scholarly journals The Analytical Approach to Evaluate the Load-Displacement Relationship of Rock Bolts

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Jianhang Chen ◽  
Shengli Yang ◽  
Hongbao Zhao ◽  
Junwen Zhang ◽  
Fulian He ◽  
...  
Keyword(s):  
Shear Strength ◽  
Young’S Modulus ◽  
Analytical Model ◽  
Load Transfer ◽  
Young's Modulus ◽  
Peak Load ◽  
Rock Bolts ◽  
Residual Shear Strength ◽  
Grouted Rock Bolts ◽  
Elastic Softening

Fully grouted rock bolts are widely used in civil engineering and mining engineering, playing a significant role in keeping the stability and safety of excavations. In this paper, the load transfer mechanism of fully grouted rock bolts was studied with an analytical model. A trilinear model was used to depict the bond-slip behaviour of the bolt/grout interface. The displacement of the confining medium was involved in this analytical model. Then, the shear stress propagation along the bolt/grout interface was analysed in the elastic, elastic-softening, elastic-softening-debonding, softening-debonding, and debonding stages. Experimental pull-out tests were used to validate this analytical model. There was a good correlation between experimental and analytical results. A parametric study was conducted to evaluate the influence of Young’s modulus of the confining medium, the shear strength of the bolt/grout interface, and the residual shear strength of the bolt/grout interface on the load transfer performance of rock bolts. The results show that increasing Young’s modulus of the confining medium was beneficial for improving the load transfer performance of rock bolts. However, once Young’s modulus of the confining medium was beyond a critical limit, it had marginal effect on the peak load of rock bolts. Furthermore, increasing the shear strength of the bolt/grout interface and the residual shear strength of the bolt/grout interface led to rising of the peak load of rock bolts. However, compared with the residual shear strength of the bolt/grout interface, increasing the shear strength of the bolt/grout interface had more apparent effect in improving the peak load of rock bolts.

scholarly journals Finite Element Analysis of Tibial Bone-Implant Load Transfer and Bone Strains with a Modern Fixed-bearing Total Ankle Replacement

2018 ◽  
Vol 3 (3) ◽  
pp. 2473011418S0011
Author(s):  
Daniel Sturnick ◽  
Guilherme Saito ◽  
Jonathan Deland ◽  
Constantine Demetracopoulos ◽  
Xiang Chen ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Tibial Component ◽  
Load Transfer ◽  
Young's Modulus ◽  
Stress Shielding ◽  
Poisson's Ratio ◽  
Bone Implant ◽  
Tibial Tray ◽  
Tibial Bone

Category: Ankle Arthritis Introduction/Purpose: Loosening of the tibial component is the primary failure mode in total ankle arthroplasty (TAA). The mechanics of the tibial component loosening has not been fully elucidated. Clinically observed radiolucency and cyst formation in the periprosthetic bone may be associated with unfavorable load sharing at and adjacent to the tibial bone-implant interface contributory to implant loosening. However, no study has fully investigated the load transfer from the tibial component to the bone under multiaxial loads in the ankle. The objective of this study was to utilize subject-specific finite element (FE) models to investigate the load transfer through tibial bone-implant interface, as well as periprosthetic bone strains under simulated multiaxial loads. Methods: Bone-implant FE models were developed from CT datasets of three cadaveric specimens that underwent TAA using a modern fixed-bearing tibial implant (a cobalt-chrome tray with a polyethylene bearing, Salto Talaris, Integra LifeSciences). Implant placement was estimated from the post-operative CT scans. Bone was modeled as isotropic elastic material with inhomogeneous Young’s modulus (determined from CT Hounsfield units) and a uniform Poisson’s ratio of 0.3. The tibial tray (Young’s modulus: 200,000 MPa, Poisson’s ratio: 0.3) and the polyethylene bearing (Young’s modulus: 600 MPa, Poisson’s ratio: 0.4) were modeled as isotropic elastic. A 100-N compressive force, a 300-N anterior force, and a 3-Nm moment were applied to two literature based loading regions on the surface of the polyethylene bearing. The proximal tibia was fixed in all directions. The bone-implant contact was modeled as frictional with a coefficient of 0.7, whereas the polyethylene bearing was bonded to the tray. Results: Along the long axis of the tibia, load was transferred to the bone primarily through the flat bone-contacting base of the tibial tray and the cylindrical top of the keel, little amount of load was transferred to the bone between those two features (Fig. 1A). Low strain was observed in bone regions medial and lateral to the keel of the tibial tray, where bone cysts were often observed clinically (Fig. 1A). On average, approximated 70% of load was transferred through the anterior aspect of the tibial tray at the flat bone-contacting base, which corresponded to the relatively high bone strain adjacent to the implant edge in the anterior bone-implant interface (Fig. 1B). Conclusion: Our results demonstrated a two-step load transfer pattern along the long axis of the tibia, revealing regions with low bone strain peripheral to the keel indicative to stress shielding. Those regions were consistent with the locations of bone cysts observed clinically, which may be explained by the stress shielding associated remodeling of bone. These findings could also describe the mechanism of implant loosening and failure. Future studies may use our model to simulate more loading scenarios, as well as different implant placement and design, to identify means to optimize load transfer to the bone and prevent stress shielding.

scholarly journals Load transfer of nanocomposite film on aluminum substrate

2018 ◽  
Vol 16 (1_suppl) ◽  
pp. 10-16
Author(s):  
Shiuh-Chuan Her ◽  
Pao-Chu Chien
Keyword(s):  
Young’S Modulus ◽  
Nanocomposite Film ◽  
Load Transfer ◽  
Young's Modulus ◽  
Tensile Load ◽  
Beam Theory ◽  
Aluminum Substrate ◽  
Nanocomposite Films ◽  
Euler Beam ◽  
Load Carrying

Introduction: Nanocomposite films have attracted much attention in recent years. Depending on the composition of the film and fabrication method, a large range of applications has been employed for nanocomposite films. Method: In this study, nanocomposite films reinforced with multi-walled carbon nanotubes (MWCNTs) were deposited on the aluminum substrate through hot press processing. A shear lag model and Euler beam theory were employed to evaluate the stress distribution and load carrying capability of the nanocomposite film subjected to tensile load and bending moment. Results: The influence of MWCNT on the Young’s modulus and load carrying capability of the nanocomposite film was investigated through a parametric study. The theoretical predictions were verified by comparison with experimental tests. A close agreement with difference less than 6% was achieved between the theoretical prediction and experimental measurements. Conclusions: The Young’s modulus and load transfer of the nanocomposite film reinforced with MWCNTs increases with the increase of the MWCNT loading. Compared to the neat epoxy film, nanocomposite film with 1 wt % of MWCNT exhibits an increase of 20% in both the Young’s modulus and load carrying capability.

Response of Honeycombs Subjected to In-Plane Shear

2016 ◽  
Vol 83 (6) ◽  
Author(s):  
Youming Chen ◽  
Raj Das ◽  
Mark Battley
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Young’S Modulus ◽  
Cell Walls ◽  
Young's Modulus ◽  
Constitutive Relations ◽  
Length Ratio ◽  
Plane Shear ◽  
Base Materials ◽  
Vertical Cell

Study on the response of honeycombs subjected to in-plane shear helps establish the constitutive relations for honeycombs and shed light on the mechanics of cellular materials. The present study explores the nonlinear elastic response of honeycombs under in-plane shear by analyzing the large deflection of cell walls in a unit cell. Governing equations are established which relate the macroscopic response of honeycombs to the deflection of cell walls. Solving these equations, the behavior of regular honeycombs under in-plane shear along horizontal (X) and vertical (Y) directions was investigated. It is found that the response of regular honeycombs under in-plane shear depends on the nondimensional shear stress which is a parameter combining the thickness-to-length ratio of cell walls, the Young's modulus of base materials, and macroscopic shear stress. Lateral shrinking is a distinctive characteristic for honeycombs under in-plane shear, which should be taken into account when establishing constitutive relations and performing simple shear experiments. Expressions for predicting the shear strength of honeycombs are formulated in this paper. It is noted that the normalized shear strength of regular honeycombs depends on two ratios: the thickness-to-length ratio of cell walls and the ratio of Young's modulus to yield strength of base materials, and the former has a dominant effect. By comparing honeycombs with cell walls of uniform thickness against honeycombs with vertical cell walls of double thickness, it is found that doubling the thickness of vertical cell walls of honeycombs increases their shear strength along horizontal (X) direction nearly twice, but does not improve the shear strength that much along the vertical (Y) direction.

Analytical Modeling of Top Roller Position for Multiple Pass (3-Roller) Cylindrical Forming of Plates

2006 ◽  
Author(s):  
A. H. Gandhi ◽  
H. K. Raval
Keyword(s):  
Young’S Modulus ◽  
Analytical Model ◽  
Young's Modulus ◽  
Material Behavior ◽  
Analytical Models ◽  
Radius Of Curvature ◽  
Single Pass ◽  
Multiple Pass ◽  
Efficient Performance ◽  
Constant E

As forming of the double or multiple curvature surfaces, includes roller forming at least once in the sequential process; its efficient performance is of great importance for controlling the final product dimensions. Most efficient and economical way to produce the cylinder is to roll the plate through the roller in single pass. Literature review revels that, most of the reported analytical models for the prediction of springback were developed with the assumption of zero initial strain. However, in practice multiple pass bending is recommended to work within the power limitation of the machine and to improve the accuracy of the final product. An attempt is made to develop the analytical model for estimation of top roller position as a function of desired radius of curvature, for multiple pass 3-roller forming of cylinders, considering real material behavior. Due to the change of Young's modulus of elasticity (E) under deformation, the springback is larger than the springback calculated with constant E. Developed analytical model was modified to include the effect of change of Young's modulus during the deformation. Developed multiple pass analytical models were compared with the single pass analytical model and experiments (on pyramid type 3-roller bending machine).

scholarly journals Finite Element Analysis of the Stress Field in Peri-Implant Bone: A Parametric Study of Influencing Parameters and Their Interactions for Multi-Objective Optimization

2020 ◽  
Vol 10 (17) ◽  
pp. 5973
Author(s):  
Paul Didier ◽  
Boris Piotrowski ◽  
Gael Le Coz ◽  
David Joseph ◽  
Pierre Bravetti ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Young’S Modulus ◽  
Load Transfer ◽  
Young's Modulus ◽  
Element Model ◽  
Implant Design ◽  
Main Effects ◽  
Full Factorial ◽  
Surrounding Bone

The present work proposes a parametric finite element model of the general case of a single loaded dental implant. The objective is to estimate and quantify the main effects of several parameters on stress distribution and load transfer between a loaded dental implant and its surrounding bone. The interactions between them are particularly investigated. Seven parameters (implant design and material) were considered as input variables to build the parametric finite element model: the implant diameter, length, taper and angle of inclination, Young’s modulus, the thickness of the cortical bone and Young’s modulus of the cancellous bone. All parameter combinations were tested with a full factorial design for a total of 512 models. Two biomechanical responses were identified to highlight the main effects of the full factorial design and first-order interaction between parameters: peri-implant bone stress and load transfer between bones and implants. The description of the two responses using the identified coefficients then makes it possible to optimize the implant configuration in a case study with type IV. The influence of the seven considered parameters was quantified, and objective information was given to support surgeon choices for implant design and placement. The implant diameter and Young’s modulus and the cortical thickness were the most influential parameters on the two responses. The importance of a low Young’s modulus alloy was highlighted to reduce the stress shielding between implants and the surrounding bone. This method allows obtaining optimized configurations for several case studies with a custom-made design implant.

scholarly journals Mechanical Behavior of Melt-Mixed 3D Hierarchical Graphene/Polypropylene Nanocomposites

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1309
Author(s):  
Karolina Gaska ◽  
Georgia C. Manika ◽  
Thomas Gkourmpis ◽  
Davide Tranchida ◽  
Antonis Gitsas ◽  
...  
Keyword(s):  
Impact Strength ◽  
Mechanical Behavior ◽  
Young’S Modulus ◽  
Load Transfer ◽  
Young's Modulus ◽  
Superposition Principle ◽  
Tensile Tests ◽  
Graphene Nanocomposites ◽  
Polypropylene Nanocomposites ◽  
Static Tensile

The mechanical properties of novel low percolation melt-mixed 3D hierarchical graphene/polypropylene nanocomposites are analyzed in this study. The analysis spans a broad range of techniques and time scales, from impact to tensile, dynamic mechanical behavior, and creep. The applicability of the time–temperature superposition principle and its limitations in the construction of the master curve for the isotactic polypropylene (iPP)-based graphene nanocomposites has been verified and presented. The Williams–Landel–Ferry method has been used to evaluate the dynamics and also Cole–Cole curves were presented to verify the thermorheological character of the nanocomposites. Short term (quasi-static) tensile tests, creep, and impact strength measurements were used to evaluate the load transfer efficiency. A significant increase of Young’s modulus with increasing filler content indicates reasonably good dispersion and adhesion between the iPP and the filler. The Young’s modulus results were compared with predicted modulus values using Halpin–Tsai model. An increase in brittleness resulting in lower impact strength values has also been recorded.

scholarly journals Multi-Material Additive Manufacturing of Sustainable Innovative Materials and Structures

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 62 ◽  
Author(s):  
Rupinder Singh ◽  
Ranvijay Kumar ◽  
Ilenia Farina ◽  
Francesco Colangelo ◽  
Luciano Feo ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Additive Manufacturing ◽  
Glass Transition Temperature ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Peak Load ◽  
Fused Deposition Modelling ◽  
Fused Deposition ◽  
Innovative Materials

This paper highlights the multi-material additive manufacturing (AM) route for manufacturing of innovative materials and structures. Three different recycled thermoplastics, namely acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and high impact polystyrene (HIPS) (with different Young’s modulus, glass transition temperature, rheological properties), have been selected (as a case study) for multi-material AM. The functional prototypes have been printed on fused deposition modelling (FDM) setup as tensile specimens (as per ASTM D638 type-IV standard) with different combinations of top, middle, and bottom layers (of ABS/PLA/HIPS), at different printing speed and infill percentage density. The specimens were subjected to thermal (glass transition temperature and heat capacity) and mechanical testing (peak load, peak strength, peak elongation, percentage elongation at peak, and Young’s modulus) to ascertain their suitability in load-bearing structures, and the fabrication of functional prototypes of mechanical meta-materials. The results have been supported by photomicrographs to observe the microstructure of the analyzed multi-materials.

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