Showing papers on "Ultimate tensile strength published in 1995"

Shear vs. Tensile Bond Strength of Resin Composite Bonded to Ceramic

Abstract: Since the mode of failure of resin composites bonded to ceramics has frequently been reported to be cohesive fracture of either ceramic or resin composite rather than separation at the adhesive interface, this study was designed to question the validity of shear bond strength tests. The reasons for such a failure mode are identified and an alternative tensile bond strength test evaluated. Three configurations (A, conventional; B, reversed; and C, all composite) of the cylinder-on-disc design were produced for shear bond strength testing. Two-dimensional finite element stress analysis (FEA) was carried out to determine qualitatively the stress distribution for the three configurations. A tensile bond strength test was designed and used to evaluate two ceramic repair systems, one using hydrofluoric acid (HF) and the other acidulated phosphate fluoride (APF). Results from the shear bond strength tests and FEA showed that this particular test has as its inherent feature the measurement of the strength of the ...

Compressive and tensile failure of inclined well bores and determination of in situ stress and rock strength

Abstract: In this paper we investigate the occurrence of compressive and tensile failures of arbitrarily inclined well bores under a wide variety of stress conditions. The principal assumptions in this analysis are that the rock is isotropic and that it deforms elastically to the point of failure. As has been shown by previous investigators, for a given stress state and well bore orientation, it is straightforward to predict the orientation of the failures around the well bore as well as whether failure is likely to occur depending on such parameters as rock strength and borehole fluid pressure. However, as the stress state is almost never known in situ, we demonstrate how observations of compressive and tensile wall failures in inclined holes can be used to constrain in situ stress orientations and magnitudes if there are independent data on the magnitude of the least principal stress from either leak-off or microfrac tests and on the formation pore pressure. We further demonstrate how once the stress state is determined, it is possible to assess both an upper bound on the effective in situ rock strength and the degree to which increasing the borehole fluid pressure (or mud weight) can reduce the likelihood of borehole failure. Through application of this methodology to an inclined well bore in an area of complex faulting in the Gulf of Mexico, we illustrate how it is possible to utilize observations of borehole failures to determine the magnitude and orientation of the stress tensor in areas such as offshore sedimentary basins where drilling inclined well bores is quite common.

Bonding to glass infiltrated alumina ceramic: Adhesive methods and their durability

Abstract: Resin bonding to a glass-infiltrated aluminum oxide ceramic (In-Ceram) cannot be achieved by the methods commonly used for conventional silica-based dental caramics. This study evaluated the durability of alternative methods of adhesive bonding to In-Ceram ceramic. The tensile bond strength of six bonding systems to In-Ceram ceramic was tested after up to 150 days of storage in isotonic artificial saliva solution and theramal cycling. Sandblasting alone or additional use of a silane did not result in a durable bond of a conventional BIS-GMA composite resin to In-Ceram ceramic. A durable bond to In-Ceram ceramic was achieved with a combination of tribochemical silica coating and conventional BIS-GMA composite resin or with the combination of sandblasting and a composite resin modified with a phosphate monomer. These two chemomechanical bonding methods appeared suitable for clinical bonding of In-Ceram ceramic restorations. A delayed degradation in bond strength was recorded for the combination of thermal silica coating and a conventional BIS-GMA composite resin; no reduction was found after 30 days, but there was a pronounced decrease after 150 days. This degradation indicated that extended storage in a wet environment was needed in laboratory tests to evaluate the durability of chemical bonds.

Composition factors affecting the water vapor permeability and tensile properties of hydrophilic zein films

Abstract: Transparent unplasticized zein films were prepared in aqueous ethanol or acetone. Tensile properties indicated that films prepared in acetone were stronger but less flexible than those prepared in ethanol. Both types of films, however, were too brittle for most applications. Films containing a glycerol:poly(propylene glycol) ratio of 1:3 exhibited elongation values almost fifty times greater than glycerol-plasticized films. Incorporation of cross-linking agents into zein films resulted in approximately a 2−3-fold increase in tensile strength values. Water vapor barrier properties were best for unplasticized zein films cross-linked with 20% polymeric dialdehyde starch. Incorporation of plasticizer into zein films resulted in an almost doubling in water vapor permeability values. Keywords: Hydrophilic; film; zein; tensile properties; plasticizer; cross-linking agents; water vapor permeability

Effects of Treatment and Storage Conditions on Ceramic/Composite Bond Strength

Abstract: During the past few years, the interest in using ceramic inlays and veneers has increased. New materials and methods have been introduced to bond these restorations to resinous materials. Since our knowledge of how to optimize such bonding is limited, the objective of this study was to test the hypothesis that various surface treatment variables and combinations of these variables affect the strength of the ceramic/composite interphase of ceramic inlays differently. The influences of material composition, surface-roughening method, silane treatment, silane heat treatment, and storage condition on bond strength were investigated. Three ceramics (Dicor, Mirage, Vitabloc), three surface-roughening methods (etching, sandblasting, grinding), three silane treatments (gamma-methacryloxypropyltrimethoxysilane [MPS], MPS+paratoluidine, vinyltrichlorosilane), two heat treatments (20 degrees C for 60 s, 100 degrees C for 60 s), and two storage conditions (24-hour dry, one yr in water at 37 degrees C) were studied. For each of the 108 combinations, five specimens were tested. Ceramic cylinders were treated according to group assignment and bonded to blocks of the same ceramic material with a dual-cured resin. The shear bond strength was determined, and the experimental factors were evaluated by analysis of variance. The results showed that surface-roughening method had the strongest effect on bond strength, while ceramic selection had the least significant effect. Of the surface-roughening methods, etching was associated with higher bond strength values than either sandblasting or grinding.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of microstructure on the deformation and fracture of γ-TiAl alloys

Abstract: Deformation and fracture behavior of two-phase γ-TiAl alloys were investigated under monotonic tension loading conditions for duplex and lamellar microstructural forms. The effects of microstructure on tensile properties and deformation-fracture behavior are analyzed for deformation temperatures below and above the brittle-ductile transition. The crack initiation toughness and associated strains near the crack tip are used to explain the inverse relationship between ductility and toughness observed at room temperature. Fracture resistance behavior and toughening mechanisms at room temperature are explained in terms of microstructure and deformation anisotropy. The competition between the effects of grain size and lamellar spacing or tensile and toughness properties is discussed.

Limits on strength and deformation properties of jointed basaltic rock masses

Abstract: A study of strength and deformation measurements for basaltic rocks, along with consideration of the influence of fracturing using a rock mass classification system, documents the range of brittle response for basaltic rock masses. Although basalts vary widely in composition and other physical factors, many of the properties of a basaltic rock mass appear to vary within a factor of about 10. Typical values of strength parameters for intact basalt at ambient temperature (20°C) and negligible confining pressure are Young's modulus, 78±19 GPa; Poisson's ratio, 0.25±0.05; tensile strength, −14.5±3.3 MPa; unconfined compressive strength, 266±98 MPa; and conhesion, 66 MPa. Corresponding values for a basaltic rock mass that incorporate the weakening effects of scale are deformation modulus, 10–40 GPa; Poisson's ratio, 0.3; tensile strength, −0.1 to −2.5 MPa; uniaxial compressive strength, 10–90 MPa; and cohesion, 0.6–6 MPa. A measured deformation modulus for ambient pressure in the vertical direction, 20 GPa, is 1.5–3 times larger than that in the horizontal directions, 13.5 and 6.5 GPa, reflecting strength anisotropy due to column or block geometry for one particular basalt. Values of tensile and cohesive strength for the basaltic rock mass are generally one to two orders of magnitude lower than corresponding values for intact basalt. The shear strength of joints appears to vary considerably from flow to flow.

Relative flexural strength of six new ceramic materials.

Abstract: The flexural strength of six recently introduced dental ceramic materials was measured using a three-point-bend test. Conventional feldspathic porcelain and soda-lime glass were used as controls. All six of the new materials had significantly greater breaking strength than the controls. The alumina-based crystalline-reinforced materials exhibited the highest breaking strengths. The silica-based crystalline-reinforced materials resulted in ceramic materials with more moderate strength but still with significantly greater strength than the controls. Scanning electron microscopic analysis of the fractured surfaces indicated crack deflection appeared to be the principal strengthening mechanism in the highly crystalline materials.

Mechanical properties of the binary titanium-zirconium alloys and their potential for biomedical materials

Abstract: Mechanical properties of titanium-zirconium binary alloys were investigated in order to reveal their possible use for new biomedical materials and to collect useful data for alloy design through a hardness test, a tensile test, and optical microscopy. The hardness of the alloy containing 50% zirconium was approximately 2.5 times as large as the hardness of pure titanium and pure zirconium. Tensile tests showed a similar tendency. No changes between hardness of as cast specimens and as homogenized specimens were observed, nor were changes in microstructures noted. Comparisons between the Ti-6Al-4V alloy and the Ti-Zr-6Al-4V alloy indicated that a titanium-zirconium alloy could provide a base material for a new biomedical alloy. From these results, it was concluded that new alloys for biomedical materials should be designed as titanium-zirconium base alloys. © 1995 John Wiley & Sons, Inc.

Full strength compacts by extrusion of glassy metal powder at the supercooled liquid state

Abstract: We report the production of full strength compacts of metallic glass by warm extrusion of powders at the supercooled liquid state just above the glass transition temperature. The alloy used was Zr65Al10Ni10Cu15 (at. %) which has the lowest viscosity among Zr‐based metallic glasses with large supercooled liquid region. The tensile strength and Young’s modulus of the glassy powder compacts were 1520 MPa and 80 GPa, respectively, which are similar to that obtained in the as‐cast bulk alloy and melt‐spun ribbon. This opens up possibilities of producing high strength amorphous alloys with complex shapes.

Estimation of ideal mechanical strength and critical porosity of calcium phosphate cement.

Abstract: The ideal mechanical strength and critical porosity of calcium phosphate cement (CPC) were estimated to help determine ways to improve its properties. CPC at various porosities was made by packing CPC paste, at various powder-to-liquid (P/L) ratios (2.0-6.0), into a mold under various pressures (0-173 MPa). The mechanical strength of CPC, in terms of diametral tensile strength (DTS), increased with decreases in porosity. Intercrystalline fracture was observed in specimens made without the application of pressure, while fracture within the crystals increased with the packing pressure. These observations support the application of the relationship between DTS and porosity in fractographic equations. The ideal wet DTS and critical porosity of CPC were estimated to be 102 MPa and 63%, respectively. The minimum porosity of the currently used CPC was approximately 26-28%, even when it was packed under 173 MPa, and the maximum DTS value was thus approximately 13-14 MPa. Because reducing the porosity of currently used CPC would be difficult, we conclude that in CPC-related research, we should focus on ways in which to accelerate bone-replacing behavior, in addition to improving the mechanical strength of CPC.

Preparation of Bulky Amorphous Zr–Al–Co–Ni–Cu Alloys by Copper Mold Casting and Their Thermal and Mechanical Properties

Abstract: Bulky amorphous alloys were found to form in Zr-Al-M (M=Co, Ni, Cu) systems by arc melting on a copper hearth. The largest thickness for glass formation is 6. 1 mm for Zr 60 Al 10 Co 3 Ni 9 Cu 18 , 6.8 mm for Zr 60 Al 15 Co 5 Ni 15 Cu 5 and 6.2 mm for Zr 55 Al 20 Co 17.5 Ni 2.5 Cu 5 . The optimum composition for glass-forming ability shifts from the Cu-rich side to the Co-rich side through the Ni-rich side with increasing Al content from 10 to 20%. The use of a metallic mold casting process enabled the formation of amorphous cylinders with the largest diameter of 7 mm for the three alloys. The compositional effect for the large glass-forming ability has also been discussed by taking the present data into consideration. The cast amorphous Zr 60 Al 10 Co 3 Ni 9 Cu 18 alloy subjected to tensile testing exhibits distinct serrated flow before final fracture. The generation of the serrated flow is noticed because the alloy has a ductile nature which enables the momentary stop of the shear sliding. The Young's modulus, tensile fracture strength and fracture elongation are 97 GPa, 1510 MPa and 2.0%, respectively. The fracture occurs along the maximum shear plane and the fracture surface consists of a well-developed vein pattern. The size of their veins is about 10 times as large as that for the melt-spun ribbon and hence the shear deformation region occurs in a much wider region for the cast alloy, indicating the necessity of a larger amount of energy up to final fracture. The finding of the amorphous alloys with the large glass-forming ability and the extremely ductile nature is important for the subsequent development of metallic glassy materials.

Fatigue rupture of wallaby tail tendons

Abstract: Wallaby tail tendons fail after repeated application of stresses much lower than would be needed to break them in a single pull. We show that this a fatigue phenomenon, distinct from the creep rupture that occurs after prolonged application of a constant stress. The two phenomena are disctinguished by experiments in which tensile stress is cycled at different frequencies, ranging from 1 to 50 Hz.

Laboratory Investigation of Compacted No-Fines Concrete for Paving Materials

Abstract: In this study the physical and engineering characteristics of various no-fines concrete mixtures are investigated. No-fines concrete mixtures subjected to impact compaction are studied under unconfined compression, indirect tension, and static modulus of elasticity; and the results are interpreted as functions of mixture proportions. The effect of impact-compaction energies, consolidation techniques, mixture proportions, curing types, and testing conditions on physical and engineering properties are presented. The abrasion characteristics and resistance to freezing and thawing of no-fines concrete are also discussed. It was found that the strength of no-fines concrete is strongly related to its mixture proportion and compaction energy. A sealed compressive strength of 20.7 MPa (3,000 psi) can readily be achieved with an aggregate cement ratio of 4.5:1 or less and a minimum compaction energy of 165 J/m 3 (4,303 ft-lb/cu ft). The splitting tensile-compressive relationship followed a pattern similar to that ...

The effect of soldering process variables on the microstructure and mechanical properties of eutectic Sn-Ag/Cu solder joints

Abstract: Fundamental understanding of the relationship among process, microstructure, and mechanical properties is essential to solder alloy design, soldering process development, and joint reliability prediction and optimization. This research focused on the process-structure-property relationship in eutectic Sn-Ag/Cu solder joints. As a Pb-free alternative, eutectic Sn-Ag solder offers enhanced mechanical properties, good wettability on Cu and Cu alloys, and the potential for a broader range of application compared to eutectic Sn-Pb solder. The relationship between soldering process parameters (soldering temperature, reflow time, and cooling rate) and joint microstructure was studied systemati-cally. Microhardness, tensile shear strength, and shear creep strength were measured and the relationship between the joint microstructures and mechani-cal properties was determined. Based on these results, low soldering tempera-tures, fast cooling rates, and short reflow times are suggested for producing joints with the best shear strength, ductility, and creep resistance.

Tensile bond testing of concrete repairs

Abstract: The development and maintenance of a sound band is an essential requirement of a concrete patch repair. Tensile bond tests are increasing in popularity as a means of measuring this adhesive property, both on site for quality control and in the laboratory for materials evaluation. This paper discusses the main issues relevant to tensile bond testing, namely material properties, surface conditions, geometry, loading and the effects of material mismatch. Analytical and experimental work is presented, along with the results of other researchers, with an emphasis on the core pull-off technique. The latter is shown to be a good method for evaluating bond strength provided that appropriate precautions are taken to minimize the influence of flaws and stress concentrations, and that the effects of mismatch in repair and substrate properties (particularly modulus, shrinkage and thermal expansion) are fully understood.

Tensile Properties of Resin-infiltrated Demineralized Human Dentin

Abstract: The ability of adhesive resins to restore the physical properties of demineralized dentin has not been well-documented. The unfilled resins that are used for adhesion have relatively low moduli of elasticity and limited ability to increase dentin stiffness, although they may increase the ultimate tensile strength of dentin. This study tested the hypothesis that resin infiltration of demineralized dentin can restore its tensile properties to those of mineralized dentin. Small (ca. 0.5 mm thick x 0.5 mm wide) specimens of demineralized human dentin were infiltrated with one of five different dentin bonding resins over many hours, to determine how these resins altered the tensile properties of dentin. Tensile stress and strain were measured in these and control (mineralized and demineralized) specimens until their ultimate failure. The results indicate that some adhesive resins, after infiltrating demineralized dentin, can restore and even exceed the ultimate tensile strength of mineralized dentin. These resins increased the modulus of elasticity of resin-infiltrated dentin to values equal to or greater than those of the resins but far below those of mineralized dentin. Although the conditions in this experiment were far removed from the manufacturer's recommendations or clinical practice, the results support the potential of resin infiltration for reinforcing dentin.

Orientation dependence of the pseudoelastic behavior of single crystals of CuAlNi in tension

Abstract: Uniaxial tension experiments were performed on single crystals of Cu-13.95 wt% Al-3.93 wt% Ni. Three specimens were prepared with tension axes in directions that were chosen based on Schmid law calculations using the 96 possible Austenite-Martensite (AM) interface orientations in this alloy. Specimen number one was chosen to have a tensile axis of [2.43,1,0] which results in a very near minimum value for its predicted tension transformation stress. Specimen number two was oriented 15 degrees from [111] direction and has a [1,1,1.73] tensile axis direction. The third specimen has the [111] direction as its tensile axis, which is the direction of maximum tensile transformation stress. A strong relationship is found between the mechanical behavior of the specimens in tension and their observed microstructure. Specimen one exhibits an extremely flat stress plateau during transformation and almost no hysteresis. The microstructure observed in this specimen consists of two nearly perpendicular AM interfaces that interact to form an X-structure that results in a purely uniaxial deformation. This microstructure is completely reversible and seems to present no restriction on the motion of either interface. Specimen two was observed to have only a single AM interface after transformation. This interface appears to preclude the formation of any other interfaces. Specimen three required five times the normal stress of that needed to transform specimen one. This specimen also exhibited a large amount of hysteresis. The microstructure observed consisted of two A M interface systems that meet to form wedges. Because the interfaces must end at the wedge apex, the formation of the wedges resulted in a kinematic coupling between the two AM interface systems. The amount of coupling between the interfaces in the microstructure correlates to the amount of hysteresis observed.

Tensile and Bond Properties of GFRP Reinforcing Bars

Abstract: The bond characteristics of four different types of glass fiber reinforced plastic (GFRP) reinforcing bars with different surface deformations were analyzed in experiments. Local bond stress-slip data, as well as bond stress-radial deformation data, needed for constitutive modeling of the interface mechanics, were obtained for varying levels of confining pressure. In addition to bond stress and slip, radial stress and radial deformation were considered fundamental variables needed to provide for configuration-independent relationships. Each test specimen consisted of a #6 GFRP reinforcing bar embedded in a 76-mm (3-in)-diameter, 102-mm (4-in)-long cracked concrete cylinder subjected to a controlled, constant amount of confining axisymmetric radial pressure. Only 67 mm (2.6 in) of contact was permitted between the bar and concrete. For each reinforcing bar type, bond stress-slip and bond stress-radial deformation relationships were obtained for five levels of confining axisymmetric radial pressure. The researcher found that small surface indentations were sufficient to yield bond strengths comparable to that of steel bars. Effects of deformations on tensile properties were discussed. It was noted that radial pressure is an important parameter that can increase the bond strength threefold.