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In the X-ray diffractometer an X-ray
beam is produced which strikes the sur-
face of the sample. The beam is reflect-
ed by the lattice planes of the crys-
talline structure. By means of the rela-
tive position of the X-ray peaks it is
possible to decide whether it is a case
of lattice expansion (tensile stresses)
or lattice deformation (compressive
stresses). The X-ray diffractometer pro-
vides both residual stress values and
half-width values, which represent a
measurement for the hardness or, as
the case may be, the dislocation struc-
ture of the component. The residual
stress values can be represented as a
depth profile which is created by means
of electrolytic etching or as polar dia-
grams. The polar diagrams provide in-
formation about the directional depen-
dence of the residual stress values (im-
portant in relation to the presetting of
springs, for example).
The cylinder-head testing stand
driven by a electromotor
First of all a strain gauge is adhered
to a spring which is then fitted into the
valve trains provided by the customer.
Throughout a range of different r.p.m.
speeds, the stress is then measured in
the non-fired electromotor. By means of
a measurement-data collection system,
the representation of the stress
throughout the r.p.m. range makes the
dynamic behaviour in the form of cases
of excessive stress visible. The mea-
surement of the stresses under load us-
ing strain gauges is an application-ori-
ented examination. It is aimed at select-
ing the valve-spring dimensioning best-
suited to the type of camshaft in hand.
Rotating-bending machines
The rotating-bending test, also known
as the Nakamura test, involves a cyclic,
rotational bending of wires at a maxi-
mum of 5,000 r.p.m. in order to ascer-
tain the fatigue strength of the material
in its initial state. By means of this test
it is possible to detect non-metallic in-
clusions in shot-peened bars or sur-
face defects in non-shot-peened bars.
Depending on the aim in question, this
process requires up to 100 million cy-
cles. On account of the large amount of
time needed, this type of test is not so
suitable for a routine, incoming material
examination. However, it is a decisive
factor in the setting up of new supply
chains. With its in-house machine-build-
ing department, SCHERDEL manufac-
tures rotating-bending machines itself
and also sells them to wire suppliers.
Finally it should be mentioned that the
Research & Fundamental Development
Department provides a whole range of
technical services for customers as
well. Corrosion tests, surface examina-
tions, chemical analyses, fatigue tests
and the whole range of topics connect-
ed with metallography, combined with
the exceptional knowledge of the staff,
are at the disposal of external cus-
tomers.
(dk)
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LOCATIONS -
TECHNOLOGY & PRODUCT DEVELOPMENT
- NEWS AND INFORMATION
Materials testing
Contact
SCHERDEL
INNOTEC Forschungs-
und Entwicklungs-GmbH
Scherdelstraße 2
D-95615 Marktredwitz
Germany
Dr. Gisela Barthold
Head of Research &
Fundamental Development
Phone +49 9231 603-525
e-mail:
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