Prediction of Fatigue Crack Growth Rate and Stress Intensity Factors Using the Finite Element Method

This study investigates crack growth and stress intensity factors via finite element methods in linear elastic fracture mechanics. The procedure involves estimating stress intensity factors (SIFs), crack trajectory, and fatigue life, using two different softwares in both two and three-dimensional analyses. Crack modeling was done in a variety of ways depending on the software. ANSYS Mechanical R19.2 and FRANC2D/L software were used to prognosticate fatigue crack growth, fatigue life, and associated stress intensity factors under plane stress state. Fatigue analysis was governed by Paris’s law and crack growth direction by the theory of maximum circumferential stress. The results show that the fatigue growth was attracted to the hole and either changes its direction to reach the hole or floats by the hole and grows as the hole is missed. The findings of the study agree with other experimental and numerical crack propagation studies presented in the literature

Two- and Three-Dimensional Numerical Investigation of the Influence of Holes on the Fatigue Crack Growth Path

Problems in fracture mechanics are difficult when the appropriate analysis is unspecified, which is very common in most real-life situations. Finite element modeling is thus demonstrated to be an essential technique to overcome these problems. There are currently various software tools available for modeling fracture mechanics problems, but they are usually difficult to use, and obtaining accurate results is not an obvious task. This paper illustrates some procedures in two finite element programs to solve problems in two- and three-dimensional linear-elastic fracture mechanics, and an educational proposal is made to use this software for a better understanding of fracture mechanics. Crack modeling was done in a variety of ways depending on the software. The first is the well-known ANSYS, which is usually utilized in industry, and the second was a freely distributed code, called FRANC2D/L, from Cornell University. These software applications were used to predict the fatigue crack growth path as well as the associated stress intensity factors. The predicted results demonstrate that the fatigue crack is turned towards the hole. The fatigue crack growth paths are influenced by the varying positions and sizes of single holes, while two symmetrically distributed holes have no effect on the fatigue crack growth direction. The findings of the study agree with other experimental crack propagation studies presented in the literature that reveal similar crack propagation trajectory observations

Investigation on the Effect of Thermal and Mechanical Treatment to the Offshore Corrosion Behavior of 6351 Aluminum Alloy in Red Sea Environments

This study investigates the effect of artificial aging treatment and mechanical attrition treatment on the corrosion behavior of 6351 Al alloy in Red Sea environment. The artificial aging of the alloy is carried out at temperature range 140°C–240°C in steps of 20°C for various time periods after the solution heat treatment at 530°C for 1 hour. Based on the hardness measurements, the aged specimens are categorized into three, namely, underaged, peak aged, and overaged. The as received alloy specimens are subjected to mechanical attrition treatment in a vacuum chamber using steel balls. Vickers hardness test reveals that there is a remarkable improvement in hardness of mechanical attrition treated specimens compared to that of aged specimens. The aged and mechanical attrition treated specimens were subjected to the corrosion test in Red Sea water using the Autolab instrument. The corrosion tests reveal that the peak-aged composite corrodes more in Red Sea water when compared to that of other groups of specimens. XRD measurements and SEM analysis are carried out to study the surface nature of attrition treated specimens. It is observed that the mechanical attrition treated specimens exhibit a nanocrystalline surface and lead to a decrease in corrosion resistance. However, the annealing of the alloy after attrition treatment optimizes the mechanical and corrosion properties of the alloy

A Computational Framework for 2D Crack Growth Based on the Adaptive Finite Element Method

As a part of a damage tolerance assessment, the goal of this research is to estimate the two-dimensional crack propagation trajectory and its accompanying stress intensity factors (SIFs) using the adaptive finite element method. The adaptive finite element code was developed using the Visual Fortran language. The advancing-front method is used to construct an adaptive mesh structure, whereas the singularity is represented through construction of quarter-point single elements around the crack tip. To generate an optimal mesh, an adaptive mesh refinement procedure based on the posteriori norm stress error estimator is used. The splitting node strategy is used to model the fracture, and the trajectory follows the successive linear extensions for every crack increment. The stress intensity factors (SIFs) for each crack extension increment are calculated using the displacement extrapolation technique. The direction of crack propagation is determined using the theory of maximum circumferential stress. The present study is carried out for two geometries, namely a rectangular structure with two holes and one central crack, and a cracked plate with four holes. The results demonstrate that, depending on the position of the hole, the crack propagates in the direction of the hole due to the unequal stresses at the crack tip, which are caused by the hole’s influence. The results are consistent with other numerical investigations for predicting crack propagation trajectories and SIFs

Numerical Simulation of Mixed-Mode Fatigue Crack Growth for Compact Tension Shear Specimen

This work concentrates on the fracture behaviour of the compact tension specimen under mixed-mode loading, and numerical investigation using ANSYS Mechanical APDL 19.2 finite element program with different modes of mix angles is carried out. The prediction of mixed-mode fatigue life under constant amplitude fatigue loading for the compact tension shear specimen (CTS) is employed using Paris’ law model for two different loading angles with agreement to the experimental results. The predicted values of ΔKeq were compared with the experimental and analytical data for various models. Depending on the analysis, the findings of the present study show consistency with the results achieved with similar models of predicting the equivalent stress intensity factor. In addition, the direction of crack growth derived from the analysis was observed to follow the same trend of the literature experimental results

Numerical Analysis of Fatigue Crack Growth Path and Life Predictions for Linear Elastic Material

The main objective of this work was to present a numerical modelling of crack growth path in linear elastic materials under mixed-mode loadings, as well as to study the effect of presence of a hole on fatigue crack propagation and fatigue life in a modified compact tension specimen under constant amplitude loading condition. The ANSYS Mechanical APDL 19.2 is implemented for accurate prediction of the crack propagation paths and the associated fatigue life under constant amplitude loading conditions using a new feature in ANSYS which is the smart crack growth technique. The Paris law model has been employed for the evaluation of the mixed-mode fatigue life for the modified compact tension specimen (MCTS) with different configuration of MCTS under the linear elastic fracture mechanics (LEFM) assumption. The approach involves accurate evaluation of stress intensity factors (SIFs), path of crack growth and a fatigue life evaluation through an incremental crack extension analysis. Fatigue crack growth results indicate that the fatigue crack has always been attracted to the hole, so either it can only curve its path and propagate towards the hole, or it can only float from the hole and grow further once the hole has been lost. In terms of trajectories of crack propagation under mixed-mode load conditions, the results of this study are validated with several crack propagation experiments published in literature showing the similar observations. Accurate results of the predicted fatigue life were achieved compared to the two-dimensional data performed by other researchers

A Comparative Analysis of 3D Software for Modeling Fatigue Crack Growth: A Review

Fatigue crack growth modeling is critical for assessing structural integrity in various engineering applications. Researchers and engineers rely on 3D software tools to predict crack propagation accurately. However, choosing the right software can be challenging due to the plethora of available options. This study aimed to systematically compare and evaluate the suitability of seven prominent 3D modeling software packages for fatigue crack growth analysis in specific applications. The selected software tools, namely ABAQUS, FRANC3D, ZENCRACK, LYNX, FEMFAT, COMSOL Multiphysics, and ANSYS, were subjected to a comprehensive analysis to assess their effectiveness in accurately predicting crack propagation. Additionally, this study aimed to highlight the distinctive features and limitations associated with each software package. By conducting this systematic comparison, researchers and engineers can gain valuable insights into the strengths and weaknesses of these software tools, enabling them to make informed decisions when choosing the most appropriate software for their fatigue crack growth analysis needs. Such evaluations contribute to advancing the field by enhancing the understanding and utilization of these 3D modeling software packages, ultimately improving the accuracy and reliability of structural integrity assessments in relevant applications

Performance Assessment of Three Latent Heat Storage Designs for a Solar Hot Water Tank

Solar hot water tanks (SHWT) based on a latent heat storage system are gaining momentum for their integration into solar heater water collectors. They can efficiently store daytime solar thermal energy and shift on-peak period loads to off-peak periods. However, their performance is generally limited by the tank configuration, the design of the thermal storage system, and the selection of the appropriate phase change material (PCM). This work presents a numerical investigation of three SHWT-PCM storage designs. A mathematical model was developed to predict the effectiveness of the geometric design and operating conditions in the SHWT-PCM system. Moreover, a sensitivity analysis was performed on the PCM type and PCM thermo-physical properties. The obtained numerical results demonstrated that the energy efficiency of the SHWT-PCM system was significantly impacted by the PCM thermo-physical properties (melting temperature, thermal conductivity, and enthalpy). In addition, it was found that using encapsulated PCM tubes with an external PCM jacket in the SHWT can result in a thermal efficiency of 70%

Finite Element Simulation of a Crack Growth in the Presence of a Hole in the Vicinity of the Crack Trajectory

The aim of this paper was to present a numerical simulation of a crack growth path and associated stress intensity factors (SIFs) for linear elastic material. The influence of the holes’ position and pre-crack locations in the crack growth direction were investigated. For this purpose, ANSYS Mechanical R19.2 was introduced with the use of a new feature known as Separating Morphing and Adaptive Remeshing Technology (SMART) dependent on the Unstructured Mesh Method (UMM), which can reduce the meshing time from up to several days to a few minutes, eliminating long preprocessing sessions. The presence of a hole near a propagating crack causes a deviation in the crack path. If the hole is close enough to the crack path, the crack may stop at the edge of the hole, resulting in crack arrest. The present study was carried out for two geometries, namely a cracked plate with four holes and a plate with a circular hole, and an edge crack with different pre-crack locations. Under linear elastic fracture mechanics (LEFM), the maximum circumferential stress criterion is applied as a direction criterion. Depending on the position of the hole, the results reveal that the crack propagates in the direction of the hole due to the uneven stresses at the crack tip, which are consequences of the hole’s influence. The results of this modeling are validated in terms of crack growth trajectories and SIFs by several crack growth studies reported in the literature that show trustworthy results