Boundaries for increasing the fatigue limit of the bearing steel SAE 52100 by thermomechanical treatments

AbstractHigh end applications often require high strength materials especially regarding the fatigue limit. It is still an open question what the highest fatigue limits are and how to increase them further in high strength steels. A thermomechanical treatment (TMT) in the temperature range of maximal dynamic strain ageing is an auspicious way to increase the fatigue limit of bearing steel SAE52100. Successful attempts have been published for various materials states. The present investigation deals with the influence of non-metallic inclusions on the fatigue limit and the possibility to increase the fatigue limit by TMT. The fatigue limit of high strength steels increases by reducing the size of the non-metallic inclusions during steelmaking. We found that TMT increases the fatigue limit of a high strength materials state only in cases in which the non-metallic inclusions are the starting points of the fatigue cracks. In the case of high cleanliness of the steel the origin of the fatigue cracks may be at any position in the matrix. If there are no critical non-metallic inclusions a TMT did not increase the fatigue limit further. The reasons for this behaviour will be explained and the border of the fatigue limit of high strength steels will be discussed

Nachhaltigkeit als strategischer Imperativ für die Gesellschaft und Unternehmen

Was haben „Fridays for future“ und Corona gemeinsam? Die Jugend fordert und die Pandemie erfordert einen nachhaltigen Umgang mit unseren Ressourcen, letztendlich zur Sicherung unseres Überlebens. Klimawandel, Verschmutzung, Reduzierung der Biodiversität, Ressourcenknappheit, Bevölkerungswachstum, Armut, Hunger, soziale Ungleichheiten, ungerechte Bildungschancen und Migration sind gewichtige Herausforderungen. Und es zeigt sich weltweit ein neues „globales“ Bewusstsein für Nachhaltigkeit. Fridays for Future Protestbewegungen sind ein deutlich sichtbares Zeichen dafür. Und internationale Vereinbarung wie die UN Sustainable Development Goals (SDGs) oder das Pariser Klimaschutzabkommen sind ebenso ermutigende Zeichen für ein neues (kollektives) Bewusstsein. Mit diesem kollektiven Bewusstsein verändern sich die Anforderungen an Unternehmen und deren Produckte und Services. Für Unternehmen wird Nachhaltigkeit zu einem strategischen Imperativ, der auf allen Ebenen des Geschäftsmodells verankert werden muss. Ein wichtiges Kennzeichen ist dabei die Zusammenarbeit der verschiedenen Stakeholder entlang der gesamten Wertschöpfungskette. Denn Nachhaltigkeit kann keine Gesellschaft und kein Unternehmen für sich allein lösen

Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases

Safety assessment of the substance (butadiene, styrene, methyl methacrylate, butyl acrylate) copolymer cross-linked with divinylbenzene or 1,3-butanediol dimethacrylate for use in food contact materials

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Results of a randomized trial of treatment modalities in patients with low or early-intermediate risk prostate cancer (PREFERE trial)

Purpose The optimal treatment for patients with low to early-intermediate risk prostate cancer (PCa) remains to be defned. The randomized PREFERE trial (DRKS00004405) aimed to assess noninferiority of active surveillance (AS), externalbeam radiotherapy (EBRT), or brachytherapy by permanent seed implantation (PSI) vs. radical prostatectomy (RP) for these patients. Methods PREFERE was planned to enroll 7600 patients. The primary endpoint was disease specifc survival. Patients with PCa stage≤cT2a, cN0/X, M0, PSA ≤10 ng/ml and Gleason-Score≤3+4 at reference pathology were eligible. Patients were allowed to exclude one or two of the four modalities, which yielded eleven combinations for randomization. Sixty-nine German study centers were engaged in PREFERE. Results Of 2251 patients prescreened between 2012 and 2016, 459 agreed to participate in PREFERE. Due to this poor accrual, the trial was stopped. In 345 patients reference pathology confrmed inclusion criteria. Sixty-nine men were assigned to RP, 53 to EBRT, 93 to PSI, and 130 to AS. Forty patients changed treatment shortly after randomization, 21 to AS. Fortyeight AS patients with follow-up received radical treatment. Median follow-up was 19 months. Five patients died, none due to PCa; 8 had biochemical progression after radical therapy. Treatment-related acute grade 3 toxicity was reported in 3 RP patients and 2 PSI patients. Conclusions In this prematurely closed trial, we observed an unexpected high rate of termination of AS and an increased toxicity related to PSI. Patients hesitated to be randomized in a multi-arm trial. The optimal treatment of low and earlyintermediate risk PCa remains unclear

Safety assessment of the process ‘EREMA Recycling (MPR, Basic and Advanced technologies)’, used to recycle post-consumer PET into food contact materials

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Safety assessment of the mixture of methyl-branched and linear C14–C18 alkanamides, derived from fatty acids, for use in food contact materials

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