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Strain based method to derive test rig loads for multi axial full scale tests

IP.com Disclosure Number: IPCOM000245101D
Publication Date: 2016-Feb-08
Document File: 3 page(s) / 22K

Publishing Venue

The IP.com Prior Art Database

Abstract

1. ABSTRACT keywords: multi axial, test rig, multi channel, airframe, fuselage, barrel test, full scale test In aircraft industry full scale tests are used to support the development of the airframe. In order to achieve the required ground and flight loads in the structural components, multiple hydraulic jacks and differential pressure are used. For all these test rig channels, the correct loads have to be found. The article proposes a method based on strains to derive these test rig loads.

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Page 01 of 3


1. ABSTRACT

keywords: multi axial, test rig, multi channel, airframe, fuselage, barrel test, full scale test

In aircraft industry full scale tests are used to support the development of the airframe. In order to achieve the required ground and flight loads in the structural components, multiple hydraulic jacks and differential pressure are used. For all these test rig channels, the correct loads have to be found. The article proposes a method based on strains to derive these test rig loads.


2. DISCLOSURE

Introduction

In aircraft industry full scale tests are used to support the development of the airframe. In order to achieve the required ground and flight loads in the structural components, multiple hydraulic jacks and differential pressure are used. For all these test rig channels, the correct loads have to be found. The article proposes a method based on strains to derive these test rig loads.

Problem description

During the development of an airframe, full scale static and fatigue tests are used to support the validation of sizing methods and the certification. These tests are performed with parts of the airframe like a fuselage barrel or the whole airframe. In order to achieve the required load distribution of the test article, a high number of hydraulic jacks are connected to the structure. For all jacks the correct forces have to be defined for each load case. Based on analytical or numerical models, the target loads are expressed in outer loads like forces and moments.

The calculation of the jack loads is a time consuming procedure. Moreover, as the model of the test rig might not reflect every detail of the test set-up and the load introduction, a deviation between the calculated target loads and the achieved loads is not unusual. In this case, the jack loads have to be adapted.

Strain based method

In nowadays, detailed FEM models are used for the sizing of airframe components. Strain gauges which are applied to the test article, are implemented in the FE model as well in order to compare the calculated strains (target) with the measured strains (achieved). As the desired strains are known from the detailed airframe FEM, the idea is to take the known strain distribution as a target when finding the correct test rig loads.


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For this, all hydraulic jacks or all test rig channels like differential pressure are loaded separately like unitary load cases in a FEM model. For example, when having a test rig with 20 channels, 20 unitary load cases are applied to...