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  • 1
    Electronic Resource
    Electronic Resource
    FATIGUE CRACK GROWTH OF Al 2024-T3 UNDER LOW AMPLITUDE TWO-STEP LOADING (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 15 (1992), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The significance of interaction effects has been studied in tests with a continuous repetition of blocks with low and high amplitude cycles under conditions characteristic for ultrasound fatigue. Significant retardation effects were observed. However, low-intensity cycles, which according to a previous investigation might be harmless, did contribute to crack growth. Delayed retardation explains this observation. A fractographic analysis indicated the significance of surface roughness. Low-amplitude cycles may induce a smoother fracture surface, and thus increase the crack growth rate at higher amplitudes. Accurate predictions are therefore problematic. For similar reasons, omitting numerous low-amplitude cycles in random load experiments should be done with great care.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1992.tb01269.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    INFLUENCE OF TRANSFORMATION-INDUCED CRACK CLOSURE ON SLOW FATIGUE CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fatigue crack growth under constant and random loading conditions was investigated for a metastable austenitic-bainitic steel in comparison with a ferritic chromium steel at very low crack growth rates. Experimentally determined random crack growth was compared with linear Miner calculations on the basis of constant amplitude results. It was found that the measured crack growth rates in transforming material are a factor of 10 lower than the calculated values, whereas the difference is only a factor of 2 for the ferritic steel. The reason for the pronounced crack growth retardation in the metastable alloy is transformation of part of the austenitic phase into martensite in the stress field of the crack tip, accompanied by a volume increase and, consequently, residual compressive stresses. Rare high load cycles in the random sequence increase the closure level, which then leads to pronounced retardation of fatigue crack growth for the numerous successive low amplitude cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1995.tb00918.x
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  • 3
    Electronic Resource
    Electronic Resource
    CRACK FACE INTERACTIONS AND NEAR-THRESHOLD FATIGUE CRACK GROWTH (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 16 (1993), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Rough fracture surfaces usually influence substantially the fatigue growth properties of materials in the regime of low growth rates. Friction, abrasion, interlocking of fracture surface asperites and fretting debris reduce the applied load amplitude to a smaller effective value at the crack tip (“sliding crack closure”, or “crack surface interaction” or “crack surface interference”). The influence of these phenomena on the fatigue crack growth properties of structural steel is discussed and compared for the two kinds of mixed mode loading employed in this work. Mixed mode loading was performed by (A): cyclic mode III + superimposed static mode I and (B): cyclic mode I + superimposed static mode III loading. Such loading cases frequently occur in rotating load-transmission devices.Several differences are typical for these two mixed-mode loading cases. A superimposed static mode I load increases the crack propagation rate under cyclic mode III loading whereas cyclic mode I fatigue crack propagation is retarded when a static mode III load is superimposed. Increase of the R -ratio (of the cyclic mode III load) leads to an insignificant increase of fracture surface interaction and subsequently to a small decrease of the crack growth rate for cyclic mode III loading, whereas higher R -values during cyclic mode I+ superimposed static mode III loading lead to a significant reduction of the crack growth rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1993.tb00071.x
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  • 4
    Electronic Resource
    Electronic Resource
    NEAR-THRESHOLD FATIGUE CRACK GROWTH IN A12O3 PARTICLE REINFORCED 6061 ALUMINIUM ALLOY (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The influence of Al2O3 particle reinforcement on the fatigue crack growth properties of 6061-T6 aluminium alloy in the near threshold regime has been investigated at a load ratio of R=– 1 using an alloy with 15 vol.% fine particles (6061/Al2O3/15p) and one with 21 vol.% coarser particles (6061/Al2O3/21p). The Al2O3 particles act as obstacles for fatigue crack growth and are especially effective at very low cyclic loads. For the reinforced alloy with fine particles the threshold of the stress intensity amplitude is higher than that for the alloy containing coarse particles, and the lowest threshold value of Kmax was obtained for pure 6061-T6. Fracture of ceramic particles and interfaces between matrix and Al2O3 particles, both more frequent for coarser particles, may serve as an explanation for the more effective improvement of fatigue crack growth properties by fine particles. At maximum stress intensity factors above 6.5 MPa√m, fatigue crack growth in the particle reinforced alloys is faster than in the unreinforced alloy 6061-T6, which is attributed to more frequent particle and interface fracturing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1995.tb01190.x
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  • 5
    Electronic Resource
    Electronic Resource
    Das primäre Carcinom der extrahepatischen Gallenwege (1979)
    Springer
    Langenbeck's archives of surgery 350 (1979), S. 33-42 
    Details
    ISSN: 1435-2451
    Keywords: Carcinoma of biliary tract ; Sex incidence ; Bilio-digestive anastomosis ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In den letzten Jahrzehnten ist es zu keiner wesentlichen Verbesserung der mittleren Überlebenszeit der primären Carcinome der extrahepatischen Gallenwege trotz Verbesserung der Operationstechnik gekommen, weil die von einem Gallenblasen- bzw. von einem Gallengangskrebs befallenen Patienten wegen der uncharakteristischen Symptome erst dann einer gezielten Diagnostik zugeführt werden, wenn das Carcinom bereits die Organgrenzen überschritten oder metastasiert hat. Bei etwa 2/3 der Patienten mit Gallenblasen- und Gallengangscarcinomen war das Tumorleiden nicht mehr operabel. Die 5-Jahres-Überlebensrate beim Gallenblasencarcinom beträgt 7 %. Lediglich 1 Patient mit einem Gallengangscarcinom überlebte bisher länger als 5 Jahre. Da eine Beziehung zwischen Gallenblasensteinleiden und/ oder chronischen Entzündungen der Gallenblase und Gallenwege und Carcinomentstehung nicht von der Hand gewiesen werden kann, sollte man die Indikation zur ≫prophylaktischen≪ Cholecystektomie und Gallenwegssanierung großzügig stellen.
    Notes: Summary From 1957 –1 977 193 patients were treated at the surgical clinic of the University of Tübingen for carcinoma of the extrahepatic bile ducts. Gall bladder carcinoma made up 139 cases; 54 were of bile duct carcinoma. The tumors were no longer operable in two-thirds of the patients with extrahepatic bile ducts cancer. The life expectancy rate of five years for patients with gall bladder carcinoma held for 7 %. Up to now only one patient with a bile duct malignancy has survived longer than five years. In the last decade essentially no improvement of median life expectancy has occurred despite improved operating techniques. Due to uncharacteristic, misleading upper abdominal symptoms, patients who suffer gall bladder or bile duct cancer are unfortunately accurately diagnosed only after the carcinoma has overcome organ borders or is already metastatic. There is reasonable hope for improved early prognosis of extrahepatic bile duct carcinoma with ERCP (Endoscopic Retrograde Cholangio-Pancreaticography) and computer-tomography. Because the possibility of a relationship between gall bladder stones and/or the chronic inflammation of gall bladder and bile ducts and the development of cancer is not out of the question, widespread prophylactic cholecystectomy and gall passage cleansing should be employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01232093
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  • 6
    Electronic Resource
    Electronic Resource
    134. Die Bedeutung der Computertomographie beim stumpfen Bauch- und Thoraxtrauma (1982)
    Springer
    Langenbeck's archives of surgery 358 (1982), S. 477-477 
    Details
    ISSN: 1435-2451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01271880
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  • 7
    Electronic Resource
    Electronic Resource
    149. Zur Pathogenese der Wunddehiscenzen nach Laparotomien (1982)
    Springer
    Langenbeck's archives of surgery 358 (1982), S. 483-483 
    Details
    ISSN: 1435-2451
    Keywords: Wound dehiscence ; General causes ; Mechanical causes ; Local causes ; Wunddehiscenz ; allgemeine Faktoren ; mechanische Komponenten ; lokale Ursachen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 10 714 Laparotomien traten 84 Wunddehiscenzen auf; das entspricht einer Häufigkeit von 0,8%. Die Letalität betrug 36,6%. Bei der Pathogenese einer Bauchwandruptur müssen allgemeine Faktoren (Eiweißstoffwechselstörungen, Medikamente, Hormone), mechanische Faktoren (ausgeprägte Adipositas, Erbrechen, Meteorismus, Ascites) und lokale Faktoren (fehlerhafte Nahttechnik, Nahtmaterial, Wundinfektion) berücksichtigt werden. 23,2 % der Wunddehiscenzen hatten ihre Ursache in postoperativen Peritonitiden, perforierten Appendicitiden und infizierten Wundhämatomen.
    Notes: Summary Wound dehiscence occurred in 84 (0.8 %) of 10,714 laparotomies. Lethality was 36.6 %. Abdominal wound dehiscence can result from general (disturbed protein metabolism, drugs, hormones), mechanical (excessive adiposis, vomiting, meteorism, ascites) or local causes (suture technique, suture material, wound infection). Of all cases of wound dehiscence 85 % occurred after longitudinal section. Infected wound dehiscence was caused in 23.2 % of cases by postoperative peritonitis, perforated appendicitis and infected haematoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01271895
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