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.

Reliability analysis of a structural element based on the Advanced First-Order-Second-Moment Method.

1985 ◽  
Vol 51 (472) ◽  
pp. 2811-2816
Author(s):  
Yoshisada MUROTSU ◽  
Masaaki YONEZAWA ◽  
Hiroo OKADA ◽  
Satoshi MATSUZAKI ◽  
Toshiki MATSUMOTO
Keyword(s):  
Reliability Analysis ◽  
Moment Method ◽  
Structural Element ◽  
Second Moment ◽  
First Order ◽  
First Order Second Moment ◽  
Second Moment Method

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.

scholarly journals Reliability Analysis Approach For Intersection Sight Distance Of A Symmetrical Single-Lane Roundabout

2021 ◽  
Author(s):  
Paria Sarshar
Keyword(s):  
Reliability Analysis ◽  
Safety Margin ◽  
Random Variables ◽  
Analysis Approach ◽  
Deterministic Models ◽  
Second Moment ◽  
First Order ◽  
Sight Distance ◽  
Design Variables ◽  
First Order Second Moment

The current intersection sight distance values on a roundabout provided by ASSHTO and other worldwide guidelines are based on deterministic methods considering only single variables as the design inputs. However, most of the input design variables such as entering speed and the deceleration rate are random variables which are stochastic in nature. Therefore, this study proposes a reliability analysis approach to add uncertainty to the current deterministic models. Two different reliability approaches; the first order second moment and advanced first order second moment are presented in this paper. These approaches rely on the normal distribution of the random variables using the mean, variance and the covariance of the probability distribution of each variable rather than the single deterministic values. Results show that the AFOSM reliability methodology provides a more conservative outcome which ensures a greater safety margin comparing to FOSM which appears to be a more efficient and robust methodology.

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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