Strength reduction in structures like an aircraft could be resulted as cyclic loads over a period of time and is an important factor for structural life prediction. Service loads are emphasized at the regions of stress concentration, mostly at the connection of components. The initial flaw prompting the service life was expected by using the Equivalent Initial Flaw Size (EIFS), which has been recognized as a powerful design tool for life prediction of engineering structures. This method was introduced 30 years ago in an attempt to study the initial quality of structural details. In this paper, the prediction of life based on failure mechanics in a Riveted joint has been addressed through the concept of EIFS. For estimation of initial crack length by EIFS, extrapolation method has been used. The EIFS value is estimated using the coefficient of cyclic intensity (Δ K) and using the cyclic integral (Δ J), and the results are compared with each other. The simulation results show that the if the coefficient of tension been used in EIFS estimation, which based on the Paris law, the EIFS value will be dependent on the loading domain, while the use of the J-Cyclic integral in the EIFS decrease its dependence on the load domain dramatically.

In aeronautical and automotive industries the use of Rivets for applications requiring several joining points is now very common. In spite of a very simple shape, a Riveted junction has many contact surfaces and stress concentrations that make the local stiffness very difficult to be calculated. To overcome this difficulty, commonly finite element models with very dense meshes are performed for single joint analysis because the accuracy is crucial for a correct structural analysis. Anyhow, when several Riveted joints are present, the simulation becomes computationally too heavy and usually significant restrictions to joint modelling are introduced, sacrificing the accuracy of local stiffness evaluation. In this paper, we tested the accuracy of a Rivet finite element presented in previous works by the authors. The structural behaviour of a lap joint specimen with a Rivet joining is simulated numerically and compared to experimental measurements. The Rivet Element, based on a closed-form solution of a reference theoretical model of the Rivet joint, simulates local and overall stiffness of the junction combining high accuracy with low degrees of freedom contribution. In this paper the Rivet Element performances are compared to that of a FE non-linear model of the Rivet, built with solid elements and dense mesh, and to experimental data. The promising results reported allow to consider the Rivet Element able to simulate, with a great accuracy, actual structures with several Rivet connections.

IntroductionPenetrating cardiac injuries generally occur secondary to gunshot or stab wounds and have a high mortality rate. They are rare and often fatal in children. When a foreign object penetrates the myocardium, it is dangerous to remove it, suddenly, and should be removed gradually to prevent excessive bleeding.Case reportWe report a case of an unusual penetrating cardiac injury in a 12-year-old boy with a Rivet pushed into his sternum and penetrating the right ventricle. After the patient underwent sternotomy and pericardiotomy, the site of the Rivet was exposed. A purse was then sutured around the Rivet and tightened while pulling it out. The patient was discharged five days post-op, with normal echocardiography after 12 months. A review of the English-written literature revealed that this is the first case of heart trauma with Rivet.

Till now, various models have been proposed in literature to simulate the behavior of Riveted structures. In order to find the most accurate analytical method in modeling the dynamic behavior of Riveted structures, a comparison study is performed on several of these models, in this research. For this purpose, experimental modal analysis tests are conducted on a Riveted plate to verify the efficacy of the analytical models. Moreover, finite element model updating is used to reduce the difference between analytical and experimental results. First, the material properties of plates are optimized using the experimental results obtained from modal tests of a simple plate. Next, the optimization is performed for the physical properties of Rivet. At the end, it is concluded that the fastener model proposed by Rutman can bring about the most accurate results when it is used in combination with solid plates and gap elements in the contact region.

Metal sheets play an important role in the mechanical design, particularly in the aerospace structures. Various parameters affect the quality of this operation. In this paper, optimization of the parameters contributing to the Riveting quality in order to minimize the value of the maximum tangential stress in metal sheets is addressed. hence, the tolerance of the hole diameter in top and bottom sheets, the friction coefficient, and the tolerance of the Rivet diameter and the Rivet length were considered as the parameters influencing the Riveting quality. A total of 64 models were obtained by permutations of the parameters, two at a time. The outputs were determined using finite element method. The objective function for optimization is the maximum tangential stress for which there is no analytical relation. Thus, three methods including the multivariable linear regression (MLR), the artificial neural network model of the radial basis function (RBF) type, and the hybrid model of the artificial neural network and the genetic algorithm (ANN-GA) were employed to model this function. Further, the performance of the three models was compared and the most suitable one was selected to model the objective function. The regression model was used to model the values of the height and the diameter after Riveting. The imperialist competitive algorithm is utilized to solve this optimization problem. The obtained value for the maximum tangential stress using the imperialist competitive algorithm is 16368 pounds per square inches. After modification, this value increased to 23440 pounds per square inches using the finite element method. After Riveting, the height and diameter of the Rivet were respectively measured to be 0.07689 inches and 0.18524 inches.

The wire drawing process is extensively used in manufacturing components such as Rivet, screw, welding wire, etc. In this work, an analytical of the wire drawing process has been considered for two-stage operation. ABAQUS commercial Finite Element code has been used to obtain the drawing force. Then, the analytical and experimental results were compared. The results show a good agreement for copper.

In this paper, experimental investigation was performed to estimate fatigue life of single and double Riveted coach peel joints of 2024 aluminum alloy. Load controlled fatigue tests were conducted with load ratio and frequency of 0. 1 and 10 Hz, respectively. Failure of the specimens revealed three major modes of folded region fracture (A-type), fracture from edge of the Rivet hole (B-type) and mixed mode fracture (A & B). Although all failure modes contributes equally in single Riveted joint, mixed mode fracture was observed as dominant mode in two Riveted ones. A numerical approach is applied to estimate fatigue life of Riveted coach peel joints. Finite element analysis was implemented by ABAQUS as the first step of this approach to estimate stress distribution, stress concentration factor, stress and strain amplitude. Fatigue lives were then calculated using three fatigue life theories of Monson-Hirschberg, Smith-Watson-Topper and Morrow. Finally, good accordance between numerical and experimental results revealed that the finite element approach combined with fatigue life theories is capable for fatigue life prediction. It is concluded that adding a Rivet in longitudinal direction to the single Riveted coach peel joint decreases the life cycles by increasing the stress concentration factor. Moreover, results of finite element approach showed that Monson-Hirschberg and experimental data has the best agreement in compare with SWT and Morrow.