Simulations of thermoelastic triangular cell lattices with bonded joints by finite element analysis

AbstractThermoelastic triangular cell lattices composed of bi-material curved ribs were designed and analyzed by finite element simulation. Positive, negative, or zero thermal expansion was possible by varying rib curvature if joints can pivot freely, as expected. Welded or bonded joints result in nonzero expansion but smaller in magnitude than that of a constituent material having higher thermal expansion coefficient. The effects of rib curvature variation for bonded joints were found to be negligible. Rib slenderness for both joints did not influence the coefficient of thermal expansion. We present a square lattice with bonded joints that has zero net thermal expansion; each curved bi-material rib has zero expansion

Post-yield Relaxation Behavior of Bovine Cancellous Bone

Relaxation studies were conducted on specimens of bovine cancellous bone at post-yield strains. Stress and strain were measured for 1000 s and the relaxation modulus was determined. Fifteen cylindrical, cancellous bone specimens were removed from one bovine femur in the anterior–posterior direction. The relaxation modulus was found to be a function of strain. Therefore cancellous bone is non-linearly viscoelastic/viscoplastic in the plastic region. A power law regression was fit to the relaxation modulus data. The multiplicative constant was found to be statistically related through a power law relationship to both strain (p \u3c 0.0005) and apparent density (p \u3c 0.0005) while the power coefficient was found to be related through a power law relationship, E(t, ε)= A(ε)t-n(ε), to strain (p \u3c 0.0005), but not apparent density

Quantification of Collagen Organization Using Fractal Dimensions and Fourier Transforms

Collagen fibers and fibrils that comprise tendons and ligaments are disrupted or damaged during injury. Fibrillogenesis during healing produces a matrix that is initially quite disorganized, but remodels over time to resemble, but not replicate, the original roughly parallel microstructure. Quantification of these changes is traditionally a laborious and subjective task. In this work we applied two automated techniques, fast Fourier transformation (FFT) and fractal dimension analysis (FA) to quantify the organization of collagen fibers or fibrils. Using multi-photon images of collagen fibers obtained from rat ligament we showed that for healing ligaments, FA differentiates more clearly between the different time-points during healing. Using scanning electron microscopy images of overstretched porcine flexor tendon, we showed that combining FFT and FA measures distinguishes the damaged and undamaged groups more clearly than either method separately

Damping properties of lead metaniobate

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Viscoelastic behavior of 80In15Pb5Ag and 50Sn50Pb alloys: Experiment and modeling

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Stable extremely-high-damping discrete viscoelastic systems due to negative stiffness elements

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Logarithmic pulse generator for long-term creep and relaxation testing

This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder