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Quantification of Clamp Loss and Subsequent Loosening of Automotive Hub-Knuckle Joints under Time-Varying Proving Ground Loading

FCA US LLC-Sandip Datta, Parag Nittur
  • Technical Paper
  • 2020-01-0181
To be published on 2020-04-14 by SAE International in United States
Threaded fasteners or bolted joints are used extensively in automotive components. There are standard procedures to evaluate joint performance under block cycles or road loads. The deciding load case for such joint design is the slippage analysis of the joint. There are studies done to evaluate the theoretical and experimental behavior of these joints. There are different ways of understanding the interaction between the bolt and the nut under different loading scenarios. However, none has provided a satisfactory method of quantifying the bolt loosening or loss of clamp under cyclic loading where initially no slippage is observed. Under varying loads, initial relaxation of the joint is followed by a loss of clamping load to below the critical value. Below a critical value, complete loss of clamping load happens very rapidly and results in a loose joint. The loss of clamping load below the critical value happens at a transition stage when both elastic deformations of the bolt as well as external moments contribute to rapid loosening. This study provides an overall understanding of geometric parameters…
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Elastomeric Component Fatigue Analysis: Rubber Fatigue Methodology and Correlation between Crack Initiation and Crack Growth

FCA US LLC-Touhid Zarrin-Ghalami, Sandip Datta, Robert Bodombo Keinti, Ravish Chandrashekar
  • Technical Paper
  • 2020-01-0193
To be published on 2020-04-14 by SAE International in United States
Many elastomeric components in automotive industry applications are subjected to dynamic service loads. Fatigue must be a consideration in the design of these components. The two approaches in rubber fatigue analysis discussed in this study are the conventional crack initiation approach, based on continuum mechanics parameters versus life, and the crack growth approach, based on fracture mechanics parameters. These methodologies were utilized and illustrated for a passenger vehicle engine mount here. Temperature effects are not considered since testing was performed at ambient room temperature and with a low frequency, typically less than 5 Hz. This promising methodology for fatigue life prediction, discussed in this paper, is a critical plane approach based on crack energy density. Rainflow cycle counting method and Miner’s damage rule are used for load cycle characterization and damage accumulation respectively. A fracture mechanics approach is implemented based on specimen crack growth data. This methodology is validated with component testing under constant amplitude experiments. Results are investigated through analysis of critical stress locations, life values, and strain states. Comparative results are presented. Numerical…
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Simultaneous Durability Assessment and Relative Random Analysis Under Base Shake Loading Conditions

Booz Allen Hamilton Inc-Karl Sweitzer
CAEfatigue, Ltd.-Neil Bishop
Published 2017-03-28 by SAE International in United States
For many automotive systems it is required to calculate both the durability performance of the part and to rule out the possibility of collision of individual components during severe base shake vibration conditions.Advanced frequency domain methods now exist to enable the durability assessment to be undertaken fully in the frequency domain and utilizing the most advanced and efficient analysis tools (refs 1, 2, 3, 4, 5). In recent years new capabilities have been developed which allow hyper-sized models with multiple correlated loadcases to be processed. The most advanced stress processing (eg, complex von-Mises) and fatigue algorithms (eg, Strain-Life) are now included. Furthermore, the previously required assumptions that the loading be stationary, Gaussian and random have been somewhat relaxed. For example, mixed loading like sine on random can now be applied.The check for “collisions” has previously been done separately with the resultant “doubling up” of the analysis being both time consuming and cumbersome.However, new technological advances now make it possible to do both these calculations at the same time and this paper will present results for…
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3D Simulation Models Simplified to 2D Planar/Axisymmetric Problems in Automotive Structures

FCA US LLC-Wenxin Qin, Sandip Datta, Weidong Zhang
Published 2016-04-05 by SAE International in United States
In automotive FEA analysis, there are many components or assemblies which can be simplified to two-dimensional (2D) plane or axisymmetric analytical problems instead of three-dimensional (3D) simulation models for quick modeling and efficient analysis to meet the timing in the design development process, especially in the advanced design phase and iteration studies. Even though some situations are not perfectly planar or axisymmetric problems, they may still be approximated in 2D planar or axisymmetric models, achieving results accurate enough to meet engineering requirements. In this paper, the authors have presented and summarized several complex 3D analytical situations which can be replaced by simplified plane axisymmetric models or 2D plane strain analytical models. Several numerical case studies presented in this paper demonstrate that plane axisymmetric and 2D planar models can provide efficient, reliable, and accurate analytical results as compared to the analytical results of equivalent 3D models. These case studies are intended to be used as reference for auto industry and CAE/FEA peers.
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Application of the Glinka's ESED Criterion in Optimization Design

Chrysler Group LLC-Wenxin Qin, Sandip Datta
Chrysler LLC-Fred Zweng
Published 2014-04-01 by SAE International in United States
In order to take into account the local material non-linear elastic-plastic effects generated by notches, Glinka proposed the equivalent strain energy density (ESED) Criterion which has been widely accepted and used in fatigue theory and calculation for the last few decades. In this paper, Glinka's criterion is applied to structural optimization design for elastic-plastic correction to consider material non-linear elastic-plastic effects. The equivalent (fictitious) stress was derived from Glinka's Criterion equation for the commonly used Ramberg-Osgood and bi-linear stress and strain relationships. This equivalent stress can be used as the stress boundary constraint threshold in structural optimization design to control the elastic-plastic stress or strain in nonlinear optimization. Examples demonstrated this application was an efficient and effective practice within the material non-linear elastic-plastic range when using the equivalent elastic stress as constraints in automotive engineering structural optimization designs.
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