High Strain Rate Tensile and Compressive Testing of Braided Composite Materials

2004 ◽  
Vol 1-2 ◽  
pp. 217-224 ◽  
Author(s):  
Nick Warrior ◽  
R. Fernie
Keyword(s):  
Composite Materials ◽  
Strain Rate ◽  
Vinyl Ester ◽  
Compressive Loading ◽  
Strain Rates ◽  
Compression Tests ◽  
Rate Dependency ◽  
Unit Cell Size ◽  
Tension And Compression ◽  
Falling Weight

Data from tension and compression tests at quasi-static and impact strain rates of up to 50s −1 (corresponding to impact speeds of up to 7ms −1) are presented to characterise the effect of strain rate on mechanical properties of triaxially braided carbon/vinyl ester. Three braid architectures were studied; 0°/±30°, 0°/±45° and 0°/±60° where the 0° was an 80k tow and the ±30° to ±60° braid tow was 12k. The methodologies and apparatus used were developed for testing composite materials with a large unit cell size at a range of strain rates and are based on novel tensile and compressive loading rigs in conjunction with a modified instrumented falling weight machine (drop tower). In the paper, the effects of increase in strain rate on fibre and matrix dominated material properties are presented. The ultimate tensile and compressive strengths were found to vary with rate. The axial properties of the braided carbon/vinyl ester, dominated by the 80K carbon fibre tow, were relatively insensitive to rate, but strong rate dependency was seen in the transverse directions where the effects of the polymer resin were more significant.

scholarly journals Effect of Strain Rate on the Transverse Tension and Compression Behavior of a Unidirectional Non-Crimp Fabric Carbon Fiber/Snap-Cure Epoxy Composite

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7314
Author(s):  
Khizar Rouf ◽  
Aaditya Suratkar ◽  
Jose Imbert-Boyd ◽  
Jeffrey Wood ◽  
Michael Worswick ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Fracture Surface ◽  
Strain Rate ◽  
Epoxy Composite ◽  
Strain Rates ◽  
Transverse Compression ◽  
Compression Tests ◽  
Rate Dependent ◽  
Transverse Tension ◽  
Tension And Compression

The strain rate-dependent behavior of a unidirectional non-crimp fabric (UD-NCF) carbon fiber/snap-cure epoxy composite loaded along the transverse direction under quasi-static and dynamic conditions was characterized. Transverse tension and compression tests at quasi-static and intermediate strain rates were performed using hydraulic testing machines, while a split Hopkinson pressure bar (SHPB) apparatus was used for transverse compression tests at high strain rates. A pulse shaper was used on the SHPB apparatus to ensure dynamic equilibrium was achieved and that the test specimens deformed homogenously with a nearly constant strain rate. The transverse tensile strength at a strain rate of 16 s−1 increased by 16% when compared to that at quasi-static strain rates, while distinct localized fracture surface morphology was observed for specimens tested at different strain rates. The transverse compressive yield stress and strength at a strain rate of 325 s−1 increased by 94% and 96%, respectively, when compared to those at quasi-static strain rates. The initial fracture plane orientation for the transverse compression tests was captured with high-speed cameras and found to increase with increasing strain rate. The study provides an important data set for the strain rate-dependent response of a UD-NCF composite material, while the qualitative fracture surface observations provide a deeper understanding of the failure characteristics.

scholarly journals Triaxial tests to determine a microstructure-based snow viscosity law

2000 ◽  
Vol 31 ◽  
pp. 457-462 ◽  
Author(s):  
Perry Bartelt ◽  
Markus Von Moos
Keyword(s):  
Strain Rate ◽  
Constitutive Relations ◽  
Viscoelastic Behavior ◽  
Final Analysis ◽  
Sample Volume ◽  
Triaxial Tests ◽  
Strain Rates ◽  
Rate Dependency ◽  
Tension And Compression ◽  
Ice Lattice

AbstractThis paper describes a new triaxial testing apparatus designed to determine the creep (viscoelastic) behavior of snow. The device is deformation-controlled and can apply strain rates between 10–7 s–1 and 10–2s–1 in tension and compression. The sample volume change is determined by measuring the displaced pore-air volume. During winters 1997/98 and 1998/99, >100 compression and tension tests were carried out. It is shown that snow is a highly non-linear but ideal viscoelastic material with a strong strain-rate dependency. A selection of test results is provided. We show how snow viscosity varies with density and strain rate. In a final analysis we interpret our results with respect to snow microstructure in order to develop microstructure-based constitutive relations which can be implemented in finite-element programs. Our results clearly show that for snow densities and strain rates tested, straining of the grain bonds is the primary mechanism of deformation within the snow ice lattice.

A Newly Developed Clamping Device for the Tension/Compression Test at Various Strain Rates

2014 ◽  
Vol 626 ◽  
pp. 353-358
Author(s):  
Geun Su Joo ◽  
Min Kuk Choi ◽  
Hoon Huh
Keyword(s):  
Strain Rate ◽  
Sheet Metal ◽  
Metal Forming ◽  
Loading Condition ◽  
Strain Rates ◽  
Compression Tests ◽  
Compression Behavior ◽  
Compression Loading ◽  
Hardening Behavior ◽  
Clamping Device

The tension/compression hardening behavior is important in sheet metal forming processes because of complicated loading paths. Experimental methods to measure the tension/ compression behavior have not considered the effect of the strain rate although the strain rate is related to the hardening behavior of sheet metal. The tension/compression tests need to be conducted considering the strain rate to acquire accurate hardening behavior.This paper deals with an experimental technique to measure the tension/compression behavior of sheet metal at various strain rates. A new clamping device was developed to prevent a sheet specimen from buckling under compression loading condition. Compared to previous clamping devices, the clamping device was devised to uniformly impose a clamping force and easily measure the strain from side of a specimen. Tension/compression tests have been conducted at various strain rates for SPCC and DP590 with displacement of 10%. Hardening curves under the tension or compression loading condition were obtained and analyzed with respect to the strain rate.

scholarly journals Hot Deformation Behavior of a Ni-Based Superalloy with Suppressed Precipitation

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 605
Author(s):  
Franco Lizzi ◽  
Kashyap Pradeep ◽  
Aleksandar Stanojevic ◽  
Silvana Sommadossi ◽  
Maria Cecilia Poletti
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Strain Rates ◽  
Compression Tests ◽  
Deformation Bands ◽  
Stress Softening ◽  
Relative Stress ◽  
The Matrix ◽  
Thermomechanical Processes

Inconel®718 is a well-known nickel-based super-alloy used for high-temperature applications after thermomechanical processes followed by heat treatments. This work describes the evolution of the microstructure and the stresses during hot deformation of a prototype alloy named IN718WP produced by powder metallurgy with similar chemical composition to the matrix of Inconel®718. Compression tests were performed by the thermomechanical simulator Gleeble®3800 in a temperature range from 900 to 1025 °C, and strain rates scaled from 0.001 to 10 s−1. Flow curves of IN718WP showed similar features to those of Inconel®718. The relative stress softening of the IN718WP was comparable to standard alloy Inconel®718 for the highest strain rates. Large stress softening at low strain rates may be related to two phenomena: the fast recrystallization rate, and the coarsening of micropores driven by diffusion. Dynamic recrystallization grade and grain size were quantified using metallography. The recrystallization grade increased as the strain rate decreased, although showed less dependency on the temperature. Dynamic recrystallization occurred after the formation of deformation bands at strain rates above 0.1 s−1 and after the formation of subgrains when deforming at low strain rates. Recrystallized grains had a large number of sigma 3 boundaries, and their percentage increased with strain rate and temperature. The calculated apparent activation energy and strain rate exponent value were similar to those found for Inconel®718 when deforming above the solvus temperature.

scholarly journals A Strain Rate-Dependent Damage Evolution Model for Concrete Based on Experimental Results

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Bin Xu ◽  
Xiaoyan Lei ◽  
P. Wang ◽  
Hui Song
Keyword(s):  
Strain Rate ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Model ◽  
Evolution Model ◽  
Experimental Results ◽  
Strain Rates ◽  
Compression Tests ◽  
Stress Strain ◽  
Actual Damage

There are various definitions of damage variables from the existing damage models. The calculated damage value by the current methods still could not well correspond to the actual damage value. Therefore, it is necessary to establish a damage evolution model corresponding to the actual damage evolution. In this paper, a strain rate-sensitive isotropic damage model for plain concrete is proposed to describe its nonlinear behavior. Cyclic uniaxial compression tests were conducted on concrete samples at three strain rates of 10−3s−1, 10−4s−1, and 10−5s−1, respectively, and ultrasonic wave measurements were made at specified strain values during the loading progress. A damage variable was defined using the secant and initial moduli, and concrete damage evolution was then studied using the experimental results of the cyclic uniaxial compression tests conducted at the different strain rates. A viscoelastic stress-strain relationship, which considered the proposed damage evolution model, was presented according to the principles of irreversible thermodynamics. The model results agreed well with the experiment and indicated that the proposed damage evolution model can accurately characterize the development of macroscopic mechanical weakening of concrete. A damage-coupled viscoelastic constitutive relationship of concrete was recommended. It was concluded that the model could not only characterize the stress-strain response of materials under one-dimensional compressive load but also truly reflect the degradation law of the macromechanical properties of materials. The proposed damage model will advance the understanding of the failure process of concrete materials.

Strain Rate Effect on Shear Behavior of Open-Graded Aggregates

2017 ◽  
Vol 2655 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Thomas Gebrenegus ◽  
Jennifer E. Nicks ◽  
Michael T. Adams
Keyword(s):  
Strain Rate ◽  
Axial Strain ◽  
Shear Behavior ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strength Parameter ◽  
Strain Rates ◽  
Rate Dependency ◽  
Confining Stress ◽  
Dilation Angle

Despite their wide application as construction materials in various earthworks built by state and local transportation agencies, the role of physical and mechanical factors in the strength and deformation behavior of crushed, manufactured open-graded aggregates (OGAs) is not well studied. In this investigation, the strain rate dependency of strength–deformation behaviors of two commonly employed crushed aggregates with small (12.7 mm) and large (38.1 mm) sizes is investigated. A 150-mm diameter triaxial testing device was used to conduct a drained compression test at five strain rates, ranging from 0.000083%/s to 0.0083%/s. To evaluate the significance of confining stress and density on the effect of strain rates, the shear tests were conducted at 34 kPa and 207 kPa effective confining stress levels, with the samples compacted at loose (30%) and dense (95%) relative densities. The peak friction angle, maximum dilation angle, secant modulus, and axial strain at which the aggregates started to dilate were determined to evaluate the strain rate effect on the shear behavior of OGAs. The results demonstrate that within the imposed quasistatic strain rate ranges, only the dilation angle showed an increasing trend with the increase in strain rate, whereas other extracted strength parameters were less sensitive to strain rate for both OGAs tested. Hence, the selection of strain rates according to ASTM specifications is appropriate for conducting strength parameter tests, used by practitioners for the design of geotechnical structures, on OGAs under quasistatic conditions.

Hot working of SP-700 titanium alloy with lamellar α + β starting structure using a processing map

2020 ◽  
Vol 111 (4) ◽  
pp. 297-306
Author(s):  
Amir Hosein Sheikhali ◽  
Maryam Morakkabati
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Hot Deformation ◽  
Processing Map ◽  
Microstructural Analysis ◽  
Shear Bands ◽  
Alpha Phase ◽  
Strain Rates ◽  
Compression Tests ◽  
Temperature Range

Abstract In this study, hot deformation behavior of SP-700 titanium alloy was investigated by hot compression tests in the temperature range of 700-9508C and at strain rates of 0.001, 0.1, and 1 s-1. Final mechanical properties of the alloy (hot compressed at different strain rates and temperatures) were investigated using a shear punch testing method at room temperature. The flow curves of the alloy indicated that the yield point phenomenon occurs in the temperature range of 800- 9508C and strain rates of 0.1 and 1 s-1. The microstructural analysis showed that dynamic globularization of the lamellar α phase starts at 7008C and completes at 8008C. The alpha phase was completely eliminated from b matrix due to deformation- induced transformation at 8508C. The microstructure of specimens compressed at 8508C and strain rates of 0.001 and 0.1 s-1showed the serration of beta grain boundaries, whereas partial dynamic recrystallization caused a necklace structure by increasing strain rate up to 1 s-1. The specimen deformed at 7008C and strain rate of 1 s-1was located in the instability region and localized shear bands formed due to the low thermal conductivity of the alloy. The processing map of the alloy exhibited a peak efficiency domain of 54% in the temperature range of 780-8108C and strain rates of 0.001- 0.008 s-1. The hot deformation activation energy of the alloy in the α/β region (305.5 kJ mol-1) was higher than that in the single-phase β region (165.2 kJ mol-1) due to the dynamic globularization of the lamellar a phase.

scholarly journals Constant Strain-Rate Tensile Testing of Natural Snow

1980 ◽  
Vol 26 (94) ◽  
pp. 519 ◽  
Author(s):  
H. Singh ◽  
F.W. Smith
Keyword(s):  
Strain Rate ◽  
Strain Gage ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Strain Rates ◽  
Strain Gages ◽  
Compression Tests ◽  
Snow Sample ◽  
Stress Strain ◽  
Natural Snow

Abstract In conducting tension and compression tests on snow samples, strains and strain-rates are usually determined from the displacements of the ends of the samples. In this work, a strain-gage which mounts directly onto the snow sample during testing, was developed and was found to give accurate and direct measurements of strain and strain-rates. A commercially available 0-28 pF variable capacitor was modified to perform the required strain measurements. It is a polished metallic plunger sliding inside a metal-coated glass tube. The plunger and tube were each soldered to the end of a spring-steel wire arm. To the other end of these arms were soldered to 10 mm square pads made of thin brass shim stock. The whole device weighs 2.5 g and the low coefficient of friction in the capacitor resulted in a very low actuation force. To mount the strain gage, the pads are wetted and frozen onto the snow sample. A high degree of sensitivity was achieved through the use of “phase-lock-loop” electronic circuitry. The capacitance change caused by the strain in the sample, changes the frequency of output signal from an oscillator and thus causes the change in output from the system. In the locked state, to which the system is constantly driven by a feed-back loop, the system output is almost ripple free. The strain gages were calibrated in the field in order to take into account the effects of very low field temperatures. The calibration curves were almost linear over the travel of 15 mm, the maximum limit. The sensitivity of the system is 4 mV per strain unit, but this could be increased by an order of magnitude by minor adjustments in the circuit. Constant strain-rate tensile tests were performed on natural snow at Berthoud Pass, Colorado, U.S.A., in the density range of 140-290 kg m-3. Four strain gages were mounted onto the samples to sense any non-uniform deformation which otherwise would have gone unnoticed or caused scatter in the data. The average indication of these gages was used to construct stress—strain curves for various types of snow at different strain-rates. The effect of strain-rate on the behavior of snow was studied. “Ratcheting” in the stress-strain curve in the region where the snow becomes plastic was observed first by Kinosita in his compression tests. A similar phenomenon was observed in these tension tests. It was found that directly measured strain is quite different from that which would be calculated from sample end movement. Strain softening was not observed in these tests up to total strains of 8%. The strain-rate effects found were comparable to the results of other investigators.

A Study on the Effects of Strain Rates on Characteristics of Brain Tissue

2017 ◽  
Author(s):  
Mohammad Hosseini Farid ◽  
Ashkan Eslaminejad ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Strain Rate ◽  
Brain Tissue ◽  
Mechanical Load ◽  
Experimental Studies ◽  
High Rate ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Compression Tests ◽  
Static Strain ◽  
The Brain

Traumatic brain injury (TBI) often happens when the brain tissue undergoes a high rate mechanical load. Although numerous research works have been carried out to study the mechanical characterization of brain matter under quasi-static (strain rate ≤ 100 S−1) loading but a limited amount of experimental studies are available for brain tissue behavior under dynamic strain rates (strain rate ≥ 100 S−1). In this paper, the results of a study on mechanical properties of ovine brain tissue under unconfined compression tests are to be presented. The samples were compressed under uniaxial strain rates of 0.0667, 3.33, 6.667, 33.33, 66.667 and 200 S−1. The brain tissue presents a stiffer response with increasing strain rate, showing a time-dependent behavior. So the hyperelastic-only models are not adequate to exhibit the brain viscoelasticity. Therefore, two hyper-viscoelastic constitutive equations based on power function model and Mooney-Rivlin energy function are applied to the results with quasi-static strain rate (≤ 100 S−1). Good agreement of experimental and theoretical has been achieved for results of the low strain rates. It is concluded that the obtained material parameters from quasi-static tests are not appropriate enough to fit the result with the high strain rate of 200 S−1. The study will further provide new insight into a better understanding of the rate-dependency behavior of the brain tissue under dynamic conditions. This is essential in the development of constitutive material characteristics for an efficient human brain finite element models to predict TBI under impact condition or high motion.

High Temperature Deformation Mechanisms and Processing Map for Hot Working of Cast-Homogenized Mg-3Sn-2Ca Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 3616-3621 ◽  
Author(s):  
K.P. Rao ◽  
Y.V.R.K. Prasad ◽  
Norbert Hort ◽  
Karl Ulrich Kainer
Keyword(s):  
Strain Rate ◽  
Processing Map ◽  
Volume Fraction ◽  
Flow Instability ◽  
Back Stress ◽  
Hot Working ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Compression Tests

The hot working behavior of Mg-3Sn-2Ca alloy has been investigated in the temperature range 300–500 oC and strain rate range 0.0003–10 s-1, with a view to evaluate the mechanisms and optimum parameters of hot working. For this purpose, a processing map has been developed on the basis of the flow stress data obtained from compression tests. The stress-strain curves exhibited steady state behavior at strain rates lower than 0.01 s-1 and at temperatures higher than 350 oC and flow softening occurred at higher strain rates. The processing map exhibited two dynamic recrystallization domains in the temperature and strain rate ranges: (1) 300–420 oC and 0.0003–0.003 s-1, and (2) 420–500 oC and 0.003–1.0 s-1, the latter one being useful for commercial hot working. Kinetic analysis yielded apparent activation energy values of 161 and 175 kJ/mole in domains (1) and (2) respectively. These values are higher than that for self-diffusion in magnesium suggesting that the large volume fraction of intermetallic particles CaMgSn present in the matrix generates considerable back stress. The processing map reveals a wide regime of flow instability which gets reduced with increase in temperature or decrease in strain rate.

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