Abstract
Drilling is one of the most common processes involved in different cutting operations and may affect the mechanical properties of the workpiece by creating residual stresses around the opened hole and highly stressed on the newly formed surface. Nevertheless, when it comes to the living tissues, drilling assumes more attention to guarantee a non-invasive procedure. Drilling of bone is common in orthopaedic surgical process, to produce a hole to screw insertion to fix the fractured members for immobilization, or even in dental implant interventions. This work describes a conventional drilling process performed on solid rigid polyurethane foams blocks with similar mechanical properties to the human bone. A dynamic and numerical study was conducted to evaluate the use of different drill diameters (4, 5 and 6mm) on the stresses generated during the process. Different simulations using an explicit dynamic program were performed to assess the level of stresses and the damage effect on the polyurethane foam structure. This program is based on the finite element method and incorporates the dynamic characteristics involved in the drilling process. The main objective of this study is to verify the combination between some drill parameters, that reduce the mechanical damage produced by high stress level during bone drilling. The results permit to assess the influence of the drill bit diameter using a constant feed-rate (75mm/min) and drill speed (600rpm). For these conditions, results show that the smaller drill bit diameter leads to a decrease in the stress level in the foam material during the process. Article DOI: https://dx.doi.org/10.20319/mijst.2017.33.112 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
Highlights
Several studies about drilling process in different materials have been published (Fernandes, Fonseca, Natal, Vaz, & Dias, 2015).Shaping operations through which excess material is removed could be categorized in different processes types: conventional machining, abrasive processes and nontraditional processes.Drilling is one of the most complex machining process, due the combination of cutting and extrusion of material
2.1 Experimental Results For all measured strain values, during the drilling process and with different drill tools, it was possible to identify the effect in the average of the stress level at the end of 30 mm depth perforation
An order 2 polynomial trendline illustrate the relationship between the drill bit diameter and the maximum stress obtained in the polyurethane foam material
Summary
Several studies about drilling process in different materials have been published (Fernandes, Fonseca, Natal, Vaz, & Dias, 2015).Shaping operations through which excess material is removed could be categorized in different processes types: conventional machining (turning, drilling, milling or other operations), abrasive processes (grinding or other) and nontraditional processes (mechanical energy, electrochemical, thermal and chemical machining).Drilling is one of the most complex machining process, due the combination of cutting and extrusion of material. Several studies about drilling process in different materials have been published (Fernandes, Fonseca, Natal, Vaz, & Dias, 2015). Conventional machining in drilling process of different materials use a controlled drilling parameters. In case of human bone surgeries, the surgeon controls manually the drilling parameters, such as the feed-rate due the imposed load control by hand (Fernandes, Fonseca, & Natal, 2017), (Fernandes, Fonseca, & Natal, 2015). Several works have been published in the biomechanical area using experimental, numerical and analytical procedures. The main objective is to study the influence of different parameters in guarantee of the health and quality of human people. Valeeprakhon & Eua-Anant, 2015, published one work focused on experimental results to count red blood cell using a new algorithm based on the displacement ratio criteria. 2016 used a numerical simulation based on finite volume method to carried out on physiological pulsatile flow through a rigid arterial wall with the objective to study the atherosclerosis, as a cardiovascular disease
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