scholarly journals Characterization of Dynamic Mechanical Parameters of Rock Fracture Evolution Based on Dry Coupling Point Contact Ultrasonic Technology

2020 ◽  
Vol 570 ◽  
pp. 052067
Author(s):  
Yang Liu ◽  
Lan Qiao ◽  
Yuan Li ◽  
Yuan Liu
Keyword(s):  
Rock Fracture ◽  
Point Contact ◽  
Mechanical Parameters ◽  
Dynamic Mechanical ◽  
Fracture Evolution ◽  
Ultrasonic Technology ◽  
Dry Coupling ◽  
Coupling Point

scholarly journals Experimental Evaluation of Shear Behavior of Stone Masonry Wall

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2313
Author(s):  
Maria Luisa Beconcini ◽  
Pietro Croce ◽  
Paolo Formichi ◽  
Filippo Landi ◽  
Benedetta Puccini
Keyword(s):  
Shear Behavior ◽  
Stone Masonry ◽  
Masonry Walls ◽  
Mechanical Parameters ◽  
In Situ Tests ◽  
Capacity Curves ◽  
Historical Structures ◽  
Definition Of

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

scholarly journals Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas

2022 ◽  
Vol 119 (3) ◽  
pp. e2117232119
Author(s):  
Giulio Franchini ◽  
Ivan D. Breslavsky ◽  
Francesco Giovanniello ◽  
Ali Kassab ◽  
Gerhard A. Holzapfel ◽  
...  
Keyword(s):  
Experimental Data ◽  
Smooth Muscle ◽  
Muscle Activation ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Viscoelastic Behavior ◽  
Material Model ◽  
Suitable Material ◽  
Dynamic Mechanical

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

On Dynamic Fracture of Rock Under Bit Impact Loads

1982 ◽  
Vol 104 (2) ◽  
pp. 105-107 ◽  
Author(s):  
I. E. Eronini
Keyword(s):  
Rock Fracture ◽  
Laboratory Data ◽  
Essential Elements ◽  
Dynamic Force ◽  
Rock Face ◽  
Time Histories ◽  
Drop Tests ◽  
Force Time ◽  
Indiana Limestone

A characterization of the dynamic interaction between an impacting tool and rock is presented. The analysis is based on the concept of rock fracture energy and on simple representations of the amount of fracturing and energy storage in the rock during fracture propagation. The governing equations are not complicated. They contain a small number of parameters and impose minimum restrictions on the form or sophistication of the model of the impacting tool. Simulation results are shown for bit-tooth drop tests on Indiana limestone under different values of the differential pressure across the rock face and for various heights of drop. The predicted dynamic force-penetration curves, force-time, displacement-time and velocity-time histories agree well with reported Laboratory data and demonstrate that the essential elements of tooth drop loading are adequately represented by the model.

Optical and Electrical Methods to Measure the Dynamic Behavior of a MEMS Gyroscope Sensor

2005 ◽  
Author(s):  
Alfredo Cigada ◽  
Elisabetta Leo ◽  
Marcello Vanali
Keyword(s):  
Laser Doppler Vibrometer ◽  
Mechanical Parameters ◽  
Mems Sensors ◽  
Electrical Method ◽  
Mems Gyroscope ◽  
Full Characterization ◽  
Design Specifications ◽  
Electrical Methods ◽  
Gyroscope Sensor

A full characterization of the mechanical parameters for vibrating MEMS sensors is required before integrating the mechanical and the electronic part. This is to verify that the main design specifications are fulfilled before sensors are available on the market. The main goal is to accurately establish the well-working devices in the shortest time. In this paper the electrical method based on the measurement of the GND current is used to satisfy this purpose. To check the validity of the achieved results through this method a comparison is done with those obtained through the widely used optical method based on vibration measurements through by means of a Laser Doppler Vibrometer (LDV).

Testing and Modeling of Mechanical Parameters in Resistance Welding Machines

2013 ◽  
Vol 712-715 ◽  
pp. 1235-1240
Author(s):  
Pei Wu ◽  
Yong An Zhang ◽  
Chuan Zhong Xuan ◽  
Yan Hua Ma
Keyword(s):  
Mechanical Response ◽  
Resistance Welding ◽  
Work Piece ◽  
Mechanical Parameters ◽  
Test Set ◽  
Dynamic Mechanical ◽  
Projection Welding ◽  
Welding Machine ◽  
Equivalent Mass ◽  
Set Up

The dynamic mechanical responses of resistance welding machine,which is mainly governed by the mechanical parameters of the machine, is very important to the weld quality especially in projection welding when collapse or deformation of work piece occurs. In this paper, a mathematical model for characterizing the dynamic mechanical response of resistance welding machine and a special test set-up called breaking test set-up have been developed. Based on the model and the test results, the mechanical parameters of the machine were identified, including the equivalent mass, the damping coefficient, and the stiffness for both electrode systems.

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