9 research outputs found
Influence of manufacturing shrinkage and microstructural features on the strength properties of carbon fibers/PEEK composite material
This research discusses the micromechanical modelling for thermoplastic composite material. Elastoplastic and damage model for PEEK matrix composite with the dependency of properties to stress state is presented. Plasticity initiation conditions and failure criterion are analyzed. The influence of manufacturing residual stresses is considered. All typical engineering experiments for neat PEEK under different stress state are good predicted by the model. Numerical experiment for macro-properties estimation based on micromechanical model is conducted and the results are compared with the test data
Studies of seismic effects on snow stability on mountain slopes
Studies of seismicity caused by technological explosions at mines in the Khibini Mountains and its influence on snow stability and avalanche releases began five years ago. First quantitative assessments of such influence were obtained during this time. It has been shown that there is a statistically significant correlation between seismic events and avalanche releases. Special seismic measurements to evaluate shaking effects of explosions have been carried out. The most interesting results of the measurements are described. At least two factors caused by shaking decrease snow stability-1) Inertia (decreases friction and increases downhill force), and 2) Snow strength decrease. Deterministic and stochastic models describing the influence of the first factor are presented. A shaking table designed to study seismic influence on snow shear strength, as well as first results obtained with it, are described. Directions of future studies are outlined. The work was supported by RFBR grants: 04-05-65057-a; 05-05-64037-a; 05-05-64368-a
A method for rapid estimation of residual stresses in metal samples produced by additive manufacturing
The mechanical methods for measuring residual stresses typically rely on so-called destructive techniques where some stress components can be determined based on part deflection after material removal (cutting, etching, drilling, etc.). While these methods don't provide a comprehensive representation of residual stresses within the entire part, they can be readily applied in most manufacturing labs. In this study, we propose an efficient method for determining residual stress within additively manufactured cylindrical samples of stainless steel. The method is based on the assumption of a relation between the axial component of residual stress (normal to cross-section) and the cylinder radius. The general form of this relation is proposed based on data from numerical simulations using linear, parabolic or piecewise approximations. The parameters for the proposed relation are defined using equilibrium equations for total force and moment. The proposed method relies on an experiment with a mechanical cut along the cylinder. Consequently, the deflection of the cylinder halves after the cut allows for obtaining the equivalent bending moment
Anisotropy of Mechanical Properties and Residual Stress in Additively Manufactured 316L Specimens
In the presented study, LPBF 316L stainless steel tensile specimens were manufactured in three different orientations for the analysis of anisotropy. The first set of specimens was built vertically on the build platform, and two other sets were oriented horizontally perpendicular to each other. Tensile test results show that mean Young’s modulus of vertically built specimens is significantly less then horizontal ones (158.7 GPa versus 198 GPa), as well as yield strength and elongation. A role of residual stress in a deviation of tensile loading diagrams is investigated as a possible explanation. Simulation of the build process on the basis of ABAQUS FEA software was used to predict residual stress in 316L cylindrical specimens. Virtual tensile test results show that residual stress affects the initial stage of the loading curve with a tendency to reduce apparent Young’s modulus, measured according to standard mechanical test methods