Influence of corrosion on fatigue behaviour of old crane runway steel

2019 ◽  
Vol 54 (7-8) ◽  
pp. 416-423
Author(s):  
Stanislav Seitl ◽  
Petr Miarka ◽  
Pavel Pokorný ◽  
Jan Klusák
Keyword(s):  
Crack Initiation ◽  
Cross Sections ◽  
Fatigue Cracks ◽  
Element Model ◽  
Fatigue Behaviour ◽  
Fatigue Properties ◽  
Experimental Measurements ◽  
Stress Concentrations ◽  
The Finite Element Model ◽  
Surface Crack Initiation

Experimental measurements of fatigue properties of old steel used for a crane runway were performed to capture the influence of corrosion on fatigue life of the material. Basquin’s law was used to quantify the fatigue properties of old steel with different cross sections and with different surface of specimens (polished and corroded). The finite element model was prepared to assess and quantify the various stress distribution in specimens with circular and rectangular cross sections. Fracture surfaces of the three kinds of specimens (circular polished, rectangular polished and rectangular corroded) were studied and they showed the surface crack initiation. The following fatigue cracks developed from the surface and expanded into specimen with radiation pattern. Observed crack initiation areas confirmed the ones expected according to stress concentrations.

scholarly journals Study of Asphalt-Concrete Pavement Fatigue Modeling

2021 ◽  
Vol 16 (1) ◽  
pp. 24-36
Author(s):  
Peteris Skels ◽  
Viktors Haritonovs ◽  
Pavel Akishin ◽  
Andris Freimanis
Keyword(s):  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
Element Model ◽  
Fatigue Behaviour ◽  
Asphalt Pavements ◽  
Fatigue Properties ◽  
Surface Loading ◽  
Asphalt Concrete Pavement ◽  
Cyclic Surface

Deterioration of asphalt pavements due to fatigue cracking is one of the most common highway pavement failure types. If the fatigue cracks are allowed to develop and grow, the driving comfort and safety, i.e., serviceability of the pavement, decreases. Pavement fatigue behaviour is not a straightforward mechanism and involves many factors and effects, thus computational methods are developed in order to help understand how the pavement works. This paper explores the accuracy and applicability of a less computational resource demanding procedure that uses transient material mechanical behaviour to model the long-term behaviour of a pavement structure. First, the mechanical and fatigue properties of asphalt were determined at the laboratory. Then a four-layer finite-element model was created using Ansys software. Two different models – with and without infinity elements – and two different fatigue simulation procedures – full and simplified – were considered. Material parameters were obtained by the laboratory tests and material properties degraded over time. Cyclic surface loading was applied to simulate the passing of a truck – 6 million fatigue cycles were simulated.

Fatigue Crack Initiation and Growth in Stainless Steel Pipe Welds

2009 ◽  
Author(s):  
D. Green ◽  
R. D. Smith ◽  
J. P. Taggart ◽  
D. Beardsmore ◽  
S. Robinson
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Thermal Loading ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Cyclic Hardening ◽  
Element Model ◽  
Fatigue Tests ◽  
Welded Pipe ◽  
Pipe Work

Thermal fatigue cracks have been found in austenitic pipe work in many pressurised water reactors, caused by thermal cycling due to the passage of water at different temperatures along the pipe inner surface. The rates of crack initiation and growth for this situation are not well understood because of the stochastic nature of the temperature fluctuations. Therefore, large allowances must be made when assessing the integrity of this pipe work to this failure mechanism. Improved assessment of crack initiation and growth could enable increased plant availability, and better safety cases. A programme of work has been completed consisting of fatigue tests on thick 304L butt-welded pipe specimens, and accompanying predictions of crack initiation and growth. In each test, uniform thermal cycles were generated using a water jet on a small area of the pipe. The magnitude of the cycles differed between the tests. Crack initiation and growth were monitored using a dye penetrant technique, applied to the pipe inner and outer surfaces, together with destructive examination. Crack initiation predictions were made using fatigue data derived from mechanical fatigue tests on the same material as in the pipe specimens. Good predictions were made using a strain-life endurance curve at a temperature corresponding to the average temperature of the metal surface during the thermal cycle. Crack growth predictions were based on an inelastic finite-element model accounting for cyclic hardening, and an enhanced R5 procedure (1) with crack closure taken into account. A linear elastic fracture mechanics definition of a Paris law for crack growth was used, and plastic redistribution effects were included. Predictions were good for all of the experimental scenarios carried out. A further experimental and analytical programme is in hand using the same experimental arrangements, concerning variable amplitude thermal loading.

Scale and Surface Machining Quality Effect on Fatigue Properties for China Railway Grade B Cast Steel Wheel

2011 ◽  
Vol 480-481 ◽  
pp. 363-368
Author(s):  
Yong Xiang Zhao ◽  
Bing Yang ◽  
Y. Li
Keyword(s):  
Fatigue Cracks ◽  
Cast Steel ◽  
Fatigue Behaviour ◽  
Fatigue Properties ◽  
Surface Machining ◽  
Linear Effect ◽  
Steel Wheel ◽  
Damage Process ◽  
China Railway ◽  
Random Fatigue

Synthetic method is studied on assessing scale and surface machined effect on fatigue lives of China railway grade B cast steel wheel. Three kinds of specimens are applied for revealing the non-linear effect with scale kinetics at a least of cost. And 8 to 9 samples are applied for each kind of specimen to reveal the random fatigue behaviour. Assessing work is carried out on a phase of fatigue lives with scale kinetics at a specified strength. Results reveal that fatigue cracks were initiated from the specimen surface having a bigger site and the fatigue damage process companied with less plastic deformation than the material specimens. Random effects on fatigue lives and effect factors are constructed for measuring effects. Statistical character of the test data has been well described.

Fatigue Behaviour of Ti-6Al-4V Alloy in Vacuum and at Low Temperature

2008 ◽  
Vol 41-42 ◽  
pp. 83-90 ◽  
Author(s):  
J.H. Zuo ◽  
Z.G. Wang ◽  
En Hou Han
Keyword(s):  
Low Temperature ◽  
Fatigue Fracture ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Sample Surface ◽  
Fatigue Behaviour ◽  
Fatigue Properties ◽  
Fatigue Fracture Surface ◽  
Cracks Propagation

Investigations have been conducted on the fatigue behavior of Ti-6Al-4V alloy with the bimodal microstructure in air at room temperature, in vacuum at room temperature and in vacuum at low temperature (100K), respectively. The results show that the fatigue life of this alloy is longer in vacuum and/or at low temperature than that in air at room temperature. The combination of vacuum and low temperature can much improve the fatigue properties of this alloy because of their purifying effect on fatigue cracks propagation. SEM observation of fatigue fracture surface indicates that all the fatigue cracks initiate in the sample surface when Nf ≦106 cycles. The above three testing conditions lead to different modes of fatigue crack propagation and therefore much different morphology of fatigue fracture.

scholarly journals High-Cycle Fatigue Properties and Sub-Surface Crack Initiation in Ti-5%Al-2.5%Sn ELI Alloy

2003 ◽  
Vol 67 (8) ◽  
pp. 391-397 ◽  
Author(s):  
Yoshinori Ono ◽  
Tetsumi Yuri ◽  
Hideshi Sumiyoshi ◽  
Saburo Matsuoka ◽  
Toshio Ogata
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
High Cycle Fatigue ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Surface Crack Initiation

Study on the Fatigue Properties of the TIG Weld Joint with the Stainless Steel Conduit in Aircraft

2015 ◽  
Vol 664 ◽  
pp. 104-110
Author(s):  
Ying Liu ◽  
Dong Jie Li ◽  
Xiao Hong Li
Keyword(s):  
Stainless Steel ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Weld Joint ◽  
Fatigue Cracks ◽  
Fatigue Properties ◽  
Research Focus ◽  
Weld Toe ◽  
Crack Initiation Life

The research focus on the material of the stainless steel thin conduit in aircraft, named 1Cr18Ni9Ti , and the TIG weld joint of which was investigated to analysis the fatigue properties. The fracture mechanics was used to analysis the crack initiation life and crack propagation life, and the fatigue surface was characterized with scanning electron microscope (SEM). The experimental and analytical results show that, the origin position of fatigue crack is the surface of the conduit. The stress concentration at the weld toe, the crystal structure is not uniform and Stress concentration in the heat affected zone (HAZ) and fusion line, so the fatigue cracks are easily generated in these locations. Delta K increases to a certain value, the HAZ has become one of the most dangerous position. The crack initiation life of HAZ in the total fatigue life is far higher than the proportion of crack propagation life.

Prediction of the Ceramic Foam Structure Failure Using a Detailed Finite Element Model

2019 ◽  
Vol 827 ◽  
pp. 222-227
Author(s):  
Oldřich Ševeček ◽  
Jiří Hanák ◽  
Zdeněk Majer ◽  
Daniel Drdlík ◽  
Zdeněk Chlup ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Crack Initiation ◽  
Energy Condition ◽  
Energy Criterion ◽  
Element Model ◽  
Ceramic Foam ◽  
Fe Model ◽  
Stress Concentrations ◽  
Foam Structure ◽  
3D Volume

The contribution deals with modelling and prediction of failure of mechanically loaded open cell ceramic foam structures by using 3D volume FE models constructed from CT scans of real foam specimens. The condition for crack initiation in particular struts comes from the coupled stress-energy criterion which combines two fracture-mechanics parameters of the investigated material – tensile strength and its fracture toughness. By combining of both stress and energy condition one obtains information about the crack initiation length which is later used (together with the tensile strength) for determination of the strut failure in the complex 3D FE model of the ceramic foam structure. The crack onset is considered in the critical location at the moment when the (tensile) principal stress under the strut surface (in a depth corresponding to the crack initiation length) exceeded the tensile strength of the strut. Such approach enables us to define failure also on relatively coarse meshes of the FE models where potential stress concentrations are not described precisely and therefore it is not possible to decide about the failure just based upon the value of tensile stress on the strut surface.

Effect of Frequency on the Fatigue Behavior of IN718 Superalloy

2017 ◽  
Vol 1142 ◽  
pp. 23-30 ◽  
Author(s):  
Jin Hui Du ◽  
Xu Dong Lu ◽  
Qun Deng
Keyword(s):  
Grain Size ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Low Frequency ◽  
Initiation Site ◽  
Fatigue Properties ◽  
Crack Initiation Site

IN718 alloy possesses excellent mechanical properties at high temperatures, good process ability, therefore, it has been widely used in aero engine turbine disks, compressor disks, and power turbine shafts (i.e., rotating components). The fatigue properties of the alloy are a key factor that determines the safety and reliability of the engine. In this paper, the fatigue properties of IN718 alloy are investigated under low-and middle-frequency conditions at 600 °C and 455 °C, the initiation of fatigue cracks, and the relation between fatigue life and grain size are discussed. The results show that the carbides response as a crack initiation site at low-frequency fatigue condition (1 Hz), and string-type or heap-type carbides distribution promotes crack propagation and shortens fatigue life, the twin boundaries in large grains are act as a crack initiation site at middle-frequency fatigue condition (10 Hz). The grain size is smaller, and the low cycle fatigue properties of the alloy are better.

Influence of Aggregate Stiffness on Fracture-Mechanical Properties of Lime-Based Mortars

2013 ◽  
Vol 486 ◽  
pp. 289-294 ◽  
Author(s):  
Pavel Tesárek ◽  
Václav Nežerka ◽  
Pavel Padevět ◽  
Jakub Antoš ◽  
Tomáš Plachy
Keyword(s):  
Experimental Investigation ◽  
Finite Element ◽  
Damage Model ◽  
Element Model ◽  
Stress Concentrations ◽  
Damage Development ◽  
Element Analysis ◽  
Three Point Bending ◽  
Isotropic Damage ◽  
The Finite Element Model

Addition of relatively stiff aggregates into lime-based mortars is responsible for an increase of the effective mortar stiffness and stress concentrations around aggregates during mechanical loading. To observe the damage development during the three-point bending and splitting tests a 2D plane-stress nonlinear finite element analysis utilizing isotropic damage model was carried out and the results were validated against experimentally obtained data. The study revealed that the finite element model is able to capture the trends observed during the experimental investigation. The results of the numerical modeling and experimental investigation show the advantages of the use of relatively compliant crushed brick aggregates in ancient structures.

scholarly journals Fatigue Assessment of Selective Laser Melted Ti-6Al-4V: Influence of Speed Manufacturing and Porosity

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1022
Author(s):  
Unai Segurajauregi ◽  
Adrián Álvarez-Vázquez ◽  
Miguel Muñiz-Calvente ◽  
Íker Urresti ◽  
Haydee Naveiras
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Additive Manufacturing ◽  
Fatigue Strength ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Surface Defects ◽  
Fatigue Behaviour ◽  
Experimental Measurements ◽  
Complete Understanding

Additive Manufacturing represents a promising technology as an alternative to the conventional manufacturing process, with rapid and economic product development, as well as a significant weight reduction and a freeform design. Although the mechanical properties of additively manufactured metals, such as the Ti-6Al-4V alloy, are well-established, a complete understanding of the fatigue performance is still a pending aspiration due to its inherent stochastic complexity and the influence of several manufacturing factors. This paper presents a study of the influence of speed manufacturing and porosity in the fatigue behaviour of a Ti-6Al-4V alloy. To this aim, a numerical simulation of the expected porosity at different laser velocities is performed, together with a simulation of the residual stresses. These numerical results are compared with experimental measurements of residual stresses and a qualitative analysis of the porosities. Then, fatigue strength is experimentally obtained for two different laser speeds and fitted by a probabilistic model. As a result, the probabilistic S–N fields for different laser velocities are found to be similar, with scatter bands nearly coincident, drawing the conclusion that this effect is negligible in comparison with other concurrent ones, such as roughness or surface defects from manufacturing conditions, promoting crack initiation and premature fatigue failure.

Sign in / Sign up

Export Citation Format

Share Document