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Fundamentals of Fatigue Analysis

  • Professional Development
  • C1875
Published 2019-11-26

Fatigue is a structural failure mode that must be recognized and understood in order to develop products that meet life cycle durability requirements. Fatigue strength is an important design requirement in any new vehicle, particularly in the age of lightweighting as engineers struggle to meet stringent weight requirements without adversely impacting durability. This technical concept course provides an introduction to the fatigue failure mode and analysis methods. Attendees will learn about the physics of material fatigue, including damage accumulation which over time may progress to product failure. Attendees will also learn about fatigue analysis methods such as stress-life (SN), strain-life (EN), and crack growth, investigating the assumptions and applicability of each. This course includes example problems which are solved by hand calculation, exploring and reinforcing key concepts. Emphasis is placed on the practical aspects of these concepts and methods so attendees are prepared to put this knowledge into action. This course is popular with both experienced analysis engineers and with engineers transitioning into a durability or analysis role as it provides the needed foundation to develop effective fatigue prediction capabilities.

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General Requirements for Powered Drive Units (PDUs) in Aircraft Cargo Systems

AGE-2 Air Cargo
  • Aerospace Standard
  • AIR4165B
  • Current
Published 2019-10-02 by SAE International in United States
This SAE Aerospace Information Report (AIR) is intended to assist the user (aircraft manufacturer/airline) in the following areas: a In the decision of whether or not to plan for the installation of a powered drive system in the cargo loading system (CLS) during the definition of the aircraft on-board cargo loading system. b If a powered drive system is decided upon, to provide general requirements to be considered during the preparation of component specifications for the powered drive units (PDUs) to be used. This provides a selection of criteria in order to obtain an optimum PDU for the application considered.
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Materials Degradation in Mechanical Design: Wear, Corrosion, Fatigue and their Interactions Web Seminar RePlay

  • Webinar Recordings
  • PD331722
Published 2019-09-19

Materials degradation from environmental conditions is a common factor that will often occur in mechanical equipment used in every type of environment. These processes can frequently materialize in unpredicted and harmful ways, especially when they interact and lead to early component damage or failure.

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Requirements for Plastic Encapsulated Discrete Semiconductors in Space Applications

CE-12 Solid State Devices
  • Aerospace Standard
  • AS6294/3
  • Current
Published 2019-08-07 by SAE International in United States
This document establishes the requirements for screening, qualification, and lot acceptance testing of Plastic Encapsulated Discrete Semiconductors (PEDS) for use in space application environments. The scope of this document is intended for standard silicon based technology only, but the process and methodology described within can be adopted for other technologies such as Silicon Carbide, Gallium Nitride, and Gallium Arsenide. However, when non-silicon based technology parts are being used, the device characterization shall be modified, and it is recommended to use available industry standards based upon published research/testing reports for those technology to address applicable physics of failure.
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Peridynamic Modeling: An Alternative Approach to Analyzing Material Failure

  • Magazine Article
  • TBMG-34871
Published 2019-08-01 by Tech Briefs Media Group in United States

A critical technology challenge for structural material applications in the aerospace and defense industries is to have a means for the reliable analysis of material damage and failure. Experimental structural assessments are typically expensive and often do not provide full information about coupled, multiscale damage processes. Computer-aided analysis has established itself as a useful tool for complementing experimental structural assessments. A comparative summary of current computer-aided approaches is presented in the accompanying table.

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Oxygen Cylinder Installation Guide

A-10 Aircraft Oxygen Equipment Committee
  • Aerospace Standard
  • ARP5021B
  • Current
Published 2019-04-11 by SAE International in United States
This document provides guidance for oxygen cylinder installation on commerical aircraft based on airworthiness requirements, and methods practiced within aerospace industry. It covers considerations for oxygen systems from beginning of project phase up to production, maintenance, and servicing. The document is related to requirements of DOT-approved oxygen cylinders, as well to those designed and manufactured to standards of ISO 11119. However, its basic rules may also be applicable to new development pertaining to use of such equipment in an oxygen environment. For information regarding oxygen cylinders itself, also refer to AIR825/12.
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ASIL-Decomposition and Related DFA for Autonomous Driving Systems

Universität Stuttgart - IVK-Hans-Christian Reuss
ZF Friedrichshafen AG-Bülent Sari
Published 2019-04-02 by SAE International in United States
According to ISO 26262, ASIL decomposition is the breakdown of a top level safety requirement derived from safety goal into redundant safety requirements with sufficient independence to achieve the safety goal independently. The usage of decomposition enables the opportunity to reduce the ASIL rating of the decomposed safety requirements of a safety goal. To apply decomposition, the decomposed safety requirements should be allocated to sufficiently independent architectural elements. If the redundant/decomposed safety requirements cannot be allocated to sufficiently independent architectural elements, then these redundant safety requirements inherit the initial ASIL of the safety goal. ASIL decomposition can be applied to the functional, technical, hardware or software safety requirements of the item.This paper discusses, how the decomposition approach from ISO 26262 can be applied for autonomous driving (AD) systems considering processing chain from sensors such as camera, radar, LIDAR, etc. to perception algorithms and decision algorithms which are executed in high performance chips. In addition, this research provides different solutions for the extension of dependent failure analysis considering SOTIF-related technological shortcomings.
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A Dynamic Fault Tree Approach for Time-Dependent Logical Modeling of Autonomous Flight Systems

Cobham Mission Systems Inc-John Wang
Published 2019-03-19 by SAE International in United States
This paper addresses the urgent need for adequate methodologies to use in analyzing autonomous flight systems, including Unmanned Aircraft. These systems are inherently dynamic and require analysis that is explicitly time dependent. Autonomous flight systems are becoming more commonly used, especially for Part 23 aircraft including Business (Corporate) and Regional Jets or Unmanned Aircraft deployed in hazardous environment/situation. Such systems are expected to make their own decisions under uncertain conditions caused by potential system structure changes when entering a new flight phase or switching to a new system configuration due to system degradation or failure(s) [1]. This paper highlights significant modeling errors that can arise in analyzing dynamic scenarios where these time dependencies are ignored. Model-based solutions are provided by incorporating a time-dependent algebraic formalism into Fault Tree Analysis (FTA) and Dependency Diagram (DD) with updated descriptions in SAE ARP4761A and ARP4754B (Note: These are currently under development). A Dynamic Goal Tree (or alternatively, a Dynamic Dependency Diagram) provides an effective implementation of the time-dependent logic for dynamic system analysis analyzing autonomous flight systems which…
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Delamination and Porosity in Composites and Adhesives Using Solid and Particulate Powdered Aerogel

  • Magazine Article
  • TBMG-33925
Published 2019-03-01 by Tech Briefs Media Group in United States

NASA's Langley Research Center has developed a method that introduces solids and particulates — specifically aerogels — into composites or adhesives while they are being constructed. These additives survive as the structure is cured to serve as a testbed and standard. Once cured, the solid or particulate additive will behave as a delamination or porosity defect and will be indistinguishable from real delamination or porosity when inspected with popular nondestructive evaluation techniques such as ultrasound or thermography.

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Field Failure Simulation of a Non-reactive Suspension Tie Rod for Heavy Commercial Vehicle Using a Road Simulator

Ashok Leyland Ltd-Dinesh Kumar Rajappan
Ashok Leyland Technical Center-Agathaman Selvaraj, Benny Johnson William, Manikandan Rajaraman, Srinivasa Chandra Vadlamudi
Published 2019-01-09 by SAE International in United States
The suspension system in a vehicle isolates the frame and body from road shocks and vibrations which would otherwise be transferred to the passengers and goods. Heavier goods vehicles use tandem axles at the rear for load carrying. Both the axles should be inter-connected to eliminate overloading of any one axle when this goes over a bump or a ditch. One of the inter-connecting mechanism used is leaf spring with tie rod, bell crank & linkages, when the first rear axle moves over a bump, the linkages equalize the loading on the second rear axle.This paper details about the failure analysis methodology to simulate the tie rod field failure using a six poster road simulator and to identify the root cause of the failure and further corrective actions. The methodology involves the study of field usage conditions and the nature of failure, strain gauging and instrumentation of tie rod, strain and load analysis on tie rod at various conditions, various experiments to re-create or simulate the failure, identification of failure modes and root cause analysis.…
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