Obtaining low-speed impact properties of soft tissues

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Funding Agency:

MHRD

Investigators:

1. Dr A. Chawla

2. Dr S. Mukherjee

Other Collaborating Agencies:

Project Objective:

In this project we aim to develop a rig to test the low speed impact properties of soft human tissues. The target will be to develop a force actuated stylus / impactor in which the force as well as its displacement will be recorded as a function of time. This stylus will be made to impinge against the soft tissues in question and the force and displacement time histories will be used to estimate the properties of the tissues by a process of inverse mapping. The tissues will be modelled using Finite Elements and the impact with this impactor will be simulated. By iterating the properties of the tissues an attempt will be match the experimental and the simulated results, thereby estimating the properties of the tissues. In this project, the device will be used to measure the low speed impact properties of the external tissues. Once the device is ready, in the future it can also be used to measure the properties of abdominal organs in an operative environment. It will then help in getting impact properties of abdominal tissues – these properties are not easily obtained by other means.

 

Highlights of the work:

The objective of this study is to establish a methodology to identify the dynamic properties of soft tissues. Nineteen in vitro impact tests are performed on human muscles at three average strain rates ranging from 136/s to 262/s. Muscle tissues are compressed uniaxially up to 50% strain level. Subsequently, finite element simulations replicating the experimental conditions are executed using the PAM-CRASHTM, explicit finite element solver. The material properties of the muscles, modeled as linear isotropic viscoelastic material, are identified using inverse finite element mapping of test data using Taguchi methods. Engineering stress - engineering strain curves from experimental data and finite element models are computed and compared during identification of material properties at the above mentioned strain rates. Response of finite element models, with extracted material properties, falls within experimental corridors indicating the validation of the methodology adopted.

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