Identification of key GMAW fillet weld parameters and interactions using artificial neural networks

Fillet welds are one of the most commonly used weld joints but one of the most difficult to weld consistently. This paper presents a technique using Artificial Neural Networks (ANN) to identify the key Gas Metal Arc Welding (GMAW) fillet weld parameters and interactions that impact on the resultant geometry, when using a metal cored wire. The input parameters to the model were current, voltage, travel speed; gun angle and travel angle and the outputs of the model were penetration and leg length. The model was in good agreement with experimental data collected and the subsequent sensitivity analysis showed that current was the most influential parameter in determining penetration and that travel speed, followed closely by current and voltage were most influential in determining the leg length. The paper also concludes that a ‘pushing’ travel angle is preferred when trying to control the resultant geometry mainly because both the resultant leg length and penetration appear to be less sensitive to changes in heat input

The Ingestion of 39 or 64 g·h-1 of Carbohydrate is Equally Effective at Improving Endurance Exercise Performance in Cyclists

In an investigator-blind, randomized cross-over design, male cyclists (mean± SD) age 34.0 (± 10.2) years, body mass 74.6 (±7.9) kg, stature 178.3 (±8.0) cm, peak power output (PPO) 393 (±36) W, and VO2max 62 (±9) ml·kg-1·min(-1) training for more than 6 hr/wk for more than 3y (n = 20) completed four experimental trials. Each trial consisted of a 2-hr constant load ride at 95% of lactate threshold (185 ± 25 W) then a work-matched time trial task (~30 min at 70% of PPO). Three commercially available carbohydrate (CHO) beverages, plus a control (water), were administered during the 2-hr ride providing 0, 20, 39, or 64 g·hr-1 of CHO at a fluid intake rate of 1L·hr(-1). Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39 g·hr(-1) (34:19.5 ± 03:07.1, p = .006) and 64 g·hr(-1) (34:11.3 ± 03:08.5 p = .004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was -6.1% (95% CI: -11.3 to -1.0) and -6.5% (95% CI: -11.7 to -1.4) in the 39 and 64 g·hr(-1) trials respectively. The 20 g·hr(-1) (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared with control (p = .126) despite a mean improvement of -3.7% (95% CI -8.8-1.5%). No further differences between CHO trials were reported. No interaction between CHO dose and pacing strategy occurred. 39 and 64 g·hr-1 of CHO were similarly effective at improving endurance cycling performance compared with a 0 g·hr(-1) control in our trained cyclists

Corrosive wear behaviour of various stainless steel alloys and a Stellite 6 weld cladding

This study has comprised an investigation the corrosive wear behaviour of UNS S31600, a low hardness (280Hv) UNS S42000, a high hardness (480Hv) UNS S42000 and a single layer Stellite 6 (UNS R30006) weld cladding on a low alloy carbon steel (UNS G43400). Erosion-corrosion testing was conducted using a submerged jet of 3.5% NaCl aqueous solution with spherical silica sand particles. The sand concentration was 2.4g/l, the velocity of the jet was 18m/s and the testing temperature range was 16°C-27°C. Both normal incidence (90°) and low angle (20°) tests were performed. Mass losses, wear scar depths and a volumetric analysis technique were used to assess the damage in the direct impinged zone (DIZ) and the outer area (OA) of the specimens. For all materials, it was found that mass loss was higher at 20° tests than that of 90°. However, when comparing wear scar depths the opposite trend was found. The results are discussed in terms of comparative material behaviour, the influence of material hardness and the corrosive wear mechanisms in different regions formed during slurry jet impingement

Metabolic Responses to Carbohydrate Ingestion during Exercise: Associations between Carbohydrate Dose and Endurance Performance

Carbohydrate (CHO) ingestion during exercise lasting less than three hours improves endurance exercise performance but there is still debate about the optimal dose. We utilised stable isotopes and blood metabolite profiles to further examine metabolic responses to CHO (glucose only) ingestion in the 20–64 g·h−1 range, and to determine the association with performance outcome. In a double-blind, randomized cross-over design, male cyclists (n = 20, mean ± SD, age 34 ± 10 years, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, VO2max 62 ± 9 mL·kg−1·min−1) completed four main experimental trials. Each trial involved a two-hour constant load ride (185 ± 25 W) followed by a time trial, where one of three CHO beverages, or a control (water), were administered every 15 min, providing 0, 20, 39 or 64 g CHO·h−1. Dual glucose tracer techniques, indirect calorimetry and blood analyses were used to determine glucose kinetics, exogenous CHO oxidation (EXO), endogenous CHO and fat oxidation; and metabolite responses. Regression analysis revealed that total exogenous CHO oxidised in the second hour of exercise, and suppression of serum NEFA concentration provided the best prediction model of performance outcome. However, the model could only explain ~19% of the variance in performance outcome. The present data demonstrate that consuming ~40 g·h−1 of CHO appears to be the minimum ingestion rate required to induce metabolic effects that are sufficient to impact upon performance outcome. These data highlight a lack of performance benefit and few changes in metabolic outcomes beyond an ingestion rate of 39 g·h−1. Further work is required to explore dose-response effects of CHO feeding and associations between multiple metabolic parameters and subsequent performance outcome

Visualisation of alternating shielding gas flow in GTAW

The alternating shielding gas technique is a method of achieving transient arc characteristics during arc welding; however the complex flow that occurs through its use has not been investigated previously. A schlieren system was used to image density gradients that arise when alternating argon and helium shield gases, under varying flow parameters, with gas tungsten arc welding (GTAW). A theoretical analysis was carried out to determine the conditions under which the technique facilitates arc pulsing, in particular to avoid mixing the shield gases in the delivery pipe prior to the welding nozzle. At appropriate pulsing frequency and flow rates, a stable horizontal region of helium was obseved in the weld region, maintained in position by the denser argon from the preceding pulse. This higher than average mass fraction of helium when applying the shielding gases alternately, compare to a premixed gas with the same volume of argon and helium, increased the weld penetration by 13% on average, suggesting a modest improvement in heat transfer

Nitrogen footprints: Past, present and future

The human alteration of the nitrogen cycle has evolved from minimal in the mid-19th century to extensive in the present time. The consequences to human and environmental health are significant. While much attention has been given to the extent and impacts of the alteration, little attention has been given to those entities (i.e., consumers, institutions) that use the resources that result in extensive reactive nitrogen (Nr) creation. One strategy for assessment is the use of nitrogen footprint tools. A nitrogen footprint is generally defined as the total amount of Nr released to the environment as a result of an entity's consumption patterns. This paper reviews a number of nitrogen footprint tools (N-Calculator, N-Institution, N-Label, N-Neutrality, N-Indicator) that are designed to provide that attention. It reviews N-footprint tools for consumers as a function of the country that they live in (N-Calculator, N-Indicator) and the products they buy (N-Label), for the institutions that people work in and are educated in (N-Institution), and for events and decision-making regarding offsets (N-Neutrality). N footprint tools provide a framework for people to make decisions about their resource use and show them how offsets can be coupled with behavior change to decrease consumer/institution contributions to N-related problems

Afgewezen en uit Nederland vertrokken? Een onderzoek naar de achtergronden van variatie in zelfstandige terugkeer onder uitgeprocedeerde asielzoekers

__Abstract__ In de periode 2008 tot en met maart 2010 heeft het Wetenschappelijk Onderzoek- en Documentatiecentrum (WODC) voor het eerst uitgebreid onderzoek gedaan naar de vraag hoe verklaard kan worden dat sommige uitgeprocedeerde asielmigranten met hulp van de Nederlandse overheid besluiten om zelfstandig terug te keren, ter-wijl anderen er de voorkeur aan geven om illegaal in Nederland te blijven of even-tueel door te migreren naar een ander land.1 De Directie Migratiebeleid (DMB) heeft het WODC verzocht een vervolgstudie te verrichten naar zelfstandige terugkeer. Dit rapport vormt de neerslag van deze vervolgstudie. Er is in de volgende opzichten voortgebouwd op het eerdere terugkeeronderzoek. Ten eerste is er in dit onderzoek gekeken naar feitelijk terugkeergedrag (geregis-treerde terugkeer via IOM) in plaats van naar terugkeerintenties en -attitudes, die in de eerdere studie centraal stonden. Ten tweede wordt terugkeer nu in verband gebracht met onafhankelijke gegevens over maatschappelijke omstandigheden in herkomstlanden. Ten derde wordt ditmaal uitgebreider gekeken naar de mogelijke invloed van terugkeerprogramma’s op zelfstandige terugkeer. Ten vierde is er nu ook onderzoek gedaan naar de vraag of de kans op terugkeer afhangt van demo-grafische kenmerken van afgewezen asielzoekers (zoals geslacht, leeftijd en gezins-samenstelling) en de tijd die de IND nodig heeft om een asielaanvraag te beoorde-len (procedureduur in eerste aanleg). De centrale vraag van het onderzoek luidt: In hoeverre stimuleren beleidsinstrumenten op het gebied van terugkeer de zelf-standige terugkeer via IOM wanneer wordt gecontroleerd voor relevante individuele kenmerken en sociaaleconomische en politieke omstandigheden in het land van herkomst

A study on the erosion-corrosion behaviour of engineering materials used in the geothermal industry

Erosion-corrosion can be a significant issue for engineering components used in the geothermal industry. This study assesses the erosion-corrosion behaviour of a wide range of engineering alloys which are used in various parts of geothermal power plants. The evaluated materials comprised a carbon steel, low-alloy steel, three grades of stainless steel together with Ni–Cr alloy (Inconel 625) and Ti–6Al–4V. Tests were conducted by utilising a submerged 90° impinging slurry jet consisting of silica sand particles suspended in an acidic (pH 4) aqueous solution consisting of 3.5% NaCl. Gravimetric mass losses, in-situ potentiodynamic polarisation scans and an enhanced volumetric analysis technique were used to assess the influence of hydrodynamic conditions on the erosion-corrosion behaviour of the test materials. The effect of applied cathodic protection was also examined. Post-test metallurgical examination was also conducted via SEM. The results showed the distinct differences between low alloy steels and "corrosion resistant" alloys – with the former demonstrating substantial material loss in the low-angle corrosive wear region due to large amounts of corrosion-related damage. Both superaustenitic stainless steel (UNS S31254) and Inconel 625 (UNS N06625) exhibited the greatest erosion-corrosion resistance of the test materials – with Inconel 625 demonstrating the greatest resistance to high angle corrosive wear. The relevance of the findings to materials selection and other methods of protection against surface degradation in geothermal power plants is discussed

Influence of metallic matrix on erosion-corrosion behaviour of high chromium cast irons under slurry impingement conditions

Chromium cast irons (CCI) comprise versatile materials that encompass a range of compositions and microstructures often chosen to promote good wear resistance. There are, however, issues that arise when the cast iron is required to operate in conditions where corrosion, as well as, wear is a factor. This scenario usually results in adapting the composition of the CCI in order to achieve higher chromium content in the metallic matrix and, thereby, to attain the corrosion resistance exhibited by high-Cr stainless steels. This paper comprises a comparison of the corrosive wear behaviour of an austenitic-based hypoeutectic cast iron and a martensitic-based, near-eutectic cast iron with the associated stainless steels, in a saline water under solid-liquid submerged jet conditions. A comprehensive experimental methodology has been adopted including evaluation of the behaviour of the materials in free erosion-corrosion conditions and with the application of cathodic protection. This approach has extended the understanding of the fundamental deterioration mechanisms in different hydrodynamic conditions and has highlighted the complexities of the mechanical/electrochemical interactions occurring during erosion-corrosion. An important feature is the influence of micro-galvanic interactions at phase boundaries. The impact of the findings has been discussed in terms of CCI alloy selection and corrosion control strategies

Comparison of hot wire TIG stellite 6 weld cladding and lost wax cast stellite 6 under corrosive wear conditions

This study compares Hot Wire Tungsten Inert Gas Stellite 6 weld cladding on a low carbon steel substrate with a lost wax cast Stellite 6 in impingement erosion-corrosion conditions. Austenitic stainless steel samples were used as a reference material. Tests were conducted in a closed loop impinged slurry vessel with a jet velocity of 18 m/s with 3.5%NaCl aqueous solution containing 500 µm spherical silica sand particles (0.5 g/l sand concentration). The testing temperature was 40 °C. Mass loss measurements and a volumetric analysis as well as microstructural evaluation were used as post-test analysis techniques. Results showed that weld cladding and lost wax cast Stellite 6 performed better than the stainless steel, with the weld cladding marginally outperforming the lost wax cast technique