This paper presents an experimental analysis of flexural capacity and deformability of structural concrete slabs prepared as composite members consisting of two concrete layers made of reinforced ordinary concrete (N) and fiber reinforced concrete (SFRC). The reinforced concrete composite slabs used in the tests were prepared in the dimensions of 600 x 1200 x 80 mm. The basis was composed of two layers consisting of SFRC, one as the top layer, and one as ordinary concrete. The results of the analysis confirm a significant improvement of structural properties of the composite slab in comparison to the slabs prepared wholly of ordinary concrete.
An automated method for crack identification and quantitative description of crack systems in concrete was developed in order to aid a service life assessment of concrete elements in structures. Flat polished specimens for crack analysis were impregnated with epoxy resin containing fluorescent dye. The examination of the crack system was performed in ultraviolet light using a stereomicroscope and an Image Pro Plus image analysis system on specimens cored out of several concrete structures. The laboratory tests were performed on cast specimens to establish correlations between water penetration and chloride diffusion and crack system parameters. The analysis of cracks in concrete cores taken from structures resulted in interesting conclusions based on the crack width distribution and crack localization with respect to steel reinforcement. The method was found very effective to support standard concrete diagnostics methods.
Inconel 713C precision castings are used as aircraft engine components exposed to high temperatures and the aggressive exhaust gas
environment. Industrial experience has shown that precision-cast components of such complexity contain casting defects like
microshrinkage, porosity, and cracks. This necessitates the development of repair technologies for castings of this type. This paper
presents the results of metallographic examinations of melted areas and clad welds on the Inconel 713C nickel-based superalloy, made by
TIG, plasma arc, and laser. The cladding process was carried out on model test plates in order to determine the technological and materialrelated
problems connected with the weldability of Inconel 713C. The studies included analyses of the macro- and microstructure of the
clad welds, the base materials, and the heat-affected zones. The results of the structural analyses of the clad welds indicate that Inconel
713C should be classified as a low-weldability material. In the clad welds made by laser, cracks were identified mainly in the heat-affected
zone and at the melted zone interface, crystals were formed on partially-melted grains. Cracks of this type were not identified in the clad
welds made using the plasma-arc method. It has been concluded that due to the possibility of manual cladding and the absence of welding
imperfections, the technology having the greatest potential for application is plasma-arc cladding.
The paper presents the results of research on the microstructure of GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoCuN25-6-3 cast steels with
a varying carbon content. The cause for undertaking the research were technological problems with hot cracking in bulk castings of duplex
cast steel with a carbon content of approx. 0.06% and with 23% Cr, 8.5% Ni, 3% Mo and 2.4% Cu. The research has shown
a significant effect of increased carbon content on the ferrite and austenite microstructure morphology, while exceeding the carbon content
of 0.06% results in a change of the shape of primary grains from equiaxial to columnar.
In this paper, the different mechanical behaviors of layered rocks with different bedding angles during uniaxial compression tests are studied. Numerical simulation models of layered rock are validated based on laboratory tests, and uniaxial compression tests are conducted by using Particle Flow Code (PFC). Using these simulations, the uniaxial compressive strength, failure patterns, development of micro-cracks, and displacement of meso particles are analyzed. When the bedding angle is similar to the failure angle, the macro failure planes develop directly along the beddings, the bedding behavior dictates the behavior of the layered rock, reducing the compressive strength.
New approach using direct crack width calculations of the minimum reinforcement in tensile RC elements is presented. Verification involves checking whether the provided reinforcement ensures that the crack width that may result from the thermal-shrinkage effects does not exceed the limit value. The Eurocode provisions were enriched with addendums derived from the German national annex. Three levels of accuracy of the analysis were defined - the higher the level applied, the more significant reduction in the amount of reinforcement required can be achieved. A methodology of determining the minimum reinforcement for crack width control on the example of a RC retaining wall is presented. In the analysis the influence of residual and restraint stresses caused by hydration heat release and shrinkage was considered.
A general model of the equations of generalized thermo-microstretch for an infinite space weakened by a finite linear opening mode-I crack is solved. Considered material is the homogeneous isotropic elastic half space. The crack is subjected to a prescribed temperature and stress distribution. The formulation is applied to generalized thermoelasticity theories, using mathematical analysis with the purview of the Lord-Şhulman (involving one relaxation time) and Green-Lindsay (includes two relaxation times) theories with respect to the classical dynamical coupled theory (CD). The harmonic wave method has been used to obtain the exact expression for normal displacement, normal stress force, coupled stresses, microstress and temperature distribution. Variations of the considered fields with the horizontal distance are explained graphically. A comparison is also made between the three theories and for different depths for the case of copper crystal.
The paper presents the susceptibility of AE44 magnesium alloy to electrochemical corrosion and stress corrosion cracking (SCC). The evaluation of the intensity of the interaction of the corrosive environment was carried out using the corrosion tests and the Slow Strain Rate Test (SSRT). Corrosion tests performed in 0.1 M Na2SO4 solution (immersion in solution and under cathodic polarization conditions) revealed that the layer of corrosion products was much thicker after immersion test. The results of SSRT showed that the AE44 alloy deformed in the solution was characterized by higher plasticity compared to the alloy deformed in the air after immersion in solution. Moreover, the fractures were characterized by different morphology. In the case of an alloy deformed in the solution under cathodic polarization many microcracks on the fracture were observed, which were not observed in the case of the alloy deformed in the air.