Noncontact Temperature Measurements of Hot Steel Bodies Using an Electromagnetic Acoustic Transducer (EMAT)

A noncontacting sensor system for measuring the average internal temperature of hot steel objects has been developed. The system uses a pulsed ruby laser for the generation of the acoustic wave and a pulsed Electromagnetic Acoustic Transducer (EMAT) as the receiver in a through-transmission technique. The pulsed EMAT design has been successfully tested to 1300° Celsius on a nine-inch-long stainless steel sample. The system measures the time-of-flight of the acoustic wave, which is coupled with the part dimension to determine the average acoustic velocity. From a calibrated relationship between velocity and temperature, the average sample temperature is determined.</p

The Elastic Compliance of Imperfect Interfaces: Review and Relationship to Ultrasonic Scattering

When a tensile load is applied to an elastic solid with an imperfect interface containing cracks or voids, the farfield displacement that would occur in the absence of the interface will be increased by localized deformations [1]. This extra extension can be modeled as the response of two half-spaces connected by a distributed spring. The spring stiffness per unit area, K, is a function of the topography of the partially contacting surfaces

Experiences in the Use of Guided Ultrasonic Waves to Scan Structures

The use of guided ultrasonic waves to rapidly interrogate large structures is a topic that is currently receiving considerable attention. The purpose of this paper, and the companion paper by Alers [1], is to briefly review some past experience that may not be readily available to current researchers since many of the results were not presented in archival publications. The work described in this paper was conducted in the context of exploring applications of electromagnetic-acoustic transducers (EMATs) [2,3] as a part of the NDE effort at the Rockwell International Science Center in the period 1970–1980. In addition to the author, others playing key roles in various parts of this effort included G. A. Alers, R. K. Elsley, C. M. Fortunko, M.W. Mahoney and C. F. Vasile. The companion paper by Alers includes subsequent developments at the private company, Magnasonics, Inc. as well as more recent work at the National Institute of Standards and Technology. Although EMAT’s were used in all of this work as the sensors to excite and detect the guided ultrasonic modes, the basic ideas apply to the use of guided modes excited by any kind of sensor to scan structures

Acoustic Nonlinearities in Adhesive Joints

Ultrasonic techniques have been used successfully to measure important bond parameters and to detect various defects in adhesive joints for about twenty years. Recent reviews of nondestructive testing of adhesively bonded structures can be found in the literature [1–3]. For direct strength assessment, the reliability of these techniques leaves much to be desired. Linear acoustic parameters are only indirectly correlated to material and bond strength, therefore we must rely on dubious empirical relations between the measured parameter (e.g., velocity or attenuation) and the sought strength parameter on a case-to-case basis. On the other hand, it is well known that failure of most materials and bonds is usually preceded by some kind of nonlinear mechanical behavior, well before appreciable plastic deformation occurs, i.e. within the range of nondestructive testing. This macroscopic nonlinearity is due to a number of different causes such as weakening of covalent bonds with increased atomic spacing, reduction in the number of these bonds, etc. It seems to be reasonable to assume that nonlinear parameters measured at approximately 10–20% of the ultimate stress level are more directly correlated to mechanical strength than linear ones measured at negligibly low ultrasonic amplitudes:</p

In-Plant Demonstration of High-Temperature Emat System on Continuous Caster Strand

The Pacific Northwest Laboratory (PNL) has been working with the Office of Industrial Programs of DOE and the American Iron and Steel Institute (AISI) since 1983 to develop a sensor that can determine the internal temperature of hot steel bodies. Research projects utilizing the relationship between acoustic velocity and temperature have been the primary technique investigated. The techniques most recently used have been laser-generated stress waves and EMAT systems [1,2,3]. Development of an ultrasonic sensor that can measure the acoustic velocity at high temperatures has been the major effort over the past few years. The internal temperature of steel bodies can be determined by measuring the time-of-flight through a known distance to calculate the velocity, and from the relationship between temperature and velocity, the average internal temperature can be determined [4,5]

Emats for Roll-By Crack Inspection of Railroad Wheels

Railroad safety depends on many factors. The integrity of the wheels on rolling stock is one that is subject to nondestructive evaluation. For some years, ultrasonic testing has been applied to the detection of cracks in wheel treads, with particular attention to automatic, in-rail, roll-by methods. We have begun constructing a system aimed at using relatively low frequency Rayleigh waves generated by electromagnetic-acoustic transducers (EMATs). The current design uses a permanent magnet to maintain a compact structure and minimize the size of the pocket machined into the rail. Measurements thus far indicate a responsiveness, even to small flaws. With the development of a signal processing and analysis system, field tests should soon be possible.</p

Ultrasonic Evaluation of Interfacial Properties in Adhesive Joints: Evaluation of Environmental Degradation

It is known that failure of adhesive joints can occur either in the bulk region of an adhesive layer (cohesive mode) or along an interface between the adhesive and an adherent (interfacial or adhesion mode). Properly manufactured adhesive joints fail in the cohesive mode, while after environmental degradation the failure mode becomes predominantly interfacial. Therefore we conclude that humid environments affect mostly the interfacial region of a joint. This indicates the importance of non-destructive assessment of interface properties. While methods of cohesive property evaluation have progressed significantly, much more effort is required to develop interface evaluation methods. A development of this type is undertaken in this work

Defining Feasibility and Pilot Studies in Preparation for Randomised Controlled Trials: Development of a Conceptual Framework

We describe a framework for defining pilot and feasibility studies focusing on studies conducted in preparation for a randomised controlled trial. To develop the framework, we undertook a Delphi survey; ran an open meeting at a trial methodology conference; conducted a review of definitions outside the health research context; consulted experts at an international consensus meeting; and reviewed 27 empirical pilot or feasibility studies. We initially adopted mutually exclusive definitions of pilot and feasibility studies. However, some Delphi survey respondents and the majority of open meeting attendees disagreed with the idea of mutually exclusive definitions. Their viewpoint was supported by definitions outside the health research context, the use of the terms ‘pilot’ and ‘feasibility’ in the literature, and participants at the international consensus meeting. In our framework, pilot studies are a subset of feasibility studies, rather than the two being mutually exclusive. A feasibility study asks whether something can be done, should we proceed with it, and if so, how. A pilot study asks the same questions but also has a specific design feature: in a pilot study a future study, or part of a future study, is conducted on a smaller scale. We suggest that to facilitate their identification, these studies should be clearly identified using the terms ‘feasibility’ or ‘pilot’ as appropriate. This should include feasibility studies that are largely qualitative; we found these difficult to identify in electronic searches because researchers rarely used the term ‘feasibility’ in the title or abstract of such studies. Investigators should also report appropriate objectives and methods related to feasibility; and give clear confirmation that their study is in preparation for a future randomised controlled trial designed to assess the effect of an intervention

CONSORT 2010 statement: extension to randomised pilot and feasibility trials [on behalf of the PAFS consensus group*]

The Consolidated Standards of Reporting Trials (CONSORT) statement is a guideline designed to improve the transparency and quality of the reporting of randomised controlled trials (RCTs). In this article we present an extension to that statement for randomised pilot and feasibility trials conducted in advance of a future definitive RCT. The checklist applies to any randomised study in which a future definitive RCT, or part of it, is conducted on a smaller scale, regardless of its design (eg, cluster, factorial, crossover) or the terms used by authors to describe the study (eg, pilot, feasibility, trial, study). The extension does not directly apply to internal pilot studies built into the design of a main trial, non-randomised pilot and feasibility studies, or phase II studies, but these studies all have some similarities to randomised pilot and feasibility studies and so many of the principles might also apply. The development of the extension was motivated by the growing number of studies described as feasibility or pilot studies and by research that has identified weaknesses in their reporting and conduct. We followed recommended good practice to develop the extension, including carrying out a Delphi survey, holding a consensus meeting and research team meetings, and piloting the checklist. The aims and objectives of pilot and feasibility randomised studies differ from those of other randomised trials. Consequently, although much of the information to be reported in these trials is similar to those in randomised controlled trials (RCTs) assessing effectiveness and efficacy, there are some key differences in the type of information and in the appropriate interpretation of standard CONSORT reporting items. We have retained some of the original CONSORT statement items, but most have been adapted, some removed, and new items added. The new items cover how participants were identified and consent obtained; if applicable, the prespecified criteria used to judge whether or how to proceed with a future definitive RCT; if relevant, other important unintended consequences; implications for progression from pilot to future definitive RCT, including any proposed amendments; and ethical approval or approval by a research review committee confirmed with a reference number. This article includes the 26 item checklist, a separate checklist for the abstract, a template for a CONSORT flowchart for these studies, and an explanation of the changes made and supporting examples. We believe that routine use of this proposed extension to the CONSORT statement will result in improvements in the reporting of pilot trials. Editor’s note: In order to encourage its wide dissemination this article is freely accessible on the BMJ and Pilot and Feasibility Studies journal websites