DI-SESS-80198B
Internal LOADS AND Static Strength Analysis Report
The Internal Loads and Static Strength Analysis Report details load derivation, stress, and strength computations to substantiate structural integrity for aircraft and stores, ensuring compliance with contract and airworthiness requirements.
Approval DateApril 11, 2014
AMSC NumberF9462
Preparing Activity—
Project Number—
OPR11 (AFLCMC/EZFS)
DTIC Applicable—
GIDEP ApplicableNo
Limitation—
Applicable Forms—
Approval Limitation—
Form Version—
DID Formatfree_text
963C CompliantYes
DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.
Supersedes
DI-GDRQ-80198A
Related
—Description & Purpose
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Application & Interrelationship
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Use & Relationship
The Internal Loads and Static Strength Analysis Report presents the derivation of internal loads, resulting stresses, and strength computations that analytically substantiate the structural ability of aircraft and aircraft-carried stores to react to critical external loading conditions. This analysis is used to substantiate the structural adequacy of the design for meeting contract requirements, and for showing compliance to airworthiness certification criteria. The report is also used to evaluate any engineering change proposals, to serve as a basis for modifications, structural repair, and damage limits, and to evaluate any possible incidents or accidents during operation.
a. The Internal Loads and Static Strength Analysis Report Data Item Description (DID) is applicable to the analyses of aircraft, missiles, aircraft-carried stores, and follow-on modification programs.
b. This DID contains the format, content, and intended use information for the data product resulting from the work task described in the contract.
Preparation Instructions
1Reference documents.The applicable issue of the documents cited herein, including their approval dates and dates of any applicable amendments, notices and revisions, shall be as specified in the solicitation or contract.
2Format.The Internal Loads and Static Strength Analysis Report shall use the format stated below:
2.1Title Page
2.2Table of contents
2.3List of Symbols and Acronyms
2.4Executive Summary
2.5Revision status sheet
2.6References
2.7Table of minimum margins of safety that includes part name, aircraft load condition, critical load condition on part, and analysis page number
2.8Introduction
2.9Material Properties and Allowables Summary
2.10Coordinate Systems
2.11External loads
2.12Internal loads
2.13Detailed stress analyses
2.14Appendix
2.15Analysis Checking by Approved Representative
3Content.The Internal Loads and Static Strength Analysis Report shall present detailed analyses of all safety-of-flight primary structure components and abbreviated analyses of all secondary structure components of the airframe to demonstrate load paths of adequate strength.
3.1Aircraft structures.The Internal Loads and Static Strength Analysis Report shall present analysis of the structural components of the aircraft including the following:
3.1.1Fuselage, including canopy, fuselage-attached engine mounts, fuselage-mounted speed reduction devices, tie-down structure for seats, litter, cargo, and equipment racks, and all actuating structure and attachments.
3.1.2Wing, including all attachments and actuating structures, hard points, moveable control surfaces, wing-mounted speed reduction devices and auxiliary lift devices.
3.1.3Empennage, including fixed horizontal and vertical surfaces, moveable surfaces, their attachments, and actuating support structures.
3.1.4Control System and surfaces, either manual or powered, including cables, rods, bell cranks, automatic parts, devices, and actuators.
3.1.5Landing and take-off gear, including actuators and attachments, and arresting gears.
3.1.6Airframe-engine interface components to include engine mounts and nacelles.
3.1.7Miscellaneous structure, including seats, equipment racks, pylons, armament attachments, fuselage and wing external fuel tanks, their fittings and attachment, Aerial refueling system. Cargo handling and aerial delivery system. as well as fittings, attachments and actuators not elsewhere analyzed.
3.2Missiles and aircraft-carried stores.The Internal Loads and Static Strength Analysis Report shall present analyses of the following major structural components:
3.2.1Body structure, including pressure vessels and those serving as primary structures, engine mount structure, control surfaces and control systems support structure and its actuating structure
3.2.2Wing, either fixed or deployable, and attachments
3.2.3Control surfaces, including fixed, deployable, and moveable
3.2.4Control systems actuators, mechanisms, and attachment
3.2.5Suspension structure, including lugs and captive-carry interface hardware
3.2.6Miscellaneous structure, including welded joints, mounted equipment and attachments, fittings, mechanisms, and actuators not elsewhere analyzed.
3.3Aircraft internal and external modifications.The report shall document revisions to previous airframe stress analyses and shall present strength analysis of new and modified installations and affected structures.
3.4External loads.The report shall provide:
3.4.1Curves or tables showing maximum external loadings of shears, bending moments, torsion
3.4.2Where appropriate, temperatures and time and temperature gradients
3.4.3Documentation of all design conditions considered (maneuver, gust, ground loading, etc.)
3.4.4Rationale for analysis conditions selected. Considered loads should include: aerodynamic, inertial, thermal loading, fatigue loads, pressurization (if applicable), and bird strikes
3.4.5Documentation of magnitudes and distributions of all loads used for design of the system in its operational environment, and provide a free body diagram showing loads and reactions when applicable. Down select of worst case conditions, and include shear, bending moment, and torsion data for all conditions
3.4.6A detailed presentation of the analysis method along with sample calculations for determining loads
3.4.7A list references and provide derivations for any assumptions
3.5Internal loads.The internal loads section may be separately prepared or combined with the detailed stress analysis described in 3.6, below. Internal loads will be tabulated for all members, but repetitive structures may be substantiated by analysis of the common structural member having the maximum loading. The computation of internal loads on all structural members shall be shown to be complete for critical, external loading conditions and show the steps considered in their development. Internal loads are identified as limit or design ultimate loads. When internal loads computations are accomplished by computer programs, rather than classical, hand-solution methods, pertinent data considered integral to the report shall be included as follows:
3.5.1An example of computer input and output with definitions
3.5.2Sufficient geometric views or computer-generated plots showing the computer model or finite element model
3.5.3Finite element model description (constraints, assumptions, nodes, degrees of freedom, etc.)
3.5.4Coordinate system origins and orientations of applicable local and global systems
3.5.5Node point locations and numbering
3.5.6Section property derivations
3.5.7Applicable material properties
3.5.8Element locations, numbering and types, with selection justification described
3.5.9Boundary constraints, with described justifications
3.5.10Applied loads
3.5.11Critical load cases (if structure is repetitive use most critical case)
3.5.12Types of applied stresses
3.5.13Special factors (fitting, bearing, casting, etc.)
3.5.14Realistic load paths that properly account for structure (holes, cutouts, etc.)
3.5.15Outputs of element forces, restraint forces and, where necessary, relative deflections
3.6Detailed stress analysis.
3.6.1The report shall describe all structural components analyzed, stating the type of construction, arrangement, materials, coordinate locations of load carrying members. The report shall provide adequate sketches to minimize the necessity of referring to drawings. All sketches shall include pertinent dimensions and shall be labeled by name and part number. Free-body sketches shall be provided to indicate applied loads, reactions, and boundary forces and constraints.
3.6.2The report shall describe the critical load cases and types of applied stresses.
3.6.3The report shall include calculations of stresses based on design ultimate loads. Where limit loads are more critical for material yield strength allowables, such calculations shall be shown. Allowable loads and stress calculations shall be shown or references listed. The analyses shall state the equations used and define the parameters within those equations prior to numerical solution. The report shall state factors used in the analysis such as but not limited to: fitting factors, casting factors, bearing factors, etc. The report shall list all margins of safety to adequately account for tensile, compressive, shear and torsional stresses, joint attachment strengths, beam column effects, crippling, panel buckling, and thermal stress effects. Substantiation of unconventional methods of analysis shall be included in the report by referencing the derivation source of unusual formulas.
3.6.4Loads and boundary conditions shall be clearly defined. The load path as it travels from the aircraft to the structure being analyzed shall be clearly identified. Perform yield checks at limit load for structures made from materials which yield strength is less than two-thirds of its ultimate strength, and margins of safety at limit load and at ultimate load, ensuring minimum margin of safety of 25% is used for critical structures that are not tested.
3.6.5All results shall be presented using a consistent coordinate system, and that system shall be clearly shown on all model and result plots.
3.6.6All repetitious and simple calculations should be omitted. One sample calculation shall be shown and the remaining results summarized by tabular or graphical form (such calculations should be stated as typical).
3.6.7Clearly define and display all mathematical variables used. Provide reference for analysis method, including equations, unless very simple or repetitious.
3.6.8Substantiate unconventional methods of analysis for accuracy and applicability by referencing the derivation source of unusual formulas. Specific page number, table, or figure of referenced material that has been adequately described by title, referenced data, which may be conveniently included within the report's list of references, shall be readily available to the procuring activity.
3.6.9Provide reasoning on conditions chosen for analysis.
3.6.10Examine stability of structure through crippling and buckling (free flange, inter rivet, column, lateral, torsional, panel, etc.).
3.6.11Include calculations for fastened joints (bearing, pullout, tear out, etc.).
3.6.12Consider secondary effects (compression wrinkling of sheets, diagonal tension in shear webs casing, increased fastener loads, etc.)If a computer program does not adequately account for joint attachment strength, combined loadings, local discontinuities and eccentricities, beam column effects, crippling, panel buckling, etc., a separate hand-solution analysis shall be performed to develop correct margins of safety.
3.6.13Include calculations of thermal stresses on structures that experience significant heating or cooling, whenever expansion or contraction is limited by external or internal constraints. Combine thermal stresses with concurrent stresses produced by other load sources.
3.6.14Include inherent residual stresses due to manufacturing/machining.
3.6.15For Finite Element Analyses (FEA), this section shall include a description of the mesh strategy, boundary conditions, load application, and convergence criteria. Where FEA results are used to compute margins of safety, a stress plot shall be provided with the maximum stress location and value noted on the figure. Information on how the FEA was validated must be provided (e.g. – hand analysis, test, etc.).
3.6.16The report shall include specific page numbers, tables, and figures of reference material used in the analyses.
3.7Analysis-static test correlation.Whenever prior, design development test measurements are available; the report shall include the correlation of those results with the report's analytically-determined values.
References
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