Numerical study of the mechanical deterioration of insulated rail joints

2008 ◽  
Vol 223 (3) ◽  
pp. 265-273 ◽  
Author(s):  
J Sandström ◽  
A Ekberg
Keyword(s):  
Numerical Study ◽  
Low Cycle Fatigue ◽  
Effective Strain ◽  
Axial Loading ◽  
Damage Mechanism ◽  
Cycle Fatigue ◽  
Longitudinal Loading ◽  
Calculation Results ◽  
Insulating Gap ◽  
Simulation Results

Numerical simulations are performed to study plastic deformation and fatigue impact of an insulated joint. The simulations feature a sophisticated constitutive model capable of capturing ratcheting under multi-axial loading conditions. Calculation results are presented in the form of effective strain magnitudes, plastic zone sizes, and multi-axial low cycle fatigue parameters. The simulation results indicate that the main damage mechanism at insulated joints is ratcheting and not low cycle fatigue. A parametric study quantifies effects of increased vertical and longitudinal load magnitudes, as well as the effect of an increased insulating gap. In particular, longitudinal loading is indicated as being severely deteriorating for the rail in the vicinity of the joint. Finally, the effect of rail edge bevelling is assessed and found to be small for the case studied.

A Rational Methodology for Determination of Service Life for a Delayed Coker Drum

2015 ◽  
Author(s):  
John J. Aumuller ◽  
Jie Chen ◽  
Vincent A. Carucci
Keyword(s):  
Service Life ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Mechanical Damage ◽  
Damage Mechanism ◽  
Modern Trend ◽  
Cold Spot ◽  
Chromium Alloy ◽  
Cycle Fatigue ◽  
Service Environment

Delayed unit coker drums operate in a severe service environment that precludes long term reliability due to excessive shell bulging and cracking of shell joint and shell to skirt welds. Thermal fatigue is recognized as the leading damage mechanism and past work has provided an idealized description of the thermo-mechanical mechanism via local hot and cold spot formation to quantify a lower bound life estimate for shell weld failure. The present work extends this idealized thermo-mechanical damage model by evaluating actual field data to determine a potential upper bound life estimate. This assessment also provides insight into practical techniques for equipment operators to identify design and operational opportunities to extend the service life of coke drums for their specific service environments. A modern trend of specifying higher chromium and molybdenum alloy content for drum shell material in order to improve low cycle fatigue strength is seen to be problematic; rather, the use of lower alloy materials that are generally described as fatigue tough materials are better suited for the high strain-low cycle fatigue service environment of coke drums. Materials such as SA 204 C (C – ½ Mo) and SA 302 B (C – Mn – ½ Mo) or SA 302 C (C – Mn – ½ Mo – ½ Ni) are shown to be better candidates for construction in lieu of low chromium alloy steel materials such as SA 387 grades P11 (1¼ Cr – ½ Mo), P12 (1 Cr – ½ Mo), P22 (2¼ Cr – 1 Mo) and P21 (3 Cr – 1 Mo).

Design and Robustness of Quilt Packaging Superconnect

2012 ◽  
Vol 2012 (1) ◽  
pp. 000524-000530
Author(s):  
M. Ashraf Khan ◽  
Jason M. Kulick ◽  
Alfred M. Kriman ◽  
Gary H. Bernstein
Keyword(s):  
Thermal Cycling ◽  
High Speed ◽  
Low Cycle Fatigue ◽  
Simulation Models ◽  
Electrical Performance ◽  
Cycle Fatigue ◽  
Signal Delay ◽  
Thermal Reliability ◽  
Simulation Results ◽  
Quilt Packaging

Quilt Packaging (QP) is a novel high-speed superconnect (i.e. direct interchip interconnect), developed to improve electrical performance — signal delay, power loss, etc. Ultrahigh bandwidth has already been demonstrated for QP, but its unique structure requires thermal reliability issues to be studied. To this end, simulation models were developed to study the robustness of QP. QP structures were fabricated, and thermal cycling tests were performed focusing on the reliability for various shapes of nodules, the basic physical interconnect unit of QP. Simulations were performed to determine stress over a range of temperatures and estimate low cycle fatigue lifetimes. Simulations considered two types of solder and several adhesives. Thermal cycling experiments indicate that QP provides a robust structure, in agreement with the simulation results.

A Study on the Low Cycle Fatigue Behavior of the Steel for Shipbuilding Industry

2005 ◽  
Vol 297-300 ◽  
pp. 10-15 ◽  
Author(s):  
Kyung Su Kim ◽  
Byung Ok Kim ◽  
Young Kwan Kim ◽  
Chang Hwan Lee ◽  
Sung Won Lee
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Published Data ◽  
Cycle Fatigue ◽  
Maritime Industry ◽  
Shipbuilding Industry ◽  
Design Procedures ◽  
Calculation Results ◽  
Good Agreement

Recently, most of fatigue cracks in ship structures are reported within a few years after delivery. This type of fatigue characteristics cannot be explained adequately by the S-N curve based on high cycle fatigue. Calculation results under critical loading conditions reveal that stress magnitude higher than three times the yield stress occurs at some critical locations. It shows the fatigue cracks are related to low cycle fatigue. But the existing recommended design procedures in maritime industry do not properly cover low cycle fatigue problems. This work represents the first step in an effort to develop a design code that addresses low cycle fatigue problems. Low cycle fatigue test for uniform round specimen made of base/weld metal and for cruciform welded joint are carried out under constant amplitude alternating load, controlled by strain. Strain-cycle curves for the base metal and weld joints show good agreement with published data as well as some code recommended design curves.

Numerical Study of an Impusively Loaded Vessel Containing Double Versus Single Closure Bolt Patterns

2017 ◽  
Author(s):  
Joseph E. D. Hess
Keyword(s):  
Finite Element ◽  
Structural Integrity ◽  
Numerical Study ◽  
Axial Loading ◽  
Element Model ◽  
Pressure Vessels ◽  
Bolted Joint ◽  
Single Row ◽  
Asme Code ◽  
Calculation Results

Impulsively loaded pressure vessels are often closed using a bolted joint configured in a double staggered row pattern. The bolted joint design must maintain the placement of the vessel opening covers to support the structural integrity of the shell and also provide the necessary preload of sealing surfaces for leak prevention. Good design practice suggests configuring tensile loaded bolted joints with a double rows pattern in order to minimize prying against the bolt head induced by localized moments. Double bolt row patterns allow moments induced by load offsets to be reacted through contact of the faying surfaces of the bolted members and if separation occurs by differential axial loading of the two bolt rows. This acts to reduce direct prying of the mated members against the bolt heads. Material cost and operational time savings could be realized if a single bolt row design with acceptable performance was implemented. In this paper a detailed finite element model is described and calculation results are presented for two vessel configurations subjected to an impulsive load; a double staggered 64 bolt pattern and a single row 32 bolt pattern. Finite element results are compared to each other and to the rules of ASME Code Case 2564 in Section VIII, Division 3. Special attention is given to the loading induced in the bolts and to the relative deflection of faying surfaces containing seals. It will be shown that reducing the bolt count per opening from 64 to 32 results in increased peak response of the bolts, seal opening gaps, and shell. Nonetheless a single row bolt pattern does appear feasible and within the bounds of the Code Case.

Low-Cycle Fatigue under Biaxial Stress

1974 ◽  
Vol 188 (1) ◽  
pp. 657-671 ◽  
Author(s):  
M. W. Parsons ◽  
K. J. Pascoe
Keyword(s):  
Austenitic Steel ◽  
Abrupt Change ◽  
Low Cycle Fatigue ◽  
Axial Loading ◽  
Strain Range ◽  
Fatigue Behaviour ◽  
Biaxial Stress ◽  
Cycle Fatigue ◽  
Biaxial Strain ◽  
Total Strain Range

The low-cycle fatigue behaviour of a ferritic and an austenitic steel have been studied under various conditions of reversed biaxial strain. These cyclically softened and hardened respectively. In all cases, relationships of the form were found between total strain range Δε t and life Nf for lives in the range 102−105 cycles, with an abrupt change of β at intermediate lives. Variation of state of strain affected both β and κ. Various theories for the correlation of fatigue behaviour under multi-axial loading have been reviewed and compared with these results. None was found to account adequately for the effect of straining régime with the materials tested.

Short fatigue crack behaviour of LZ50 railway axle steel under multi-axial loading in low-cycle fatigue

2020 ◽  
Vol 132 ◽  
pp. 105366 ◽  
Author(s):  
Zhen Liao ◽  
Bing Yang ◽  
Yahang Qin ◽  
Shoune Xiao ◽  
Guangwu Yang ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Low Cycle Fatigue ◽  
Axial Loading ◽  
Cycle Fatigue ◽  
Short Fatigue Crack ◽  
Railway Axle
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