scholarly journals Identifying the Range of Micro-Events Preceding the Critical Point in the Destruction Process in Traditional and Quasi-Brittle Cement Composites with the Use of a Sound Spectrum

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1809
Author(s):  
Dominik Logoń ◽  
Janusz Juraszek ◽  
Zbynek Keršner ◽  
Petr Frantík
Keyword(s):  
Critical Point ◽  
Stress Level ◽  
Compression Strength ◽  
Test Cases ◽  
Cement Composites ◽  
Test Results ◽  
Destruction Process ◽  
Four Point Bending ◽  
Sound Spectrum ◽  
Brittle Composites

This paper presents the possibilities of determining the range of stresses preceding the critical destruction process in cement composites with the use of micro-events identified by means of a sound spectrum. The presented test results refer to the earlier papers in which micro-events (destruction processes) were identified but without determining the stress level of their occurrence. This paper indicates a correlation of 2/3 of the stress level corresponding to the elastic range with the occurrence of micro-events in traditional and quasi-brittle composites. Tests were carried out on beams (with and without reinforcement) subjected to four-point bending. In summary, it is suggested that the conclusions can be extended to other test cases (e.g., compression strength), which should be confirmed by the appropriate tests. The paper also indicates a need for further research to identify micro-events. The correct recognition of micro-events is important for the safety and durability of traditional and quasi-brittle cement composites.

scholarly journals Identification of the Destruction Process in Quasi Brittle Concrete with Dispersed Fibers Based on Acoustic Emission and Sound Spectrum

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2266 ◽  
Author(s):  
Dominik Logoń
Keyword(s):  
Acoustic Emission ◽  
Three Dimensional ◽  
Sound Intensity ◽  
Destruction Process ◽  
Ordinary Concrete ◽  
Additional Information ◽  
Dimensional Spectrum ◽  
Sound Spectrum ◽  
Brittle Composites ◽  
Brittle Composite

The paper presents the identification of the destruction process in a quasi-brittle composite based on acoustic emission and the sound spectrum. The tests were conducted on a quasi-brittle composite. The sample was made from ordinary concrete with dispersed polypropylene fibers. The possibility of identifying the destruction process based on the acoustic emission and sound spectrum was confirmed and the ability to identify the destruction process was demonstrated. It was noted that in order to recognize the failure mechanisms accurately, it is necessary to first identify them separately. Three- and two-dimensional spectra were used to identify the destruction process. The three-dimensional spectrum provides additional information, enabling a better recognition of changes in the structure of the samples on the basis of the analysis of sound intensity, amplitudes, and frequencies. The paper shows the possibility of constructing quasi-brittle composites to limit the risk of catastrophic destruction processes and the possibility of identifying those processes with the use of acoustic emission at different stages of destruction.

scholarly journals The Recognition of the Micro-Events in Cement Composites and the Identification of the Destruction Process Using Acoustic Emission and Sound Spectrum

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2988 ◽  
Author(s):  
Dominik Logoń ◽  
Krzysztof Schabowicz
Keyword(s):  
Acoustic Emission ◽  
Three Dimensional ◽  
Sound Intensity ◽  
High Volume ◽  
Cement Composites ◽  
Destruction Process ◽  
Critical Crack ◽  
Additional Information ◽  
Sound Spectrum ◽  
Structure Destruction

This paper presents the recognition of micro-events and their concentration in quasi-brittle cement composites and the identification of the destruction process based on acoustic emission and sound spectrum. The tests were conducted on a quasi-brittle composite of a cement paste reinforced with a high volume of dispersed polypropylene fibers. The possibility of identifying the destruction process based on acoustic emission and sound spectrum was confirmed. This paper focused on the identification of micro-events using the 3D spectrum. It was shown that the identification of the concentration of micro-events precedes the occurrence of critical crack fcr, ending the Hooke’s law range. The ability to recognize this phenomenon with the use of the 3D spectrum makes it possible to predict the structure destruction process and subsequently to assess the structure destruction (micro and macro-cracks) and the reinforcement destruction (pull-off, breaking). It was confirmed that the three-dimensional spectrum provided additional information, enabling a better recognition of micro and macro-changes in the structure of the samples based on the analysis of sound intensity, amplitudes, and frequencies.

scholarly journals Online Affirmation and Peer Support are Effective for Reducing Medical Personnel Stress in Dealing with Covid-19 Patients

2021 ◽  
Vol 10 (2) ◽  
pp. 151-161
Author(s):  
Nurmukaromatis Saleha ◽  
Rina Delfina ◽  
Nurlaili Nurlaili ◽  
Fourni Ardiansyah ◽  
Mercy Nafratilova
Keyword(s):  
Social Support ◽  
Peer Support ◽  
Stress Level ◽  
Intervention Group ◽  
Management Training ◽  
Medical Personnel ◽  
T Test ◽  
Test Results ◽  
Stress Management Training ◽  
Post Test

The Covid-19 outbreak has psychological impacts on frontline medical personnel at risk of infection. Therefore, this study aimed to evaluate the effect of online affirmations and peer support on medical personnel stress level in dealing with Covid-19 patients, as well as social support and spiritual intelligence's influence. It was a quasi-experiment with pre- and post-test administered to 25 and 30 medical personnel as the intervention and control groups, respectively. The intervention was carried out on WhatsApp group for 4 weeks. The stress level pair T-test results showed p = 0.000 in the intervention group and p = 0.238 in the control, while the independent T-test results showed p = 0.009. Social support did not affect medical personnel’s stress (p=0.978), but the effect of spiritual intelligence was significant (p=0.000). According to the results of multiple regression test conducted using the Enter method, the coefficient value (R2) = 0.584. This intervention was effective in helping medical personnel to manage stress. Hence, hospital managers need to carry out stress management training to maintain medical personnel’s mental health.

Numerical Simulation of the Kinetic Energy Projectile Oblique Penetration into the Concrete

2014 ◽  
Vol 989-994 ◽  
pp. 982-985
Author(s):  
Jun Chen ◽  
Xiao Jun Ye
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Kinetic Energy ◽  
Three Dimensional ◽  
Test Results ◽  
Destruction Process ◽  
3D Finite Element ◽  
Finite Element Software ◽  
Simulation Results ◽  
Target Characteristics

ANSYS-LS/DYNA 3D finite element software projectile penetrating concrete target three-dimensional numerical simulation , has been the target characteristics and destroy ballistic missile trajectory , velocity and acceleration and analyze penetration and the time between relationship , compared with the test results , the phenomenon is consistent with the simulation results. The results show that : the destruction process finite element software can better demonstrate concrete tests revealed the phenomenon can not be observed , estimated penetration depth and direction of the oblique penetration missile deflection .

The Effect of Polypropylene Fiber on the Mechanical Properties of Self-Compacting Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 1325-1329
Author(s):  
Ye Ran Zhu ◽  
Jun Cai ◽  
Dong Wang ◽  
Guo Hong Huang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Polypropylene Fiber ◽  
Flexural Properties ◽  
Test Results ◽  
Self Compacting Concrete ◽  
Bending Tests ◽  
Flexural Toughness ◽  
Four Point Bending

This paper investigates the mechanical properties (compressive strength, splitting tensile strength and flexural toughness) of polypropylene fiber reinforced self-compacting concrete (PFRSCC). The effect of the incorporation of polypropylene fiber on the mechanical properties of PFRSCC is determined. Four point bending tests on beam specimens were performed to evaluate the flexural properties of PFRSCC. Test results indicate that flexural toughness and ductility are remarkably improved by the addition of polypropylene fiber.

scholarly journals Soil-concrete for use in the 3D printers in the construction of buildings and structures

2018 ◽  
Vol 245 ◽  
pp. 03002 ◽  
Author(s):  
Petr Iubin ◽  
Lubov Zakrevskaya
Keyword(s):  
Rheological Properties ◽  
Cement Paste ◽  
Clay Soil ◽  
Cement Composite ◽  
Cement Composites ◽  
Test Results ◽  
Flow Table ◽  
Key Factor ◽  
3D Printers ◽  
The Cost

Nowadays, the construction of cement composite using 3D printers is considered one of the most promising methods of automation of building processes. However, the compositions of cement composites have several disadvantages, such as high cost, short workability and etc. It has been suggested that clay soil as an additive will help to solve these problems partially. The aim of the work is development the cement compositions with clay soil, for use in 3D printers to construction. The composite consists of cement paste with clay soil and additives. To study printability of a composite the rheological properties in a fresh state were studied. The study of the rheological properties of composites was carried out using a flow table test for mortar. The key factor for determining the suitability of the composite for printing was accepted the diameter of the cone after shaking. The test results showed the possibility of replacing cement paste with clay soil up to 25% which leads to a reduction in the cost and an increase in printability with a slight decrease in the strength of the obtained material to 7%. Utilizing of soil from the construction site provides maximum economic efficiency of the material application.

Fatigue Crack Propagation in Clad RR58 Sheet to DTD 5070A: Analysis and Correlation of Test Results

1969 ◽  
Vol 73 (700) ◽  
pp. 335-339 ◽  
Author(s):  
D. P. Rooke ◽  
N. J. F. Gunn ◽  
J. T. Ballett ◽  
F. J. Bradshaw
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Aluminium Alloy ◽  
Fatigue Crack Propagation ◽  
Stress Level ◽  
Stress Conditions ◽  
Specimen Geometry ◽  
Aircraft Industry ◽  
Test Results ◽  
Obvious Advantage

In recent years there has been an increasing need for data on the rates of fatigue crack propagation in alloys of interest to the aircraft industry. In general alloys in which cracks grow slowly, under given stress conditions, have an obvious advantage over those in which cracks grow faster; there is more time to detect a crack before failure. It is possible that, in the future, quantitative crack propagation data may be used to give better estimates of the safe life of a structure. There is, however, a need to rationalise the presentation of such data and to study the effect of such parameters as specimen geometry and stress level. Some experiments to investigate the effect of varying some of these parameters in one clad aluminium alloy, DTD 5070A are described. It is a summary of work contained in two RAE Technical Reports.

scholarly journals Experimental Investigation on Flexural Behavior of Granite Stone Slabs with Near Surface Mounted CFRP Bars and Screw-Thread Steels

2018 ◽  
Vol 2018 ◽  
pp. 1-30
Author(s):  
Xiaopeng Gao ◽  
Zhongfan Chen ◽  
Xiaomeng Ding ◽  
Erxiang Dong
Keyword(s):  
Failure Load ◽  
Ductile Failure ◽  
Flexural Behavior ◽  
Screw Thread ◽  
Test Results ◽  
Cracking Behavior ◽  
Near Surface ◽  
Four Point Bending ◽  
Calculation Results ◽  
Near Surface Mounted

An experimental study that investigates the behavior of stone slabs strengthened in fixure with near surface mounted (NSM) technique using screw-thread steels and carbon fiber-reinforced polymer (CFRP) bars is presented. A total of ten full-scale stone slabs were tested under a four-point bending loading to investigate the effect of groove dimension, reinforcement ratios, and reinforcement materials on the flexural performance of stone slabs. The test results included failure characteristics, yield and ultimate capacities, deflection of midspan, and cracking behavior of stone slabs. The test results indicate that with the increase of groove height and groove width, cracking load and middeflection decrease by 6.4%–14.18%; however, failure load and middeflection increase by 4.7%–41.2%. Cracking load, failure load, and failure displacement of stone slabs adopting NSM screw-thread steels increased by 10.9%, 167%, and 617%, respectively, under the maximum reinforcement ratios of 0.629% over the control slab without NSM bars. Meanwhile, with the increase of reinforcement ratios, the failure mode transforms from brittle failure to ductile failure. The calculation results of strength are in agreement with the experimental results. Finally, it can be concluded that NSM CFRP bars are more effective than NSM screw-thread steels to improve flexural capacity with the same reinforcement ratios.

Numerical Analysis on Mechanical Properties of Beams Reinforced by CFRP Laminates

2015 ◽  
Vol 744-746 ◽  
pp. 196-200
Author(s):  
Ning Zhuang ◽  
Hao Dong Sun ◽  
Song Ge
Keyword(s):  
Large Scale ◽  
Growth Failure ◽  
High Strength ◽  
Test Results ◽  
Cfrp Laminates ◽  
Fiber Reinforced Plastic ◽  
Four Point Bending ◽  
Reinforced Plastic ◽  
Low Weight ◽  
Cfrp Sheet

Carbon Fiber Reinforced Plastic (CFRP) has been widely used in large-scale concrete infrastructure’s reinforcement and renovation because of its low weight and high strength, which promotes CFRP application in the field of civil engineering. This paper two aged beams reinforced by CFRP sheet was loaded to failure in four-point bending by laboratory experiment. Then the numerical model was built to simulate the destruction process and compared with test results. Based on the studying of this paper, the changing law of beam’s stress, ultimate bearing capacity growth, failure mode and cracking propagation was investigated during the loading process. The research has guiding significance for the design and construction of concrete structures reinforced by CFRP laminates.

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