Hardening condition of unsaturated polyether from alcoholysis products of secondary polyethylene terephthalate

The technological parameters of the curing of unsaturated polyesters synthesized on the basis of alcoholysis products of secondary polyethylene terephthalate and used in the production of fiberglass pipes have been studied. It is shown that unsaturated polyesters synthesized on the basis of alcoholysis products can completely substitute imported resins of 196 and 196A grades in the production of fi berglass pipes.

Modal Coupling Effect in a Novel Nonlinear Micromechanical Resonator

Capacitive micromechanical resonators share electrodes with the same bias voltage, resulting in the occurrence of electrostatic coupling between intrinsic modes. Unlike the traditional mechanical coupling, the electrostatic coupling is determined by the structural electric potential energy, and generally, it only occurs when the coupling modes operate in nonlinear regions. However, previous electrostatic coupling studies mainly focus on the stiffness softening region, with little attention on the opposite stiffness hardening condition. This paper presents a study on the electrostatic modal coupling effect in the stiffness hardening region. A novel capacitive micromechanical resonator with different modal nonlinearities is designed and fabricated. It is demonstrated that activating a cavity mode can shift the fundamental resonance of the manipulated mode by nearly 90 times its mechanical bandwidth. Moreover, the frequency shifting direction is found to be related to the manipulated mode’s nonlinearity, while the frequency hopscotch is determined by the cavity mode’s nonlinearity. The electrostatic coupling has been proven to be an efficient and tunable dynamical coupling with great potential for tuning the frequency in a wide range. The modal coupling theory displayed in this paper is suitable for most capacitive resonators and can be used to improve the resonator’s performance.

Friction-Stir Welding of Work-Hardened Al-Mg Alloy with Nanoscale Particles

In this work, feasibility of friction-stir welding (FSW) for joining of heavily deformed 5083 aluminum alloy was studied. To produce work hardening condition, the commercially available material was homogenized to precipitate strengthening particles and then subjected to equal-channel angular pressing (ECAP) at 300 °C to a true strain of ~12 via BCroute and successive rolling at the same temperature to 80 pct. of thickness reduction. Despite the subsequent FSW resulted in significant microstructural changes in stir zone, joint efficiency was found to be 98 pct.

Stress Measurement at Loaded Aluminium Welds Using Diffraction Methods

Aluminium alloys welded with arc welding and electron beam welding processes were investigated to analyse the local deformation behaviour under static loads. Therefore strain measurements were carried out. These investigations were combined with X-ray diffraction experiments which should provide information about the residual stress condition and additionally about load-induced changes of the hardening condition. Additionally diffraction experiments using synchrotron and neutron radiation where carried out to analyse the deformation behaviour of particular welds under varying static loads.

Microstructures and Properties of Cu-Cr-Y Alloy after Cold Worked and Aging

The influence of cold-worked and aging processes on the microstructures, mechanical properties and conductivity of Cu-Cr-Y alloy has been experimentally investigated. Samples were cut from ingot of Cu-0.8 wt.%Cr-0.05 wt.%Y alloy. They were solution-treated, cold rolled and aging treated. The results show that the Cu-Cr-Y alloy, with 70% deformation and aging at 480°C for 24min, can reach an excellent combination of microhardness and conductivity. The microhardness and conductivity is about 143HV and 84%IACS, respectively. The microstructures by transmission electron microscopy (TEM) show that the fine and dispersed distributed Cr precipitate, which form due to decomposition of the supersaturated solid solution during aging, is responsible for the peak maximum microhardness as it is predominantly present in the peak aged hardening condition.

The Asymptotic Elastic-Viscoplastic Field at Mode I Dynamic Propagating Crack-Tip

The viscosity of material is considered at propagating crack-tip. Under the assumption that the artificial viscosity coefficient is in inverse proportion to the power law of the plastic strain rate, an elastic-viscoplastic asymptotic analysis is carried out for moving crack-tip fields in power-hardening materials under plane-strain condition. A continuous solution is obtained containing no discontinuities. The variations of the numerical solution are discussed for mode I crack according to each parameter. It is shown that stress and strain both possess exponential singularity. The elasticity, plasticity and viscosity of material at the crack-tip only can be matched reasonably under linear-hardening condition. The tip field contains no elastic unloading zone for mode I crack.