The objective of this study is to establish a methodology to identify the dynamic properties of s... more 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-CRASH TM , explicit finite element solver. The material properties of the muscles, modelled as linear isotropic viscoelastic material, are identified using inverse finite element mapping of test data using Taguchi methods. Engineering stressengineering 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.
In passive automotive safety, advanced Human Body Models for injury prediction based on the Finit... more In passive automotive safety, advanced Human Body Models for injury prediction based on the Finite Element (FE) method (e.g. Thums or GHBMC families) have the potential to represent the population variability and to provide more accurate injury predictions than alternatives using global injury criteria. However, these advanced HBMs are underutilised in industrial R&D. Possible reasons include difficulties to position the models - which are typically only available in one posture - in actual vehicle environments, and the limited representation of the population variability (size, weight, limited availability for specific populations such as children, etc.). As the models and methodologies to use them are not standardized or widely shared, research achievements have been slow to result into safety benefits for the whole community. The main objective of the PIPER project was to develop user friendly tools to position and personalize these advanced HBMs, and to share them widely with th...
Computational Modeling Before testing, a detailed FE mesh of the specimen was obtained using CT s... more Computational Modeling Before testing, a detailed FE mesh of the specimen was obtained using CT scans. In order to capture the non‐ homogeneity of the material, the mesh was divided into twenty material sets based on Hounsfield Number from CT Scans and material properties were assigned to them. Long bones are seen to exhibit strain‐rate dependency in stiffness as well as in failure. Therefore, it was concluded that rate‐dependency has to be captured for an accurate structural and failure characterization of the bones. Data from the experiments have therefore been utilized in understanding bone behaviour under impact and capturing the same using computer simulations. A user‐defined material model was developed that incorporates the rate dependency of stiffness, yielding and failure. A logarithmic relation was used to model strain‐rate dependency of elastic modulus, yield and damage initiation. A Drucker‐Prager plastic model was chosen as it captures dilation of bone and asymmetry in ...
Select study of urban freight in Delhi Research and advocacy on public transport and in-use vehic... more Select study of urban freight in Delhi Research and advocacy on public transport and in-use vehicle management Sponsor: CEFIPRA (Indo French Centre for Advanced Scientific Research) Sponsor: Volvo Educational Research Foundations, Sweden Project team: Geetam Tiwari and K.R. Rao Project team: Dinesh Mohan, Geetam Tiwari, Anoop Chawla, Sudipto Mukherjee, Objective: This project includes major interventions at two levels product and S.R.Kale, Sanjeev Sanghi, Puneet Mahajan, Niladri Chatterjee process. The product involves use of Intelligent Transportation Systems (ITS) Objective: To develop resources and expertise in the control of adverse health technology, for developing performance indicators for Bus Rapid Transit (BRT)/ bus effects of road transport in as integrated a manner as possible and wide systems. At the process level, the aim is to improve the operation of BRT by means dissemination of this knowledge. This process involves: (a) prevention of pollution of branching modules, ...
In passive safety, advanced Human Body Models (HBMs) for injury prediction based on the Finite El... more In passive safety, advanced Human Body Models (HBMs) for injury prediction based on the Finite Element (FE) method have the potential to represent the population variability and to provide more accurate injury predictions than alternatives using global injury criteria. However, these advanced HBMs are underutilised in industrial research and development (RD the use of a priori knowledge regarding human body shape and posture to help define personalising or positioning targets (WP2); and applications of the software to existing HBMs (incl. the GHBMC model, Thums V3, and child models that will be improved during the project).
The current manuscript reports on the development status of a software framework to scale (person... more The current manuscript reports on the development status of a software framework to scale (personalize) and position Human Body Models used in safety applications, i.e. the PIPER framework. The framework is both model and code agnostic and it was successfully used with Thums, GHBMC and the new PIPER scalable child model. Various transformation methods to scale or positioning were implemented in an interactive application. The software was released under the Open Source General Public License (GPL) version 2.
In a significant number of automobile crashes involving pedestrians, the knee ligament which cont... more In a significant number of automobile crashes involving pedestrians, the knee ligament which controls the stability of the knee often get severely loaded. In lateral impact on knee during automotive crashes, varus-valgus deformities result in failure of ligament by avulsion or rupture. Varus-valgus deformity strains occur mainly in the middle region of ligament and it is known that properties vary in the different regions of the ligament. Experimental measurement of tensile-load elongation behavior of bovine middle region medial collateral ligament properties between strain rate 0.0001/s to 161/s are reported here. The results shows a linear stress-strain response at lower strain rate whereas it is nonlinear and strain rate sensitive in dynamic loading conditions. The objective of this study is to establish a methodology to identify the quasi-static and dynamic properties of ligaments.
Accurate reduction of two-dimensional curve noises is crucial to metrology and reverse engineerin... more Accurate reduction of two-dimensional curve noises is crucial to metrology and reverse engineering. In this paper we propose a set of schemes for two-dimensional curve denoising. Our approach consists of three main steps: 1) feature-based pre-smoothing of noised polylines; 2) curve partitioning of polylines into different regions; 3) two hybrid denoising schemes of arbitrary polylines with noises. Numerical experiments indicate the effectiveness of our approach against existing methods.
Knee injuries are common in automobile pedestrian crashes. Lateral impact on the knee results in ... more Knee injuries are common in automobile pedestrian crashes. Lateral impact on the knee results in varus-valgus bending and causes injuries to collateral ligaments. Mechanical properties of ligaments under different loading conditions are important for developing human body finite element model to predict the injury risk to pedestrians in automobile crashes and for safer design of vehicle fronts. Tensile properties of the middle region of medial collateral ligament are reported between 0.0001/s to 140/s as obtained from isolated ligament tests. The results show a linear stress-strain response at lower strain rate whereas it is nonlinear and strain rate sensitive in dynamic loading conditions. Knee Joints, Injuries, Pedestrians, Ligament, Viscoelasticity PEDESTRIAN-AUTOMOBILE COLLISIONS often result in severe injuries to the lower extremities. In lateral impact the varus-valgus strain results in injuries to the collateral knee ligament (Kajzer et al. 1990, 1993, 1999, Kerrigan et al. 2003). In lateral impact on knee during automotive crashes, varus-valgus deformities result in failure of ligament by avulsion or rupture (Teresinki et al. 2001). Medial collateral ligament is the main focus of attention as it is the most frequently injured ligament. Further, it is known that constitutive properties of ligaments are not the same in different regions of the ligament (Robinson et al. 2005). There have been some studies on the mechanical properties of collateral ligaments (
This paper investigates correlation between throwing distance and impact speed / point of impact ... more This paper investigates correlation between throwing distance and impact speed / point of impact for bicycle-car front-to-side crash. Crashes between a bicycle and a car were simulated using multi body models developed in MADYMO TM. The Hybrid III 50th percentile male dummy model, available from MADYMO library has been used. Crash configurations reported in literature have been used and parametric variations have been done in speed, and point of impact. It is observed that only some configurations show a monotonic dependence of the throwing distance on the car speed.
During impact with an automobile, a pedestrian suffers multiple impacts with the bumper, hood and... more During impact with an automobile, a pedestrian suffers multiple impacts with the bumper, hood and the windscreen. Optimisation of the car front using a scalar injury cost function has been demonstrated. The results for impacts simulated in MADYMO show good co-relation with Euro-NCAP ratings for existing vehicles. Optimization of the car front to minimise the injury cost converges to vehicle profiles with features known from earlier studies to be pedestrian friendly. A method to design car fronts for pedestrian safety is evolved.
A finite element methodology has been developed for predicting the behaviour of honeycomb structu... more A finite element methodology has been developed for predicting the behaviour of honeycomb structures. Dynamic analysis of hexagonal aluminium honeycomb structures is carried out using PAM-CRASH TM , an explicit FE analysis code, and the result are verified against experimental data. Relationship between the crushing behaviour of honeycomb and simulation parameters has been established. The simulation results are also compared with theoretically predicted values.
This paper investigates the effect of muscle contraction on lower extremity injuries for pedestri... more This paper investigates the effect of muscle contraction on lower extremity injuries for pedestrian walking posture in a carpedestrian lateral impact at low speed. The full body model, pedestrian model with active lower extremities (PMALE), which was configured in a symmetric standing posture, has been repositioned in the walking posture. Finite-element simulations have then been performed using the PMALE in walking posture and front structures of a car. Two impact configurations, i.e. impact on the right and left legs, have been simulated. Two pre-impact conditions, that of a symmetrically standing pedestrian, representing a cadaver and an unaware pedestrian have been simulated for both the impact configurations. Stretch-based reflexive action was included in the simulations for an unaware pedestrian. It is concluded that (1) with muscle contraction, the risk of ligament failure decreases whereas the risk of bone fracture increases; (2) in lateral impacts, MCL could be considered as the most vulnerable and LCL as the safest ligament; and (3) for a walking pedestrian, PCL would be at a higher risk in the case of impact on the rear leg, whereas ACL would be at a higher risk if car strikes the front leg.
SAE International Journal of Passenger Cars - Mechanical Systems, 2009
The Engineering Meetings Board has approved this paper for publication. It has successfully compl... more The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE's peer review process under the supervision of the session organizer. This process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.
Human body finite element (FE) models for use in impact simulations require soft tissue character... more Human body finite element (FE) models for use in impact simulations require soft tissue characterization at high strain rates. The objective of the current work is to extract viscoelastic properties of passive muscle tissues at high strain rates and study their rate dependency. A procedure to identify the dynamic properties of passive muscle tissue under impact has been proposed using isolated-tissue experiments, FE simulations and Genetic Algorithm (GA) based optimization. Data from nineteen impact tests on unconfined isolated human muscles for strain rate ranging from 132/s to 262/s were used [1]. Tissues were compressed up to approximately 50 % strain and the force-time response was recorded. FE simulations of these impact tests have been performed in the present study by modeling the muscle as linear viscoelastic. RMS of the deviation between the experimental and FE force data, sampled at 10 kHz, was then minimized to predict the material parameters, bulk modulus, short-term shear modulus and long-term shear modulus. This parameter identification process was automated using PAM-CRASH TM , open source GA code [2] and C++ programming. In the present study a predefined generation size is used for optimization. Optimal bulk modulus, short term shear modulus and long term shear modulus for three average strain rates were found to be 73200, 13100, 347 Pa for 136/s; 278000, 26200, 1510 Pa for 183/s; 317000, 34900, 5210 Pa for 262/s respectively. The variation obtained in these properties with strain rates suggests that the linear viscoelastic model being used for muscle tissues is not a perfect choice for characterizing the dynamic compressive behaviour of these tissues. The proposed methodology offers a method for determining soft tissue properties at different strain rates. The usage of GA based optimization eliminates the determination of derivatives as used in conventional optimization techniques [3]. With minimal effort, this method can also be extended to other material models considered for muscle characterization.
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