A new test procedure to validate tensile dynamic mechanical properties of sheet metals and alloys in automotive crash applications

A thin walled open channel beam subjected to a 3-point bend and constant velocity boundary condition is investigated to establish its potential to validate material performance for automotive crash applications. Specifically quantitative validation of material data determined from high speed tensile testing and qualitative validation of material resistance to fracture in crash components. Open channel beams are fabricated from structural grade sheet steel and aluminium alloy and tested at quasi-static and higher speeds up to 10 m/s and in all cases, deformation develops a plastic hinge. This paper describes development of the validation test procedure, specifically design of specimen, system of measurement and boundary conditions using numerical and experimental techniques. The new test procedure will increase confidence in materials modelling and reduce the risk to introduce new advanced high strength materials into automotive crash structures

Modelling self-piercing riveted joint failures in automotive crash structures

This paper describes a new model and method to predict Self-Piercing Riveted (SPR) joint interlock failures in aluminium sheet at crash speeds using explicit finite element simulation. SPR interlock failure is dependent on rivet direction, which is included in the model. A mesh independent approach is adopted for connection model which is capable of industrial application at the full vehicle crash analysis level. The paper provides an overview of the approach to validate connection model; typically by developing detailed physics based models of various joint configurations supported with high speed experimental data, through to model capable of industrial application. The framework to validate connection model for use in crash simulation tools is expected to have broader applicatio

Validating dynamic tensile mechanical properties of sheet steels for automotive crash applications

A thin-wall open channel beam, fabricated from high strength Dual Phase sheet steel, subjected to 3-point bending and constant velocity boundary condition, is investigated to validate material performance for automotive crash applications. Specifically quantitative validation of material tensile data determined from high speed tests and component models, and qualitative validation of materials resistance to fracture. The open channel beam is subjected to quasi-static and increasing loading speed and in all cases, large displacement in which deformation involves formation of a plastic hinge. This paper describes development of test procedure, notably beam specimen design, measurement system and boundary conditions, using both experimental and numerical techniques. The new test procedure, as a compliment to crush testing, will increase confidence in the modeling and application of new advanced higher strength materials in automotive crash structure

Validating performance of automotive materials at high strain rate for improved crash design

This paper investigates sources of performance variability in high velocity testing of automotive crash structures. Sources of variability, or so called noise factors, present in a testing environment, arise from uncertainty in structural properties, joints, boundary conditions and measurement system. A box structure, which is representative of a crash component, is designed and fabricated from a high strength Dual Phase sheet steel. Crush tests are conducted at low and high speed. Such tests intend to validate a component model and material strain rate sensitivity data determined from high speed tensile testing. To support experimental investigations, stochastic modeling is used to investigate the effect of noise factors on crash structure performance variability, and to identify suitable performance measures to validate a component model and material strain rate sensitivity data. The results of the project will enable the measurement of more reliable strain rate sensitivity data for improved crashworthiness predictions of automotive structures

Validating material information for stochastic crash simulation

This paper describes the steps in validating material information for stochastic simulation using a quasi static tensile test experiment Sources of physical noise usually present in a testing environment such as variation in material properties, geometry and boundary conditions are included as inputs to finite element models

Strain Rate Testing of Metallic Materials and their Modelling for use in CAE based Automotive Crash Simulation Tools : Recommendations and Procedures

The aim of this book is to provide guidelines to generate tensile strain rate test data for ferrous and non-ferrous sheet metals for use in finite element based automotive crash simulation tools. Specifically, measurement of the strength hardening in a sheet material resulting from strain rate testing using a high speed servo hydraulic test machine. Additionally, to provide guidelines to process raw test data, fit material model and format this data for application in crash simulation tools. It is not within the scope of these recommendations to advocate a material model to fit to strain rate test results, although useful models are referenced. Rather to give guidance on the error allowance in fitting model to test results. These guidelines are expected to have broader application in the transport industry sector

Reducing performance variation of compression moulded long glass fibre reinforced thermoplastics by targeted reinforcement

Long glass fibre compression mouldings are prone to significant variations in mechanical properties. Stiffness and strength tend to vary across an individual moulding and in addition there are also variations when different mouldings arc compared. Compression mouldings in the form of a top hat section were produced. This component was first modified to have ribs, then samples of both batches were reinforced with a thin thermoplastic composite plate with continuous fibres. In this way, four different batches were produced, which were tested under 3-point-bending. Further, this work investigated the changes in mechanical properties across the manufactured top hat section mouldings. Tensile test results strongly indicate that the scatter of mechanical properties increases towards the edges of the compression moulding. When the mouldings were tested under 3-point-bending, the experimental results were prone to a large scatter and it was not possible to predict the position of failure or the failure mode. However, this work successfully demonstrated that a targeted reinforcement of the moulding with continuous fibres can significantly reduce the performance variations, particular under loading with large strain. The findings of this work could lead to the development of new lightweight structural components, where there is a need for integrating functions into the moulding in order to reduce weight and costs for mass production

Development of bend-impact test procedure to validate dynamic tensile mechanical properties of sheet metals and alloys for automotive crash applications

This paper examines the development of bend-impact test procedure to validate dynamic tensile mechanical properties of sheet metals and alloys for automotive crash applications

Erroneous intracranial pressure measurements from simultaneous pressure monitoring and ventricular drainage catheters

The objective of this report is to highlight the potential for false pressure measurements from systems that combine intracranial pressure (ICP) measurement and ventricular drainage. If the ports of the drain become blocked to the extent that they present a high resistance to cerebrospinal fluid flow, then a significant pressure gradient between the inside and outside of the catheter may be established. Thus, any intracatheter transducer will faithfully record a pressure much lower than true ICP. This holds true for catheter-tip transducers when the transducer lies inside the catheter. In the absence of flow, however, pressures will equalize; therefore, accurate measurements may be taken if the drain is temporarily closed. We model this situation and provide simulations of expected measurements in such situations; these compare well to observed clinical readings.</p