Search NASA⌕ Search

SEARCH · Search NASA

Results for “skin effect”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Stiffener-skin interactions in pressure-loaded composite panels

The effects of flange thickness, web height, and skin stiffness on the strain distributions in the skin-stiffener interface region of pressure-loaded graphite-epoxy panels, stiffened by the type-T stiffener, were examined at pressure levels up to one atmosphere. The results indicate that at these pressures geometric nonlinearities are important, and that the overall stiffener stiffness has a significant effect on panel response, particularly on the out-of-plane deformation or pillowing of the skin. The strain gradients indicated that the interface between the skin and the stiffener experiences two components of shear stress, in addition to a normal (peel) stress. Thus, the skin-stiffener interface problem is a three-dimensional problem rather than a two-dimensional one, as is often assumed.

Loup, D. C.↗
NASA NTRSDate not supplied

Effect of Composite Stiffened Panel Design on Skin-Stringer Separation in Postbuckling

To design aeronautical composite multi-stringer panels that can safely operate in a postbuckled state, it is important to identify the parameters that can influence the different modes in which skin-stringer separation might occur. A methodology is under development to study the interaction between the skin-stringer separation and the postbuckling deformation. A simple criterion that can predict the initiation of skin-stringer separation is developed using the building block approach and single-stringer specimens. The criterion identifies whetherthe initiation is mainly due to bending or twisting deformations, so that these two possible modes can be studied separately. This procedure has the potential to reduce the overall development cost and allows the investigation of the design parameters that might precipitate or delay the skin-stringer separation.

Lucas J. Kootte↗
NASA NTRSDate not supplied

Effect of Composite Stiffened Panel Design on Skin-Stringer Separation in Postbuckling

To design aeronautical composite multi-stringer panels that can safely operate in a postbuckled state, it is important to identify the parameters that can influence the different modes in which skin-stringer separation might occur. A methodology is under development to study the interaction between the skin-stringer separation and the postbuckling deformation using the building block approach and single-stringer specimens. In particular, the methodology can identify whether the skin-stringer separation occurs due to bending or twisting, so that these two possible modes can be studied separately. For bending, a simple criterion that can predict the location of initiation is presented. This procedure has the potential to reduce the overall development cost and allows the investigation of the design parameters that influence the skin-stringer separation.

Lucas J. Koote↗
NASA NTRS2016

Effects of Hindlimb Unloading and Ionizing Radiation on Murine Gene Expression in Skin and Bone

Long duration spaceflight causes a negative calcium balance and reduces bone density in astronauts. The underlying mechanisms of spaceflight-induced bone loss and the possible influences of both microgravity and radiation are not fully understood although emerging evidence suggests that these two factors may interact to result in increased bone loss. Previously, gene expression analysis of hair follicles from astronauts, as well as skin from space-flown mice, revealed changes in the expression of genes related to DNA damage and oxidative stress responses. These results resemble the responses of bone to spaceflight-like radiation and simulated weightlessness by hindlimb unloading (HU). Hence in this study, we initiated studies to determine whether skin can be used to predict the responses of bone to simulated microgravity and radiation. We examined oxidative stress and growth arrest pathways in mouse skin and long bones by measuring gene expression levels via quantitative polymerase chain reaction (qPCR). To investigate the effects of irradiation andor HU on gene expression, we used skin and femora (cortical shaft) from the following treatment groups: control (normally loaded, sham-irradiated) (CT), hindlimb unloading (HU), 56Fe radiation (IR) and both HU+IR. Animals were euthanized 11 days post-IR, and results were analyzed by 1-way ANOVA. In skin samples, Cdkn1a was decreased to the same extent in HU and HU+IR (47 of CT). In addition, HU reduced FoxO3 expression (46 of CT) and IR increased Gadd45g expression 135 compared CT in skin. But in bone, HU increased FoxO3 expression 31 compared the level of CT. These results suggest that radiation and simulated weightlessness regulated simliar oxidative stress and cell cycle arrest genes in both skin and bone, although the time course and direction of changes may differ. This research may lead to the development of a relatively simple diagnostic tool for bone loss with the advantage that hair follicles and skin are relatively easy to acquire from subjects.

Terada, Masahiro↗
NASA NTRS2003

Risk of Skin Cancer from Space Radiation

We review the methods for estimating the probability of increased incidence of skin cancers from space radiation exposure, and describe some of the individual factors that may contribute to risk projection models, including skin pigment, and synergistic effects of combined ionizing and UV exposure. The steep dose gradients from trapped electrons, protons, and heavy ions radiation during EVA and limitations in EVA dosimetry are important factors for projecting skin cancer risk of astronauts. We estimate that the probability of increased skin cancer risk varies more than 10-fold for individual astronauts and that the risk of skin cancer could exceed 1 % for future lunar base operations for astronauts with light skin color and hair. Limitations in physical dosimetry in estimating the distribution of dose at the skin suggest that new biodosimetry methods be developed for responding to accidental overexposure of the skin during future space missions.

Cucinotta, Francis A.↗
NASA NTRS1975

Human health effects of ozone reduction

Modification of the stratosphere, such as a reduction in its equilibrium ozone content, could produce direct and indirect effects on human health. The direct hazard to humans would be caused by an increase in the cumulative amount of UV radiation reaching the earth's surface in the range of 285 to 340 nm, encompassing the UV-B or erythemal wavelength region of 280 to 320 nm. Exposing the susceptible human population to an increased total UV dosage of shorter wavelengths could increase skin cancer incidence. Although effects would be delayed by decades, for each 1% decrease in ozone the expected increase in skin cancer incidence would be on the order of 2%.

Source record↗
NASA NTRS1982

A nonintrusive laser interferometer method for measurement of skin friction

A method is described for monitoring the changing thickness of a thin oil film subject to an aerodynamic shear stress using two focused laser beams. The measurement is then simply analyzed in terms of the surface skin friction of the flow. The analysis includes the effects of arbitrarily large pressure and skin friction gradients, gravity, and time varying oil temperature. It may also be applied to three dimensional flows with unknown direction. Applications are presented for a variety of flows including two dimensional flows, three dimensional swirling flows, separated flow, supersonic high Reynolds number flows, and delta wing vortical flows.

Monson, D. J.↗
NASA NTRS1983

A nonintrusive laser interferometer method for measurement of skin friction

A method is described for monitoring the changing thickness of a thin oil film subject to an aerodynamic shear stress using two focused laser beams. The measurement is then simply analyzed in terms of the surface skin friction of the flow. The analysis includes the effects of arbitrarily large pressure and skin friction gradients, gravity, and time varying oil temperature. It may also be applied to three dimensional flows with unknown direction. Applications are presented for a variety of flows, including two dimensional flows, three dimensional swirling flows, separated flow, supersonic high Reynolds number flows, and delta wing vortical flows. Previously announced in STAR as N83-12393

Monson, D. J.↗
NASA NTRS1999

Skin Friction Drag Predictions: Summary of CFD Cross Checks, Wing/Body

The objective of the present study was to address the questions of: 1) how reliably or consistently the Navier-Stokes methods and processes used by the various organizations can predict integrated skin friction drag, and 2) how well the methods can predict trends within a family of optimized configurations. As a first step, all available skin friction drag predictions were accumulated to obtain a mean and standard deviation for the TCA (Technology Concept Airplane) baseline and each of the optimized configurations. It is observed that the optimization process has had little effect on the predicted skin friction drags. The variation in the mean that is observed is dwarfed by the standard deviations. In order to understand the reasons for the relatively large spreads in the computed results, a number of auxiliary computations have been performed using the UPS and OVERFLOW codes in an effort to identify and quantity potential sources of the variations.

Lawrence, Scott↗