Advanced ultrasonic for remaining life assessment of industrial components

Nonlinear ultrasonic is the new approach for the effective evaluation of material degradation in the area of nondestructive evaluation (NDE). Fatigue damage of a material produces a substantial distortion ofultrasonic waves propagating through the degraded material. The wave distortion is quantified by means of a material nonlinearity parameter f3 that is defused as the ratio ofthe amplitude of the 2nd harmonic to the square of the amplitude of the fundamental. This nonlinear parameter changes when, for instance, a distribution ofmicrocracks appears inside the material. This feature has recently been found as a new potential application in the characterization of fatigued and degraded materials. In this present paper, the potential of NLU technique to evaluate fatigue damage in structural steel and to assess the localized plastic deformation during high cycle fatigue to locate the position of crack initiation much before the failure along the gage length of hourglass type specimen in polycrystalline copper has been highlighted

Modern Ultrasonic Technique for Defect Detection in Cast Materials

In casting flaw detection is exclusively concerned with manufacturing defects. The typical cast defects are (i) shrinkage cavities which form during solidification as a result of the reduction in volume when metal changes from the liquid to the solid state. Shrinkage cavities occur in situations where molten metal is not available to compensate for the volume decrease during solidi-fication,(ii) porosity and gas holes; porosity is small smooth-faced cavities, generally smaller than 1.5 mm diameter, usually caused by the release of gas from the molten metal as it cools. Gas holes are also smooth-faced cavities but greater than 1.5 mm diameter. Typical causes of gas holes are evolution of gas from molten metal during solidifications, gas trapped as the molten metal enters the mould etc. (iii) hot tears; these are jagged crack type defects resulting from stresses imposed on the cast metal when it is just below the solidification temperature and so is in a weak condition. The stresses usually arise when the casting is restrained during contraction by the mould, or by an already solid thinner section. The defect occurs mainly at or near a change of section and may or may not extend to the surface, (iv) cracks; these are dis-continuities due to the fracture of the metal during or after solidification, (v) inclusions; these are foreign non-metallic materials such as sand or slag trapped within the cast metal, (vi) cold shuts; these are basica-lly 'lack of fusion' defect caused by the failure of a stream of molten metal to form a continuous bond with a second stream, or solid metal such as an internal chill or splash. They are most prevalent in thin-walled castings

Non-linear ultrasonic for structural damage assessment: Approach at CSIR-National Metallurgical Laboratory

CSIR-NML has been active for the last two decades on structural health monitoring and remaining life assessment of materials in the power plant, petrochemicals and steel industries through both microstructure and mechanical property evaluation as well as non-destructive evaluation (NDE). Over the years, CSIR-NML is pursuing focused application oriented research in NDE for diverse components like aerospace, defence, power and steel sectors. Need based development of NDE sensors and techniques for specialised applications are also the integral part of the activities. In recent years, realising the potential of Non-linear ultrasonic (NLU) for the assessment of progression of damage in structural materials, CSIR-NML has initiated activities in the area of NLU from 2006 onwards. Applications of NLU to assess the most prominent damages in industrial components like fatigue, corrosion and creep are one of the niche research areas of CSIR-NML. An attempt has also been initiated to develop damage predictive model based on NLU parameter. NML has also developed globally the first portable, site worthy NLU device (Ultra) that can be used to monitor the damage of in-service structural components

Centre for Non-destructive Evaluation at CSIR-National Metallurgical Laboratory, Jamshedpur for materials characterisation and damage evaluation: an Overview

Non-Destructive Evaluation (NDE) centre established in 2003, with a partial funding from Department of Science & Technology (DST), Govt. of India at CSIR- National Metallurgical Laboratory, Jamshedpur has developed different NDE based methodologies for characterisation of microstructure and assessment of different kinds of damage (creep, fatigue, corrosion etc) for diverse components from aerospace, defence, power and steel sector. Besides, need based development of NDE sensors and techniques for specialised applications are also the integral part of Centre activities. This paper will highlight some of the above activities particularly the research activities on fatigue and corrosion damage evaluation in structural materials by advanced NDE

Need of Improved Non-Destructive Technique for the Surface Condition Monitoring of High Speed Steel (HSS) Work Rolls

Over the last few years, the use of work rolls for hot rolling of flat steel has changed from clear chill rolls to indefinite chill, then came high chrome steel and now High Speed tool Steel (HSS). The hardness of HSS roll reaches 80/85 ShC, hence it becomes very much crack-sensitive and the developed crack is usually oriented parallel to the roll axis and propagates in a non-radial direction. In the next phase, a fatigue “cat’s tongue” like fracture band propagates progressively in a circumferential direction running more or less parallel to the barrel surface. The direction of propagation is opposite to that of the direction of roll rotation. Crack propagation develops within the working surface of the roll, gradually increasing in depth and width followed by a large surface spall of the overlying barrel surface. Hence it is highly recommended to eliminate all kinds of surface cracks, whenever these rolls are reground, otherwise these `cats – tongue’ band type spalls may lead to abnormal failure. This paper presents the necessity of development of improved non-destructive technique for the crack detection of HSS rolls and also highlights the recent attempts at Tata Steel in collaboration with CSIR-National Metallurgical Laboratory, Jamshedpur to develop surface wave based ultrasonic technique to detect fine cracks on the barrel surface of HSS rolls to optimise the grinding procedure for having crack free roll surface

Non-destructive Testing and Evaluation at CSIR-National Metallurgical Laboratory, Jamshedpur for Iron and Steel Industry: an Overview

In the area of iron and steel, the NDE centre at CSIR- National Metallurgical Laboratory has not only developed different NDE based methodologies for characterisation of microstructure and assessment of different kinds of damage (creep, fatigue, corrosion etc) in various grades of steel; but also developing methodologies for blast furnace lining thickness measurement and assessment of High Speed Steel (HSS) rolls. This paper will highlight some of the above activities particularly related to steel and allied industries