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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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Failure Analysis and Multi Frequency Swept Sine Testing of Automotive Engine Oil Sump

Ashok Leyland Ltd.-Obuli Karthikeyan Narasimman, Raguram Mohan, Sriraman Srinivasan, Karthik Lakshminarayanan, Srinivasa Chandra Vadlamudi
Published 2019-01-09 by SAE International in United States
Automotive business is more focused towards delivering a highly durable and reliable product at an optimum cost. Anything falls short of customer expectation will ruin the manufacturer’s reputation. To exterminate this, all automotive components shall undergo stringent testing protocol during the design validation process. Nevertheless, there are certain factors in the field which cannot be captured during design validation. This paper aims at developing a validation methodology for engine oil sump by simulating field failure. In few of our vehicles, field failure was observed in engine oil sump near the drain plug location. Preliminary analysis was carried out to find the potential causes for failure. Based on the engine test bed results, multi frequency swept sine testing was carried out in laboratory. Field failure was simulated in the lab test and the root causes for failure were found out. After the design modification, new oil sump samples were validated and achieved an improved life over the earlier design.
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Effect of Ambient Temperature and Inflation Pressure on Tire Temperature

Automotive Research Association of India-Shreyas Bharadwaj, Vyankatesh Khairatkar
Published 2019-01-09 by SAE International in United States
Tire failure is identified as a major cause of accidents on highways around the world in the recent past. A tire burst leads to loss of control of the vehicle which ends up in a catastrophe. There are various factors which are accounted for a tire burst. Heat buildup, aging of tire and cracks on tires are the major ones which are identified. A superior ability of the tire to dissipate the heat generated during operation is a major factor which prevents a tire failure. Other factors such as ambient temperature, inflation pressure etc. contributes to heat buildup which may ultimately result in tire failure. A combination of these factors might manifest as a tire failure at high speeds, the latter being an immediate cause of heat buildup. A dormant crack in the tire might develop if the temperature and pressure conditions are favorable, thus giving away at the weakest point. With regard to the temperature conditions, road conditions, inflation pressure checks etc. India is vulnerable to tire failures. It may be noted that present…
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Adhesive Failure Prediction in Crash Simulations

Tata Motors Ltd.-Sivaprasad Koralla, Debabrata Ghosh, Susanta Dey
Tata Technologies Ltd.-Hrishikesh S. Rao, Sourabh Tiwari
Published 2019-01-09 by SAE International in United States
Structural adhesive is a good alternative to provide required strength at joinery of similar and dissimilar materials. Adhesive joinery plays a critical role to maintain structural integrity during vehicle crash scenario. Robust adhesive failure definitions are critical for accurate predictions of structural performance in crash Computer Aided Engineering (CAE) simulations.In this paper, structural adhesive material characterization challenges like comprehensive In-house testing and CAE correlation aspects are discussed. Considering the crash loading complexity, test plan is devised for identification of strength and failure characteristics at 0°, 45°, 75°, 90°, and Peel loading conditions. Coupon level test samples were prepared with high temperature curing of structural adhesive along with metal panels. Test fixtures were prepared to carryout testing using Instron VHS machine under quasi-static and dynamic loading.Various material models available in LSDYNA are studied and MAT169 (*MAT_ARUP_ADHESIVE) material model is selected for adhesive material characterization. Finite Element (FE) models inline to the test conditions were prepared. Sensitivity studies carried out to understand the significance of critical parameters in material model and modelling practices. Test and CAE correlation…
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Validating Requirements and Improving Specifications with Telematics Data

  • Professional Development
  • C1897
Published 2018-12-19

Field failures cause high warranty expenses, perhaps the highest quality cost. Failures occur when new designs are introduced, existing products are sold in new markets, and product specifications don’t reflect actual product usage. Any mistake in product specifications affects the entire product development process and cascades through the supply chain.