Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 80 for “"brittle failure"”.
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Modeling of brittle failure and comparisons to laboratory experiments
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.
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3D numerical modelling of brittle failure in mechanized excavation of deep tunnels
… these geological hazards is the stress-induced brittle failure of hard rocks, leading to spalling (formation of rock slabs) and/or rockbursting (violent ejection of rock fragments). This thesis initially deals with brittle failure, both in laboratory tests (uniaxial and/or triaxial) and in …
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Characterization of crack propagation and brittle failure induced by discrete, high velocity waterjet impacts in crystalline rocks, The
Includes bibliographical references (pages 297-304).
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Deformation and fracture of polycarbonate and rubber-modified polycarbonate under controlled temperature, deformation rate, and notch stress triaxiality
… begins to travel into the grip region, ductile failure occurs due to extensive stretching. The fracture is surface initiated. The load at yield is shown to be dependent on temperature and displacement rate. The load at yield increases with increasing strain rate and decreases with increasing …
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The Ductile to Brittle Transition in Polycarbonate
… in order to simulate the ductile to brittle failure transition in polycarbonate. The cohesive zone model is motivated by experimental evidence that two different critical energies per unit area of crack growth exist in glassy polymers. A higher energy state is associated with ductile …
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Scale-model investigation of brittle tunnel failure using a true-triaxial device
Brittle instabilities in tunnel excavation have led to severe consequences such as spalling, violent rock ejection or rock burst, and tunnel collapse. Detached rocks from the tunnel boundary not only compromise the structural integrity of tunnels but also pose significant safety risks to personnel …
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Accelerated Testing Method to Estimate the Lifetime of Polyethylene Pipes
… to quickly develop predictions of the time-to-failure under different loading levels allows designers to choose the best polymeric material for a specific application. Additionally, it helps material producers to design, manufacture, test, and modify a polymeric material more rapidly. In the …
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Finite Element Analysis of Thermoviscoplastic Deformations of an Impact-Loaded Prenotched Plate
… in the sense that at low speed of impact, a brittle failure ensues at a point on the upper surface of the notch tip. However, at high impact speeds, a ductile failure in the form of a shear band initiates first from a point on the lower surface of the notch tip. The predicted speed at which …
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Nonlinear Truss Analysis of Non-ductile Reinforced Concrete Frames with Unreinforced Masonry Infills
… which may even lead to collapse due to brittle failure modes. Furthermore, the effect of the infills on the seismic response of the structural system is not always accounted for in analysis and design. At present, there is no consensus on whether masonry infills are beneficial (by …
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Laboratory Ultrasonic Pulse Velocity Logging for Determination of Elastic Properties from Rock Core
… recognized as significant mechanisms of violent brittle failure. In order to predict whether violent brittle failure will occur, it is important to identify the location of stiffness transitions that are associated with geologic structure. One approach to identify the effect of geologic …
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ΣΥΜΒΟΛΗ ΣΤΗ ΒΕΛΤΙΩΣΗ ΤΗΣ ΣΕΙΣΜΙΚΗΣ ΣΥΜΠΕΡΙΦΟΡΑΣ ΕΞΩΤΕΡΙΚΩΝ ΚΟΜΒΩΝ ΠΛΑΙΣΙΩΝ ΑΠΟ Ο/Σ: αναλυτική και πειραματική έρευνα
… UNDER STRONG EARTHQUAKE EXCITATIONS IS THE BRITTLE FAILURE OF THE B/C JOINTS SUBJECTED TO LARGE CYCLIC SHEAR . IF THIS BRITTLE FAILURE IS AVOIDED, SAFETY AND RELIABILITY OF REINFORCED CONCRETE STRUCTURES UNDER A STRONG EARTHQUAKE CAN BE CONSIDERABLY IMPROVED. THE OBJECTIVE OF THE PRESENT …
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Evaluation of the Flexural Response of Steel Reinforced UHP-FRC Beams Using Distributed Sensing
… of UHP-FRC beams in flexure, leading to a brittle failure mechanism due to crack localization. Previous studies faced limitations in fully exploring this interaction due to conventional sensors. Distributed fibre-optic sensors (DFOS), particularly based on optical frequency domain …
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Use of acoustic emission to study deformation of mild steel in hydrogen and nitrogen environments
… nitrogen typically failed by bursting (ductile failure) while those tested in hydrogen typically failed by leaking ("brittle" failure).
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Blast Retrofit of Unreinforced Masonry Walls Using Fabric Reinforced Cementitious Matrix (FRCM) Composites
… walls. Such walls are vulnerable to sudden and brittle failure under blast loads due to their insufficient out-of-plane strength. The failure of such walls under blast pressures can also result in fragmentation and wall debris which can injure building occupants. Over the years, researchers have …
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Impact fracture of austenitic stainless steels
… gas. Because of the risk of catastrophe if brittle failure occurs, careful material selection is imperative. Austenitic stainless steels may be a likely choice for hydrogen service because their behavior in high pressure hydrogen ranges from no apparent damage to relevant, but generally …
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Statistical modelling of the transition toughness properties of low alloy pressure vessel steels
… on a number of metallurgical factors and failure modes; therefore, the micro-mechanisms of the ductile and brittle failure are explored and an assessment of the current best thinking on the modelling of crack arrest toughness is also considered. It has been established in this work that a …
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Micro-Architected Carbon Composites
… been produced to meet this desire but are highly brittle and unsuitable for mechanical applications. Three lattice topologies with relative density of 20% were produced in a custom polymer and pyrolyzed into carbon lattices. Two different methods of infiltrating an epoxy matrix into these …
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Things fall apart: the universal geometry of failure
… are everywhere. These ubiquitous signatures of brittle failure can be found from micron to kilometer scales in natural and human-made systems alike. When things fall apart, they encode the mechanisms of their failure in their geometry. In this dissertation, I implement a novel geometric …
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Analysis of Code Procedures for Seismic Assessment of Existing Buildings: Italian Seismic Code, EC8, ATC-40, FEMA356, FEMA440
… in plan and elevation, domination of brittle failure modes over ductile ones, etc. On account of that, seismic assessment of existing buildings is adopted as a problem which needs specific treatment in building codes. The present study analyzes five codes for assessment of existing …
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