Numerical Analysis of the Crack Growth in a High Loaded Bolt Connection

2007 ◽  
Vol 348-349 ◽  
pp. 625-628
Author(s):  
Marko Knez ◽  
Srečko Glodež ◽  
Janez Kramberger
Keyword(s):  
Crack Growth ◽  
Crack Size ◽  
Initial Crack ◽  
Structural Elements ◽  
Element Analysis ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Final Failure ◽  
Heavy Loads ◽  
Bolt Connection

The present paper deals with the research on the crack growth in a bolt connection of a lug for crane counter weight bars. Counter weight bars are structural elements that are subjected to very heavy loads and therefore special attention must be paid. The main purpose of this research is to determine the number of the load cycles required for a crack to propagate from initial to critical crack length, when the final failure can be expected to occur. All required material parameters and the experimental results were determined in our previous research. The influence of the initial crack size upon the remaining life of the lug is researched numerically by means of finite element analysis and analytically by use of the corrected analytical model.

Determination of Critical Crack Size Utilizing a Fracture Mechanics Test in Equipment Under Fatigue

2009 ◽  
Author(s):  
Irene Garcia Garcia ◽  
Radoslav Stefanovic
Keyword(s):  
Heat Treatment ◽  
Fracture Mechanics ◽  
Crack Size ◽  
Operational Experience ◽  
Element Analysis ◽  
Critical Crack ◽  
Circumferential Welds ◽  
Fea Model ◽  
Critical Crack Size

Equipment that is exposed to severe operational pressure and thermal cycling, like coke drums, usually suffer fatigue. As a result, equipment of this sort develop defects such as cracking in the circumferential welds. Operating companies are faced with the challenges of deciding what is the best way to prevent these defects, as well as determining how long they could operate if a defect is discovered. This paper discusses a methodology for fracture mechanics testing of coke drum welds, and calculations of the critical crack size. Representative samples are taken from production materials, and are welded employing production welding procedures. The material of construction is 1.25Cr-0.5Mo low alloy steel conforming to ASME SA-387 Gr 11 Class 2 in the normalized and tempered condition (N&T). Samples from three welding procedures (WPS) are tested: one for production, one for a repair with heat treatment, and one for repair without heat treatment. The position and orientation of test specimen are chosen based on previous surveys and operational experience on similar vessels that exhibited cracks during service. Fracture mechanics toughness testing is performed. Crack finite element analysis (FEA) model is used to determine the path-independed JI-integral driving force. Methodology for the determination of critical crack size is developed.

scholarly journals Subcritical crack growth parameters in glass as a function of environmental conditions

2020 ◽  
Author(s):  
Christopher Brokmann ◽  
Stefan Kolling ◽  
Jens Schneider
Keyword(s):  
Crack Growth ◽  
Environmental Conditions ◽  
Subcritical Crack Growth ◽  
Growth Parameters ◽  
Crack Depth ◽  
Indentation Test ◽  
Soda Lime ◽  
Initial Crack ◽  
Chemical Compositions ◽  
Critical Crack

Abstract In the present work, subcritical crack growth in soda–lime silicate glass is investigated under different environmental conditions. Crack growth parameters as a function of temperature and humidity were determined by dynamic fatigue tests, which has been verified by using the in-situ method of filming crack growth during experiments. The specimens were pre-damaged for constant initial crack lengths in all specimens using the Vickers indentation test. The determined parameters were compared with those from literature in order to discuss existing deviations of sub-critical crack growth parameters in literature. These deviations may be caused by environmental conditions and different chemical compositions of the glass. Arrest lines were used to determine the ratio of crack width to crack depth in Vickers indented specimens. For the initial crack depth, images of fracture surfaces were taken using an scanning electron microscope. Furthermore, the influence of humidity and temperature on the failure stress of unindented specimens with a constant initial crack length was simulated.

The Corrosion Morphology and Crack Growth Analysis of Aluminum Alloy

2011 ◽  
Vol 80-81 ◽  
pp. 464-468
Author(s):  
Zhi Tao Mu ◽  
Hui Liu ◽  
Zuo Tao Zhu ◽  
Ding Hai Chen
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Growth Analysis ◽  
Three Dimensional ◽  
Critical Crack ◽  
Corrosion Morphology ◽  
Critical Crack Length ◽  
Corrosion Depth ◽  
Corrosion Pits

The relation between corrosion depth and width with corrosion time is according with the power function. The corrosion pits can be seen as ellipse balls through the examination of QUESTAR three-dimensional optics microscope. Corrosion can decrease the fatigue life of materials and is the main reason of fatigue crack form and grow; through AFGROW analyze we can see that the AFGROW software can simulate crack growth life well and the error is low, the crack growth life and critical crack length are conservative than experiment values.

A New Model of Stochastic Crack Growth under Random Loading and Reliability Analysis of Fatigue Life

2007 ◽  
Vol 353-358 ◽  
pp. 81-84
Author(s):  
Hong Zhong Huang ◽  
G. Huang ◽  
Qiang Miao ◽  
Dan Ling ◽  
Q. Ma
Keyword(s):  
Reliability Analysis ◽  
Crack Growth ◽  
Critical Size ◽  
Crack Size ◽  
Initial Crack ◽  
Random Loading ◽  
New Model ◽  
First Order ◽  
Moment Approximation ◽  
First Order Second Moment

A new model is proposed for the analysis of fatigue crack growth under random loading. The fatigue rule of crack length is transformed into the monotony function rule based on types of the crack. By performing reliability analysis, the randomness of the stress, the stochastic nature of the crack growth, the fuzziness of the initial crack size and the randomness of the crack critical size are considered. The First-order-second-moment approximation method is used to obtain the solution of the probability density function. An example is given to illustrate feasibility of the proposed method.

scholarly journals Experimental and Numerical Investigations on Crack Propagation in Titanium Alloys

2018 ◽  
Vol 8 (04) ◽  
Author(s):  
Varimadugu Sandhya ◽  
Jyothirmayi Narne ◽  
Nagini Yerramsetty ◽  
V. Jaipal Reddy
Keyword(s):  
Titanium Alloys ◽  
Energy Release ◽  
Crack Growth ◽  
Cleavage Fracture ◽  
Tensile Load ◽  
Strain Energy Release ◽  
Tensile Tests ◽  
Tensile Specimen ◽  
Crack Size ◽  
Element Analysis

The titanium alloys are the objects of wide experimental analysis in the terms of crack growth characteristics and mechanism of fracture due to their applications. The Ti-6.4%Al-2.6%Mo-1.7%Cr-0.5%Fe-0.5%Si (wt %) alloy was used in the investigation. The tensile tests were conducted on plate specimens. The test variables considered are width of tensile specimen, crack size and tensile loading. The mechanism of fracture that appeared in the specimens was established from the TEM micrographs of the replicas taken from different zones of the fracture surfaces. The mechanism of fracture was also studied using finite element analysis. The results obtained from the FEA were verified with experimental results. It can be concluded that there is a general trend of increasing stress intensity factor with increasing applied tensile load, crack size and width of the flat specimen. The strain energy release increases with increasing applied tensile load. Crack extension can occur when crack-driving force is equal to the energy required for crack growth. For a particular stress the energy release rate is proportional to the crack size. As the tensile load and the size of the initial crack increase, there is an increased crack growth in the Ti alloy. In the crack initiation zone evidence of quasi-cleavage fracture with limited plastic striations symptoms was found in the specimen tested under  =1000MPa. Micro fracture analysis of the specimens (tested under =1100MPa) has revealed quasi-cleavage fracture with small symptoms of plastic shearing in the early part of cracking.

Assessment Method for Complex Cracked Pipe Using Equivalent Pipe Concept

2016 ◽  
Author(s):  
Kyung-Dong Bae ◽  
Ho-Wan Ryu ◽  
Seung-Jae Kim ◽  
Hyun-Suk Nam ◽  
Yun-Jae Kim
Keyword(s):  
Crack Growth ◽  
Surface Crack ◽  
Crack Size ◽  
Assessment Method ◽  
J Integral ◽  
Element Analysis ◽  
Welding Part ◽  
Complex Crack ◽  
Tensile Experiment ◽  
Damage Criteria

This paper proposes the assessment method of complex cracked pipes. Complex crack is the form of crack existing through-wall crack and surface crack at the same time [1–2]. Complex crack is mainly caused by PWSCC phenomenon in pipe with overlay maintenance welding. At first, circumferential surface crack is developed by PWSCC phenomenon in the weakest point which is nickel alloy welding point. And this crack propagates to axisymmetric crack in inner surface. After that the crack initiates in not only pipe part but also overlay maintenance welding part, complex crack shape which is main subject in this paper is formed. Unlike through-wall cracked pipes or surface cracked pipes, complex cracked pipes have a complex behavior because of combining through-wall crack behaviors and surface crack behaviors in cracked part. So calculating J-integral and defining amount of crack growth of complex cracked pipes are more difficult than those of through-wall cracked pipes and surface cracked pipes. Therefore, in this paper, the concept using equivalent pipe is proposed for assessment method of complex cracked pipes. To determine equivalent pipe, maximum loads of various through-wall cracked pipes having same circumferential crack size and different thickness are calculated. The reason why through-wall cracked pipe is selected for equivalent pipe is that many researches about J-integral and crack growth of through-wall cracked pipes are already performed and those results are sufficiently validated. In addition, it can be not only directly utilized procedure of leak before break assessment but also compared previous research results using only through-wall cracked part in complex cracked pipes referred to reduced thickness method. Maximum loads of complex cracked pipes and through-wall cracked pipes are calculated using stress-modified fracture strain model in finite element analysis [3–6]. This model is technics removing load bearing capacity in elements which satisfy damage criteria. Damage criteria is determined by using tensile experiment results, fracture toughness experiment results and validated by comparing with real size pipe experiment results. All the experiment results are in pipe fracture encyclopedia published by Battelle [7]. The experiments utilized in the paper are performed in operating temperature 288°C and materials of pipes are stainless steel SA376 TP304 and carbon steel A106 Gr.B. Finally, the results of equivalent through-wall cracked pipe thickness are provided.

Fracture Resistance of Ship Longitudinal Members Including Fatigue Crack

2013 ◽  
Author(s):  
Yann Quéméner ◽  
Chien-Hua Huang ◽  
Chi-Fang Lee
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Length ◽  
Crack Growth ◽  
Fracture Resistance ◽  
Crack Tip ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Extreme Loads

This study investigates the fracture failure of longitudinal members including cracks. Specifically, this study employs the failure assessment diagram methodology to assess the conditions of failure at the crack tip. Based on various crack configurations, this study establishes the analytical formulations of the crack-tip condition that are validated using finite element analyses. In addition, the material toughness is expressed in terms of crack-tip opening displacement. This study evaluates the failure stress of representative cracked members as a function of the crack length. This enables determining critical crack lengths corresponding to the maximum stresses derived from extreme loads. Finally, this study uses simplified fatigue crack growth analyses to characterize the critical crack length in terms of fatigue life. For members located in the deck and bottom regions, the critical crack lengths correspond to the end of the assessed fatigue life. Therefore, the fracture resistance of the longitudinal members is satisfactory as it will not cause the premature loss of the component. This study also provides analytical formulations for crack-tip conditions that could be employed in a reliability study linking fatigue crack growth and fracture under extreme loads.

Prediction of the Fatigue Life of the Vibrational Sieve Supporting Beam

2017 ◽  
Vol 755 ◽  
pp. 274-278
Author(s):  
Jelena M. Djoković ◽  
Ružica R. Nikolić ◽  
Jan Bujnak
Keyword(s):  
Fatigue Life ◽  
Crack Length ◽  
Crack Propagation Rate ◽  
Working Life ◽  
Propagation Rate ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Remaining Fatigue Life

Vibrational sieves are exposed to exceptionally high cyclic loading during their working life and that is the reason why the special attention should be paid to estimates of the fatigue life of their structural elements, as well as to design with respect to fatigue fracture. Any change in the design appearance of the structural component must be carefully analyzed, since even the rearrangement of the components' elements layout, with keeping all the sizes constant, can cause serious consequences to the particular component's fatigue life. The research subject considered in this paper is the remaining fatigue life of the carrying beam, as well as the suggestions for improving the working life of the vibrational sieve. The Paris' law was used for estimates of the average crack propagation rate. From the presented diagram of the initial crack length versus the remaining working life one could see that the fatigue life decreases with the crack length increase. When the initial crack length reaches a value a little less than a half of the critical crack length, the remaining fatigue life starts to drop abruptly.

Analysis of Crack Growth in a 3D Voronoi Structure: A Model for Fatigue in Low Density Trabecular Bone

2002 ◽  
Vol 124 (5) ◽  
pp. 512-520 ◽  
Author(s):  
A. M. Makiyama ◽  
S. Vajjhala ◽  
L. J. Gibson
Keyword(s):  
Fatigue Life ◽  
Relative Density ◽  
Trabecular Bone ◽  
Crack Growth ◽  
Three Dimensional ◽  
Crack Size ◽  
Initial Crack ◽  
Low Density ◽  
Cycle Fatigue ◽  
Crack Growth Model

Both creep and crack growth contribute to the reduction in modulus associated with fatigue loading in bone. Here we simulate crack growth and subsequent strut failure in fatigue in an open-cell, three-dimensional Voronoi structure which is similar to that of low density, osteoporotic bone. The model indicates that sequential failure of struts leads to a precipitous drop in modulus: the failure of 1% of the struts leads to about a 10% decrease in modulus. A parametric study is performed to assess the influence of normalized stress range, relative density, initial crack size, crack shape and cell geometry on the fatigue life. The fatigue life is most sensitive to the relative density and the initial crack length. The results lead to a quantitative expression for the fatigue life associated with crack growth. Data for the fatigue life of trabecular bone are compared with the crack growth model described in this paper, as well as with a previous model for creep of a three-dimensional Voronoi structure. In our models, creep dominates the fatigue behavior in low cycle fatigue while crack growth dominates in high cycle fatigue, consistent with previous observations on cortical bone. The large scatter in the trabecular bone fatigue data make it impossible to identify a transition between creep dominated fatigue and crack growth dominated fatigue. The parametric study of the crack growth model indicates that variations in relative density among specimens, initial crack size within trabeculae and crack shape could easily produce such variability in the test results.

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