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Studies on the disbonding initiation of interfacial cracks.

Description: With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization o… more
Date: August 1, 2005
Creator: McAdams, Brian J. (Lehigh University, Bethlehem, PA) & Pearson, Raymond A. (Lehigh University, Bethlehem, PA)
Partner: UNT Libraries Government Documents Department
open access

3-D Experimental Fracture Analysis at High Temperature

Description: T*e, which is an elastic-plastic fracture parameter based on incremental theory of plasticity, was determined numerically and experimentally. The T*e integral of a tunneling crack in 2024-T3 aluminum, three point bend specimen was obtained through a hybrid analysis of moire interferometry and 3-D elastic-plastic finite element analysis. The results were verified by the good agreement between the experimentally and numerically determined T*e on the specimen surface.
Date: September 14, 2001
Creator: Jackson, John H. & Kobayashi, Albert S.
Partner: UNT Libraries Government Documents Department
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Simulating the pervasive fracture and fragmentation of materials and structures using randomly close-packed Voronoi tessellations.

Description: Under extreme loading conditions most often the extent of material and structural fracture is pervasive in the sense that a multitude of cracks are nucleating, propagating in arbitrary directions, coalescing, and branching. Pervasive fracture is a highly nonlinear process involving complex material constitutive behavior, material softening, localization, surface generation, and ubiquitous contact. Two primary applications in which pervasive fracture is encountered are (1) weapons effects on str… more
Date: September 1, 2008
Creator: Bishop, Joseph E.
Partner: UNT Libraries Government Documents Department
open access

Development of experimental verification techniques for non-linear deformation and fracture on the nanometer scale.

Description: This work covers three distinct aspects of deformation and fracture during indentations. In particular, we develop an approach to verification of nanoindentation induced film fracture in hard film/soft substrate systems; we examine the ability to perform these experiments in harsh environments; we investigate the methods by which the resulting deformation from indentation can be quantified and correlated to computational simulations, and we examine the onset of plasticity during indentation tes… more
Date: November 1, 2005
Creator: Moody, Neville Reid & Bahr, David F.
Partner: UNT Libraries Government Documents Department
open access

Ring-On-Ring Tests and Load Capacity of Cladding Glass

Description: Report issued by the National Bureau of Standards over studies conducted on the load capacity of cladding glass. Testing methods are discussed. This report includes tables, photographs, and illustrations.
Date: August 1984
Creator: Simiu, Emil; Reed, Dorothy A.; Yancey, Charles W. C.; Martin, Jonathan W.; Hendrickson, Erik M.; Gonzalez, Armando C. et al.
Partner: UNT Libraries Government Documents Department
open access

Mechanisms for Fatigue of Micron-Scale Silicon StructuralFilms

Description: Although bulk silicon is not susceptible to fatigue,micron-scale silicon is. Several mechanisms have been proposed to explainthis surprising behavior although the issue remains contentious. Here wedescribe published fatigue results for micron-scale thin siliconfilms andfind that in general they display similar trends, in that lower cyclicstresses result in larger number of cycles to failure in stress-lifetimedata. We further show that one of two classes of mechanisms is invariablyproposed to ex… more
Date: November 3, 2006
Creator: Alsem, Daan Hein; Pierron, Olivier N.; Stach, Eric A.; Muhlstein,Christopher L. & Ritchie, Robert O.
Partner: UNT Libraries Government Documents Department
open access

A micromechanical basis for partitioning the evolution of grainbridging in brittle materials

Description: A micromechanical model is developed for grain bridging inmonolithic ceramics. Specifically, bridge formation of a single,non-equiaxed grain spanning adjacent grains is addressed. A cohesive zoneframework enables crack initiation and propagation along grainboundaries. The evolution of the bridge is investigated through avariance in both grain angle and aspect ratio. We propose that thebridging process can be partitioned into five distinct regimes ofresistance: propagate, kink, arrest, stall, an… more
Date: October 9, 2006
Creator: Foulk, J. W., III; Cannon, R. M.; Johnson, G. C.; Klein, P. A. & Ritchie, R. O.
Partner: UNT Libraries Government Documents Department
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Modeling brittle fracture, slip weakening, and variable friction in geomaterials with an embedded strong discontinuity finite element.

Description: Localized shear deformation plays an important role in a number of geotechnical and geological processes. Slope failures, the formation and propagation of faults, cracking in concrete dams, and shear fractures in subsiding hydrocarbon reservoirs are examples of important effects of shear localization. Traditional engineering analyses of these phenomena, such as limit equilibrium techniques, make certain assumptions on the shape of the failure surface as well as other simplifications. While thes… more
Date: October 1, 2006
Creator: Regueiro, Richard A. (University of Colorado, Boulder, CO); Borja, R. I. (Stanford University, Stanford, CA) & Foster, C. D. (Stanford University, Stanford, CA)
Partner: UNT Libraries Government Documents Department
open access

CONSTRAINT EFFECT IN FRACTURE WHAT IS IT

Description: The meaning of the phrase 'constraint effect in fracture' has changed in the past two decades from 'contained plasticity' to a broader description of 'dependence of fracture toughness value on geometry of test specimen or structure'. This paper will first elucidate the fundamental mechanics reasons for the apparent 'constraint effects in fracture', followed by outlining a straightforward approach to overcoming this problem in both brittle (elastic) and ductile (elastic-plastic) fracture. It is … more
Date: October 29, 2008
Creator: Lam, P & Prof. Yuh J. Chao, P
Partner: UNT Libraries Government Documents Department
open access

Measuring the stress-bridging law of a heterogeneous material

Description: In this investigation, fracture experiments on a high explosive material (PBX 9501) were conducted using the digital image correlation technique. From the experimental measurement, we are able to determine quantitatively the stress-bridging law (or decohesion law), which characterizes the relationship between the bridging stress and the opening displacement cross the bridging zone. The plastic bonded HMX (PBX) high explosives are composed of the energetic crystal (HMX) and a polymeric binder. P… more
Date: January 1, 2002
Creator: Liu, C. (Cheng)
Partner: UNT Libraries Government Documents Department
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The Relationships between Weight Functions, Geometric Functions,and Compliance Functions in Linear Elastic Fracture Mechanics

Description: Linear elastic fracture mechanics is widely used in industry because it established simple and explicit relationships between the permissible loading conditions and the critical crack size that is allowed in a structure. Stress intensity factors are the above-mentioned functional expressions that relate load with crack size through geometric functions or weight functions. Compliance functions are to determine the crack/flaw size in a structure when optical inspection is inconvenient. As a resul… more
Date: February 6, 2007
Creator: Yuan, Rong
Partner: UNT Libraries Government Documents Department
open access

Morphological properties of poly (ethylene terephthalate) (PET) nanocomposites in relation to fracture toughness.

Description: The effect of incorporation of montmorillonite layered silicate (MLS) on poly (ethylene terephthalate) (PET) matrix was investigated. MLS was added in varying concentration of 1 to 5 weight percent in the PET matrix. DSC and polarized optical microscopy were used to determine the crystallization effects of MLS addition. Non isothermal crystallization kinetics showed that the melting temperature and crystallization temperature decrease as the MLS percent increases. This delayed crystallization a… more
Date: August 2005
Creator: Pendse, Siddhi
Partner: UNT Libraries
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Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites

Description: Nonlinear-elastic fracture mechanics methods are used to assess the fracture toughness of bulk metallic glass (BMG) composites; results are compared with similar measurements for other monolithic and composite BMG alloys. Mechanistically, plastic shielding gives rise to characteristic resistance?curve behavior where the fracture resistance increases with crack extension. Specifically, confinement of damage by second?phase dendrites is shown to result in enhancement of the toughness by nearly an… more
Date: May 26, 2009
Creator: Launey, Maximilien E.; Hofmann, Douglas C.; Suh, Jin-Yo; Kozachkov, Henry; Johnson, William L. & Ritchie, Robert O.
Partner: UNT Libraries Government Documents Department
open access

The significance of crack-resistance curves to the mixed-mode fracture toughness of human cortical bone

Description: The majority of fracture mechanics studies on the toughness of bone have been performed under tensile loading. However, it has recently been shown that the toughness of human cortical bone in the transverse (breaking) orientation is actually much lower in shear (mode II) than in tension (mode I); a fact that is physiologically relevant as in vivo bone is invariably loaded multiaxially. Since bone is a material that derives its fracture resistance primarily during crack growth through extrinsic … more
Date: March 25, 2010
Creator: Zimmermann, Elizabeth A.; Launey, Maximilien E. & Ritchie, Robert O.
Partner: UNT Libraries Government Documents Department
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Fracture Toughness Testing of Plastics under Various Environmental Conditions

Description: The primary objective of this study is to test the applicability to plastics of a fracture toughness testing tool developed for metals. The intent is to study pre-test conditioning of several plastic materials and the effect of the depth of the razor notch cut in the chevron notched fracture toughness test specimens. The study includes the careful preparation of samples followed by conditioning in various environments. Samples were subjected to laboratory air for a specific duration or to a con… more
Date: December 1997
Creator: Velpuri, Seshagirirao V.
Partner: UNT Libraries
open access

Characterizing size dependence of ceramic-fiber strength using modified Weibull distribution

Description: The strengths of ceramic fibers have been observed to increase with decreasing fiber diameter and length. The traditional single-modal Weibull distribution function can only take into account one type of flaw, which makes it inappropriate to characterize the strength dependence of both the diameter and the length since ceramic fibers usually have both volume and surface flaws which affect the strength dependence in different ways. Although the bi-modal Weibull distribution can be used to charac… more
Date: May 1, 1995
Creator: Zhu, Yuntian & Blumenthal, W.R.
Partner: UNT Libraries Government Documents Department
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Results of fracture mechanics analyses of the Adorer cranes in the device assembly facility using actual, rather than conservative, stress-components

Description: Fracture mechanics analyses were done on 3 critical locations on the lower flange of the load beam of the Ederer 5 ton and 4 ton cranes in the D.A.F. Facility. This was done to determine appropriate flaw sizes for NDE detection during periodic inspection, and appropriate inspection intervals.
Date: December 26, 1996
Creator: Dalder, E. N. C.
Partner: UNT Libraries Government Documents Department
open access

Evaluation of models for estimating changes in fracture permeability due to thermo-mechanical stresses in host rock surrounding a potential repository

Description: We provide in this report a methodology to estimate bounds on the changes in fracture permeability due to thermal-mechanical processes associated with excavation of drifts and emplacement of waste. This report is the first milestone associated with Task A of the LLNL initiative to evaluate available methods for estimating chamges in fracture permeability surrounding drifts in the Exploratory Studies Facility (ESF) and the potential repository at Yucca Mountain in response to (1) construction-in… more
Date: February 18, 1997
Creator: Berge, P. A.; Blair, S. C.; Shaffer, R. J. & Wang, H. F.
Partner: UNT Libraries Government Documents Department
open access

Results of fracture mechanics analyses of the Ederer cranes in the Device Assembly Facility: The effect of using a general expression for fatigue crack growth of the crane material

Description: The subject analyses were conducted on 3 critical locations on the lower flange of the load-beam of the Ederer 5 ton and 4 ton cranes in the D.A.F. facility. An expression for the fatigue-crack growth behavior of ferritic-pearlitic constructional steels (``Barsom Equation``) was used in place of the previously used equation to describe fatigue-crack growth behavior in this steel (base-line equation) to evaluate the effects of varying the fatigue-crack growth rate. Results appear that: (1) Propa… more
Date: February 3, 1997
Creator: Dalder, E. N. C.
Partner: UNT Libraries Government Documents Department
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Reactor Material Program Fracture Toughness of Type 304 Stainless Steel

Description: This report describes the experimental procedure for Type 304 Stainless Steel fracture toughness measurements and the application of results. Typical toughness values are given based on the completed test program for the Reactor Materials Program (RMP). Test specimen size effects and limitations of the applicability in the fracture mechanics methodology are outlined as well as a brief discussion on irradiation effects.
Date: March 28, 2001
Creator: Awadalla, N. G.
Partner: UNT Libraries Government Documents Department
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Probabilistic Fracture Mechanics Evaluation of Selected Passive Components – Technical Letter Report

Description: This report addresses the potential application of probabilistic fracture mechanics computer codes to support the Proactive Materials Degradation Assessment (PMDA) program as a method to predict component failure probabilities. The present report describes probabilistic fracture mechanics calculations that were performed for selected components using the PRO-LOCA and PRAISE computer codes. The calculations address the failure mechanisms of stress corrosion cracking, intergranular stress corrosi… more
Date: May 31, 2007
Creator: Simonen, Fredric A.; Doctor, Steven R.; Gosselin, Stephen R.; Rudland, David L.; Xu, H.; Wilkowski, Gery M. et al.
Partner: UNT Libraries Government Documents Department
open access

On the mechanistic role of the dentin-enamel junction in preventing the fracture of human teeth

Description: The dentin-enamel junction (DEJ), which is the interface between the dentin and outer enamel coating in teeth, is known for its unique biomechanical properties that provide a crack-arrest barrier for flaws formed in the brittle enamel. In this work, we re-examine how cracks propagate in the proximity of the DEJ, and specifically quantify, using interfacial fracture mechanics, the fracture toughness of the DEJ region. Additionally, we show that the vital function of the DEJ, in preventing cracks… more
Date: September 1, 2004
Creator: Imbeni, V.; Kruzic, J. J.; Marshall, G. W.; Marshall, S. J. & Ritchie, R. O.
Partner: UNT Libraries Government Documents Department
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Ductile damage modeling based on void coalescence and percolation theories

Description: A general model for ductile damage in metals is presented. It includes damage induced by shear stress as well as damage caused by volumetric tension. Spallation is included as a special case. Strain induced damage is also treated. Void nucleation and growth are included, and give rise to strain rate effects. Strain rate effects also arise in the model through elastic release wave propagation between damage centers. The underlying physics of the model is the nucleation, growth, and coalescence o… more
Date: September 1, 1995
Creator: Tonks, D.L.; Zurek, A.K. & Thissell, W.R.
Partner: UNT Libraries Government Documents Department
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