Automatically Welded Tubular X‐Joints for Jacket Substructures: Prediction of the Technical Fatigue Crack Location

To increase the competitiveness of jacket substructures compared to monopiles a changeover from an individual towards a serial jacket production based on automated manufactured tubular joints combined with standardized pipes has to be achieved. Therefore, this paper addresses fatigue tests of automatically welded tubular X-joints focusing on the location of the technical fatigue crack. The detected location of the technical crack is compared to numerical investigations predicting the most fatigue prone notch considering the structural stress approach as well as the notch stress approach. Besides, the welding process of the automated manufactured tubular X-joints is presented

Fatigue Behavior of Automatically Welded Tubular Joints for Offshore Wind Energy Substructures

To successfully fight climate change, it is essential to replace fossil fuels with renewable energies. Offshore wind energy will significantly contribute to this transition. Since the required future bottom-fixed offshore wind farms will be located further away from shore and in greater water depth, in addition to (XL-) monopiles, jacket foundations are a reasonable alternative. To increase the competitiveness of jacket substructures, a modular jacket concept was developed within the offshore industry, combining prefabricated robot-welded tubular joints with standardized pipes. With regard to fatigue strength in particular, the automatically welded tubular joints have a large potential due to the reproducible fabrication process resulting in highly uniform welds. However, this potential cannot be adequately considered for the fatigue assessment due to the lack of suitable S-N curves. Up to now, serial fatigue tests to determine statistically validated S-N curves have only been conducted on manually welded tubular joints. Nevertheless, some robot-welded tubular joints were tested regarding fatigue strength, but neither the influence of an inner root welding nor the existing weld geometry was systematically evaluated. Against this background, the fatigue resistance of automatically manufactured tubular joints is determined within this thesis. Furthermore, this work focuses on the characterization of the uniform weld seam geometry as a prerequisite for an additionally proposed weld geometry optimization using bionic approaches. To determine a statistically validated S-N curve, serial fatigue tests were performed on 16 single- and 16 double-sided automatically welded tubular X-joints, whereby these joints were medium-scaled compared to real jacket dimensions. During these tests, the fatigue damage evolution was digitized using the digital image correlation method, enabling a detailed analysis of the tubular joints' fatigue behavior including crack initiation. The obtained fatigue resistance of the robot-welded tubular X-joints was moderately improved compared to the currently valid design S-N curve. The corresponding scatter was significantly reduced in comparison to the experience of manually welded tubular joints. In contrast, no significant impact of the inner root welding on the fatigue strength could be observed. In addition to the fatigue tests, the geometry of the robot-fabricated welds was systematically evaluated with regard to its reproducibility. The outcomes were then compared to reference values of manually welded tubular joints. For this purpose, analytical investigations were performed to determine the notch radius and flank angle distributions. Additionally, a reverse engineering application was developed to enable a real notch stress analyses of the actual weld geometry. The obtained statistics representing the distributions of the flank angles and real notch stresses confirmed the optical impression of a uniform and highly reproducible weld geometry when compared to the manually welded tubular joints. However, with respect to the minimum size of the achieved notch radii, no significant advantage of the robot-based welding could be determined. Finally, considering the statistically confirmed reproducibility of the weld geometry, a bionic optimization of the weld geometry profile was proposed, which resulted in a significant reduction of the decisive fatigue loads

Abstract 111: Head and neck cancer cells can differentiate and resemble their tissue of origin

Oppel F, Shao S, Gendreizig S, et al. Abstract 111: Head and neck cancer cells can differentiate and resemble their tissue of origin. Cancer Research. 2022;82(12_Supplement):111-111.**Abstract** Head and neck squamous cell carcinoma (HNSCC) is a highly malignant disease with a mortality rate of about 50%. It represents the sixth most common type of malignant tumor in the world. Risk factors include tobacco and alcohol usage and infection with the human papilloma virus (HPV). HPV-negative HNSCCs frequently display areas of cornification evident by keratin pearls in the tumor tissue. Cornification represents a natural differentiation path of keratinocytes in the normal epidermis and oral mucosa. To investigate the mechanisms of HNSCC cell differentiation we have established spheroid cell cultures from patient-derived HNSCC and parotid gland adenoid cystic carcinoma (ACC) tissue that grow in suspension under serum-free conditions. The use of a specific differentiation medium induced striking adhesion, loss of proliferation, and differentiation in tumor cells. Spheroid cells grew as single cell clones under serum-free conditions with a cloning efficiency of 40-60%, which was fully diminished under differentiating conditions. HNSCC cells cornified as indicated by the formation of lamellar bodies in the cytoplasm of adherent cells and an upregulation of cornification markers SPRR3 and involucrin. ACC cells upregulated parotid gland differentiation markers including α-amylase. RNA-seq analysis in HNSCC cells confirmed an upregulation of signaling pathways associated with cornification and epithelial cell differentiation. Conversely, pathways regulating the three-dimensional organization of the genome were downregulated upon differentiation. This was accompanied by the formation of ATRX-positive heterochromatin foci in the nucleus of differentiated ACC and HNSCC cells resembling those previously described to arise during therapy-induced senescence. Moreover, gas chromatography mass spectrometry analysis revealed a lack of essential amino acids including leucine to be implicated in the differentiation process. Altogether, our spheroid model of HNSCC and ACC cells is suitable to analyze the mechanisms underlying tumor cell differentiation and might lead to new therapeutic approaches that can drive long-term repopulating HNSCC and ACC cells into differentiation. Citation Format: Felix Oppel, Senyao Shao, Sarah Gendreizig, Philipp Kühnel, Vivien Przybycin, Carsten Hain, Pascal Schmidt, Matthias Schürmann, Peter Goon, Karsten Niehaus, Jörn Kalinowski, Holger Sudhoff. Head and neck cancer cells can differentiate and resemble their tissue of origin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 111

Different effects of lifestyle intervention in high- and low-risk prediabetes

Lifestyle intervention (LI) can prevent type 2 diabetes, but response to LI varies depending on risk subphenotypes. We tested if prediabetic individuals with low risk benefit from conventional LI and individuals with high risk benefit from an intensification of LI in a multi-center randomized controlled intervention over 12 months with 2 years follow up. 1105 prediabetic individuals based on ADA glucose criteria were stratified into a high- and low-risk phenotype, based on previously described thresholds of insulin secretion, insulin sensitivity and liver fat content. Low-risk individuals were randomly assigned to conventional LI according to the DPP protocol or control (1:1), high-risk individuals to conventional or intensified LI with doubling of required exercise (1:1). A total of 908 (82%) participants completed the study. In high-risk individuals, the difference between conventional and intensified LI in post-challenge glucose change was -0.29 mmol/l [CI:-0.54;-0.04], p=0.025. Liver fat (-1.34 percentage points [CI:-2.17;-0.50], p=0.002) and cardiovascular risk (-1.82[CI:-3.13-0.50],p=0.007) underwent larger reductions with intensified than with conventional LI. During a follow up of 3 years, intensified compared to conventional LI had a higher probability to normalize glucose tolerance (p=0.008). In conclusion, it is possible in high-risk individuals with prediabetes to improve glycemic and cardiometabolic outcomes by intensification of LI. Individualized, risk-phenotype-based LI may be beneficial for the prevention of diabetes