| 1. |
- Hemphälä, Hillevi, et al.
(author)
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A method for risk assessment within Visual Ergonomics
- 2015
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In: Proceedings of the 19th Triennial Congress of the International Ergonomics Association. ; , s. nr 1203-
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Conference paper (peer-reviewed)abstract
- IntroductionInsufficient visual ability can lead to increased work load and contribute to eyestrain and musculoskeletal discomfort, since “the eye leads the body” (Anshel, 2005). It has been shown that visually demanding work, such as computer work, is associated with eye discomfort, headaches and muscle pains in mainly the neck and shoulders (Rosenfield, 2011).Although the relation between eyestrain and musculoskeletal discomfort is not fully understood, studies have shown that straining the eyes increases the musculoskeletal activity in neck and shoulders (trapezius), and an association between visually demanding work, eye problems, headache and/or muscle problems have been found (Aarås et al., 2001; IESNA, 2011, Richter et al., 2008; Zetterberg et al., 2013). Problems due to insufficient visual ergonomics not only exist in computer intensive jobs, but in other professions as well. For example, surgeons and other surgical personnel that report eyestrain also report twice as much musculoskeletal discomfort from the upper part of the body (Hemphälä et al., 2011). In an intervention study among postmen, both eyestrain and musculoskeletal discomfort decreased after a visual ergonomic intervention. The intervention included providing customized eyeglasses and optimal lighting conditions (Hemphälä et al., 2012). Apart from health and well-being being affected by a poor visual ergonomic work environment, quality and productivity may also be reduced (Eklund, 2009).The aim of this paper is to present the first version of a practical, easy-to-use, and time-efficient risk assessment method for visual ergonomics. The development of the method including the evaluation will also be described. With such a method, risk factors within the visual environment can hopefully be detected, and interventions implemented in order to reduce the prevalence of symptoms related to poor visual ergonomics among workers.MethodsA first version of the method has been developed, mainly based on existing checklists and instruments (Colon et al. 1999; Børsting et al., 2008, Knave et al., 1985, Sheedy and Shaw-McMinn, 2002; Wilson & Corlett, 2005). During spring 2015, 30 ergonomists will be updated about visual ergonomics and introduced to the risk assessment method. Each ergonomist will thereafter use the method in 10 workplaces, yielding data and practical experiences from 300 risk assessments. These data will then be used to test the validity and reliability of the method, and if necessary to further develop it.ResultsThe first version of the risk assessment method for Visual Ergonomics will be presented at IEA 2015, together with results from the approximately 300 risk assessments made by the ergonomists. So far, the factors included in the method are objective measurements such as illuminance, luminance contrast, uniformity values, expert assessment of the risk for glare, and subjective ratings of the visual ability, eyestrain and musculoskeletal discomfort.DiscussionThe presented method will be compared to other similar methods. The used method for development will be discussed in relation to validity and reliability. Finally the presented risk assessment method will be discussed in relation to usefulness in prevention of discomfort and work related disorders at work places.
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| 2. |
- Ganvir, Ashish, 1991-, et al.
(author)
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Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings
- 2016
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In: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 25:1-2, s. 202-212
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Journal article (peer-reviewed)abstract
- Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.
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| 3. |
- Hemphälä, Hillevi, et al.
(author)
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A method for assessing risks within visual ergonomics
- 2014
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In: 11th International Symposium on Human Factors in Organisational Design and Management & 46th Annual Nordic Ergonomics Society Conference. - Santa Monica, CA, USA : The IEA PRESS. - 9788793130135 ; , s. 111-112
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Conference paper (peer-reviewed)abstract
- 1. IntroductionInsufficient visual ability can lead to strained work load for employees and can contribute to eyestrain and musculoskeletal discomfort, “the eye leads the body” (Anshel, 2005). An optimal visual environment provides physical conditions for work in the best possible way. Visually demanding work, such as computer work, is associated with eye discomfort, headaches and muscle pains in mainly the neck and shoulders (Rosenfield, 2011). For computer workers in North America studies show that 75-90 % of the workers reported subjective symptoms from the eyes (Anshel, 2005). The causality between eyestrain and musculoskeletal discomfort is not fully understood, but studies have shown that straining the eyes increases the musculoskeletal activity in neck and shoulders (trapezius), and a link between visually demanding work, eye problems, headache and/or muscle problems have been found (Aarås et al., 2001; Richter et al., 2008; Zetterlund et al., 2009; Zetterberg et al., 2013). A study of call-center workers in Sweden showed that 21% of workers have both eyes and neck problems (Wiholm et al., 2007). Ergonomic problems also exist for professions where computer work is not dominant. Surgeons and other surgical personnel, with subjective eye discomfort, reported twice the incidence of musculoskeletal disorders when compared with staff without eye symptoms (Hemphälä et al., 2011). In an intervention study among postmen the eyestrain and musculoskeletal discomfort decreased after visual ergonomic interventions including customized eyeglasses and optimal lighting conditions (Hemphälä et al., 2012). Apart from health and well-being being affected by a poor visual ergonomic work environment, the quality and productivity are also involved (Eklund, 2009).Lighting is an important factor; both the lighting quantity (strength) and quality (e.g. light distribution, direction, glare and contrast). Too low illumination makes it difficult to see clearly and may thus lower performance, high illuminance can cause glare and lead to increased eye fatigue and decreased productivity (IESNA, 2011).2. MethodsThere are several factors to consider when developing a method for visual ergonomics risk assessment of subjective symptoms and discomfort of the eyes (Colon et al. 1999; Børsting et al., 2008, Knave et al., 1985). There are also checklists used in eye exams or medical appointments (Sheedy and Shaw-McMinn, 2002; Wilson & Corlett, 2005). These will be used as basis in the presents the project intended to develop a risk assessment instrument for visual ergonomics.3. ResultsA preliminary version of a risk analysis method for Visual Ergonomics has been developed and will be presented, with a focus on discussing with the audience which factors should primarily be included. The factors included so far in the method are the objective measurements such as illuminance, luminance contrast, uniformity values, expert assessment of the risk for glare; indirect measurements such as subjective ratings of the visual ability, eyestrain and musculoskeletal discomfort. The goal is to develop a practical time efficient method that is easy to use. With such a tool, actions needed to reduce the visual load among the workers, the companies and the society’s negative consequences induced by work-related eyestrain and musculoskeletal discomfort can hopefully be identified.
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| 4. |
- Joshi, Shrikant V., 1960-, et al.
(author)
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Advanced Coatings by Thermal Spray Processes
- 2019
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In: Technologies. - : MDPI. - 2227-7080. ; 7:4, s. 1-14
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Journal article (peer-reviewed)abstract
- Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of other in-chamber processes. Consequently, TS techniques like high-velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS) are industrially well-accepted. However, they have reached limits of their capabilities while expectations from coatings progressively increase in pursuit of enhanced efficiency and productivity. Two emerging TS variants, namely high-velocity air-fuel (HVAF) and liquid feedstock thermal spraying, offer attractive pathways to realize high-performance surfaces superior to those hitherto achievable. Supersonic HVAF spraying provides highly adherent coatings with negligible porosity and its low processing temperature also ensures insignificant thermal ‘damage’ (oxidation, decarburization, etc.) to the starting material. On the other hand, liquid feedstock derived TS coatings, deposited using suspensions of fine particles (100 nm–5 µm) or solution precursors, permits the production of coatings with novel microstructures and diverse application-specific architectures. The possibility of hybrid processing, combining liquid and powder feedstock, provides further opportunities to fine tune the properties of functional surfaces. These new approaches are discussed along with some illustrative examples.
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| 5. |
- Joshi, Shrikant V., 1960-, et al.
(author)
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New Generation Ceramic Coatings for High-Temperature Applications by Liquid Feedstock Plasma Spraying : Defense, Security, Aerospace and Energy Applications
- 2020
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In: Handbook of Advanced Ceramics and Composites. - Cham : Springer. - 9783319732558 ; , s. 1-42
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Book chapter (other academic/artistic)abstract
- Plasma spraying with liquid feedstock offers an exciting opportunity to obtain coatings with characteristics that are vastly different from those produced using conventional spray-grade powders. The two extensively investigated variants of this technique are suspension plasma spraying (SPS), which utilizes a suspension of fine powders in an appropriate medium, and solution precursor plasma spraying (SPPS), which involves use of a suitable solution precursor that can form the desired particles in situ. The advent of axial injection plasma spray systems in recent times has also eliminated concerns regarding low deposition rates/efficiencies associated with liquid feedstock. The 10–100 μm size particles that constitute conventional spray powders lead to individual splats that are more than an order of magnitude larger compared to those resulting from the fine (approximately 100 nm–2 μm in size) particles already present in suspensions in SPS or formed in situ in SPPS. The distinct characteristics of the resulting coatings are directly attributable to the above very dissimilar splats (“building blocks” for coatings) responsible for their formation. This chapter discusses the salient features associated with SPS and SPPS processing, highlights their versatility for depositing a vast range of ceramic coatings with diverse functional attributes, and discusses their utility, particularly for high-temperature applications through some illustrative examples. A further extension of liquid feedstock plasma processing to enable use of hybrid powder-liquid combinations for plasma spraying is also discussed. This presents a novel approach to explore new material combinations, create various function-dependent coating architectures with multi-scale features, and enable convenient realization of layered, composite, and graded coatings as demonstrated through specific examples.
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| 6. |
- Kumara, Chamara, et al.
(author)
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Microstructure modelling of laser metal powder directed energy deposition of alloy 718
- 2019
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In: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 25, s. 357-364
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Journal article (peer-reviewed)abstract
- A multi-component and multi-phase-field modelling approach, combined with transformation kinetics modelling, was used to model microstructure evolution during laser metal powder directed energy deposition of Alloy 718 and subsequent heat treatments. Experimental temperature measurements were utilised to predict microstructural evolution during successive addition of layers. Segregation of alloying elements as well as formation of Laves and δ phase was specifically modelled. The predicted elemental concentrations were then used in transformation kinetics to estimate changes in Continuous Cooling Transformation (CCT) and Time Temperature Transformation (TTT) diagrams for Alloy 718. Modelling results showed good agreement with experimentally observed phase evolution within the microstructure. The results indicate that the approach can be a valuable tool, both for improving process understanding and for process development including subsequent heat treatment.
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| 7. |
- Markocsan, Nicolaie, 1967-, et al.
(author)
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Liquid Feedstock Plasma Spraying : An Emerging Process for Advanced Thermal Barrier Coatings
- 2017
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In: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 26:6, s. 1104-1114
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Journal article (peer-reviewed)abstract
- Liquid feedstock plasma spraying (LFPS) involves deposition of ultrafine droplets of suspensions or solution precursors (typically ranging from nano- to submicron size) and permits production of coatings with unique microstructures that are promising for advanced thermal barrier coating (TBC) applications. This paper reviews the recent progress arising from efforts devoted to development of high-performance TBCs using the LFPS approach. Advancements in both suspension plasma spraying and solution precursor plasma spraying, which constitute the two main variants of LFPS, are presented. Results illustrating the different types of the microstructures that can be realized in LFPS through appropriate process parameter control, model-assisted assessment of influence of coating defects on thermo-mechanical properties and the complex interplay between pore coarsening, sintering and crystallite growth in governing thermal conductivity are summarized. The enhancement in functional performances/lifetime possible in LFPS TBCs with multilayered architectures and by incorporating new pyrochlore chemistries such as gadolinium zirconate, besides the conventional single 8 wt.% yttria-stabilized zirconia insulating ceramic layer, is specifically highlighted.
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| 8. |
- Bahbou, M. Fouzi, 1973-, et al.
(author)
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A parameter study of the Protal® Process to optimise the adhesion of Ni5Al Coatings
- 2004
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In: Thermal Spray 2004 : Advances in technology and applications. - 9780871708090 ; , s. 898-902
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Conference paper (peer-reviewed)abstract
- The Protal process combines surface preparation using a laser and thermal spraying in one production step. The laser preparation is based on a photomechanical reaction induced by the interaction between a laser of high instantaneous power and a polluted surface. The mechanism of bonding and the coating-substrate interface are then changed in comparison with grit blasting resulting in a significantly reduced substrate roughness. This study is aimed at finding the optimal Protal process parameters for the coating adhesion of a Ni5%Al sprayed on Ti6Al4V and IN718 alloys. The parameters investigated are laser beam intensity, the time delay between the laser impact and the spray impact, powder feed rate, substrate roughness and temperature. A test plan including these parameters is analysed by means of a fractional factorial design of experiment method. The adhesions of the coatings are measured using the ASTM C633 standard test. Data are analysed by a multiple linear regression model using a least squares fit. In addition, the coating/substrate interface is examined by optical and electron scanning microscopy (SEM) techniques as well as by Auger electron spectroscopy. Substrate roughness, substrate temperature and laser intensity are all shown to have a negative correlation with adhesion strength within the investigated range. Areas of diffusion are noticed at the coating/substrate interface.
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