Effect of the Strain Rate on the Twisting of Trabecular Bone from Women with Hip Fracture

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Ana C. Vale ◽  
Jennifer Faustino ◽  
Luís Reis ◽  
Ana Lopes ◽  
Bruno Vidal ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Hip Fracture ◽  
Shear Modulus ◽  
Strain Rate ◽  
Trabecular Bone ◽  
Axial Load ◽  
Angular Displacement ◽  
Maximum Shear Stress ◽  
Lower Limbs

As one of the major functions of bone is to provide structural support for the musculoskeletal system, it is important to evaluate its mechanical strength. Bones may be subjected to multiaxial stresses due to bone pathologies, accidental loads which may lead to hip, wrist fracture, or to a prosthetic joint replacement. Twist loading may lead to fractures, especially involving long bones from lower limbs. The aim of this work was to study the effect of the strain rate on the shear properties of trabecular bone samples from women with hip fracture (from 65 to 100 years). Cylindrical samples were core drilled from human femoral heads along the primary trabecular direction. The cylinder's ends were polished and embedded in blocks of polymeric material which fit the grips of the testing device. Deformation rates of 0.005, 0.01, 0.015, and 0.05 s−1 were applied. Twisting tests were conducted with or without an applied axial load of 500 N. From the torque-angular displacement curves, the shear stress–strain curves were obtained. The maximum shear strength and the shear modulus (i.e. the slope of the linear region) were determined. A large scatter of the results of the shear strength and the shear modulus was found, which is probably related to the heterogeneity of nonhealthy human bone samples. There is no significant effect of the strain rate on the maximum shear stress and the shear modulus, either in tests undertaken with or without the application of an axial load. The effect of strain rate on nonhealthy bone trabecular twisting properties did not follow the trend observed on the effect of strain rate in healthy bone, where an increase is detected.

Determining of Shear Modulus for the Samples Circular and Hollow Circular Cross-Section

2016 ◽  
Vol 862 ◽  
pp. 298-304
Author(s):  
Eva Labašová ◽  
Rastislav Ďuriš ◽  
Vladimír Labaš
Keyword(s):  
Shear Stress ◽  
Shear Modulus ◽  
Cross Section ◽  
Theoretical Basis ◽  
Maximum Shear Stress ◽  
Circular Cross Section ◽  
Static Method ◽  
Strength Theory ◽  
Modulus Maximum ◽  
System Quantum

The contribution is focused on estimating the shear modulus of the samples of circular and hollow circular sections by static method. The samples were loaded by simple torsion, individual sections were stressed by shear stress. Theoretical basis are determined by linear elasticity and strength theory and they define the relation between shear modulus, maximum shear stress and relative strains. Relative strains are determined by using measurement apparatus and measurement system Quantum X MX 840.

Stress distribution analysis of novel dental mini-implant designs to support overdenture prosthesis

2021 ◽  
Author(s):  
Mariana Lima da Costa Valente ◽  
Ana Paula Macedo ◽  
Andréa Reis
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Axial Load ◽  
Static Load ◽  
Maximum Shear Stress ◽  
Load Application ◽  
Distribution Analysis ◽  
Mini Implants ◽  
Photoelastic Analysis

This study aimed to test and compare two novel dental mini-implant designs to support overdentures with a commercial model, regarding the stress distribution, by photoelastic analysis. Three different mini-implant designs (Ø 2.0 mm × 10 mm) were tested: G1—experimental threaded (design with threads and 3 longitudinal and equidistant self-cutting chamfers), G2—experimental helical (design with 2 long self-cutting chamfers in the helical arrangement), and G3—Intra-Lock® System. After including the mini-implants in a photoelastic resin, they were subjected to a static load of 100 N under two situations: axial and inclined model (30°). The fringe orders (n), that represents the intensity of stresses were analyzed around the mini-implants body and quantified using Tardy's method that calculates the maximum shear stress (τ) value in each point selected. In axial models, less stress was observed in the cervical third mini-implants, mainly in G1 and G2. In inclined models (30°), higher stresses were generated on the opposite side of the load application, mainly in the cervical third of G2 and G3. All mini-implant models presented lower tensions in the cervical third compared with the middle and apical third. The new mini-implants tested (G1 and G2) showed lower stresses than the G3 in the cervical third under axial load, while loading in the inclined model generated greater stresses in the cervical of G2.

The Physical and Mechanic Properties of the Loess Landslide

2012 ◽  
Vol 446-449 ◽  
pp. 3003-3006
Author(s):  
Li Hua Li ◽  
Meng Dang ◽  
Heng Lin Xiao ◽  
Hui Ming Tang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Maximum Shear Stress ◽  
Friction Angle ◽  
Dry Density ◽  
Disaster Prevention ◽  
Loess Landslide ◽  
Landslide Disaster

The loess landslide in BaDong city, HuBei province China suffers great losses, which is an extremely typical landslide disaster. Variation in water level in the Yangtse River and rainfall has enormous influence on the loess landslide disaster. Some tests on loess have been done, which mainly include water content influence on shear strength of the loess, the relation between water content and dry density etc. The results have shown that When the water content average increasing with 3%, the cohesive strength reduces with 57%，49%，54% respectively and the internal friction angle average reduces 43%. The bigger the water content, the bigger the shear displacement at the same imposed load. When water content average increases with 3%, the corresponding maximum shear stress reduces with 50%, which may be in favor of loess landslide disaster prevention.

PHOTOELASTIC STUDY ON THE MECHANICAL PROPERTIES OF FRACTAL ROCK JOINTS

Fractals ◽  
1996 ◽  
Vol 04 (04) ◽  
pp. 521-531 ◽  
Author(s):  
HEPING XIE ◽  
WEIHONG XIE ◽  
PENG ZHAO
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Shear Strength ◽  
Fractal Dimension ◽  
Maximum Shear Stress ◽  
Fractal Dimensions ◽  
Rock Joints ◽  
Peak Shear Strength ◽  
Joint Roughness ◽  
Contact Points

In this paper, the fractal rock joints are manufactured on the photoelastic material plate. Based on the visualized photoelastic experiments, the mechanical properties of the fractal joints with different roughness (different fractal dimensions) are investigated under uniaxial and shear compression. The research results indicate that the joint roughness (the fractal dimension of the joints) significantly influences the peak shear strength, the position of the maximum shear stress, and the number of contact points.

Interpretation of undrained creep tests in terms of effective stresses

1995 ◽  
Vol 32 (2) ◽  
pp. 373-379 ◽  
Author(s):  
Thomas C. Sheahan
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Strain Rate ◽  
Creep Behavior ◽  
Creep Rupture ◽  
Peak Shear Stress ◽  
Stress Levels ◽  
Static Yield ◽  
Undrained Shear ◽  
Undrained Creep

The paper provides an effective stress-based interpretation technique for undrained creep behavior in cohesive soils. This technique could ultimately be used to predict whether a particular applied shear stress level will lead to failure or creep rupture. During the primary phase of undrained creep at constant shear stress, the soil's strain rate decreases, which in turn leads to a decrease in the undrained shear strength. However, it has been shown for a number of soils that a minimum undrained strength, or upper yield strength (suy), is eventually reached regardless of further strain rate decreases. It has been postulated that this phenomenon is part of a time-dependent behavior framework in which the yield locus shrinks with decreasing strain rate until some limiting surface, the static yield surface (SYS), is reached. Such a surface has been the basis for a number of constitutive models in which it represents the inviscid, or rate independent, behavior. The peak shear stress on the SYS corresponds to suy. Data from previous experimental programs are presented to show the existence of the surface and its role in undrained creep behavior. Undrained creep shear stress levels above suy lead to creep rupture on the failure envelope; stress levels below suy cause creep to the SYS, where the stress state apparently stabilizes without failure. The value of suy can be used in a number of analyses in creep susceptible soils, and the static yield condition can be used in the field to determine whether measured pore pressures are exceeding predicted nonrupture levels. A method is proposed for simple determination of the SYS using constant strain rate undrained shear tests. Key words : clays, consolidated-undrained tests, creep, rate effects, rheology, shear strength.

scholarly journals Effects of temperature and repeat layer spacing on mechanical properties of graphene/polycrystalline copper nanolaminated composites under shear loading

2021 ◽  
Vol 12 ◽  
pp. 863-877
Author(s):  
Chia-Wei Huang ◽  
Man-Ping Chang ◽  
Te-Hua Fang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Shear Stress ◽  
Shear Modulus ◽  
Maximum Shear Stress ◽  
Shear Loading ◽  
Polycrystalline Copper ◽  
Self Healing ◽  
Layer Spacing ◽  
Armchair Direction

In the present study, the characteristics of graphene/polycrystalline copper nanolaminated (GPCuNL) composites under shear loading are investigated by molecular dynamics simulations. The effects of different temperatures, graphene chirality, repeat layer spacing, and grain size on the mechanical properties, such as failure mechanism, dislocation, and shear modulus, are observed. The results indicate that as the temperature increases, the content of Shockley dislocations will increase and the maximum shear stress of the zigzag and armchair directions also decreases. The mechanical strength of the zigzag direction is more dependent on the temperature than that of the armchair direction. Moreover, self-healing occurs in the armchair direction, which causes the shear stress to increase after failure. Furthermore, the maximum shear stress and the shear strength of the composites decrease with an increase of the repeat layer spacing. Also, the shear modulus increases by increasing the grain size of copper.

scholarly journals Tensile and Shear Testing of Basalt Fiber Reinforced Polymer (BFRP) and Hybrid Basalt/Carbon Fiber Reinforced Polymer (HFRP) Bars

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5839
Author(s):  
Kostiantyn Protchenko ◽  
Fares Zayoud ◽  
Marek Urbański ◽  
Elżbieta Szmigiera
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Tensile Testing ◽  
Maximum Shear Stress ◽  
Fiber Reinforced Polymer ◽  
Strength Testing ◽  
Fiber Reinforced ◽  
Shear Testing ◽  
Reinforced Polymer ◽  
Average Maximum

The use of sustainable materials is a challenging issue for the construction industry; thus, Fiber Reinforced Polymers (FRP) is of interest to civil and structural engineers for their lightweight and high-strength properties. The paper describes the results of tensile and shear strength testing of Basalt FRP (BFRP) and Hybrid FRP (HFRP) bars. The combination of carbon fibers and basalt fibers leads to a more cost-efficient alternative to Carbon FRP (CFRP) and a more sustainable alternative to BFRP. The bars were subjected to both tensile and shear strength testing in order to investigate their structural behavior and find a correlation between the results. The results of the tests done on BFRP and HFRP bars showed that the mechanical properties of BFRP bars were lower than for HFRP bars. The maximum tensile strength obtained for a BFRP bar with a diameter of 10 mm was equal to approximately 1150 MPa, whereas for HFRP bars with a diameter of 8 mm, it was higher, approximately 1280 MPa. Additionally, better results were obtained for HFRP bars during shear testing; the average maximum shear stress was equal to 214 MPa, which was approximately 22% higher than the average maximum shear stress obtained for BFRP bars. However, HFRP bars exhibited the lowest shear strain of 57% that of BFRP bars. This confirms the effectiveness of using HFRP bars as a replacement for less rigid BFRP bars. It is worth mentioning that after obtaining these results, shear testing can be performed instead of tensile testing for future studies, which is less complicated and takes less time to prepare than tensile testing.

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