Research on the integral forming process of thin walled and thick mouth seamless gas cylinders.

There is a considerable difference in wall thickness between the mouth and the cavity of thin-walled and thick-mouthed seamless gas cylinders, and the existing manufacturing processes are unable to effectively meet product requirements. To overcome such issue, a step-by-step boring-necking-spinning solution for gas cylinders was proposed, in which sufficient wall thickness is reserved for the mouth area of the cylinder blank, followed by necking-spinning to realize the overall forming of thin-walled, thick-mouthed seamless gas cylinders. The stress-strain distribution and geometric dimensional changes of gas cylinders during the spinning process were investigated by means of finite element simulation, and the effects of different process parameters on the stress and wall thickness of the bottle mouth were analyzed. Further, multi-objective optimization of the response surface model was performed using the NSGA-II algorithm to derive a set of optimal process parameters. Finally, the correctness of the simulation and optimization results was verified experimentally, and the expected geometry and optimal strain state of the gas cylinder were obtained. The newly developed processing solution represents a groundbreaking advancement in the manufacturing of thin-walled and thick-mouthed gas cylinders.

Crack mechanism and experimental verification on straightening of AZ31B magnesium alloy plate.

When plates with edge cracks in the rolling process is straightened by cyclic tensile and compressive stress, the tip of edge crack always accompanied by stress concentration, which leads to crack propagation. In this paper, damage parameters are imported into the plate straightening model based on determining the GTN damage parameters of magnesium alloy materials by inverse finite element calibration method, the influence of different straightening process schemes and prefabricated V-shaped crack geometry on crack growth is analyzed through the way of the combination of simulation and straightening experiment. The results show that the peak values of equivalent stress and equivalent strain under each straightening roll appear at the crack tip. The value of longitudinal stress and equivalent stain decrease with the distance to crack tip becomes larger. The peak value of longitudinal stress appears when the crack circumferential angle is about 100°, and the crack tip is easy to form crack propagation; when the plate passes roll 2 and roll 4, the equivalent stress and strain concentration at the crack tip are most obvious; when the reduction reaches a certain degree, the void volume fraction (VVF) reaches the VVF of the material breaking; with the increase of the entrance reduction, the number of VVF at the crack tip which reaches the material fracture increases, and the length of crack propagation increases; the stress concentration at the tip of V-shaped crack with large length-width ratio is obvious, and the VVF is more likely to reach the VVF at the time of material fracture, crack initiates and propagates easily.

Torsion of ovarian endometrioma in pregnancy: a case report and review of the literature.

Adnexal torsion induced by an endometrioma has seldom been reported. Because of its rarity and its complexity in respect of fetal health during pregnancy, the diagnosis and treatment is challenging. We report a 25-year-old primigravida in the eighth week of gestation presenting with acute onset lower abdominal pain. A pelvic ultrasonography showed an intrauterine single viable embryo with a right ovarian cyst measuring 6 × 6 cm in diameter. Exploratory laparotomy revealed torsion of the right adnexa by 360°. After a right adnexectomy was performed, the patient proceeded to full-term pregnancy. Adnexal torsion is defined as rotation of > 45° in the long axis of the adnexae. Its occurrence during gestation is reported as 2%, accounting for 2.7% of surgical emergencies in pregnant women. Most cases are caused by dermoid and functional ovarian cysts. Because of the rarity of torsion induced by an endometrioma, the diagnosis and treatment are challenging. In poor-resource conditions, a diagnostic laparoscopy (or laparotomy) remains a logical method of diagnosis, offering simultaneous therapeutic options.