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