Papers by Keyword: Transverse Crack

Abstract: Occurrence of defects like crack on the surface of the cast products has long been recognized as a critical challenge for steelmakers in the continuous casting. Cracks on the surface can severely reduce yield and required further operations like salvage and scarfing. Depending on the severity of defect slabs can be diverted or in worst cases a slab can be rejected altogether if the defect cannot be removed by surface conditioning. Rourkela Steel Plant (RSP) of Steel Authority of India Limited (SAIL) produces continuously cast slabs as feed material for plate mills and hot strip mill. Sometimes the slabs produced through continuous casting are faced issues intermittently due to presence surface defects like midface longitudinal cracks (LC) and transverse edge crack (EC) etc. A systematic investigation of the operating parameters of these casters e.g. monitoring of oscillation parameters, slabs and mould flux, simulation and analysis of fluid flow inside mould, steel chemistry and role of dissolve gases in steel. Based on the investigation critical parameters responsible for crack formation have been identified and key areas identified where modification need to be done. Modifications has been done in terms of mould flux addition practice, optimization of the grade chemistry, optimization of process route, optimization of casting speed, checking of strand thermal profile, mould & machine allignment etc. It was observed that the crack incidences are significantly lower after the modifications were done.

Abstract: The paper describes the rail failures occurring repeatedly in the same distance from the rail butt weldment. The results of this investigation, especially fractographic analysis of the fracture surface of rail, evaluation of its macrostructure and microstructure, EDS analysis and hardness measurements revealed that transverse crack initiated in the foot of rail gauge and propagated by fatigue mechanism until the final cleavage fracture.

Abstract: According to the national standard "Code for Design of Concrete Structure", the reliability index for the structural members of reinforced concrete have not been given, which are controlled by serviceability limit states. A methodological framework was proposed, which made use of fuzzy invalidation rule for reliability analysis of reinforced concrete members. Firstly, A membership function was chosen. Secondly, A equivalent function was established to deal with the fuzzy reliability of concrete structure by traditional JC method. Finally, the fuzzy reliability index of transverse crack of reinforced concrete structure was obtained.

Abstract: In this paper, the single disk rotor system with a transverse open and close crack has been taken as an example; square wave function has been adopted to express opening and closing characteristics of a transverse crack. The stability on the system has been discussed by theoretical analysis and experimental model study. The conclusions have shown that the unstable vibrations are found in the regions near the rotational speed at 2/3, 2/5and 2/7 of the critical speed in the large crack and the small damping case. The influence of some factors such as the crack depth and the damping on stability of the system is qualitatively discussed.

Abstract: In this paper, the single disk rotor system with a transverse open and close crack has been taken as an example; the stability problem on the system in the special speeds has been discussed by theoretical analysis and experimental study. First, the conditions, positions and areas of the stable vibrations and the unstable vibrations on a rotor system with a transverse crack have been studied quantitatively theoretically. Not only the conclusions of other authors are verified，but also that the unstable vibrations are found in the regions near the rotational speed at 2/5and 2/7 of the critical speed in the large crack and the small damping case. Then the influence of some factors such as the crack depth parameters and the damping on stability of the system is qualitatively discussed.

Abstract: An analytical model based on the displacement function of the opening of crack applied by Lundmark and Varna [26] in the internal layers to study the evolution of the decrease of stiffness in a laminate is investigated. The results of axial rigidity versus the crack density are presented for three composite materials. The influences of the temperature and moisture on the mechanical properties of composite material are highlighted. The micromechanical model of the laminates used in present study describes the degradation of the mechanical properties of composite material by the variation in the temperature and moisture. The hygrothermal effect is observed to be harmful for composite materials.

Abstract: In this study, we analyzed transverse cracks in rails using eddy current testing. Quantitative analysis was performed on transverse crack defect signals ascertained by actual flaw detection and finite element simulation of the rail that had developed a central transverse crack. The conductivity and width of the finite element model were equivalent to those of the actual rail. By analyzing the distribution of eddy current on the rail surface, the relationship between the variation in the density of eddy current and size of transverse crack was obtained. Experimental and simulation results indicated that the application of eddy current testing in quantitative analysis of a rail flaw was feasible and would be a valuable reference in future research.

Abstract: Structural health monitoring based on Lamb wave attracts great attention in large-span structures. Lamb wave propagation in complex structures is very complicated due to multiple reflection and mode conversion at geometrical and material features. For effectively inspecting structural integrity, numerical simulation is employed to for extract damage features. It is essential to develop fast and low-cost simulating methods to study Lamb wave propagation in damaged structures. Spectral element method (SEM) is one of the most attractive methods, which is employed to study wave propagation in damaged structures. A massless spring, coupling the longitudinal and rotational vibration, is proposed to model a transverse crack and analyze wave propagation in a composite cracked beam based on SEM. Cracked spectral element formulation is derived by modeling the crack as the spring, whose stiffness is obtained from laws of fracture mechanics. Due to asymmetry of the crack, extensional and flexural wave modes are reflected and transmitted from an incident flexural wave mode. The proposed model is verified by comparing with conventional finite element analysis. Power reflection and transmission varying with the crack depth is also calculated. The results indicate that power reflection/transmission ratio of a single mode is monotonic, which may provide some quantitative foundations for structural health monitoring.

Abstract: Overlay new cement concrete pavement on the old cement concrete pavement following different treatment schemes, survey pavement cracking phenomenon after the opening of the new pavement , analysis the crack resistance of the various programs, accumulate experience for the cement concrete pavement repair technical solutions.

Abstract: The problem of transverse crack formation in continuously cast steel has been an issue for over 30 years. The crack susceptibility depends not only to the steel composition, but also to the temperature history during casting. To improve the surface quality, two key solutions have been suggested; adjusting the straightening stage to an appropriate temperature range, out of hot ductility trough, and/or alloy modification. These solutions have certain limitations and difficulties still exist for grades such as peritectic steels containing Nb or V. In this article, the hot ductility of a peritectic steel grade with Nb has been studied under direct cast conditions. This was performed using a Gleeble 3800 thermo-mechanical simulator under two critical strain rates. In addition, the transverse crack formation and appearance, as well as the application of infrared camera to study the surface temperature profile of the slabs is presented.