scholarly journals Effects of Cyclic Freezing and Thawing on the Shear Behaviors of an Expansive Soil under a Wide Range of Stress Levels

2021 ◽  
Author(s):  
Wei-lie Zou ◽  
Zhong Han ◽  
Gui-tao Zhao ◽  
Kewei Fan ◽  
Sai K. Vanapalli ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Softening ◽  
Expansive Soil ◽  
Friction Angle ◽  
Shearing Stress ◽  
Freezing And Thawing ◽  
Confining Stress ◽  
Stress Strain ◽  
Apparent Cohesion ◽  
Wide Range

Abstract The focus of this paper is directed towards investigating the influence of multiple freeze-thaw (FT) cycles on the stress-strain relationships during undrained shearing for an expansive soil under a wide range of confining stresses (σc) from 0 to 300 kPa. Different numbers of FT cycles were applied to compacted specimens. The influence of FT cycles on the soil’s structure was investigated using mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests. FT impacted specimens were subjected to consolidated undrained (CU) shear tests with pore pressure measurement (σc = 10 to 300 kPa) and unconfined compression (UC) tests (σc = 0 kPa) to derive the shearing stress-strain relationships and the associated mechanical properties including (i) failure strength (qu), elastic modulus (Eu), effective and apparent cohesion (c’ and c), and effective and apparent friction angle (ϕ’ and ϕ) obtained from CU tests and (ii) qu and reloading modulus (E1%) and stress (Su1%) at 1% strain obtained from UC tests. Testing results show that FT cycles mainly influence the soil’s macropores with diameters between 5 and 250 microns. Cracks develop during FT cycles and result in slight swelling which contributes to an increase in the global volume of the soil specimens. There is a significant reduction in the investigated mechanical properties after FT cycles. They typically achieve equilibrium after about 6 cycles. The shearing stress-strain curves transits from strain-softening to strain-hardening as the confining stress increases. An empirical model is developed to describe the strain-softening behavior of the specimens under low confining stresses. The model is simple to use and well describes all stress-strain curves obtained in this study that show strain-softening characteristics.

INVESTIGATING THE INFLUENCE OF ENVIRONMENTAL CONDITIONING ON EPOXY RESINS AT QUASISTATIC AND HIGH STRAIN RATES FOR MATERIAL OPERATING LIMIT

2021 ◽  
Author(s):  
SAGAR M. DOSHI, SAGAR M. DOSHI, ◽  
NITHINKUMAR MANOHARAN ◽  
BAZLE Z. (GAMA) HAQUE, ◽  
JOSEPH DEITZEL ◽  
JOHN W. GILLESPIE, JR.
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Yield Stress ◽  
High Strain ◽  
Operating Conditions ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Wide Range ◽  
Environmental Aging

Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55°C to 76°C) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environmental factors also affect the resin properties and hence influence the performance of the composites. Therefore, it is critical to determine the stress-strain behavior of the epoxy resin over a wide range of strain rates and temperatures for accurate multi-scale modeling of composites and to investigate the influence of environmental aging on the resin properties. Additionally, the characterization of key mechanical properties such as yield stress, modulus, and energy absorption (i.e. area under the stress-strain curve) at varying temperatures and moisture can provide critical data to calculate the material operating limits. In this study, we characterize mechanical properties of neat epoxy resin, SC-15 (currently used in structural armor) and RDL-RDC using uniaxial compression testing. RDL-RDC, developed by Huntsman Corporation, has a glass transition temperature of ~ 120°C, compared to ~ 85°C of SC-15. A split Hopkinson pressure bar is used for high strain rate testing. Quasistatic testing is conducted using a screw-driven testing machine (Instron 4484) at 10-3 s-1 and 10-1 s-1 strain rates and varying temperatures. The yield stress is fit to a modified Eyring model over the varying strain rates at room temperature. For rapid investigation of resistance to environmental aging, accelerated aging tests are conducted by immersing the specimens in 100°C water for 48 hours. Specimens are conditioned in an environmental chamber at 76 °C and 88% RH until they reach equilibrium. Tests are then conducted at five different temperatures from 0°C to 95°C, and key mechanical properties are then plotted vs. temperature. The results presented are an important step towards developing a methodology to identify environmental operating conditions for composite ground vehicle applications.

Wide-range linear viscoelastic hydrogels with high mechanical properties and their applications in quantifiable stress-strain sensors

2020 ◽  
Vol 399 ◽  
pp. 125697 ◽  
Author(s):  
Changshu Ma ◽  
Yi Wang ◽  
Zuming Jiang ◽  
Zhenxing Cao ◽  
Huiting Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Sensors ◽  
Stress Strain ◽  
Wide Range ◽  
Linear Viscoelastic

Strain localization due to structural softening during pressure sensitive rate independent yielding

2013 ◽  
Vol 184 (4-5) ◽  
pp. 357-371 ◽  
Author(s):  
Laetitia Le Pourhiet
Keyword(s):  
Shear Band ◽  
Strain Softening ◽  
Shear Bands ◽  
Limit Load ◽  
Friction Angle ◽  
Stress Axis ◽  
Flow Rule ◽  
Finite Limit ◽  
Confining Stress ◽  
Pressure Sensitive

Abstract After giving a complete analytical solution for the strain softening model associated to Mohr-Coulomb non associated elasto-plastic flow rule (MC-model), the paper demonstrates that this rheology possesses a finite limit load which allows solving for strength drop as a boundary value problem. The MC-model produces a non-dimensional strength drop, which depends on three parameters: the orientation of the shear band versus the least principal stress axis outside the band α0, the peak friction angle φ and the dilatation angle Ψ. The maximum reduction of strength obtained with that strain-softening model is on the order of the confining stress p0. For this weakest regime, the effective friction of the shear band drops from μini = 0.85 at peak to μss = 0.64 at the end of the softening phase. In this model, which considers thick shear bands, the weakest regime is not obtained for an orientation corresponding to the exact Coulomb orientation. Instead, the orientation of the weakest shear zone systematically deviates from the coulomb orientation by an angle, which rises with its internal friction angle. The characteristic shear strain needed to achieve steady state is quantified semi analytically and in the range of parameters valid for Earth, this strain is found to be of the order of 7–8%. These numbers are typical of what is observed in the laboratory, which give us confidence on that MC-model is a good and probably the simplest model to localize strain in numerical codes aimed at modeling the brittle part of the Earth.

Mechanical Properties and Stress-Strain Behaviour of Binary and Ternary Composites Based on Polyolefins and Vegetable Fillers

2017 ◽  
Vol 265 ◽  
pp. 221-226 ◽  
Author(s):  
E.E. Mastalygina ◽  
A.A. Popov
Keyword(s):  
Mechanical Properties ◽  
Filler Content ◽  
Low Density Polyethylene ◽  
Biological Degradation ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Composition And Structure ◽  
Study Results ◽  
Wide Range ◽  
Dimensional Parameters

Binary and ternary composites based on isotactic polypropylene and low-density polyethylene in a wide range of ratios without and with filler content have been investigated. Micron-scale vegetable cellulosic components initiating biological degradation have been used as fillers for polymeric composites. The analysis of stress-strain behaviour of the composites has shown a non-additive dependency of elongation and tensile strength at break on blends composition. Based on this study results the composition and structure of polymeric phase of binary and ternary composites, as well as dimensional parameters of filler particles have a significant impact on stress-strain behaviour of the materials. The main regularities determining materials mechanical properties have been discovered, that, in turn, could be used for predicting service behaviour of composites under investigation.

An Experimental Study on the Mechanical Properties of Soils of the Landslide Induced by Rainfall

2011 ◽  
Vol 90-93 ◽  
pp. 1303-1306
Author(s):  
Dong Heng Hao ◽  
Jian Feng Qi ◽  
Bin Wang ◽  
Shu Qin Zhao
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Internal Friction ◽  
Water Content ◽  
Strain Softening ◽  
Friction Angle ◽  
Mechanical Parameters ◽  
Strain Stress ◽  
Geotechnical Tests ◽  
Sliding Zone

Geotechnical tests are performed to study the strain-stress behavior and mechanical parameters by using the automatic KTG triaxial shear apparatus. This study shows that the strain softening phenomenon emerges after the peak values of strain-stress relations appear for the sliding-body soils, and that the strain-stress relations are in the sate of strain hardening all the time for the sliding-zone soils although the water content keeps sameness. The variation laws of cohesion and internal friction angle with water content are respectively consistent with an exponential function and linear relation.

High Strain Rate Mechanical Properties of SAC-Q Between -65°C and +200°C After Exposure to Isothermal Aging

2020 ◽  
Author(s):  
Pradeep Lall ◽  
Vishal Mehta ◽  
Jeff Suhling ◽  
Ken Blecker
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Isothermal Aging ◽  
High Strain ◽  
Strain Rates ◽  
Solder Alloys ◽  
Stress Strain ◽  
Wide Range ◽  
Operating Temperatures ◽  
Electronic Parts

Abstract In many industries, such as automotive, oil and gas, aerospace, medical technologies, electronic parts can often be exposed to high strain loads during shocks, vibrations and drop-impact conditions. Such electronic parts can often be subjected to extreme low and high temperatures ranging from −65°C to 200°C. Also, these electronic devices can be subjected to strain rates of 1 to 100 per second in the critical environment. Recently, many doped SAC solder alloys are being introduced in the electronic component including SAC-Q, SAC-R, Innolot. SAC-Q is made with addition of Bi in Sn-Ag-Cu composition. Mechanical characteristic results and data for lead-free solder alloys are extremely important for optimizing electronic package reliability, at high temperature storage and elevated strain rates. Furthermore, the mechanical properties of solder alloys can be changed significantly due to a thermal aging, which is causing modification of microstructure. Data for the SAC-Q solder alloy with a high temp aging and testing at extreme low to high operating temperatures are not available. SAC-Q material was tested and analyzed for this study at range of operating temperatures of −65°C to 200°C and at a strain rate up to 75 per second. After the specimens were manufactured and reflowed, specimens were stored at 100°C for the isothermal aging for up to 90 days, before tensile tests were carried out at different operating temperatures. For the wide range of strain rates and test temperatures, stress-strain curves are established. In addition, the measured experimental results and data were fitted to the Anand viscoplasticity model and the Anand constants were calculated by estimating the stress-strain behavior measured in the wide range of operating temperatures and strain rates.

scholarly journals Experimental study on the mechanical properties of Guiyang red clay considering the meso micro damage mechanism and stress path

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yanzhao Zhang ◽  
Shuangying Zuo ◽  
Rita Yi Man Li ◽  
Yunchuan Mo ◽  
Guosheng Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Soil Sample ◽  
Pore Water ◽  
Shear Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Strain Curve ◽  
Friction Angle ◽  
Red Clay ◽  
Stress Strain

Abstract This study investigated the macroscopic physical and mechanical properties of Guiyang red clay during surcharge loading, lateral excavation and lateral unloading with axial loading, and clarified the failure mechanism of microstructure before and after shear under different stress paths of CTC, RTC and TC. Consolidated undrained triaxial shear permeability, SEM scanning, XRF fluorescence spectrum analysis and XRD diffraction tests were conducted to simulate the actual engineering conditions. The stress–strain curve, shear strength, pore water pressure variation rule and macroscopic failure mode of soil samples under different stress paths were analysed. In addition, Image Pro Plus 6.0 and PCAS were used to study the relationship between the macro mechanical properties and micro microstructure failure under different stress paths. The stress–strain curves from CTC, RTC and TC in CU tests were different, with the peak values of shear stress under the three stress paths being P-increasing, equal P-path and P-decreasing path. Moreover, the internal friction angle and cohesion of the increasing P path were higher than those of equal P path and decreasing P path, hence, the influence of stress paths on the cohesion is greater than that of internal friction angle. The pore water pressure is strongly dependent on the stress path, and the variation characteristics of pore water pressure are consistent with the change in the law of the stress–strain curve. Under the same confining pressure in the P-increasing path, the shear failure zone runs through the whole soil sample, and the shear failure zone is significant, whereas under the condition of the P-reducing path, the shear failure angle of soil sample is about 65°, 55° and 45°, and in the equal P path, the soil sample is dominated by the confining pressure, with no obvious microcrack on the surface of the soil sample. The difference is that the distribution of pores in the path of increasing P and equal P is directional, and the anisotropy rate is small, while the distribution of pores in soil samples with shear failure and before shear is random and the anisotropy rate is high.

The Influence of Redundant Work When Drawing Rods Through Conical Dies

1968 ◽  
Vol 90 (2) ◽  
pp. 411-416 ◽  
Author(s):  
R. M. Caddell ◽  
A. G. Atkins
Keyword(s):  
Mechanical Properties ◽  
Strain Hardening ◽  
Stress Strain ◽  
Work Factor ◽  
Wide Range ◽  
Before And After

Values of the redundant work factor in rod drawing were determined experimentally for four metals over a wide range of variables; none of the metals were strain hardened prior to drawing. The method of superposition of stress-strain curves before and after drawing was used, and an expression for the redundant work factor was found to be related to the strain hardening characteristics of the metal being drawn. Use of this factor was made to predict certain mechanical properties of the drawn metals; these agreed quite well with the values measured experimentally.

scholarly journals Novel Ring Compression Test Method to Determine the Stress-strain Relations and Mechanical Preperties of Metallic Materials

2021 ◽  
Author(s):  
Guang-Zhao Han ◽  
lixun Cai ◽  
Chen Bao ◽  
Bo Liang ◽  
Yang Lv ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Test Method ◽  
Metallic Materials ◽  
Compression Tests ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Ring Compression ◽  
Wide Range

Abstract Although there are methods for testing the stress–strain relation and strength, which are the most fundamental and important properties of metallic materials, their application to small size specimens is limited. In this study, a new dimensionless elastoplastic load–displacement (EPLD-Ring) model for compressed metal rings with isotropy and constitutive power law is proposed to describe the relation between the geometric dimensions, Hollomon law parameters, load, and displacement based on energy density equivalence. Furthermore, a novel test method for the rings is developed to obtain the elastic modulus, stress–strain relation, yield strength, and tensile strength. The universality and accuracy of the model are verified within a wide range of imaginary materials via finite element analysis (FEA), and the results show that the stress–strain relations obtained with the model are more consistent with those inputted in the FEA software. Additionally, for seven metallic materials, a series of ring compression tests with various dimensions were performed. It was found that the stress–strain relations and mechanical properties predicted by the model are in agreement with the normal tensile test results. It is believed that the new method is reliable and effective for testing the mechanical properties of small size materials and tube components.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

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