2009-05-08 Tehnomus 15 Suceava Rotating Bending Machine for High Cycle Fatigue Testing

7/28/2019 2009-05-08 Tehnomus 15 Suceava Rotating Bending Machine for High Cycle Fatigue Testing

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Rotating bending machine forRotating bending machine for

high cycle fatigue testinghigh cycle fatigue testing

D. Brandolisio, J. Symynck, F. De Bal

Department of Mechanical EngineeringLaboratory of Material Testing

KaHo Sint-Lieven University College, GentAssociation KULeuven


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Aim of the projectAim of the project

- realisation of a rotating bending (RB) machine for high cycle fatiguetesting (HCF)

cover most of the machines in the market

- force range

- rotational speed

- dimensional flexibility

controllable

- parameters

- data acquisition


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Motives of the projectMotives of the project

1 - Additional method for fatigue testing in the laboratory

alternative way of investigation

- scientific publication:

On the difference of fatigue strengths from rotating bending, four-

point bending, and cantilever bending tests

( on Fatimat's website: http://mechanics.kahosl.be/fatimat/ )
http://mechanics.kahosl.be/fatimat/http://mechanics.kahosl.be/fatimat/


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2 - High cycle fatigue testing for SME (Small and Medium Enterprises)

HC testing

SH (ServoHydraulic) OK

EM (ElectroMechanical) SLOW

BUT

solution: EM + rotation


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Rotating Bending Fatigue TestRotating Bending Fatigue Test

Definition

- application of a known constant bending stress to a round sample of the

material, combined with the rotation of the sample around the bending

stress axis until its failure.

bending stress due to bending moment


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y=M

Jy

J=d4

64

- bending stress

- area moment of inertia

ymax=d2

Main formulae


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In the paper:

comparison different methods for fatigue testing

- cantilever bending (two-points)

- four-points bending

- four-points rotating bending


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weakest point (failure initiation)

- RB all external section always

- other B tests only extreme points may or may not

RB test other bending tests


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- cyclical fluctuation of stress in RB


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Advantages of RB test:

more accuracy

less scatter in results

less specimens for test

Disadvantages in RB test:

only axialsymmetrical specimens

difficulty in non-zero mean stress


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- two types of RB test

4 points bending 2 points bending

constant moment triangular moment


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- machines in the market


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- basic scheme 4 points RB machine


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Specification of components

clamping system

- precise

- adaptable


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bearings displacement

- axial displacement forpure bending


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Specimen for RB test

- ISO 1143

- tolerances

- smoothness


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- other geometries

- easier (cheaper) realisation


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Loading condition

- in real life:

from random to constant amplitude blocks


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- common machines:

- static load variation (deadweights)

- difficulty in load setting


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importance ofoverload and underload conditions

- scientific publication:

Effect of compressive underloads and tensile overloads on fatiguedamage accumulation in SAE 1045 Steel

- overloads and underloads in cumulative damage

alteration of specimen's life


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idea:

- application ofvariable and controlled load

- automatic variation

- dynamic switching


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Project's choicesProject's choices

Zwick-Roell Z020 electromechanical actuator for loading

- adjustable

- controlled ( testXpert II)


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4 points RB test

- constant moment inside the specimen

- easier specimen's realisation

collet clamping system

- precise

- resistant

- adaptable

- not expensive


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Spreadsheets

use of main formulae for

- stress on the surface

- specimen's curvature

- axial displacement

- optimum moment's arm

- shaft's critical dimensions


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3D Models3D Models

frontal view of the machine


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section view

load bearing detail view


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support bearing detail view

support section view


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general view with Zwick/Roell Z020


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Control of the machineControl of the machine

- magnitude of load Zwick/Roell testXpert II

- rotational speed controller

- cycle counting I/O module

- moment's arm variation - displacement sensor

- Spider8

- Catman


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Control scheme


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ConclusionsConclusions

- RB valid test for fatigue behaviour

- reliable

- simple

this projectthis project

- support for SME

- study and research possibility

2009-05-08 Tehnomus 15 Suceava Rotating Bending Machine for High Cycle Fatigue Testing

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