The Experts below are selected from a list of 9462 Experts worldwide ranked by ideXlab platform
Andreas Tunnermann - One of the best experts on this subject based on the ideXlab platform.
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analysis of the hole shape evolution in fs pulse percussion Drilling with bursts
Proceedings of SPIE, 2016Co-Authors: Helena Kammer, Andreas Tunnermann, Stefan Nolte, Felix DreisowAbstract:We analyze the use of bursts of ultra-short pulses in order to improve Drilling Efficiency and quality. Silicon is used as a non-transparent model material, in which the behavior of laser percussion Drilling with 1030 nm bursts consisting of 200 fs pulses separated by a time delay between 1 ps and 4 ns was investigated. The deep Drilling process is directly imaged perpendicular to the Drilling direction using a CCD camera and an illumination beam at 1064 nm, where the silicon sample is transparent. The results are compared to Drilling without bursts for different pulse energies. The Efficiency of the Drilling process, hole quality, as well as reproducibility of the hole shape are analyzed. Pulse separation times within the burst from 1 ps to 8 ps result in deeper holes with a larger silhouette area, however equal or reduced hole quality and reproducibility compared to Drilling with individual pulses. In contrast with pulse separation times from 510 ps to 4 ns a quality and reproducibility improvement is visible. For these delay times the achieved depth was equal or higher compared to micromachining without bursts.
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ultrashort pulse laser Drilling of metals using a high repetition rate high average power fiber cpa system
Proceedings of SPIE the International Society for Optical Engineering, 2009Co-Authors: Antonio Ancona, Stefan Nolte, Cesar Jauregui, Sven Doring, F Roser, Jens Limpert, Andreas TunnermannAbstract:We present an experimental study of the Drilling of metal targets with ultrashort laser pulses with pulse durations from 800 fs to 19 ps at repetition rates up to 1 MHz, average powers up to 70 Watts, using an Ytterbium-doped fiber CPA system. Particle shielding and heat accumulation have been found to influence the Drilling Efficiency at high repetition rates. Particle shielding causes an increase in the number of pulses for breakthrough. It occurs at a few hundred kHz, depending on the pulse energy and duration. The heat accumulation effect is noticed at higher repetition rates. Although it overbalances the particle shielding thus making the Drilling process faster, heat accumulation is responsible for the formation of a large amount of molten material that limits the hole quality. The variations of the pulse duration reveal that heat accumulation starts at higher repetition rates for shorter pulse lengths. This is in agreement with the observed higher ablation Efficiency with shorter pulse duration. Thus, the shorter pulses might be advantageous if highest precision and processing speed is required.
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high speed laser Drilling of metals using a high repetition rate high average power ultrafast fiber cpa system
Optics Express, 2008Co-Authors: Antonio Ancona, Stefan Nolte, F Roser, Jens Limpert, K Rademaker, Andreas TunnermannAbstract:We present an experimental study on the Drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the Drilling Efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation Efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investigated processing parameters. Therefore, the full power of the fiber CPA system can be exploited, which allows to trepan high-quality holes in 0.5mm-thick copper samples with breakthrough times as low as 75 ms.
Stefan Nolte - One of the best experts on this subject based on the ideXlab platform.
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analysis of the hole shape evolution in fs pulse percussion Drilling with bursts
Proceedings of SPIE, 2016Co-Authors: Helena Kammer, Andreas Tunnermann, Stefan Nolte, Felix DreisowAbstract:We analyze the use of bursts of ultra-short pulses in order to improve Drilling Efficiency and quality. Silicon is used as a non-transparent model material, in which the behavior of laser percussion Drilling with 1030 nm bursts consisting of 200 fs pulses separated by a time delay between 1 ps and 4 ns was investigated. The deep Drilling process is directly imaged perpendicular to the Drilling direction using a CCD camera and an illumination beam at 1064 nm, where the silicon sample is transparent. The results are compared to Drilling without bursts for different pulse energies. The Efficiency of the Drilling process, hole quality, as well as reproducibility of the hole shape are analyzed. Pulse separation times within the burst from 1 ps to 8 ps result in deeper holes with a larger silhouette area, however equal or reduced hole quality and reproducibility compared to Drilling with individual pulses. In contrast with pulse separation times from 510 ps to 4 ns a quality and reproducibility improvement is visible. For these delay times the achieved depth was equal or higher compared to micromachining without bursts.
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ultrashort pulse laser Drilling of metals using a high repetition rate high average power fiber cpa system
Proceedings of SPIE the International Society for Optical Engineering, 2009Co-Authors: Antonio Ancona, Stefan Nolte, Cesar Jauregui, Sven Doring, F Roser, Jens Limpert, Andreas TunnermannAbstract:We present an experimental study of the Drilling of metal targets with ultrashort laser pulses with pulse durations from 800 fs to 19 ps at repetition rates up to 1 MHz, average powers up to 70 Watts, using an Ytterbium-doped fiber CPA system. Particle shielding and heat accumulation have been found to influence the Drilling Efficiency at high repetition rates. Particle shielding causes an increase in the number of pulses for breakthrough. It occurs at a few hundred kHz, depending on the pulse energy and duration. The heat accumulation effect is noticed at higher repetition rates. Although it overbalances the particle shielding thus making the Drilling process faster, heat accumulation is responsible for the formation of a large amount of molten material that limits the hole quality. The variations of the pulse duration reveal that heat accumulation starts at higher repetition rates for shorter pulse lengths. This is in agreement with the observed higher ablation Efficiency with shorter pulse duration. Thus, the shorter pulses might be advantageous if highest precision and processing speed is required.
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high speed laser Drilling of metals using a high repetition rate high average power ultrafast fiber cpa system
Optics Express, 2008Co-Authors: Antonio Ancona, Stefan Nolte, F Roser, Jens Limpert, K Rademaker, Andreas TunnermannAbstract:We present an experimental study on the Drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the Drilling Efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation Efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investigated processing parameters. Therefore, the full power of the fiber CPA system can be exploited, which allows to trepan high-quality holes in 0.5mm-thick copper samples with breakthrough times as low as 75 ms.
Antonio Ancona - One of the best experts on this subject based on the ideXlab platform.
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ultrashort pulse laser Drilling of metals using a high repetition rate high average power fiber cpa system
Proceedings of SPIE the International Society for Optical Engineering, 2009Co-Authors: Antonio Ancona, Stefan Nolte, Cesar Jauregui, Sven Doring, F Roser, Jens Limpert, Andreas TunnermannAbstract:We present an experimental study of the Drilling of metal targets with ultrashort laser pulses with pulse durations from 800 fs to 19 ps at repetition rates up to 1 MHz, average powers up to 70 Watts, using an Ytterbium-doped fiber CPA system. Particle shielding and heat accumulation have been found to influence the Drilling Efficiency at high repetition rates. Particle shielding causes an increase in the number of pulses for breakthrough. It occurs at a few hundred kHz, depending on the pulse energy and duration. The heat accumulation effect is noticed at higher repetition rates. Although it overbalances the particle shielding thus making the Drilling process faster, heat accumulation is responsible for the formation of a large amount of molten material that limits the hole quality. The variations of the pulse duration reveal that heat accumulation starts at higher repetition rates for shorter pulse lengths. This is in agreement with the observed higher ablation Efficiency with shorter pulse duration. Thus, the shorter pulses might be advantageous if highest precision and processing speed is required.
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high speed laser Drilling of metals using a high repetition rate high average power ultrafast fiber cpa system
Optics Express, 2008Co-Authors: Antonio Ancona, Stefan Nolte, F Roser, Jens Limpert, K Rademaker, Andreas TunnermannAbstract:We present an experimental study on the Drilling of metal targets with ultrashort laser pulses at high repetition rates (from 50 kHz up to 975 kHz) and high average powers (up to 68 Watts), using an ytterbium-doped fiber CPA system. The number of pulses to drill through steel and copper sheets with thicknesses up to 1 mm have been measured as a function of the repetition rate and the pulse energy. Two distinctive effects, influencing the Drilling Efficiency at high repetition rates, have been experimentally found and studied: particle shielding and heat accumulation. While the shielding of subsequent pulses due to the ejected particles leads to a reduced ablation Efficiency, this effect is counteracted by heat accumulation. The experimental data are in good qualitative agreement with simulations of the heat accumulation effect and previous studies on the particle emission. However, for materials with a high thermal conductivity as copper, both effects are negligible for the investigated processing parameters. Therefore, the full power of the fiber CPA system can be exploited, which allows to trepan high-quality holes in 0.5mm-thick copper samples with breakthrough times as low as 75 ms.
Xuyue Chen - One of the best experts on this subject based on the ideXlab platform.
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real time optimization of Drilling parameters based on mechanical specific energy for rotating Drilling with positive displacement motor in the hard formation
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Xuyue Chen, Deli Gao, Boyun Guo, Yongcun FengAbstract:Abstract Mechanical specific energy (MSE) has been widely used to quantify Drilling Efficiency and maximize rate of penetration (ROP) in oil and gas wells Drilling. Given currently there are few effective MSE models to precisely model the actual downhole Drilling for rotating Drilling with positive displacement motor (PDM), in this work a new MSE model for rotating Drilling with PDM is established based on the analysis of PDM performance. Meanwhile a method for real time optimization of Drilling parameters based on MSE for rotating Drilling with PDM in the hard formation is also presented. Field data presented in this paper indicate that when Drilling with a high Efficiency and free of Drilling complications, the MSE(min) estimated by the new MSE model is roughly equal to the confined compressive strength (CCS) of the formation along the well depth, it can meet the needs of applications in the field. It also shows that ROP is sensitive to high weight on bit (WOB) for rotating Drilling with PDM and the optimum WOB is low, increasing WOB does not always increase ROP but is more likely to decrease ROP. The method for optimizing Drilling parameters can real time estimate optimum WOB values with different RPM to drill a specific formation interval with PDM. It can be used to maximize ROP and allow operators to drill longer and avoid unnecessary trips.
U Eppelt - One of the best experts on this subject based on the ideXlab platform.
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analysis of laser drilled deep holes in stainless steel by superposed pulsed nd yag laser radiation
Optics and Lasers in Engineering, 2008Co-Authors: M. Brajdic, K. Walther, U EppeltAbstract:Abstract Deep Drilling of through holes in stainless steel (1.4301, sample thicknesses 5, 8 and 10 mm) has been performed with the superposed radiation of two pulsed Nd:YAG lasers with pulse duration of 0.5 ms superposed by 17 ns pulses. The Drilling Efficiency is improved by the spatially and temporally superposed radiation of the two lasers. The enhanced Drilling speed and the larger reproducibility of the Drilling time are explained by a modified formation of closures in the hole during percussion Drilling which are recorded by high-speed photography. The metallographic hole analysis exhibits high-temperature oxidation marks. The development of these marks is described by a ray tracing of the incident beam within the hole and the resulting intensity distribution at the hole wall.
