16 research outputs found
Influence of Tool Geometry and Process Parameters on the Properties of Friction Stir Spot Welded Multiple (AA 5754 H111) Aluminium Sheets.
Friction stir spot welding is an emerging spot-welding technology that offers opportunities for joining a wide range of materials with minimum energy consumption. To increase productivity, the present work addresses production challenges and aims to find solutions for the lap-welding of multiple ultrathin sheets with maximum productivity. Two convex tools with different edge radii were used to weld four ultrathin sheets of AA5754-H111 alloy each with 0.3 mm thickness. To understand the influence of tool geometries and process parameters, coefficient of friction (CoF), microstructure and mechanical properties obtained with the Vickers microhardness test and the small punch test were analysed. A scanning acoustic microscope was used to assess weld quality. It was found that the increase of tool radius from 15 to 22.5 mm reduced the dwell time by a factor of three. Samples welded with a specific tool were seen to have no delamination and improved mechanical properties due to longer stirring time. The rotational speed was found to be the most influential parameter in governing the weld shape, CoF, microstructure, microhardness and weld efficiency. Low rotational speeds caused a 14.4% and 12.8% improvement in joint efficiency compared to high rotational speeds for both tools used in this investigation
How patients and families describe major medical treatments: They are no longer living, just existing
Background: As more life-sustaining treatments become available, the need to provide patients and families clarity about what these treatments are and what they do is increasing. Little is known about how patients and families conceptualize life support.
Objective: To explore the discourse that patients and families used to describe major medical treatments in their accounts of treatment decision-making.
Methods: This study is a secondary data analysis of a survey sent to random addresses in Wisconsin regarding experiences with major medical treatment decision-making. This analysis includes the subsample of 366 respondents who specified the type of decision made in the survey\u27s open-ended questions. Inductive content analysis was used to qualitatively analyze the responses to the open-ended questions, with particular attention to how respondents described the treatment in their responses.
Results: Respondents\u27 descriptions showed a conceptualization of engaging in major medical treatments as keeping patients alive, whereas discontinuing or choosing not to engage in such treatments would bring about the patient\u27s death. However, respondents recognized the potential adverse consequences of engaging in major medical treatments, such as their capacity to cause pain or result in an undesirable neurologic state. Additionally, respondents described the limitations of such treatment regarding the uncertainty of the treatments providing the desired outcome or their uselessness in situations in which the patient\u27s death would be inevitable.
Conclusion: Understanding how patients and families make sense of major medical treatments can help clinicians during decision-making conversations
Oxygen permeation and creep behavior of Ca1-xSrxTi0.6Fe0.15Mn0.25O3-δ (x=0, 0.5) membrane materials
Oxygen permeation measurements were performed on dense symmetric samples of Ca0.5Sr0.5Ti0.6Fe0.15Mn0.25O3âδ and compared to CaTi0.6Fe0.15Mn0.25O3âδ in order to assess the influence of the perovskite lattice volume on oxygen permeation. Oxygen flux measurements were performed in the temperature range 700â1000 °C and as function of feed side pO2 from 10â2 to 1 bar, and at high pressures up to 4 bar with a pO2 of 3.36 bar. The O2 permeability of the Sr-doped sample was significantly lower than that of the Sr-free sample, amounting to 3.9Ă10â3 mL minâ1 cmâ1 at 900 °C for a feed side pO2 of 0.21 bar. The O2 permeability of CaTi0.6Fe0.15Mn0.25O3âδ shows little variation with increased feed side pressures and reaches 1.5Ă10â2 mL minâ1 cmâ1 at 900 °C for a feed side pO2 of 3.36 bar. This is approximately 1.5 times higher than the O2 permeability with a feed side pO2 of 0.21 bar. Furthermore, in order to assess the applicability of CaTi0.6Fe0.15Mn0.25O3âδ as an oxygen membrane material, creep tests were performed under compressive loads of 30 and 63 MPa, respectively, in air in the temperature range 700â1000 °C; the results indicate a high creep resistance for this class of materials. The measured O2 permeabilities and creep rates are compared with other state-of-the-art membrane materials and their performance for relevant applications is discussed in terms of chemical and mechanical stability.acceptedVersio
Solution, solid state and biological characterization of ruthenium(III)-DMSO complexes with purine base derivatives.
Mechanical characterization of ceramics by means of a 3D defect analysis
A three-dimensional defect study was carried out on CaTi0.9Fe0.1O3âd ceramic membrane material as a model study for the use of computed tomography in both microstructural analysis and mechanical characterization. The study demonstrated many advantages over the commonly used fractographic study which is also presented in this paper. The data obtained by computed tomography were further used for mechanical modeling and prediction of materialâs behavior based on finite element analysis, where the stress state was also analyzed by varying the defectâs position and the loading configuration. The results obtained by these techniques were validated by microstructural studies, mechanical experiments and fractographic analysis. The fracture strength of the tested material was determined and compared to other potential membrane materials
Recommended from our members
Itâs Big Surgery: Preoperative Expressions of Risk, Responsibility, and Commitment to Treatment after High-risk Operations
Objective
To identify the processes surgeons use to establish patient buy-in to postoperative treatments.
Background
Surgeons generally believe they confirm the patient's commitment to an operation and all ensuing postoperative care, before surgery. How surgeons get buy-in and whether patients participate in this agreement is unknown.
Methods
We used purposive sampling to identify three surgeons from different subspecialties who routinely perform high-risk operations at each of three distinct medical centers (Toronto, ON; Boston, MA; Madison, WI). We recorded preoperative conversations with three to seven patients facing high-risk surgery with each surgeon (n = 48) and used content analysis to analyze each preoperative conversation inductively.
Results
Surgeons conveyed the gravity of high-risk operations to patients by emphasizing the operation is âbig surgeryâ and that a decision to proceed invoked a serious commitment for both the surgeon and the patient. Surgeons were frank about the potential for serious complications and the need for intensive care. They rarely discussed the use of prolonged life-supporting treatment, and patientsâ questions were primarily confined to logistic or technical concerns. Surgeons regularly proceeded through the conversation in a manner that suggested they believed buy-in was achieved, but this agreement was rarely forged explicitly.
Conclusions
Surgeons who perform high-risk operations communicate the risks of surgery and express their commitment to the patient's survival. However, they rarely discuss prolonged life-supporting treatments explicitly and patients do not discuss their preferences. It is not possible to determine patientsâ desires for prolonged postoperative life support based on these preoperative conversations alone
Oxygen permeation and creep behavior of Ca1-xSrxTi0.6Fe0.15Mn0.25O3-δ (x=0, 0.5) membrane materials
Oxygen permeation measurements were performed on dense symmetric samples of Ca0.5Sr0.5Ti0.6Fe0.15Mn0.25O3âδ and compared to CaTi0.6Fe0.15Mn0.25O3âδ in order to assess the influence of the perovskite lattice volume on oxygen permeation. Oxygen flux measurements were performed in the temperature range 700â1000 °C and as function of feed side pO2 from 10â2 to 1 bar, and at high pressures up to 4 bar with a pO2 of 3.36 bar. The O2 permeability of the Sr-doped sample was significantly lower than that of the Sr-free sample, amounting to 3.9Ă10â3 mL minâ1 cmâ1 at 900 °C for a feed side pO2 of 0.21 bar. The O2 permeability of CaTi0.6Fe0.15Mn0.25O3âδ shows little variation with increased feed side pressures and reaches 1.5Ă10â2 mL minâ1 cmâ1 at 900 °C for a feed side pO2 of 3.36 bar. This is approximately 1.5 times higher than the O2 permeability with a feed side pO2 of 0.21 bar. Furthermore, in order to assess the applicability of CaTi0.6Fe0.15Mn0.25O3âδ as an oxygen membrane material, creep tests were performed under compressive loads of 30 and 63 MPa, respectively, in air in the temperature range 700â1000 °C; the results indicate a high creep resistance for this class of materials. The measured O2 permeabilities and creep rates are compared with other state-of-the-art membrane materials and their performance for relevant applications is discussed in terms of chemical and mechanical stability