Sami Aksoy

Evaluation of bone plate with low-stiffness material in terms of stress distribution

The aim of this study is to evaluate a newly developed bone plate with low-stiffness material in terms of stress distribution. In this numerical study, 3D finite element models of the bone plate with low-stiffness material and traditional bone plates made of stainless steel and Ti alloy have been developed by using the ANSYS software. Stress analyses have been carried out for all three models under the same loading and boundary conditions. Compressive stresses occurring in the intact portion of the bone (tibia) and at the fractured interface at different stages of bone healing have been investigated for all three types of bone-plate systems. The results obtained have been compared and presented in graphs. It has been seen that the bone plate with low-stiffness material offers less stress-shielding to the bone, providing a higher compressive stress at the fractured interface to induce accelerated healing in comparison with Ti alloy and stainless-steel bone plate. In addition, the effects of low-stiffness materials with different Youngs modulus on stress distribution at the fractured interface have been investigated in the newly developed bone-plate system. The results showed that when a certain value of Youngs modulus of low-stiffness material is exceeded, increase in stiffness of the bone plate does not occur to a large extent and stress distributions and micro-motions at the fractured interface do not change considerably.

An elastic/plastic solution for a thermoplastic composite cantilever beam loading by bending moment

Abstract In this study, an elastic/plastic stress analysis is carried out for a thermoplastic composite cantilever beam loaded by a bending moment at the free end. The composite beam is reinforced by woven steel fibers, at 0, 15, 30 and 45° orientation angles. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli–Navier hypotheses. It is found that the intensity of the residual stress component of σx is a maximum at the upper and lower surfaces. The composite material is assumed to be as hardening linearly. The Tsai–Hill theory is used as a yield criterion.

Elastic–plastic stress analysis of simply supported and clamped aluminum metal-matrix laminated plates with a hole

Abstract In this study, an elastic–plastic stress analysis is carried out on simply supported and clamped cross-ply and angle-ply aluminum metal-matrix composite laminated plates with a circular hole. Classical lamination theory with first-order shear deformation theory is used for small deformations. The expansion of the plastic region and residual stress components are obtained on the upper and lower surfaces of the plates by using the finite element method. They are loaded on the upper surface transversely. Loading is gradually increased from the yield point of the plate by 0.0001 MPa at each load step. Load step numbers are chosen as 400, 600 and 800.

Residual stress effects on fracture energies of cement-bone and cement-implant interfaces.

The effects of residual stresses, which are caused by the temperature difference arising after polymerisation of bone cement, on the fracture energies of cement bone and cement-implant interfaces have been examined by using both experimental and numerical works. Only fracture loads of the test specimen having interfacial cracks have been measured in the experimental stage. The values of fracture loads and temperature difference after polymerisation have been applied to finite element models of the test specimens to calculate critical J-integral values of these both interfaces in the numerical stage. In addition, fracture energies of bone and cement, have been obtained by experimentally, using three-point bending test method The results have shown that residual stresses can produce changes in the fracture energies of these bimaterial systems, especially in cement implant interface and J(Ic) values of interfaces are considerably smaller than the experimentally determined J(Ic) values of cement and bone.

The three-dimensional finite element analysis of fixed bridge restoration supported by the combination of teeth and osseointegrated implants.

This study investigated the designs of osseointegrated prostheses in cases of free-end partial edentulism using comparative stress interpreted with the three-dimensional finite element method. Three free-end fixed osseointegrated prostheses models with various connection designs (ie, rigidly connected to an abutment tooth and an implant, rigidly connected to an implant and two abutment teeth, and rigidly connected to an implant and three abut- ment teeth) were studied. The stress values of the three models loaded with vertical, buccolingual, and linguobuccal directions at 30° angled to vertical axis forces were analyzed. When the fixed partial denture was connected to the three natural abutment teeth and an implant, the lowest levels of stress in the bone were noted.

Elastic-plastic finite elements analysis of transient and residual stresses in ceramo-metal restorations

Transient and residual stresses occurring in partially fixed dental prostheses after the firing process can be calculated with elastic or elastic-plastic finite element analyses (FEA). In this study, firstly, the mechanical and thermal properties at various temperatures of the materials used in a porcelain fused metal (PFM) system were obtained by experimental and literature studies. The effects of viscoelastic and viscoplastic behaviours of the dental porcelain at the elevated temperatures were reflected onto its elastic properties. The equivalent heat transfer coefficients were determined experimentally by measuring temperatures and the results were supplied as input to the 3D finite elements analysis. It has been observed that the maximum stresses occur within a short time period after cooling begins and that stresses decrease during the cooling process and remain at a constant value at the end of cooling; these are the thermal residual stresses.

Elastic–Plastic Stress Analysis of Unidirectionally Reinforced Symmetric Thermoplastic Laminated Beams Loaded by Bending Moment:

Elastic–plastic stress analysis is carried out on steel fiber reinforced thermoplastic matrix laminated beams loaded by bending moment. The beam is composed of four orthotropic layers, perfectly bonded and symmetrically arranged with respect to the x-axis. The orientation angles are chosen as (90°/0°)s, (30°/30°)s, (45°/45°)s and (60°/60°)s. The composite material is assumed to be linearly hardening. x residual stress component is found to be highest at the upper and lower surfaces. However, when the applied bending moment is increased, the plastic region is further expanded towards middle plane from the upper and lower surfaces of the beam and so x residual stress component is found to be highest at the elastic and plastic boundaries. The plastic flow is obtained to be maximum at the upper and lower surfaces for (30°/30°)s orientation. The transverse displacement is obtained to be highest at the free end for (90°/0°)s orientation.

An Elastic–Plastic and Residual Stress Analysis of Symmetric Laminated Cantilever Beam Under a Bending Moment

An elastic–plastic stress analysis in symmetric woven steel fiber reinforced polyethylene thermoplastic matrix laminated cantilever beam under a bending moment is studied by using analytical method and the Bernoulli–Euler theory for small plastic deformations. The orientation of the plies is chosen as (0°)4, (15° / -15°)2, (30° / -30°)2 and (45° / -45°)2. The Tsai–Hill theory is used as a yield criterion. Elastic and plastic stresses are the highest at the upper and lower surfaces. The residual stress component of x is maximized at the upper and lower surfaces. However, when the plastic region is further expanded, it is the highest at the boundary of the elastic and plastic regions. The magnitude of the residual stress component of x is found to be the highest for (0°)4 orientations. The plastic flow is maximized at the upper and lower surfaces for (0°)4 orientations.