Applied Biomedical Engineering AMME4981 Lecture 1 Introduction to Computational Modelling and its Application in Biomedical Engineering http://www.aeromech.usyd.edu.au/people/academic/qingli/AMME4981.htm Course Web
Course Outline - Learning Objectives
Understanding of biomedical engineering design ;
Skills of finite element analysis and application of software (Ansys) ;
Overview of modelling techniques in biomedical engineering ;
Project-based-learning, approach to development of biomedical design and optimisation .
Course Outline - Syllabus Seminar 2 and Final Report 13 Quiz (one hour paper and 1.5 hour Ansys) 12 Clinical applications of modelling 11 Modelling of damage, fracture and healing 10 Bone remodelling and simulation 9 Seminar 1 (literature review and preliminary studies) 8 Finite element modelling issues 7 Fundamentals of finite element method 6 Solid modelling and design optimisation 5 Introduction to CT/MRI and image processing 4 Constitutive models of biomaterials 3 Biomechanical modelling of musculoskeletal systems 2 Introduction to computational modelling and software in biomedical engineering 1
Course Outline - Assessment Attendance will be counted in individual project marks of 50% Participation Mark Seminar 1 – Week 8 ( 1 0%) Seminar 2 – Week 13 ( 2 0%) Group final report – Week 13 (20%) Seminar s 1 hour paper ( 10 %) and 1.5 hour in Ansys (10%) – Week 12 (total: 20%) Quiz Assignment 1 – Week 4 (10%) Assignment 2 – Week 8 (10%) Assignment 3 – Week 13 ( 1 0%) Assignment s
Project Based Learning Tentative Project: Hip Replacement Design (To be finalized by week 2) Metal, Polyethylene, Ceramic Implantation Hip replacement is a medical procedure in which the hip joint is replaced by a synthetic implant. It is the most successful, cheapest and safest form of joint replacement surgery.
Design Related Issues
Minimize stress shielding
Stimulate positive bone remodelling
CT or MRI Scanning
Acquisition of computer tomographic (CT) data of the femur,
Computational Solid Modelling
Geometrical modelling of the femur and design of anatomical prosthesis in a computer-aided design (CAD) system,
Finite Element Modelling and Analysing
Verification of the designed prosthesis in the finite element method (FEM) system –– including bone remodeling prediction .
Objectives Three typical steps
Reverse Engineering “ Direct” Engineering Design Computer Model Fabrication Product “ Reverse” Engineering Product (Bone) CT Data Computer Model
Reverse Engineering – Application Slice Model of the prosthesis stem fitted to the medullary canal. Differences in cross-sections of the three designs of the prosthesis stems: Solid Model
CT-based Modelling – Procedure Segmentation of CT images Stack of sectional curves NURBs Surface fitting Solid Model Step 1 selection of CT images that represent the desired anatomy of the bone, Step 2 segmentation of the desired object(s) through detection of the contours by determining the value of Hounsfield number CT at points Step 3 creation of sectional curves along the CT points Step 4 creation of surface model from the curves Step 5 generation of the solid model of the femur
Review on Commercial Software – ScanFE/ScanIP Simpleware ( http://www.simpleware.com/index.php ) – MRI and CT (US$15K) ScanIP – image processing tools to assist the user in visualising and segmenting regions of interest from any volumetric 3D data (e.g. MRI, CT, MicroCT). Segmented images can be exported as STL files for CAD analysis and RP manufacturing or imported directly into leading commercial finite element packages. ScanFE – generates volume and/or surface meshes, contact surfaces and material properties from segmented data. Software Export – ABAQUS, ANSYS Segmentation Hip meshed with ScanFE Analysis
Review on Commercial Software – Mimics Mimics – http://www.materialise.com/materialise/view/en/65854-Homepage.html CT, MRI images Allow segmentation, solid modelling and FEA or export MedCAD Module – a bridge between medical imaging (CT, MRI) and CAD. Allow a two-way interface from the imaging system to the CAD system and vice versa . FEA – Build-in FEA module: Remesh the 3D object with the Mimics Remesher Export Software – Patran neutral, Ansys or Abaqus (surface mesh) Material Assignment – Continuious
Review on Commercial Software – Amira and Rhino3D Amira – http://www.amiravis.com/ Import for CT, MRI, Ultrasound images from current scanning devices via DICOM, Rhino3D – http://www.rhino3d.com/ US$195 Import for CT, MRI via DICOM Manually generate 3D solid model Import to Solidworks, Catia, Unigraphics etc
Review on Commercial Software – 3D Doctor http://www.ablesw.com/3d-doctor/index.html
Strand7 (Strand7 - Australian-own FE company, initiated from USYD)
– A powerful structural analysis program for analysing stress, vibration, dynamic, nonlinear and heat transfer characteristics without node limits.
– Easy to use.
– FEA software for highly nonlinear complex problems (Standard/Explicit).
– High-end parallelised program in super-computers
– ABAQUS/CAE interface with CAD systems
Cos m osWorks
– Build-in Solidworks CAD system
– Powerful linear solvers
General-Purpose FEA Software in AMME
Introduction to ANSYS – GUI Layout
Left mouse button picks (or unpicks) the entity or location closest to the mouse pointer. Pressing and dragging allows you to “preview” the item being picked (or unpicked).
Middle mouse button does an Apply. Saves the time required to move the mouse over to the Picker and press the Apply button. Use Shift-Right button on a two-button mouse.
Right mouse button toggles between pick and unpick mode. Note, the Shift-Right button on a two-button mouse is equivalent to the Middle mouse button on a three-button mouse.
ANSYS File System
Database and Files: The term ANSYS database refers to the data ANSYS maintains in memory as you build, solve, and postprocess your model. The database stores both your input data and ANSYS results data:
– Input data -- info you must enter, such as dimensions, material properties, and load data.
– Results data -- quantities that ANSYS calculates, such as displacements and stresses.
Defining the Jobname: Utility Menu > File> Change Jobname
The jobname is a name up to 32 characters that identifies the ANSYS job. When you define a jobname for an analysis, the jobname becomes the first part of the name of all files the analysis creates. (The extension or suffix for these files' names is a file identifier such as .DB.) By using a jobname for each analysis, you ensure that no files are overwritten.
Typical files in Ansys
jobname .db, .dbb: Database file, binary. Compatible across all supported platforms.
jobname .log: Log file, ASCII. Contains a log of every command issued during the session. If you start a second session with the same jobname in the same working directory, ANSYS will append to the previous log file (with a time stamp).
jobname .err: Error file, ASCII. Contains all errors and warnings encountered during the session. ANSYS will also append to an existing error file.
jobname .rst, .rth, .rmg, .rfl: Results files, binary. Contains results data calculated by ANSYS during solution.Compatible across all supported platforms.
File Management Tips:
• Run each analysis project in a separate working directory.
• Use different jobnames to differentiate various analysis runs.
• You should keep the following files after any ANSYS analysis: log file ( .log); database file ( .db); results files (.rst, .rth, …); load step files, if any (.s01, .s02, ...)
Defining an Analysis Title: Utility Menu> File> Change Title
This will define a title for the analysis. ANSYS includes the title on all graphics displays and on the solution output. ( Please include your name and student ID in the analysis title for all original graphs )
ANSYS File System – Cont’d
ANSYS File System – Cont’d
Methods of Solid Modeling
Top-Down method – Boolean Operation
Boolean Operation – Cont’d
ANSYS Element Type
There are two main meshing methods: Free and Mapped.
Free Mesh – Has no element shape restrictions.
The mesh does not follow any pattern.
Suitable for complex shaped areas and volumes.
Suitable for complex shaped areas and volumes.
Volume meshes consist of high order tetrahedral (10 nodes), large dof.
Mapped Mesh – Restricts element shapes to quadrilaterals (areas) and hexahedra (volume)
Typically has a regular pattern with obvious rows of elements.
Suitable only for “regular” shapes such as rectangles and bricks.
Mesh Density Control
Material Property and Unit
Unit (SI) – The ANSYS program does not assume a system of units for your analysis. You can use any system of units
Tasks of Week 1
Discussion for forming a team (shaft and cup)
Read papers and further literature review
Ansys online tutorial (login Ansys Help > tutorial)
Ansys tutorial in biomedical engineering (see handout)
Ansys tutorial: Model nail/callus in fractured femur Upper part of bone Lower part of bone Callus Fracture site Coating Implants