A Multi-Point Loaded Piezocomposite Beam: Mechanics and Response to Harmonic Excitation

In this paper a multi-segment beam, in what is called an inertial four-point loaded configuration, is proposed and its dynamic response is analyzed. In this configuration, two symmetrical overhanging free segments extend beyond the pinned supports, and two tip masses are attached to these free segments yielding symmetrical inertial loading at the tips. By varying the configuration parameters of this multi-segment beam, such as support locations and tip loading, the dynamic response of the system can be significantly altered. The harmonically excited transverse vibration of a piezocomposite beam with four-point loaded boundary conditions is analyzed as a function of the support location and tip mass. Experimental data for several support locations is presented for validation of the analytical model and the predicted relationship between the system natural frequency, support locations, and tip masses. Comparisons are also made between the multi-point loaded cases and a reference cantilevered beam. The analytical and experimental results demonstrate that the natural frequency of a multi-point loaded beam can be continuously adjusted in a relatively wide range using the configuration changes investigated.

Model-Based Experimental Development of Passive Compliant Robot Legs from Fiberglass Composites

We report on the methodology of developing compliant, half-circular, and composite robot legs with designable stiffness. First, force-displacement experiments on flat cantilever composites made by one or multifiberglass cloths are executed. By mapping the cantilever mechanics to the virtual spring model, the equivalent elastic moduli of the composites can be derived. Next, by using the model that links the curved beam mechanics back to the virtual spring, the resultant stiffness of the composite in a half-circular shape can be estimated without going through intensive experimental tryouts. The overall methodology has been experimentally validated, and the fabricated composites were used on a hexapod robot to perform walking and leaping behaviors.

Blebbing Dynamics, Single Cell Force Measurements, and the Influence of Cytochalasin D on Glioblastoma Multiforme Cells Using STEP Fibers

Classified as a grade IV tumor of the central nervous system, Glioblastoma multiforme (GBM) arises from the glia. A poor understanding of tumor metastasis and limited treatment options have led to increase in deaths of patients suffering from GBM. Studying glioma behavior using aligned structures that mimic native glioblastoma metastatic path is challenging. In this study, we utilize a previously described non-electrospinning platform to manufacture aligned 3D structures called STEP nanonets that not only allows the study of individual cell-nanofiber interaction, but also allows the calculation of migratory forces using beam mechanics. In particular, the blebbing dynamics, force generation, and the effect of an actin disruptor, Cytochalasin D have been investigated on a glioma cell line (DBTRG, Denver Based Tumor Research Group). It was observed that cell pulled onto the nanofibers causing measurable deflections when they were in spread and non-blebbing conditions. In non-spread configurations while attached to fibers, the cells acquired spherical configurations and resumed blebbing. The average migratory force generated by cells exposed to DMSO (control, 1:1000 dilution) using nanonets of 2μm by 400nm fibers was 0.58±0.06nN. Actin disruptor, Cytochalasin D severely compromised the ability of the glioma cells to migrate causing no deflection of the fibers. Forces exerted by tumor cells on their native microenvironment affects their ability to metastasize, invade and proliferate. While the result presents actin disruptor as a potential target to minimize metastasis, the influence of other cytoskeleton disruptors can also be studied using the platform. Moreover, the results obtained from the study can be utilized to better understand the individual cell – nanofibers interaction which can shed light on how cells interact with their native environment during metastasis.

Research on Frictional Roller’s Strength of Endless-Rope Winch

The strength of friction roller for endless-rope winch is analyzed, and the unit beam mechanics model for friction rollers is established, the flexural deformation equations are derived base on relevant theoretical analysis and calculate. Meanwhile, the variation curves of the flexural solution and compression stress along with the direction of friction roller width are obtained by MATLAB software. Thereby provides the theoretical basis for design and selection of friction roller.