The Four Legged Stool

"Like a milking stool, society becomes dysfunctional if any leg is short or weak. The current argument is that civil society is the short, or weak, leg and thus our societal disarray." In this report to the Kettering Foundation, John McKnight examines this argument, making a case for the strengths of and the need for a stronger associational life for citizens.McKnight distinguishes associations from not-for-profit corporations, though they are often combined as the third leg of a "three-legged stool," the other legs being business and government. He points out their differences: not-for-profit corporations are usually formal and hierarchical, whereas associations tend to be informal and horizontal; not-for-profits use the special knowledge of professionals and experts to perform their functions, while associations generally use the experience and knowledge of member citizens.Society, McKnight argues, is actually like a four-legged stool, with associations being the fourth support. However, our focus on the three institutional legs has obscured the presence and vitality of the fourth.Alexis de Tocqueville recognized this powerful role of citizens in a democracy -- the power of association. In associations, he saw Americans making power. In voting, he saw them delegating power. As our three major institutions are pulling back from local community space -- governments cut budgets, not-for-profits reduce programs, and businesses contract -- the need for an alternative source of production becomes clear. Our future well-being depends on our rediscovery and nurturing of the fourth leg of the American stool -- associational life

Structural analysis applications

An account is given of the application of computer codes for the efficient conduct of three-dimensional inelastic analyses to aircraft gas turbine combustor, turbine blade, and turbine stator vane components. The synergetic consequences of the program's activities are illustrated by an evaluation of the computer analyses of thermal barrier coatings and of the Space Shuttle Main Engine's High Pressure Fuel Turbopump turbine blading. This software, in conjunction with state-of-the-art supercomputers, can significantly reduce design-task burdens

Multiaxial Cyclic Thermoplasticity Analysis with Besseling's Subvolume Method

A modification was formulated to Besseling's Subvolume Method to allow it to use multilinear stress-strain curves which are temperature dependent to perform cyclic thermoplasticity analyses. This method automotically reproduces certain aspects of real material behavior important in the analysis of Aircraft Gas Turbine Engine (AGTE) components. These include the Bauschinger effect, cross-hardening, and memory. This constitutive equation was implemented in a finite element computer program called CYANIDE. Subsequently, classical time dependent plasticity (creep) was added to the program. Since its inception, this program was assessed against laboratory and component testing and engine experience. The ability of this program to simulate AGTE material response characteristics was verified by this experience and its utility in providing data for life analyses was demonstrated. In this area of life analysis, the multiaxial thermoplasticity capabilities of the method have proved a match for the actual AGTE life experience

The 3D inelastic analysis methods for hot section components

The objective of this research is to develop an analytical tool capable of economically evaluating the cyclic time dependent plasticity which occurs in hot section engine components in areas of strain concentration resulting from the combination of both mechanical and thermal stresses. The techniques developed must be capable of accommodating large excursions in temperatures with the associated variations in material properties including plasticity and creep. The overall objective of this proposed program is to develop advanced 3-D inelastic structural/stress analysis methods and solution strategies for more accurate and yet more cost effective analysis of combustors, turbine blades, and vanes. The approach will be to develop four different theories, one linear and three higher order with increasing complexities including embedded singularities

Component specific modeling

The objective is to develop and verify a series of interdisciplinary modeling and analysis techniques that have been specialized to address three specific hot section components. These techniques will incorporate data as well as theoretical methods from many diverse areas including cycle and performance analysis, heat transfer analysis, linear and nonlinear stress analysis, and mission analysis. The new methods developed will be integrated to provide an accurate, efficient, and unified approach to analyzing combustor burner liners, hollow air-cooled turbine blades, and air-colled turbine vanes. For these components, the methods developed will predict temperature, deformation, stress, and strain histories throughout a complete flight mission

Component specific modeling

The objective was to develop and verify a series of interdisciplinary modeling and analysis techniques specialized to address hot section components. These techniques incorporate data as well as theoretical methods from many diverse areas, including cycle and performance analysis, heat transfer analysis, linear and nonlinear stress analysis, and mission analysis

Nonlinear analysis of an axisymmetric structure subjected to non-axisymmetric loading

The development of the SHELPC finite element computer program is detailed. This program is specialized to simulate the nonlinear material behavior which results from combustor liner hot streaks. This problem produces a nonlinear Fourier Series type loading on an axisymmetric structure. Example cases are presented

The 3D inelastic analysis methods for hot section components

Advanced 3-D inelastic structural/stress analysis methods and solution strategies for more accurate and yet more cost-effective analysis of combustors, turbine blades, and vanes are being developed. The approach is to develop four different theories, one linear and three higher order with increasing complexities including embedded singularities. Progress in each area is reported

Coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures

Accomplishments are described for the third years effort of a 5-year program to develop a methodology for coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures. These accomplishments include: (1) structural analysis capability specialized for graded composite structures including large deformation and deformation position eigenanalysis technologies; (2) a thermal analyzer specialized for graded composite structures; (3) absorption of electromagnetic waves by graded composite structures; and (4) coupled structural thermal/electromagnetic analysis of graded composite structures