| Development and Implementation of Practical Optimal LES Models |
31 MAR 2007 |
75 pages |
| Authors:
R. D. Moser; R. J. Adrian; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
 | One of the most promising techniques for the prediction of turbulent flows is that of Large Eddy Simulation (LES), in which an under-resolved representation of the turbulence is simulated numerically by modeling the effects of the unresolved small-scales on the simulation. Such simulations have been applied in several flows with reasonable success. However, there are several outstanding problems that need to be addressed before LES can fulfill its promise as ... |
|
| Analytic and Computational Studies on Micro-Propulsion and Micro-detonics |
22 AUG 2006 |
12 pages |
| Authors:
Mark Short; D. S. Stewart; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The Principal Investigators were funded by the AFOSR to conduct several theoretical investigations on aspects of micro-propulsion and micro-detonics technology. These included: (i) An examination of unsteady inert and reactive flows in rectangular and cylindrical channels with side- and end-wall mass injection intended as a model of micro-size rocket thrusters. (ii) An investigation of two issues associated with developing small-scale pulsed detonation wave engines. These concern the dynamics and criticality ... |
|
| Adjoint-based Aeroacoustic Control |
MAY 2006 |
54 pages |
| Authors:
Jonathan B. Freund; Randall R. Kleinman; Mingjun Wei; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A technique for controlling complex unsteady high-speed flows is being developed. Our approach uses numerical solutions of the adjoint of the compressible flow equations to circumvent the complexity of the flow and directly determine the sensitivity of a specified control objective to changes in actuation. Since this method requires a complete physical description of a turbulent flow which is only currently available from direct numerical simulations, the immediate objective obviously ... |
|
| Optimal Large Eddy Simulation of Turbulence |
29 MAR 2004 |
92 pages |
| Authors:
R. D. Moser; S. Balachandar; R. J. Adrian; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Optimal LES modeling is a new approach to the development of subgrid models of turbulence. It has been found to produce accurate LES simulations when based on reliable statistical information. Now, the primary effort in optimal model development is the determination of this statistical information from theoretical considerations, with minimal empirical input. The validity of the theoretically determined statistics is being tested against experimental and DNS data. When small-scales are ... |
|
| Analytical Modelling of Ignition of Condensed Energetic Materials, Pulsed Detonation Engines and Miniaturization of Explosive Systems: Final Report |
14 JAN 2003 |
7 pages |
| Authors:
Mark Short; Scott Stewart; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Over the duration of the grant, several papers were written by Short, his collaborators and students on AFOSR issues related to the proposal outline. Those that list whole or partial support of the AFOR (F49620-00-1-0005) are given below. Copies of the publications listed are also included. Some highlights of the most recent work are also included. |
|
| Vortex Packets in Turbulent Boundary Layers with Application to High Reynolds Number Effects, Isolated and Patterned Roughness, Near Wall Modeling and Strategies for Drag Reduction |
02 NOV 2001 |
16 pages |
| Authors:
R. J. Adrian; S. Balachandar; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The scientific goals of this work are to develop a complete physical model of turbulence in wall boundary layers and to develop means of describing and modeling surface roughness effect. We make use of recent developments in our understanding of the mechanistic structure of near wall turbulence for smooth walls at low Reynolds numbers to understand how large Reynolds number and wall roughness affect turbulence. We build upon experimental and ... |
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| Characterization of Optimal LES in Turbulent Channel Flow |
AUG 2001 |
8 pages |
| Authors:
R. D. Moser; S. Volker; P. Venugopal; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The application of large eddy simulation (LES) to wall-bounded turbulent flows has be hindered by the failure of current subgrid models in the strongly inbomogeneous region very near the wall. This is the LES wall modeling problem. To address this a new modeling approach called optimal LES modeling is applied to a turbulent channel flow. Ideal LES is an LES evolution that is guaranteed to produce correct statistics and accurate ... |
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| Filtering Boundary Conditions for LES and Embedded Boundary Simulations |
AUG 2001 |
8 pages |
| Authors:
A. Das; R. D. Moser; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Two related observations lead us to propose a new approach for embedding boundaries in the context of LES. In this approach, we treat the wall by filtering through it'. A homogeneous or nearly homogeneous filter is applied to the flow field including the embedded boundary. As a result, the boundary is no longer a sharp interface, but is diffused across the filter width. To recover a Direct Numerical Simulation (DNS), ... |
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| Studies of the Mechanics and Combustion of Energetic Materials for the Design of Explosive Systems |
MAY 2001 |
33 pages |
| Authors:
D. S. Stewart; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| This is the final report that summarizes the research activities carried out under the grant F08630-95-1-0004 (for 5 year, period 01/30/95 to 01/ 29/00), awarded to the University of Illinois (D. Scott Stewart, Principle Investigator) and the Air Force Research Laboratory, Munition Directorate, Eglin AFB. The major research findings are summarized in the Discussion of Research Accomplishments and they describe (1) development of new models for reactive flow and ignition ... |
|
| 20TH International Congress of Theoretical and Applied Mechanics |
15 JAN 2001 |
10 pages |
| Authors:
Hassan Aref; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The funds from this grant along those from other sources were used to support the 20th International Congress of Theoretical and Applied Mechanics, which took place in Chicago, IL during 27 August - 2 September 2000. These international conferences have been held every four years since 1924, except during World War II, and this was only the third time it was in the United States. It is not an exaggeration ... |
|
| Analytical Investigations on Detonation Theory and Mechanical Ignition of Explosive |
30 SEP 1999 |
9 pages |
| Authors:
D. S. Stewart; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The research carried out under this grant was on 1) the analytical theory of detonation stability and 2) the development of new models for description of the mechanical ignition of condensed explosives. The research directly and indirectly supported a separate effort at UIUC on the engineering design of explosive systems, specifically condensed phase explosives and the use of related numerical technologies. |
|
| A Microforce-Based Theory for Energetic Materials |
08 JUN 1999 |
3 pages |
| Authors:
Gregory A. Ruderman; D. S. Stewart; Eliot Fried; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Employing advanced tools of continuum thermomechanics, we have developed a fully three-dimensional framework, which in its most general form is able to model all the mentioned behaviors of energetic materials. The concept of microforces, forces that drive changes in material microstructure, is employed to generate consistent equations of evolution for combustion and phase transitions. The method of generating equations for thermomechanical behavior using microforces begins with the generation of a ... |
|
| Multidimensional Structure of Wall Bounded Turbulence-Continuation |
22 DEC 1998 |
392 pages |
| Authors:
Ronald J. Adrian; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Broad goals of the work were to study the structure of the turbulent wall layer using modern particle image velocimetry techniques to measure instantaneous velocity fields and to interpret the structure. Earlier work (C. D. Meinhart, Ph.D. Thesis. Univ. Illinois, 1994) supported by ONR had suggested that low momentum regions are created in wall turbulence by the alignment of hairpin vortices, but the field of view of this work was ... |
|
| Large Capacity PIV Diagnostic Facility for Turbulence Research |
23 JUL 97 |
37 pages |
| Authors:
Ronald J. Adrian; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The purpose of this grant was to construct a stereographic particle image velocimeter (SPIV) for the measurement of three-dimensional velocity vectors on planar slices through fluids defined by laser light sheets. The facility has been constructed from components, requiring the use of multiple vendors. A stereographic particle image velocimeter using two 2,048 x 2,048 pixel video cameras has been constructed and shown to work. An attached paper by Liu, Adrian, ... |
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| Theoretical and Experimental Studies of Reacting Compressible Flow |
JUN 97 |
13 pages |
| Authors:
D. Scott Stewart; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| This proposal for this grant requested funds to support travel expenses for graduate students to participate in summer workshop programs and experimental research at the facilities of the Armament Directorate of Wright Laboratories at Eglin AFB. Funds were also requested to support a Graduate Research Assistant (GRA) to support related, theoretical research. The area of the research supported by the grant was multi-dimensional, time-dependent, reacting compressible flows. The AASERT grant ... |
|
| Lectures on Detonation Physics: Introduction to the Theory of Detonation Shock Dynamics |
25 AUG 93 |
57 pages |
| Authors:
D. S. Stewart; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| These lectures review some basic results of detonation theory and are specialized to serve as an introduction to the theory of Detonation Shock Dynamics (DSD). The theory of DSD is a time dependent, multidimensional theory for the propagation of near Ohapman Jouguet (OJ) detonations. This theory is especially relevant to applications of detonation propagation in condensed explosives and the basic dynamics in freely propagating gaseous explosives as well. The theory ... |
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| A Doubly Periodic Rectangular Array of Fiber-Matrix Interfacial Cracks Under Longitudinal Shearing. |
1993 |
|
| Authors:
Hong Teng; A. Agah-Tehrani; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
 | This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, analytical, composite materials, theoretical materials and material types:, fibers material characteristics and data fields:, antiplane strain deformations, fiber spacings, interfacial shear tractions, longitudinal shearing, plain strain, plane stress deformations, stress deformations, stress intensity factors parameter values relevant to the data:, volume fractions miscellaneous and special technical terms:, crack lengths, interfacial cracks, ... |
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| Stereoscopic Particle Image Velocimetry Applied to Liquid Flows, |
23 JUL 1992 |
|
| Authors:
A. K. Prasad; R. J. Adrian; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A twin-camera stereoscopic system has been developed to extend conventional high image-density. Particle Image Velocimetry (PIV) to three-dimensional vectors on planar do mains. The stereoscopic velocimeter performs with extremely high accuracy. Translation tests have yielded errors (mu) of 0.2 % of full-scale for the in-plane displacement, and 0.8 % of full-scale for the out-of-place component both of which agree with the errors predicted by an uncertainty analysis. In addition, modified ... |
|
| The Mechanics of Internal Stress and Microcrack Toughening Mechanisms in Ceramics |
APR 85 |
|
| Authors:
R. M. McMeeking; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A simple constitive law is proposed for the description of a certain ceramic composite which undergoes stress induced martensitic transformation. This law is used in finite element calculations to investigate the shear effect on the transformation zone near a crack tip. A formula describing the stress intensity factor change due to the shear contribution of the transformation given. Significant loss of toughness is observed in the case of a stationary ... |
|
| The Shearing Contribution in Transformation Toughening of Brittle Materials |
MAR 85 |
|
| Authors:
P. Sofronis; R. M. McMeeking; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A simple constitutive law is proposed for the description of a ceramic composite which undergoes stress induced martensitic transformation. This law is used in finite element calculations to investigate the shear effect on the transformation zone near a crack tip. A formula describing the stress intensity factor change due to the shear contribution of the transformation is given. Significant loss of toughness is observed in the case of a stationary ... |
|
| Mechanics of Near Tip Microcracking in Brittle Material |
MAR 85 |
|
| Authors:
P. Charalambides; R. M. McMeeking; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A continuum mechanics description, of the phenomenon of stress induced microcracking has been used to study the near tip stress and strain fields and the size and shape of a small scale damaged zone for a stationary mode I crack in an elastic body. The microcrack density was found to characterize three regions of interest. In the outer region the microcrack density is zero and the stress and strain fields ... |
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| Stress Intensity Factors for Slightly Kinked, Partially Closed Cracks in Compression |
APR 1984 |
|
| Authors:
N. Aravas; R. M. McMeeking; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A solution is presented for the elastic stress intensity factors at the tips of a slightly kinked, partially closed crack in compression. The solution is accurate to first order in the deviation of the crack surface from a straight line and is carried out using perturbation procedures analogous to those of Banichuk, Goldstein and Salganik, and Cotterell and Rice for the problem of an open crack. Comparison with the exact ... |
|
| Near Chapman-Jouget Detonations, |
FEB 1984 |
|
| Authors:
D. S. Stewart; G. S. S. Ludford; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The moving boundary problem that arises from a certain model of one-dimensional detonation waves is considered. Burgers equations for a function, f, have to be solved on the two sides of a discontinuity, at which f and the jump in iits derivative (corresponding to the exothermic reaction) are prescribed. The steady solution, a summary of its linear stability characteristics, and some preliminary numerical results are presented. (Author) |
|
| The Mechanics of Delamination in Fiber-Reinforced Composite Materials. Part II - Delamination Behavior and Fracture Mechanics Parameters, |
NOV 1983 |
|
| Authors:
S. S. Wang; I. Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination was determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method using singular finite elements was developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special ... |
|
| The Mechanics of Delamination in Fiber-Reinforced Composite Materials. Part I - Stress Singularities and Solution Structure, |
NOV 1983 |
|
| Authors:
S. S. Wang; I. Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The fundamental mechanics of delamination in fiber composite laminates was studied. Mathematical formulation of the problem is based on recently developed laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations were determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a ... |
|
| The Mechanics of Delamination in Fiber-Reinforced Composite Materials. Part 1. Stress Singularities and Solution Structure |
Nov 1983 |
47 pages |
| Authors:
S S Wang; I Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on recently developed laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a ... |
|
| The Mechanics of Delamination in Fiber-Reinforced Composite Materials. Part 2. Delamination Behavior and Fracture Mechanics Parameters |
Nov 1983 |
61 pages |
| Authors:
S S Wang; I Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special ... |
|
| Viscoelastic Effect on Dynamic Crack Propagation in Homalite 100, |
OCT 1983 |
|
| Authors:
K. S. Kim; K. L. Dickerson; W. G. Knauss; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The optical method of caustics is used to determine the stress intensity factor for a running crack in a viscoelastic material. A formulation of the quasi-static deformation of materials with rheologically simple shadow-optic creep functions is derived for the caustics, solved numerically and applied to the fracture testing of Homalite-100 at various temperatures (40 deg C - 100 deg C). Theoretical and experimental caustics show good agreement in shape even ... |
|
| Evolution of Near Chapman-Jouget Deflagrations, |
FEB 1983 |
|
| Authors:
Donald Scott Stewart; G. S. S. Ludford; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| In order to analytically investigate flame acceleration effects, Stewart and Ludford posed a model rationally derived from Arrehnius kinetics in which the temperature of the thin reaction zone is constant. For small heat-release during combustion this model has been shown to have a simple limiting form. In this paper the authors show that such a model leads to a Burger's equation for the evolution of disturbances moving with the flame ... |
|
| The Premixed Flame in a Counterflow |
02 JUN 1981 |
|
| Authors:
J. Buckmaster; D. Mikolaitis; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
|
| Flame Stabilization in a Rear Stagnation Point Flow |
01 MAY 1981 |
|
| Authors:
D. Mikolaitis; J. Buckmaster; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
|
| Boundary-Layer Effects in Composite Laminates: Free-Edge Stress Singularities. Part 6 |
APR 81 |
49 pages |
| Authors:
S. S. Wang; I. Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A rigorous mathematical model has been obtained for the boundary- layer free-edge stress singularity in angleplied and crossplied fiber composite laminates. The solution was obtained using the previously developed method (under the grant) consisting of complex-variable stress function potentials and unique eigenfunction expansions. The required order of the boundary-layer stress singularity is determined by solving the transcendental characteristic equation obtained from the homogeneous solution of the partial differential equations. Numerical ... |
|
| Boundary-Layer Effects in Composite Laminates: Free-Edge Stress Singularities. Final Report-Part VI, |
APR 81 |
|
| Authors:
S. S. Wang; I. Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A rigorous mathematical model was obtained for the boundary-layer free-edge stress singularity in angleplied and crossplied fiber composite laminates. The solution was obtained using a previously developed method consisting of complex-variable stress function potentials and unique eigenfunction expansions. Numerical results obtained show that the boundary- layer stress singularity depends only upon material elastic constants and fiber orientation of the adjacent plies. For angleplied and crossplied laminates the order of the ... |
|
| Edge Delamination In Angle-Ply Composite Laminates. Part 5 |
FEB 81 |
60 pages |
| Authors:
S. S. Wang; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Edge delamination has caused severe concern in the design and analysis of advanced composite materials and structures. Due to its complex nature, very limited knowledge for the problem is currently available. It involves not only geometric and material discontinuities but also inherently coupled mode I, II and III fracture in the layered anisotropic system. Based on complex-variable stress potentials in the anisotropic elasticity theory and eigenfunction expansion, exact orders of ... |
|
| Interlaminar Crack Growth in Fiber Reinforced Composites During Fatigue. Part 3 |
FEB 81 |
47 pages |
| Authors:
S. S. Wang; H. T. Wang; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Interlaminar crack growth behavior in fiber-reinforced composites subjected to fatigue loading was investigated experimentally and theoretically. In the experimental phase of the study, interlaminar crack propagation rates and mechanisms were detertnined for the cases of various geometrles. laminate parameters and cyclic stress levels. An advanced singular hybrid-stress finite element method was used in conjunction with the experimental results to examine the local crack-tip behavior and to characterize the crack propagation ... |
|
| An Analysis of Cracks Emanating From a Circular Hole in Unidirectional Fiber Reinforced Composites. Part 2 |
FEB 81 |
45 pages |
| Authors:
S. S. Wang; J. F. Yau; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| An analytical method is developed for cracks emanating from a circular hole in an off-axis unidirectional fiber-reinforced composite. The method is formulated by using conservation laws of elasticity and fundamental relationships in anisotropic fracture mechanics. The method provides a very convenient and accurate means to examine the complicated crack behavior, when used in conjunction with a suitable numerical scheme such as the finite element method. The formulation is eventually reduced ... |
|
| Analysis of Interface Cracks in Adhesively Bonded Lap Shear Joints. Part 4 |
FEB 81 |
49 pages |
| Authors:
S. S. Wang; J. F. Yau; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The conservation laws of elasticity for nonhomogeneous materials developed under this grant are used to study the crack behavior in adhesively bonded lap shear joints. These laws and the fundamental relationships in fracture mechanics of interface cracks, the problem is reduced to a pair of linear algebraic equations, and stress intensity solutions can be determined directly by information extracted from the far field. The numerical results obtained show that: (1) ... |
|
| An Analysis of Cracks Emanating From a Circular Hole in Unidirectional Fiber Reinforced Composites. Final Report-Part II, |
FEB 81 |
|
| Authors:
S. S. Wang; J. F. Yau; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| An analytical method was developed for cracks emanating from a circular hold in an off-axis unidirectional fiberglass reinforced epoxy composite. The method is formulated by using conservation laws of elasticity and fundamental relationships in anisotropic fracture mechanics. The method provides a very convenient and accurate means to examine the complicated crack behavior, when used in conjunction with a suitable numerical scheme such as the finite element method. The formulation is ... |
|
| Edge Delamination in Angle-Ply Composite Laminates. Final Report-Part V, |
FEB 81 |
|
| Authors:
S. S. Wang; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A theoretical method based on anisotropic elasticity was developed for describing the edge delamination stress intensity characteristics in angle- ply composite laminates. The method predicts exact orders of the three- dimensional stress singularity in a delamination crack tip region. Fracture mechanics parameters such as the mixed-mode stress intensity factors and associated energy release rates for edge delamination can be calculated explicitly. Solutions were obtained for edge delaminated angle-ply composites under ... |
|
| Analysis of Interface Cracks in Adhesively Bonded Lap Shear Joints. Final Report-Part IV, |
FEB 81 |
|
| Authors:
S. S. Wang; J. F. Yau; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Conservation laws of elasticity for nonhomogeneous materials were used to study the crack behavior in adhesively bonded lap shear joints. Using these laws and the fundamental relationships in fracture mechanics of interface cracks, the problem is reduced to a pair of linear algebraic equations, and stress intensity solutions can be determined directly by information extracted from the far field. Numerical results obtained for: a stress intensity factor of a lap ... |
|
| Boundary Layer Thermal Stresses in Angle-Ply Composite Laminates. Final Report-Part I, |
FEB 1981 |
|
| Authors:
S. S. Wang; I. Choi; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A theoretical investigation of boundary-layer thermal stress singularities and distributions in angle-ply composite laminates subjected to uniform thermal loading is presented. By using appropriate anisotropic elasticity field equations and Lehknitskii's complex stress functions, a system of sixth-order governing partial differential equations for the current problem is obtained. Homogeneous boundary conditions and interface continuity lead to the establishment of a transcendental characteristic equation for determining the boundary-layer stress singularity in a ... |
|
| Interlaminar Crack Growth in Fiber Reinforced Composites During Fatigue. Final Report-Part III, |
FEB 1981 |
|
| Authors:
S. S. Wang; H. T. Wang; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Interlaminar crack growth behavior in fiber-reinforced composites subjected to fatigue loading was investigated experimentally and theoretically. Interlaminar crack propagation rate and mechanisms were determined for the cases of various geometries, laminate parameters and cyclic stress levels. An advanced singular hybrid-stress finite element method was used in conjunction with the experimental results to examine the local crack-tip behavior and to characterize the crack propagation during fatigue. The results show that crack ... |
|
| Review of Contemporary Approaches to Fatigue Damage Analysis |
80 |
|
| Authors:
D. F. Socie; J-d. Morrow; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| A review of current methods for fatigue damage analysis employing smooth specimen materials data for predicting the service life of components and structures subjected to variable loading is presented. Special emphasis is placed on the detailed elements of the analysis, as well as the overall pattern for synthesizing these elements into a working computer-based program. After discussing the details of the analysis, application of the techniques is illustrated by making ... |
|
| An Analysis of Interface Crack in Adhesively Bonded Lap Shear Joints |
DEC 79 |
|
| Authors:
S. S. Wang; J. F. Yau; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| This paper presents an analytical study of interface crack problems in adhesively bonded lap shear joints. A convenient and accurate method of analysis is developed on the basis of conservation laws in elasticity and of the fundamental relationships in fracture mechanics of interface crack problems. The problem is eventually reduced to a system of linear algebraic equations of mixed-mode stress intensity factor solutions. One of the salient features of the ... |
|
| The Stabilization of Slip on a Narrow Weakening Fault Zone by Coupled Deformation-Pore Fluid Diffusion |
AUG 1979 |
|
| Authors:
J. W. Rudnicki; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| The transient stabilization of rapid slip on a very narrow weakening fault zone by the coupling of the deformation with pore fluid diffusion is investigated. The fault zone is assumed to be so narrow that it can be idealized as a planar surface and the constitutive law is specified as a relation between stress on the fault tau sub f/t and relative slip delta. The study considers only the stabilizing ... |
|
| Rotation of Principal Stress Axes Caused by Faulting |
MAR 1979 |
|
| Authors:
J. W. Rudnicki; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
|
| Significance of Cyclic History Dependent Deformation Phenomena of Metals on Fatigue Life Estimation |
JUN 1974 |
34 pages |
| Authors:
H. R. Jhansale; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Simple calculations for determining estimated extremes in fatigue life of metals with or without accounting for cycle dependent hardening, softening and mean stress relaxation in fatigue analysis, are presented. These calculations aid in assessing the importance of cyclic deformation properties in cumulative damage procedures. An SAE 1045 quenched and tempered steel is considered for illustration. In general cycle dependent deformation phenomena may be important only in intermediate and long life ... |
|
| Fatigue Crack Initiation as a Function of Temperature and Strain Rate |
MAR 1974 |
47 pages |
| Authors:
S. J. Stadnick; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
| Thirty-four specimens of pure (0.999+) aluminum were cyclically strained under a variety of plastic strain ranges, plastic strain rates and temperatures in an atmosphere of dry nitrogen. Stable cyclic stress strain data was recorded for a variety of plastic strain rates and temperatures. A time- temperature parameter method of analysis was found to give an adequate representation of the stable cyclid stress-strain relationships for the conditions tested. The specimen surface ... |
|
| PRELIMINARY INVESTIGATION OF MEASUREMENT OF ELASTIC MODULI OF COMPOSITES USING STRAIN GAGES. |
1967 |
|
| Authors:
G. G. Trantina; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
|
| MODES OF FAILURE OF GLASS FIBER REINFORCED PLASTICS UNDER COMPRESSIVE LOADS. |
1967 |
|
| Authors:
J. W. Gillman; H. T. Corten; ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
|
|
Reports by Corporate Author
