Dr Mohammad Reza Allazadeh,
Volume 9, Issue 3 (9-2012)
Abstract
Abstract: A combination of a finite element method (FEM) algorithm with ANSYS codes and post image processing of NDT ultrasonic images along with laboratory cooling experiments and microstructural analysis provide a guideline to determine the optimum cooling rate for any grade of steel in which the highest productivity can be achieved without any degradation of the cast steel products. The suggested FEM algorithm with ANSYS codes is introduced to develop a quasi real models to simulate quenching of as-cast steel with any cooling rate from any initial temperature below steel’s melting point. The algorithm builds a model which is capable to approximate the thermodynamic stresses generated by thermal strain and possible solid-solid phase transformation for as-cast steel with any chemical composition. The model is applicable for any casting geometry (slab, billet and bloom, bar, etc) and adaptable for any method of cooling (unidirectional or multidirectional). Cooling with any cooling agent can be simulated with the algorithm in an ideal case. The phase transformation of the steel in the algorithm can be controlled by Continuous Cooling Transformation (CCT) Diagram obtained from analytical calculation or real time-temperature-transformation experiments for the cast steel. A function for optimizing cooling rate is suggested.
Assist. Prof. Dr. Saad Mahmood Ali,
Volume 20, Issue 4 (12-2023)
Abstract
In the present work, development models of a new artificial human soft heart and artificial heart valves using nanocomposite materials and synthetics were designed, manufactured, and tested. The fabricated mechanical artificial heart valves were examined to determine the best service life for each type. The fatigue life results were implemented by using the transient repeated and continuously applied blood pressure on each produced value to simulate diastolic and systolic that occur in the natural heart at each pulse cycle. The obtained results showed that a 3D printing of a new generation soft artificial heart for a permanent replacement was implemented as an alternative to the high-cost available temporary implant mechanical hearts, which may exceed the price by tens and hundreds of thousands of dollars, with a working life of not more than five years. The obtained fatigue safety factors for the produced artificial valves using different materials and designs were decreased with the complexity of the movement of the moving parts of the valve. The highest rates were obtained when using the valves with flat, simple movement in one direction like the single-leaflet type valve, where all the used materials are suitable for the production of this type of valve. The highest obtained safety factor was reached (15). The lowest rates were recorded when using the highly flexible and strong PSN4 nanocomposite material for fabricating the mitral tri-leaflet valve (thick. = 1.0 mm) reached 1.91. This value decreases to 0.99 when using the same type and material of valve but with a thickness equal to 0.5 mm. It can be noted here that the only suitable for the manufacture of this artificial valve type is the nanocomposite polyetherimide/ silicone rubber with nano silica (PSN4), whereas the other used materials failed because the fatigue factor values are less than 1. The service life span of this material is about 9200 x 106 cycles, which is equivalent to about 290 years, followed by SIBSTAR 103 with a default age of 209.6 x 106 cycles or 9 years.
