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Austenite transformation simulation for a controlled rolling processing technology development

Abstract

Using an originally-developed computer model and appropriate software the impact of deformation on austenite phase transformation in low carbon alloyed steel was carried out. The computer simulation takes into account an impact of the deformation degree and takes into account non-constant cooling rate. That makes it useful for the development of thermal and deformation technological processes development. Based on the simulation results a technology of controlled rolling of low carbon steel alloyed by carbide forming elements (Nb, V, Ti) was developed. The proposed technique allows production of rolled steel sheets with high strength and plastic properties, as well as high impact strength in normal and low temperatures.

Open access
Continuous Preventive Bridge Maintenance of Swedish Municipalities – A Survey on Common Practice

Abstract

As part of a report [1] on continuous preventive bridge maintenance, a survey was conducted with Swedish municipalities. The survey’s focus was on bridges and preventive maintenance, as well as the demands and performance control stated by the municipalities. The preventive maintenance the survey focused on was the annual maintenance concerning washing, cleaning of drainage system and removal of vegetation. The survey showed both similarities and differences within the municipalities but also in comparison with Swedish Transport Agency (STA).

Open access
Dynamic Measurements for Determining Poisson’s Ratio of Young Concrete

Abstract

Knowledge of the elastic properties of concrete at early age is often a pre-requisite for numerical calculations. This paper discusses the use of a laboratory technique for determining Poisson’s ratio at early concrete age. A non-destructive test set-up using the impact resonance method has been tested and evaluated. With the method, it has been possible to obtain results already at 7 hours of concrete age. Poisson’s ratio is found to decrease sharply during the first 24 hours to reach a value of 0.08 and then increase to approximately 0.15 after seven days.

Open access
Filler and Water Reducer Effects on Sedimentation, Bleeding and Zeta-Potential of Cement Paste

Abstract

Bleeding and sedimentation quantify the stability of fresh cement paste, whereas the addition of fillers and water reducers affect the stability. The effect of various types of fillers and water reducers was investigated by measuring bleeding, hydrostatic pressure and electroacoustic zeta-potential. Depending on their characteristics and use, fillers can improve stability by reducing sedimentation rate and bleeding. The combined effects of fillers and water reducers on the sedimentation rates, quantified as time-dependent hydrostatic pressure changes (dp/dt) in fresh matrix, correspond to their effects on zeta-potentials. The influence of the water reducers on sedimentation and bleeding exceed that of filler type.

Open access
Frost Destruction of Concrete – A Study of the Validity of Different Mechanisms

Abstract

Well-known frost destruction mechanisms applicable to concrete not exposed to salt are, (1) hydraulic pressure during freezing, (2) growth of ice-bodies in capillaries during freezing. Theories behind these mechanisms are presented. A third mechanism, ice expansion during heating of frozen concrete, is put forward. The validity of a certain mechanisms is discussed by analyzing its ability to explain experimental observations.

Open access
Full-scale Test of an Unreinforced Concrete Dome Plug for the Spent Nuclear Fuel Repository

Abstract

In the planned Swedish repository for spent nuclear fuel, plugs are designed to close the deposition tunnels. The outer part of these plugs consists of a concrete dome made with self-compacting-concrete, designed to have low pH to reduce negative effects on the bentonite clay buffer. A full-scale test has been performed to evaluate the performance of the plug, to test the installation and to verify underlying design assumptions. In this paper, the behaviour of the concrete dome is evaluated based on measurements, from casting the concrete until it was subjected to 4 MPa hydrostatic water pressure.

Open access
The influence of chemical composition on the dimensions

Abstract

The paper presents the influences of nanofluids, which are used in hardening process, to dimension changes, hardness and microstructure of hardened construction of steel samples. An analysis was also carried out with the use of English methods of cooling abilities of nanofluids environments based on water, solid nanoparticles of Al2O3 and ammoniac water. The results of this experiment show, that only one of specific dimensions of cooled samples, in the distilled water, changed for about 9%, but when using nanofluids this change was smaller. The hardness of alloy materials got a few percent more when nanofluids were used in comparasion to using the distilled water. The gained results allow to conclude the positive influence of nanofluids on parameters of the hardened materials.

Open access
The Influence of Supplementary Cementitious Materials on Climate Impact of Concrete Structures Exposed to Chlorides

Abstract

Addition of fly ash or GGBS in concrete has shown to increase the durability and thus the service life of concrete structures exposed to chlorides. Currently, the durability relies on regulations, which beside a minimum cover thickness also put constraint on amount and type of SCM in different environments. Swedish regulations do not, however, consider the actual durability of different binders. As a consequence, a LCA might be misleading. This paper investigates the climate impact of concrete with SCM in chloride environment. Current prescriptive design approach is compared with a performance based service life approach and applied to bridge parts.

Open access
Long-term Influence of Concrete Surface and Crack Orientation on Self-healing and Ingress in Cracks – Field Observations

Abstract

This paper presents results from investigations on the long-term influence of concrete surface and crack orientation on ingress in cracks. Five reinforced concrete structures from Norway exposed to either de-icing salts or seawater have been investigated. Concrete cores were taken with and without cracks from surfaces with vertical and horizontal orientation. Carbonation in cracks was found on all de-iced structures, and a crack on a completely horizontal surface appeared to facilitate chloride ingress. Ingress of substances from seawater was found in all cracks from marine exposure. However, the impact of cracks on chloride ingress was unclear. Horizontal cracks on vertical surfaces appeared to facilitate self-healing.

Open access
Open loop control of piezoelectric tube transducer

Abstract

This paper is focused on the open loop control of a piezoelectric tube actuator, hindered by a strong hysteresis. The actuator was distinguished with 22 % hysteresis, which hinders the positioning of piezoelectric actuator. One of the possible ways to solve this problem is application of an accurate analytical inversed model of the hysteresis in the control loop. In this paper generalized Prandtl-Ishlinskii model was used for both modeling and open loop control of the piezoelectric actuator. Achieved modeling error does not exceed max. 2.34 % of the whole range of tube deflection. Finally, the inverse hysteresis model was applied to the control line of the tube. For the same input signal (damped sine 0.2 Hz) as for the model estimation the positioning error was max. 4.6 % of the tube deflection. Additionally, for a verification reason three different complex harmonic functions were applied. For the verification functions, still a good positioning was obtained with positioning error of max.4.56 %, 6.75 %and5.6%of the tube deflection.

Open access