Strength and deformation of frozen saturated sand at −30 °C

1982 ◽  
Vol 19 (1) ◽  
pp. 104-107 ◽  
Author(s):  
V. R. Parameswaran ◽  
M. Roy
Keyword(s):  
Strain Rate ◽  
Power Law ◽  
Quartz Sand ◽  
Peak Strength ◽  
Strain Rates ◽  
Saturated Sand ◽  
Ideal Plastic ◽  
Strength And Deformation ◽  
Power Law Equation

Frozen saturated quartz sand containing 20% moisture by weight, when deformed at −30 °C at various strain rates, showed various modes of behaviour such as visco-plastic, almost ideal plastic, and brittle with little plasticity with increasing order of strain rate. The values of peak strength observed for strain rates between 5 × 10−7 and 6 × 10−3 s−1 were in the range 15–42 MPa, stress being related to strain rate by a power-law equation.

scholarly journals Effects of loading rate on strength and deformation characteristics of gypsum mixed sand

2019 ◽  
Vol 92 ◽  
pp. 05008
Author(s):  
Zain Maqsood ◽  
Junichi Koseki ◽  
Hiroyuki Kyokawa
Keyword(s):  
Strain Rate ◽  
Axial Strain ◽  
Constitutive Modelling ◽  
Strain Rates ◽  
Deformation Characteristics ◽  
Wide Range ◽  
Strength And Deformation ◽  
Loading Tests ◽  
Rational Evaluation ◽  
Strain Responses

It has been unanimously acknowledged that the strength and deformation characteristics of bounded geomaterials, viz. cemented soils and natural rocks, are predominantly governed by the rate of loading/deformation. Rational evaluation of these time-dependent characteristics due to viscosity and ageing are vital for the reliable constitutive modelling. In order to study the effects of ageing and loading/strain rate (viscosity) on the behaviour of bounded geomaterials, a number of unconfined monotonic loading tests were performed on Gypsum Mixed Sand (GMS) specimens at a wide range of axial strain rates; ranging from 1.9E-05 to 5.3E+00 %/min (27,000 folds), and at different curing periods. The results indicate shifts in the viscous behaviour of GMS at critical strain rates of 2.0E-03 and 5.0E-01 %/min. In the light of this finding, the results are categorized into three discrete zones of strain rates, and the behaviour of GMS in each of these zones is discussed. A significant dependency of peak strength and stress-strain responses on strain rate was witnessed for specimens subjected to strain rates lesser than 2.0E-03 %/min, and the effects of viscosity/strain rate was found to be insignificant at strain rate higher than 5.0E-01%/min.

The Effect of Strain Rate on Yielding in High Strength Steels

1966 ◽  
Vol 88 (1) ◽  
pp. 37-44 ◽  
Author(s):  
D. P. Kendall ◽  
T. E. Davidson
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Power Law ◽  
High Strength Steels ◽  
Rate Sensitivity ◽  
High Strength ◽  
Strain Rates ◽  
Alloy Steels ◽  
Strength Alloy ◽  
Continuous Power

The effect of strain rates ranging from 10−4 to 10 in/in/sec on the yield strengths of several high strength alloy steels is investigated. Quenched and tempered-type alloys exhibit two regions of strain-rate sensitivity with the strain rate dividing the sensitive and insensitive regions varying from 0.5 to greater than 10 in/in/sec, depending on composition, microstructure and grain size. At the higher rates a power-law relationship is found which is consistent with a yielding model involving breakaway of dislocations from solute atmospheres. Maraging steel exhibits a continuous power law-strain rate sensitivity over the entire range.

scholarly journals Effect of strain rate on strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy

2021 ◽  
Vol 250 ◽  
pp. 05012
Author(s):  
Sebastian Henschel ◽  
Lutz Krüger
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Image Correlation ◽  
Coarse Grained ◽  
Strain Rates ◽  
Localized Deformation ◽  
Strength And Deformation

The strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy at different strain rates was studied. Furthermore, the effect of grain size was investigated. To this end, a batch with bamboo-like grain arrangement and a batch with smaller, nevertheless coarse, grains were analyzed. Tensile tests at quasi-static, intermediate, and dynamic loading rates were performed. Digital image correlation and microstructural analysis revealed the localized deformation and phase transformation in favorable oriented grains. At higher strain rates, a increased number of orientations was activated for the phase transformation. A higher strain rate resulted in an increased strength for the coarse-grained material while the bamboo-like material did not show this effect. The analysis of fracture surfaces revealed ductile fracture and cleavage fracture for all strain rates.

scholarly journals Experimental Investigation on Strength and Deformation Characteristics of Red Sandstone at Strain Rates of 10−2∼55 s−1

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jie Shi ◽  
Zongmu Luo ◽  
Huachao Liu ◽  
Dan Wang ◽  
Haipeng Shen ◽  
...  
Keyword(s):  
Strain Rate ◽  
Elastic Strain ◽  
Strain Energy ◽  
Loading Condition ◽  
Elastic Strain Energy ◽  
Strain Rates ◽  
Deformation Characteristics ◽  
Intermediate Strain Rate ◽  
Blasting Excavation ◽  
Strength And Deformation

The mechanical properties of rocks under low to intermediate strain rate are of great importance for seismic engineering, rock impact, and blasting excavation. To study the strength and deformation characteristics of sandstone subjected to low-medium speed impact loading, the complete stress-strain relationships of uniaxial compression at strain rates of 10−2∼55 s−1 were obtained utilizing MTS and drop weight impact test devices. It is indicated that the dynamic compressive strength of sandstone in the range of intermediate strain rate increases approximately linearly with the strain rate under the quasi-static loading condition, while increasing nonlinearly under the dynamic loading condition. The deformation and fracture process of sandstone still consists of pore compaction stage, elastic deformation stage, instable microcrack propagation stage, and brittle fracture stage. The peak stress, critical strain, and residual strain increase with an increase in the strain rate, and the corresponding fracture mode changes from shear failure to split failure. The evolution law of total absorbed strain energy with deformation coincides with that of stored elastic strain energy for sandstone at the intermediate strain rate. The effect of the strain rate on elastic strain energy is more significant than that of dissipated strain energy. Furthermore, both the brittleness and fracture degree of sandstone become more remarkable with the strain rate increasing.

scholarly journals DYNAMIC TESTS OF FROZEN SAND SOILS

2019 ◽  
Vol 81 (4) ◽  
pp. 443-448
Author(s):  
V.V. Balandin ◽  
L.V. Meyer ◽  
S. Abdel-Malek
Keyword(s):  
Moisture Content ◽  
Strain Rate ◽  
Dynamic Properties ◽  
Experimental Studies ◽  
Uniaxial Stress ◽  
Frozen Soil ◽  
Strain Rates ◽  
Saturated Sand ◽  
Frozen Sand ◽  
Water Saturated

The study of the laws of contact interaction of hard and deformable impactors with frozen soils is of great scientific and applied value. In solving such problems, numerical methods are widely used. For numerically modeling the behavior of frozen soil under dynamic loading, it is necessary to use models of soil media that adequately describe their behavior at various negative temperatures, humidities and strain rates. To identify the parameters of these models, experimental studies are required for determining dynamic properties of soils at low temperatures. The paper presents the results of experimental studies of dynamic deformation of samples of frozen sand with humidities of 10% and 18%. Compression experiments were conducted using a stand implementing the Kolsky method. Deformation curves of frozen sand at a temperature of -18 °С were obtained under uniaxial stress conditions at various strain rates in the range of 400-2500 s-1. Diagrams of strength of frozen sand under uniaxial compression as a function of strain rate are constructed. The diagrams are linear for samples of different humidity in the studied range of strain rates. Maximum stresses in frozen water-saturated sand are higher than those in frozen sand of 10% humidity. With increasing strain rate, compressive strength of water-saturated sand grows faster than that of sand with a moisture content of 10%: at a strain rate of about 500 s-1, the stresses in frozen water-saturated sand, at which the samples fail, are 1.5 times higher than those in the frozen sand with a moisture content of 10%, and at a strain rate of 2500 s-1 they are 3 times as high.

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

Conductivity, Dielectric and Modulus study of NH4PF6 based Zwitterionic polymer electrolyte

2020 ◽  
Vol 13 ◽  
Author(s):  
Manindra Kumar ◽  
Neelabh Srivastava
Keyword(s):  
Polymer Electrolyte ◽  
Power Law ◽  
Loss Tangent ◽  
Electric Modulus ◽  
Relaxation Behavior ◽  
Conductivity Data ◽  
Frequency Range ◽  
Zwitterionic Polymer ◽  
Power Law Equation ◽  
Jonscher’S Power Law

Background and Objective: Zwitterionic polymer electrolyte has been successfully synthesized using NH4PF6 salt. The conductivity of the synthesized polymer membrane is found to be of the order of 10-3Scm-1. Dielectric and Modulus properties of the polymer electrolyte have also been studied which showed well relaxation peaks with both temperature and salt concentrations. Result: This is well depicted with the loss tangent curve. Debye type relaxation behavior has observed from the electric modulus. Conclusion: Frequency dependent conductivity data (fitted with Jonscher's power law equation) confirmed the presence of NCL/SLPL type behavior in the studied frequency range.

scholarly journals A Review on Mechanical Properties of Natural Fibre Reinforced Polymer Composites under Various Strain Rates

2021 ◽  
Vol 5 (5) ◽  
pp. 130
Author(s):  
Tan Ke Khieng ◽  
Sujan Debnath ◽  
Ernest Ting Chaw Liang ◽  
Mahmood Anwar ◽  
Alokesh Pramanik ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Polymer Composites ◽  
Stress Transfer ◽  
Natural Fibre ◽  
Transfer Efficiency ◽  
Strain Rates ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Fibre Matrix

With the lightning speed of technological evolution, the demand for high performance yet sustainable natural fibres reinforced polymer composites (NFPCs) are rising. Especially a mechanically competent NFPCs under various loading conditions are growing day by day. However, the polymers mechanical properties are strain-rate dependent due to their viscoelastic nature. Especially for natural fibre reinforced polymer composites (NFPCs) which the involvement of filler has caused rather complex failure mechanisms under different strain rates. Moreover, some uneven micro-sized natural fibres such as bagasse, coir and wood were found often resulting in micro-cracks and voids formation in composites. This paper provides an overview of recent research on the mechanical properties of NFPCs under various loading conditions-different form (tensile, compression, bending) and different strain rates. The literature on characterisation techniques toward different strain rates, composite failure behaviours and current challenges are summarised which have led to the notion of future study trend. The strength of NFPCs is generally found grow proportionally with the strain rate up to a certain degree depending on the fibre-matrix stress-transfer efficiency. The failure modes such as embrittlement and fibre-matrix debonding were often encountered at higher strain rates. The natural filler properties, amount, sizes and polymer matrix types are found to be few key factors affecting the performances of composites under various strain rates whereby optimally adjust these factors could maximise the fibre-matrix stress-transfer efficiency and led to performance increases under various loading strain rates.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

scholarly journals Using Artificial Neural Networks to Predict Influences of Heterogeneity on Rock Strength at Different Strain Rates

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3042
Author(s):  
Sheng Jiang ◽  
Mansour Sharafisafa ◽  
Luming Shen
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Strain Rate ◽  
Network Model ◽  
Neural Network Model ◽  
Artificial Neural Network Model ◽  
Rock Strength ◽  
Strain Rates ◽  
Filling Material ◽  
Artificial Neural

Pre-existing cracks and associated filling materials cause the significant heterogeneity of natural rocks and rock masses. The induced heterogeneity changes the rock properties. This paper targets the gap in the existing literature regarding the adopting of artificial neural network approaches to efficiently and accurately predict the influences of heterogeneity on the strength of 3D-printed rocks at different strain rates. Herein, rock heterogeneity is reflected by different pre-existing crack and filling material configurations, quantitatively defined by the crack number, initial crack orientation with loading axis, crack tip distance, and crack offset distance. The artificial neural network model can be trained, validated, and tested by finite 42 quasi-static and 42 dynamic Brazilian disc experimental tests to establish the relationship between the rock strength and heterogeneous parameters at different strain rates. The artificial neural network architecture, including the hidden layer number and transfer functions, is optimized by the corresponding parametric study. Once trained, the proposed artificial neural network model generates an excellent prediction accuracy for influences of high dimensional heterogeneous parameters and strain rate on rock strength. The sensitivity analysis indicates that strain rate is the most important physical quantity affecting the strength of heterogeneous rock.

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