Scanning laser source and scanning laser detection techniques for different surface crack geometries

Standard test samples typically contain simulated defects such as slots machined normal to the surface. However, real defects will not always propagate in this manner; for example, rolling contact fatigue on rails propagates at around 25º to the surface, and corrosion cracking can grow in a branched manner. Therefore, there is a need to understand how ultrasonic surface waves interact with different crack geometries. We present measurements of machined slots inclined at an angle to the surface normal, or with simple branched geometries, using laser ultrasound. Recently, Rayleigh wave enhancements observed when using the scanning laser source technique, where a generation laser is scanned along a sample, have been highlighted for their potential in detecting surface cracks. We show that the enhancement measured with laser detector scanning can give a more significant enhancement when different crack geometries are considered. We discuss the behaviour of an incident Rayleigh wave in the region of an angled defect, and consider mode-conversions which lead to a very large enhancement when the detector is close to the opening of a shallow defect. This process could be used in characterising defects, as well as being an excellent fingerprint of their presence

Non-contact ultrasonic detection of angled surface defects

Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-breaking defects has assumed cracks inclined at 90° to the surface. This paper explores the interaction of Rayleigh waves with cracks which have a wide range of angles and depths relative to the surface, using a non-contact laser generation and detection system. Additional insight is acquired using a 3D model generated using finite element method software. A clear variation of the reflection and transmission coefficients with both crack angle and length is found, in both the out-of-plane and in-plane components. The 3D model is further used to understand the contributions of different wavemodes to B-Scans produced when scanning a sample, to enable understanding of the reflection and transmission behaviour, and help identify angled defects. Knowledge of these effects is essential to correctly gauge the severity of surface cracking

Scanning laser techniques for characterisation of different surface breaking defect geometries

Measurements using a laser scanning system consisting of a pulsed Nd:YAG laser to generate surface ultrasonic waves and an interferometer to detect the surface displacement, are presented for different samples and defect geometries. We show, firstly, details of the interaction of Rayleigh waves in thick samples with machined slots inclined at an angle to the surface normal, or with simple branched geometries, scanning the generation source over the defect (SLLS) or scanning the detection point over the defect (SLD). Secondly, we discuss effects of Lamb waves interacting with V-shaped defects in thin samples. The results from these measurements have shown that the signal enhancement found in the near-field in both cases can be used to position the defect and gain an idea of its geometry, and have shown this to be a suitable fingerprint of the presence of the defect

Interaction of laser generated ultrasonic waves with wedge-shaped samples

Wedge-shaped samples can be used as a model of acoustic interactions with samples ranging from ocean wedges, to angled defects such as rolling contact fatigue, to thickness measurements of samples with non-parallel faces. We present work on laser generated ultrasonic waves on metal samples; one can measure the dominant Rayleigh-wave mode, but longitudinal and shear waves are also generated. We present calculations, models, and measurements giving the dependence of the arrival times and amplitudes of these modes on the wedge apex angle and the separation of generation and detection points, and hence give a measure of the wedge characteristics

Farm poultry management : for 4-H poultry projects I and II

Accompanied by: Leader's guide : 4-H poultry project (to be used with Circular 75), March, 1945.Cover title.Includes "4-H Record" at end.I. Young stock production -- II. Flock management

Synthesis of Nanoporous Type A and X Zeolite Mixtures from Biomass Combustion Fly Ash for Post-Combustion Carbon Capture

In this study, improved nanoporous zeolites for use in post-combustion carbon capture have been synthesised from industrial-grade biomass combustion fly ash generated in one of the largest biomass combustion power plants in the UK. The method of nanoporous zeolite synthesis follows an alkaline fusion-assisted hydrothermal procedure. The nanoporous zeolites have been characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The presence of two crystalline structures, Faujasite and Linde Type A has been confirmed by the characterisation results. The CO 2 adsorption investigations were conducted via thermogravimetric analysis (TGA) to estimate the uptake capacity of the prepared adsorbents. TGA studies suggest that the improved nanoporous adsorbent, evaluated under 100 mol % CO 2 at atmospheric pressure, has an equilibrium capacity of over 1.6 mmolCO 2 /g at 50°C, a two-fold increase from our previous study with a crystalline structure confirmed by XRD.10.13039/501100000266-Engineering and Physical Sciences Research Council (EPSRC), UK; 10.13039/100008475-Brunel University London, UK

Challenging the orthodoxy: union learning representatives as organic intellectuals

Teacher education and continuing professional development have become a key areas of controversy in England since the period of school sector restructuring following the 1988 Education Reform Act. More recently teacher training and professional development have often been used to promote and reinforce a narrow focus on the government’s ‘standards agenda’. However, the emerging discourse of ‘new professionalism’ has raised the profile of professional development in schools, and together with union learning representatives, there are opportunities to secure real improvements in teachers’ access to continuing professional development. This paper argues however that union learning representatives must go beyond advocating for better access to professional development and should raise more fundamental questions about the nature of professional development and the education system it serves. Drawing on Gramsci’s notion of the ‘organic intellectual’, the paper argues that union learning representatives have a key role as organisers of ideas – creating spaces in which the ideological dominance of current policy orthodoxy might be challenged

Case-control study of the association between kava use and pneumonia in eastern Arnhem Land Aboriginal communities (Northern Territory, Australia)

Pneumonia causes significant morbidity and mortality in Aboriginal populations in Australia\u27s Northern Territory (NT). Kava, consumed in Arnhem Land since 1982, may be a risk factor for infectious disease including pneumonia. A case-control study (n=115 cases; n=415 controls) was conducted in 7001 Aboriginal people (4217 over 15 years). Odds ratios (OR) were calculated by conditional logistic regression with substance use and social factors as confounders. Pneumonia, vas not associated with kava use. Crude OR=1.26 (0.74-2.14, P=0.386), increased after controlling for confounders (OR=1.98, 0.63-6.23, P=0.237) but was not significant. Adjusted OR for pneumonia cases involving kava and alcohol users was 1.19 (0.39-3.62, P=0.756). In communities with longer kava-using histories, adjusted OR was 2.19 (0.67-7.14, P=0.187). There was no kava dose-response relationship. Crude ORs for associations between pneumonia and cannabis use (OR=2.27, 1.18-4.37, P=0.014) and alcohol use (OR=1.95, 1.07-3.53, P=0.026) were statistically significant and approached significance for petrol sniffing (OR=1.98, 0.99-3.95, P=0.056)

Revealing the mechanical and microstructural performance of multiphase steels during tensile, forming and flanging operations

The mechanical performance of Dual Phase (DP) and Complex Phase (CP) steels was investigated by SEM analysis, tensile testing, Forming Limit Curve investigation and flange formability testing. The alloys of interest were Dual Phase (DP) untempered, Dual Phase (DP) tempered and Complex Phase (CP) steels. Phase content analysis showed that the distribution of the ferrite and martensite phases was the same for the two DP alloys, but the grain size and condition (tempered/untempered) for the martensite islands was much different in the two alloys. In the tempered DP steel, the smaller grain size for the martensite and the tempering process resulted in increased elongation, more formability and ability to form a flange (flangeability). In CP steels the soft ferrite phase is replaced by harder bainite, yielding a bainitic-martensitic microstructure. Bainite reduced the total elongation of the alloy during tensile testing, reduced the formability (especially under plane strain conditions) of the alloy but improved the flangeability of the alloy. Under flanging conditions, CP steels deformed to higher strains, at tighter radii with minimum springback. Microstructural inspections at the outer radius of the flanged specimens revealed that in CP steels bainite deforms similarly to martensite, therefore the strain partitioning is smaller in CP steels in comparison to DP steels. Plastic deformation in CP steels upon flanging occurs with the formation of strong slip bands in both martensite and bainite. In contrast, the martensite and ferrite grains in DP steels deform quite differently leading to strong strain localisations. Void nucleation and cracking occurred at the martensite islands or within the soft ferrite phase next to the martensite islands. In CP steels no voids or damage was observed within the matrix. A special case study was done with a thicker and stronger alloy, a Martensitic 1400 steel to reveal the flangeability limits for advanced high strength steels. Neither cracks nor damage were observed visually on the flanged specimens. However SEM observations at the outer radius of the flanged samples revealed significant void growth at inclusion sites and cracks nucleating within the matrix adjacent to the inclusions.Publisher Statement: This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/)</p