Prompt Determination of the Mechanical Properties of Industrial Polypropylene Sandwich Pipes

A simple and prompt method to determine the mechanical properties of industrial multilayer extrusion polypropylene pipes for a gravity sewer network is suggested. The engineering formulas included for calculating the permissible thickness and relative position of a foam core in the pipes are based on a linear-elastic approximation and the rule of mixtures. The applicability of the approximation was justified experimentally during investigation of the effective tensile characteristics of single- and multilayer pipes and each layer specimen by using traditional tests and finite-element calculations. The results obtained were used to formulate engineering recommendations for calculations of this type.

FFT-Based Numerical Method for Non-Linear Elastic Contact

Based on FFT, a numerical method suitable for elastoplastic and hyperelastic frictionless contact is proposed in this paper, which can be used to solve 2D and 3D contact problems. The non-linear elastic contact problem is transformed to linear elastic contact considering residual deformation (or equivalent residual deformation). Numerical simulations for elastic, elastoplastic and hyperelastic contact between hemisphere and rigid plane are compared with the results of finite element method (FEM) to verify the accuracy of the numerical method. Compared with the existing elastoplastic contact numerical methods, the calculation efficiency is improved while ensuring a certain calculation accuracy (pressure error does not exceed 15% while calculation time does not exceed 10 minutes in a 64×64 grid). For hyperelastic contact, the proposed method reduces the dependence of the approximation result on load as in linear elastic approximation. Despite a certain error, the simplified numerical method shows a better approximation result than linear elastic contact approximation, which can be used for the fast solution in engineering applications. Finally, taking the sealing application as an example, the contact and leakage rate between 3D complicated rough surfaces are calculated.

Nπ scattering in the Roper channel

We present results from our recent lattice QCD study of Nπ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance N*(1440) resides in experiment. Using a variety of hadron operators, that include qqq-like, Nπ in p-wave and Nσ in s-wave, we systematically extract the excited lattice spectrum in the nucleon channel up to 1.65 GeV. Our lattice results indicate that Nπ scattering in the elastic approximation alone does not describe a low-lying Roper. Coupled channel effects between Nπ and Nππ seem to be crucial to render a low-lying Roper in experiment, reinforcing the notion that this state could be a dynamically generated resonance. After giving a brief motivation for studying the Roper channel and the relevant technical details to this study, we will discuss the results and the conclusions based on our lattice investigation and in comparison with other lattice calculations.

Cross-Sectional Deformation in Multi-Walled Carbon Nanotubes under Hydrostatic Pressure

This contribution provides simulated results of cross-sectional deformations observed in carbon nanotubes under high pressure. Molecular dynamics (MD) simulations were performed to explore radial buckling characteristics of multi-walled carbon nanotubes, and confirmed a variety of large-amplitude deformation modes. The energetically stable deformation mode turned out to be strongly dependent on the diameter of the innermost tube and the number of concentric walls. Critical buckling pressure obtained by MD simulations was compared with that estimated from a continuum elastic approximation, by which the validity of the continuum approximation was assessed.

KALEIDOSCOPIC MODE CHANGE IN CROSS-SECTIONAL DEFORMATION OF REINFORCED CARBON NANOTUBES

Cross-sectional deformation of multiwalled carbon nanotubes under isotropic radial pressure is investigated in a realm of continuum elastic approximation. The nanotube we assumed is subjected to the embedment into an elastic medium and stiffener insertion into the core cavity. Combination of the two reinforcement manipulations is found to cause kaleidoscopic mode changes in the radial corrugation, in which the cylindrical walls exhibit wavy patterns along the circumferential direction. Physical consequences of the diverse corrugation patters are also discussed.

Atomic Paths in Scanning of the AFM Tip above the Close-Packed Surface in Repulsive Mode

The paths are calculated for the surface and tip apex atoms when scanning the AFM tip above the close-packed lattice in contact mode. The interaction of the sample and the tip atoms is considered in elastic approximation. The dependence of the atomic paths on the type of the tip and its orientation is investigated. It is shown that the vertical characteristic sizes of the atomic paths are several times larger than the vertical resolution of the atomic force microscope.