Fatigue Characteristics Of Steel Research Articles

Effect of Coatings on the Fatigue Characteristics of Steels Under Contact Load

A new type of technological process is proposed for increasing the life of structural elements under rolling friction. Results of comparative experimental studies on increasing the life of steels under rolling friction, using hydrogen-free integral techniques for the application of gradient coatings with optimal properties, residual stresses and substrate hardness and using ion nitriding and heat treatment.

The Influence of the Ferrite and Pearlite Grain Size on the S-N Fatigue Characteristics of Steel

In this work an investigation of internal structure influence on mechanical and fatigue properties of ferritic-pearlitic steels is shown. Ferrite grain size and phase volume fraction of three grades of structural steel with similar chemical composition, but different mechanical properties, were examined. Afterwards, samples of the materials were subjected to cyclic bending tests. The results and conclusions are presented in this paper

Scatter in the fatigue characteristics of steels and its analysis with allowance for cyclic inelastic strains

The regularities of the scatter in the characteristics of fatigue and inelasticity of steels 45 and 1Kh13 have been studied under steady-state, step, and block loading. It is shown that the use of the inelastic strain per cycle as a measure of the fatigue damage accumulation rate makes it possible to take into account the scatter in the number of cycles to fracture and in the fatigue limits and to substantiate the cumulative fatigue damage rule.

Fatigue durability of steels of railroad wheels

On the basis of the characteristics of strength, hardness, and fatigue failure resistance, we substantiate the possibility of replacement of the railroad wheels of current production by the developed high-strength wheels. We have revealed an ambiguous influence of the structure and strength level on the fatigue behavior of wheel steels depending on the presence or absence of crack-like defects in their structure. For eliminating this ambiguity, it is proposed to evaluate the endurance of steels with regard for the structural-mechanical parameter (d*). Using the Kitagawa-Takahashi diagram, we predict the safe size of a defect (the diameter of a destroyed inclusion) 2a 0 = d* = 126–186 µm under cyclic loading. Furthermore, the influence of the sizes of technological defects (of diameter up to 3 mm) on the fatigue characteristics of steels of railroad wheels has been evaluated. We have established that a decrease in the permissible size of technological defects from 3.0 to 1.5 mm will increase two to three times the fatigue durability of wheels.

Effect of plasma spray coating on the fatigue characteristics of steel 45

1. The life of coatings by the criterion of fatigue limit is determined by the technology, the materials, parameters and structure of sprayed-on coatings, by adhesive bonds. 2. Important parameters affecting the fatigue characteristics are the sequence and kind of sprayed-on powders, the existence and the thickness of the sublayer, the total thick ness of the sprayed-on layer, preliminary heating of the substrate (increases adhesion), residual stresses arising during treatment (with increasing thickness of the coating the residual tensile stresses increase). 3. The use of powder PN85Yu15 as sublayer and of power PR-N65Kh25S3R3 as upper layer, with the total thickness of the coating equal to 0.15 mm, increases the fatigue limit of spra coated specimens by 30% in comparison with the same specimens but with the material in the initial state.

Properties of 55KhGR steel after high-temperature thermomechanical treatment and repeated quenching

1. Straight HTTMT makes it possible to improve the strength and fatigue characteristics of steel by almost 10%. The maximum toughening effect is attained with about 25% strain. 2. Repeated quenching of the steel and hardening HTTMT with the use of rapid heating after intermediate high-temperature tempering partially reestablishes the strength and improves the plastic properties of the steel obtained by straight HTTMT, and there is little decrease of the fatigue limit. 3. Straight HTTMT without low-temperature tempering does not provide complete “reversibility” of the properties with repeated quenching and low-temperature tempering after HTTMT.