Laser diffractometry of the surface of fatigue fractures under applied cyclic loads

1988 ◽  
Vol 20 (7) ◽  
pp. 972-976
Author(s):  
A. V. Matokhin ◽  
V. V. Yudin ◽  
G. V. Matokhin ◽  
T. Yu. Yakovleva ◽  
A. V. Khlamenok
Keyword(s):  
Cyclic Loads ◽  
Laser Diffractometry ◽  
Fatigue Fractures

scholarly journals Experimental study of factors affecting the failure of the cyclical nature of rotary endodontic instruments

2020 ◽  
Vol 18 (1) ◽  
pp. 4-14
Author(s):  
V. G. Deviatnikova ◽  
T. N. Manak
Keyword(s):  
Root Canal ◽  
Statistical Data ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Cyclic Loads ◽  
Bending Angle ◽  
Factors Affecting ◽  
Main Factors ◽  
Number Of Cycles ◽  
Fatigue Fractures

Relevance. The properties of shape memory, superelasticity and plasticity in nickel-titanium tools make the visual prediction of breakage as difficult as possible. Therefore, an important role is given to research, the purpose of which is to predict the time of their work and to identify the main factors affecting the probability of a fracture.Aim. Comparison of cyclic fatigue resistance of Ni-Ti rotary endodontic instruments of various manufacturers.Materials and methods. The influence of the autoclaving procedure and the angle of bending of the root canal on the resistance of a rotating endodontic instrument to cyclic loads was studied using an author's patented device that simulates the rotation of an instrument in a real channel; the number of cycles completed by each instrument before its fracture was recorded. The morphology of fractures, the microstructure of specimens under fractures, and the microhardness of specimens of endodontic instruments after testing were studied.Results. It has been established that resistance to fatigue fractures of instruments of various endodontic systems decreases with an increase in the bending angle of the root canal. For Endostar E3 Basic Rotary System tools, the number of cycles decreased by 1.2 times, for Protaper Universal tools by 2.9 times. The tools of the Protaper Next system reduced the number of cycles at a bending angle of the artificial root canal of 60 degrees by 1.5 times compared with the number of cycles at a bending angle of 45 degrees. At the same time, statistical data and the study of the microstructure of samples of new and past 6 cycles of autoclave tools did not show a connection between the autoclaving procedure and a decrease in their resistance to cyclic loads.Conclusions. When working in complex bent over 45 degrees channels, it is rational to choose an endodontic instrument that has undergone heat treatment at the production stage (in the framework of this study, it was Protaper Next 25/06 M-Wire alloy). This will reduce the likelihood of a file fracture and associated dangerous complications of endodontic treatment.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

Aging of polymer composite materials under loading. (See Beginning in #10-2020)

2020 ◽  
pp. 2-12
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Polymer Composite ◽  
Polymer Composite Materials ◽  
Cyclic Loads ◽  
Reinforced Plastics ◽  
Water Exposure ◽  
Laboratory Conditions ◽  
Bending Loads ◽  
Moisture Conditions

A study review of aging polymer composite materials (PCM) under different heat-moisture conditions or water exposure with the sequential or parallel influence of static or cyclic loads in laboratory conditions is presented. The influence of tension and bending loads is compared. Conditions of the different load influence on parameters of carbon-reinforced plastics and glass-reinforced plastics are discussed. Equipment and units for climatic tests of PCM under loading are described. Simulation examples of indices of mechanical properties of PCM under the influence of environment and loads are shown.

Aging of polymer composite materials under loading

2020 ◽  
pp. 7-18
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Polymer Composite ◽  
Polymer Composite Materials ◽  
Cyclic Loads ◽  
Reinforced Plastics ◽  
Water Exposure ◽  
Laboratory Conditions ◽  
Bending Loads ◽  
Moisture Conditions

A study review of aging polymer composite materials (PCM) under different heat-moisture conditions or water exposure with the sequential or parallel influence of static or cyclic loads in laboratory conditions is presented. The influence of tension and bending loads is compared. Conditions of the different load influence on parameters of carbon-reinforced plastics and glass-reinforced plastics are discussed. Equipment and units for climatic tests of PCM under loading are described. Simulation examples of indices of mechanical properties of PCM under the influence of environment and loads are shown.

scholarly journals Shear Capacity of Reinforced Concrete Beams under Monotonic and Cyclic Loads: Experiments and Computational Models

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4092
Author(s):  
Kamil Bacharz ◽  
Barbara Goszczyńska
Keyword(s):  
Reinforced Concrete ◽  
Laboratory Tests ◽  
Computational Models ◽  
Concrete Beams ◽  
Shear Capacity ◽  
Reinforced Concrete Beams ◽  
Image Correlation ◽  
Engineering Practice ◽  
Cyclic Loads ◽  
Loading Modes

The paper reports the results of a comparative analysis of the experimental shear capacity obtained from the tests of reinforced concrete beams with various static schemes, loading modes and programs, and the shear capacity calculated using selected models. Single-span and two-span reinforced concrete beams under monotonic and cyclic loads were considered in the analysis. The computational models were selected based on their application to engineering practice, i.e., the approaches implemented in the European and US provisions. Due to the changing strength characteristics of concrete, the analysis was also focused on concrete contribution in the shear capacity of reinforced concrete beams in the cracked phase and on the angle of inclination of diagonal struts. During the laboratory tests, a modern ARAMIS digital image correlation (DIC) system was used for tracking the formation and development of diagonal cracks.

Flaw-sensitivity of a tough hydrogel under monotonic and cyclic loads

2021 ◽  
pp. 104483
Author(s):  
Yifan Zhou ◽  
Jian Hu ◽  
Pingping Zhao ◽  
Wenlei Zhang ◽  
Zhigang Suo ◽  
...  
Keyword(s):  
Cyclic Loads ◽  
Flaw Sensitivity
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