SEM Study of High-Chromium Martensitic Steel LCF Fracture

2011 ◽  
Vol 465 ◽  
pp. 298-301
Author(s):  
Tamaz Eterashvili ◽  
Elguja Kutelia ◽  
T. Dzigrashvili ◽  
M. Vardosanidze
Keyword(s):  
Crack Propagation ◽  
Low Cycle Fatigue ◽  
Propagation Direction ◽  
High Chromium ◽  
X Ray ◽  
Crack Propagation Direction ◽  
Sem Study ◽  
Main Effect ◽  
Growth Crack

Low cycle fatigue of high-chromium 13Х11Н2В2МФ stainless steel has been studied after cyclic tests at room temperature with the frequency of loading, 0.45Hz and amplitude, ± 1mm. The samples were v-notched with the dimensions x2x50, where =3mm. The peculiarities of fatigue crack propagation and influence of heat treatment, sizes of grains and laths, and disposition of microcrack and microstructure elements of the steel were studied. Next, the main effect on propagation direction is caused by the shape of grains and laths. It turned apparent that main microcrack is composed of individual micro-components with the lengths correlating with the dimensions of grains and martensitic laths. During growth crack propagation direction changes from lath to lath; however, general trend remains unchanged. The results of tests indicate that speed of fatigue failure rises when the frequency and amplitude of loading increases. The work includes x-ray characterization of the steel, statistical distribution curve for angles between the main direction of macrocrack propagation and micro-components, and explanation of micro- and macrocrack propagation alteration is given.

Automatic 3-D Crack Propagation Calculations in Industrial Components: A Pure Hexahedral versus a Combined Hexahedral-Tetrahedral Approach

2007 ◽  
Vol 348-349 ◽  
pp. 45-48
Author(s):  
Guido Dhondt
Keyword(s):  
Crack Propagation ◽  
Computing Time ◽  
Propagation Direction ◽  
Hexahedral Elements ◽  
Crack Propagation Direction ◽  
Low Weight ◽  
Out Of Plane ◽  
Hexahedral Meshes ◽  
Crack Faces

In recent years, increased loading and low weight requirements have led to the need for automatic crack tracing software. At MTU a purely hexahedral code has been developed in the nineties for Mode-I applications. It has been used extensively for all kinds of components and has proven to be very flexible and reliable. Nevertheless, in transition regions between complex components curved cracks have been observed, necessitating the development of mixed-mode software. Due to the curvature of the crack faces, purely hexahedral meshes are not feasible, and therefore a mixture of hexahedral elements at the crack tip, combined with tetrahedral in the remaining structure has been selected. The intention of the present paper is to compare both methods and to point out the strength and weaknesses of each regarding accuracy, complexity, flexibility and computing time. Furthermore, difficulties arising from the out-of-plane growth of the crack such as the determination of the crack propagation direction are discussed.

Characterization of low cycle fatigue damage in 9Cr–1Mo ferritic steel using X-ray diffraction technique

1999 ◽  
Vol 76 (5) ◽  
pp. 275-281 ◽  
Author(s):  
Sanjay Rai ◽  
B.K Choudhary ◽  
T Jayakumar ◽  
K.Bhanu Sankara Rao ◽  
Baldev Raj
Keyword(s):  
Fatigue Damage ◽  
Ferritic Steel ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
X Ray Diffraction ◽  
X Ray

Experimental Study and Finite Element Simulation of Heat Build-Up in Rubber Compounds with Application to Fracture

2003 ◽  
Vol 76 (2) ◽  
pp. 386-405 ◽  
Author(s):  
Vladamir Kerchman ◽  
Cheng Shaw
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Numerical Models ◽  
Propagation Direction ◽  
Transient Temperature ◽  
Ir Thermography ◽  
Crack Propagation Direction ◽  
Measure Surface Temperature ◽  
Rubber Compounds ◽  
Heat Build Up

Abstract IR thermography was used to measure surface temperature profiles of cylindrical rubber specimens during cyclic compression. A linearized constitutive approach and finite element analysis were used to evaluate heat generation and associated transient temperature fields. Modeled temperatures compared well with the IR measurements. This led to extended simulation efforts on lab fracture samples. IR thermography was used to measure temperature of filled NR and filled SBR specimens during tensile fatigue cut growth tests. Temperature gradients are expected to relate to kinetics of rubber fracture and identify regions within the sample that are undergoing accelerated damage. The following cut growth issues were addressed: 1) crack propagation direction in a non-uniform stress field; 2) crack propagation direction as a function of the angle of initial cuts; 3) initiation of crack branching; and 4) catastrophic failure. The nonlinear coupled mechanical and thermal FEA was used to evaluate the energy dissipation in the non-homogeneous cyclic deformation of cracked samples. Modeled and measured surface temperatures are in good agreement. Accounting for heat build-up ahead of an advancing crack can improve numerical models that quantify fatigue cut growth behavior in rubber compounds.

SEM Study of Fatigue Crack Propagation in Chromium Martensitic Steel after LCF

2017 ◽  
Vol 754 ◽  
pp. 15-18 ◽  
Author(s):  
Tamaz Eterashvili ◽  
G. Abuladze ◽  
L. Kotiashvili ◽  
T. Dzigrashvili ◽  
M. Vardosanidze
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Low Cycle Fatigue ◽  
Experimental Studies ◽  
Complex Problem ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Sem Study ◽  
Deformation Tests ◽  
Microstructure Of The Material

Crack propagation after low-cycle fatigue (LCF) deformation has been studied in the chromium martensitic structural steel. Although the study of a fundamental mechanism of fatigue crack growth has received much attention over the last decade, it still remains a sufficiently complex problem and needs full understanding. Moreover, the recent studies show that the cracks propagate discontinuously even on the millisecond timescale, and their growth rate significantly depends on a microstructure of the material. In the present work the boundaries of the former austenitic grains were revealed on the polished surfaces of the thermally treated samples, which subsequently were undergone low-cycle fatigue tests. The experimental studies show that fatigue macrocracks mainly grow along the boundaries of the former austenitic grains, and changetheir propagation direction when crossing the grain boundary, however, remain within 45 ̊ interval with regard the cycling axis. In particular cases, when the boundaries of a martensite packets and those of the former austenite grains lay along the length of a packet, the macrocrack is better formed and with regular borders. After a macrocrack reaches a definite length ~30-50μ, a microcrack is nucleated ahead of the macrocrack tip, and is oriented along the substructure element of the steel. Further deformation tests provide an increase in the length of the main crack via aggregation of microcracks initiated ahead of it during the LCF. In the cases when the macrocrack is deviated, slip bands are formed in martensitic structures along the boundaries of martensite packets (laths). A correlation is revealed between the microcrack components and the substructure elements of the steel as well. The same results were obtained by fractography of the tested and fractured samples. However, in the latter case correlation was established between the cleavage facets and the dimensions of packets.

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