Correlation between Hardness and Fatigue Properties

2015 ◽  
Vol 662 ◽  
pp. 197-200 ◽  
Author(s):  
Pavol Zubko ◽  
Ladislav Pešek
Keyword(s):  
Cyclic Loading ◽  
Fatigue Behavior ◽  
Hardness Measurement ◽  
Fatigue Properties ◽  
Tensile Curve ◽  
Static Tensile ◽  
Static And Cyclic Loading ◽  
Hardness Values ◽  
Good Agreement

The contribution deals with estimation of tensile properties and fatigue behavior based on hardness measurement. First of all the database of tensile and fatigue properties vs. hardness data was created for a group of steels, from literature survey and performed experiments. Tensile strength, yield strength, ductility and parameters of Ludwig-Hollomon equation in static and cyclic loading were extracted and fitted in relation to the hardness HB. The experimental materials were API 5 L grade steels – X60 and X70 after different deformation exposition. Measured tensile curve (SC) and cyclic deformation curve (CDC) were compared with predicted curves. Hardness was measured in-situ during cyclic loading. The maximum possible hardness values were experimentally determined. The results give a good agreement between estimated and measured data of both static tensile test and fatigue properties.

scholarly journals Effects of thermomechanical history and environment on the fatigue behavior of (β)-Ti-Nb implant alloys

2018 ◽  
Vol 165 ◽  
pp. 06001 ◽  
Author(s):  
André Reck ◽  
Stefan Pilz ◽  
Ulrich Thormann ◽  
Volker Alt ◽  
Annett Gebert ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Cyclic Loading ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Grain Structure ◽  
Fatigue Properties ◽  
Β Phase ◽  
Α Phase ◽  
Nb Content ◽  
Implant Alloys

This study examined the fatigue properties of a newly developed cast and thermomechanical processed (β)-Ti-40Nb alloy for a possible application as biomedical alloy due to exceptional low Young’s modulus (64-73 GPa), high corrosion resistance and ductility (20-26%). Focusing on the influence of two microstructural states with fully recrystallized β-grain structure as well as an aged condition with nanometer-sized ω-precipitates, tension-compression fatigue tests (R=-1) were carried out under lab-air and showed significant differences depending on the β-phase stability under cyclic loading. Present ω- precipitates stabilized the β-phase against martensitic α’’ phase transformations leading to an increased fatigue limit of 288 MPa compared to the recrystallized state (225 MPa), where mechanical polishing and subsequent cyclic loading led to formation of α’’-phase due to the metastability of the β-phase. Additional studied commercially available (β)-Ti-45Nb alloy revealed slightly higher fatigue strength (300 MPa) and suggest a change in the dominating cyclic deformation mechanisms according to the sensitive dependence on the Nb-content. Further tests in simulated body fluid (SBF) at 37°C showed no decrease in fatigue strength due to the effect of corrosion and prove the excellent corrosion fatigue resistance of this alloy type under given test conditions.

In situ observation of fatigue behavior of single crystal copper micron-scale specimen under tension-compression cyclic loading

2018 ◽  
Vol 2018 (0) ◽  
pp. OS1403
Author(s):  
Takashi SUMIGAWA ◽  
Kim BYUNGWOON ◽  
Yuki MIZUNO ◽  
Takuma MORIMURA ◽  
Takayuki KITAMURA
Keyword(s):  
Cyclic Loading ◽  
Single Crystal ◽  
Fatigue Behavior ◽  
Single Crystal Copper

Effect of pre-strain on the fatigue behavior of SAPH440 steel

2019 ◽  
Vol 9 (9) ◽  
pp. 1001-1008 ◽  
Author(s):  
Li-Hui Zhao ◽  
Hong-Chang Cai ◽  
Shuo Weng ◽  
Song-Lin Zheng
Keyword(s):  
Fatigue Strength ◽  
Dislocation Density ◽  
Work Hardening ◽  
Fatigue Behavior ◽  
Static Strength ◽  
Fatigue Properties ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Transmission Electron ◽  
Static Tensile

The present research envisages the effects of different uniaxial tensile pre-strain levels on the fatigue properties of the SAPH440 steel. The S-N curves of different pre-strain levels (0%, 6%, 12%, 18%) were drawn using different load levels, with a stress ratio R = –1. The test results show that the fatigue strength of the SAPH440 steel increased with an increasement in the uniaxial tensile pre-strain levels. The static tensile test was carried out on different uniaxial tensile and different pre-strain levels specimens. The results show that with an increase in the uniaxial tensile pre-strain levels, the degree of work hardening of the SAPH440 steel and the static strength increased. Additionally, the hardening index and the elongation at break reduced, while the tensile strength and yield strength increased. TEM (Transmission Electron Microscopy) observation of the test samples with different pre-strain levels showed that the dislocation density of different pre-strain levels specimens increased with an increasement in the pre-strain levels. This resulted in an increasement in the fatigue strength of the SAPH440 steel, the degree of work hardening, and the static strength. However, compared with fatigue strength, the increase of dislocation density has a more significant effect on static strength.

Prediction of Tensile Properties Based on Hardness Measurement

2014 ◽  
Vol 606 ◽  
pp. 35-38 ◽  
Author(s):  
Pavol Zubko ◽  
Ladislav Pešek
Keyword(s):  
Tensile Strength ◽  
Yield Strength ◽  
Tensile Properties ◽  
Tensile Testing ◽  
Brinell Hardness ◽  
Hardness Measurement ◽  
Stress Strain ◽  
Hardness Values ◽  
Hollomon Equation ◽  
Good Agreement

The contribution deals with prediction of tensile properties based on measurement of microhardness. First of all, the database of stress strain, s-e vs. hardness data was created. Tensile strength, yield strength, ductility and parameters of Ludwig-Hollomon equation σ = σ0+kεn; k, n were correlated with hardness. Various hardness values found in literature were recalculated to Brinell hardness. In tensile testing measured s-e curves were compared with that obtained from the correlation. The investigated materials were API 5 L grade steels X70 after different deformation exposition. The results give good agreement between compared data. The most difference between estimated and measured curve is in area of yield strength, because of Lüders deformation on investigated steel.

Fatigue properties by “self-heating” method: Application to orthodontic Ni-Ti wires after hydrogen charging

2018 ◽  
Vol 29 (16) ◽  
pp. 3242-3253 ◽  
Author(s):  
Maha Rokbani ◽  
Luc Saint-Sulpice ◽  
Shabnam Arbab Chirani ◽  
Tarak Bouraoui
Keyword(s):  
Cyclic Loading ◽  
Fatigue Behavior ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Orthodontic Wires ◽  
Heating Method ◽  
Hydrogen Charging ◽  
Self Heating ◽  
Number Of Cycles

Ni-Ti superelastic alloys have been successfully used in orthodontic clinics thanks to their good biomechanical and biochemical behavior. However, during treatment, some orthodontic wires may break in the oral cavity. The susceptibility of these alloys to cyclic loadings and to hydrogen embrittlement is supposed to be main causes of these unexpected failures. This study presents a contribution to studying the effect of hydrogen, obtained after cathodically charging in 0.9% NaCl solution, on the fatigue behavior of Ni-Ti commercial orthodontic wires subjected to high-cycle fatigue. Fatigue tests were analyzed using self-heating method based on observing thermal effects under mechanical cyclic loading. The results obtained with self-heating approach imply that the increase in hydrogen charging time is connected with an increase in the mean stabilized temperature and a decrease in the fatigue life. Self-heating method allows a rapid prediction of the endurance limit with a good reproducibility of fatigue tests at high number of cycles. Furthermore, cyclic stress–induced transformations and conventional fatigue tests under strain control are considered in this work to investigate the effect of hydrogen on cyclic loading type and to acquire for a better understanding of the interaction between hydrogen and thermo-mechanical mechanisms in Ni-Ti alloys.

Effects of stabilization patterns on the static and fatigue behavior of glass fiber non-crimp fabric composites

2019 ◽  
Vol 53 (25) ◽  
pp. 3589-3598
Author(s):  
Sana Ullah Nasir ◽  
Asim Shahzad
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Glass Fiber ◽  
Volume Fraction ◽  
Fatigue Behavior ◽  
Experimental Studies ◽  
Tensile Modulus ◽  
Fatigue Properties ◽  
Fabric Composites ◽  
Static Tensile

Experimental studies have been conducted to evaluate static tensile and tension–tension fatigue response of unidirectional glass fiber non-crimp fabric composites subject to seven different stabilization patterns (two multiaxial and five uniaxial stabilizing yarns). The effect of stabilization patterns on non-crimp fabric is crucial as they produce different mesoscale bundle shapes and bundle volume fractions which may affect the static and fatigue properties of non-crimp fabric composites. The studies show that tensile modulus and fatigue life decline with increasing amount of uniaxial stabilizations. Different stabilizations with different bundle shapes influence the final composite properties through various factors than just the volume fraction. The multiaxial stabilizations with higher static tensile strength have shorter fatigue life as compared to uniaxial stabilizations with lower tensile strength. As the areal weight of stabilizing yarns increases, fatigue life decreases at all stress levels which show the deleterious effects of stabilizations on the fatigue behavior of composites. Areal weight and orientation of stabilizing yarns should be optimally selected for the anticipated performance of the non-crimp fabric composites.

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