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  • 1
    Publication Date: 2013-08-31
    Description: Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2513 , NAS 1.60:2513 , E-2578
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  • 2
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The problems and failures occurring with the operation of high speed gears are discussed. The gearing losses associated with high speed gearing such as tooth mesh friction, bearing friction, churning, and windage are discussed with various ways shown to help reduce these losses and thereby improve efficiency. Several different methods of oil jet lubrication for high speed gearing are given such as into mesh, out of mesh, and radial jet lubrication. The experiments and analytical results for the various methods of oil jet lubrication are shown with the strengths and weaknesses of each method discussed. The analytical and experimental results of gear lubrication and cooling at various test conditions are presented. These results show the very definite need of improved methods of gear cooling at high speed and high load conditions.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-87096 , E-2660 , NAS 1.15:87096
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  • 3
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    In:  CASI
    Publication Date: 2013-08-31
    Description: Gearing technology in its modern form has a history of only 100 years. However, the earliest form of gearing can probably be traced back to fourth century B.C. Greece. Current gear practice and recent advances in the technology are drawn together. The history of gearing is reviewed briefly in the Introduction. Subsequent sections describe types of gearing and their geometry, processing, and manufacture. Both conventional and more recent methods of determining gear stress and deflections are considered. The subjects of life prediction and lubrication are additions to the literature. New and more complete methods of power loss predictions as well as an optimum design of spur gear meshes are described. Conventional and new types of power transmission systems are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-RP-1152 , NAS 1.61:1152 , E-2003 , AVSCOM-TR-84-C-15
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  • 4
    Publication Date: 2013-08-31
    Description: Surface fatigue tests were conducted with AISI 9310 spur gears using a formulated synthetic tetraester oil (conforming to MIL-L-23699 specifications) as the lubricant containing either sulfur or phosphorus as the EP additive. Four groups of gears were tested. One group of gears tested without an additive in the lubricant acted as the reference oil. In the other three groups either a 0.1 wt % sulfur or phosphorus additive was added to the tetraester oil to enhance gear surface fatigue life. Test conditions included a gear temperature of 334 K (160 F), a maximum Hertz stress of 1.71 GPa (248 000 psi), and a speed of 10,000 rpm. The gears tested with a 0.1 wt % phosphorus additive showed pitting fatigue life 2.6 times the life of gears tested with the reference tetraester based oil. Although fatigue lives of two groups of gears tested with the sulfur additive in the oil showed improvement over the control group gear life, the results, unlike those obtained with the phosphorus oil, were not considered to be statistically significant.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.60:2408 , E-2042 , NASA-TP-2408
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  • 5
    Publication Date: 2013-08-31
    Description: Tests were conducted at 350 K (170 F) with three groups of 8.9 cm (3.5 in.) pitch diameter spur gears made of vacuum induction melted (VIM) consumable-electrode vacuum-arc melted (VAR), AISI M-50 steel and one group of vacuum-arc remelted (VAR) AISI 9310 steel. The pitting fatigue life of the standard forged and ausforged gears was approximately five times that of the VAR AISI 9310 gears and ten times that of the bending fatigue life of the standard machined VIM-VAR AISI M-50 gears run under identical conditions. There was a slight decrease in the 10-percent life of the ausforged gears from that for the standard forged gears, but the difference is not statistically significant. The standard machined gears failed primarily by gear tooth fracture while the forged and ausforged VIM-VAR AISI M-50 and the VAR AISI 9310 gears failed primarily by surface pitting fatigue. The ausforged gears had a slightly greater tendency to fail by tooth fracture than the standard forged gears.
    Keywords: MECHANICAL ENGINEERING
    Type: E-8258 , NASA-TM-X-71748
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  • 6
    Publication Date: 2013-08-31
    Description: Tests were conducted with two groups of 8.89-centimeter (3.5-in.) pitch diameter spur gears with standard 20 deg involute profile with tip relief made of CVM Super-Nitralloy (5Ni-2Al) and CVM AISI M-50 at a temperature of 350 K (170 F). Super-Nitralloy gears with tip relief had a life 150 percent that of gears without tip relief. An increased scoring phenomenon was noted with the Super-Nitralloy gears with tip relief. Through-hardened AISI M-50 gears with tip relief failed due to tooth fracture. AISI M-50 gears without tip relief had a life approximately 40 times greater than the AISI M-50 gears with tip relief.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7535
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  • 7
    Publication Date: 2013-08-31
    Description: The NASA spinning torque apparatus was modified to measure the spinning torque on a cageless ball thrust bearing. Friction torque was measured for thrust loads varying from 44.5 to 403 newtons (10 to 90 lb) at speeds of 1000, 2000, and 3000 rpm. Tests were conducted with di-2-ethylhexyl sebacate and a synthetic paraffinic oil. These tests were run with either oil jet lubrication or with a thin surface film of lubricant only. An analytical model which included rolling resistance was developed and extended from previous models for spinning torque and lubricant rheology. The model was extended by the inclusion of rolling resistance. The computed values were in fair agreement with the experimental results and confirmed previous hypotheses that a thin lubricant film gives minimum bearing torque and an oil jet flow of a viscous lubricant will result in considerable rolling torque in addition to the torque due to ball spin.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: E-7284 , NASA-TN-D-7356
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  • 8
    Publication Date: 2013-08-31
    Description: The elastohydrodynamic theory for predicting the spinning friction of a ball in a nonconforming groove was modified to incorporate a rheological model. The rheological model is based on the exponential pressure viscosity relation for low shear stresses, but at high shear rates and pressures, the relation is altered to one in which the shear stress is porportional to the normal stress. The model was fitted to experimental spinning torques for four different lubricants: a synthetic paraffinic lubricant, di-2-ethylhexyl sebacate, a super-refined naphthenic mineral oil, and a polyphenyl ether (5P4E). Good agreement between the model and experiment was found.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-7280 , E-7256
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  • 9
    Publication Date: 2013-08-31
    Description: Elastohydrodynamic analysis and experimental speed effects on ball spinning friction coefficients and torque
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-TN-D-5527
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  • 10
    Publication Date: 2013-08-31
    Description: Endurance tests were conducted with four groups of spur gears manufactured from three heats of consumable electrode vacuum melted (CVM) modified Vasco X-2. Endurance tests were also conducted with gears manufactured from CVM AISI 9310. Bench type rolling element fatigue tests were conducted with both materials. Hardness measurements were made to 811 K. There was no statistically significant life difference between the two materials. Life differences between the different heats of modified Vasco X-2 can be attributed to heat treat variation and resultant hardness. Carburization of gear flanks only can eliminate tooth fracture as a primary failure mode for modified Vasco X-2. However, a tooth surface fatigue spall can act as a nucleus of a tooth fracture failure for the modified Vasco X-2.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-1731 , E-070
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