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Functionally Graded Additive Manufacturing of Thin-Walled 316L Stainless Steel-Inconel 625 by Direct Laser Metal Deposition Process : Characterization and Evaluation
Full text linkDirect Laser Metal Deposition (DLMD) is a state-of-the-art manufacturing technology used to fabricate 316L stainless steel/Inconel 625 functionally graded material (FGMs) in this research. For the practical application of these materials in the industry, the effects of process parameters on the geometric characteristics and surface roughness require more investigation. This FGM was additively manufactured in five layers by changing the 316L stainless steel/Inconel 625 ratio in each layer. The effects of laser power on geometric characteristics, height stability, and surface roughness were investigated. The microstructural analysis and microhardness profiles were studied. The results show that despite the high solidification rate, the segregation of alloying elements into dendritic areas occurred. It was also found that increasing the laser power will increase the height, width, height stability, and surface roughness of the gradient walls. The maximum width and height of the deposited layers were 1.615 and 6.42 mm, respectively, at the highest laser power (280 W). At the laser power of 220 W, the least surface roughness (Ra = 105 µm) and the best height stability (0.461 mm) will be obtained. The microhardness values will differ in various sections of the gradient walls in a range of 225–277 HV
Influence of the different nanostructures of acrylonitrile butadiene styrene/carbon nanotubes nanocomposites on laser cutting properties: Machining and chemical aspects
Full text linkReported on in depth for the first time herein is the influence of the diverse nanostructures of acrylonitrile butadiene styrene (ABS)/multi-walled carbon nanotubes (MWCNTs) on its chemical, physical and electrical properties after laser cutting. Injection moulding was used to fabricate the nanocomposite samples in various structures with a thickness of 3 mm by adjusting temperature and pressure. The samples’ nanostructures were evaluated prior to cutting with a CO2 laser. Design of experiments (DoE) by a full-factorial method used three levels laser power 45, 55 and 65 W) and the cutting velocity at three levels (4, 8 and 12 mm/s) as independent variables. The findings from this work are significant and support new theories. It was revealed different surface damage modes such as shrink holes, cracks, decomposed smithereens and sink marks. These were affected by the laser energy density criterion which means that the ratio of power to cutting velocity was the governing factor, whilst the effect of primary nanostructures was negligible. Unlike surface damage, the width of heat affected zone (HAZ) was found to depend on the thermal conductivity, which directly relates to the samples’ nanostructure. Minimum HAZ was obtained at 0.45 mm for the sample with maximum thermal conductivity equal to 0.23 W/mK. Analysis of the post-laser cut surface and HAZ indicated that the MWCNTs were well dispersed with higher orientation and degrees of distribution. This, naturally, allows the inference that application of low laser energy density accounted for and governed oxidation of these regions. The results show that the nanotexture of the post-laser cut surface is completely changed in comparison with the as-moulded surface, leading to the lowest reduction in surface electrical resistivity to 3.2 kΩ for the sample produced at a temperature of 220 ◦C and a holding pressure of 70 bar
Design and Analysis of a Typical Vertical Pressure Vessel using ASME Code and FEA Technique
Full text linkThis study aims to address the hazards associated with the design and manufacture of pressure vessels used for storing dangerous liquids, specifically focusing on the increased demand for liquefied petroleum gas (LPG) worldwide. The construction of more LPG facilities necessitates the implementation of safer pressure vessels to mitigate risks such as explosions and leakage. The primary objective of this project is to design a vertical pressure vessel, in accordance with the American Society of Mechanical Engineers (ASME) code, capable of safely storing 10 m3 of pressurised LPG. To ensure the safety of the pressure vessel, the researchers employed Autodesk Inventor Professional 2023 for geometric modelling and utilised Inventor Nastran for finite element analysis (FEA) to investigate displacements, deflections, and von Mises stresses. The vessel is cylindrical in shape and features two elliptical heads, two nozzles, a manway, and four leg supports. The FEA analysis conducted using Autodesk Inventor Nastran enabled the researchers to identify areas where structural modifications were necessary to reduce stress within the vessel. The results revealed an inverse relationship between the displacement and the tank section shell thickness. Additionally, the factor of safety exhibited a linear increase as the shell thickness increased. The researchers carefully considered permissible pressures and determined the required wall thickness to maintain acceptable maximum stresses. The findings indicate that the design of the pressure vessel is safe from failure. Among the components, the manway experiences the highest stresses, followed by the shell, while the heads, nozzles, and leg supports experience lower stresses. The researchers also conducted theoretical calculations for the entire model and ensured that the results fell within acceptable limits, further validating their design approach. The research emphasised the importance of designing pressure vessels in compliance with ASME codes to ensure safety and prevent hazards associated with improper design and manufacturing. The combination of Autodesk Inventor Professional and Inventor Nastran proved to be an effective approach for simulating and evaluating the performance of the pressure vessel. Through the analysis, the researchers found that changes to the pressure vessel structure were necessary to reduce stress. They observed an inverse relationship between displacement and tank section shell thickness, while the factor of safety increased linearly with shell thickness. Stress distribution analysis revealed that the manway and shell experienced the highest stresses, while the heads, nozzles, and leg support exhibited lower stresses. Employing the finite element method, potential stress points within the pressure vessel were identified, enabling necessary modifications to enhance its safety
Numerical approach for flexible body with internal boundary movement
Full text linkIn this paper, a numerical method is proposed for a flexible tether motion that spans two different environments and has large displacement and deformation. When considering the behavior of a tethered system in which the tether cable is subjected to the above conditions, variations of an internal boundary in the tether must be considered. In general, the absolute nodal coordinate formulation (ANCF), a nonlinear finite element method, is effective for the dynamic simulation of a flexible body with large displacement and deformation. However, in conventional methods, such as ANCF, the analysis accuracy decreases and the calculation cost increases when the movement of an internal boundary across different environments is considered. In this study, an efficient numerical approach that considers the variations of an internal boundary by using ANCF using variable-domain finite elements is proposed. In addition, to further improve the calculation efficiency, dimensionless variables are introduced using appropriate representative values. The accuracy of the numerical results obtained using the proposed method, which considers an internal variable boundary, is similar to that for a conventional method
Genetic distance and cross-border M&A completion: Evidence from Chinese firms
Full text linkUsing data drawn from Chinese firms from 1996 to 2019, we explored the effect of genetic distance on the completion of cross-border merger and acquisition (M&A). We found an inverted U-shaped relationship between genetic distance and cross-border M&A completion. Further research showed that this relationship is moderated by heterogeneity at the firm-, industry-, and country-levels. In particular, when the acquirer is a foreign-listed company and the host country institution is of good quality, genetic distance has a linear positive effect on M&A completion. When the acquirer belongs to the high-tech industry and the two countries involved have not signed any bilateral investment treaties, the effect of genetic distance is not significant. Our study sheds light on the impact of genetic distance on cross-border M&A completion and enriches the related theoretical perspective. Our findings also have a certain practical value
Birthing outside the guidelines: a qualitative study of student midwives' experiences
Full text linkBackground Choice in childbirth is not a new concept, yet it has been suggested that few service-users have a genuine choice about birth. Existing research has explored midwives' experiences of caring for service users birthing outside guidelines, but nothing is known about student midwives' experiences. This study's aim was to explore student midwives' experiences of caring for women giving birth outside the guidelines. Methods A generic qualitative approach was used, and purposive sampling recruited five student midwives from a university in east England. Data were collected using semi-structured interviews and analysed thematically. Results The three themes were ‘contradictions’, focusing on the incongruity identified in the narratives, ‘the actions of clinicians’ illustrated by clinician behaviour witnessed by the participants and ‘punishment and judgement’, which outlines the treatment of service users who gave birth outside the guidelines. Conclusions Students can be exposed to inapt clinicians' behaviours, with the failure to protect and advocate for service users leaving them feeling anxious and potentially burnt out. Midwives should act as role models, so future midwives are aware this behaviour is not conducive to person-led care
A Rapid Evidence Review of Clinical Risk Factors for Poor Perinatal Mental Health in Women's Prisons in England
Full text linkPregnancy and the first year after childbirth are a high-risk period of a woman's life, and research shows that women in prison are at heightened risk for poor mental health, self-harm and suicide. Whilst there has been a recent focus on studies into the health care for women in prison, research looking into the specific risk factors for poor perinatal mental health in women's prisons is sparse, with the majority having been conducted within a U.S. context that will have different provisions available and population need. This rapid evidence review explored academic literature published to identify clinical risk factors of poor perinatal mental health for women in prison in England. Following the initial search, 21 documents were identified which were then thematically analysed resulting in the identification of 72 clinical risk factors. Meta-themes identified included ‘individual’, ‘relationships’, ‘prison context’, ‘provision ’and ‘processes’. The recognition and mitigation of identified clinical risk factors is critical to ensuring quality care for women in prison and reduction of poor perinatal mental health
Experimental and response surface study on additive manufacturing of functionally graded steel-inconel wall using direct laser metal deposition
Full text linkIn the present study, the effective parameters in the Direct Laser Metal Deposition Method (DLMD) of SS316L-Inconel 625 grade material were investigated. A 1000 W continuous-wave fiber laser was used to manufacture a five-layered gradient wall. The weight percentages of Inconel 625 and SS316L were different in each layer. Response Surface Methodology (RSM) was used to study the effects of scanning speed and laser power -each in three levels- on the average width, surface roughness, average microhardness, standard deviation of the width, and standard deviation of the height of the gradient walls. Also, the microstructure of the gradient walls was investigated using SEM images and EDS analysis. The results showed that the average width and surface roughness of the walls would increase by decreasing the scanning speed and increasing the laser power. The increase in the scanning speed and decrease in the laser power decreased the standard deviation of the width and the height of the walls. The lowest surface roughness of 96 µm was obtained at the highest scanning speed of 200 mm/min while the lowest values of the standard deviation of the width and standard deviation of height were 76 and 70 μm, respectively at this speed. It was also found that the microhardness value increased significantly with the increase in the scanning speed due to the higher solidification rate
The experiences of new primary school special educational needs coordinators: presenting the SENCO voice through concept‐drawing and personal narratives
Full text linkThrough a narrative informed study, using concept drawing, ten newly appointed primary school Special Educational Needs Coordinators (SENCOs) drawn from across three Local Authority areas at the start of their compulsory training, reflect upon and share their experiences at this early point in their SENCO career. Their experiences reveal that they like being SENCOs due to the support they provide for their pupils and professional colleagues together with the positive differences they perceive they make in terms of improved outcomes for children with special educational needs (expressed as their ‘Psychological Contract’). However, this is set against a climate which impacts negatively on their ability to meet the requirements of current legislation and statutory guidance (expressed as their Legal Contract). This climate is created through the Contextual Variety which exists between schools as they have their own culture/ethos which can result, as reported in this study, by SENCOs facing an excessive (and increasing) administrative workload, a general lack of resources, limited protected time, limited understanding about the role and special educational needs in general held by their colleagues and limited opportunities to develop as school leader
The role of vancomycin-soaking of the graft in anterior cruciate ligament reconstruction
Full text linkApproximately 1% of anterior cruciate ligament reconstruction (ACLR) procedures develop septic arthritis despite intravenous antibiotic prophylaxis and other preventive measures. Infection is most commonly due to contamination during autograft harvest and preparation by introducing bacteria into the knee during graft insertion. Pre-soaking ACL grafts in 5 mg/mL vancomycin ("vancomycin wrap") has been utilised to eradicate such bacterial contamination. Many level III studies have reported a marked decrease in infection rates with no increase in graft failure rates. However, the lack of prospective randomised control trials and these studies' heterogeneity do not allow a universal recommendation for vancomycin pre-soaking of all grafts during ACLR. Randomised controlled trials are needed to confirm efficacy in reducing sepsis rates. [Abstract copyright: Crown Copyright © 2022. Published by Elsevier Inc. All rights reserved.
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