The Influence of Mean Stress on Fatigue Properties of ADI

2007 ◽  
Vol 567-568 ◽  
pp. 341-344
Author(s):  
Stanislav Vĕchet ◽  
Jan Kohout ◽  
Klára Hanzlíková ◽  
Vojtěch Hruby
Keyword(s):  
Fatigue Limit ◽  
Nodular Cast Iron ◽  
Isothermal Transformation ◽  
Fatigue Properties ◽  
Quantitative Phase Analysis ◽  
Mean Stress ◽  
Convex Shape ◽  
Limit Values ◽  
Static Tests ◽  
General Power

The paper presents the results of research focused on assessment of the influence of loading cycle asymmetry on fatigue limit values. For tests two heats of unalloyed nodular cast iron were used. Test bars made of keel blocks were heat treated in salt bathes (austenitization at 900 °C during 1 hour, isothermal transformation at 380 and 400 °C) and loaded at symmetrical, repeating and pulsating loading cycles at room temperature. Evaluation of fatigue properties was based on the determination of S-N curves in high-cycle region including the fatigue limit assessment for 107 cycles to fracture. Fatigue and static tests were completed by metallographic and quantitative phase analysis. Most important result obtained from the presented study is that the dependence of stress amplitude on mean stress cannot be approached by the linear relation but by general power law with exponent lower than 1 (i.e. the Haigh diagram has convex shape).

Fatigue properties of a glass-fibre-reinforced polyester material used in wind turbine blades

1998 ◽  
Vol 33 (3) ◽  
pp. 183-193
Author(s):  
J Vázquez ◽  
A Silvera ◽  
F Arias ◽  
E Soria
Keyword(s):  
Wind Turbine ◽  
Fatigue Limit ◽  
Glass Fibre ◽  
Moisture Absorption ◽  
Turbine Blades ◽  
Fatigue Properties ◽  
Dynamic Tests ◽  
Wind Turbine Blades ◽  
Static Tests ◽  
Glass Fibre Reinforced

Glass-fibre-reinforced polyester (GFRP) is a composite commonly used in the manufacture of wind turbine blades. In the present work, one such material has been subject to static and dynamic tests in order to obtain data that can be applied to the design of wind turbine blades and other machine elements. The results of the static tests established a basis for the determination of a set of tension-tension (constant amplitude and sinusoidal load) dynamic tests with the aim of establishing a mathematical model in order to predict life as a function of the load state and calculate the fatigue limit. The multiplicative model (y = axb) for y = log of life and x = transformed stress (a and b are characteristic parameters of the material obtained from data) matches the data quite well. The conclusion is that the GFRP studied has no fatigue limit. The possible decrease of fatigue strength of the material with solar radiation and moisture absorption was also investigated, with a negative result.

scholarly journals Effect of surface compressive residual stress introduced by surface treatment on fatigue properties of metallic material

2018 ◽  
Vol 165 ◽  
pp. 18006
Author(s):  
Jinta Arakawa ◽  
Tatsuya Hanaki ◽  
Yoshiichirou Hayashi ◽  
Hiroyuki Akebono ◽  
Atsushi Sugeta
Keyword(s):  
Residual Stress ◽  
Surface Treatment ◽  
Fatigue Limit ◽  
Compressive Residual Stress ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Mean Stress ◽  
Metallic Material ◽  
Effect Of Surface

This study considers shakedown in evaluating the fatigue limit of metals with compressive residual stress at the surface. We begin by applying tension-compression fatigue tests to ASTM CA6NM under conditions of controlled load and displacement to obtain fatigue limit diagram in compressive mean stress. The results imply that shakedown occurs under the condition of controlled displacement, therefore, shakedown should be considered when evaluating the fatigue limit of metals with compressive residual stress at the surface.

Influence of Isothermal Transformation Dwell on Tensile and Fatigue Properties of Austempered Ductile Iron

2005 ◽  
Vol 482 ◽  
pp. 371-374 ◽  
Author(s):  
Stanislav Vĕchet ◽  
Jan Kohout ◽  
Klára Hanzlíková
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Fatigue Limit ◽  
Ductile Iron ◽  
Retained Austenite ◽  
Isothermal Transformation ◽  
Austempered Ductile Iron ◽  
Fatigue Properties ◽  
Stress Increase ◽  
Yield Stress Increase

Two ADI heats transformed at temperatures of 400 and 380 °C during temporal range from 2 minutes to 9 hours were studied in details, with emphasis on structure composition and mechanical properties (tensile and fatigue properties were determined). In the case of the shortest dwells the level of mechanical properties is influenced by martensite, which occurs in the structure as a result of subsequent cooling. UTS and yield stress increase slightly with the dwell of isothermal transformation while the values of elongation to fracture as well as of fatigue limit are very closely dependent on the amount of the retained austenite in the microstructure.

Effect of Pre-Strain and Roller Working on Torsional Fatigue Properties of a Structural Steel

2011 ◽  
Vol 295-297 ◽  
pp. 2227-2230
Author(s):  
Cong Ling Zhou
Keyword(s):  
Residual Stress ◽  
Fatigue Limit ◽  
Work Hardening ◽  
Compressive Residual Stress ◽  
Strain Ratio ◽  
Fatigue Tests ◽  
The Other ◽  
Fatigue Properties ◽  
Torsional Fatigue ◽  
Stress Work

In this study, fatigue tests have been performed using two kinds of specimens made of 25 steel. One is pre-strained specimen with pre-strain ratio changing from 2% to 8% by tension, the other is roller worked with deformation of 0.5 mm and 1.0 mm in diameter direction. In the case of pre-strained specimen, the fatigue limit increases according to increase of tensile pre-strain, the fatigue limit of 8% pre-strained specimen is 25% higher than that of non-pre-strained one; in the case of roller worked specimen, the fatigue limit of R05 and R10 is 126% and 143% to that of non-roller worked specimen, respectively. These remarkable improvements of fatigue limit would be caused by the existence of compressive residual stress, work-hardening and the elongated microscopic structures.

A new method for prediction of nodular cast iron fatigue limit

2010 ◽  
Vol 32 (7) ◽  
pp. 988-995 ◽  
Author(s):  
N. Costa ◽  
N. Machado ◽  
F.S. Silva
Keyword(s):  
Cast Iron ◽  
Fatigue Limit ◽  
Nodular Cast Iron ◽  
New Method

The Influence of Mean Stress on Fatigue Properties of ADI

2007 ◽  
pp. 341-344
Author(s):  
Stanislav Vĕchet ◽  
Jan Kohout ◽  
Klára Hanzlíková ◽  
Vojtěch Hrubý
Keyword(s):  
Fatigue Properties ◽  
Mean Stress

The Processing and Fatigue Characterization of TiNi and Ti-6Al-4V Porous Materials

2011 ◽  
Vol 493-494 ◽  
pp. 930-935 ◽  
Author(s):  
Emin Erkan Aşik ◽  
Gül Ipek Nakaş ◽  
Şakir Bor
Keyword(s):  
Titanium Alloys ◽  
Endurance Limit ◽  
Fatigue Behavior ◽  
Porous Titanium ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Compression Tests ◽  
Limit Values ◽  
Porous Ti ◽  
Structural Applications

Porous titanium alloys have been extensively studied in biomedical applications due to their elastic moduli similar to that of bone compared to other implant materials. Accordingly, TiNi and Ti-6Al-4V foams have been widely characterized in terms of their various mechanical properties; however, their fatigue properties have not been well studied, even though, it has a vital importance in structural applications such as medical implants. In this study, porous titanium alloys were processed via sintering at 1200 °C for 2 hours employing Mg space holder technique. TiNi and Ti-6Al-4V alloys with a porosity of 49 and 51 vol.%, respectively, were mechanically characterized by monotonic and cyclic compression tests. The compressive strength was determined to be 148 MPa for TiNi foams whereas 172 MPa for Ti-6Al-4V foams with homogenously distributed pores having diameters in the range of 250-600 µm. Endurance limit values were determined relative to the yield strength of each porous alloy in order to enable the comparison of fatigue behavior. The fatigue tests applied with a frequency of 5 Hz and a constant stress ratio (σmin/σmax) of 0.1 have revealed that porous TiNi alloys have an endurance limit of approximately 0.6 σy whereas porous Ti-6Al-4V alloys have an endurance limit of approximately 0.75 σy. The differences and similarities in the microstructure and their effect on mechanical behavior of the two alloys were also studied by employing scanning electron microscope (SEM).

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