In response to an unprecedented demand for poster presentations at the upcoming ICMOBT meeting, a new submission route has been opened for “breaking news” posters that present the latest developments in the field. We’re looking to select an additional ten posters to be presented at the conference. If you are interested, please follow this  link http://csemails.elsevier.com/conf/templateabstract.doc and submit your poster to Jenny Wang jen.wang@elsevier.com before 30 November 2011 to ensure consideration by the committee. Decisions will be made by 2 December 2011.

Failure of pharmaceutical packaging incurs the risk of negative health outcomes and expensive product recalls. Pre-filled syringes represent a growing portion of the drug packaging market. During its working life, a syringe ex-periences stresses that may result in material damage. Specifically, the syringe barrel may develop microcracks that coalesce and propagate, causing the syringe to frac-ture and its contents to lose sterility. Abaqus/Standard offers the technologies necessary to include fracture and failure in the syringe design process. The extended finite element method (XFEM) allows for the analysis of crack initiation and propagation along an arbitrary, solution dependent path without the need for remeshing.

In the design of hearing instruments it is important to achieve the highest possible gain without introducing feedback between the microphone and loudspeaker. With more gain, a larger hearing loss can be accommodated and a greater number of users benefit.
Maximizing gain while minimizing the possibility of feed-back requires an optimal choice of design parameters. In this Technology Brief, we outline how Abaqus/Standard and Isight can be combined in a process to optimize the vibro-acoustic characteristics of hearing instruments.

Biodegradable polymeric stents must provide mechanical support of the stenotic artery wall for up to several months while being subjected to cyclic loading that af-fects the degradation process. To understand the appli-cability and efficacy of biodegradable polymers, a hypere-lastic constitutive model is developed for materials under-going deformation-induced degradation. The model was implemented in Abaqus/Standard and applied to a com-monly used biodegradable polymer system, poly (L-lactic acid) (PLLA).

In the adaptive bone remodeling process, the density of bone tissue changes over time according to the load it sustains. Elevated loads produce increases in bone den-sity while reduced loads cause reduction of bone density. The long term success of an orthopedic implant can be better predicted by including this process in the design workflow. In this Technology Brief, we demonstrate the Abaqus/Standard implementation of one of the leading bone re-modeling algorithms. User subroutine USDFLD is em-ployed to capture solution dependent material properties, and the approach is used in the analysis of a total hip re-placement design.

Electroencephalography (EEG) is used to obtain informa-tion about the electrical activity in the brain and is rou-tinely used to diagnose neurological abnormalities. The inverse problem in EEG refers to the procedure of locat-ing electrical sources in the brain from the extracranial electrical field measured on the scalp. The solution of the inverse problem requires the forward calculation of the electric field for a given source location. The significance of the inclusion of inhomogeneity and anisotropy in the electrical conductivity of the brain tissue in the forward solution is not well understood.

The ability of a finite element simulation to accurately capture the behavior of a structure strongly depends on the chosen material model. Not only must it be applica-ble to the given class of materials and intended applica-tion, it must be properly calibrated. Sophisticated material models that use many parameters can present a challenging calibration task. Optimization techniques can be employed to determine suitable pa-rameter values. In this Technology Brief, HEEDS, an optimization tool developed by Red Cedar Technology, will be used in conjunction with Abaqus to determine the parameters needed to model the viscoelastic behavior of a rate-dependent vinyl material.

The superelastic, shape memory, biocompatibility, and fatigue properties of Nitinol, a nickel-titanium alloy, have made the material attractive for medical devices such as cardiovascular stents. However, it is a complex material and difficult to process. Finite element modeling of Nitinol devices such as stents reduces testing and time-to-market by allowing the designer to simulate the stent manufacturing and deployment processes. The constitu-tive models for superelastic alloys are available as user subroutine libraries for both Abaqus/Standard and Abaqus/Explicit.

Trabecular bone must withstand the loads that arise during daily activities as well as those due to trauma. Investigation of the mechanical properties of trabecular bone presents a challenge due to its high porosity and complex architecture, both of which vary substantially between anatomic sites and across individuals. While Micro Finite Element (μFE) analysis of trabecular bone is the most commonly used method to analyze trabecular bone mechanical behavior, the large size of these models has forced researchers to use custom codes and linear analysis. The nonlinear capabilities in Abaqus allow efficient analysis of these models and provide  answers to important research questions.

The modelling of welds is desirable to predict the distortion of components during manufacture, the position and magnitude of peak residual stresses and to predict metallurgical effects in specific regions. Welds are a complex modelling problem requiring both thermal and structural solutions. This has lead to the development of several weld-specific simulation packages and codes for finite element analysis packages. This paper describes the application of the newly developed Abaqus 2D Weld Modeller to simulate the residual stress field in ferritic weld test specimens. The specimens were manufactured for an ongoing research programme in conjunction with The University of Manchester and Serco Assurance.

Electric Boat’s design process involves evaluating the structural stability of ring-stiffened cylinder structures through finite element analyses to simulate a static pressure load. Each design revision of the cylinders must be evaluated to verify that the structure meets the required stress criteria for the static pressure load; any revision to geometry or material would require the design to be reevaluated. Additionally, it is critical that the weight of the structure is kept as light as possible while still satisfying all stress and deflection criteria. This presentation documents the use of Isight and Abaqus to perform a weight optimization for static pressure loading on a ring-stiffened cylinder, varying geometry and model thicknesses.

Biomechanics testing of the lumbar spine, using cadaveric specimens, has the advantage of using actual tissue, but has several disadvantages including variability between specimens and difficultly acquiring measures such as disc pressure, bone strain, and facet joint contact pressure. A simulation model addresses all of these disadvantages. The objective of this work is to develop a method to simulate the biomechanics of the lumbar spine. A process is currently being used to convert a CT scan of a lumbar spine into a simulation model. The process includes converting the CT scan to a geometry file, creating a mesh of the bone and soft tissue, and assigning material properties to each element of the bone based on the bone density. Finally, the model is solved using Abaqus Explicit.

Total knee replacement gives proven good results for isolated patello-femoral osteoarthritis, but patello-femoral arthroplasty may be more appropriate because only the joint compartment is replaced. Although the femoral component of a patello-femoral prosthesis is smaller than in total knee arthroplasty, it is unknown whether strain-adaptive periprosthetic bone remodeling occurs following patello-femoral arthroplasty. The aim of the study was to evaluate and compare the stress shielding effect of prosthetic replacement with Finite Element (FE) modeling.

Genetic algorithms have become one of successful tools in design and topology optimization. The optimization module based on genetic algorithms was developed and employed in Abaqus/CAE by GUI and kernel scripting. The new module extends advanced functionality of Abaqus/CAE allowing to perform optimization directly in Abaqus Unified FEA product suite from SIMULIA. The genetic algorithms implemented in optimization approach are based on available GPL libraries. Significant improvement in evolving into optimal solution can be achieved when genetic algorithms are combined with neural networks which one can train by running Abaqus jobs, and substantially improve the efficiency of computations.

In this study we compare various way of quantifying high cycle radial fatigue behavior in a percutaneous Mitral repair device using Goodman methods. In order to provide an improved representation of the tissue-device interaction, we use an Ogden hyperelastic model to  simulate the native vessel with parameters obtained from pressure-diameter test data of human cadaver heart coronary tissue, and published data presented in previous work. We also examine how the computed peak tensile strains at the surface of this device differ from (a)The values computed at integration points in the 3D and (b) The same integration point values extrapolated to the nodal points and averaged over adjacent elements.

Prediction of respiratory motion has the potential to substantially improve cancer radiation therapy. A nonlinear finite element (FE) model of respiratory motion during full breathing cycle has been developed based on patient specific pressure-volume relationship and 4D Computed Tomography (CT) data. For geometric modeling of lungs and ribcage we have constructed

Computational modeling of stents can provide insight into critical locations (high stress/strain regions), help with design iterations/optimization, and reduce the need for bench-top testing. This study focuses on the developmental efforts to create a material model that can capture the mechanical response of poly-L-lactide (PLLA), the backbone of Abbott Vascular’s ABSORB Bioresorbable Vascular Scaffold (BVS). PLLA is an anisotropic, viscoplastic material. Its material behavior maybe affected by temperature, environment, and processing; thereby, introducing substantial challenges in modeling its response. A new test protocol was developed for performing material characterization experiments that can capture the anisotropic material response using a dog-bone shaped specimen.

Endovascular aneurysm repair involves insertion of an introductory component called guidewire through native vessels to help with the guidance of the delivery catheter. Guidewire tends to alter the vessel geometry due to its higher stiffness compared to the vessel wall. Very limited data is available to understand such interactions. Investigation of interaction between guidewire and native vessels could provide useful insight into vessel stresses and guidewire deformation in-vivo. This could further help in understanding the initial conditions for delivery catheter and device performance testing to improve deliverability in tortuous anatomy.

To enhance the fatigue life of metal components, frequently compressive stress is introduced to the surface layer. Although procedures such as shot peening have been practiced for many decades in other industries, an improved understanding of the fundamental mechanics that leads to the improved performance is desired. From a continuum mechanical point of view, the interaction between the crack and the stress intensity field is the factor determining whether the crack will propagate. Of special interest for fatigue performance is the propagation behavior of microstructurally short cracks, where the energy release rate, G, is smaller than the threshold value, Gth.

The stresses in a battery housing used in Implantable Pulse Generators (IPGs), also known as pacemakers, were investigated using Abaqus/Standard. There were three levels of analysis: the global level, the three-dimensional submodel level and the plane strain submodel level. The output of the global analysis was fed into the three-dimensional submodel analysis and subsequently the output of the three-dimensional submodel analysis was fed into the plane strain submodel analysis. The simulation results of the global model were used to drive the more detailed three-dimensional submodels on long and short sides of the battery models. The material properties of the heat affected zone and fusion zone were incorporated into the more detailed three-dimensional submodels.

Cataract surgery is the most common surgery in America today. Modern surgeries require the opacified crystalline lens to be removed and for a prosthetic lens to be inserted through a suture-less incision during a 5-10 minute outpatient procedure. The industry is driving for smaller incisions by redesigning the lens and insertion device geometry in addition to new materials. Typical lens dimensions are 6mm diameter with a center thickness of 1mm which is inserted through a 2.8mm incision. For the insertion the lens is folded and elongates while advancing down a tapering tube. Abaqus Explicit was chosen for this analysis because of its capability to solve large deformations and difficult self contact. During the insertion the lens can experience strains in excess of 60%.

The fracture of the proximal humerus is the second most common injury to the upper extremity. In severe fractures, surgery may be necessary which can be in the form of a locking plate holding the bones in place. This study examines the effect of including a bonegraft alongside the locking plate. ScanIP and +ScanCAD (Simpleware Ltd) were used to segment the proximal humerus from a CT scan, and to introduce CAD data of the fixation plate and bonegraft. The combined model of image data (proximal humerus) and CAD data (fixation plate, bonegraft) was then meshed in +ScanFE (Simpleware Ltd) were materials and contacts were defined. The materials for the bonegraft and locking plate were linear elastic.

Stents have been used in the treatment of coronary artery disease for decades, and their use in the peripheral arterial vasculature is growing rapidly. Mechanical loads imposed on peripheral stents may include loads due to arterial pulsation, axial compression, bending and torsion. These stents are most often manufactured using nitinol, a nickel-titanium alloy that exhibits unique shape memory and superelastic characteristics. Finite element analysis can be a powerful tool in designing medical devices to withstand such a rigorous loading environment. This paper will focus on the use of Abaqus/Standard for fatigue life characterization of nitinol stents and comparison of performance predicted by FEA to experimental data.

In the design of hearing instruments it is important to achieve as high gain as possible
without causing oscillation in the device, due to feedback between the microphones and the

Due to concerns over particle generation in conventional metal-on-polyethylene hip bearings used in total hip arthroplasty (THA), interest in advanced low-wear bearing alternatives such as ceramic-on-ceramic (CoC) couples has reemerged. While ceramics demonstrate excellent