Enabling Technologies for Unified Life-Cycle Engineering of Structural Components (1991) / Chapter Skim
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7 CRITICAL ISSUES
7 CRITICAL ISSUES
Pages 39-58
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From page 39... ...
The critical issues are: information. · ULCE-driven development of materials processing and repair methodologies requires integration of research and development (R&D)
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From page 40... ...
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From page 42... ...
Additional insight into the benefits and requirements of the ULCE approach is obtained by understanding the needs and concerns which are the basis for the critical issues and a brief description of each and of the enabling technologies is given in the following section. CRITICAL ISSUE 1 ULCE-driven development of materials processing and repair methodologies requires integration of R&D across disciplines.
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From page 43... ...
This knowledge base has allowed formulation of constitutive equations describing observed behavior, and sometimes predicting it. Actual service conditions are far more complicated than these test conditions, particularly when time-varying conditions occur under which the principal modes of damage change over time aswell.
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From page 44... ...
These manufacturing processes must address both initial component manufacturing and in-service repair, since field military equipment will be subject to environmental damage, battle damage, and maintenance damage, as well as normal wear and tear. It is imperative that appropriate repair techniques be developed that can restore most of the original structural capability.
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From page 45... ...
This, coupled with simultaneous measures of service conditions would provide a basis for model validation and provide input data for future analyses. Technologies f or Enhancing Design f or Supportability Advances in repair methodologies, inspectability, and lifetime prediction models are needed to enhance design for supportability.
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From page 46... ...
The fourth is a computerized data base that provides information that potentially can close the loop between the sensors and the process controls and replace the human component. CRITICAL ISSUE 2 Advanced analytical modeling and simulation methods to predict actual component manufacture, operation, and logistics do not exist to the extent required to preclude the need for physical prototypes and mock-ups.
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From page 47... ...
For example, large material strain induced by deformations in manufacturing require special attention in finite element modeling and solution algorithms and boundary conditions for processes are, at times, more complex than those for modeling a component in operation. Higher-level simulations of factories and sequences of manufacturing operations offer considerable promise in providing a product designer with trade-offs and impacts of a potential design.
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From page 48... ...
Finite element methods have matured and are in common use but are only available for deterministic analysis. Thus, variations in materials properties, dimensions, and applied forces can only be considered by repeating analysis computations with different parameter values.
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From page 49... ...
Today's CAD-CAM systems do not fully meet this requirement. Deficiencies lie in the inability to represent all the product definition data since CAD-CAM systems, including second-generation solid modelers and workstation CAD-CAM systems, focus primarily on the geometric data and are deficient in handling nonshape data (i.e., notes, tolerances, specifications)
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From page 50... ...
Supercomputer systems need to be adapted to support solid modeling as utilized in the design process to support the definition of data for manufacturing. A primary concern is that the needs of the ULCE information system cannot be met adequately merely by writing more software.
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From page 51... ...
Software needs include design assessment tools incorporating powerful finite element packages for structural, thermal, and aerodynamic analyses; simulation tools; and capabilities to model and display components to aid in visualizing designs. Similarly, there needs to be software that will allow manufacturing process information and software to be meshed more efficiently and flexibly with information and software from design, manufacturing facilities, materials, and field experience.
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From page 52... ...
Enabling Technologies Cognitive Systems Science and Technology The new disciplines of artificial intelligence and neural nets and their specialty subareas based on symbolic processing, nonprocedural programming languages, and use of heuristics need to be motivated to fuse their strengths in order to handle practical problems of significant size and technical difficulty. ULCE is one such endeavor.
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From page 53... ...
Product Definition Standards Technology The current industry standard for product definition data exchange is the Initial Graphics Exchange Specifications (IGES) developed by a volunteer industry committee supported by the National Institute of Standards and Technology.
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From page 54... ...
to assess the difference between actual field experience and the tests with which the product was accepted for delivery. The comparison will serve two purposes: adjust both the field and laboratory data acquisition process and pertinent specifications for future programs; and develop design rules as well as laboratory test conditions that address the conditions experienced in the field.
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From page 55... ...
To develop a practical risk analysis, the relationship of cost drivers to the uncertainties of applying new materials must be understood and quantified in a manner that would permit rigorous mathematical analysis. A risk assessment capability is driven particularly by · Application of new materials that incur long development cycles that include testing the materials' behavior during manufacturing processes and in the intended use environment, and ~ Field data collection, as well as laboratory data, that only provide information on existing material and/or structures from which conclusions are drawn as to the material's failure mechanisms.
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From page 56... ...
There are a number of NDE techniques that offer the possibility of being utilized via embedded sensors to continuously monitor vital materials characteristics. These techniques include: fiber optic sensors utilizing fluorescent spectroscopy or polarization spectroscopy; dielectric or electrical conductivity measurement utilizing microwaves, capacitance probes, embedded electrodes or eddy current coils, and acoustic transducers with conventional electrical connectors or with an optical fiber array coupled to acoustic emission sensors.
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From page 57... ...
To support such artificial intelligence techniques, a data base will also need to be developed from actual field experience with aircraft damage, which in turn would relate such damage to reliability impact and aircraft availability. Knowledge-Based and Expert Systems Expert systems and new data bases currently being advanced should be developed in such a fashion that design knowledge and design rules can be easily sorted by dominant effect on items such as performance, reliability, manufacturability, and influence on cost and schedule.
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From page 58... ...
1985. Processing of pattern based information, Part 1: Inductive methods suitable for use in patten recognition and artificial intelligence.
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