Papers by Author: Mihaela Amarandei

Abstract: This paper presents a finite element analysis regarding the stress distribution in a cemented Austin Moore type hip prosthesis. The 3-D model was obtained using a Roland PICZA 3-D laser scanner. The applied loads simulate the normal gait cycle. The prosthesis is made from stainless steel with a femoral head of 45mm diameter. The numerical analysis was performed using the ABAQUS code. The results showed that the stress level in the cement is sensitive to the femoral neck angle. Starting with a standard, 125° angle, and increasing the angle with up to 5°, the resulting stress can be reduced with more than 10%. The proposed angle increase produces a more uniform stress distribution in the cemented section, increasing the durability of the arthoplasty.

Abstract: The aim of this work is to investigate the potential of transient thermography in the nondestructive evaluation of structural defects of NECURON 1001 using the FLIR thermographic system. Necuron is a polyurethane material used for applications like: fixture and gauges, master and copy models, models with high mechanical stress, etc. Transient thermography is a thermographic method which implies the investigation of materials that are of a different (often higher) temperature than the ambient. The heat flow into the sample is altered in the presence of a subsurface defect or feature, creating a temperature contrast at the surface that is recorded by the infrared system. Results show that this method of evaluation can indicate, in necuron, defects of small sizes that can be overlooked in the manufacturing process. Also, it was shown that the transient thermography method presented can be an important tool in evaluating structural defects of materials.

Abstract: Nitinol (NiTi) is a biocompatible nickel titanium alloy widely used in medical applications and devices. In anterior cruciate ligament (ACL) reconstruction surgery of the knee, fine wires of NiTi are used because of its high elasticity and good memory shape behavior. In surgical procedures these wires are exposed to mechanical stress and high deformations. This paper presents the results of the tests performed on fine NiTi wires of 1.1 mm and 0.73 mm in diameter, exposed to tensile load, which frequently appears in orthopedic surgery. The tests were done at a temperature of 37o C, in order to observe the influence of tensile stress on the mechanical properties of NiTi. The obtained material properties are in good correlation with data from manufacturers. These results are useful in durability evaluation of fine NiTi wires utilized in surgical procedures.