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Welded Joints Integrity of the Pressure Vessels Pipes Made of Hot Rolled Fine-Grained Steel
Get PDFThis paper contains results of tests performed in order
to determine mechanical properties of steel P460NL1, meant for
production of pressure vessels. Arc welding of samples from
which the specimens were taken was carried out through the
application of welding process 111, because it is one of the
processes for the execution of pipelines for the transport of oil or
gas. Micro specimens with diameter of 1,5 mm were tested in
order to determine tensile properties of material taken from the
heat-affected zone and weld metal, while specimens with
diameter of 6 mm were tested in order to determine tensile
properties of parent material. Standard Charpy V-notch
specimens were used in order to determine impact energy.
Results of metallographic tests which refer to the structure of a
pipe welded joint are also presented.
On the basis of results of tensile tests carried out on specimens
taken from parent material, heat-affected zone and weld metal it
was determined that mean values of yield strength and tensile
strength of parent material and weld metal are practically equal,
while these values for heat-affected zone are more than 20%
lower. The situation is similar regarding the value of elongation.
Mean values of overall impact energy for parent material and
weld metal are practically equal, while in comparison with
results obtained for material taken from the heat-affected zone
they are more than 2 times lower. Through the analysis of energy
necessary for initiation and propagation of cracks it was
determined that the ratio of those energies is very good when it
comes to parent material and weld metal, while it was also
determined that the critical location for crack initiation is the
heat-affected zone.
Integrity evaluation of the air tank during exploitation was
carried out through the analytical calculation of strength of the
shell and upper bottom based on their technical properties after
the completion of reparatory welding/surface welding
Cavitation Properties of Rendering Mortars with Micro Silica Addition
Get PDFMicro-silica is a highly efficient mineral additive whose role is reflected in improvements of microstructure packing, strength and durability of non-shaped composite building materials such as concrete and mortar. A comparative study of performances of rendering mortars with different quantities of micro silica was conducted. The experimental program included production of reference mortar based on Portland cement and quartz sand (CM) and three mortars with 5, 10, and 15 % addition of micro silica (SCM-5, SCM-10, and SCM-15). The effect that micro silica addition has on the thermal behavior and mechanical properties of mortars was discussed. Hydration mechanisms and thermally induced reactions were studied at temperatures ranging from ambient to 1100 degrees C by differential thermal analysis. The results were supported by X-ray diffraction analysis. The cementing efficiency of micro silica was assessed by cavitation erosion test. The changes in the morphology of mortar samples prior and upon cavitation testing were monitored by means of the scanning electron microscope imagining. It was found that 5 % of superfine micro silica (SCM-5 mortar) has positive effects on mechanical strengths (15 % increase in compressive strength) due to microstructure densification arising from the successive filling of voids by the micro silica. Addition of micro silica also improved the cavitation erosion resistance in comparison with reference cement mortar (SCM-5 showed cavitation velocity as low as 0.09 mg/min). This qualifies mortars with micro silica addition as building materials which can be safely employed in potential hydro-demolition environment
Case study on application of ground-penetrating radar for non-destructive assessment of historical building
No full textNon-destructive techniques such as ground-penetrating radar (GPR) have many benefits for
the condition assessment of structures. Acquiring real-time results in a short time frame makes
the inspection with GPR very effective even in the case of large areas. The inspection ensures
minimal obstruction, therefore, GPR could be beneficial in cases of cultural heritage and historical
buildings. By emitting electromagnetic waves into a structure, GPR detects waves reflected from
the internal objects. The appropriate analysis and interpretation of results offer information
about the position of reinforcement and the presence of possible structural irregularities. The
identification of internal degradation due to the presence of voids, cracks, or water intrusion can
also reliably be detected by GPR.
In this paper, the main principles of the GPR technique are presented. This is followed by the
application of GPR for the localization of reinforcement and determination of slab geometry in the
case of Faculty of Teacher Education in Petrinja
Razvoj nove generacije dopunskih cementnih materijala - termički i mehanički aktivirane gline
No full textVerifikacija tehničkog rešenja od strane Matičnog naučnog odbora za saobraćaj, urbanizam i građevinarstvo sprovedena je na sednici održanoj 29.12.2020. godin
Clay sample preparation by microwave digestion for Fe determination using inductively coupled plasma optical emission spectrometry
No full textSome Aspects of Pile Testing Using Static Load Test (SLT)
Get PDFThe paper presents typical examples of pile load tests with a specific analysis of results, whereby the test methodology relies on existing ASTM standards, own knowledge and experience. The pile tests were conducted using own equipment with licensed hardware and software for the Static Load Test (SLT). The tests have shown some situations that arise when analyzing the bearing capacity of piles. Aspects of application of different equipment and testing methodologies in different situations are indicated. Also, the need to develop a plan for testing the load capacity of piles when it comes to large and significant structures was pointed out
Mechanisms and morphologies of cavitation damage of NN 70 steel
Get PDFBroken test tubes for low-cycle fatigue testing of Nionicral 70 (NN-70) parent material (PM) steel
and simulated heat-affected zones (SHAZ) were used to produce samples for cavitation resistance
testing. Ultrasonic vibrational cavitation method (stationary sample method) was applied for
testing in laboratory conditions. The test conditions and procedure, sample preparation and
interpretation of results are defined by ASTM G32. The surfaces of the NN-70 PM and SHAZ steel
samples were exposed to cavitation and damage monitoring over time. Measuring the weight loss of
samples on the analytical balance after a certain time allowed us to determine the cavitation
velocity as a measure of the material's resistance to the effect of cavitation. Scanning electron
microscopy (SEM) was applied to monitor variations in surface morphology with changing test
time. On the basis of the results of the cavitation resistance test, the morphologies of the surface
damage for different exposure times of the cavitation of PM and SHAZ steel NN-70 samples were
analyzed, as well as the mechanisms that led to the damage of the sample surfaces
Influence of different types of fibers on the ultimate and residual flexural strength of sprayed concrete
Get PDFThe influence of the application of different types of fibres on the flexural strength of beams cut from slabs of
sprayed concrete is presented in the paper. Fibres of different materials, shapes and dimensions were used. All types of
concrete were made of the same component materials and composition, except the amount of fibres that is varied. Slabs
of dimensions 60x60x10 cm were made using a concrete spraying machine. After curing, the beams of 75x125x500 mm
were cut from the beams. Flexural strength of the beams was tested according to SRPS EN 14488-3 at the age of 28
days. Based on the test results, depending on the type, shape, amount and distribution of fibres, values of ultimate and
residual strengths were analysed. The highest values of ultimate and residual strength at deformations of 0.5-1, 0.5-2 and
0.5-4 mm had sprayed concrete (or shotcrete) with the addition of 40 mm polypropylene fibres
Experimental research of mechanical characteristics of railway vehicles safety coupling components
No full textThe coupling system provides a mechanical connection between European railway vehicles. Screw couplings are designed as a safety device in railway vehicles with coupling links and screw as two main components intended to break. Failure of these components is necessary when the load between vehicles is exceeded, otherwise more significant draw gear elements will fracture. The analysis of train break cases shows that the failure of the links occurs only in an approx. 6% of cases. Therefore, the links taken from exploitation after more than 30 years in operation were tested to determine their mechanical characteristics. Tensile testing was performed according to the ISO 6892-1 standard with a continual force and a minimal and maximal test speed prescribed by ISO 6892-1. The values of mechanical characteristics of coupling links are substantially improved during production after heat treatment by hardening and tempering. However, test results of mechanical characteristics didn’t meet all prescribed limits for the minimum requirements according to UIC 826. The current regulations of mechanical characteristics were not in force in time of link production. Examination of the tested links showed a ductile fracture and the cross-sectional area shows the planar stress state
