Springer Science and Business Media LLC

Stretch flanging is the important sheet metal-forming process which is widely used in automobile and aerospace sectors. The formability of sheet metal depends on various parameters such as material properties, geometry of the tool setup and process parameters. In the present work, effects of different die radius and sheet width on deformation behavior of sheet are studied by FEM simulation and experiments. The predicted FEM results are presented in the form of edge crack location and its propagation, crack length, forming load and strain distribution in sheet along the die profile radius. This study indicates that crack length increases with increase in the sheet width, while the crack length decreases with increase in the die radius. It is found that the crack propagation in stretch flanging process is affected by the strain distribution in sheet and this distribution of strain depends on many parameters. The crack initiates during deformation of the sheet at the die corner edge and propagates toward the center of the sheet along the die profile radius. Simulation results are compared with the experimental one in terms of crack length and variation in sheet thickness. FE simulation results are found in very good agreement with experimental results. Fractography study is also presented in terms of size, shape of the dimples along with their distribution on the fractured surface.

The survivability of artillery projectile 155-mm Extended Range Full Bore Boat Tail (ERFB BT) inside gun barrel during gun launch mainly depends upon the mechanical properties of the shell body, boat tail and driving band materials. Any abrupt change in geometry of any one of these components can impair the structural integrity of the projectile, thereby resulting in malfunctioning of the projectile. Investigating the effect of abrupt change in geometry of the components is of much significance for assessing structural integrity. To investigate the effect of abrupt change in geometry of the components on structural failure, the notch tensile tests are performed to quantify the data on notch strength ratio (NSR), stress triaxiality and true fracture strain of the materials. To identify the mode of failure, the fractographic examination of the fracture surfaces is made. NSR is found more than unity; stress triaxiality determined by applying Bridgman’s analysis reveals notch strengthening behavior of the materials. The fractographic examination shows that the shell body and boat tail materials fail in the combined ductile and brittle mode, whereas the driving band material fails by ductile mode. The outcome of the investigation confirms the load-carrying capacity and structural integrity of the projectile.

The finite element (FE) predictions of single-bolt connections shear-out failure in the literature were conducted with only elastic–plastic material models without any fracture model. This paper presents the FE single-bolt connection shear-out fracture (SBCSOF) prediction and failure analysis using the phenomenological shear fracture model. It is established that FE simulations without any fracture model employed in the literature cannot predict SBCSOF and thus cannot be employed for FE SBCSOF failure analysis. Consequently, it is essential to incorporate fracture model(s) for FE SBCSOF prediction and failure analysis. Analyses of the experimental and predicted SBCSOF shapes reveal that the shear fracture consists of a long main shear fracture which occurs under combined shear and compressive bending deformations, and a short shear lip that is oppositely inclined to the main shear fracture which occurs under combined shear and tensile bending deformations. The work thus presents the appropriate FE SBCSOF failure analysis technique that serves as a useful tool for in-service failure analysis when fractographic analysis is impracticable. The FE SBCSOF failure analysis technique could also serves as a tool for the parametric studies of connection parameters on the fracture behavior of single-bolt shear connections that exhibit the shear-out fracture mode.

A metallurgical and mechanical failure analysis was applied as part of a vehicle accident reconstruction of a multi-vehicle collision. One of these vehicles was a coal-hauling tractor-trailer. Examination of the trailer involved in the incident revealed a fatigue fracture to a primary lateral stiffener, along with a significant misalignment of the stiffener. Stress and fatigue analysis indicated that the misalignment severely degraded the fatigue life of the stiffener. Evaluation of the structural dynamics of the trailer after the fatigue fracture indicated decreased lateral stability. The decreased stability caused by fracture of the lateral stiffener allowed rollover of the trailer to occur while negotiating a curve. The failure sequence developed in this investigation proved consistent with all physical damage observed on the trailer and with witness accounts of the incident. The failure scenario developed in this investigation is compared with other conclusions made by other investigators to show that those conclusions are not consistent with all of the available evidence.