Experimental and finite element analyses of bone strains in the growing rat tibia induced by in vivo axial compression

2019 ◽  
Vol 94 ◽  
pp. 176-185 ◽  
Author(s):  
Tanvir Mustafy ◽  
Irène Londono ◽  
Isabelle Villemure
Keyword(s):  
Finite Element ◽  
Axial Compression ◽  
Finite Element Analyses ◽  
Bone Strains ◽  
Growing Rat ◽  
Rat Tibia

An Interlocking Ligamentous Spinal Disk Arthroplasty with Neural Network Infrastructure

2010 ◽  
Vol 7 ◽  
pp. 55-79 ◽  
Author(s):  
Philip Boughton ◽  
James Merhebi ◽  
C. Kim ◽  
G. Roger ◽  
Ashish D. Diwan ◽  
...  
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Axial Compression ◽  
Wire Array ◽  
Axial Strain ◽  
Compressive Strain ◽  
Niti Wire ◽  
Motion Segment ◽  
Flexion Extension

An elastomeric spinal disk prosthesis design (BioFI™) with vertebral interlocking anchors has been modified using an embedded TiNi wire array. Bioinert styrenic block copolymer (Kraton®) and polycarbonate urethane (Bionate®) thermoplastic elastomer (TPE) matrices were utilized. Fatigue resistant NiTi wire was pretreated to induce superelastic martensitic microstructure. Stent-like helical structures were produced for incorporation within homogenous TPE matrix. Composite prototypes were fabricated in a vacuum hot press using transfer moulding techniques. Implant prototypes were subject to axial compression using a BOSE ® ELF3400. The NiTi reinforced implants exhibited reduction in axial strain, compliance, and creep compared to TPE controls. The axial properties of the NiTi reinforced Bionate® BioFI™ implant best approximated those of a spinal disk followed by Kraton®-NiTi, Bionate® and Kraton® prototypes. An ovine lumbar segment biomechanical model was used to characterize the disk prosthesis prototypes. Specimens were subject to 7.5Nm pure moments in axial rotation, flexion-extension and lateral bending with a custom jig mounted on an Instron® 8874. The motion preserving ligamentous nature of this arthroplasty prototype was not inhibited by NiTi reinforcement. Joint stiffness for all prototypes was significantly less than the intact and discectomy controls. This was due to lack of vertebral anchor rigidity rather than BioFI™ motion segment matrix type or reinforcement. Implant stress profiles for axial compression and axial torsion conditions were obtained using finite element methods. The biomechanical testing and finite element modelling both support existing BioFI™ design specifications for higher modulus vertebral anchors, endplates and motion segment periphery with gradation to a low modulus core within the motion segment. This closer approximation of the native spinal disk form translates to improvements in prosthesis biomechanical fidelity and longevity. Axial compressive strain induced within a TiNi reinforced Kraton® BioFI™ was found to be linearly proportional to the NiTi helical coil electrical resistance. This neural network capability delivers opportunities to monitor and telemeterize in situ multiaxis joint structural performance and in vivo spine biomechanics.

BEHAVIOUR OF SILOS SUPPORTED ON DISCRETE BRACKETS

2002 ◽  
Vol 02 (01) ◽  
pp. 45-62 ◽  
Author(s):  
M. GILLIE ◽  
J. M. F. G. HOLST ◽  
M. MÜNCH ◽  
J. M. ROTTER
Keyword(s):  
Finite Element ◽  
Axial Compression ◽  
Failure Modes ◽  
Design Guidelines ◽  
Finite Element Analyses ◽  
Structural Behaviour ◽  
Stress Regime ◽  
Bending Stresses ◽  
Mechanism Of Failure ◽  
Design Guidance

The controlling design condition in thin metal silos is generally buckling under axial compression. This compression is often assumed to be uniform but in many practical cases several failure modes interact as a result of a rather more complex pattern of stresses. Small silos are often supported on several columns with local brackets attached to the sides of the shell. Failure occurs with an interaction between buckling and yielding under a stress regime involving a combination of membrane and bending stresses developed by the applied loads. This paper firstly reviews the literature relevant to bracket supported silos and exposes the limitations in the available design guidance. The results of a series of finite element analyses are then presented to describe the underlying structural behaviour. It is shown that material and geometric non-linearity both play an important role in the behaviour of discretely supported silos. It is also established that the degree of bracket eccentricity is an important factor in determining the mechanism of failure and the associated strength of the silo. Finally, comparison is made between the numerical results and existing design guidelines.

Local Buckling Behavior of X100 Linepipes

2003 ◽  
Author(s):  
Nobuhisa Suzuki ◽  
Ryuji Muraoka ◽  
Alan Glover ◽  
Joe Zhou ◽  
Masao Toyoda
Keyword(s):  
Finite Element ◽  
Axial Compression ◽  
Critical Strain ◽  
Axial Stress ◽  
Local Buckling ◽  
Bending Moment ◽  
Finite Element Analyses ◽  
Design Factor ◽  
Shell Elements ◽  
Buckling Behavior

Local buckling behavior of API 5L X100 grade linepipes subjected to axial compression and/or bending moment is discussed in this paper based on results obtained by finite element analyses. Yield-to-tensile strength (Y/T) ratio and design factor were taken into account in the finite element analyses in order to discuss their effects on the local buckling behavior. The local bucking behavior of such lower strength linepipes as X60 and X80 grade linepipes is also discussed for comparison. Two-dimensional solid elements and four-node shell elements were used for the finite element modeling of the linepipes subjected to axial compression and bending moment, respectively. The study has improved the understanding of local buckling behavior of the X100 grade linepipes and observed the following trends. When a linepipe is subjected to axial compression, the critical axial stress decreases with increasing design factor and Y/T ratio. However, the nominal critical strain increases with increasing design factor and decreasing Y/T ratio. When a linepipe is subjected to bending moment, the critical bending moment decreases with increasing design factor and Y/T ratio. Similarly, the nominal critical strain increases with increasing design factor. However, the nominal critical strain increases with decreasing Y/T ratio when the design factor is less than and equal to 0.6 and decreases with decreasing Y/T ratio when the design factor is equal to 0.8.

Design of flexure revolute joint based on compliance and stiffness ellipsoids

2021 ◽  
pp. 095441002110169
Author(s):  
Jing Zhang ◽  
Hong-wei Guo ◽  
Juan Wu ◽  
Zi-ming Kou ◽  
Anders Eriksson
Keyword(s):  
Finite Element ◽  
Single Point ◽  
Synthesis Method ◽  
Nonlinear Finite Element ◽  
Finite Element Analyses ◽  
Rotational Stiffness ◽  
Rotational Angle ◽  
Parameterized Model ◽  
Flexure Joints ◽  
Translational Stiffness

In view of the problems of low accuracy, small rotational angle, and large impact caused by flexure joints during the deployment process, an integrated flexure revolute (FR) joint for folding mechanisms was designed. The design was based on the method of compliance and stiffness ellipsoids, using a compliant dyad building block as its flexible unit. Using the single-point synthesis method, the parameterized model of the flexible unit was established to achieve a reasonable allocation of flexibility in different directions. Based on the single-parameter error analysis, two error models were established to evaluate the designed flexure joint. The rotational stiffness, the translational stiffness, and the maximum rotational angle of the joints were analyzed by nonlinear finite element analyses. The rotational angle of one joint can reach 25.5° in one direction. The rotational angle of the series FR joint can achieve 50° in one direction. Experiments on single and series flexure joints were carried out to verify the correctness of the design and analysis of the flexure joint.

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