Meckel’s diverticulum represents a remnant of the proximal end of the omphalomesenteric duct, which constitutes a connection between the middle intestine and the vitelline vesicle. It is the most common congenital anomaly of the gastrointestinal tract and is found in approximately 0.3–2% of the general population. Complications such as hemorrhage, bowel obstruction, infl ammation, perforation, intussusception, volvulus and malignant transformation develop in only 4–4.8% of all patients, with most cases presenting in childhood, while relative risk decreases during life. The aim of the present study is to present our experience in managing a 15-year old male patient with Meckel’s diverticulum covered perforation. It was a case of disguised perforation of the Meckel’s diverticulum, with development of adhesions to the anterior surface of the right third of the transverse colon, which was successfully treated on the basis of emergency. Diagnosis was made intraoperatively and was documented by histological examination of the excised diverticulum.
This paper presents a numerical investigation of fracture criterion influence on perforation of high-strength 30PM steel plates subjected to 7.6251 mm Armour Piercing (AP) projectile. An evaluation of four ductile fracture models is performed to identify the most suitable fracture criterion. Included in the paper is the Modified Johnson-Cook (MJC) constitutive model coupled separately with one of these fracture criteria: the MJC fracture model, the Cockcroft-Latham (CL), the maximum shear stress and the constant failure strain models. A 3D explicit Lagrangian algorithm that includes both elements and particles, is used in this study to automatically convert distorted elements into meshless particles during the course of the computation. Numerical simulations are examined by comparing with the experimental results. The MJC fracture model formulated in the space of the stress triaxiality and the equivalent plastic strain to fracture were found capable of predicting the realistic fracture patterns and at the same time the correct projectile residual velocities. However, this study has shown that CL one parameter fracture criterion where only one simple material test is required for calibration is found to give good results as the MJC failure criterion. The maximum shear stress fracture criterion fails to capture the shear plugging failure and material fracture properties cannot be fully characterized with the constant fracture strain.
The aim of the study is to identify the relevant aspects of numerical analysis of impact of projectiles with soft cores into a package composed of thin flexible plies located on the plastic backing. In order to illustrate the problem, normal impact of 7.62 mm TT projectile into an unclamped package comprising 36 plies of Dyneema SB71 supported on the plastic backing was selected. The problem was solved with the use of the finite element method (FEM) with the explicit integration scheme (central difference method) of motion equations in the matrix form. Based on the conducted numerical computations, it was revealed that obtaining the extreme deformations of a projectile soft core and the backing material in Lagrangian description requires employment of adaptive methods. The proposed R-adaptive method performs its role but must be used carefully due to the mass loss which may appear during calculations.