Analysis of the Effect of Tungsten Inert Gas Welding Sequences on Residual Stress and Distortion of CFETR Vacuum Vessel Using Finite Element Simulations

The as-welded sectors of China Fusion Engineering Testing Reactor (CFETR) vacuum vessel (VV) have very tight tolerances. However, it is difficult to investigate the welding stress and distortion without the production of a full-scale prototype. Therefore, it is important to predict and reduce the welding stress and distortion to guarantee the final assembly by using an accurately adjusted finite element model. In this paper, a full-scale finite element model of the 1/32 VV mock-up was built by ABAQUS which is a powerful finite element software for engineering simulation, and three different tungsten inert gas (TIG) welding sequences were simulated to study the effect of welding sequences on the welding stress and distortion. The results showed that the main welding stress happened on the weld zone, and the maximum distortion occurred on the shell near the welding joints between the inboard segment (PS1) and the lower segment (PS4). The inboard segment (PS1), upper segment (PS2), and lower segment (PS4) distorted to inside of the shell perpendicularly, while the equatorial segment (PS3) distorted to outside of the shell perpendicularly. According to the further analysis, the maximum welding stresses in sequence 1, sequence 2, and sequence 3 were 234.509 MPa, 234.731 MPa, and 234.508 MPa, respectively, and the average welding stresses were 117.268 MPa, 117.367 MPa, and 117.241 MPa, respectively, meanwhile, the maximum welding displacements in sequence 1, sequence 2, and sequence 3 were 1.158 mm, 1.157 mm, and 1.149 mm, respectively, and the average welding displacements were 1.048 mm, 1.053 mm, and 1.042 mm, respectively. Thus, an optimized welding sequence 3 was obtained and could be applied to the practical assembly process of the 1/32 VV mock-up

Exploring risk factors for totally implantable venous access devices (TIVADs)-related thrombotic occlusion in the off-treatment period

Abstract Totally implantable venous access devices (TIVADs) have been widely used for many years in the management of patients suffering from cancer. Thrombotic occlusion is the most common functional complication in the off-treatment period. This study aims to investigate the incidence of and risk factors for TIVADs-related thrombotic occlusion in patients with breast cancer. The clinical data of 1586 eligible patients with breast cancer with TIVADs at the Fourth Affiliated Hospital of Hebei Medical University from 1 January 2019 to 31 August 2021 were analysed. Thrombotic occlusion was confirmed by angiography with signs of partial or total occlusion. Thrombotic occlusion occurred in 96 (6.1%) cases. Multivariable logistic regression analysis showed that the insertion site of the catheter (P = 0.004), size of the catheter (P < 0.001), and indwelling time (P < 0.001) were significant factors for thrombotic occlusion. Insertion in the right internal jugular vein, smaller catheter size and shorter indwelling time can lower the incidence of thrombotic occlusion in breast cancer patients with TIVADs in the off-treatment period