Grain size effects in the forming of ultra-thin sheets
Introduction The number of micro scale applications of metals is growing rapidly. Progressive miniaturization has become a decisive characteristic of developments in electronic devices (Figure 1) or electronically controlled mechanical systems. Along with the miniaturization so-called size effects occur in sheet metal manufacturing processes. These effects are assumed to be caused by changes in the relative contribution of the different micro-structural events.
A crystallographic model for the study of local deformation processes in polycrystals
Abstract Most engineering materials possess a polycrystalline structure. Under load the anisotropy of the constituent grains leads to strong inhomogeneities of stresses and strains on the grain level. In order to investigate the local deformation processes, a new crystallographic model for pure fcc metals in the low temperature range has been developed. It is based on the framework of crystal plasticity and uses the finite element method (FEM). The rate dependent constitutive equations consider isotropic as well as kinematic hardening, whereby the mutual interactions of dislocation processes on the different slip systems are taken into account. Comprehensive calculations show that the essential features of both single crystals—which serve as a test object for the constitutive equations—and polycrystals are reproduced correctly. Moreover the simulations allow a deeper understanding of the mechanisms that control the local deformation behaviour of metals, especially of the mutual interactions of slip system activity, local hardening and resulting local strain. Furthermore, the model may serve as a physically motivated base for a later inclusion of damage terms which allow investigations of damage and fatigue on the local scale.
The Analysis on Fire Smoke Exhausting Robot Vibration Based on Wavelet Transform
Belt relaxation, which affects a lot on operation reliability of the fire smoke exhausting robot, is hard to detect. In this paper, a new method for belt relaxation feature recognition based on continuous wavelet transform (CWT) is proposed, and a vibration model which simplified the robot as a 2-dof forced vibration system under harmonic excitation is established. The vibration acceleration signal has been collected using the IEPE sensor and data acquisition card, experimental results verified the accuracy of the vibration model, and weak impact signal caused by the belt relaxation was distinguished, that testify the practicability of the CWT method in belt relaxation feature recognition.