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Showing papers by "Wright-Patterson Air Force Base published in 1971"


Journal ArticleDOI
TL;DR: In this article, an operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors, which satisfies the invariant requirements of coordinate transforma tion, takes into account the difference in strengths due to positive and negative stresses, and can be specialized to account for different material symmetries, multi-dimensional space, and multi-axial stresses.
Abstract: An operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors. Differing from existing quadratic approximations of failure surfaces, the present theory satisfies the invariant requirements of coordinate transforma tion, treats interaction terms as independent components, takes into account the difference in strengths due to positive and negative stresses, and can be specialized to account for different material symmetries, multi-dimensional space, and multi-axial stresses. The measured off-axis uniaxial and pure shear data are shown to be in good agreement with the predicted values based on the present theory.

3,030 citations


Journal ArticleDOI
TL;DR: In this article, the infrared and Raman frequencies of monoclinic zirconia and stabilized and metastable tetragonal and cubic cubic Zirconias were established, and the effects of heating, grinding and adding stabilizing oxides on the ir spectra were determined.
Abstract: The infrared and Raman frequencies of monoclinic zirconia and of stabilized and metastable tetragonal and cubic zirconias were established. Infrared spectra were examined by the powder transmission (CsI pellet) and surface reflection techniques. The effects of heating, grinding, and adding stabilizing oxides on the ir spectra were determined. The spectra develop additional bands as the crystal symmetry is lowered, and certain of these bands are highly sensitive to strain-induced distortions of the crystal lattice. Practical applications of ir and Raman spectroscopy to zirconia technology are discussed.

420 citations


Journal ArticleDOI
TL;DR: In this paper, a systematic study was made of ignition delay times behind a reflected shock wave of the alkanes methane through pentane in stoichiometric argon simulated air mixtures.

263 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed an alternate procedure for obtaining the activity of the vibrations from the correlation tables which comes close to meeting these goals The calculation is reduced to but a few minutes' work The method will be explained in detail by use of numerous examples.
Abstract: With the recent growth in interest in the ir and Raman spectra of crystals, it has become very important to know which vibrational modes are optically active Hornig, Winston and Halford, and Bhagavantam and Venkatarayudu pioneered in developing methods for this However, heretofore the determination has been a laborious procedure fraught with difficulty and with many points of indecision Among the latter is the choice of the primitive cell and the correct site symmetry of each atom What is needed is a short, straightforward, foolproof method We propose here an alternate procedure for obtaining the activity of the vibrations from the correlation tables which comes close to meeting these goals The calculation is reduced to but a few minutes' work The method will be explained in detail by use of numerous examples

253 citations


Journal ArticleDOI
TL;DR: In this article, both hot-pressed and sintered Cr2O3 pellets were investigated in O2/Ar gas mixtures and the dependence of the weight loss on the O2 partial pressure, the gas flow rate, and the total pressure was determined independently.
Abstract: The weight loss of Cr2O3 in oxidizing environments (Po2= 1 to 10−3 atm) at 1200°C was measured. Both hot-pressed and sintered Cr2O3 pellets were investigated in O2/Ar gas mixtures, and the dependence of the weight loss on the O2 partial pressure, the gas flow rate, and the total pressure was determined independently. The experimentally determined O2 partial pressure dependence (rate ∝ PO23/4) corresponds to that expected for the reaction Cr2O3(s)+3/2O2⇌2CrO3(g). The flow rate and total pressure dependencies show that mass transport through a gaseous boundary layer is the rate-controlling step in the oxidation/vaporization of Cr2O3. Evaporation coefficients for the loss of CrO3(g) under the experimental conditions were <0.01.

230 citations


Journal ArticleDOI
TL;DR: In this paper, a generalized Duhamel-Neumann form of Hooke's law is used to develop laminated plate equations which include the effect of expansional strains, such as temperature, absorption by a polymeric matrix material of a swelling agent such as water vapor, and by sudden expansion of absorbed gases in the matrix.
Abstract: A generalized Duhamel-Neumann form of Hooke's law is used to develop laminated plate equations which include the effect of expansional strains. Such strains are induced in composite materials by temperature, absorption by a polymeric matrix material of a swelling agent such as water vapor, and by sudden expansion of absorbed gases in the matrix. Solutions to specific boundary value problems are presented for both symmetric and nonsymmetric laminates. Numerical results indicate that in addition to inducing residual stresses, expansional strains can substantially affect the gross response characteristics of a composite material.

211 citations


Journal ArticleDOI
TL;DR: In this paper, the authors identify some potentially critical areas of viscous interactions associated with high Mach number vehicles and briefly review their state of knowledge in these areas with emphasis on the basic flow phenomena.
Abstract: T most severe problems of atmospheric flight at high Mach numbers are associated with viscous-inviscid interactions. Cruise vehicles for Mach numbers above four and lifting re-entry vehicles have highly complex three-dimensional configurations in which exist many regions of high compression that can cause boundary layers to separate. Although separation can result in loss of control effectiveness or flow degradation in an engine inlet, flow reattachment gives rise to heat rates that can far exceed those for an attached boundary layer. A further, and possibly far more severe viscous interaction problem is the impingement of shock waves generated by the forebody and other external components of a vehicle on aft sections resulting in local heat rates that may be many times larger than stagnation point values. Peak heating conditions may be laminar for lifting re-entry configurations, though our knowledge of boundary layertransition is far from adequate so that transitional and turbulent flows cannot be ruled out. However, Reynolds num, bers of potential high Mach number cruise vehicles are high— 10 to 10—so that viscous interactions will be predominately associated with turbulent boundary layers and their attendant higher heat rates. The high local heat rates resulting from viscous interactions cause "hot spots" that could lead to catastrophic failure. Vivid examples of damage resulting from viscous interactions are given in Figs. 1 and 2. A ventral pylon on the X-15 airplane, shown in Fig. 1, caused high^local heating of the fuselage around its root, and developed large holes near its tip due to the impingement of the shock wave from a dummy ramjet it supported, during a flight at Mach 6.7 in 1967. A study of the flowfield of the pylon-mounted dummy ramjet configuration is reported in Ref. 1. Figure 2 shows considerable damage due to interaction heating to the underside of a sled and its supporting slipper as a result of a run at 7000 fps on the 7-mile test track at Holloman Air Force Base. Unlike stagnation-point heating where the location is obvious, the problem with complex configurations is to determine "where" high heat rates are likely to occur, as well as their magnitude. It is the purpose of this paper to identify some potentially critical areas of viscous interactions associated with high Mach number vehicles and briefly review our state of knowledge in these areas with emphasis on the basic flow phenomena.

189 citations


Journal ArticleDOI
TL;DR: Recent studies of the anthropometry and selected biomechanical characteristics of hands are summarized and the utility of these data for human factors engineering is discussed.
Abstract: Recent studies of the anthropometry and selected biomechanical characteristics of hands are summarized. These include: (1) conventional anthropometry of male and female hands, (2) the anthropometry of the relaxed hand, (3) comparison of certain engineering anthropometric and performance parameters between bare and pressure-gloved hands, and (4) the ability to retain grips on selected handles under high dynamic loads. The utility of these data for human factors engineering is discussed.

186 citations


Journal ArticleDOI
TL;DR: In this paper, the energy levels of core electrons in ZnO, ZnS and CdTe were determined using X-ray-induced electron-emission measurements.
Abstract: X-ray induced electron-emission measurements were used to determine the energy levels of core electrons in ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, HgS, HgSe, and HgTe. The investigated energy range extends from the bottom of the valence band to about 1200 eV below the Fermi level. Chemical shifts were determined by comparing our results with experimental values for the pure elements. These shifts are plotted as a function of the fractional ionicity values determined by Phillips and Van Vechten, Pauling, and Coulson. Spinorbit-splitting values were experimentally determined for the first time for several levels including the $\mathrm{Zn}3d$, $\mathrm{Cd}4d$, and $\mathrm{Hg}5d$ levels. Furthermore, our measured energy values for these levels are used to determine the absolute energy values of the initial and final states of transitions normally labeled ${d}_{2}$ in ultraviolet reflectivity and electron-energy-loss measurements. Our results for ZnSe and CdTe are compared with self-consistent relativistic orthogonalized-plane-wave calculations for the excitation energies of these compounds. Agreement with these theoretical calculations is best for the levels closest to the valence band and appears to be angular momentum dependent.

170 citations


Journal ArticleDOI
TL;DR: In this article, the ignition delay of a single-pulse shock tube was examined in a mixture of methane-oxygen mixtures with argon and was found to be correlated with the concentration of the additive, which acts as a booster.

164 citations


Journal ArticleDOI
TL;DR: In this paper, a laminate analogy for predicting the elastic stiffness and thermal expansion properties of a randomly oriented short fiber composite is extended to include a large class of fiber reinforced composites possessing very complex geometry.
Abstract: A previously developed laminate analogy for predicting the elastic stiffness and thermal expansion properties of a randomly oriented short fiber composite is extended to include a large class of fiber reinforced composites possessing very complex geometry. In particular, the stiffness and thermal expansion coefficients of short fiber com posites having biased filaments, misaligned filaments, and variable fiber aspect ratios are determined from a laminate analogy. In addition, the laminate analogy is extended to 2 and 3 dimensional woven fabric composites. Theoretical results for the short fiber com posites show excellent agreement with experimental results, while theoretical results for the woven fabric composites are shown to be qualitatively correct.

Journal ArticleDOI
TL;DR: In this article, a detailed theoretical and experimental analysis of the rail shear test is presented, where a Fourier series solution is obtained for the stresses in an idealized rail-shear specimen.
Abstract: A detailed theoretical and experimental analysis of the rail shear test is presented. A Fourier series solution is obtained for the stresses in an idealized rail shear specimen. The theoretical results are quali tatively verified on fiber reinforced rubber composites. Rail shear data on the modulus and strength of current high-modulus rein forced composites is compared to predicted values obtained from lamination theory. Results show that, despite definite limitations, the rail shear test can be useful in the determination of the in-plane shear properties of a laminated composite.

Journal ArticleDOI
TL;DR: In this article, the soft X-ray CrL III, CrK and OK emission and absorption spectra are combined and used to construct empirically a complete molecular orbital diagram for simple chromium-oxygen compounds.

Journal ArticleDOI
TL;DR: Equal intensity curves derived from the magnitude estimation data show the same general shape and comparable levels as corresponding curves determined experimentally using the intensity matching procedure, providing more systematic and quantitative characterizations of subjective response to vibration than previous approaches.
Abstract: Using the methods of magnitude estimation and intensity matching, curves of equal subjective vibration intensity were constructed over the frequency range from 3.5 to 20 Hz. Twenty subjects made magnitude estimations of the intensity of vibration at 0.08, 0.16, 0.24, 0.40, 0.48, and 0.56 gz with vibration at 0.32 gz serving as a standard. These intensities were judged at each of the frequencies of 3.5, 5, 7, 9, 11, 15, and 20 Hz. For each frequency, the results were plotted as straight-line functions on log-log graphs of subjective intensity against physical intensity. The slopes of the lines varied as a function of frequency, the steepest slope occurring at 5 Hz. (the frequency of greatest body response due to resonance in this axis). Additional experiments were conducted in which ten subjects matched the intensity of 9-Hz. vibration at 0.16, 0.36, and 0.56 gz with vibration at each of the other six frequencies listed above, and ten different subjects made similar equality judgments against 9-Hz. vibrati...

Journal ArticleDOI
TL;DR: In this article, a 0.5 wt% molybdenum dispersed phase was added to alumina with metallographic and X-ray diffraction analyses, and microhardness, elastic moduli, tensile strength, and fracture energy were determined.
Abstract: Compositions of alumina with a molybdenum dispersed phase were investigated in the 0 to 5 vol% Mo range. These compositions were also prepared with a 0.5 wt% MgO addition. All specimens were fabricated by hot-pressing, and near theoretical densities were achieved. Specimens were characterized by metallographic and X-ray diffraction analyses, and microhardness, elastic moduli, tensile strength, and fracture energy were determined. Results revealed that Mo additions did not affect grain growth; in contrast, MgO additions significantly inhibited grain growth. However, Mo additions did reduce the elastic moduli and microhardness but did not measurably affect the tensile strength. Tensile strength was dependent on grain size and fitted the G−1/3 relation. The fracture energy of Al2O3+5% Mo was 50% greater than that of Al2O3. Specimens were successfully hot-pressed with a micro-structure graded from that of Al2O3 to that of the 5% Mo composition.

Journal ArticleDOI
01 Jan 1971
TL;DR: In this paper, a detailed shock tube study of ignition delay times in propane-oxygen-argon mixtures is presented, where ignition delays were determined from pressure and heat-flux measurements in the reflected shock region.
Abstract: A detailed shock-tube study of ignition-delay times in propane-oxygen-argon mixtures is presented. Ignition delays were determined from pressure and heat-flux measurements in the reflected shock region. The induction times measured ranged from 12 to 600 μsec and the temperature range covered was 1250°–1600°K. The pressures varied from 2 to 10 atm, and the equivalence ratios of the various mixtures ranged from 0.125 to 2.0 The influence of each parameter on ignition-delay times was separately determined. The dependence upon the concentrations close to stoichiometric composition, derived from more than 150 shocks is the following: τ = 4.4 × 10 − 14 exp ⁡ [ ( 42.2 × 10 3 ) / RT ] [ Ar ] 0 [ C 3 H 8 ] 0.57 [ O 2 ] − 1.22 sec ⁡ , where the concentrations are in moles/cc. Additional experiments were carried out in order to determine the product distribution before and after ignition. Considerable decomposition of propane takes place before ignition. The rate of decomposition is close to that of pure propane, and is very little affected by the presence of oxygen.

Journal ArticleDOI
TL;DR: In this article, exact solutions within the framework of linear elasticity theory were developed and compared to the respective solutions governed by CPT, and numerical data calculated based on simple harmonic load distributions have indicated rather wide discrepancy between the two solutions for laminates having low span to depth ratios.
Abstract: In a series of three papers [1,2,3], the range of applicability of classical laminated plate theory (CPT) in describing the response of composite laminates under static bending has been examined. Briefly, exact solutions within the framework of linear elasticity theory were developed and compared to the respective solutions governed by CPT [4,5,6]. Numerical data calculated based on simple harmonic load distributions have indicated rather wide discrepancy between the two solutions for laminates having low span-to-depth ratios. At high aspect ratios however, the CPT solution is in good agreement with the elasticity solution.

Journal ArticleDOI
TL;DR: A machine for testing thin-walled tubes in torsion at shear-strain rates up to 25/sec is described in this paper, and constant and variable-rate tests are presented for 1100-0 aluminum, AISI 1020 steel, and 50-A titanium.
Abstract: A machine for testing thin-walled tubes in torsion at shear-strain rates up to 25/sec is described Results of constant and variable-strain-rate tests are presented for 1100-0 aluminum, AISI 1020 steel, and 50-A titanium Results indicate that 1100-0 aluminum is very slightly strain-rate sensitive, but steel and titanium are noticeably sensitive to both strain rate and strain-rate history Variable-rate tests show that subsequent dynamic loading on a statically prestrained specimen causes an increase in the flow stress in steel and a decrease in the flow stress in titanium

Journal ArticleDOI
TL;DR: In this paper, a fine particle size, high-purity BaTiO3 powder was used to fabricate sintered and hot-pressed specimens and the dielectric properties of many specimens had frequency dispersions characteristic of interfacial polarization or other related space charge effects.
Abstract: Fine particle size, high-purity BaTiO3 powder was used to fabricate sintered and hot-pressed specimens. A second phase, BaTi3O7, frequently developed in samples fired at high temperatures. The dielectric properties of many specimens had frequency dispersions characteristic of interfacial polarization or other related space charge effects. Controlled particle size specimens were fabricated by hot-pressing and the temperature dependence of their dielectric properties was evaluated as a function of heat treatment.

Journal ArticleDOI
TL;DR: In this paper, a method of obtaining films of aromatic heterocyclic ladder polymers has been found which circumvents casting from high-boiling acidic solvents.
Abstract: A new method of obtaining films of aromatic heterocyclic ladder polymers has been found which circumvents casting from high-boiling acidic solvents. The BBL ladder polymer has been formed into tough, durable films by collecting suspensions of the polymer obtained from acid reprecipitations upon a fritted glass funnel. After drying, the polymer can be removed as film, with thickness dependent upon the amount of material used. Such a film has a tensile strength of 9,600 lb/in.2 as compared to a tensile strength of 16,000 lb/in.2 obtained from the same polymer when cast from methanesulfonic acid solution.

Journal ArticleDOI
TL;DR: In this article, the same consolidation parameters and intimate mixing of residual concentrations of highly active fine-particulate rare-earth oxides to act as grain growth inhibitors were used to obtain nearly theoretically dense bodies with a uniform microstructure and 1 to 1.5 μm grain size.
Abstract: Polycrystalline BaTiO3 prepared from alkoxy-derived high-purity submicron powders was studied. Highly dense bodies with uniform grain size were obtained typically by uniaxial cold-pressing at 3000 psi and isostatic pressing at 30,000 psi followed by sintering at 1300° to 1350°C in air for 0.5 to 1 h. Using the same consolidation parameters and intimate mixing of residual concentrations of highly active fine-particulate rare-earth oxides to act as grain-growth inhibitors, nearly theoretically dense bodies with a uniform microstructure and 1 to 1.5 μm grain size were obtained. Typical microstructures with well-defined 90° and 180° domain patterns characteristic of BaTiO3: were observed. Also, an example of a checkerboard pattern resulting from a 〈111〉 ingrown twin plane in the structure which is independent of the Curie temperature was found. Electrical measurements on the undoped material indicated room-temperature dielectric constant and tan δ values of 5000±500 and 4×10−3, respectively. Very high k values and dissipation factors were observed with the La2O3- and Nd2O3-doped samples.


Journal ArticleDOI
TL;DR: The spin-orbit splittings of the valence and conduction bands of the group-IV semiconductors Si, Ge, and Ge have been obtained using a relativistic orthogonalized plane wave (ROPW) model as mentioned in this paper.
Abstract: The spin-orbit splittings of the valence and conduction bands of the group-IV semiconductors Si, Ge, and $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$, the III-V compounds AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb, and the II-VI compounds ZnS, ZnSe, ZnTe, and CdTe have been obtained at the $\ensuremath{\Gamma}$, $X$, and $L$ symmetry points in the Brillouin zone. The calculations were made using a relativistic orthogonalized plane wave (ROPW) model. The energies presented are differences in eigenvalues of the Dirac Hamiltonian where the exchange correlation potential operator was approximated by the cube root of the electron density with coefficients suggested by Slater and by Kohn, Sham, and Gaspar (KSG). The calculated values are compared with values obtained from experiments and from previous $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}$ calculations. The validity of the two-thirds rule for the ratio of the $L$-point to $\ensuremath{\Gamma}$-point valence-band spin-orbit splitting is examined. The effects of hydrostatic pressure on the spin-orbit splittings are also presented.

Journal ArticleDOI
TL;DR: In this article, the authors derived exact central distributions of the extreme roots of the Wishart and MANOVA matrices and the expressions for these distributions and the associated probability integrals are written as linear combinations of the products of certain double integrals.

Journal ArticleDOI
01 May 1971-Cancer
TL;DR: The results indicate that PTAH‐stainable fibrils in cultured astrocytes are analogous to the “stress fibers” which are a nonspecific finding when present in cultured cells.
Abstract: The ultrastructure of a cloned astrocytoma line which produces a protein unique to the nervous system (S-100 protein) is described. The cells have features that are consistent with an origin from neoplastic astrocytes. They are characterized by a sparsity of organelles and the presence of many fine filaments in their cytoplasm. Two classes of filaments are present. One type is 90 to 100 A in diameter filaments that frequently appear hollow, are gently curved, can be followed for long distances in thin sections, and are arranged in loose fascicles. These filaments are similar to the cytoplasmic filaments in normal and neoplastic astrocytes in vivo but are more loosely arrayed in TC-158 cells than in normal astrocytes. The other type is 70 to 75 A filaments that are uniformly electron dense, straight, can only be followed for short distances in sections, and are arranged in compact bundles. These filaments are without counterpart in normal or neoplastic astrocytes in vivo although they are frequently seen in cultured cells from diverse origins (so-called “stress fibers”). In TC-158 cells examined with the light microscope, PTAH-stainable fibrils are present that mimic the distribution of the fine bundles of 70 to 75 A filaments seen in the electron microscope. We suggest that the PTAH-stainable fibrils and bundles of 70 to 75 A filaments share a common identity in TC-158 astrocytes. Although PTAH-staining fibrils in cultured astrocytes have been called “gliofibrils” in the literature, our results indicate that they are analogous to the “stress fibers” which are a nonspecific finding when present in cultured cells.


Journal ArticleDOI
TL;DR: Tasks involving primarily central neural processes, such as reaction time, monitoring, and pattern recognition, are highly resistant to the effects of vibration, as are other motor capacities.
Abstract: VIBRATION RESEARCH IS REVIEWED FROM THE POINT OF VIEW OF HOW THIS ENVIRONMENTAL STRESS AFFECTS DIFFERENT TYPES OF HUMAN PERFORMANCE CAPABILITIES. THE OSCILLATORY MOTIONS NORMALLY CALLED VIBRATION RANGE FROM 1 - 30 HZ., AND THE MOTION MAY BE EITHER SINUSOIDAL OR RANDOM. IN TERMS OF SUBJECTIVE DISCOMFORT, THE LOWEST TOLERANCE LEVEL FOR VIBRATION OCCURS AT ABOUT 5 HZ., THE FREQUENCY AT WHICH RESONANCE OF LARGE BODY ORGANS IS MOST SEVERE. VISUAL ACUITY IS SEVERELY IMPAIRED BY VIBRATION FREQUENCIES IN THE RANGE OF 10 - 25 HZ. MANUAL TRACKING CAPABILITY IS MOST SERIOUSLY AFFECTED BY VIBRATIONS AT 5 HZ. AND BELOW, AS ARE OTHER MOTOR CAPACITIES. TASKS INVOLVING PRIMARILY CENTRAL NEURAL PROCESSES, SUCH AS REACTION TIME, MONITORING, AND PATTERN RECOGNITION, ARE HIGHLY RESISTANT TO THE EFFECTS OF VIBRATION. /AUTHOR/

Journal ArticleDOI
TL;DR: In this paper, a convenient synthesis for the preparation of various polyfluoroaromatic magnesium compounds through the magnesium-halogen exchange reaction is described, and anomalous instability of the (pentafluorophenyl)magnesium chloride is noted.

Journal ArticleDOI
TL;DR: In this article, transfer matrix methods were used for the analysis of the forced vibrations of cylindrically curved multi-span structures, including shell segments and closed shells stiffened by discrete stringers in the axial direction.

Journal ArticleDOI
TL;DR: In an experiment, 20 seated young adult male subjects moved their right foot as rapidly as possible over distances of 15 cm to circular targets and the direction of these discrote movements had no appreciable effect on the accuracy of motion.
Abstract: The literature pertaining to foot operation of controls is reviewed and a new experiment reported. Published experimental results clarify only some isolated aspects of leg and foot motions. Even the relatively often investigated speed of operating pedals and forces that can be applied to them, were studied under such different experimental conditions that no general statements are possible concerning what pedal can be operated most quickly or forcibly. Opinions about the advantages and dis advantages of hand versus foot operation seem not generally based on experimental findings. In an experiment, 20 seated young adult male subjects moved their right foot as rapidly as possible over distances of 15 cm to circular targets. The direction of these discrote movements had no appreciable effect on the accuracy of motion. Forward motions of the vertical or almost vertical lower leg were slightly faster than backward or lateral motions of the elevated lower leg. All motions could be performed in about 0-1 seconds.