Wyniki wyszukiwania - BazTech

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Thermal Deformation of Moulding and Core Sands with an Inorganic Binder Containing a Relaxation Additive

Bobrowski A., Drożyński D., Jakubski J., Szumera M., Kaczmarska K., Grabowska B.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 4

93--98

EN

The paper presents the results of an investigation of the thermal deformation of moulding sands with an inorganic (geopolymer) binder with a relaxation additive, whose main task is to reduce the final (residual) strength and improves knocking-out properties of moulding sand. The moulding sand without a relaxation additive was the reference point. The research was carried out using the hot-distortion method (DMA apparatus from Multiserw-Morek). The results were combined with linear deformation studies with determination of the linear expansion factor (Netzsch DIL 402C dilatometer). The study showed that the introduction of relaxation additive has a positive effect on the thermal stability of moulding sand by limiting the measured deformation value, in relation to the moulding sand without additive. In addition, a relaxation additive slightly changes the course of the dilatometric curve. Change in the linear dimension of the moulding sand sample with the relaxation additive differs by only 0.05%, in comparison to the moulding sand without additive.

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Modified Hot Distortion Test to Investigate the Effect of the Inorganic Binder on the High-Temperature Behaviour of Physically Hardened Moulding Sands

Stachowicz M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

45--50

EN

This study is an attempt to determine by Hot Distortion Test (HDT) the impact of physical methods of hardening inorganic binders in the moulding sands on phenomena caused by influence of thermal energy from heating elements with a temperature of 900°C +/- 10°C. Medium silica sand-based moulding mixtures were densified and then hardened using two physical methods: microwave heating at a frequency of 2.45 GHz or classical drying at a temperature of 110°C. Sodium silicate bonded sand (SSBS) with five unmodified kinds of hydrated sodium silicates subjected to two different types of hardening method were assessed in terms of their behaviour in high temperature. Thermal behaviour by means of deformation measurement was carried out with a modified Hot Distortion Test (mHDT). Due to this advanced, but unstable by appropriate standards Hot Distortion Test gives an opportunity to measure thermoplastic deformations (L) in moulding sands in many aspects, such as time of annealing. Research carried out in this way exposed differences between inorganic binders with molar module ranging from 3.4 to 2.0. It was established that deformations under the influence of high temperature last the longest in SSBS containing binders with molar module ranging from 3.4 to 2.9. Similarly, for these types of moulding sands the method of hardening the binder is found to be essential for increasing/decreasing the rate of thermoplastic deformations during the annealing of samples. The samples of SSBS made with binders with molar module from 2.5 to 2.0 are found to be excessively susceptible to thermoplastic deformation as a result of heating them in high environmental temperature presence.

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Odkształcenia termiczne stali budowlanej w zmiennym polu temperatur

Bednarek Z., Kamocka R.

Inżynieria i Budownictwo

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2003

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R. 59, nr 8

455-457

PL

Podano wyniki badań odkształceń stali klasy A-III gatunku 34GS. Omówiono wpływ prędkości ogrzewania na odkształcenia termiczne oraz na współczynnik liniowej rozszerzalności termicznej.

EN

Results of tests of thermal strain caused by thermal expansion and coefficient of linear thermal expansion are presented for steel class A-III grade 34GS, tested in a lineary variable temperature field at various heating rates.

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Wpływ ciepła hydratacji cementu na możliwość zarysowania konstrukcji żelbetowych o rozwiniętym przekroju poprzecznym

Flaga K.

Inżynieria i Budownictwo

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1998

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R. 54, nr 5

243-245

PL

Omówiono związek pomiędzy technologią betonowania a zagrożeniem termicznym konstrukcji. Zagadnienie zilustrowano przykładem zarysowań wsporników estakady żelbetowej, spowodowanych różnicami w odkształcalnościach termicznych płyty nośnej i wsprników. Podano sposób obliczenia i rozmieszczenia zbrojenia przypowierzchniowego w rozciąganych przez płytę nośną wspornikach.

EN

Relation between casting technology and thermic hazard of structure is described. The problem is illustrated with example of cracking of sidewalk cantilevers of exsisting reinforced concrete slab bridge span. The cracks are caused by difference of deformability of massive load-carrying slab and cantilevers. The way of calculation and arrangement of necessary near-surface reinforcement of cantilever against tension caused by massive slab is given.