Abstract: Gray cast iron shows large asymmetrical features by the graphite flake when tensile and
compressive stresses are applied. The plastic strain rage which is used in low-cycle fatigue life
prediction by many researchers is hardly defined and gives very different values by the Standards in
this case. From the results of this study, it is not reliable to use the plastic strain range as a low-cycle
fatigue damage parameter. Therefore, the plastic strain energy density which is uniquely defined was
suggested as a damage parameter and it showed good correlation in low-cycle fatigue in gray cast
Abstract: Powder-metallurgical (P/M) produced components may be used as mass parts in a very large
quantity. Due to the multistage manufacturing process which consists of the pressing of the prepared
powder and the sintering of the green bodies also complex shaped components can be produced very
economically and precisely. They can be utilised without any further post-processing if the whole
production process is optimised. However, it is still difficult and only possible with considerable
technical and financial effort to produce highly stressable components profitably using the sinter
Therefore, the examinations on hand had the intention to create the basis for the use of the sinter
technology also for the production of highly stressable case-hardened components. To this, at first
bending specimens were fabricated with modern pressing procedures and sinter facilities and first
characterized in the as sintered state. Then the conditions for the case-hardening was analysed and the
parameters for an optimised case-hardening procedure fixed. With these parameters specimens were
case-hardened and their lifetime behaviour estimated under different bending loading conditions.
Finally it should be checked whether the knowledge gained from the specimens could be applied
to complex components. To this, gear wheels were produced using powder-metallurgy. The cyclical
tooth foot strength of this gear wheels were analysed in the only sintered as well as in the
case-hardened state. It could be demonstrated that the improvement of the fatigue strength of the
bending specimens by case-hardening also appears at the tooth foot strength of the gear wheels.
Abstract: In this paper the fatigue crack growth properties of a nitrided shot-peened steel is dealt
with: different peening intensities were considered and the resulting residual stresses measured by
means of an X-ray diffractometer. Rotating bending fatigue tests were executed on specimens with
a blind micro-hole, acting as a pre-existent crack. The results allowed determining the threshold of
propagation of the nitrided and of nitrided and shot peened material. It was also possible to relate
the crack initiation point with the applied and the residual stresses.
Abstract: Recent observations relevant to the early stages of the fatigue damage of crystalline
materials are reviewed. Experimental evidence on the localization of the cyclic plastic strain and on
the surface relief formation in cyclic loading of 316L austenitic stainless steel is presented. The
focused ion beam is used for exposing three-dimensional evidence of persistent slip markings
(PSMs). PSMs consist of extrusions and parallel or alternating intrusions which develop during
cyclic loading. Monte Carlo simulations of vacancy generation within persistent slip band (PSB)
and their migration to the matrix where they annihilate on the edge dislocations are used to simulate
the growth of extrusions and intrusions. The results of the simulations are compared with
experimental data and discussed in terms vacancy models of fatigue crack initiation.
Abstract: Cyclic strain control tests have been performed on cylindrical specimens of cast
polycrystalline Inconel 792-5A superalloy at 23, 500, 700 and 800 °C in laboratory atmosphere to
study the effect of temperature on the fatigue behavior. Cyclic hardening-softening curves and fatigue
life curves were measured. Scanning electron microscopy was used to investigate the surface relief.
Low amplitude straining was characterized by saturation of the stress amplitude. In room temperature
high amplitude straining cyclic hardening was followed by marked saturation. Pronounced
continuous hardening until failure was observed at 500 °C. Initial cyclic hardening was followed by
softening at 800 °C. A systematic shift of the Manson-Coffin and of the Basquin curves to lower
fatigue lives was found when temperature was increased. Fatigue cracks were observed to initiate
from surface slip markings at all temperatures.
Abstract: The technical development of construction equipment such as wheel loader leads to an
increase of not only amount of workload per hour, but also magnitude of allowable stress range.
Since welded structures of the wheel loader occupy approximately 40-60% of its total weight and
are subjected to incessant fatigue loads, fatal fatigue failures occur occasionally around the welded
zone during its practical operation in the field. To reasonably evaluate the fatigue life, the effect of
these geometries and welding residual stress on the fatigue life should be taken into account. In this
paper, the modified notch strain approach developed previously by the authors is applied practically
to assess the fatigue life of welded joints in boom and front frame structures of the wheel loader.
Abstract: The surface layer of binary Al-Zn alloy specimen, ever after a long time aging, remains
softer than the interior when the specimens are age-hardened at around room temperature after
quenching from high temperature. In this study, effects of the soft surface layer on the fatigue
strength of Al-Zn alloys were studied under repeated tensile loading. Vickers microharhness test
revealed that there existed less hardened region in the vicinity of grain boundary and specimens
surface, and that the region extends 50 to 100μm from the surface inward. From the plot of the
stress amplitude against the number of cycles to failure, it is concluded that the presence of less
hardened surface layer increases fatigue resistance of age-hardened Al-Zn alloys containing 8 to 16
mass%Zn under the repeated tensile loading.
Abstract: There are different documents containing fatigue crack propagation limit or design curves
and rules for the prediction of crack growth. The research work aimed to characterise the fatigue crack
propagation resistance of different materials using limit curves and determination of limit curves
under different loading conditions, based on statistical analysis of test results and the Paris-Erdogan
law. With the help of the characteristic values of threshold stress intensity factor range (Kth), two
constants of Paris-Erdogan law (C and n), fatigue fracture toughness (Kfc) or fracture toughness (KIc)
two reliable method can be proposed. The limit curves calculated by both methods represent a
compromise of rational risk (not the most disadvantageous case is considered) and striving for safety
(uncertainty is known).
Abstract: Recently a European community funded thematic network project (participation of 17
countries) FITNET (www.eurofitnet.org) has completed a new and unified engineering assessment
procedure (FITNET FFS Procedure) of flaws in metallic structures and welds. This newly
developed procedure (under CEN Workshop Agreement WA22) provides assessment rules for
flaws or damage due to fracture, fatigue, creep and corrosion to demonstrate the structural integrity
of the component. This paper gives an overview of the FITNET Fitness-for-Service (FFS)
Procedure and specifically presents the features and basic equations of the Fracture Module. It also
presents two brief examples for the validation of the procedure using laser welded specimens.
Abstract: If multiple discrete flaws are detected, alignment and combination rules are used to
determine whether the flaws should be treated as non-aligned or as coplanar, and independent or
combined flaws. Alignment and combination rules for multiple flaws are provided in
Fitness-for-Service (FFS) procedures of many codes and standards in the world. However, these
alignment and combination rules defined in the FFS are different. This paper aims to give overview
of alignment and combination rules for multiple flaws in FFS procedures. In addition, experimental
data on flat plates with parallel planar flaws are compared with the alignment rules of these FFS