Laser Hardening Parameters Influencing Component Lifetime and Residual Stresses

2014 ◽  
Vol 782 ◽  
pp. 306-310 ◽  
Author(s):  
Stanislav Němeček ◽  
Michal Míšek ◽  
Ivo Černý ◽  
Jiří Sís ◽  
Nikolaj Ganev ◽  
...  
Keyword(s):  
Laser Beam ◽  
Fatigue Resistance ◽  
Industrial Applications ◽  
Laser Hardening ◽  
Fatigue Properties ◽  
Basic Material ◽  
Material Surface ◽  
Comprehensive Knowledge ◽  
Key Words Laser ◽  
42Crmo4 Steel

Laser surface hardening is an advanced method of surface treatment of structural steels with a great potential for wide industrial applications. The technology is quite new and so, investigations have to be performed in order to gain a comprehensive knowledge about effects on microstructure, hardness, surface properties of treated materials, but also mechanical an particularly fatigue properties. Concerning fatigue resistance of material treated with this technology, results and knowledge recently published in the literature indicate that fatigue resistance can be either reduced or increased, even considerably, depending on numerous parameters of basic material, laser hardening parameters etc. This contribution contains results of a partial study of effect of laser hardening of relatively small specimens on fatigue resistance of 42CrMo4 steel. Two different parameters of the treatment were used, namely two speeds of laser beam on the material surface at constant beam energy. Unlike the lower speed, when fatigue resistance was slightly reduced, higher speed of laser beam resulted in a slight increase of fatigue resistance and fatigue limit. The results are discussed considering an occurrence of residuals stresses. Key words: Laser hardening, residual stress, lifetime, fatigue, fracture, microstructure, surface

An Effect of Surface Laser Hardening on Deformations and Fatigue Properties of 42CrMo4 Steel Specimens

2013 ◽  
Vol 486 ◽  
pp. 54-57
Author(s):  
Ivo Černý ◽  
Jiří Sís
Keyword(s):  
Residual Stresses ◽  
Laser Treatment ◽  
Fatigue Resistance ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Laser Hardening ◽  
Small Samples ◽  
Fatigue Properties ◽  
Basic Material ◽  
Subsurface Layers

Laser hardening is an advanced method of surface heat treatment with wide possibilities of industrial applications. Considering the fact that this technology is fairly new and is being developed, knowledge about effects on properties of materials treated by this technology are still limited, particularly from the viewpoint of mechanical and particularly fatigue properties. As a dependence of numerous parameters of the treatment, basic material and its state and also size of treated pieces or specimens, not only substantial changes of microstructure in the surface and subsurface layers occur, but also residual stresses and connected deformations. Results of an experimental investigation of effects of laser treatment with selected parameters on deformations and fatigue resistance of relatively small samples of 8 x 8 mm cross section are presented and discussed in this work. Effects of surface speed of the laser beam was evaluated, then effects of fixation of the specimens to rigid supporting steel plate on changes of deflection caused by the laser treatment and eventually, changes of the deformations after releasing the specimens from the supporting plate. Results are in a good agreement with residual stress measurements. Fatigue tests indicated possibilities of favourable effects of laser treatment on fatigue resistance. Results are discussed considering an occurrence of inclusions in the material, residual stresses and fatigue damage mechanisms.

Evaluation of Fatigue Strength of Heat Treated and Laser Hardened 42CrMo4 Steel Considering Localized Initiation Mechanisms

2014 ◽  
Vol 606 ◽  
pp. 31-34
Author(s):  
Ivo Černý ◽  
Jiří Sís ◽  
Dagmar Mikulová
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Resistance ◽  
Fatigue Crack Initiation ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Laser Hardening ◽  
Basic Material ◽  
Heat Treated ◽  
42Crmo4 Steel

Laser surface hardening is an advanced method of surface treatment of structural steels with a great potential for wide industrial applications. According to the recent literature results and knowledge about laser hardening, fatigue resistance can be either reduced or increased, even considerably, depending on numerous parameters of basic material, the technology parameters etc. This contribution contains results of a partial study of effect of laser hardening of relatively small specimens on fatigue resistance of 42CrMo4 steel. Two different parameters of laser hardening were used, one of them resulted in considerable longitudinal residual stresses surface speed of laser beam 4 mm/s. Results of fatigue tests of basic reference material had a surprisingly high, atypical scatter, particularly in the region near fatigue limit. Fractographical analyses indicated that this scatter was connected with presence of single inclusions, even quite large, which in some cases caused fatigue crack initiation. Compressive residual stresses after the laser treatment improved fatigue strength and reduced the scatter, likely due to short crack retardation in the compressive residuals tress field. Further analyses and discussion are provided using Murakami method of fatigue life evaluation of materials containing defects.

An Effect of Laser Hardening on Contact and Bending Fatigue of a 42CrMo4 Steel

2015 ◽  
Vol 665 ◽  
pp. 221-224 ◽  
Author(s):  
Ivo Černý ◽  
Ivan Fürbacher ◽  
Dagmar Mikulová ◽  
Jiří Sís
Keyword(s):  
Fatigue Resistance ◽  
Contact Fatigue ◽  
Laser Hardening ◽  
Bending Fatigue ◽  
42Crmo4 Steel ◽  
Surface Laser ◽  
Point Bend ◽  
Gear Wheels ◽  
Contact Fatigue Resistance

The paper deals with an investigation of surface laser hardening characteristics on contact and bending fatigue resistance of a 42CrMo4 steel, being often used for manufacture of gear wheels. The aim of the experimental programme was to simulate the complex service loading of fairly large gears by two separate investigations, namely contact fatigue performed on a special, so called analogon machine and bending fatigue performed on high cycle fatigue resonance machines using three-point-bend (3PB) fairly large specimens. It was shown that after optimising the methodology and parameters of the laser hardening technology, contact fatigue resistance is very good, comparable with very expensive and time consuming thermochemical high-depth surface treatments. Bending endurance limit can be increased. The role of residual stresses resulting from the laser treatment was shown as decisive.

scholarly journals CHANGES IN FATIGUE RESISTANCE OF STRUCTURAL STEELS AT DIFFERENT LOADING SPECTRA

2019 ◽  
Vol 62 (10) ◽  
pp. 796-802
Author(s):  
V. V. Myl’nikov ◽  
D. I. Shetulov ◽  
O. B. Kondrashkin ◽  
E. A. Chernyshov ◽  
A. I. Pronin
Keyword(s):  
Fatigue Resistance ◽  
Resistance Index ◽  
Fatigue Curve ◽  
Cyclic Strength ◽  
Structural Steels ◽  
Experimental Results ◽  
Cyclic Behavior ◽  
Material Surface ◽  
Loading Frequency ◽  
Surface Layers

Fatigue strength of widely used engineering structural steels was  studied at various frequencies of loading according to the scheme of  cantilever bending of the rotating cylindrical samples. Fatigue resistance index is tangent of angle of inclination of fatigue curve to axis  of longevity. It is established that 40 and 45 steels belong to the group  of materials in which decrease in frequency of loading leads to cyclic  softening and decrease in fatigue resistance, which is numerically expressed by increasing slope of fatigue curve. Tests of the samples made  of 40X steel had shown that increase in frequency of loading cycles  leads to a noticeable decrease in slope of fatigue curve parameter, i.e.  to an increase in fatigue resistance. Decrease in fatigue resistance parameter is associated with an increase in hardening of material of the  samples (parts) surface layers which reduces fatigue damage to the  surface itself. Dependence of the fatigue curve slope tangent on surface damage at changing loading cycles frequency is shown and it is  stated that, regardless of frequency, damage of material surface layers  increases along the slope of fatigue curve. For each of these groups  mathematical relations are defined. The correlation coefficient providing degree of convergence of experimental results with the constructed fatigue curve was adopted as a criterion of cyclic behavior stability  of steels. It is revealed that increase in behavior stability of 40X steel  is observed with increase in cyclic deformation rate. Tests of 45  steel  have shown that decrease in cyclic strength with increase in loading  frequency does not affect fatigue stability of material. Increased dispersion of experimental results was observed in 40 steel at low loading  frequency, despite the high values of cyclic strength at given loading  frequency. On the basis of conducted experiments, dynamics of behavior of real machine parts and structures subjected to cyclic loads  operating was determined in the studied loading spectrum.

Enhanced fatigue resistance and lattice dynamics induced by the strong local strain in Fe-doped KTa1-xNbxO3 single crystal

2021 ◽  
Author(s):  
Xiaolin Huang ◽  
Peng Tan ◽  
Yu Wang ◽  
Yao Zhang ◽  
Xiangda Meng ◽  
...  
Keyword(s):  
Single Crystal ◽  
Fatigue Resistance ◽  
Lattice Dynamics ◽  
Piezoelectric Materials ◽  
Local Strain ◽  
Lead Free ◽  
Fatigue Properties ◽  
Practical Applications ◽  
Local Structures ◽  
The Impact

Improvement of durability is greatly important for the practical applications of lead-free-doped piezoelectric materials. However, the promotional mechanism of anti-fatigue properties and the impact on local structures from ion dopants...

Diaphragm muscle fatigue resistance during postnatal development

1991 ◽  
Vol 71 (2) ◽  
pp. 458-464 ◽  
Author(s):  
G. C. Sieck ◽  
M. Fournier ◽  
C. E. Blanco
Keyword(s):  
Postnatal Development ◽  
Fatigue Resistance ◽  
Muscle Fibers ◽  
Diaphragm Muscle ◽  
Fatigue Properties ◽  
Type I ◽  
Type Ii ◽  
Cross Sectional ◽  
Type I Fibers ◽  
Type Ii Fibers

postnatal development. Both twitch contraction time and half-relaxation time decreased progressively with age. Correspondingly, the force-frequency curve was shifted to the left early in development compared with adults. The ratio of peak twitch force to maximum tetanic force decreased with age. Fatigue resistance of the diaphragm was highest at birth and then progressively decreased with age. At birth, most diaphragm muscle fibers stained darkly for myofibrillar adenosinetriphosphatase after alkaline preincubation and thus would be classified histochemically as type II. During subsequent postnatal development, the proportion of type I fibers (lightly stained for adenosinetriphosphatase) increased while the number of type II fibers declined. At birth, type I fibers were larger than type II fibers. The size of both fiber types increased with age, but the increase in cross-sectional area was greater for type II fibers. On the basis of fiber type proportions and mean cross-sectional areas, type I fibers contributed 15% of total muscle mass at birth and 25% in adults. Thus postnatal changes in diaphragm contractile and fatigue properties cannot be attributed to changes in the relative contribution of histochemically classified type I and II fibers. However, the possibility that these developmental changes in diaphragm contractile and fatigue properties correlated with the varying contractile protein composition of muscle fibers was discussed.

Abrasive Blasting, a Technique for the Industrial Decontamination of Metal Components From Decommissioning to Unconditional Release Levels

2001 ◽  
Author(s):  
Robert Walthéry ◽  
Lucien Teunckens ◽  
Patrick Lewandowski ◽  
Danny Millen ◽  
Sven Baumann
Keyword(s):  
Radioactive Waste ◽  
Waste Treatment ◽  
Unit Cost ◽  
Radioactive Wastes ◽  
Basic Material ◽  
Material Surface ◽  
Health Physics ◽  
Global Cost ◽  
Physics Department ◽  
Abrasive Blasting

Abstract When decommissioning nuclear installations, large quantities of metal components are produced as well as significant amounts of other radioactive materials, which mostly show low surface contamination. Having been used or having been brought for a while in a controlled area marks them as ‘suspected material’. In view of the very high costs for radioactive waste processing and disposal, alternatives have been considered, and much effort has gone to recycling through decontamination, melting and unconditional release of metals. In a broader context, recycling of materials can considered to be a first order ecological priority in order to limit the quantities of radioactive wastes for final disposal and to reduce the technical and economic problems involved with the management of radioactive wastes. It will help as well to make economic use of primary material and to conserve natural resources of basic material for future generations. In a demonstration programme, Belgoprocess has shown that it is economically interesting to decontaminate metal components to unconditional release levels using dry abrasive blasting techniques, the unit cost for decontamination being only 30% of the global cost for radioactive waste treatment, conditioning, storage and disposal. As a result, an industrial dry abrasive blasting unit was installed in the Belgoprocess central decontamination infrastructure. At the end of May 2001, after 6 years of operation, 523 Mg of contaminated metal has been treated. 182 Mg of this material was unconditionally released, having been monitored twice by the in-house health physics department. About 303 Mg of the metal, presenting surfaces that could not be measured due to their shape, were melted for unconditional release in a controlled melting facility. The suitability of the abrasive blasting system was verified, and it was proved that there was no intrusion of contamination into the material surface. The paper gives an overview of the experience relating to the decontamination of metal material by abrasive blasting at the decommissioning of the Eurochemic reprocessing plant in Dessel, Belgium.

Fatigue behavior of nanoscale Mo/W multilayers on flexible substrates

MRS Advances ◽  
2019 ◽  
Vol 4 (43) ◽  
pp. 2309-2317
Author(s):  
Fang Wang ◽  
Xue-Mei Luo ◽  
Dong Wang ◽  
Peter Schaaf ◽  
Guang-Ping Zhang
Keyword(s):  
Fatigue Resistance ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Properties ◽  
Individual Layer ◽  
Out Of Plane ◽  
Inclination Angles ◽  
Plane Direction ◽  
Columnar Grain ◽  
20 Nm

ABSTRACTFatigue properties of Mo/W multilayers with individual layer thickness (λ) of 5, 20, 50 and 100 nm on flexible polyimide substrates were investigated. The experimental results show that the fatigue resistance increases with decreasing λ from 100 nm to 20 nm, and reaches the maximum at λ=20 nm, and then decreases when further decreasing λ. Fatigue cracks of Mo/W multilayers with different λ were found to propagate along columnar grain boundary in the out-of-plane direction and along the boundary of cluster structures. The enhanced fatigue resistance is attributed to the larger cluster inclination angles and the more tortuous in-plane cracking paths.

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