The Process of Spalling in Railroad Wheels

2011 ◽  
Author(s):  
Steven L. Dedmon
Keyword(s):  
Finite Element ◽  
Laboratory Tests ◽  
Rapid Heating ◽  
Fatigue Cracks ◽  
Material Strength ◽  
Finite Element Analyses ◽  
Rolling Contacts ◽  
Railroad Wheels ◽  
Applied Stresses ◽  
Lower Material

Although the term “Spalling” means different things to different disciplines and product types, for railroad wheels the term is used for the process by which tread cracks form as a result of a sliding event. The process includes rapid heating and austenitizing of the tread surface during a slide followed by rapid cooling and transformation to untempered martensite. Preexisting cracks in the area of a slide can grow from shallow and harmless cracks into cracks of greater significance due to high thermal and transformation stresses. Case crushing of the tread caused by high loads can also develop into spalls. Lastly, rolling contacts can cause fatigue cracks to form at the edges of a martensite patch in the heat affected zone. A complex combination of lower material strength and higher residual and applied stresses and the limiting hardenability of carbon steel produce conditions ideal for the formation of fatigue cracks. This investigation uses finite element analyses and laboratory tests to characterize the process of spalling.

scholarly journals A Plastic Fracture Mechanics Analysis of Small Case B Fatigue Cracks Under Multiaxial Loading Conditions

1997 ◽  
Author(s):  
Y. Wang ◽  
J. Pan
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Finite Element Analyses ◽  
Growth Criterion ◽  
General Yielding ◽  
Deformation Patterns ◽  
Generalized Plane Strain

The near-tip fields of small Case B cracks in power-law hardening materials are investigated under generalized plane-strain and general yielding conditions by finite element analyses. The results for two different crack orientations are examined and compared. The results indicate that the plastic deformation patterns near the tips of the cracks of two different orientations are remarkably similar in terms of the global coordinates. The results of the J integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trends of constant ΔJ contours on the Γ-plane for two cracks of different orientations are virtually the same. Further, the trends are compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate.

Prediction of Fatigue Crack Initiation and Growth During Thermal Cycling

2015 ◽  
Author(s):  
Guiyi Wu ◽  
David Smith ◽  
David Tanner
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Crack Initiation ◽  
Thermal Cycling ◽  
Dwell Time ◽  
Thermal Loading ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Stress And Strain ◽  
Finite Element Analyses

Conventional approaches to assess fatigue under combined thermal and mechanical loading often utilize a fatigue design curve. In this paper models based on the physics and mechanics for the initiation and growth of fatigue cracks in stainless steel are first explained. The models are based on experimental evidence gathered for the initiation and growth of small cracks created during strain controlled laboratory tests. This evidence is then linked with data for the growth of large fatigue cracks in stainless steel. In the paper these models are coupled with finite element analyses to explore the fatigue initiation and growth of cracks in stainless steel pipes subjected to thermal cycling. It is assumed that the material behaviour is elastic-perfectly plastic, rate independent and fatigue occurs in air. The stress and strain fields for pipes subjected to a range of thermal loading conditions are explored. The fields are shown to be sensitive to parameters such as the Biot and Fourier numbers that include pipe dimensions, physical properties, dwell time and thermal conditions. Of particular interest is the temperature range and dwell time during thermal loading. Finite element analyses are then used to determine the stress and strain ranges created by thermal loading and these ranges are used in the crack initiation and growth models to estimate fatigue life.

Modelling of Offshore Tubular Members in Non-Linear Analyses

2005 ◽  
Author(s):  
Ken Skinner ◽  
David W. Styles ◽  
Sirous F. Yasseri
Keyword(s):  
Finite Element ◽  
Shell Model ◽  
Slenderness Ratio ◽  
Full Range ◽  
Material Strength ◽  
Finite Element Analyses ◽  
Shell Elements ◽  
Beam Elements ◽  
Linear Finite Element ◽  
Non Linear

This paper presents results of a study into calibrating beam elements properties for use in non-linear finite element analyses, such that the elements simulate the behaviour of real members. Following the API approach, it is recommended that the material strength is de-rated to achieve a well-behaved element. A large number of typical “imperfect” offshore tubular members were modelled using shell elements and analysed to determine the full range of their load-displacement behaviour. The complete practical range of combination of the slenderness and D/t (diameter to thickness) ratios were considered. Then the beam elements’ material was de-rated to achieve the same results as obtained from the shell model. The result of the study is a two-way table which gives the required de-rating as a function of the slenderness ratio and the D/t ratio.

A Plastic Fracture Mechanics Analysis of Small Case B Fatigue Cracks Under Multiaxial Loading Conditions

1998 ◽  
Vol 120 (4) ◽  
pp. 796-800 ◽  
Author(s):  
Y. Wang ◽  
J. Pan
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Finite Element Analyses ◽  
Growth Criterion ◽  
General Yielding ◽  
Deformation Patterns ◽  
Generalized Plane Strain

The near-tip fields of small Case B cracks in power law, hardening materials are investigated under generalized plane-strain and general yielding conditions by finite element analyses. The results for two different crack orientations are examined and compared. The results indicate that the plastic deformation patterns near the tips of the cracks of two different orientations are remarkably similar in terms of the global coordinates. The results of the J-integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trends of constant ΔJ-contours on the Γ-plane for two cracks of different orientations are virtually the same. Further, the trends are compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate.

Evolving the Banded Radial Tire

1987 ◽  
Vol 15 (1) ◽  
pp. 30-41 ◽  
Author(s):  
E. G. Markow
Keyword(s):  
Finite Element ◽  
Wear Rate ◽  
Finite Element Modeling ◽  
Laboratory Tests ◽  
Rolling Resistance ◽  
Two Dimensional ◽  
Theoretical Discussion ◽  
Radial Tire ◽  
Puncture Resistance ◽  
Element Modeling

Abstract Development of the banded radial tire is discussed. A major contribution of this tire design is a reliable run-flat capability over distances exceeding 160 km (100 mi). Experimental tire designs and materials are considered; a brief theoretical discussion of the mechanics of operation is given based on initial two-dimensional studies and later on more complete finite element modeling. Results of laboratory tests for cornering, rolling resistance, and braking are presented. Low rolling resistance, good cornering and braking properties, and low tread wear rate along with good puncture resistance are among the advantages of the banded radial tire designs.

Design of Pipeline Composite Repairs: From Lab Scale Tests to FEA and Full Scale Testing

2014 ◽  
Author(s):  
Remy Her ◽  
Jacques Renard ◽  
Vincent Gaffard ◽  
Yves Favry ◽  
Paul Wiet
Keyword(s):  
Finite Element ◽  
Full Scale ◽  
Combined Loading ◽  
Material Strength ◽  
Repair System ◽  
Loading Conditions ◽  
Original Design ◽  
Composite Repair ◽  
Repair Systems ◽  
Composite Properties

Composite repair systems are used for many years to restore locally the pipe strength where it has been affected by damage such as wall thickness reduction due to corrosion, dent, lamination or cracks. Composite repair systems are commonly qualified, designed and installed according to ASME PCC2 code or ISO 24817 standard requirements. In both of these codes, the Maximum Allowable Working Pressure (MAWP) of the damaged section must be determined to design the composite repair. To do so, codes such as ASME B31G for example for corrosion, are used. The composite repair systems is designed to “bridge the gap” between the MAWP of the damaged pipe and the original design pressure. The main weakness of available approaches is their applicability to combined loading conditions and various types of defects. The objective of this work is to set-up a “universal” methodology to design the composite repair by finite element calculations with directly taking into consideration the loading conditions and the influence of the defect on pipe strength (whatever its geometry and type). First a program of mechanical tests is defined to allow determining all the composite properties necessary to run the finite elements calculations. It consists in compression and tensile tests in various directions to account for the composite anisotropy and of Arcan tests to determine steel to composite interface behaviors in tension and shear. In parallel, a full scale burst test is performed on a repaired pipe section where a local wall thinning is previously machined. For this test, the composite repair was designed according to ISO 24817. Then, a finite element model integrating damaged pipe and composite repair system is built. It allowed simulating the test, comparing the results with experiments and validating damage models implemented to capture the various possible types of failures. In addition, sensitivity analysis considering composite properties variations evidenced by experiments are run. The composite behavior considered in this study is not time dependent. No degradation of the composite material strength due to ageing is taking into account. The roadmap for the next steps of this work is to clearly identify the ageing mechanisms, to perform tests in relevant conditions and to introduce ageing effects in the design process (and in particular in the composite constitutive laws).

Design of flexure revolute joint based on compliance and stiffness ellipsoids

2021 ◽  
pp. 095441002110169
Author(s):  
Jing Zhang ◽  
Hong-wei Guo ◽  
Juan Wu ◽  
Zi-ming Kou ◽  
Anders Eriksson
Keyword(s):  
Finite Element ◽  
Single Point ◽  
Synthesis Method ◽  
Nonlinear Finite Element ◽  
Finite Element Analyses ◽  
Rotational Stiffness ◽  
Rotational Angle ◽  
Parameterized Model ◽  
Flexure Joints ◽  
Translational Stiffness

In view of the problems of low accuracy, small rotational angle, and large impact caused by flexure joints during the deployment process, an integrated flexure revolute (FR) joint for folding mechanisms was designed. The design was based on the method of compliance and stiffness ellipsoids, using a compliant dyad building block as its flexible unit. Using the single-point synthesis method, the parameterized model of the flexible unit was established to achieve a reasonable allocation of flexibility in different directions. Based on the single-parameter error analysis, two error models were established to evaluate the designed flexure joint. The rotational stiffness, the translational stiffness, and the maximum rotational angle of the joints were analyzed by nonlinear finite element analyses. The rotational angle of one joint can reach 25.5° in one direction. The rotational angle of the series FR joint can achieve 50° in one direction. Experiments on single and series flexure joints were carried out to verify the correctness of the design and analysis of the flexure joint.

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