Nowadays, dental filling materials with fizionomic properties are mostly used in dental care. Due to this, more and more products, which we know quite little about, appear on the market. During the curing process they all have certain polymerization shrinkage. Most of the dental practitioners believe that polymerization shrinkage is the causing mechanism of poor marginal adaptation between the two surfaces (tooth-filling material), ultimately leading to micro leakage and appearance of secondary caries lesions. Although this misconception is in clear contradiction with the facts experienced...
More and more optical 3d deformation measurement systems are used to analyse material and component behaviour. Obvious advantages in the analyses - especially at high strain deformation states, where nonlinearity caused by material behaviour and kinematics, anisotropy or inhomogeneity plays a role - are pushing these methods. Nevertheless DIC-based systems only serve to observe surfaces of specimens or components. For the determination of a full 3d deformation state, there is a need of information about a material point behind the observed surface. Due to this fact it is only possible to get...
In this paper the authors presents an analytical and experimental study for determine the Young’s modulus in case of a composite beam (aluminum and wood- spruce), loaded to pure bending. For the experimental study of displacements are used displacements transducers (WA20MM - HBM) and Digital Image Correlation (DIC) method. For spruce beam, displacements had determined for two cases: first, when the load is applied perpendicular on fibers, and the second, when the load is applied along the fibers.
The usage of full-field deformation data from experiments for the identification of material parameters is a topic of current research. The continuous improvement of optical measurement systems leads to promising results in parameter identification and optimization. With the high amount of data points the displacement and deformation field is not only a mean value but can be resolved locally which leads to a higher accuracy of the identified parameters. The goal of this research is to get reliable results from the full-field measurement data through a Finite Element Model Updating Method...
Operation of microelectronic components at higher temperatures and for long periods is one of the major reasons for technical failure of solder joints due to creep effect. This effect also has an influence on the determination of local mechanical material properties via nanoindentation tests. It generally occurs during the dwell time of the indentation procedure. In order to analyze its influence on the measured values of Young’s modulus several nanoindentation tests were performed at different elevated temperatures for a eutectic lead-free solder material, namely Sn24Bi58, which has its...
In the last ten years elastomers were more frequently used in complex technical fields which require high performance. Therefore it is very important to have an instrument to estimate the service life of these technical parts. At the moment there are two classical methods for service life prediction. Both are more or less adapted from metal parts engineering. Fracture mechanics uses the characteristic values of dynamic crack propagation experiments to calculate the load cycles to failure for different load amplitudes. The other method, based on the concept of Wöhler, measures the lifetime of...
The challenge was to calculate the tooth root strength of worm wheels. This is important for a better prediction of cracks. To use local stresses is a suitable way in comparison with rated stresses, especially in the case of complex shaped components.
The paper presents the evaluation of the pedestrian safety, during a collision with a road vehicle with the high bonnet leading edge. A Sport Utility Vehicle (SUV) was chosen to investigate the influence of vehicle front design on the pedestrian lower extremity injuries. The Finite Element Method (FEM) was utilized in order to reduce the costs and time needed to carry out a pedestrian-to-car front aggressiveness test. The virtual tests carried out by means of the numerical, certified Finite Element (FE) lower leg impactor were further contrasted with the results of the multibody (MB)...
Excavation process in open cast mines requires heavy machines which work in very hard conditions. The machines are strongly exposed to dynamic loads during operation. The problem of identification of modal modes is additionally complicated while the operational conditions changes. Type of excavated material, configuration of the machine, balancing and many other factors can shift frequencies or even influence on mode shape.
Turbogenerator rotors are a typical example of large components experiencing low cycle fatigue (LCF). Every machine switch-on and switch off corresponds to a LCF cycle, for a total amount of 10,000-15,000 cycles in the whole machine life. In, an experimental study was presented, concerning the characterization of two materials for rotor and coil retaining ring (CRR) manufacturing. The design task of rotors and CRRs involves serious safety issues: incidents caused by unexpected failures may lead to rotor explosion with catastrophic effects. For this reason, the structural analysis must be...