A testing rig for cycling at high biaxial strains

1973 ◽  
Vol 8 (3) ◽  
pp. 168-175 ◽  
Author(s):  
J M H Andrews ◽  
E G Ellison
Keyword(s):  
High Strain ◽  
External Pressure ◽  
Multiaxial Fatigue ◽  
Axial Tension ◽  
Wide Range ◽  
Fatigue Data ◽  
Other Information ◽  
Tension And Compression ◽  
Tubular Specimens ◽  
Experimental Rig

There is a scarcity of multiaxial fatigue data available to designers especially in the high-strain régime. This is due in part of the complexity of the test equipment involved. A servo-hydraulic experimental rig has been developed for the application of biaxial high-strain reversed cycles to thin-walled tubular specimens, i.e. under axial tension and compression and internal and external pressure. It is capable of testing over a wide range of strain ratios and is reasonably versatile in that other information pertaining to buckling, Poisson's ratio, and criteria for yielding can be obtained.

Effect of multiaxial stresses on the fracture strength of silicon carbide

1969 ◽  
Vol 4 (2) ◽  
pp. 81-87 ◽  
Author(s):  
E K Priddle
Keyword(s):  
Silicon Carbide ◽  
Fracture Strength ◽  
Room Temperature ◽  
Fracture Behaviour ◽  
Axial Tension ◽  
Straight Line ◽  
Failure Envelopes ◽  
Tension And Compression ◽  
Failure Theories ◽  
Tubular Specimens

This work describes the fracture behaviour of silicon-carbide tubular specimens under multi-axial stresses at room temperature. A method of obtaining combinations of stresses in the form of torsion, hoop, axial tension, and compression is described and failure envelopes for silicon carbide are included from the data obtained. Failure theories are reviewed and the results from the work show that the available theories are inadequate to describe both the tension-tension and tension-compression quadrants. For practical purposes a straight-line relation can be used joining axial and hoop tensile strengths and the axial compression strength.

scholarly journals The elastic limit of metals exposed to tri-axial stress

1932 ◽  
Vol 137 (833) ◽  
pp. 559-574 ◽  
Keyword(s):  
Shear Stress ◽  
Axial Stress ◽  
Maximum Shear Stress ◽  
Internal Surface ◽  
External Pressure ◽  
Stress System ◽  
Axial Tension ◽  
Tension And Compression ◽  
Von Mises ◽  
Similar Kind

The numerous investigations which have been carried out since the opening of the present century into the elastic breakdown of metals have resulted in the formulation of several hypotheses concerning the conditions of stress and strain necessary for its occurrence. The methods generally employed in the investigations have consisted in the application of combinations of tension and compression with torsion, and of bending with torsion, to solid bars and thin tubes, and of tension and compression combined with internal and external pressure to thin tubes; so that the stress system produced in the metal was essentially bi-axial in character, the third principal stress being either very small or zero. The results of these experiments have given general support to the shear stress hypothesis of Guest, although with deviations which in some cases are not insignificant. Experiments employing a tri-axial stress system, in which the relation to each other of the component stresses could be varied, have been comparatively few in number. Tests by Turner on thick walled cylinders of mild steel exposed simultaneously to internal pressure and axial tension, were inconclusive, possibly owing to the irregularity of the tubes. Those by Cook and Robertson, also on thick-walled tubes of varying dimensions, showed a reasonably constant value of the maximum shear stress at the instant of elastic breakdown at the internal surface; this stress was, however, considerably higher than the shear stress observed in the uni-axial state of stress in a simple tensile test of the same material, a result confirmed in more recent tests of a similar kind by the author. The newer hypotheses of Haigh and of von Mises require an effect of this kind; but it has been suggested by the author that the observed effect may nevertheless be associated more directly with the non-uniform character of the stress distribution, rather than as an indication of the inapplicability of the hypothesis which regards failure as due to the existence of a critical value of the shear stress.

Methodology of studying the mechanical properties of composite materials (reinforced concrete)

2018 ◽  
Vol 84 (12) ◽  
pp. 61-67
Author(s):  
V. A. Eryshev
Keyword(s):  
Mechanical Properties ◽  
Reinforced Concrete ◽  
Experimental Studies ◽  
Analytical Relationship ◽  
Hardened Concrete ◽  
Deformation Model ◽  
Joint Work ◽  
Concrete Shrinkage ◽  
Axial Tension ◽  
Tension And Compression

The mechanical properties of a complex composite material formed by steel and hardened concrete, are studied. A technique of operative quality control of new credible concrete and reinforcement, both in laboratory and field conditions is developed for determination of the strength and strain characteristics of materials, as well as cohesion forces determining their joint operation under load. The design of the mobile unit is presented. The unit provides a possibility of changing the direction of loading and testing the reinforced element of the given shape both for tension and compression. Moreover, the nomenclature of testing equipment and the number of molds for manufacturing concrete samples substantially decrease. Using the values of forcing resulting in concrete cracking when the joint work of concrete and reinforcement is disrupted the values of the inherent stresses and strains attributed to the concrete shrinkage are determined. An analytical relationship between the forces and deformations of the reinforced concrete sample with central reinforcement is derived for axial tension and compression, with allowance for strains and stresses in the reinforcement and concrete resulted from concrete shrinkage. The results of experimental studies are presented, including tension diagrams and diagrams of developing axial deformations with an increase in the load under the central loading of the reinforced elements. A methodology of accounting for stresses and deformations resulted from concrete shrinkage is developed. The applicability of the derived analytical relationships between stresses and deformations on the material diagrams to calculations of the reinforced concrete structures in the framework of the deformation model is estimated.

scholarly journals Molecular survey of vector-borne diseases in two groups of domestic dogs from Lisbon, Portugal

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Ana Mafalda Dordio ◽  
Relja Beck ◽  
Telmo Nunes ◽  
Isabel Pereira da Fonseca ◽  
Jacinto Gomes
Keyword(s):  
Clinical Status ◽  
Molecular Methods ◽  
Hepatozoon Canis ◽  
Clinical Approach ◽  
Limited Information ◽  
Vector Borne Diseases ◽  
Wide Range ◽  
Other Information ◽  
Southern Portugal ◽  
Vector Borne

Abstract Background Canine vector-borne diseases (CVBDs) are caused by a wide range of pathogens transmitted by arthropods. They have been an issue of growing importance in recent years; however, there is limited information about the vector-borne pathogens circulating in Portugal. The aim of the present study was to detect canine vector-borne bacteria and protozoa of veterinary and zoonotic importance using molecular methods. Methods One hundred and forty-two dogs from Lisbon, southern Portugal, were tested: 48 dogs from a veterinary hospital clinically suspected of vector-borne diseases and 94 apparently healthy dogs from shelters. Anaplasma spp./Ehrlichia spp., Babesia/Theileria spp., Hepatozoon spp., and Mycoplasma spp. infections were detected by PCR from blood samples and examined under light microscopy. Other information including clinical status and diagnostic test results were collected for each animal. Results Infections were detected by PCR in 48 (33.80%) dogs. Single infections were found in 35 dogs (24.64%), and co-infections were found in 13 (9.15%) dogs. Twenty-nine (20.42%) dogs were positive for Hepatozoon spp., 15 (10.56%) for Mycoplasma spp., 11 (7.75%) for Anaplasma spp./Ehrlichia spp., and six (4.21%) for Babesia spp. DNA sequencing was used to identify Babesia vogeli (2.81%), Babesia canis (1.40%), Hepatozoon canis (20.42%), Mycoplasma haematoparvum (2.11%), Mycoplasma haemocanis (8.45%), Anaplasma platys (7.04%), and Ehrlichia canis (0.70%). Conclusions This is the first molecular identification of B. canis and M. haematoparvum in dogs from southern Portugal. This study highlights the importance of molecular methods to identify CVBD pathogens in endemic areas and helps to guide the clinical approach of veterinarians in practice.

Structural and Magneto-Electric Properties of Pulsed Laser Deposited Ferroelectric/Ferromagnetic Heterostructure

2009 ◽  
Vol 1199 ◽  
Author(s):  
Ricardo Martinez ◽  
Ashok Kumar ◽  
Ratnakar Palai ◽  
Ram S. Katiyar
Keyword(s):  
Elevated Temperatures ◽  
High Strain ◽  
Ferroelectric Properties ◽  
Pulsed Laser ◽  
Ferromagnetic Behavior ◽  
Asymmetric Behavior ◽  
Normal Behavior ◽  
Wide Range ◽  
Capacitance Voltage ◽  
Voltage Relationship

AbstractAsymmetric superlattices (SLs) with ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric Ba0.7Sr0.3TiO3 (BST) as constitutive layers were fabricated on conducting LaNiO3 (LNO) coated (001) oriented MgO substrates using pulsed laser deposition (PLD). The crystallinity, ferroelectric and magnetic properties of the SLs were studied over a wide range of temperatures and frequencies. The structure exhibited ferromagnetic behavior at 300K, and ferroelectric behavior over a range of temperatures between 100K and 300K. The dielectric response as a function of frequency obeys normal behavior below 300 K, whereas it follows Maxwell–Wagner model at elevated temperatures. The effect of ferromagnetic LSMO layers on ferroelectric properties of the SL indicated strong influence of the interfaces. The asymmetric behavior of ferroelectric loop and the capacitance-voltage relationship suggest development of a built field in the SLs due to high strain across the interfaces.

Tension and Compression Behavior of Pre-Stressed Steel Strands at High Strain Rate

2011 ◽  
Vol 82 ◽  
pp. 154-159 ◽  
Author(s):  
Anatoly M. Bragov ◽  
Ezio Cadoni ◽  
Alexandr Yu. Konstantinov ◽  
Andrey K. Lomunov
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Gauge Length ◽  
Hopkinson Pressure Bar ◽  
Dog Bone ◽  
Tension And Compression ◽  
Set Up

In this paper is described the mechanical characterization at high strain rate of the high strength steel usually adopted for strands. The experimental set-up used for high strain rates testing: in tension and compression was the Split Hopkinson Pressure Bar installed in the Laboratory of Dynamic Investigation of Materials in Nizhny Novgorod. The high strain rate data in tension was obtained with dog-bone shaped specimens of 3mm in diameter and 5mm of gauge length. The specimens were screwed between incident and transmitter bars. The specimens used in compression was a cylinder of 3mm in diameter and 5mm in length. The enhancement of the mechanical properties is quite limited compared the usual reinforcing steels.

An Experimental Evaluation for Four Multiaxial Fatigue Approaches

2014 ◽  
Vol 627 ◽  
pp. 425-428
Author(s):  
Dan Jin ◽  
Da Jiang Tian ◽  
Qi Zhou Wu ◽  
Wei Lin
Keyword(s):  
Low Cycle Fatigue ◽  
Multiaxial Fatigue ◽  
304 Stainless Steel ◽  
Normal Strain ◽  
Cycle Fatigue ◽  
Critical Plane ◽  
Maximum Shear Strain ◽  
Rainflow Cycle Counting ◽  
Tubular Specimens ◽  
Damage Rule

A series of tests for low cycle fatigue were conducted on the tubular specimens for 304 stainless steel under variable amplitude and irregular axial-torsional loading. Rainflow cycle counting and linear damage rule are used to calculate fatigue damage and four approaches, e.g. SWT(Smith-Watson-Topper), KBM(Kandil-Brown-Miller), FS(Fatemi-Socie), and LKN(Lee-Kim-Nam) approach are employed to predict the fatigue life. The maximum shear strain plane, the maximum normal strain plane, and the maximum damage plane are considered as the critical plane, respectively. The effects of the choice of the critical plane on previous approaches are discussed. It is shown that comparing with the maximum shear/normal strain approach, the predictions are improved by using the maximum damage plane approach, part nonproportional paths for SWT, AV and part nonproportional paths for KBM, TV paths for FS. But for LKN, the prediction results are nonconservative for some paths than that of the maximum shear/normal strain approach.

scholarly journals Microtubules soften due to cross-sectional flattening

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Edvin Memet ◽  
Feodor Hilitski ◽  
Margaret A Morris ◽  
Walter J Schwenger ◽  
Zvonimir Dogic ◽  
...  
Keyword(s):  
High Strain ◽  
Three Dimensional ◽  
Elastic Model ◽  
Softening Effect ◽  
Cross Sectional ◽  
Mechanical Compliance ◽  
Wide Range ◽  
Elastic Filament ◽  
New Interpretation ◽  
Effective Mechanical Properties

We use optical trapping to continuously bend an isolated microtubule while simultaneously measuring the applied force and the resulting filament strain, thus allowing us to determine its elastic properties over a wide range of applied strains. We find that, while in the low-strain regime, microtubules may be quantitatively described in terms of the classical Euler-Bernoulli elastic filament, above a critical strain they deviate from this simple elastic model, showing a softening response with increasing deformations. A three-dimensional thin-shell model, in which the increased mechanical compliance is caused by flattening and eventual buckling of the filament cross-section, captures this softening effect in the high strain regime and yields quantitative values of the effective mechanical properties of microtubules. Our results demonstrate that properties of microtubules are highly dependent on the magnitude of the applied strain and offer a new interpretation for the large variety in microtubule mechanical data measured by different methods.

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.

Uncertainty in Collapse Strength Prediction of Sandwich Pipelines

2021 ◽  
Author(s):  
U. Bhardwaj ◽  
A. P. Teixeira ◽  
C. Guedes Soares
Keyword(s):  
Probabilistic Models ◽  
Uncertainty Propagation ◽  
Simulation Method ◽  
External Pressure ◽  
Design Parameters ◽  
Collapse Strength ◽  
Parameters Uncertainty ◽  
Wide Range ◽  
Model Predictions ◽  
Strength Models

Abstract This paper assesses the uncertainty in the collapse strength of sandwich pipelines under external pressure predicted by various strength models in three categories based on interlayer adhesion conditions. First, the validity of the strength models is verified by comparing their predictions with sandwich pipeline collapse test data and the corresponding model uncertainty factors are derived. Then, a parametric analysis of deterministic collapse strength predictions by models is conducted, illustrating insights of models’ behaviour for a wide range of design configurations. Furthermore, the uncertainty among different model predictions is perceived at different configurations of outer and inner pipes and core thicknesses. A case study of a realistic sandwich pipeline is developed, and probabilistic models are defined to basic design parameters. Uncertainty propagation of models’ predictions is assessed by the Monte Carlo simulation method. Finally, the strength model predictions of sandwich pipelines are compared to that of an equivalent single walled pipe.

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