there is already links to all publications coming out of my lab in the general area of AM.
Diabetic foot represents a complication of diabetes that can lead to foot ulcers and other serious conditions. 3D Finite Element (FE) analysis enables dynamic characterisation of different loads within the foot.
Flexoelectricity is an electromechanical effect coupling polarization to strain gradients. It fundamentally differs from piezoelectricity because of its size-dependence and symmetry. Flexoelectricity is generally perceived as a small effect noticeable only at the nanoscale. Since ferroelectric ceramics have a particularly high flexoelectric coefficient, however, it may play a significant role as piezoelectric transducers shrink to the sub-micrometer scale.