Computational modeling of creep-based fatigue as a means of selecting lead-free solder alloys

The primary aim of this investigation was to understand the effect of temperature fluctuations on a number of various solder materials namely SAC105, SAC305, SAC405 and Sn–36Pb–2Ag. To achieve this objective, three different classic joint assemblies (a ball joint, a test specimen joint and finger lead joint) were modeled which provided the foundation for the creep and fatigue behaviors simulation. Anand’s viscoplasticity as a constitutive equation was employed to characterize the behavior of solders numerically under the influence of thermal power cycles (80–150 °C) and thermal shock cycles (−40 to 125 °C). To extend the research outcome for industrial use, two additional research activities were carried out. One of them was to obtain lifetime-predictions of solder joints based on Coffin Manson concept. The other one focused on parameterization to obtain the ideal solder thickness under the consideration of plastic strain and economic benefit

Investigating the thermal profile of a marine vessel engine room through simulation with field measurements

This paper assesses the use of computational fluid dynamics (CFD) to model the ventilation of a working marine vessel, its performance in extreme climates, and potential improvements to the ventilation system which could lead to increased efficiencies of the engine and generator set.Comparisons between data gathered on the marine vessel and the computational model show good agreement, with an average discrepancy in temperature of 0.4%. The model showed that the current ventilation system was inadequate for the use of the marine vessel in Arctic waters. In contrast, the model showed the vessel was suited for tropical waters, and that the boat complied with British Standards for ventilation.Directing the flow within the engine room was found to improve the overall cooling of the room, and reduce the range of temperatures to improve thermal comfort. Directing the flow has shown reduced intake temperatures of the engine and generator set, improving efficiencies by 0.5% and 0.57% respectively. This paper demonstrates that the use of CFD to model marine vessel engine rooms can be used in retrospective design of ventilation systems, furthermore, it can be a tool utilised in the design stages for optimised engine rooms ventilation systems

Investigation into the effect of process parameters on microstructural and physical properties of 316L stainless steel parts by selective laser melting

Additive manufacturing by selective laser melting (SLM) was used to investigate the effect of laser energy density on 316L stainless steel properties. Point distance and exposure time were varied and their impact on porosity, surface finish, microstructure, density and hardness, was evaluated. The surface roughness was primarily affected by point distance with increased point distance resulting in increased surface roughness, R a, from 10 to 16 μm. Material hardness reached a maximum of 225 HV at 125 J/mm3 and was related to the material porosity; with increased porosity leading to decreased material hardness. Different types of particle coalescence leading to convex surface features were observed (sometimes referred to as balling); from small ball features at low laser energy density to a mixture of both small and large ball features at high laser energy density. Laser energy density was shown to affect total porosity. The minimum amount of porosity, 0.38 %, was observed at an energy density of 104.52 J/mm3

High temperature nanoindentation up to 800°C for characterizing high temperature properties of materials

One of the primary motivations for development of instrumented indentation was to measure the mechanical properties of thin films. Characterization of thin film mechanical properties as a function of temperature is of immense industrial and scientific interest. The major bottlenecks in variable temperature measurements have been thermal drift, signal stability (noise) and oxidation of/condensation on the surfaces. Thermal drift is a measurement artifact that arises due to thermal expansion/contraction of indenter tip and loading column. This gets superimposed on the mechanical behavior data precluding accurate extraction of mechanical properties of the sample at elevated temperatures. Vacuum is essential to prevent sample/tip oxidation at elevated temperatures. In this poster, the design and development of a novel nanoindentation system that can perform reliable load-displacement measurements over a wide temperature ranges (from -150 to 800 °C) will be presented emphasizing the procedures and techniques for carrying out accurate nanomechanical measurements. This system is based on the Ultra Nanoindentation Tester (UNHT) that utilizes an active surface referencing technique comprising of two independent axes, one for surface referencing and another for indentation. The differential depth measurement technology results in negligible compliance of the system and very low thermal drift rates at high temperatures. The sample, indenter and reference tip are heated/cooled separately and the surface temperatures matched to obtain drift rates as low as 1nm/min at 800 °C without correction. Instrumentation development, system characterization, experimental protocol, operational refinements and thermal drift characteristics over the temperature range will be presented, together with a range of results on different materials. Please click Additional Files below to see the full abstract

The influence of powder ageing characteristics on 316l stainless steel processed by laser based powder bed fusion

The past 3-4 years has seen a transition in the use of Additive Manufacturing techniques from prototyping to series production. There remain a number of technical challenges that need to be resolved in order to increase adoption of the technology across a wider range of markets, one of which is improved part-to-part consistency. It is recognised that one factor that can influence the consistency of the laser based powder bed fusion process is the ageing of the metal powder used to manufacture parts, that is to say how the properties of the powder change following repeated used in repeated build cycles. Whilst commercial powder producers can exercise tight control over the 'as received' powder, changes that can subsequently occur following exposure to repeated process cycles in the laser beam melting machine warrant separate investigation

The prevalence of mild to moderate distress in patients with end stage renal disease:results from a patient survey using the emotion thermometers in four hospital Trusts in the West Midlands, UK

Objectives To assess the prevalence of mild-To-moderate distress in patients with end-stage renal disease (ESRD) and determine the association between distress and patient characteristics. Design Cross-sectional survey using emotion thermometer and distress thermometer problem list. Setting Renal units in four hospital Trusts in the West Midlands, UK. Participants Adult patients with stage 5 chronic kidney disease who were: (1) On prerenal replacement therapy. (2) On dialysis for less than 2 years. (3) On dialysis for 2 years or more (4) With a functioning transplant. Outcomes The prevalence of mild-To-moderate distress, and the incidence of distress thermometer problems and patient support needs. Results In total, 1040/3730 surveys were returned (27.9%). A third of survey respondents met the criteria for mild-To-moderate distress (n=346; 33.3%). Prevalence was highest in patients on dialysis for 2 years or more (n=109/300; 36.3%) and lowest in transplant patients (n=118/404; 29.2%). Prevalence was significantly higher in younger versus older patients (χ 2 =14.33; p=0.0008), in women versus men (χ 2 =6.63; p=0.01) and in black and minority ethnic patients versus patients of white ethnicity (χ 2 =10.36; p=0.013). Over 40% of patients (n=141) reported needing support. More than 95% of patients reported physical problems and 91.9% reported at least one emotional problem. Conclusions Mild-To-moderate distress is common in patients with ESRD, and there may be substantial unmet support needs. Regular screening could help identify patients whose distress may otherwise remain undetected. Further research into differences in distress prevalence over time and at specific transitional points across the renal disease pathway is needed, as is work to determine how best to support patients requiring help.</p

Design and development of a reduced form-factor high accuracy three-axis teslameter

Acknowledgments: The authors would like to thank Reuben Debono for his useful guidance and help in the PCB assembly of the instruments at the Electronic Systems Lab at the Faculty of Engineering at University of Malta. The authors would like to thank R. Ganter, project leader of the Athos undulator beamline and H-H. Braun, SwissFEL machine director, for their constant support throughout the entire project. The authors would like to thank Sasa Spasic and his team at Sentronis facilities for their fruitful discussions and their guidance during testing.A novel three-axis teslameter and other similar machines have been designed and developed for SwissFEL at the Paul Scherrer Institute (PSI). The developed instrument will be used for high fidelity characterisation and optimisation of the undulators for the ATHOS soft X-ray beamline. The teslameter incorporates analogue signal conditioning for the three-axes interface to a SENIS Hall probe, an interface to a Heidenhain linear absolute encoder and an on-board high-resolution 24-bit analogue-to-digital conversion. This is in contrast to the old instrumentation setup used, which only comprises the analogue circuitry with digitization being done externally to the instrument. The new instrument fits in a volumetric space of 150 mm × 50 mm × 45 mm, being very compact in size and also compatible with the in-vacuum undulators. This paper describes the design and the development of the different components of the teslameter. Performance results are presented that demonstrate offset fluctuation and drift (0.1–10 Hz) with a standard deviation of 0.78 µT and a broadband noise (10–500 Hz) of 2.05 µT with an acquisition frequency of 2 kHz.peer-reviewe

Topical Flunixin Meglumine Effects on Pain Associated Biomarkers after Dehorning

Twenty-four calves were dehorned and treated with either topical flunixin meglumine formulated for systemic absorption or a placebo. Biomarkers associated with pain were evaluated for up to 72 hour after the dehorning procedure. Plasma cortisol concentrations, 90 minutes post-dehorning, and mechanical nociception threshold at the control site were the only tested biomarkers where a significant difference was demonstrated. No other differences of biomarkers between the two dehorned groups were observed for any time points. Although this product is easy to dose and dispense, its effects on pain biomarkers appears to be negligible

The use of the RenalGuard system in cardiac surgery with cardiopulmonary bypass: a first in man prospective, observational, feasibility pilot study

Objectives As proof of concept, this prospective, observational study assessed the feasibility and early clinical outcomes of performing on-pump cardiac surgery with the RenalGuard system. Background Acute kidney injury (AKI) is reported in up to 30% of patients undergoing cardiac surgery and is a recognised independent predictor of both morbidity and mortality. Forced diuresis with the RenalGuard system reduces the incidence of AKI during percutaneous coronary intervention procedures but its use in cardiac surgery has not been explored. Methods Ten consecutive patients who were at risk of developing AKI during cardiac surgery were selected. The RenalGuard system was used to facilitate forced diuresis using weight-adjusted intravenous furosemide while maintaining neutral fluid balance by matched intravenous fluid replacement. This regimen was initiated preoperatively in all patients and continued for 6–12 hours postoperatively. Serum creatinine, electrolytes and need for renal replacement were documented in all patients. Results The RenalGuard system functioned successfully in all patients and facilitated high perioperative urine outputs, even when patients were placed on cardiopulmonary bypass (CPB). There were no incidences of significant (A) electrolyte imbalance, (B) changes in haemoglobin levels or (C) pulmonary oedema. No patients developed AKI within 36 hours of surgery despite one patient developing cardiac tamponade 8 hours postoperatively and one patient developing paralytic ileus. One patient, however, was ‘electively’ haemofiltered on day 2 after developing acute right ventricular failure. The median intensive care stay was 1.5 (1, 5) days. Conclusion The RenalGuard system can be used successfully in patients undergoing cardiac surgery with CPB and may reduce the incidence of AKI in at-risk patients