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Effect of Fillers and of Mixing Procedure on the Strength of Plastic Materials

Description: Note presenting a study to prepare a series of molding powders with the use of a given plastic and given fillers in varying proportions and to determine the effect of the differences in composition of the molding powders on certain physical properties of standard test pieces molded from them.
Date: January 1943
Creator: Kynoch, William & Patronsky, L. A.
Partner: UNT Libraries Government Documents Department

Mechanical behavior, properties and reliability of tin-modified lead zirconate titanate.

Description: The influences of temperature and processing conditions (unpoled or poled-depoled) on strength, fracture toughness and the stress-strain behavior of tin-modified lead zirconate titanate (PSZT) were evaluated in four-point bending. PSZT exhibits temperature-dependent non-linear and non-symmetric stress-strain behavior. A consequence of temperature dependent non-linearity is an apparent reduction in the flexural strength of PSZT as temperature increases. At room temperature the average stress in the outer-fiber of bend bars was 84 MPa, whereas, for specimens tested at 120 C the average failure stress was only 64 MPa. The load-carrying capacity, however, does not change with temperature, but the degree of deformation tolerated by PSZT prior to failure increased with temperature.
Date: August 1, 2003
Creator: Watson, Chad Samuel
Partner: UNT Libraries Government Documents Department

Processing and mechanical behavior of Nicalon{reg_sign}/SiC composites with sol-gel derived oxide interfacial coatings

Description: Recent analytical and finite element modeling studies have indicated that low modulus interface materials are desirable for obtaining Nicalon/SiC composites with good toughness. Two oxides, Al titanate and mullite, were chosen on this basis as interface materials. The oxide and C coatings were deposited by sol-gel and CVD, respectively. Nicalon/SiC composites with oxide/C and C/oxide/C interfaces were fabricated and evaluated for flexure strength in the as-processed and oxidized conditions. Composites with C/oxide/C interfaces retained considerable strength and damage-tolerant behavior even after 500 h oxidation at 1000 C in air. The C/oxide/C interface shows promise as a viable oxidation-resistant interface alternative to C or BN interfaces.
Date: October 1, 1996
Creator: Shanmugham, S. & Liaw, P.K.
Partner: UNT Libraries Government Documents Department

Dynamic response of flexible retaining walls

Description: Making use of an extension of a recently proposed, relatively simple, approximate method of analysis, a critical evaluation is made of the response to horizontal ground shaking of flexible walls retaining a uniform, linear, viscoelastic stratum of constant thickness and semiinfinite extent in the horizontal direction. Both cantilever and top-supported walls are examined. Following a detailed description of the method and of its rate of convergence, comprehensive numerical solutions are presented that elucidate the action of the system and the effects of the various parameters involved. The parameters varied include the flexibility of the wall, the condition of top support, and the characteristics of the ground motion. The effects of both harmonic base motions and an actual earthquake record are examined. Special attention is paid to the effects of long-period, effectively static excitations. A maximum dynamic response is then expressed as the product of the corresponding static response and an appropriate amplification or deamplification factor. The response quantities examined include the displacements of the wall relative to the moving base, the dynamic wall pressures, and the total wall force, base shear and base moment.
Date: January 1, 1997
Creator: Younan, A.H.; Veletsos, A.S. & Bandyopadhyay, K.
Partner: UNT Libraries Government Documents Department

Design and implementation of an x-ray strain measurement capability using a rotating anode machine

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Residual stresses close to the surface can improve the reliability and lifetime of parts for technological applications. X-ray diffraction plays a significant role in gaining an exact knowledge of the stresses at the surface and their depth distribution. An x-ray capability at Los Alamos is key to developing and maintaining industrial collaborations in strain effects. To achieve this goal, the authors implemented a residual strain measuring station on the rotating anode x-ray instrument at the Lujan Center. This capability has been used to investigate residual strains in heat treated automotive components, machining effects on titanium alloys, resistance welded steel joints, titanium matrix fiber reinforced composites, ceramic matrix composites, thin films, and ceramic coatings. The overall objective is to combine both x-ray and neutron diffraction measurements with numerical models (e.g., finite element calculations).
Date: December 31, 1998
Creator: Roberts, J.A.; Rangaswamy, P.; Lujan, M. Jr. & Bourke, M.A.M.
Partner: UNT Libraries Government Documents Department

Effects of surface grinding conditions on the reciprocating friction and wear behavior of silicon nitride

Description: The relationship between two significantly different surface grinding conditions and the reciprocating ball-on-flat friction and wear behavior of a high-quality, structural silicon nitride material (GS-44) was investigated. The slider materials were silicon nitride NBD 200 and 440C stainless steel. Two machining conditions were selected based on extensive machining and flexural strength test data obtained under the auspices of an international, interlaboratory grinding study. The condition categorized as {open_quotes}low strength{close_quote} grinding used a coarse 80 grit wheel and produced low flexure strength due to machining-induced flaws in the surface. The other condition, regarded as {open_quotes}high strength grinding,{close_quotes} utilized a 320 grit wheel and produced a flexural strength nearly 70% greater. Grinding wheel surface speeds were 35 and 47 m/s. Reciprocating sliding tests were conducted following the procedure described in a newly-published ASTM standard (G- 133) for linearly-reciprocating wear. Tests were performed in directions both parallel and perpendicular to the grinding marks (lay) using a 25 N load, 5 Hz reciprocating frequency, 10 mm stroke length, and 100 m of sliding at room temperature. The effects of sliding direction relative to the lay were more pronounced for stainless steel than for silicon nitride sliders. The wear of stainless steel was less than the wear of the silicon nitride slider materials because of the formation of transfer particles which covered the sharp edges of the silicon nitride grinding grooves and reduced abrasive contact. The wear of the GS-44 material was much greater for the silicon nitride sliders than for the stainless steel sliders. The causes for the effects of surface-grinding severity and sliding direction on friction and wear of GS-44 and its counterface materials are explained.
Date: December 1997
Creator: Blau, P. J.; Martin, R. L. & Zanoria, E. S.
Partner: UNT Libraries Government Documents Department

Gas pressure sintering of silicon nitride to optimize fracture toughness

Description: Gas-pressure sintering (GPS) can be used to densify silicon nitride containing a wide variety of sintering additives. Parameters affecting the sintering behavior include densification temperature, densification time, grain growth temperature, grain growth time and heating rates. The Si{sub 3}N{sub 4}-6% Y{sub 2}O{sub 3}-2% A1{sub 2}O{sub 3} samples sintered to high densities at all conditions used in the present study, whereas the Si{sub 3}N{sub 4}-Sr{sub 2}La{sub 4}Yb{sub 4}(SiO{sub 4}){sub 6}O{sub 2} samples required the highest temperatures and longest times to achieve densities {ge}98 % T. D. The main effect on the fracture toughness for Si{sub 3}N{sub 4}-6% Y{sub 2}O{sub 3}-2% A1{sub 2}O{sub 3} samples was the use of a lower densification temperature, which was 1900C in the present study. For the Si{sub 3}N{sub 4}-Sr{sub 2}La{sub 4}Yb{sub 4}SiO4{sub 4}){sub 6}O{sub 2} composition, fracture toughness was sensitive to and improved by a slower heating rate (10c/min), a lower densification temperature (1900`), a higher grain growth temperature (2000C), and a longer grain growth time (2 h).
Date: June 1, 1995
Creator: Tiegs, T.N.; Nunn, S.D.; Beavers, T.M.; Menchhofer, P.A.; Barker, D.L. & Coffey, D.W.
Partner: UNT Libraries Government Documents Department

Using Designed Residual Stress Profiles to Produce Flaw-Tolerant Glass

Description: A processing approach has been identified and reduced to practice in which a residual stress profile can be designed such that cracks in a brittle material are arrested or grow in a stable fashion. In the procedure, cracks in the body encounter an increase in the magnitude of residual compression as the crack propagates. If correctly designed, the process increases strength, significantly decreases strength variability and gives rise to multiple cracking. This approach is demonstrated for an ion-exchanged silicate glass using four-point and biaxial flexure strength testing. Optical microscopy was used to study the morphology and development of the multiple cracking that precedes the final failure.
Date: September 2, 1999
Partner: UNT Libraries Government Documents Department

The Effect of Excimer Laser Treatment on the Surface Roughness and Fracture Strength of Alumina Substrates

Description: The microelectronics industry requires alumina substrates with exceptionally smooth surfaces and few surface defects to allow successful deposition of metallic films for reliable electronic performance. Irradiation by a 248-nm wavelength excimer laser beam (KrF) at a fluence of 125 mJ/mm{sup 2} and at various angles of incidence is shown to significantly reduce the surface roughness of alumina substrates. However, irradiation also creates a fine particulate deposit of alumina that only partially adheres to the substrate and impedes deposition of metal films. Annealing in air between 1350 C and 1450 C was found to remove the particles by sintering. As-received material showed surface roughness average (R{sub a}) mean values of 457 nm, which was reduced to 60 nm (mean) following irradiation and 71 nm (mean) following irradiation and annealing at 1350 C. Irradiation also produced a decrease in the number and severity of surface defects. The flexural strength and Weibull modulus were both increased by laser irradiation and thermal treatment. Flexural strength went from an as-received value of 450 MPa to 560 MPa following irradiation/sintering, measured at 10% probability of failure. The Weibull modulus was increased from the as-received value of about 9, to about 13 following irradiation/sintering. It was concluded that irradiation at an angle of incidence of 60{degree} from perpendicular was most effective in producing a low surface roughness.
Date: May 13, 1998
Creator: Smoot, J. E.
Partner: UNT Libraries Government Documents Department

Elastic properties of large tow 2-D braided composites by numerical and analytical methods

Description: The homogenized extensional and flexural properties of a large tow, two- dimensional, braided carbon-fiber composite lamina were evaluated using analytical and numerical methods. The plane-stress composite lamina was assumed to be periodic in its plane and was modeled with a single representative volume element. The homogenized elastic properties were analytically estimated using beam-theory concepts and upper and lower bound techniques as well as using three-dimensional finite element analyses. The homogenized extensional and bending lamina properties are, in general, distinct properties and are not simply related to each other as in monolithic beams and plates or in composites with very fine and highly periodic microstructures. The importance and cause of distinct homogenized extensional and flexural elastic properties is briefly discussed.
Date: September 1, 1998
Creator: Nguyen, T D & Zywicz, E
Partner: UNT Libraries Government Documents Department

Effect of panel alignment and surface finish on bond strength

Description: The flexural strength of bonded acrylic is tested as a function of panel alignment and bond surface finish. Bond strength was shown to be highly dependent on both parameters with only a narrow range of values yielding a high strength bond. This study was performed for the heavy water-containing acrylic vessel for the Sudbury Neutrino Observatory detector.
Date: October 1, 1991
Creator: Wouters, J. M.; Doe, P. J. & Baker, W. E.
Partner: UNT Libraries Government Documents Department

Oxygen Transport Ceramic Membranes

Description: In this quarter a systematic analysis on the decomposition behavior of the OTM membranes at air and nitrogen were initiated to understand the structural and stoichiometric changes associated with elevated temperatures. Evaluation of the flexural strengths using 4-point bend test was also started for the dual phase membranes. Initial results on the synthesis of dual phase composite materials have been obtained. The measurements have focused on the compatibility of mixed conductors with the pure ionic conductors yttria stabilized zirconia (YSZ) and gadolinium doped ceria (GDC). The initial results obtained for three different mixed conductors suggest that (GDC) is the better choice. A new membrane permeation system has been designed and tested and sintering studies of biphasic systems are in progress.
Date: May 1, 2006
Creator: Bandopadhyay, S.; Nithyanantham, T.; Zhou, X.-D; Sin, Y-W.; Anderson, H.U.; Jacobson, Alan et al.
Partner: UNT Libraries Government Documents Department

Effects of thermomechanical processing on the resulting mechanical properties of 6101 aluminum foam

Description: Porous materials represent a tremendous weight savings for light-weight structural applications. The fabrication path can play a critical role in the resulting properties. High porosity aluminum was fabricated in a number of ways. The starting material was a cast 6101 aluminum that had a relative density of 9.8%. The cast aluminum block was compressed by uniaxial, biaxial, and triaxial densification. Uniaxial compression was done at room temperature and 200 C. Biaxial compression was achieved by unidirectional rolling at room temperature and 200 C. Triaxial compression was done by cold isostatic pressing at 3.4, 6.7, and 34 MPa (0.5, 1.0, and 5.0 ksi). Metallography and mechanical test specimens were machines from the processed bars. The mechanical properties showed that the relative yield strength depended both on relative density and processing temperature.
Date: December 1, 1998
Creator: Margevicius, R.W.; Stanek, P.W. & Jacobson, L.A.
Partner: UNT Libraries Government Documents Department

Summary and evaluation of low-velocity impact tests of solid steel billet onto concrete pads

Description: Spent fuel storage casks intended for use at independent spent fuel storage installations are evaluated during the application and review process for low-velocity impacts representative of possible handling accidents. In the past, the analyses involved in these evaluations have assumed that the casks dropped or tipped onto an unyielding surface - a conservative and simplifying assumption. Since 10 CFR Part 72, the regulation imposed by the Nuclear Regulatory Commission (NRC), does not require this assumption, applicants are currently seeking a more realistic model for the analyses to predict the effect of a cask dropping onto a reinforced concrete pad, including energy absorbing aspects such as cracking and flexure. To develop data suitable for benchmarking these analyses, the NRC has conducted several series of drop-test studies of a solid steel billet and of a near-full-scale empty cask. This report contains a summary and evaluation of all steel billet testing conducted by Sandia National Laboratories and Lawrence Livermore National Laboratory. A series of finite element analyses of the billet testing is described and benchmarked against the test data. A method to apply the benchmarked finite element model of the soil and concrete pad to an analysis of a full-size storage cask is provided. In addition, an application to a {open_quotes}generic{close_quotes} full-size cask is presented for side and end drops, and tipover events. The primary purpose of this report is to provide applicants for an NRC license under 10 CFR Part 72 with a method for evaluating storage casks for low-velocity impact conditions.
Date: February 1, 1998
Creator: Witte, M.C.; Hovingh, W.J.; Mok, G.C.; Murty, S.S.; Chen, T.F. & Fischer, L.E.
Partner: UNT Libraries Government Documents Department

The fracture strength of plate and tubular forms of monolithic silicon carbide (SiC) produced by chemical vapor deposition (CVD)

Description: The fracture strength of silicon carbide (SiC) plate deposits produced by Chemical Vapor Deposition (CVD) was determined from room-temperature to 1500 C using a standard 4-point flexural test method (ASTM Cl 161). CVD SiC materials produced by two different manufacturers are shown to have only slightly different flexural strength values, which appear to result from differences in microstructure. Although CVD deposition of SiC results in a textured grain structure, the flexural strength was shown to be independent of the CVD growth direction. The orientation of machining marks was shown to have the most significant influence on flexural strength, as expected. The fracture strength of tubular forms of SiC produced by CVD deposition directly onto a mandrel was comparable to flexural bars machined from a plate deposit. The tubular (o-ring) specimens were much smaller in volume than the flexural bars, and higher strength values are predicted based on Weibull statistical theory for the o-ring specimens. Differences in microstructure between the plate deposits and deposits made on a mandrel result in different flaw distributions and comparable strength values for the flexural bar and o-ring specimens. These results indicate that compression testing of o-rings provides a more accurate strength measurement for tubular product forms of SiC due to more representative flaw distributions.
Date: December 1, 2000
Creator: Cockeram, B.V.
Partner: UNT Libraries Government Documents Department

Gas pressure sintering of silicon nitride

Description: The Cooperative Research and Development Agreement (CRADA) with Materials and Electrochemical Research Corp. (MER) examined materials made with different starting {alpha}/{beta}Si{sub 3}N{sub 4} ratios and with the addition of sintering aids as coatings instead of powders. The samples were sintered by GPS using optimum densification parameters developed for high toughness materials in the ORNL program. High densities were achieved for all of the samples fabricated at ORNL and containing up to 50% {beta}-Si{sub 3}N{sub 4}. The effect of the type of {beta}-Si{sub 3}N{sub 4} seed on fluxural strength and fracture toughness indicated seeds fabricated by the reaction of either yttrium nitrate or Y{sub 2}O{sub 3} powder and Ube E-10 Si{sub 3}N{sub 4} developed materials with the highest flexural strength. However, the fracture toughness of these materials (at the 25% addition level) showed no improvement over the baseline composition having no {beta}-seed addition. The effects of the {beta}-seed content on flexural strength and fracture toughness were mixed. Higher toughnesses were observed with 50% {beta}-seed additions, while the other additive levels showed no consistent improvements.
Date: December 1998
Creator: Tiegs, T. N.; Leaskey, L. & Loutfy, R. O.
Partner: UNT Libraries Government Documents Department

Recent progress in ceramic joining

Description: Both fundamental and practical aspects of ceramic joining are understood well enough for many, if not most, applications requiring moderate strengths at room temperature. This paper argues that the two greatest needs in ceramic joining are for techniques to join buried interfaces by selective heating, and methods for joining ceramics for use at temperatures of 800 to 1,200 C. Heating with microwave radiation or with high-energy electron beams has been used to join buried ceramic interfaces, for example SiC to SiC. Joints with varying levels of strength at temperatures of 600 to 1,000 C have been made using four techniques: (1) transient liquid phase bonding; (2) joining with refractory braze alloys; (3) joining with refractory glass compositions; and (4) joining using preceramic polymers. Joint strengths as high as 550 MPa at 1,000 C have been reported for silicon nitride-silicon nitride bonds tested in four-point flexure.
Date: September 1, 1998
Creator: Loehman, R.E.
Partner: UNT Libraries Government Documents Department

Processing and properties of molybdenum silicide intermetallics containing boron

Description: The processing and mechanical properties of Mo-Si-B intermetallic alloys with compositions Mo-26.7Si-7.3B and Mo-12Si-8.5B (at.%) were investigated. The first alloy consisted of the phases Mo{sub 3}Si, Mo{sub 5}Si{sub 3} (T1) and Mo{sub 5}SiB{sub 2} (T2). Attempts to extrude castings of this alloy at 1700 or 1800 C were not successful. Hot isostatic pressing of elemental powders was more promising and room temperature flexure strengths on the order of 200 MPa were reached. The second alloy with the composition Mo-12Si-8.5B could be readily cast and consisted of {alpha}-Mo inclusion in a brittle matrix of Mo{sub 3}Si and T2. A heat treatment of 1 day at 1600C in vacuum improved the room temperature strength and fracture toughness. Values on the order of 500 MPa and 10 MPa m{sup 1/2}, respectively, were obtained. Consistent with ductile phase toughening, limited plastic deformation as well as debonding of the {alpha}-Mo inclusions were seen on fracture surfaces.
Date: November 1, 1998
Creator: Schneibel, J.H.; Liu, C.T.; Heatherly, L. Jr. & Carmichael, C.A.
Partner: UNT Libraries Government Documents Department

Final report for the ORNL/3M CRADA No. ORNL91-0061 for the period January 1, 1992--December 31, 1992

Description: Oxide fiber-reinforced silicon carbide matrix composites were fabricated employing the forced-flow, thermal gradient chemical vapor infiltration (FCVI) process. Composites using Nextel{trademark} fibers of varying composition were prepared to investigate the effectiveness of each Nextel{trademark} fiber as a reinforcement for the given matrix. A carbon interface coating was used for the baseline materials, however, alternate interlayers with improved oxidation resistance were also explored. Room-temperature flexure strengths of as-fabricated composites and specimens heated in air at 1273 K were measured and compared to results for other SiC-matrix composites.
Date: October 1, 1995
Creator: Weaver, B.L.; Besmann, T.M. & Lowden, R.A.
Partner: UNT Libraries Government Documents Department

Controlled densification of mullite for composite applications.

Description: As part of an effort to fabricate oxide-based fibrous monolithic ceramics, sintering of mullite has been examined. The effects of Y{sub 2}O{sub 3} additions on sinterability of sol-gel-derived mullite and on the resulting microstructure were evaluated over a range of compositions, sintering times, and temperatures. Electron microscopy, X-ray diffraction, differential thermal analysis, and density measurements indicated that the Y{sub 2}O{sub 3} additions promoted densification through formation of a Y-Si-Al-O liquid phase. This phase tended to solidify as a glass during normal processing, but could be crystallized by a two-step annealing process at 1300 and 1200 C. The four-point flexural strengths of mullite and mullite-5 Wt.% Y{sub 2}O{sub 3} were also examined.
Date: May 19, 1999
Creator: Cruse, T. A.
Partner: UNT Libraries Government Documents Department

Fabrication and characterization of a porous-matrix oxide fibrous monoliths.

Description: We have fabricated unidirectional fibrous monoliths based on dense ZrSiO{sub 4} cells that are surrounded by a porous, weak ZrSiO{sub 4} cell boundary phase. We coextruded a duplex filament, cut it to short lengths, bundled the lengths and packed them into an extruder, and then extruded a new filament. This filament was cut and packed into a bar die to produce test specimens. After heat treatment, the specimens were tested in four-point flexure and examined by scanning electron microscopy. Load-displacement curves were linear to failure, but some evidence of toughening was observed microscopically.
Date: March 2, 1999
Creator: Polzin, B. J.
Partner: UNT Libraries Government Documents Department

Fabrication and characterization of oxide fibrous monoliths produced by coextrusion.

Description: Unidirectional fibrous monoliths (FMs) based on dense, strong ZrSiO{sub 4} cells that were surrounded by a porous, weaker ZrSiO{sub 4} cell-boundary phase were fabricated. A duplex filament was coextruded, sectioned, bundled, and the resulting bundle was extruded to form a new filament. This filament was cut and packed into plate and bar dies to produce FM test specimens. Four-point flexural tests were conducted on the cell material, cell-boundary material, and FMs. After testing, fracture surfaces and cross sections were examined by scanning electron microscopy. The FMs exhibited graceful failure in flexural testing, and the fracture surfaces exhibited clear evidence of crack deflection and delamination.
Date: May 19, 1999
Creator: Polzin, B. J.
Partner: UNT Libraries Government Documents Department

Crystallization of grain boundary phases in silicon nitride with low additive contents by microwave annealing

Description: Microwave annealing of dense Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials showed improvements over conventional heating. Increases in fracture toughness were observed for annealing between 1200--1650C. The high temperature strength was related to the residual {alpha}-Si{sub 3}N{sub 4} content which is indicative of a finer average grain size in the specimens. The high temperature dynamic fatigue showed increased stress to failure for specimens microwave annealed between 1400--1550C for periods >5 h. Silicon nitrides with different sintering additives would require different conditions for optimum crystallization. While there were some observed property improvements, they were not so dramatic to justify abandoning conventional over microwave heating. The Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials used in the study were developed for elevated temperature use and already posses excellent good high temperature strength, fatigue resistance and creep properties. This is due to the very refractory nature of the grain boundary phases and the small quantity of secondary phase present. However, microwave annealing of these materials may be necessary in applications where the maximum in fracture toughness and fatigue resistance are required and thus justifies its use.
Date: June 1, 1993
Creator: Tiegs, T. N.; Ploetz, K. L.; Kiggans, J. O. & Yeckley, R. L.
Partner: UNT Libraries Government Documents Department

Effect of fiber fabric orientation on the monotonic and fatigue behavior of a continuous fiber ceramic composite

Description: The monotonic fast fracture and fatigue behavior of a Nextel{trademark} 312 reinforced SiC matrix composite was investigated. Effect of fabric orientation with respect to the loading axis on the monotonic and fatigue behavior of the composite was examined. Two geometries were investigated: transverse, where fiber fabric is perpendicular to loading direction; and edge-on where the fabric is parallel to the loading axis. The edge-on geometry showed higher flexure strengths than the transverse orientation. The different deformation mechanisms between the edge-on and transverse orientations were due to strong in-plane shearing of the fiber fabric and weak interlaminar shear of the plies, respectively. In cyclic fatigue, stress versus cycles (S-N) curves showed high fatigue endurance limits in both orientations, although the transverse orientation survived more cycles than the edge-on orientation at stresses slightly above the endurance limit.
Date: September 1, 1994
Creator: Chawla, N.; Liaw, P. K.; Lara-Curzio, E.; Lowden, R. A. & Ferber, M. K.
Partner: UNT Libraries Government Documents Department