The effect was investigated of biaxial loading on the flaw growth rate of 2219-T87 aluminum alloy that would be typical of Space Shuttle cryogenic tankage design. The stress distribution and stress concentration factors for several integrally stiffened panels under various loading conditions were obtained. The flaw growth behavior of both stiffened and unstiffened panels under biaxial loading conditions was determined. The effect of a complex stress state was studied by introducing flaws in...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, CRYOGENIC FLUID STORAGE, LOADS (FORCES),...

The optimal design was investigated of simple structures subjected to dynamic loads, with constraints on the structures' responses. Optimal designs were examined for one dimensional structures excited by harmonically oscillating loads, similar structures excited by white noise, and a wing in the presence of continuous atmospheric turbulence. The first has constraints on the maximum allowable stress while the last two place bounds on the probability of failure of the structure. Approximations...

Topics: NASA Technical Reports Server (NTRS), ATMOSPHERIC TURBULENCE, HARMONIC OSCILLATION, OPTIMAL...

The current experimental program was designed to systematically investigate the role of the oxidizer in the thermal degradation process of composite propellants. The scanning electron microscope (SEM) was used to examine the failure sites in thermally degraded propellant samples. The formulation variables tested were oxidizer purity, oxidizer particle size, and oxidizer to binder bonding agent. The binder, a saturated hydrocarbon, was kept constant throughout the experiments. The oxidizers...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE PROPELLANTS, ELECTRON MICROSCOPES, THERMAL...

Rayleigh-Ritz and modified Rayleigh-Ritz procedures are used to construct approximate solutions for the response of a thick-walled sphere to uniform pressure loads and an arbitrary radial temperature distribution. The thermoelastic properties of the sphere are assumed to be transversely isotropic and nonhomogeneous; variations in the elastic stiffness and thermal expansion coefficients are taken to be an arbitrary function of the radial coordinate and temperature. Numerical examples are...

Topics: NASA Technical Reports Server (NTRS), DYNAMIC STRUCTURAL ANALYSIS, ELASTIC PROPERTIES, TEMPERATURE...

The elastic deformation of two ellipsoidal solids in contact and subjected to Hertzian stress distribution was evaluated numerically as part of a general study of the elastic deformation of such solids in elastohydrodynamic contacts. In the analysis the contact zone was divided into equal rectangular areas, and it was assumed that a uniform pressure is applied over each rectangular area. The influence of the size of the rectangular area upon accuracy was also studied. The results indicate the...

Topics: NASA Technical Reports Server (NTRS), BALL BEARINGS, ELASTIC DEFORMATION, ELASTOHYDRODYNAMICS,...

An improved procedure for the three dimensional finite element analysis of an angle ply laminate with a circular hole is discussed. The procecure exploits polar symmetry and is the basis for a new finite element computer code. For the broad class of laminates that contain angle plies, this code requires only one half as much computing capacity as conventional codes.

Topics: NASA Technical Reports Server (NTRS), FINITE ELEMENT METHOD, LAMINATES, STRESS ANALYSIS, SYMMETRY,...

The bump protection hat (BPH) was subjected to impact testing in which it underwent three impacts at 35 foot-pounds of energy. The impacts generated stress cracks, but no penetration. All impacts resulted in deflections of less than one-half inch. It was shown that the BPH is qualified for Skylab and the rescue vehicle.

Topics: NASA Technical Reports Server (NTRS), HELMETS, IMPACT TESTS, SKYLAB PROGRAM, ACCEPTABILITY, CRACK...

The plane elastostatic problem of internal and edge cracks in an infinite orthotropic strip is considered. The problems for the material types 1 and 2 are formulated in terms of singular integral equations. For the symmetric case the stress intensity factors are calculated and are compared with the isotropic results. The results show that because of the dependence of the Fredholm kernels on the elastic constants, unlike the crack problem for an infinite plane, in the strip the stress intensity...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, CRACKS, ORTHOTROPIC PLATES, ELASTOSTATICS,...

The report consists of four sections. The first section describes tilt and leveling measurements on Anegada, the most northerly of the British Virgin Islands; the second section contains a discussion of sea-level measurements that were initiated in the region and which played a significant role in the development of a network of sea-level monitors now telemetered via satellite from the Alaskan Shumagin Islands. The third part of the report is a brief description of surface deformation...

Topics: NASA Technical Reports Server (NTRS), ELASTIC DEFORMATION, GEOLOGICAL SURVEYS, ICELAND, SURFACE...

The problem of a laminate composite in the presence of a crack located normal to the bond lines is considered. Stress analysis of the limiting case when the crack extends to the bond lines is carried out. An integral transform technique is used to formulate the problem in terms of a singular integral equation. The power of stress singularity around the crack tip terminating at the interface is obtained using the above technique. The singular integral equation is solved numerically and the...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE MATERIALS, CRACKING (FRACTURING), INTEGRAL...

355
355

May 6, 2010
05/10

by
Dauwatter, C. R.; Gilinson, P. J., Jr.; Scoppettuolo, J. A

texts

######
eye 355

######
favorite 0

######
comment 0

Multirange precision torque measuring system

Topics: FEEDBACK, WATTMETERS, ELECTROMAGNETIC INSTRUMENT, FEEDBACK, MEASURING APPARATUS, PRECISION,...

Papers are presented dealing with structural dynamics; structural synthesis; and the nonlinear analysis of structures, structural members, and composite structures and materials. Applications of mathematics and computer science are included.

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMMING, CONFERENCES, DYNAMIC STRUCTURAL...

A review of recent developments in the calculation of design parameters for fracture mechanics by the method of lines (MOL) is presented. Three dimensional elastic and elasto-plastic formulations are examined and results from previous and current research activities are reported. The application of MOL to the appropriate partial differential equations of equilibrium leads to coupled sets of simultaneous ordinary differential equations. Solutions of these equations are obtained by the...

Topics: NASA Technical Reports Server (NTRS), FRACTURE MECHANICS, LOAD TESTS, STRESS DISTRIBUTION,...

Experimental work in support of stress studies in high speed silicon sheet growth has been emphasized in this quarter. Creep experiments utilizing four-point bending have been made in the temperature range from 1000 C to 1360 C in CZ silicon as well as on EFG ribbon. A method to measure residual stress over large areas using laser interferometry to map strain distributions under load is under development. A fiber optics sensor to measure ribbon temperature profiles has been constructed and is...

Topics: NASA Technical Reports Server (NTRS), LASER INTERFEROMETRY, LOADS (FORCES), RESIDUAL STRESS,...

Simplified inelastic analysis procedures were developed at NASA Lewis and Pratt & Whitney Aircraft for predicting the stress-strain response at the critical location of a thermomechanically cycled structure. These procedures are intended primarily for use as economical structural analysis tools in the early design stages of aircraft engine hot section components where nonlinear finite-element analyses would be prohibitively expensive. Both simplified methods use as input the total strain...

Topics: NASA Technical Reports Server (NTRS), FATIGUE (MATERIALS), PREDICTION ANALYSIS TECHNIQUES, STRESS...

The problem of a finite crack in an infinite medium under antiplane shear load is considered. It is shown that the nodal forces at the tip of the crack accurately gives the order of singularity, that n energy release methods can give the strength to better than 1 percent with element size 1/10 the crack length, and that nodal forces give a much better estimate of the stress field than do the elements themselves. The finite element formulation and the factoring of tridiagonal matrices are...

Topics: NASA Technical Reports Server (NTRS), CONVERGENCE, CRACKS, FINITE ELEMENT METHOD, SHEAR STRESS,...

Mechanical properties and stress-strain behavior for several types of commercially fabricated aluminum matrix composites, containing up to 40 vol % discontinuous SiC whisker, nodule, or particulate reinforcement were evaluated. It was found that the elastic modulus of the composites was isotropic, to be independent of type of reinforcement, and to be controlled solely by the volume percentage of SiC reinforcement present. The yield/tensile strengths and ductility were controlled primarily by...

Topics: NASA Technical Reports Server (NTRS), METAL MATRIX COMPOSITES, SILICON CARBIDES, STRESS...

Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of...

Topics: NASA Technical Reports Server (NTRS), THERMAL STRESSES, THERMOELASTICITY, MECHANICAL PROPERTIES,...

The research carried out here builds on our previous NASA supported research on the general topic of edge effects and load diffusion in composite structures. Further fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for the multi-functional large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures....

Topics: NASA Technical Reports Server (NTRS), COMPOSITE STRUCTURES, DIFFUSION, LOADS (FORCES),...

An analysis of adhesively bonded joints using conventional finite elements does not capture the singular behavior of the stress field in regions where two or three dissimilar materials form a junction with or without free edges. However, these regions are characteristic of the bonded joints and are prone to failure initiation. This study presents a method to capture the singular stress field arising from the geometric and material discontinuities in bonded composites. It is achieved by coupling...

Topics: NASA Technical Reports Server (NTRS), ADHESIVE BONDING, STRESS DISTRIBUTION, FINITE ELEMENT METHOD,...

Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional...

Topics: NASA Technical Reports Server (NTRS), POLYMER MATRIX COMPOSITES, MECHANICAL PROPERTIES,...

Isotropic rib stiffened shell whose ribs intersect to form equilateral triangles has advantages of high twisting rigidity of construction and simplicity of triangular pattern.

Topics: NASA Technical Reports Server (NTRS), BENDING, BUCKLING, GRIDS, ISOTROPISM, REINFORCED SHELLS,...

216
216

May 31, 2011
05/11

by
Hunter, Steve L.; Dischinger, Charles; Estes, Samanth

texts

######
eye 216

######
favorite 0

######
comment 0

Most, if not all, 3-D and Virtual Reality (VR) software programs are designed for one-G gravity applications. Space environments simulations require gravity effects of one one-thousandth to one one-million of that of the Earth's surface (10(exp -3) - 10(exp -6) G), thus one must be able to generate simulations that replicate those microgravity effects upon simulated astronauts. Unfortunately, the software programs utilized by the National Aeronautical and Space Administration does not have the...

Topics: COMPOSITE STRUCTURES, CRACKS, PREDICTION ANALYSIS TECHNIQUES, COMPUTATIONAL GRIDS, FAILURE MODES,...

For each of the two types of specimens, bend and compact, described previously for plane strain fracture toughness of materials, E 399, a polynominal expression is given for calculation of the stress intensity factor, K, from the applied force, P, and the specimen dimensions. It is explicitly stated, however, that these expressions should not be used outside the range of relative crack length, a/W, from 0.45 to 0.55. While this range is sufficient for the purpose of E 399, the same specimen...

Topics: NASA Technical Reports Server (NTRS), FORMULAS (MATHEMATICS), FRACTURE STRENGTH, MATERIALS TESTS,...

Cyclic-load crack growth measurements were performed on ASME SA-105 Grade 2 steel specimens exposed to 10,000- and 15,000-psi hydrogen and to 5000-psi helium, all at ambient temperatures. The cyclic-load crack growth rate was found to be faster in high-pressure hydrogen than in helium. Cyclic-load crack growth rates in this steel were not reduced by preloading in air to a stress intensity of 1.5 times the cyclic K sub max in hydrogen. There are indications that holding under load in hydrogen,...

Topics: NASA Technical Reports Server (NTRS), AMBIENT TEMPERATURE, CRACK INITIATION, HELIUM, HYDROGEN,...

Global/local method in conjunction with a special macro finite element is used to gain computational efficiency in the simulation of textile composites behavior. Results are included to demonstrate the effectiveness of the method. Also, 2D finite elements are used to study boundary effects in plain weave composite specimens subjected to extension, shear, and flexure loads. Effective extension, shear, and flexural moduli were found to be quite sensitive to specimen size. For extension and...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE STRUCTURES, FIBER COMPOSITES, FINITE ELEMENT...

The tectonic forces or stresses due to the small scale mantle flow under the South American plate are detected and determined by utilizing the harmonics of the geopotential field model. The high degree harmonics are assumed to describe the small scale mantle convection patterns. The input data used in the derivation of this model is made up of 840,000 optical, electronic, and laser observations and 1,656 5 deg x 5 deg mean free air anomalies. Although there remain some statistically...

Topics: NASA Technical Reports Server (NTRS), EARTH GRAVITATION, EARTH MANTLE, GRAVITATIONAL FIELDS,...

An isotropic sheet stiffened by means of an orthotropic quarter-plate is considered. The quarter-plate is assumed to be perfectly bonded to the metal sheet everywhere except an area of debonding which may develop due to high stress concentrations. The adhesive which has a small constant thickness is treated as a shear spring. The loads are applied at infinity and supposed to be transmitted through the metal plate. Shear stress distribution between the two plates was obtained from the continuity...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE MATERIALS, METAL SHEETS, STIFFNESS, STRESS...

The elastic deformation of two ellipsoidal solids in contact and subjected to a Hertzian stress distribution was evaluated numerically as part of a general study of the elastic deformation of such solids in elastohydrodynamic contacts. In the analysis the contact zone is divided into equal rectangular areas and it is assumed that a uniform pressure is applied over each rectangular area. A study was made of the influence on the size of the rectangular area upon accuracy. The results also...

Topics: NASA Technical Reports Server (NTRS), ELASTIC DEFORMATION, NUMERICAL ANALYSIS, SOLIDS, SURFACE...

Previous attempts to develop an appropriate sensor for measuring the stress or strain of high altitude balloons during flight are reviewed as well as the various conditions that must be met by such a device. The design, development and calibration of a transducer which promises to satisfy the necessary design constraints are described. The thin film strain transducer has a low effective modulus so as not to interfere with the strain that would naturally occur in the balloon. In addition, the...

Topics: NASA Technical Reports Server (NTRS), HIGH ALTITUDE BALLOONS, STRAIN GAGES, STRESS DISTRIBUTION,...

A model describing the failure in tempered glass is proposed and a method of solution is presented. An infinite elastic strip is assumed to represent the glass and the loads vanish everywhere on the boundary as well as at infinity. The problem is solved using the integral equations technique where the input is the residual stresses in the glass.

Topics: NASA Technical Reports Server (NTRS), CRACKING (FRACTURING), GLASS, STRESS DISTRIBUTION, TEMPERING,...

The relationship between several semiempirical fracture analyses (SEFA) and the R-curve concept of fracture mechanics is examined. The conditions for equivalence between a SEFA and an R-curve are derived. A hypothetical material is employed to study the relationship analytically. Equivalent R-curves are developed for real materials using data from the literature. For each SEFA there is an equivalent R-curve whose magnitude and shape are determined by the SEFA formulation and its empirical...

Topics: NASA Technical Reports Server (NTRS), CRACK INITIATION, CRACK PROPAGATION, FRACTURE MECHANICS,...

325
325

Jul 25, 2010
07/10

by
Power, John L.; Chapman, Randall A

texts

######
eye 325

######
favorite 0

######
comment 0

This paper describes the current development of a high-power microwave electrothermal thruster (MET) concept at the NASA Lewis Research Center. Such a thruster would be employed in space for applications such as orbit raining, orbit maneuvering, station change, and possibly trans-lunar or trans-planetary propulsion of spacecraft. The MET concept employs low frequency continuous wave (CW) microwave power to create and continuously pump energy into a flowing propellant gas at relative high...

Topics: COMPUTER PROGRAMS, STRESS-STRAIN RELATIONSHIPS, TEMPERATURE EFFECTS, DEFORMATION, FINITE ELEMENT...

197
197

Jul 26, 2010
07/10

by
Kern, Lura E.; Belle, Steve D.; Duke, Eugene L

texts

######
eye 197

######
favorite 0

######
comment 0

When analyzing the performance of an aircraft, certain simplifying assumptions, which decrease the complexity of the problem, can often be made. The degree of accuracy required in the solution may determine the extent to which these simplifying assumptions are incorporated. A complex model may yield more accurate results if it describes the real situation more thoroughly. However, a complex model usually involves more computation time, makes the analysis more difficult, and often requires more...

Topics: AXIAL STRAIN, THERMAL RESISTANCE, VISCOPLASTICITY, CREEP ANALYSIS, ELASTIC PROPERTIES,...

Methods for solving three dimensional crack problems are discussed. The stress intensity factor for the case of uniform pressure on the surface crack is analysis. An analysis of concentrated forces acting on the crack faces parallel to the crack front of a half-plane crack was made. Two dimensional calculations were made using the exact solution for the stress field around an elliptical hole in a uniformly stretched plate. The strain energy density was computed in the neighborhood of the ends...

Topics: NASA Technical Reports Server (NTRS), CRACKING (FRACTURING), STRESS ANALYSIS, SURFACE CRACKS,...

The problem of a cylindrical shell containing a circumferential through crack is considered by taking into account the effect of transverse shear deformations. The formulation is given for a specially orthotropic material within the confines of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions regarding moment and stress resultants on the crack surface. Consequently, aside from multiplicative constants representing the stress...

Topics: NASA Technical Reports Server (NTRS), CRACKING (FRACTURING), CYLINDRICAL SHELLS, SHEAR STRESS,...

In April, 1989, a workshop on constitutive relationships and models in continuum theories of multiphase flows was held at NASA's Marshall Space Flight Center. Topics of constitutive relationships for the partial or per phase stresses, including the concept of solid phase pressure are discussed. Models used for the exchange of mass, momentum, and energy between the phases in a multiphase flow are also discussed. The program, abstracts, and texts of the presentations from the workshop are...

Topics: NASA Technical Reports Server (NTRS), CONSTITUTIVE EQUATIONS, CONTINUUM MECHANICS, MATHEMATICAL...

A technique consisting of a marriage between stress freezing photoelasticity and a numerical method was used to obtain stress intensity factors for natural cracks emanating from the corner at which a hole intersects a plate surface. Geometrics studied were: crack depth to thickness ratios of approximately 0.2, 0.5, and 0.75; crack depth to crack length ratios of approximately 1.0 to 2.0. All final crack geometries were grown under monotonic loading and growth was not self similar with most of...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, HOLE DISTRIBUTION (MECHANICS), HOLES...

The role of adrenal glucocorticoids and ACTH in behavior, and the influence of various behavioral situations on the neuroendocrine regulation of the pituitary-adrenal system were investigated. Results are presented and discussed.

Topics: NASA Technical Reports Server (NTRS), ADRENAL GLAND, BEHAVIOR, PITUITARY GLAND, STRESS...

The input and output formats and options are described along with the technical approaches used within the computer program. Included are example data and problems.

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMMING, CRACK PROPAGATION, USER MANUALS...

Several intact or broken stringers which are continuously attached to a cracked orthotropic sheet through an adhesive are considered. The effect of orthotropy on the stress intensity factors is investigated. The stringers are assumed to be partially debonded due to high stress concentrations. The shear stress distribution between the stringers and the plate and the stress intensity factors are obtained from an integral equation which represents the continuity of displacements along the bond...

Topics: NASA Technical Reports Server (NTRS), CRACKING (FRACTURING), METAL SHEETS, ORTHOTROPISM, STRINGERS,...

The crack-closure and crack-growth characteristics of the titanium alloy Ti-6Al-4V were determined experimentally on surface-flawed plate specimens. Under cyclic loading from zero to tension, cracks deeper than 1 mm opened at approximately 50 percent of the maximum load. Cracks shallower than 1 mm opened at higher loads. The correlation between crack-growth rate and the total stress-intensity range showed a lower threshold behavior. This behavior was attributed to the high crack-opening loads...

Topics: NASA Technical Reports Server (NTRS), ALUMINUM ALLOYS, CRACK INITIATION, SURFACE DEFECTS, TITANIUM...

A method of measuring the longitudinal residual stress distribution in boron fibers is presented. The residual stresses in commercial CVD boron on tungsten fibers of 102, 142, and 203 microns (4, 5.6, and 8 mil) diameters were determined. Results for the three sizes show a compressive stress at the surface 800 to -1400 MN/sq m 120 to -200 ksi), changing monotonically to a region of tensile stress within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum...

Topics: NASA Technical Reports Server (NTRS), BORON REINFORCED MATERIALS, REINFORCING FIBERS, RESIDUAL...

An equation governing the prior to failure crack propagation is proposed. For a rate-sensitive solid containing two-dimensional crack and subject to the tensile mode of fracture, the differential equations are integrated numerically for the loads increasing monotonically in time. The resulting integral curves sigma = sigma(l) and l = l(t), i.e. load vs. crack length and length vs. time, indicate that the growth of cracks in the subcritical range is strongly rate dependent. The fatigue growth,...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, FATIGUE (MATERIALS), LOADS (FORCES),...

The development of the first version of a minicomputer controlled system that converts the fringe pattern motion into a voltage output proportional to displacement is presented. Details of the instrument and the calibration tests are included.

Topics: NASA Technical Reports Server (NTRS), DIFFRACTION PATTERNS, FRACTURE MECHANICS, INTERFEROMETERS,...

Electrical characterization of defects induced in FZ and CZ silicon stress in four-point bending above 1200 C was started. Techniques to study electrical activity that will permit correlation of defect activity with diffusion length and with room and low temperature EBIC are being developed. Preliminary characterization of defects in ribbon grown at very low speeds of less than 1 cm/min shows that the dislocation density is very low over significant regions of cross section, while regions of...

Topics: NASA Technical Reports Server (NTRS), CREEP PROPERTIES, CRYSTAL DEFECTS, CZOCHRALSKI METHOD, SOLAR...

Results of planar boundary collocation analysis are given for ring segment (C shaped) specimens with radial cracks, subjected to combined forces and couples. Mode I stress intensity factors and crack mouth opening displacements were determined for ratios of outer to inner radius in the range 1.1 to 2.5, and ratios of crack length to segment width in the range 0.1 to 0.8.

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, FORCE DISTRIBUTION, RING STRUCTURES, CRACK...

The object of the project was to determine experimentally the stress distribution in cylindrically hollow and spherically hollow balls. Ball models several times actual bearing ball size were fabricated. Strain gage rosettes will be mounted on the outside and inside surfaces of the models at specific locations and orientations. The models were subjected to a range of static loads simulating actual ball-race contact loads experienced in high-speed bearings operating at DN values from 2 to 4...

Topics: NASA Technical Reports Server (NTRS), ANTIFRICTION BEARINGS, BALL BEARINGS, PERFORMANCE TESTS,...

The thermal stresses on a cryogenic storage tank strongly affect the condition of the tank and its ability to withstand operational stresses. These thermal stresses also affect the growth of any surface damage that might occur in the tank walls. These stresses are particularly of concern during the initial cooldown period for a new tank placed into service, and during any subsequent thermal cycles. A preliminary thermal stress analysis of a high-pressure cryogenic storage tank was performed....

Topics: NASA Technical Reports Server (NTRS), CRYOGENIC TEMPERATURE, HIGH PRESSURE, STORAGE TANKS, STRESS...

A procedure is presented for performing three-dimensional stress analysis of spiral bevel gears in mesh using the finite element method. The procedure involves generating a finite element model by solving equations that identify tooth surface coordinates. Coordinate transformations are used to orientate the gear and pinion for gear meshing. Contact boundary conditions are simulated with gap elements. A solution technique for correct orientation of the gap elements is given. Example models and...

Topics: NASA Technical Reports Server (NTRS), STRESS DISTRIBUTION, FINITE ELEMENT METHOD, SPIRAL BEVEL...