Papers by Keyword: Strain

Abstract: The mechanical behaviour and adhesion properties of thermal oxide scales are key issues for steel processing and long-term durability. This chapter aims at taking up the various aspects to be considered for such studies. The first part is devoted to a description of the origin of stress and stress quantification. Then, description of mechanical failure and damaging patterns of thermal oxide scales will be given. Finally, definitions of adhesion energy as well as quantitative methods to measure adhesion energy will be proposed. An appendix describing the hypotheses and the constitutive equations for plane stress analysis, which suits to oxide scales, is also given The purpose is enriched by references in particular to Alain Galerie’s co-workers’ publications.

Abstract: This paper presents a new method and toolset to measure strain values of the fabrics under biaxial tensile test. The proposed model is based on the reverse engineering of Delta 3D printing system. A comparison is made to the existing widely accepted models of strain measurements. The designed toolset was developed by parameter based modelling and genetic optimization to ensure that the equipment can function within the given strain domains. The equipment design model can be adapted to any biaxial tension frame.

Abstract: This article discusses the algorithm for calculating the shell structure of arbitrary shape, taking into account the physical nonlinearity of the material used. In determining the parameters of the stress-strain state, a step loading procedure was used. Algorithm for calculating the shell structure of arbitrary shape, taking into account the physical nonlinearity of the used material is discussed in this article. In determining the parameters of the stress-strain state, a step loading procedure was used.

Abstract: The paper proposes a method for calculating the reinforced concrete elements strength according to the deformation model using the deformation diagrams of concrete and reinforcing steel materials, which eliminates the complicated procedure of numerical integration of stresses in the element section during the transition to generalized internal forces. Integral parameters of diagrams are introduced into the energy model for calculating the strength of reinforced concrete elements along with the deformations and stresses normalized values at the base diagrams’ points. The integral parameters are calculated for the element cross section, the strain at the stress diagram gravity center in the compressed concrete zone and the coordinates of force in the concrete and reinforcement are relative to the neutral axis from the condition of the stress profile shape compliance in the element compressed zone, and the concrete diagram is used in the calculations. The integral parameters calculated dependences for the compressive strength concrete classes. The recommendations on the concrete diagrams integral parameters values rationing and their use in the complex sections and statically indeterminable systems calculations are given.

Abstract: Comparative analysis of the use of the defining equations of plasticity theories obtained at the loading step in three ways is performed. In the first method, the relations between strains increments and stresses increments are obtained by differentiating the governing equations of the small elastic-plastic deformations theory between full stresses and strains. In the second method, the authors based on the proportionality hypothesis between the component deviators of strains increments and the component deviators of stresses increments without separating the incremental strain into elastic and plastic parts obtain the determining equations at the loading step. In the third method, the relations between the incremental strain and the stresses increment of the plastic flow theory are used on the basis of the hypothesis about the proportionality of the plastic deformations increments to the components of the stress deviator. Based on the analysis of algorithms for obtaining the constitutive relations and the analysis of the numerical results of the calculation example, preference is given to the second method of obtaining expressions between stress increments and strain increments without separating the latter into elastic and plastic parts.

Abstract: The paper describes a cause of the geometric accuracy degradation of slender metallic products during their operation, which consists in the relaxation of residual stresses accumulated while product manufacturing. The most promising technology among the existing technologies of residual stress relaxation is based on the use of vibromechanical vibrations. This technology has high performance and low energy consumption. The reason for the relaxation of residual stresses under the action of vibromechanical vibrations is the gradual accumulation of internal energy, which leads to plastic dislocation shifts upon reaching a critical level. The dislocation motion under the action of vibromechanical vibrations continues until the dislocations take a more compact layout that corresponds to the equilibrium energy state. For technological implementation of the process there was developed a method of ultrasonic stabilization of elastic plates, which serve as sensing elements in differential-pressure transducers. The experimental studies of ultrasonic stabilization are carried out. According to the results of the studies, there have been conducted tests of the microstructure of the control samples. It is established that the samples of steel 20CH13 subject to ultrasonic treatment have a more uniform structure than the samples after the factory technology of long "aging". This confirms the assumption about the structural-energy processes occurring during vibromechanical relaxation of residual stresses. The technology of ultrasonic stabilization can be recommended as a replacement to the "aging" technology on the basis of the obtained results.

Abstract: The process of less than 90 degrees angle bending is presented in this article. Elastic-plastic deformation took place in the sample. After removing the force, the effect of elastic spring-back occurs – the angle of the part is increased by a value that depends on many parameters. The usage of an elastic element in the stamp allows us to change the angle of spring-back. This is happened doe to adjusting the height of the press stroke. This allows us to produce parts with accurate dimensions.

Abstract: The results of computer simulation processing and determination of limiting degree of deformation by the Kolmogorov criterion are presented. The derivation of the dependence for the evaluation of the destruction of low-plastic materials at the edge is made at bend angle of 90⁰

Abstract: Zinc oxide Nanorods (ZnO-NRs) were deposited onto glass substrates using zinc chloride by Ultrasonic Spray Pyrolysis (USP) method. The films were prepared in different deposition time at optimum deposition parameters. The effect of deposition time on the structural, morphological and optical properties of ZnO-NRs was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectrometry (UV-Vis). XRD and SEM measurements indicated that all films show a hexagonal wurtzite Nano rods (NRs) structure growing preferentially along c-axis perpendicular to the surface of the substrate. Optical transmission spectra showed high transmittance of 80-85% in the visible range for all thin films, and increase of optical band gap from 3.24 to 3.265 eV with deposition time. The high quality c-axis orientated ZnO thin films with minimum strain and tuneable optical properties could be used as a transparent conducting oxide (TCO) for optoelectronic applications.

Abstract: In this article is determined the ratio between effective elastic characteristics of the fibrous transversally isotropic material. Fibrous uniaxial material, which consists of the isotropic elastic matrix and fiber, is in the focus of attention. It is assumed that mechanical properties of components under stretching and compression are different, notably matrix material and fiber material are multi-modular. Transverse stretching and transverse compression of composite cell are considered. Two problems for each type of strain are solved. In the first problem stresses and displacements of matrix and fiber under conditions of their common axisymmetrical deformation are determined. Subsequently similar characteristics for the cell deformation of the homogeneous transversally isotropic material as a composite are determined. Ratio between effective composite’s characteristics is solved from the conditions of equality of the axial displacements of the composite’s cell and radial displacements on its surface. The relation of the calculated ratio from volume fraction of fiber in a composite is analyzed.