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  • Other Sources  (6)
  • 1990-1994  (6)
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  • 1
    facet.materialart.
    Unknown
    Statistical structural analysis of rotor impact ice shedding (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The statistical characteristics of impact ice shear strength are analyzed, with emphasis placed on the most probable shear strength and statistical distribution of an ice deposit. Several distribution types are considered: the Weibull, two-parameter Weibull, and exponential distributions, as well as the Gumbell distribution of the smallest extreme and the Gumbell distribution of the largest extreme. It is concluded that the Weibull distribution yields the best results; however, the expected life, shape parameter, and scale parameter should be determined separately for each case of varying wind speed and droplet size. The theoretical predictions of shear stresses in a specific rotating ice shape are compared, and it is noted that when the effects of lift are added to the theoretical model and the interference is calculated with a new mean and standard deviation, the probability of ice shed is computed as 36.64 pct.
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: AIAA PAPER 91-0663
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Unknown
    Impact ice stresses in rotating airfoils (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Finite element analysis is used to study the tensile and shear stresses at the interface between impact ice adhering to a rotating airfoil and the metal airfoil surface. A simple rotating beam-ice structure is used to obtain basic understanding of stress distribution in the ice. Calculations show that shear stresses increase linearly with ice thickness and tensile stresses tend to zero for a fully bonded surface. When shear stresses exceed the ultimate strength, adhesive failure occurs and tensile stresses are developed in the unbonded ice, resulting in tensile failure of the impact ice. A second model is used to study the OH-58 tail rotor with a measured ice profile. Ice shedding predictions are compared to the resulting data using a statistical structural analysis.
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: AIAA PAPER 90-0198
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Unknown
    Tensile properties of impact ices (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A special test apparatus was developed to measure the tensile strength of impact ices perpendicular to the direction of growth. The apparatus consists of a split tube carefully machined to minimize the effect of the joint on impact ice strength. The tube is supported in the wind tunnel by two carefully aligned bearings. During accretion the tube is turned slowly in the icing cloud to form a uniform coating of ice on the split tube specimen. The two halves of the split tube are secured firmly by a longitudinal bolt to prevent relative motion between the two halves during ice accretion and handling. Tensile test strength results for a variety of icing conditions were obtained. Both glaze and rime ice conditions were investigated. In general, the tensile strength of impact ice was significantly less than refrigerator ice. Based on the limited data taken, the median strength of rime ice was less than glaze ice. However, the mean values were similar.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: AIAA PAPER 92-0883
    Format: text
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  • 4
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    Unknown
    Influence of aerodynamic forces in ice shedding (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Stresses in accreted ice on a typical airfoil impact ice caused by aerodynamic forces have been studied using finite element analyses. The objective of this study is to determine the significance of these stresses relative to values needed to cause ice shedding. In the case studied, stresses are not significant (less than 10 percent) when compared to the fracture value for airspeeds below a Mach number of 0.45. Above this velocity, the influence of aerodynamic forces on impact ice stresses should be considered in analyses of ice shedding.
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: AIAA PAPER 91-0664
    Format: text
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  • 5
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    Unknown
    A combined analytical-experimental tensile test technique for brittle materials (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A semiconventional tensile test technique is developed for impact ices and other brittle materials. Accurate results have been obtained on ultimate strength and modulus of elasticity in a refrigerated ice test. It is noted that the technique can be used to determine the physical properties of impact ices accreted inside icing wind tunnels or other brittle materials.
    Keywords: NONMETALLIC MATERIALS
    Type: Experimental Techniques (ISSN 0732-8818); 16; 46-50
    Format: text
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  • 6
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    Unknown
    Impact ice stresses in rotating airfoils (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: AIR TRANSPORTATION AND SAFETY
    Type: Journal of Aircraft (ISSN 0021-8669); 28; 450-455
    Format: text
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