Impact Strength Of Glass And Glass Ceramic

Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicatc glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.Mechanical Engineerin

Improved Bar Impact Tests Using A Photonic Doppler Velocimeter

Bar impact tests, using the techniques described elsewhere in this symposium, were used to measure compressive and tensile strengths of borosilicate glass, soda lime glass, and a glass ceramic. The glass ceramic was 25% crystalline spinel, furnished by Corning Inc. There are two measures of compressive strength: the peak stress that can be transmitted in unconfined compression, and the >steady state> strength. For borosilicate glass and soda lime glass, these values were similar, being about 1.8 and 1.5 GPa, respectively. The glass ceramic (25% spinel) was almost 50% stronger. Tensile failure in the glass and glass ceramic takes places via surface flaws, and thus tensile strength is an extrinsic, as opposed to intrinsic property.Mechanical Engineerin

Sand Penetration By High-Speed Projectiles

Tungsten projectiles were shot into sand at velocities between 600 and 2200 m/s. Penetration was maximum at about 775 m/s. Below that velocity, projectiles were apparently stabilized by a fin set. Above that velocity, projectiles were broken by transverse loads. High-speed penetration resulted in comminution of sand particles, reducing their size by about 1000 times.Mechanical Engineerin

X-Ray Tomography To Measure Size Of Fragments From Penetration Of High-Velocity Tungsten Rods

Behind-armor debris that results from tungsten rods penetrating armor steel at 2 km/s was studied by analysis of recovered fragments. Fragment recovery was by means of particle board. Individual fragments were analyzed by x-ray tomography, which provides information for fragment identification, mass, shape, and penetration down to masses of a few milligrams. The experiments were complemented by AUTODYN and EPIC calculations. Fragments were steel or tungsten generated from the channel or from the breakout through the target rear surface. Channel fragment motions were well described by Tate theory. Breakout fragments had velocities from the projectile remnant to the channel velocity, apparently depending on where in the projectile a fragment originated. The fragment size distribution was extremely broad and did not correlate well with simple uniform-fragment-size models.Mechanical Engineerin

A finite element based method for solution of optimal control problems

A temporal finite element based on a mixed form of the Hamiltonian weak principle is presented for optimal control problems. The mixed form of this principle contains both states and costates as primary variables that are expanded in terms of elemental values and simple shape functions. Unlike other variational approaches to optimal control problems, however, time derivatives of the states and costates do not appear in the governing variational equation. Instead, the only quantities whose time derivatives appear therein are virtual states and virtual costates. Also noteworthy among characteristics of the finite element formulation is the fact that in the algebraic equations which contain costates, they appear linearly. Thus, the remaining equations can be solved iteratively without initial guesses for the costates; this reduces the size of the problem by about a factor of two. Numerical results are presented herein for an elementary trajectory optimization problem which show very good agreement with the exact solution along with excellent computational efficiency and self-starting capability. The goal is to evaluate the feasibility of this approach for real-time guidance applications. To this end, a simplified two-stage, four-state model for an advanced launch vehicle application is presented which is suitable for finite element solution

Sobre las facies de ostrácodos del Carbonífero superopr y su uso para correlaciones en las Cuencas Hulleras

Desde el año 1964 se está realizando una investigación sisteiziática sobre la presencia de ostrácodos en el nordeste de la Cuenca Hullera de Asturias. Partes de este trabajo ya se publicaron en "Leidse Geologische Meddelingten" y en "Notas y Comunicaciones del Instituto Geológico y Minero de España". Resultó posible seguir ciertos horizorites fosilíferosde una tniiia n otra y así correlacionar capas de carbón sobre distancias a veces bastante estimables. El interés económico que tiene esto último está bien claro.El motivo principal de haber escogido los ostrácodos entre otras clases de fósiles para estos fines es el siguiente: Los ostrácodos por su pequeñez (raramente más de dos milímetros), están normalmente mejor conservados que los macrofósiles, puesto que éstos con frecuencia son afectados, ya sea por la diagénesis de los sedimentos o por los movimientos tectótnicos que influyen en la roca. Además se encuentran los ostrácodos en relativa abundancia en los estratos carboníferos, bien sea en sedimentos marinos, fluviales o salobres. Otras clases de  microfósiles, como por ejemplo los foraminíferos, están limitados a los niveles marinos y únicamente en las calizas abundan

Optimal guidance law development for an advanced launch system

The proposed investigation on a Matched Asymptotic Expansion (MAE) method was carried out. It was concluded that the method of MAE is not applicable to launch vehicle ascent trajectory optimization due to a lack of a suitable stretched variable. More work was done on the earlier regular perturbation approach using a piecewise analytic zeroth order solution to generate a more accurate approximation. In the meantime, a singular perturbation approach using manifold theory is also under current investigation. Work on a general computational environment based on the use of MACSYMA and the weak Hamiltonian finite element method continued during this period. This methodology is capable of the solution of a large class of optimal control problems

The effect of magnetic pinch pressure on boron nitride, cadmium sulfide, graphite, silica glass, and some other materials.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1970.Bibliography: leaves 129-136.Sc.D