Post-buckling dynamics of spherical shells

We explore the intrinsic dynamics of spherical shells immersed in a fluid in the vicinity of their buckled state, through experiments and three-dimensional axisymmetric simulations. The results are supported by a theoretical model that accurately describes the buckled shell as a two-variable-only oscillator. We quantify the effective ‘softening’ of shells above the buckling threshold, as observed in recent experiments on interactions between encapsulated microbubbles and acoustic waves. The main dissipation mechanism in the neighbouring fluid is also evidenced.

Sub g Threshold Acceleration Sensor Incorporating Latched Bistable Beam

We present a concept and a theoretical feasibility study of a sub g threshold inertial micro sensor, which incorporates a curved bistable beam as a suspension element. For certain range of geometric parameters such a beam can exhibit lathing, namely remain in its switched configuration at zero actuating force. Since the device can be released from its latched state by an external acceleration force, it can therefore serve as a threshold inertial switch. While the snap-through force, associated with the switching from the initial to the buckled state, cannot be reduced without decreasing the frequency of the device, the release value of the acceleration can be tailored to be arbitrarily low. This allows design of a devices with sufficiently high stiffness in the initial and latched configurations, but with a very low release threshold. Our model show that for appropriately chosen parameters, it is possible to design a sub g threshold acceleration micro switch of realistic dimensions.

Behavior of Thin-Film-Type Delamination of Layered Composite in Post-Buckling

A revision of the basic assumptions those are usually used in the analysis of stability of thin delaminated layer and delamination propagation in a compressed composite is presented in this paper. For this purpose, the theory of flexible elastic plates with large displacements was used. As a result the compressive force and the total longitudinal strain of sub-laminate are expressed in terms of complete elliptic integrals, which uniquely identify the buckled shape of sub-laminate, the effect of buckling on the compression strain and increment of the compressive force in the buckled state. Stress and strain, as well as the strength of the buckled sub-laminate in the dangerous cross-section were also analyzed. The results of the general analysis of delamination propagation and its compression-bending destruction in the buckled state allow to define the basic regularities of the damage behavior of compressed layered composite.

Some Identities on Structural Flexibility after Buckling

Summary This paper gives some identities concerning the flexibility of certain elastic structures, including flat plates, at the onset of buckling and subsequently. The identities have a useful application in determining the flexibility and the rate of change of flexibility with load for structures in which the mode in the buckled state changes continuously with load.