Publications
Authors: J. R. Goossens, W. V. Mars, G. Smith, P. Heil, S. Braddock, and J. Pilarski
Published: 01/01/2017
Journal: SAE Technical Paper, 2017-01-1857, 2017
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Durability Analysis of 3-Axis Input to Elastomeric Front Lower Control Arm Vertical Ride Bushing
Abstract
Fatigue life prediction of elastomer NVH suspension products has become an operating norm for OEMs and suppliers during the product quoting process and subsequent technical reviews. This paper reviews a critical plane analysis based fatigue simulation methodology for a front lower control arm. Filled natural rubber behaviors were measured and defined for the analysis, including: stress-strain, fatigue crack growth, strain crystallization, fatigue threshold and initial crack precursor size. A se...
Fatigue life prediction of elastomer NVH suspension products has become an operating norm for OEMs and suppliers during the product quoting process and subsequent technical reviews. This paper reviews a critical plane analysis based fatigue simulation methodology for a front lower control arm. Filled natural rubber behaviors were measured and defined for the analysis, including: stress-strain, fatigue crack growth, strain crystallization, fatigue threshold and initial crack precursor size. A series of four distinct single and dual axis bench durability tests were derived from OEM block cycle specifications, and run to end-of-life as determined via a stiffness loss criterion. The tested parts were then sectioned in order to compare developed failure modes with predicted locations of crack initiation. In all cases, failure mode was accurately predicted by the simulation, and predicted fatigue life preceded actual end-of-life by not more than a factor of 1.4 in life.
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Authors: K. P. Barbash and W. V. Mars
Published: 04/04/2016
Journal: SAE Technical Paper, 2016.
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Critical Plane Analysis of Rubber Bushing Durability under Road Loads
Abstract
We demonstrate here an accounting of damage accrual under road loads for a filled natural rubber bushing. The accounting is useful to developers who wish to avoid the typical risks in development programs: either the risk of premature failure, or of costly overdesign. The accounting begins with characterization of the elastomer to quantify governing behaviors: stress-strain response, fatigue crack growth rate, crack precursor size, and strain crystallization. Finite Element Analysis is used to c...
We demonstrate here an accounting of damage accrual under road loads for a filled natural rubber bushing. The accounting is useful to developers who wish to avoid the typical risks in development programs: either the risk of premature failure, or of costly overdesign. The accounting begins with characterization of the elastomer to quantify governing behaviors: stress-strain response, fatigue crack growth rate, crack precursor size, and strain crystallization. Finite Element Analysis is used to construct a nonlinear mapping between loads and strain components within each element. Multiaxial, variable amplitude strain histories are computed from road loads. Damage accrues in this reckoning via the growth of cracks. Crack growth is calculated via integration of a rate law from an initial size to a size marking end-of-life. Multiaxiality is addressed via Critical Plane Analysis, in which damage accrual is computed for all potential crack plane orientations, prior to selecting the most critical orientation and its associated life. Variable amplitudes in the energy release rate history are considered via the application of rainflow counting, which is applied on each potential plane during the critical plane search. The analysis produces estimates of life for each element in the finite element model. These are visualized to identify bushing life and failure mode. Also, the analysis produces a diagnostic database enabling damage sources to be identified with respect to time, space, and orientation, and giving various details of the micromechanics of damage accumulation.
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Authors: Enduirica
Published: 01/06/2015
Journal:
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Why do we call it the Pure Shear test?
Abstract
This experiment is useful for both hyperelastic and fracture mechanical characterizations of rubber. We explain the nomenclature.
Authors: Endurica
Published: 01/06/2015
Journal:
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Comparing Pure Shear and Simple Shear
Abstract
The spin and rate of deformation tensors for these two common testing scenarios are computed and compared.
Authors: William V. Mars, Marion G. Pottinger
Published: 01/10/2013
Journal: Tire Science and Technology
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John R. Luchini — Tire Science Giant
Abstract
Dr. John Remo Luchini, a giant among scientists in the tire industry and a past president of the Tire Society, passed away at his home on September 27, 2013, after a short illness. John was a passionate and dedicated scientist known for repeated contributions to experimental and computational tire science and for exceptional service to the professional community. He had retired in 2011 as senior research scientist after a 34 year career with the Cooper Tire & Rubber Company.
John was born...
Dr. John Remo Luchini, a giant among scientists in the tire industry and a past president of the Tire Society, passed away at his home on September 27, 2013, after a short illness. John was a passionate and dedicated scientist known for repeated contributions to experimental and computational tire science and for exceptional service to the professional community. He had retired in 2011 as senior research scientist after a 34 year career with the Cooper Tire & Rubber Company.
John was born September 2, 1949, in Detroit, Michigan, and raised in Dearborn Heights, Michigan. He earned his B.S., M.S., and Ph.D. degrees in engineering at the University of Michigan, where he also met and married his wife Tamara. His doctoral thesis was supervised by Professor Sam Clark, during a period of high demand for more energy efficient tires. Entitled “Mathematical Model for Rubber Hysteresis,” his thesis explored the problem of...
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Authors: A.N. Gent, W.V. Mars, In: James E. Mark, Burak Erman and Mike Roland, Editor(s)
Published: 01/10/2013
Journal: The Science and Technology of Rubber (Fourth Edition), Academic Press, Boston, 2013, Pages 473-516, ISBN 9780123945846, 10.1016/B978-0-12-394584-6.00010-8
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Chapter 10 – Strength of Elastomers
Abstract
This chapter seeks to answer such questions as where and under what conditions does fracture begin, and what laws govern the growth of a crack once it has been initiated? First considered is the initiation of fracture from crack precursors, followed by the rate of development of cracks after initiation. The phenomenon of accelerated growth under dynamic stressing is also discussed. Then the effects of applied stresses and temperature of measurement are discussed, as well as other effects of the ...
This chapter seeks to answer such questions as where and under what conditions does fracture begin, and what laws govern the growth of a crack once it has been initiated? First considered is the initiation of fracture from crack precursors, followed by the rate of development of cracks after initiation. The phenomenon of accelerated growth under dynamic stressing is also discussed. Then the effects of applied stresses and temperature of measurement are discussed, as well as other effects of the environment, notably the destructive action of ozone. Finally, a brief survey of abrasive wear is given.
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Authors: W.V. Mars, M. Isasi, and A. Arriaga
Published: 01/10/2013
Journal: Constitutive Models for Rubber VIII – Gil-Negrete and Alonso, Editors, Pages 355-360, 2013 Taylor & Francis Group, London, ISBN 978-1-138-00072-8
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Loss of stiffness during fatigue and the development of crack precursors
Abstract
Jago (2012) recently reviewed techniques useful for imaging and surveying crack precursors, not only on the surface of a specimen, but also in the bulk. Crack precursors are seen to occur in a range of sizes, with smaller precursors occurring more frequently, and larger precursors occurring less frequently. For example, Mars & Fatemi (2006) reported observations in which precursors of size 20 microns occurred at a volume density of 5000/mm3, and precursors of size 100 microns occurred at a volum...
Jago (2012) recently reviewed techniques useful for imaging and surveying crack precursors, not only on the surface of a specimen, but also in the bulk. Crack precursors are seen to occur in a range of sizes, with smaller precursors occurring more frequently, and larger precursors occurring less frequently. For example, Mars & Fatemi (2006) reported observations in which precursors of size 20 microns occurred at a volume density of 5000/mm3, and precursors of size 100 microns occurred at a volume density of 3/mm3.
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Authors: W.V. Mars, X.Z. Cheng, H. Yang, and L.Q. Zhang,
Published: 01/10/2013
Journal: Constitutive Models for Rubber VIII – Gil-Negrete and Alonso, Editors, Pages 371-376, 2013 Taylor & Francis Group, London, ISBN 978-1-138-00072-8
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Influence of cyclic softening on the energy release rate of an edge crack under simple tension
Abstract
Prior to the advent of finite element analysis for nonlinearly elastic materials at finite strains, the problem of computing the mechanical fields surrounding the tip of a crack in an elastomer was considered completely intractable (Gent and Mars 2013). This limitation, along with recognition that the stress-concentrating power of the crack tip is responsible for crack growth, inspired Rivlin and Thomas (1953) to develop an energetic theory for the analysis of cracks, following Griffith’s orig...
Prior to the advent of finite element analysis for nonlinearly elastic materials at finite strains, the problem of computing the mechanical fields surrounding the tip of a crack in an elastomer was considered completely intractable (Gent and Mars 2013). This limitation, along with recognition that the stress-concentrating power of the crack tip is responsible for crack growth, inspired Rivlin and Thomas (1953) to develop an energetic theory for the analysis of cracks, following Griffith’s original concept (Griffith 1921). The approach considers the supply of energy associated with growth of a crack, and it avoids the need to understand crack tip fields in detail. It has proven so elegant and powerful that it has been widely adopted into practice. For a general overview of fracture mechanics in elastomers, see Lake (2003) or Thomas (1994).
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Authors: WV Mars, D Ostberg
Published: 03/10/2012
Journal: ENDURICA LLC FINDLAY OH (2012)
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Fatigue Damage Analysis of an Elastomeric Tank Track Component
Abstract
Abstract: The backerpad on the Abrams tank track system is an elastomeric cushion that protects the track and has direct contact with the tank’s wheels. The backerpad’s service life is limited by harsh operating conditions, and system designers are challenged to extend that limit. Accordingly, an analysis is demonstrated here of an experimental backerpad’s fatigue performance under the action of a tank roadwheel epeatedly rolling over the pad. First, the elastomer is characterized via tes...
Abstract: The backerpad on the Abrams tank track system is an elastomeric cushion that protects the track and has direct contact with the tank’s wheels. The backerpad’s service life is limited by harsh operating conditions, and system designers are challenged to extend that limit. Accordingly, an analysis is demonstrated here of an experimental backerpad’s fatigue performance under the action of a tank roadwheel epeatedly rolling over the pad. First, the elastomer is characterized via tests that define its fatigue behavior. Next, the multiaxial, variable amplitude duty cycle of the pad through a representative rollover event is computed in ABAQUS/Explicit. Finally, the material characterization and duty cycle are analyzed via the fe-safe/Rubber fatigue life solver to estimate damage accumulation in each finite element of the model. The calculation identifies the location and number of duty cycle repeats associated with the first appearance of 1 mm cracks for the selected duty cycle, providing an example of how fatigue analysis may be applied to understand damage development in elastomeric components.
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Authors: WV Mars
Published: 01/09/2012
Journal: Rubber Chemistry and Technology 85 (2012)(3), 493
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Book Review: Engineering with Rubber, Edited by AN Gent
Abstract
When a text has influenced a large enough audience, for a long enough time, it becomes a classic. We expect that newcomers to the field will enter through this text, and that established professionals will have a well-worn copy in their personal library. Alan Gent's Engineering with Rubber: How to Design Rubber Components is such a classic. It has just been published by Hanser in a 3rd edition, offering a valuable guide to the fundamentals of rubber component mechanical design.
