Semih Benli

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.

The Effect of Preload on Failure Response of Glass-Epoxy Laminated Composite Bolted-Joints with Clearance:

In this study, the effect of preload moments on failure response of glass-epoxy laminated composite bolted-joints with bolt/hole clearance was investigated. To evaluate the effects of bolted-joint geometry and stacking sequence of laminated plates on the bearing strength and failure mode, parametric analyses were performed, experimentally. Two different geometrical parameters, edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D), were examined. For this reason, the E/D ratio was selected from 1 to 5, whereas the W/D ratio was chosen from 2 to 5. Besides, preload moments were applied as 0, 3 and 6 Nm. Due to the estimating material parameters effect, laminated plates were oriented as three different groups, [0°/0°/90°/90°]s, [45°/45°/—45°/—45°]s and [60°/60°/—60°/—60°]s, symmetrically. The experiments were also performed under a clearance for the diameters of the bolt and the circular hole for 5 and 6 mm, respectively. Experimental results showed that failure mode and bearing strength are strictly affected by the magnitude of preload moments. Additionally, if material and geometrical parameters of composite bolted-joints are changed, the failure response is completely influenced by this change.

Experimental Failure Analysis of Glass-Epoxy Laminated Composite Bolted-Joints with Clearance Under Preload

In this study, a failure analysis of glass-epoxy laminated composite bolted-joints with bolt/hole clearance under various torques was carried out. To estimate the effects of joint geometry and fiber orientation on the failure strength and failure mode, parametric studies were conducted experimentally. The two different geometrical parameters were the edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D), E/D ratio was selected from 1 to 5, and W/D ratio was chosen from 2 to 5. The bolt preload torque was also carried out as 0, 3, and 6 Nm. To investigate the material parameters effect, laminated plates were oriented as three different stacking sequences [90o]8, [45o]8, and [0o] 8. The experiments were carried out with a clearance between the diameters of the bolt and the circular hole of 5 and 6 mm, respectively. According to experimental results, failure mode and bearing strength are strongly influenced by both material parameters and geometrical parameters. Additionally, when a torque is applied to the bolted-joints, the failure mechanism is affected by its increasing values.

Determination of Mechanical Properties and Failure Pressure in Composite Cylinders

Abstract In this study, mechanical properties of cylindrical composite specimens were measured experimentally. Composite cylinders oriented at 0° C and 90° were manufactured by using the hand lay -up technique. The cylinders were loaded axially for measuring the axial tensile strength and compressive strengths. Some specimens were attached to a torsion machine for measuring shear strength and shear modulus. Thus, a close and true measuring was performed in the cylindrical specimens. A finite element solution was performed in closed ended composite cylinders under internal pressure and thermal loading. Thermal stresses occur at low and high temperatures with respect to the room temperature. For a true or close solution in composite cylinders, mechanical properties should be determined in cylindrical composite specimens.

Stress Analysis of Fiber-reinforced Maxillary Dentures Under Different Loadings

The aim of this study was to compare maxillary dentures having different reinforcing materials in terms of stress distribution under concentrated forces applied to anterior and posterior regions. For this purpose, stress analyses of finite element models of 3 mm thick maxillary denture-bone systems were performed by using ANSYS software. First, concentrated forces making various angles, such as 0°, 15°, 30°, 45°, 60°, 75°, and 90°, with horizontal axis were applied to the anterior incisor and the posterior molar tooth regions of a maxillary denture without reinforcement material. The results show that the highest stress in critical zones occur at 75° and 45° angles, under loadings of 150 N to molar and 75 N to incisor region, respectively. Secondly, four different reinforcing materials including unidirectional and woven glass fibers, unidirectional carbon fibers, and alloyed chrome—cobalt fibers were placed in the denture in two different positions. Under vertical loadings, the σx stress distributions occurring in critical zones were investigated. It is concluded from the stress analyses that use of Cr—Co as a reinforcing material at the center of the maxillary denture gives the best results in terms of stress distribution and strength.

Sea Water Effect on Failure Behaviour of Mechanically Fastened Composites

Abstract In this study, sea water effect on failure behaviour was investigated for mechanically fastened composites that are oriented as [0/90/45/-60]s. The laminated composite specimens were fastened with two serial fasteners and were tested under non-immersed and immersed conditions, i. e. in sea water for 200 days. The experiments were carried out according to D 5229/D 5229M standard test method for evaluation of moisture absorption properties and equilibrium conditioning of polymer matrix composite materials. The results point out that the immersion into sea water of the composite specimens can cause a decrease in failure loads of both, pinned and bolted joints, particularly.

Elastic-Plastic and Residual Stresses in Clamped Thermoplastic Composite Laminates Loaded Transversely

In this study, an elastic-plastic stress analysis was carried out in woven steel fibers- thermoplastic clamped composite laminates. The stacking sequences were chosen as [0/0]2, [15/-15]2, [30/-30]2 and [45/-45]2 for woven steel fibers – thermoplastic composites plates. The layers were chosen for symmetric and antisymmetric cases. The finite element solution was performed by using the ANSYS software. Solid 186 element was utilized in the solution. Normal stress components at the clamped edges were found to be higher than that at the mid point of the laminated plates. Normal stresses are tensile at the mid point of the clamped edges and compressive at the mid point of the laminated plates. Then, the residual stress components were calculated in the critical points of the composite laminates.

Comparison of Stress Distributions of Dental Woven and Unidirectional Fiber-Reinforced Composite Crowns Under Different Loadings

The aim of this numerical study was to investigate and compare the stresses occurring in dental woven and unidirectional experimental fiber-reinforced composite (FRC) crowns under different thermal and singular force loading conditions. For this reason, finite element models of FRC crown and tooth systems were performed by using the ANSYS program. Stress analyses of the models were carried out under thermal loading conditions heated from 37 to 55°C, cooled from 37 to 5°C, and 450 N singular force loading conditions at different angles. The results indicated that high stresses occurred in both woven and unidirectional FRC crowns under horizontal loadings because of bending moment. Thermal stresses exhibited small values that did not cause any damage. It can also be concluded that since the stress component of σ z in the woven type FRC was smaller than that of unidirectional type FRC, use of the woven FRC might be beneficial in comparison with the unidirectional composite.