Numerical Analysis of Plate Thickness Effect on Residual Stress Distribution around a Cold Expanded Hole

The process of cold expansion creates compressive stresses around the mounting hole, which can help to reduce stress concentrations during the loading of a structure. A numerical simulation using the finite element method was conducted to analyse the effect of cold expansion on perforated plates of different thicknesses. The simulation considered the thickness of the plate and the tapered mandrel and examined the induced residual stresses. The results showed that the magnitude of the circumferential residual stresses varied depending on the thickness of the plate and that the extent of the zone of compressive stresses was strongly affected by the plate thickness. These findings are particularly relevant to the optimisation of the cold expansion process, as the optimal parameters for a particular plate thickness may not be optimal for some other thickness. Therefore, the results of this study can guide the optimisation of the cold expansion process for different plate thicknesses

Finite element based fatigue analysis of 6082 Aluminum alloy under random loading

Mechanical and structural components are subject in the most cases during their services to random loading. For this reason, it is necessary to reduce the complex history of these kinds of loading in a series of constant amplitude cycles. There are several counting methods that lead to different results. Among all these methods, it is recognized that the Rainflow Cycle Counting method provides the most conservative results. In this paper, a finite elements analysis technique is presented to predict the fatigue life using this method associate with the S-N method which is used for high cycle fatigue applications that makes no distinction between initiation or growing a crack, but rather, predicts the total life to failure. Comparison between numerical and experimental results is considering in this paper.

Finite element based fatigue analysis of 6082 Aluminum alloy under random loading

Mechanical and structural components are subject in the most cases during their services to random loading. For this reason, it is necessary to reduce the complex history of these kinds of loading in a series of constant amplitude cycles. There are several counting methods that lead to different results. Among all these methods, it is recognized that the Rainflow Cycle Counting method provides the most conservative results. In this paper, a finite elements analysis technique is presented to predict the fatigue life using this method associate with the S-N method which is used for high cycle fatigue applications that makes no distinction between initiation or growing a crack, but rather, predicts the total life to failure. Comparison between numerical and experimental results is considering in this paper.

A 3D analysis of crack-front shape of asymmetric repaired aluminum panels with composite patches

Through this study, a numerical simulation based on 3D in order to investigate the effect of Crack-front shape on the stress intensity factor and fatigue crack growth behavior of center cracked aluminum plate repaired asymmetrically with a bonded composite patch. Consequently, Skew degree is a significant effect on stress intensity factor (SIF) distribution along the crack front in thick panels more than thin panels. Moreover, Fatigue life was calculated using different averages stress intensity factor of patched panel determined from the uniform crack front model and skew crack front model obtained from FEM and when comparing fatigue life values obtained from the finite element model with experimental values were shown a good agreement

Numerical Analysis and Optimization of the Residual Stresses Distribution Induced by Cold Expansion Technique

Abstract. This paper presents a numerical investigation about the influence of mandrel shape on residual stresses induced by the cold expansion procedure. Thus, ball and tapered pin are used for cold expanding the plate. As, the entrance face presents the lowest residual stresses throughout the hole thickness, we propose to solve this problem by varying the mandrel taper degree, instead of applying a double expansion.  The obtained results show that the tapered pin is more suitable for the cold expansion. More, low taper increases the residual stresses at the entrance, reaching the values generated at the exit face

Finite element modeling and analytical solution of a semi-elliptic crack's Jintegral

In this work, we first evaluate the J-integral rupture parameter as a function of various crack parameters (crack size, rod dimensions, intensity and nature of loads) for various crack form. In a second step, and in the base of the results obtained by the finite element method, we propose formulas of the factor shape, whose implementation remains rather simple and inexpensive in terms of time, effort and means to the engineer in order to predict evolution of the rupture behavior of a cylindrical component with a semielliptical crack emerging from the surface. The comparison of the proposed analytical solution showed a good performance relatively with results of the literature

Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6

Hole cold expansion (HCE) is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue damage accumulation of cold expanded hole in aluminum alloy which is widely used in transportation and in aeronautics was analyzed. Experimental tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. These tests were performed by using two and four blocks under uniaxial constant amplitude loading. The increasing and decreasing loading were carried. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the 'damaged stress model', which takes into account the loading history, yields a good estimation according to the experimental results. Moreover, the error is minimized in comparison to the Miner's model

Finite Elements Analysis of a Butterfly-Shaped Composite patch Repair and its Comparison to the Usual Shapes

A 3-D finite element analysis was conducted on a thin aluminum plate with a 45 ° inclined central crack.  A modeling of the bonding repair with composite patch of different shapes was carried out. In addition to the patch shapes studied in the literature, a new butterfly shape was proposed. The latter is defined by a length H, a width B and a neck C in the middle. The main objective is to analyze the effect of patch geometry on the rate of decrease of stress intensity factors. This rate is characterized by a coefficient R which combines between the mode I and the mode II of the rupture (KI and KII). Thus, an optimization of the patch shape is made with respect to the effectiveness in decreasing the stress intensity factor. The comparison between the results obtained with the different patch shapes has shown that the butterfly-shaped patch is more effective for relatively small surfaces. On the other hand, the extended octagon shape has been shown to be more effective for higher patch surfaces

Finite Elements Analysis of a Butterfly-Shaped Composite patch Repair and its Comparison to the Usual Shapes

A 3-D finite element analysis was conducted on a thin aluminum plate with a 45 ° inclined central crack.  A modeling of the bonding repair with composite patch of different shapes was carried out. In addition to the patch shapes studied in the literature, a new butterfly shape was proposed. The latter is defined by a length H, a width B and a neck C in the middle. The main objective is to analyze the effect of patch geometry on the rate of decrease of stress intensity factors. This rate is characterized by a coefficient R which combines between the mode I and the mode II of the rupture (KI and KII). Thus, an optimization of the patch shape is made with respect to the effectiveness in decreasing the stress intensity factor. The comparison between the results obtained with the different patch shapes has shown that the butterfly-shaped patch is more effective for relatively small surfaces. On the other hand, the extended octagon shape has been shown to be more effective for higher patch surfaces

Finite Elements Analysis of a Butterfly-Shaped Composite patch Repair and its Comparison to the Usual Shapes

A 3-D finite element analysis was conducted on a thin aluminum plate with a 45 ° inclined central crack.  A modeling of the bonding repair with composite patch of different shapes was carried out. In addition to the patch shapes studied in the literature, a new butterfly shape was proposed. The latter is defined by a length H, a width B and a neck C in the middle. The main objective is to analyze the effect of patch geometry on the rate of decrease of stress intensity factors. This rate is characterized by a coefficient R which combines between the mode I and the mode II of the rupture (KI and KII). Thus, an optimization of the patch shape is made with respect to the effectiveness in decreasing the stress intensity factor. The comparison between the results obtained with the different patch shapes has shown that the butterfly-shaped patch is more effective for relatively small surfaces. On the other hand, the extended octagon shape has been shown to be more effective for higher patch surfaces