damage development
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Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 91
Author(s):  
Martin Markert ◽  
Josef Katzmann ◽  
Veit Birtel ◽  
Harald Garrecht ◽  
Holger Steeb

High-performance concrete (HPC) is a topic of current research and construction projects, due to its outstanding compressive strength and durability. In particular, its behaviour under high-cycle fatigue loading is the focus of current investigations, to further pave the way to highly challenging long-lasting constructions; e.g., bridges or offshore buildings. In order to investigate the behaviour of HPC with different moisture contents in more detail, a mixture of silica sand and basalt aggregate with a maximum grain size of 8 mm was investigated with three different moisture contents. For this purpose, cyclic compressive fatigue tests at a loading frequency of 10 Hz and different maximum stress levels were performed. The main focus was the moisture influence on the number of cycles to failure and the development of concrete temperature and strain. In a further step, only the mortar matrix was investigated. For this purpose, the mixture was produced without basalt, and the moisture influence was investigated on smaller-sized test specimens using dynamic mechanical analysis (DMA) and X-ray computed tomography (XRCT). It was shown that the moisture content of HPC had a significant influence on the fatigue damage behaviour due to the number of cycles to failure decreasing significantly with increased moisture. In addition, there was also an influence on the temperature development, as well as on the strain development. It was shown that increasing moisture content was associated with an increase in strain development. XRCT scans, in the course of the damage phases, showed an increase in internal cracks, and made their size visible. With the help of DMA as a new research method in the field of concrete research, we were also able to measure damage development related to a decrease in sample stiffness. Both methods, XRCT and DMA, can be listed as nondestructive methods, and thus can complement the known destructive test methods, such as light microscopy.


Author(s):  
L. Yu. Ilchenko ◽  
I. G. Fedorov ◽  
G. G. Totolyan ◽  
A. M. Karelina ◽  
G. A. Sedova ◽  
...  

The article presents clinical case of the jaundice development and severe hyperenzymemia in GAM-Covid-VAK (Sputnik V) vaccination against COVID-19 in a 69-year-old patient. History — systematic use of non-steroidal anti-inflammatory drugs due to persisting pain after knee arthroplasty in 2018; frequent trips for several years to another region for sanatorium treatment, the use of mineral water. The diseases caused by hepatitis viruses, drug damage and post-vaccination reaction were included in diagnostic search. The markers of hepatitis B and C infection viruses were not detected during the enzyme immunoassay and polymerase chain reaction. The indicator for determining the relationship of a drug with the liver damage development was 6 points (borderline value) and only indicated the likelihood of drug hepatotoxicity. At the same time, it is known from history that repeated administration of the drug did not cause liver dysfunctions. The diagnosis of coronavirus infection was established based on the identification of SARS-CoV-2 in the hospital with repeated laboratory testing and competing diagnosis of hepatitis A has been confirmed on the basis of hepatocellular damage and the presence of serological marker of hepatitis A virus (immunoglobulin M antibodies). The treatment was continued in the infectious hospital, where the diagnosis of co-infection was confirmed. The pneumofibrotic changes in the S5 region of the left lung were revealed according to computed tomography. The normalization of aminotransferase activity and bilirubin was noted during dynamic observation. Apparently HAV infection led to a decrease in the immune response, the formation of an insufficient level of neutralizing antibodies in vaccinated against COVID-19 patient M. and contributed to the development of a new coronavirus infection with minimal manifestations in contact with SARS-CoV-2.


Author(s):  
Harish Ramesh Babu ◽  
Marco Böcker ◽  
Mario Raddatz ◽  
Sebastian Henkel ◽  
Horst Biermann ◽  
...  

Abstract Gas turbines and aircraft engines are dominated by cyclic operating modes with fatigue-related loads. This may result in the acceleration of damage development on the components. Critical components of turbine blades and discs are exposed to cyclic thermal and mechanical multi-axial fatigue. In the current work, planar-biaxial Low-Cycle-Fatigue tests are conducted using cruciform specimens at different test temperatures. The influence on the deformation and lifetime behaviour of the nickel-base disk alloy IN718 is investigated at selected cyclic proportional loading cases. The calculation of the stress and strain distribution of the cruciform specimens from the experimental data is difficult to obtain due to complex geometry and temperature gradients. Therefore, there is a need for Finite Element Simulations. A viscoplastic material model is considered to simulate the material behaviour subjected to uniaxial and the selected planar-biaxial loading conditions. At first, uniaxial simulation results are compared with the uniaxial experiment results for both batches of IN718. Then, the same material parameters are used for simulating the biaxial loading cases. The prediction of FE simulation results is in good agreement with the experimental LCF test for proportional loadings. The equivalent stress amplitude results of the biaxial simulation are compared with the uniaxial results. Furthermore, the lifetime is calculated from the simulation and by using Crossland and Sines multi-axial stress-based approaches. The Crossland model predicts fatigue life significantly better than the Sines model. Finally, the simulated lifetime results are compared with the experimental lifetime


2021 ◽  
Vol 2131 (2) ◽  
pp. 022029
Author(s):  
Yu P Manshin ◽  
E Yu Manshina

Abstract Sufficient safety of the parts, which determines the safety of the system specified by the technical assignment, is the necessary quality of the project, the subject of the design engineer’s attention and the customer’s requirement. An extensive task is the collection of data for iterative refinement of the resource for project details in a probabilistic aspect. It can be significantly reduced when using approximate methods for estimating the resource at intermediate stages of refining the project to the required resource with a calculated probability of failure-free operation. Thus, by the analysis of dimensionless relations of parameters of models of fatigue damage development, it is possible to obtain tools of numerical estimation of technological and constructive techniques of increase of a resource of details and their rational combination. The paper deals with the numerical measures of various directions of upgrading the fatigue life of the parts, derived from the dimensionless relations of the parameters of fatigue damage development models.


2021 ◽  
Vol 87 (11) ◽  
pp. 43-54
Author(s):  
M. V. Zernin ◽  
A. V. Matyuhin ◽  
N. N. Rybkin

Fatigue damage to babbitt layers of plain bearings is often manifested during operation. The goal of the study is to develop a model for accumulation of the fatigue damage and destruction of antifriction materials and layers of plain bearings. A generalized fatigue diagram of tin-based babbitts including the main stages of fatigue damage and a diagram of the fatigue damage development in the antifriction layer of plain bearings are presented. The generalized model of V. V. Bolotin for damage accumulation and destruction is modified with regard to antifriction materials containing rather large structural elements. An explicit (direct) modeling of damage processes appeared possible for such materials. The model describes dissipated accumulation of microcracks (interpreted as destruction of the elements of the material structure), initiation and development of a system of short cracks, initiation and development of macro-cracks up to the limit state of the object. The model suggests discretization of the volume into sections with constant levels of complex stress state and discretization of the time axis into the intervals (blocks of loading cycles). The problem of identifying the parameters of a multistage model of the fatigue damage accumulation in the alloy is solved proceeding from the analysis of the results of testing babbitt specimens. We used the simplest optimization procedure, i.e., the method of deformable polyhedron. The parameters of the power function in the dependence of the rate of microdamage accumulation on the level of stresses are obtained. The parameters of the initiation and development of the crack system in the babbitt layer are obtained from the analysis of experimental results of studying steel-babbitt samples. The problem of calculating the durability of antifriction babbitt layers required the development of a new software. The program is examined by comparing calculated and experimental values of the durability of fatigue-tested bearing specimens forced against a rotating shaft by varying cyclic load. The calculated values of the durability match the experimental which confirms the performance of the calculated model.


2021 ◽  
Vol 1 ◽  
pp. 3-4
Author(s):  
Tania Barretto ◽  
Eric Rentschler ◽  
Sascha Gentes

Abstract. Due to the delayed construction and commissioning of a German repository for intermediate- and low-level radioactive waste, waste inventories from several decades are now located at the interim storage sites, the safe custody of which must also be ensured for an indefinite period of interim storage. The usual practice in the interim storage facilities is recurrent inspections, which are carried out almost exclusively manually and without electronic comparative recordings as well as without mechanical documentation and archiving. Remote or automated inspection does not take place. The inspections are carried out visually and are therefore very subjective and thus subject to errors. Manual performance is labor intensive and requires the use of personnel exposed to radiation. Neither are uniform inspection criteria of the visual inspections applied, nor are the inspections performed uniformly between sites. Based on these facts, the Institute for Technology and Management in Construction, Department of Deconstruction and Decommissioning of Conventional and Nuclear Buildings, together with the Institute for Photogrammetry and Remote Sensing, is developing an automated drum inspection system as part of the funding measure FORKA – Research for the Deconstruction of Nuclear Facilities. EMOS is a mobile inspection unit that remotely and automatically records the entire surface of the drum, including lid and bottom, optically; evaluates it analytically; and both stores it electronically and outputs the results in the form of an inspection report. In this way, recurring inspections of the drum stock can be completed under the same inspection conditions each time. A decisive advantage is the possibility of carrying out the inspection remotely in order to reduce the radiation dose to the employees on site. The optical evaluation, display and output of the results will ensure a more precise inspection and analysis of the drum surfaces through software to be specially developed than is possible through manual and visual inspections as currently performed in the interim storage facilities. The continuous monitoring of the stored drums will be facilitated and also the tracing of possible damage development through the comparison of archived measurement results is a novel and powerful tool that helps to increase and ensure the safety aspects of interim storage in the long term. Changes in drum geometry as well as in the surface condition (e.g. corrosion formation, etc.) can be identified at an early stage with the help of the inspection unit, and measures can be taken at an early stage to counteract the loss of integrity of the storage containers.


2021 ◽  
pp. 002199832110558
Author(s):  
Matthew D Waller ◽  
Charles E Bakis ◽  
Kevin L Koudela

Pitch-based carbon fiber reinforced epoxy composites are used in specialized applications for their high-modulus and thermal conductivity; however, little data on their fatigue performance are available in the open literature. In this study, fatigue behaviors of ultra-high-modulus pitch-based carbon fiber and standard-modulus polyacrylonitrile (PAN)-based carbon fiber were compared in woven quasi-isotropic epoxy matrix composites subject to uniaxial tension. It was found that the pitch fiber composite possessed higher normalized tensile fatigue strength and that its stress-life ( S-N) curve is less steep. Extrapolation suggests the pitch fiber composite is more fatigue-resistant in higher cycle regimes (specifically, N > 107). Cyclic loading of the pitch fiber composite resulted in minimal matrix damage, and the eventual fractures were localized and fiber-dominated for all stress levels. Cyclic loading of the PAN fiber composites resulted in widespread matrix cracking and delamination. The difference in fatigue behavior is attributed to the different strain levels attained at similar stress levels and the consequent difference in matrix damage development.


Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6365
Author(s):  
Chander Prakash ◽  
Vidyapati Kumar ◽  
Ankita Mistri ◽  
Amrinder Singh Uppal ◽  
Atul Babbar ◽  
...  

Fiber-reinforced polymer (FRP) matrix materials are quickly being investigated for application in concrete construction repair, reinforcement, and refurbishment. The technology has progressed to the point that its future acceptance is mainly reliant on the availability of established design guidelines based on recognized performance criteria, as well as the cost competitiveness of these technologies in contrast to conventional rehabilitation methods. The goal of this study is to evaluate the different functional grades of adhesives throughout bond length for bonded socket joints of laminated FRP composite pipes. Damage development resistance is high with a functionally graded FRP composite socket joint, as shown. To extend the service life of the structure, the joint designer should use an FRP composite socket joint with a functionally graded adhesive (FGA).


2021 ◽  
Vol 67 (5) ◽  
pp. 91-98
Author(s):  
Mayu FUJIMOTO ◽  
Kazutaka MUKOYAMA ◽  
Xingsheng LI ◽  
Koushu HANAKI ◽  
Tetsusei KURASHIKI

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