The Experts below are selected from a list of 1245 Experts worldwide ranked by ideXlab platform
Johannes Henrich Schleifenbaum - One of the best experts on this subject based on the ideXlab platform.
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Laser additive manufacturing of Zn porous scaffolds: Shielding Gas Flow, surface quality and densification
Journal of Materials Science and Technology, 2019Co-Authors: Peng Wen, Maximilian Voshage, Lucas Jauer, Yanzhe Chen, Reinhart Poprawe, Yu Qin, Johannes Henrich SchleifenbaumAbstract:Zn based metals have exhibited promising prospects as a structural material for biodegradable applications. Pure Zn porous scaffolds were produced by laser powder bed fusion (LPBF) based on data files of designing and CT scanning. Massive Zn evaporation during laser melting largely influenced the formation quality during LPBF of Zn metal. The metal vapor in processing chamber was blown off and suctioned out efficiently by an optimized Gas circulation system. Numerical analysis was used to design and testify the performance of Gas Flow. The surface of scaffolds was covered with numerous particles in different sizes. Processing pores occurred near the outline contour of struts. The average grain size in width was 8.5 μm, and the hardness was 43.8 HV. Chemical plus electrochemical polishing obtained uniform and smooth surface without processing pores, but the diameter of struts reduced to 250 μm from the design value 300 μm. The poor surface quality and processing pores were resulted by the splashing particles included spatters and powders due to the recoil force of evaporation, and the horizontal movement of liquid metal due to overheating and wetting. The insufficient melting at the outline contour combined with good wetting of Zn liquid metal further increased the surface roughness and processing pores.
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Laser additive manufacturing of Zn metal parts for biodegradable implants: Effect of Gas Flow on evaporation and formation quality
Journal of Laser Applications, 2019Co-Authors: Yanzhe Chen, Maximilian Voshage, Lucas Jauer, Johannes Henrich Schleifenbaum, Peng Wen, Yu Qin, Reinhart PopraweAbstract:Zn based metals have exhibited promising applications for biodegradable medical implants. Although additive manufacturing has been widely investigated for many medical metals, only a handful of very recent reports can be found on laser powder bed fusion (L-PBF) of pure Zn cubes. Severe evaporation occurred during laser melting of Zn powders due to the low boiling point of Zn metal. The formation quality was either not satisfactory or the obtained processing window was too narrow. In this paper, a specially designed Gas Flow system was used in order to eliminate the negative effect of Zn metal evaporation on the processing of L-PBF. Numerical analysis was used to simulate the velocity distribution of Shielding Gas Flow and the interaction between the Gas Flow and the evaporation fume based on computation fluid dynamics with considering different Shielding Flow designs and laser energy inputs. Pure Zn metal parts were obtained with density over 99.90% after the optimization of Shielding Gas Flow and laser energy input. The areal surface roughness (Sa) of L-PBF parts was about 10 μm at side surfaces for as-melted status, and reduced to 4.83 μm after sandblasting. The effects of Gas Flow and laser energy input on evaporation and formation quality were discussed. An effective method was provided to deal with metal evaporation during L-PBF processing, which was not only beneficial to additive manufacturing of Zn based metals, but also to other active metals with high evaporation tendency like Mg and Al alloys.Zn based metals have exhibited promising applications for biodegradable medical implants. Although additive manufacturing has been widely investigated for many medical metals, only a handful of very recent reports can be found on laser powder bed fusion (L-PBF) of pure Zn cubes. Severe evaporation occurred during laser melting of Zn powders due to the low boiling point of Zn metal. The formation quality was either not satisfactory or the obtained processing window was too narrow. In this paper, a specially designed Gas Flow system was used in order to eliminate the negative effect of Zn metal evaporation on the processing of L-PBF. Numerical analysis was used to simulate the velocity distribution of Shielding Gas Flow and the interaction between the Gas Flow and the evaporation fume based on computation fluid dynamics with considering different Shielding Flow designs and laser energy inputs. Pure Zn metal parts were obtained with density over 99.90% after the optimization of Shielding Gas Flow and laser e...
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Visualization of the Shielding Gas Flow in SLM machines by space-resolved thermal anemometry
Rapid Prototyping Journal, 2018Co-Authors: Maximilian Schniedenharn, Frederik Wiedemann, Johannes Henrich SchleifenbaumAbstract:Purpose The purpose of this paper is to introduce an approach in measuring the Shielding Gas Flow within laser powder bed fusion (L-PBF) machines under near-process conditions (regarding oxygen content and Shielding Gas Flow). Design/methodology/approach The measurements are made sequentially using a hot-wire anemometer. After a short introduction into the measurement technique, the system which places the measurement probe within the machine is described. Finally, the measured Shielding Gas Flow of a commercial L-PBF machine is presented. Findings An approach to measure the Shielding Gas Flow within SLM machines has been developed and successfully tested. The use of a thermal anemometer along with an automated probe-placement system enables the space-resolved measurement of the Flow speed and its turbulence. Research limitations/implications The used single-normal (SN) hot-wire anemometer does not provide the Flow vectors’ orientation. Using a probe with two or three hot-films and an improved placement system will provide more information about the Flow and less disturbance to it. Originality/value A measurement system which allows the measurement of the Shielding Gas Flow within commercial L-PBF machines is presented. This enables the correlation of the Shielding Gas Flow with the resulting parts’ quality.
M Aghaiekhafri - One of the best experts on this subject based on the ideXlab platform.
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optimization of Gas tungsten arc welding process by response surface methodology
Materials & Design, 2014Co-Authors: N Kiaee, M AghaiekhafriAbstract:Abstract Gas tungsten arc welding is widely used for connecting of boiler parts made of A516-Gr70 carbon steel. In this study important process parameters namely current, welding speed and Shielding Gas Flow rate were optimized using response surface methodology (RSM). The simultaneous effects of these parameters on tensile strength and hardness were also evaluated. Applying RSM, simultaneous effects of welding parameters on tensile strength and hardness were obtained through two separate equations. Moreover, optimized values of welding process parameters to achieve desired mechanical properties were evaluated. Desired tensile strength and hardness were achieved at optimum current of 130 A, welding speed of 9.4 cm/min and Gas Flow rate of 15.1 l/min.
Norman Mcpherson - One of the best experts on this subject based on the ideXlab platform.
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Visualisation of alternating Shielding Gas Flow in GTAW
Materials & Design, 2016Co-Authors: Ioannis Bitharas, Norman Mcpherson, Stuart Campbell, Alexander Galloway, Andrew MooreAbstract:Abstract The alternating Shielding Gas technique is a method of achieving transient arc characteristics during arc welding; however the complex Flow that occurs through its use has not been investigated previously. A schlieren system was used to image density gradients that arise when alternating argon and helium shield Gases, under varying Flow parameters, with Gas tungsten arc welding (GTAW). A theoretical analysis was carried out to determine the conditions under which the technique facilitates arc pulsing, in particular to avoid mixing of the shield Gases in the delivery pipe prior to the welding nozzle. At appropriate pulsing frequency and Flow rates, a stable horizontal region of helium was observed in the weld region, maintained in position by the denser argon from the preceding pulse. This higher than average mass fraction of helium when applying the Shielding Gases alternately, compared to a premixed Gas with the same volume of argon and helium, increased the weld penetration by 13% on average, suggesting a modest improvement in heat transfer.
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effect of Shielding Gas parameters on weld metal thermal properties in Gas metal arc welding
The International Journal of Advanced Manufacturing Technology, 2015Co-Authors: F H Ley, Alexander Galloway, Stuart Campbell, Norman McphersonAbstract:This study considered the effect of Shielding Gas parameters (composition, supply method and Flow rate) on the post-weld thermal properties (thermal expansion, specific heat capacity, thermal diffusivity and thermal conductivity) of the weld metal in Gas metal arc welding. This is of importance as the thermal properties influence the temperature distribution and therefore the residual stresses and distortion present within the final structure. Due to the lack of accurate thermal data, computational modelling techniques (such as FEA and CFD) used for modelling the welding process generally make assumptions regarding the material thermal properties, and it is often the case that the parent material thermal properties are extended to the weld metal, introducing errors to the simulation. It was determined that the weld metal posses considerably different thermal properties to the DH36 grade steel parent material and that the Shielding Gas parameters significantly alter key thermal properties of the solidified weld metal. A lower Shielding Gas Flow rate exhibited beneficial properties including a lower thermal expansion and higher specific heat capacity and thermal conductivity than a higher Shielding Gas Flow rate.
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Artificial neural network optimisation of Shielding Gas Flow rate in Gas metal arc welding subjected to cross drafts when using alternating Shielding Gases
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2014Co-Authors: Stuart Campbell, Alexander Galloway, F H Ley, Norman McphersonAbstract:This study implemented an iterative experimental approach in order to determine the Shielding Gas Flow required to produce high quality welds in the Gas metal arc welding (GMAW) process with alternating Shielding Gases when subjected to varying velocities of cross drafts. Thus determining the transitional zone where the weld quality deteriorates as a function of cross draft velocity. An Artificial Neural Network (ANN) was developed using the experimental data that would predict the weld quality based primarily on Shielding Gas composition, alternating frequency and Flowrate, and cross draft velocity, but also incorporated other important input parameters including voltage and current. A series of weld trials were conducted validate and test the robustness of the model generated. It was found that the alternating Shielding Gas process does not provide the same level of resistance to the adverse effects of cross drafts as a conventional argon/carbon dioxide mixture. The use of such a prediction tool is of benefit to industry in that it allows the adoption of a more efficient Shielding Gas Flow rate, whilst removing the uncertainty of the resultant weld quality.
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PRICM: 8 Pacific Rim International Congress on Advanced Materials and Processing - GMAW Shielding Gas Flow optimisation by refinement of nozzle geometry
Proceedings of the 8th Pacific Rim International Congress on Advanced Materials and Processing, 2013Co-Authors: Stuart Campbell, Alexander Galloway, Norman McphersonAbstract:With an ongoing demand to improve the efficiency of the Gas metal arc welding process, steps are being taken to reduce the Shielding Gas consumption. However, sufficient Shielding Gas coverage of the weld region is essential for the generation of high quality welds, and drafts can be detrimental to its efficiency. In industry, the general practise to ensure coverage is to increase the Shielding Gas Flow rate, however, too high a Flow rate can induce undesirable turbulence in the Shielding Gas column, whilst adding unnecessary cost to the process. A simplified computational fluid dynamics model has been generated, and validated through extensive experimental trials, to accurately model the Shielding Gas Flow when subjected to the adverse effects of cross drafts. Several nozzle geometry changes have been investigated with the aim of improving the Shielding Gas column’s resistance to drafts, eliminating the requirement to increase the Shielding Gas Flow rate.
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gmaw Shielding Gas Flow optimisation by refinement of nozzle geometry
PRICM: 8 Pacific Rim International Congress on Advanced Materials and Processing, 2013Co-Authors: Stuart Campbell, Alexander Galloway, Norman McphersonAbstract:With an ongoing demand to improve the efficiency of the Gas metal arc welding process, steps are being taken to reduce the Shielding Gas consumption. However, sufficient Shielding Gas coverage of the weld region is essential for the generation of high quality welds, and drafts can be detrimental to its efficiency. In industry, the general practise to ensure coverage is to increase the Shielding Gas Flow rate, however, too high a Flow rate can induce undesirable turbulence in the Shielding Gas column, whilst adding unnecessary cost to the process. A simplified computational fluid dynamics model has been generated, and validated through extensive experimental trials, to accurately model the Shielding Gas Flow when subjected to the adverse effects of cross drafts. Several nozzle geometry changes have been investigated with the aim of improving the Shielding Gas column’s resistance to drafts, eliminating the requirement to increase the Shielding Gas Flow rate.
Peng Wen - One of the best experts on this subject based on the ideXlab platform.
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Laser additive manufacturing of Zn porous scaffolds: Shielding Gas Flow, surface quality and densification
Journal of Materials Science and Technology, 2019Co-Authors: Peng Wen, Maximilian Voshage, Lucas Jauer, Yanzhe Chen, Reinhart Poprawe, Yu Qin, Johannes Henrich SchleifenbaumAbstract:Zn based metals have exhibited promising prospects as a structural material for biodegradable applications. Pure Zn porous scaffolds were produced by laser powder bed fusion (LPBF) based on data files of designing and CT scanning. Massive Zn evaporation during laser melting largely influenced the formation quality during LPBF of Zn metal. The metal vapor in processing chamber was blown off and suctioned out efficiently by an optimized Gas circulation system. Numerical analysis was used to design and testify the performance of Gas Flow. The surface of scaffolds was covered with numerous particles in different sizes. Processing pores occurred near the outline contour of struts. The average grain size in width was 8.5 μm, and the hardness was 43.8 HV. Chemical plus electrochemical polishing obtained uniform and smooth surface without processing pores, but the diameter of struts reduced to 250 μm from the design value 300 μm. The poor surface quality and processing pores were resulted by the splashing particles included spatters and powders due to the recoil force of evaporation, and the horizontal movement of liquid metal due to overheating and wetting. The insufficient melting at the outline contour combined with good wetting of Zn liquid metal further increased the surface roughness and processing pores.
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Laser additive manufacturing of Zn metal parts for biodegradable implants: Effect of Gas Flow on evaporation and formation quality
Journal of Laser Applications, 2019Co-Authors: Yanzhe Chen, Maximilian Voshage, Lucas Jauer, Johannes Henrich Schleifenbaum, Peng Wen, Yu Qin, Reinhart PopraweAbstract:Zn based metals have exhibited promising applications for biodegradable medical implants. Although additive manufacturing has been widely investigated for many medical metals, only a handful of very recent reports can be found on laser powder bed fusion (L-PBF) of pure Zn cubes. Severe evaporation occurred during laser melting of Zn powders due to the low boiling point of Zn metal. The formation quality was either not satisfactory or the obtained processing window was too narrow. In this paper, a specially designed Gas Flow system was used in order to eliminate the negative effect of Zn metal evaporation on the processing of L-PBF. Numerical analysis was used to simulate the velocity distribution of Shielding Gas Flow and the interaction between the Gas Flow and the evaporation fume based on computation fluid dynamics with considering different Shielding Flow designs and laser energy inputs. Pure Zn metal parts were obtained with density over 99.90% after the optimization of Shielding Gas Flow and laser energy input. The areal surface roughness (Sa) of L-PBF parts was about 10 μm at side surfaces for as-melted status, and reduced to 4.83 μm after sandblasting. The effects of Gas Flow and laser energy input on evaporation and formation quality were discussed. An effective method was provided to deal with metal evaporation during L-PBF processing, which was not only beneficial to additive manufacturing of Zn based metals, but also to other active metals with high evaporation tendency like Mg and Al alloys.Zn based metals have exhibited promising applications for biodegradable medical implants. Although additive manufacturing has been widely investigated for many medical metals, only a handful of very recent reports can be found on laser powder bed fusion (L-PBF) of pure Zn cubes. Severe evaporation occurred during laser melting of Zn powders due to the low boiling point of Zn metal. The formation quality was either not satisfactory or the obtained processing window was too narrow. In this paper, a specially designed Gas Flow system was used in order to eliminate the negative effect of Zn metal evaporation on the processing of L-PBF. Numerical analysis was used to simulate the velocity distribution of Shielding Gas Flow and the interaction between the Gas Flow and the evaporation fume based on computation fluid dynamics with considering different Shielding Flow designs and laser energy inputs. Pure Zn metal parts were obtained with density over 99.90% after the optimization of Shielding Gas Flow and laser e...
Reinhart Poprawe - One of the best experts on this subject based on the ideXlab platform.
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Laser additive manufacturing of Zn porous scaffolds: Shielding Gas Flow, surface quality and densification
Journal of Materials Science and Technology, 2019Co-Authors: Peng Wen, Maximilian Voshage, Lucas Jauer, Yanzhe Chen, Reinhart Poprawe, Yu Qin, Johannes Henrich SchleifenbaumAbstract:Zn based metals have exhibited promising prospects as a structural material for biodegradable applications. Pure Zn porous scaffolds were produced by laser powder bed fusion (LPBF) based on data files of designing and CT scanning. Massive Zn evaporation during laser melting largely influenced the formation quality during LPBF of Zn metal. The metal vapor in processing chamber was blown off and suctioned out efficiently by an optimized Gas circulation system. Numerical analysis was used to design and testify the performance of Gas Flow. The surface of scaffolds was covered with numerous particles in different sizes. Processing pores occurred near the outline contour of struts. The average grain size in width was 8.5 μm, and the hardness was 43.8 HV. Chemical plus electrochemical polishing obtained uniform and smooth surface without processing pores, but the diameter of struts reduced to 250 μm from the design value 300 μm. The poor surface quality and processing pores were resulted by the splashing particles included spatters and powders due to the recoil force of evaporation, and the horizontal movement of liquid metal due to overheating and wetting. The insufficient melting at the outline contour combined with good wetting of Zn liquid metal further increased the surface roughness and processing pores.
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Laser additive manufacturing of Zn metal parts for biodegradable implants: Effect of Gas Flow on evaporation and formation quality
Journal of Laser Applications, 2019Co-Authors: Yanzhe Chen, Maximilian Voshage, Lucas Jauer, Johannes Henrich Schleifenbaum, Peng Wen, Yu Qin, Reinhart PopraweAbstract:Zn based metals have exhibited promising applications for biodegradable medical implants. Although additive manufacturing has been widely investigated for many medical metals, only a handful of very recent reports can be found on laser powder bed fusion (L-PBF) of pure Zn cubes. Severe evaporation occurred during laser melting of Zn powders due to the low boiling point of Zn metal. The formation quality was either not satisfactory or the obtained processing window was too narrow. In this paper, a specially designed Gas Flow system was used in order to eliminate the negative effect of Zn metal evaporation on the processing of L-PBF. Numerical analysis was used to simulate the velocity distribution of Shielding Gas Flow and the interaction between the Gas Flow and the evaporation fume based on computation fluid dynamics with considering different Shielding Flow designs and laser energy inputs. Pure Zn metal parts were obtained with density over 99.90% after the optimization of Shielding Gas Flow and laser energy input. The areal surface roughness (Sa) of L-PBF parts was about 10 μm at side surfaces for as-melted status, and reduced to 4.83 μm after sandblasting. The effects of Gas Flow and laser energy input on evaporation and formation quality were discussed. An effective method was provided to deal with metal evaporation during L-PBF processing, which was not only beneficial to additive manufacturing of Zn based metals, but also to other active metals with high evaporation tendency like Mg and Al alloys.Zn based metals have exhibited promising applications for biodegradable medical implants. Although additive manufacturing has been widely investigated for many medical metals, only a handful of very recent reports can be found on laser powder bed fusion (L-PBF) of pure Zn cubes. Severe evaporation occurred during laser melting of Zn powders due to the low boiling point of Zn metal. The formation quality was either not satisfactory or the obtained processing window was too narrow. In this paper, a specially designed Gas Flow system was used in order to eliminate the negative effect of Zn metal evaporation on the processing of L-PBF. Numerical analysis was used to simulate the velocity distribution of Shielding Gas Flow and the interaction between the Gas Flow and the evaporation fume based on computation fluid dynamics with considering different Shielding Flow designs and laser energy inputs. Pure Zn metal parts were obtained with density over 99.90% after the optimization of Shielding Gas Flow and laser e...