software

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.

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 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.

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.

Metal welding processes are employed in various indus-tries. Gas welding techniques use the heat from a flame to melt the parts to be joined and a filler material simulta-neously. Extreme thermal loading is applied to the parts being joined, and complex material responses are initi-ated. The steep, localized thermal gradients result in stress concentrations in the welding zone. Consequently, modeling and simulation of welding processes are often complex and challenging.

Filament winding has become a popular construction technique in a wide variety of industries for creating com-posite structures with high stiffness-to-weight ratios. The difficulty in accurately analyzing the structural behavior of a filament wound body derives from the continually vary-ing orientation of the filaments. The standard capabilities of commercial finite element codes are inadequate to model the spatial variation of fiber orientation in a practical way.

Abaqus/CAE includes modeling and postprocessing capabilities for fracture mechanics analyses. These features provide interactive access to the contour integral fracture mechanics technology in Abaqus/Standard. Several fracture-specific tools are available, such as those for creating seam cracks, defining singularities, selecting the crack front and crack tip, defining q-vectors or normals to the crack front, and creating focused meshes. With these tools models can be created to estimate J-integrals, stress intensity factors, and crack propagation directions.