scholarly journals Experimental complexes for investigation of behavior of materials at a strain rate of 5·102÷105 s-1

2018 ◽  
Vol 226 ◽  
pp. 03024 ◽  
Author(s):  
Anatoly M. Bragov ◽  
Alexander Y. Konstantinov ◽  
Andrei K. Lomunov ◽  
Tatyana N. Yuzhina ◽  
Andrey R. Filippov
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Speed ◽  
Spall Strength ◽  
Pressure Sensors ◽  
Laser Interferometry ◽  
Strain Rate Range ◽  
Materials Testing ◽  
Dynamic Crack ◽  
Gas Guns

A description of experimental complexes, methodological and hardware means for determining the mechanical properties of materials under high-speed deformation and fracture is given in the report. Determination of mechanical properties in the strain rate range 5•102÷103 s-1 is the first direction of work in the laboratory of “Dynamic Materials Testing”. These tests are done using automated complexes based on the Kolsky method and its modifications for compression, tension and shearing. It is also possible to determine the fracture toughness, the characteristics of dynamic crack resistance, as well as to obtain stressstrain curves of low-density materials under uniaxial strain. Original gas guns with a caliber of 10, 20 and 57 mm are used for creation a dynamic load. The study of the behavior of materials at strain rates of 105 s-1 and higher is the second direction of work. In this case, the methods of a planewave shock experiment based on gas guns of 57 and 85 mm caliber are used. Manganine and dielectric pressure sensors, as well as laser interferometry are used for measuring the parameters of elastoplastic waves and for determining such important characteristics as impact compressibility, Hugoniot yield strength, spall strength.

scholarly journals Investigation of mechanical properties of limesand brick under dynamic loading

2018 ◽  
Vol 174 ◽  
pp. 02018
Author(s):  
Anatoliy Bragov ◽  
Andrey Lomunov ◽  
Alexander Konstantinov ◽  
Dmitriy Lamzin ◽  
Leopold Kruszka
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Strain Rate ◽  
Dynamic Loading ◽  
Energy Intensity ◽  
Strain Rate Range ◽  
Brazilian Test ◽  
Stress Rate ◽  
Rate Range ◽  
Kolsky Method

The results of experimental study of mechanical properties of samples of lime-sand brick under dynamic loading are presented. The tests were carried out using the traditional Kolsky method and its modification - dynamic splitting (the so-called «Brazilian test»). The laws of change in strength, strain, time properties and energy intensity of the investigated material are established in the strain rate range of 5·102-2.5·103 s-1 under compression and in the stress rate range of 2·101-3·102 GPa/s under tension.

The Methodic of Testing Using Experimental Equipment

2014 ◽  
Vol 635 ◽  
pp. 94-99
Author(s):  
Martin Kubelka ◽  
Tomáš Pačák ◽  
František Tatíček
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Speed ◽  
Mechanical Engineering ◽  
Manufacturing Technology ◽  
Strain Rates ◽  
Experimental Equipment ◽  
Material Behaviour ◽  
Pressing Process ◽  
Engineering Institute

During pressing using high speed, the material is stressed to the limit of its mechanical properties. And this generates problems during production. For this reason, opens debate on the factors previously neglected, such as the strain rate. For determining the effect of strain rate on the pressing process has been designed to CTU, Faculty of Mechanical Engineering, Institute of Manufacturing Technology, equipment for monitoring the behaviour of the material at different strain rates. The article describes the creation of testing methodologies material behaviour using this device.

scholarly journals Mechanical and structural properties of weak snow layers measured in situ

1998 ◽  
Vol 26 ◽  
pp. 1-6 ◽  
Author(s):  
Paul M. B. Föhn ◽  
Christian Camponovo ◽  
Georges Krüsi
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Strain Rate ◽  
Structural Properties ◽  
Strain Rate Range ◽  
Displacement Sensor ◽  
Dynamic Force ◽  
Rate Dependency ◽  
Snow Samples

Weak layers such as buried surface hoar or depth hoar frequently form the failure plane of slab avalanches. Therefore, the mechanical properties of such layers in relation to their snow structure have been investigated. Since it is difficult to transport samples containing a weak layer into cold rooms, the mechanical measurements have to be made in situ.We investigate strain-rate dependency of shear strength by measuring concurrently strength, deformation and acceleration, using a digital force gauge attached to a 0.05 m2 shear frame to which an accelerometer and a displacement sensor are fixed. In doing so, a dynamic force comparable to a driving skier is applied. The measurements cover a strain-rate range 10-2 to 1 s-1. The samples fail in a brittle manner. The shear-strength values cover the range 0.2–2.8 kPa. The dataset is also used to approximate the coefficient G, the shear modulus, for different weak layers.The snow structure has been analysed macroscopically in the field and for some layers representative snow samples have been extracted in order to prepare, in the cold laboratory, single-sided serial planes with cuts every 0.1 mm recorded by video. The analysis of these snow samples should have given the relation between some mechanical properties (strength, strain) and the structural properties. Due to basic problems in defining the connection between complex snow grains (e.g. surface hoar), we were unable to complete this part in due time. Only preliminary results on this aspect are presented here. Based on our long-term database, containing macroscopic structural and strength data of weak layers, a relationship between snow type and shear strength has been established.

scholarly journals Effect of Strain Rate on the Mechanical Properties of Cu/Ni Clad Foils

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6846
Author(s):  
Haiyang Wang ◽  
Chuanjie Wang ◽  
Linfu Zhang ◽  
Gang Chen ◽  
Qiang Zhu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Interface Layer ◽  
Strain Rate Range ◽  
Coarse Grained ◽  
Uniaxial Tensile ◽  
Rate Range ◽  
Static Strain

The performance of clad foils in microforming deserves to be studied extensively, where the strain rate sensitivity of the clad foil concerning the forming performance is a crucial factor. In this paper, the strain rate sensitivity of the mechanical properties of coarse-grained (CG) Cu/Ni clad foils in the quasi-static strain rate range (ε˙=10−4 s−1~10−1 s−1) is explored by uniaxial tensile tests under different strain rates. The results show that the strength and ductility increase with strain rate, and the strain rate sensitivity m value is in the range of 0.012~0.015, which is three times the value of m for CG pure Cu. The fracture morphology shows that slip bands with different directions are entangled in localized areas near the interface layer. Molecular dynamics simulations demonstrate the formation of many edged dislocations at the Cu/Ni clad foils interface due to a mismatch interface. The improved ductility and strain rate sensitivity is attributed to the interaction and plugging of the edged dislocations with high density in the interface layer. Additionally, the influence of size effect on mechanical properties is consistently present in the quasi-static strain rate range. This paper helps to understand the strain rate sensitivity of CG clad foils and to develop clad foils in microforming processes.

scholarly journals Experimental Study on the Influence of Freezing Pressure on the Uniaxial Mechanical Properties of Ice

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Baosheng Wang ◽  
Weihao Yang ◽  
Peixin Sun ◽  
Xin Huang ◽  
Yaodan Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Strain Rate ◽  
Uniaxial Compression ◽  
Peak Stress ◽  
Strain Rate Range ◽  
Brittleness Index ◽  
Rate Range ◽  
Minimum Value ◽  
Maximum Minimum

In this study, a test technique that enables continuous control of the sample stress state from freezing to testing is proposed to investigate the influence of freezing pressure on the mechanical properties of ice under uniaxial compression. In this method, the water is frozen into the standard cylindrical ice specimen under high hydraulic pressure in a triaxial pressure chamber, and then, the temperature field and stress field of the ice specimens are adjusted to the initial state of the test; finally, an in situ mechanical test is conducted in the triaxial chamber. The uniaxial compression test of ice specimens with temperature of −20°C and freezing pressure of 0.5–30 MPa is performed in the strain rate range of 5 × 10−5−1.5 × 10−6 s−1. The results show that, as the freezing pressure increases, the ductile-to-brittle transition zone of the ice specimen during failure moves to the low strain rate range, and the failure mode of the specimen changes from shear failure to splitting failure. Further, the brittleness index of the ice specimen first increases, then decreases, and then again increases with the increase in freezing pressure. The brittleness index reaches the maximum (minimum) when the freezing pressure is 30 MPa (20 MPa). The peak stress of the ice specimen also increases first, then decreases, and then increases with the increase in freezing pressure. The maximum value is also at the freezing pressure of 30 MPa, but the minimum value is obtained at the freezing pressure of 0.5 MPa. The failure strain of the ice specimen first decreases and then increases with the increase in freezing pressure, and the maximum (minimum) value is achieved at the freezing pressure of 0.5 MPa (10 MPa). When the ice specimen exhibits brittle failure, the relationships between the residual stress and the freezing pressure and between the peak stress and freezing pressure are the same, but when the ice specimen exhibits ductile failure, there is no obvious relationship between the residual stress and the freezing pressure.

scholarly journals In-Situ Damage Evaluation of Pure Ice under High Rate Compressive Loading

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1236 ◽  
Author(s):  
Isakov ◽  
Lange ◽  
Kilchert ◽  
May
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Compressive Loading ◽  
Compressive Load ◽  
Strain Rate Range ◽  
High Rate ◽  
Hopkinson Pressure Bar ◽  
Order Of Magnitude ◽  
Pressure Bar

The initiation and propagation of damage in pure ice specimens under high rate compressive loading at the strain rate range of 100 s−1 to 600 s−1 was studied by means of Split Hopkinson Pressure Bar measurements with incorporated high-speed videography. The results indicate that local cracks in specimens can form and propagate before the macroscopic stress maximum is reached. The estimated crack velocity was in the range of 500 m/s to 1300 m/s, i.e., lower than, but in similar order of magnitude as the elastic wave speed within ice. This gives reason to suspect that already at this strain rate the specimen is not deforming under perfect force equilibrium when the first cracks initiate and propagate. In addition, in contrast to quasi-static experiments, in the high rate experiments the specimens showed notable residual load carrying capacity after the maximum stress. This was related to dynamic effects in fractured ice particles, which allowed the specimen to carry compressive load even in a highly damaged state.

The Effect of Strain Rate on the Mechanical Properties of Human Cortical Bone

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Ulrich Hansen ◽  
Peter Zioupos ◽  
Rebecca Simpson ◽  
John D. Currey ◽  
David Hynd
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Cortical Bone ◽  
Maximum Load ◽  
Strain Rate Range ◽  
Stress And Strain ◽  
Tension Stress ◽  
Strain Rates ◽  
Tension And Compression ◽  
Ductile To Brittle Transition

Bone mechanical properties are typically evaluated at relatively low strain rates. However, the strain rate related to traumatic failure is likely to be orders of magnitude higher and this higher strain rate is likely to affect the mechanical properties. Previous work reporting on the effect of strain rate on the mechanical properties of bone predominantly used nonhuman bone. In the work reported here, the effect of strain rate on the tensile and compressive properties of human bone was investigated. Human femoral cortical bone was tested longitudinally at strain rates ranging between 0.14–29.1s−1 in compression and 0.08–17 s−1 in tension. Young’s modulus generally increased, across this strain rate range, for both tension and compression. Strength and strain (at maximum load) increased slightly in compression and decreased (for strain rates beyond 1 s−1) in tension. Stress and strain at yield decreased (for strain rates beyond 1 s−1) for both tension and compression. In general, there seemed to be a relatively simple linear relationship between yield properties and strain rate, but the relationships between postyield properties and strain rate were more complicated and indicated that strain rate has a stronger effect on postyield deformation than on initiation of yielding. The behavior seen in compression is broadly in agreement with past literature, while the behavior observed in tension may be explained by a ductile to brittle transition of bone at moderate to high strain rates.

scholarly journals Investigation on Mechanical Properties and Reaction Characteristics of Al-PTFE Composites with Different Al Particle Size

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Jia-xiang Wu ◽  
Xiang Fang ◽  
Zhen-ru Gao ◽  
Huai-xi Wang ◽  
Jun-yi Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
High Speed ◽  
Structural Characteristics ◽  
Testing Machine ◽  
Strain Rate Range ◽  
Drop Weight ◽  
Hardening Modulus ◽  
Reaction Characteristics ◽  
Ptfe Composites

Al-PTFE (aluminum-polytetrafluoroethylene) serves as one among the most promising reactive materials (RMs). In this work, six types of Al-PTFE composites with different Al particle sizes (i.e., 50 nm, 1∼2 μm, 6∼7 μm, 12∼14 μm, 22∼24 μm, and 32∼34 μm) were prepared, and quasistatic compression and drop weight tests were conducted to characterize the mechanical properties and reaction characteristics of Al-PTFE composites. The reaction phenomenon and stress-strain curves were recorded by a high-speed camera and universal testing machine. The microstructure of selected specimens was anatomized through adopting a scanning electron microscope (SEM) to correlate the mesoscale structural characteristics to their macroproperties. As the results indicated, in the case of quasistatic compression, the strength of the composites was decreased (the yield strength falling from 22.7 MPa to 13.6 MPa and the hardening modulus declining from 33.3 MPa to 25 MPa) with the increase of the Al particle size. The toughness rose firstly and subsequently decreased and peaked as 116.42 MJ/m3 at 6∼7 μm. The reaction phenomenon occurred only in composites with the Al particle size less than 10 μm. In drop weight tests, six types of specimens were overall reacted. As the Al particle size rose, the ignition energy of the composites enhanced and the composites turned out to be more insensitive to reaction. In a lower strain rate range (10−2·s−1∼102·s−1), Al-PTFE specimens take on different mechanical properties and reaction characteristics in the case of different strain rates. The formation of circumferential open cracks is deemed as a prerequisite for Al-PTFE specimens to go through a reaction.

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