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RISS 인기검색어
- 검색키워드
- 저자 : G. N. Wells (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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An experimental-computational investigation of fracture in brittle materials
K. De Proft,G. N. Wells,L. J. Sluys,W. P. De Wilde 한국계산역학회 2004 Computers and Concrete, An International Journal Vol.1 No.3
A combined experimental-computational study of a double edge-notched stone specimen subjected to tensile loading is presented. In the experimental part, the load-deformation response and the displacement field around the crack tip are recorded. An Electronic Speckle Pattern Interferometer (ESPI) is used to obtain the local displacement field. The experimental results are used to validate a numerical model for the description of fracture using finite elements. The numerical model uses displacement discontinuities to model cracks. At the discontinuity, a plasticity-based cohesive zone model is applied for monotonic loading and a combined damage-plasticity cohesive zone model is used for cyclic loading. Both local and global results from the numerical simulations are compared with experimental data. It is shown that local measurements add important information for the validation of the numerical model. Consequently, the numerical models are enhanced in order to correctly capture the experimentally observed behaviour.
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Insights Into Emissions and Exposures From Use of Industrial-Scale Additive Manufacturing Machines
Stefaniak, A.B.,Johnson, A.R.,du Preez, S.,Hammond, D.R.,Wells, J.R.,Ham, J.E.,LeBouf, R.F.,Martin, S.B. Jr.,Duling, M.G.,Bowers, L.N.,Knepp, A.K.,de Beer, D.J.,du Plessis, J.L. Occupational Safety and Health Research Institute 2019 Safety and health at work Vol.10 No.2
Background: Emerging reports suggest the potential for adverse health effects from exposure to emissions from some additive manufacturing (AM) processes. There is a paucity of real-world data on emissions from AM machines in industrial workplaces and personal exposures among AM operators. Methods: Airborne particle and organic chemical emissions and personal exposures were characterized using real-time and time-integrated sampling techniques in four manufacturing facilities using industrial-scale material extrusion and material jetting AM processes. Results: Using a condensation nuclei counter, number-based particle emission rates (ERs) (number/min) from material extrusion AM machines ranged from $4.1{\times}10^{10}$ (Ultem filament) to $2.2{\times}10^{11}$ [acrylonitrile butadiene styrene and polycarbonate filaments). For these same machines, total volatile organic compound ERs (${\mu}g/min$) ranged from $1.9{\times}10^4$ (acrylonitrile butadiene styrene and polycarbonate) to $9.4{\times}10^4$ (Ultem). For the material jetting machines, the number-based particle ER was higher when the lid was open ($2.3{\times}10^{10}number/min$) than when the lid was closed ($1.5-5.5{\times}10^9number/min$); total volatile organic compound ERs were similar regardless of the lid position. Low levels of acetone, benzene, toluene, and m,p-xylene were common to both AM processes. Carbonyl compounds were detected; however, none were specifically attributed to the AM processes. Personal exposures to metals (aluminum and iron) and eight volatile organic compounds were all below National Institute for Occupational Safety and Health (NIOSH)-recommended exposure levels. Conclusion: Industrial-scale AM machines using thermoplastics and resins released particles and organic vapors into workplace air. More research is needed to understand factors influencing real-world industrial-scale AM process emissions and exposures.
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Insights Into Emissions and Exposures From Use of Industrial-Scale Additive Manufacturing Machines
A.B. Stefaniak,A.R. Johnson,S. du Preez,D.R. Hammond,J.R. Wells,J.E. Ham,R.F. LeBouf,S.B. Martin Jr.,M.G. Duling,L.N. Bowers,A.K. Knepp,D.J. de Beer,J.L. du Plessis 한국산업안전보건공단 산업안전보건연구원 2019 Safety and health at work Vol.10 No.2
Background: Emerging reports suggest the potential for adverse health effects from exposure to emissions from some additive manufacturing (AM) processes. There is a paucity of real-world data on emissions from AM machines in industrial workplaces and personal exposures among AM operators. Methods: Airborne particle and organic chemical emissions and personal exposures were characterized using real-time and time-integrated sampling techniques in four manufacturing facilities using industrial-scale material extrusion and material jetting AM processes. Results: Using a condensation nuclei counter, number-based particle emission rates (ERs) (number/min) from material extrusion AM machines ranged from 4.1 1010 (Ultem filament) to 2.2 1011 [acrylonitrile butadiene styrene and polycarbonate filaments). For these same machines, total volatile organic compound ERs (mg/min) ranged from 1.9 104 (acrylonitrile butadiene styrene and polycarbonate) to 9.4 104 (Ultem). For the material jetting machines, the number-based particle ER was higher when the lid was open (2.3 1010 number/min) than when the lid was closed (1.5e5.5 109 number/min); total volatile organic compound ERs were similar regardless of the lid position. Low levels of acetone, benzene, toluene, and m,p-xylene were common to both AM processes. Carbonyl compounds were detected; however, none were specifically attributed to the AM processes. Personal exposures to metals (aluminum and iron) and eight volatile organic compounds were all below National Institute for Occupational Safety and Health (NIOSH)-recommended exposure levels. Conclusion: Industrial-scale AM machines using thermoplastics and resins released particles and organic vapors into workplace air. More research is needed to understand factors influencing real-world industrial- scale AM process emissions and exposures.
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