1. In situ consideration of resistance of bridge girder according to EC2 with AEMAna Brunčič, Andrej Štrukelj, Maja Kreslin, Andrej Anžlin, Aljoša Šajna, 2023, published scientific conference contribution Abstract: The paper presents a case study of a considerably cracked and degraded bridge in Slovenia: with the implementation of in-situ measurements under bending and shear and the use of a non-destructive acoustic emission technique. Despite the existing crack system, the latter was able to detect microstructural changes. These were characterised by low values of average frequency (AF), as well as lower values of the rise time-amplitude ratio (RA), and energy. A correlation between shear capacity and acoustic activity was observed. This promises to expand the use of AE in the process of assessing of the load-bearing capacity of existing concrete structures.
Keywords: shear resistance, shear crack, crack width, acoustic emission (AE) parameters, bridge girder, stiffness, elasticity, damage evaluation
Published in DiRROS: 28.11.2023; Views: 192; Downloads: 104
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2. Effect of surface machining on the environmentally-assisted cracking of Alloy 182 and 316L stainless steel in light water reactor environments : results of the collaborative project MEACTOSMariia Zimina, Stefan Ritter, Bojan Zajec, Marc Vankeerberghen, Liberato Volpe, Anna Hojna, Rik-Wouter Bosch, Fabio Scenini, Zaiqing Que, Alberto Sáez-Maderuelo, P. Jill Meadows, Michael Grimm, Matthias Herbst, Andraž Legat, Agostino Maurotto, Radek Novotny, Karl-Heinz Seifert, 2023, original scientific article Abstract: The main objective of the EU-funded project mitigating environmentally-assisted cracking through optimisation of surface condition (MEACTOS) was to gain knowledge on the ability of different surface machining procedures to mitigate environmentally-assisted cracking (EAC) in typical light water reactor structural materials and environments. Surfaces of cold-worked (CW) type 316L austenitic stainless steel and nickel-based weld metal Alloy 182 flat tapered tensile specimens were machined using different processes. EAC initiation susceptibility of these specimens was evaluated using constant extension rate tensile (CERT) tests under simulated boiling water reactor (BWR) and pressurized water reactor (PWR) conditions and assessed using constant load experiments. More than a hundred tests were performed covering about 10 years of autoclave testing time. Only minor or no measurable improvements in EAC initiation susceptibility as a function of surface treatments (grinding or advanced machining) compared to the standard industrial face milling were demonstrated. In most cases, the stress thresholds for EAC initiation determined in constant load tests confirmed the trend obtained from CERT tests. This paper summarises the most important results and conclusions concerning the EAC initiation behaviour for the CW 316L and Alloy 182 under reducing PWR and oxidizing BWR conditions.
Keywords: crack initiation, environmentally-assisted cracking, Alloy 182, AISI 304 stainless steel, surface treatment, light water reactor, open access
Published in DiRROS: 30.05.2023; Views: 315; Downloads: 182
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3. Investigation of surface treatment effects on the environmentally-assisted cracking behaviour of Alloy 182 in boiling water reactor environmentZaiqing Que, Bojan Zajec, Stefan Ritter, Tommi Seppänen, Timo Saario, Aki Toivonen, Aleksandra Treichel, Valentin Lautaru, Fabio Scenini, 2022, original scientific article Abstract: Surface treatments of primary circuit components in light water reactors are regarded as possible ways to mitigate environmentally-assisted cracking (EAC). To date, it is not fully conclusive which surface condition is suitable to reduce the EAC initiation susceptibility. Constant extension rate tensile (CERT) tests were performed by several labs using flat tapered tensile specimens with different surface conditions (ground, industrial face milled, advanced face milled and shot peened), exposed to a boiling water reactor normal water chemistry environment at 288°C. Despite some scatter in the results, the CERT tests revealed that the EAC initiation susceptibility seems lowest for the advanced face milled surface and highest for the shot peened surface. However, it must be emphasised that the differences were moderate and that the surprising behaviour of the shot peened surface can be explained. The mechanical grinding of the surface did not significantly retard EAC initiation compared to industrial face milling.
Keywords: crack initiation, environmentally-assisted cracking, Alloy 182, surface machining, boiling water reactor, open access
Published in DiRROS: 05.05.2023; Views: 347; Downloads: 145
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4. Mode I fracture of beech-adhesive bondline at three different temperaturesJaka Gašper Pečnik, Andreja Pondelak, Michael David Burnard, Václav Sebera, 2022, original scientific article Abstract: Single edge-notched three-point bending tests (SEN-TPB) for mode I were utilized to experimentallyevaluate fracture properties of adhesive bondlines in European beech (Fagus SylvaticaL.). Thebondline was examined at two anatomical planes with TR and RT orientation and at control andtwo elevated temperatures (70°C and 140°C). Among epoxy (EPI), melamine-urea formaldehyde (MUF), and polyurethane (PUR) adhesives, the highest average critical energyGcwith 0.80 N/mmand fracture energyGfwith 1079.4 N/mm were obtained for EPI in the TR plane and understandard climate conditions (20°C/65% relative humidity), followed by MUF (Gc= 0.50 N/mm andGf= 620 N/mm) and PUR (Gc= 0.25 N/mm andGf= 290.9 N/mm), respectively. PUR was leasteffected by elevated temperature, and no significant differences forGcandGfbetween TR and RTbondline orientations were found for MUF and PUR treated at 20°C/65% relative humidity whilecomparisons between other factors varied significantly. Treatment of specimens at elevatedtemperatures resulted in reduced fracture performance regardless of wood grain orientation orthe adhesive system.
Keywords: crack, fracture, grain orientation, temperature, European Beech, odprti dostop
Published in DiRROS: 03.05.2023; Views: 427; Downloads: 351
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