Thickness Improvement and Calibration Pressure Reduction of Stepped Tubular Components Using Axial Hydro-pressing Method

A new tube axial hydro-pressing method was proposed to solve the problems of high forming pressure and severely uneven wall thickness distribution of traditional tube hydroforming methods to form stepped tubular components. The forming pressure of the traditional hydroforming and the tube axial hydro-pressing method is studied theoretically, the mechanical model of the fillet area is established, and the forming pressure calculation formula is given. Based on this, an investigation of the tube axial hydro-pressing method is carried out by numerical simulation and experimental methods, and compared with the traditional tube hydroforming method. The key to the tube axial hydro-pressing method is to precisely control the relationship between the protrusion height and the axial feed, which is achieved by precisely controlling the feeding pressure and the axial displacement. Therefore, the constant pressure device in the experiment was used to eliminate the influence of the pressure rise caused by the volume compression on its cooperation relationship, to achieve accurate control of the loading path, eliminate wrinkles and flash defects. A qualified workpiece is successfully manufactured when the internal pressure is 18.0 MPa and the feed on each side is 15.0 mm. The forming pressure is reduced by 88.0%, and the feed is increased by 6.5%, which reduces the wall thickness reduction by 9.0%. The wall thickness difference of the workpiece can be controlled within 7.0%. The tube axial hydro-pressing method is suitable for forming stepped tubular components, which can achieve more replenishment at lower pressures, thereby effectively improving the uniformity of wall thickness and significantly reducing the forming pressure.

Multi-objective Tubular Hydroforming Process Parametric Optimization using TOPSIS and PSI techniques

Tube Hydroforming (THF) process is widely used in the aerospace and automotive industries. The success of forming tubular components using the THF process generally depends on many influencing parameters such as geometry, coefficient of friction, loading pathways, material formability, etc. The objective of this study was to determine the effect of the corner radius, coefficient of friction and heat treatment temperature on the bulging of the tubular component using finite element simulations. To address the complexity of parameter selection correctly with different alternatives, the multi-criteria decision-making methods (MCDM) applied in the present work. Two decision models, namely Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) and Performance Selection Index (PSI) methods with entropy weighting criteria were applied for obtaining the best combination of parameters to get a sound quality product. Finally, the proposed ranking was validated by conducting experimental trials and the error was observed to be in limits in comparison with the simulated data. ANOVA was also performed to distinguish the significant parameters and their contribution to the responses. Both the MCDM methods suggested the same favorable and unfavorable alternatives.

Three-dimensional numerical analysis of tubular adhesive joints under torsional loads

Bonding method using adhesives has gained a lot of presence in the design of mechanical structures in several industries, especially in the aeronautics and automobile industry. Bonded joints are widely used to join tubular components, in vehicle frames like aeroplanes and automobiles. For the design process of these joints, analytical or numerical predictive techniques can be used. This work performs a numerical study in order to evaluate the torsional performance of aluminium tubular adhesive joints (AW6082-T651), considering the variation of the main geometric parameters, such as overlap length (L O) and tubes’ thickness. In order to predict the strength, the Finite Element Method (FEM) was used with Cohesive Zone Models (CZM), whose analysis based itself on the internal stresses of the adhesive, namely the analysis of shear stress (τxy) and joint strength, measured by the maximum torsional moment (M m). Previously, validation with experimental data was carried out. The technique was positively validated, and a significant geometry on M m was found, except for L O.

A Regression Model to Determine Pressure Ratings of Slotted Tubular Components With Imperfections

The objective of the present work is to develop a prediction model to predict the pressure rating accounting for the imperfections using Design of Experiments (DoE) approach. Each imperfection is modelled in terms of a design parameter and bounded by a certain realistic variation. The DoE approach aids in identifying the most influencing imperfections and in further developing an approximate model that relates the input design parameters to the maximum radial deformation. Furthermore, the regression model is built to obtain the pressure rating of the component accounting for the imperfections. The study identifies that ovality and its orientation are by far the most influential imperfections when compared to others and provides the designer the effects of imperfection parameters on the component. The prediction model developed, serves as a ready reckoner to obtain the pressure rating of the component within the design space without any exclusive analysis. This approach leads to effective design and saves computational time.

Combination of Nivolumab Plus Ipilimumab for Mucinous Tubular and Spindle Cell Carcinoma of the Kidney with Bone Metastases: The First Case Report

Background: Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare subtype of renal cell carcinoma (RCC) and generally considered a low-grade renal epithelial neoplasm composed of tubules, spindle cells, and extracellular mucin. MTSCC with distant metastases has been reported, with some cases showing a poor prognosis. While only a few case reports regarding the treatment of metastatic MTSCC have been reported, targeted agents and monotherapy of immune checkpoint inhibitors have shown some efficacy. To our knowledge, this is the first reported case of metastatic MTSCC of the kidney treated with combination therapy of nivolumab plus ipilimumab.Case presentation: A 26-year-old man consulted our hospital after a 72-mm tumor was detected at the upper pole of the left kidney with multiple osteolytic bone metastases by computed tomography (CT). A CT-guided biopsy of the renal tumor and bone metastases resulted in a diagnosis of MTSCC of the kidney with bone metastases (cT2aN0M1) and an ‘intermediate risk’ according to the International Metastatic Renal Cell Carcinoma Database Consortium criteria. He therefore received combination therapy of nivolumab plus ipilimumab therapy. After 4 cycles of combination nivolumab plus ipilimumab and 9 cycles of nivolumab monotherapy, he underwent cytoreductive nephrectomy because the tumor had shrunk, and sclerotic changes in the bone metastases were noted. In the excised specimen, the programmed cell death ligand 1 expression was higher in the spindle components than in the tubular components, but CD4- and CD8-positve T cells showed greater infiltration in the tubular components than in the spindle components. Furthermore, CD-4- and CD-8-positive T cells in both components of the resected specimen showed greater infiltration than they had at the pretreatment biopsy of the renal tumor and bone metastases.Conclusions: Combination immunotherapy of nivolumab and ipilimumab may be an effective treatment option for metastatic MTSCC of the kidney.

Renal MRI Diffusion: Experimental Protocol

Renal diffusion-weighted imaging (DWI) can be used to obtain information on the microstructure of kidney tissue, and has the potential to provide MR-biomarkers for functional renal imaging. Here we describe in a step-by-step experimental protocol the MRI method for measuring renal diffusion coefficients in rodents using ADC or IVIM models. Both methods provide quantification of renal diffusion coefficients; however, IVIM, a more complex model, allows for the calculation of the pseudodiffusion and fraction introduced by tissue vascular and tubular components. DWI provides information of renal microstructure contributing to the understanding of the physiology and the underlying processes that precede the beginning of pathologies.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.

Enhancing the Energy Absorption Characteristics of Multi-Cell Square Tubes under Lateral Impact

Thin-walled tubular components have been broadly utilized in energy absorption applications, to improve the crashworthiness of the structure and to mitigate the impact kinetic energy through progressive plastic buckling. The extensive usage of cylindrical tubes as impact energy attenuators is owing to their superior crashworthiness behaviour, easy fabrication, less cost, and light-weight efficacy. The current paper examines the lateral impact behaviour of thin-walled aluminum multi-cell square tubes of different configurations using numerical simulations. These non-linear impact simulations were performed on multi-cell square tubes using finite element ABAQUS/CAE explicit code. From the overall results obtained, the crashworthiness performance of multi-cell square tubes of various configurations were compared. Moreover, multi-cell square tube of first type were recognized as most prominent for better energy absorption. This type of tubes was found to be effective one to improve the lateral crashworthiness performance