The Experts below are selected from a list of 16707 Experts worldwide ranked by ideXlab platform
B Holper - One of the best experts on this subject based on the ideXlab platform.
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near threshold fatigue crack growth at positive load ratio in aluminium alloys at low and ultrasonic frequency influences of strain rate slip behaviour and air humidity
International Journal of Fatigue, 2004Co-Authors: B Holper, H Mayer, A K Vasudevan, S E StanzltscheggAbstract:Abstract Fatigue crack growth near threshold has been studied in 2024-T3 and in over-aged 7075 (7075-OA) using servo-Hydraulic Equipment (cycling frequency 20 Hz) and ultrasonic Equipment (20 kHz). Experiments have been performed at load ratio R =0.05 and R =0.5 in ambient air and in vacuum. Below 10 −9 m/cycle, fatigue crack growth in vacuum is not influenced by the cycling frequency and no strain rate effects are found. Air humidity accelerates near threshold fatigue crack growth, and threshold stress intensities at 10 −10 m/cycle in ambient air are approximately 50–60% of those measured in vacuum. Similar threshold stress intensities at 20 Hz and 20 kHz, however, higher crack growth rates at the lower frequency at stress intensities above threshold were found in ambient air, where the frequency influence was most pronounced for fully reversed loading. Near threshold 2024-T3 shows planar slip behaviour and crystallographic (stage I-like) fatigue crack growth in vacuum, whereas stage II fatigue crack growth is found in ambient air. 7075-OA shows homogeneous slip properties and stage II fatigue crack growth in both environments. No apparent influences of load ratio and cycling frequency on fracture surfaces produced at very low growth rates are visible.
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near threshold fatigue crack growth in aluminium alloys at low and ultrasonic frequency influences of specimen thickness strain rate slip behaviour and air humidity
International Journal of Fatigue, 2003Co-Authors: B HolperAbstract:Abstract Near threshold fatigue crack growth in ambient air and in vacuum has been studied with ultrasonic fatigue testing Equipment (cycling frequency 20 kHz) and with servo-Hydraulic Equipment (20 Hz). Aluminium alloy 2024-T3 and 7075, heat treated to promote planar slip (7075-UA) and homogeneous slip (7075-OA), respectively, have been tested at load ratio R=-1. In vacuum, no strain rate influences were found and similar crack growth rates were observed at both frequencies. Specimen thickness does not influence the threshold stress intensity amplitude (Kmax,th) determined at 3.5×10–13 m/cycle in vacuum whereas crack growth resistance increases with decreasing specimen thickness at higher growth rates. Kmax,th determined at 10-10 m/cycle in ambient air are similar at 20 Hz and 20 kHz and are 45–55% of those measured in vacuum. In ambient air and at higher stress intensities, fatigue cracks may propagate by a factor of 5–50 faster at the lower frequency. In vacuum, 7075-UA shows better crack growth properties than 7075-OA, more pronounced at higher growth rates. In ambient air, the planar slip materials show a plateau like regime in the (Δa/ΔN vs Kmax)-curves, where growth rates are hardly affected by the stress intensity.
S E Stanzltschegg - One of the best experts on this subject based on the ideXlab platform.
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near threshold fatigue crack growth at positive load ratio in aluminium alloys at low and ultrasonic frequency influences of strain rate slip behaviour and air humidity
International Journal of Fatigue, 2004Co-Authors: B Holper, H Mayer, A K Vasudevan, S E StanzltscheggAbstract:Abstract Fatigue crack growth near threshold has been studied in 2024-T3 and in over-aged 7075 (7075-OA) using servo-Hydraulic Equipment (cycling frequency 20 Hz) and ultrasonic Equipment (20 kHz). Experiments have been performed at load ratio R =0.05 and R =0.5 in ambient air and in vacuum. Below 10 −9 m/cycle, fatigue crack growth in vacuum is not influenced by the cycling frequency and no strain rate effects are found. Air humidity accelerates near threshold fatigue crack growth, and threshold stress intensities at 10 −10 m/cycle in ambient air are approximately 50–60% of those measured in vacuum. Similar threshold stress intensities at 20 Hz and 20 kHz, however, higher crack growth rates at the lower frequency at stress intensities above threshold were found in ambient air, where the frequency influence was most pronounced for fully reversed loading. Near threshold 2024-T3 shows planar slip behaviour and crystallographic (stage I-like) fatigue crack growth in vacuum, whereas stage II fatigue crack growth is found in ambient air. 7075-OA shows homogeneous slip properties and stage II fatigue crack growth in both environments. No apparent influences of load ratio and cycling frequency on fracture surfaces produced at very low growth rates are visible.
H Mayer - One of the best experts on this subject based on the ideXlab platform.
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near threshold fatigue crack growth at positive load ratio in aluminium alloys at low and ultrasonic frequency influences of strain rate slip behaviour and air humidity
International Journal of Fatigue, 2004Co-Authors: B Holper, H Mayer, A K Vasudevan, S E StanzltscheggAbstract:Abstract Fatigue crack growth near threshold has been studied in 2024-T3 and in over-aged 7075 (7075-OA) using servo-Hydraulic Equipment (cycling frequency 20 Hz) and ultrasonic Equipment (20 kHz). Experiments have been performed at load ratio R =0.05 and R =0.5 in ambient air and in vacuum. Below 10 −9 m/cycle, fatigue crack growth in vacuum is not influenced by the cycling frequency and no strain rate effects are found. Air humidity accelerates near threshold fatigue crack growth, and threshold stress intensities at 10 −10 m/cycle in ambient air are approximately 50–60% of those measured in vacuum. Similar threshold stress intensities at 20 Hz and 20 kHz, however, higher crack growth rates at the lower frequency at stress intensities above threshold were found in ambient air, where the frequency influence was most pronounced for fully reversed loading. Near threshold 2024-T3 shows planar slip behaviour and crystallographic (stage I-like) fatigue crack growth in vacuum, whereas stage II fatigue crack growth is found in ambient air. 7075-OA shows homogeneous slip properties and stage II fatigue crack growth in both environments. No apparent influences of load ratio and cycling frequency on fracture surfaces produced at very low growth rates are visible.
A K Vasudevan - One of the best experts on this subject based on the ideXlab platform.
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near threshold fatigue crack growth at positive load ratio in aluminium alloys at low and ultrasonic frequency influences of strain rate slip behaviour and air humidity
International Journal of Fatigue, 2004Co-Authors: B Holper, H Mayer, A K Vasudevan, S E StanzltscheggAbstract:Abstract Fatigue crack growth near threshold has been studied in 2024-T3 and in over-aged 7075 (7075-OA) using servo-Hydraulic Equipment (cycling frequency 20 Hz) and ultrasonic Equipment (20 kHz). Experiments have been performed at load ratio R =0.05 and R =0.5 in ambient air and in vacuum. Below 10 −9 m/cycle, fatigue crack growth in vacuum is not influenced by the cycling frequency and no strain rate effects are found. Air humidity accelerates near threshold fatigue crack growth, and threshold stress intensities at 10 −10 m/cycle in ambient air are approximately 50–60% of those measured in vacuum. Similar threshold stress intensities at 20 Hz and 20 kHz, however, higher crack growth rates at the lower frequency at stress intensities above threshold were found in ambient air, where the frequency influence was most pronounced for fully reversed loading. Near threshold 2024-T3 shows planar slip behaviour and crystallographic (stage I-like) fatigue crack growth in vacuum, whereas stage II fatigue crack growth is found in ambient air. 7075-OA shows homogeneous slip properties and stage II fatigue crack growth in both environments. No apparent influences of load ratio and cycling frequency on fracture surfaces produced at very low growth rates are visible.
Yudoko G. - One of the best experts on this subject based on the ideXlab platform.
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Review of Hydraulic Equipment Maintance Strategy to Reduce Oil Consumption Cost in Hot Strip Mill PT KS
Bandung Institute of Technology, 2013Co-Authors: Suwarto A., Yudoko G.Abstract:Currently, every company should do efficiency to reduce the production cost in order to increase it product competitiveness in both local and International market. Maintenance activity cost is the one of management concern to reduce without sacrificing the reliability of Equipment and machine performance. The average lubricant USAge cost in Hot Strip Mill PT. KS is Rp 1.149.464.558,- per-month or total Rp 13.793.574.699,- for year 2011, and this is a serious problem because it tends to increase every year. There are many kinds of lubricants (oil and grease) which are used in Hot Strip Mill PT. Krakatau Steel as bearing lubrication system, gear lubrication system and as fluid media in Hydraulic system to move the Equipment with heavy load. To reduce the lubricant cost is by doing identification of Hydraulic Equipment which is using the biggest of oil consumption cost for Rp 3.287.476.000,- per-year. Because there are some Hydraulic system in Hot Strip Mill, therefore the research is focusing on Hydraulic system in Finishing Mill area which is the biggest contributor on oil consumption by 825.691.647,- per-year.The main cause of high oil consumption cost is leakage on Hydraulic hose and Hydraulic cylinder seal because there is no periodically replacement schedule. Therefore, it is suggested to implement the maintenance strategy both for preventive and predictive maintenance strategy based on Equipment criticality factor or impact will occur when Equipment failure such as: workforce safety, production downtime, product quality, Equipment duty of operation and the inspection possibilities during Equipment running. By implementing an appropriate maintenance strategy, the company will get cost saving Rp 87.838.138,- per-year or 10,6 % from oil consumption cost
