Fifth International Conference on Engineering Failure Analysis, 1-4 July 2012, Hilton Hotel, The Hague, The Netherlands

To register, go to http://www.icefaconference.com

Composite structures often have a higher capacity for ab-sorbing energy than their metal counterparts. The crush-ing behavior of composite materials is complex, and the inclusion of composite components in vehicles for crash protection can necessitate expensive experimental test-ing. The ability to computationally simulate the crushing response of composite structures can significantly shorten the product development cycle and reduce cost in the aerospace, automotive, and railway industries. In this Technology Brief, we describe a methodology for modeling the crushing behavior of composite structures using Abaqus/Explicit.

The uniform pressure method (UPM) approach to simulat-ing airbag deployment has been widely used in the auto-mobile safety industry. The defining assumption of UPM, specifically that pressure in the airbag is spatially uniform during inflation, makes the approach most applicable for „in-position‟ (IP) analyses with fully inflated airbags. In contrast, an analysis may be characterized as „out-of-position‟ (OoP) if the occupant interacts with the airbag before it is fully deployed. Prior to complete inflation, large spatial pressure gradients can exist in the airbag, violating the assumptions of the UPM approach. The advancement of airbag regulations and technology necessitates the consideration of OoP scenarios.

In a traditional automobile noise, vibration and harshness (NVH) analysis, stationary tires are defined and subjected to vertical dynamic loading. The actual operating condi-tions of a tire involve rolling however, and the vibration characteristics of rolling tires are considerably different from those of stationary tires. Abaqus offers a methodology to include the pre-loading and gyroscopic effects of rolling tires in a forced response dynamic analysis of the moving vehicle. This article closely follows SIMULIA Technology Brief TB-08-TVC-1 and illustrates the use of substructures in a typical NVH analysis for a full vehicle model with steadily rolling tires.

In the automobile industry, kinematics and compliance (K&C) testing is used to evaluate the ride and handling performance of an automobile. The traditional approach to numerical simulation of K&C testing involves the use of multi-body dynamics software, which simplifies the phys-ics by introducing rigid body assumptions. In this Technology Brief, a new methodology for K&C simulation is demonstrated using Abaqus/Standard. This approach differentiates itself from that of traditional rigid body simulations by accounting for component flexibility as well as geometric and material nonlinearities.

Accurate simulation of an anti-lock brake system (ABS) requires detailed modeling of separate subsystems in dif-ferent physical domains. Creating refined models of the brake, wheel, and control components with a single analy-sis tool is difficult, if not impossible. The strategy of co-simulation can be adopted to meet this challenge; differ-ent simulation tools can be used simultaneously to create multi-disciplinary and multi-domain coupling. In this Technology Brief, a co-simulation approach using Abaqus and Dymola is used to achieve a realistic system-level simulation of an ABS. The tire, wheel, brake caliper mechanism, and road are simulated with a detailed Abaqus finite element model while the brake system con-trol algorithm and hydraulics and are simulated with Dy-mola.

The Biofidelic Rear Impact Dummy (BioRID-II) hardware model has been developed to measure automotive seat and head restraint system performance in low-speed rear end crashes. It has also been used to further the under-standing of whiplash injuries. This technology brief fo-cuses on the Abaqus BioRID-II finite element model, which has been developed in cooperation with the Ger-man Association for Research in Automobile Technology FAT. The capabilities of the model will be described, and a comparison with experimental data is shown.

Tires are the only load transfer mechanism between a vehicle’s suspension and the road. Consequently, tire vibration has a significant impact on ride quality and vehicle interior noise.
To accurately predict the frequencies and mode shapes of a rolling tire, Abaqus allows pre-loading and gyroscopic effects to be included in a complex frequency extraction. These effects can also be included in a forced response analysis of the rolling tire to predict the  spindle forces contributing to vehicle noise and vibration. In this Technology Brief, we outline the analysis methodology for determining the vibration characteristics of stationary and steadily rolling tires.

The B-pillar is an important load carrying component of any automobile body. It is a primary support structure for the roof, and is typically a thin-walled, spot-welded, closed-section structure made from high strength steels. As part of the validation process, the B-pillar can be ex-perimentally loaded at quasi-static rates until failure†. The force and displacement of the impactor are measured to get valuable insight into the stiffness characteristics of the structure.

During product development, design engineers often have the freedom to modify a number of parameters. However, any design modification requires validation to ensure the satisfaction of requirements for all load cases. With Abaqus for CATIA V5 (AFC), nonlinear finite element technology is made available within the CATIA environment, allowing design engineers to efficiently incorporate accurate stress analysis into the design process. In this Technology Brief two approaches are described to illustrate the productivity gains possible with AFC. The first uses CATIA’s Knowledgeware capability to define parametric studies that assist in making engineering decisions. With this approach, geometry and load parameters can be captured in a design table to further simplify model modifications.

This technology brief illustrates typical mode-based noise, vibration, and harshness (NVH) analyses of a full automobile model using the Abaqus product suite. Abaqus/AMS, the automatic multi-level substructuring eigensolver, is used to compute the eigensolution. A steady-state dynamic analysis is then performed in Abaqus/Standard. The significant performance benefit of using Abaqus/AMS and the SIM-based linear dynamics architecture will be demonstrated for uncoupled structural and coupled structural-acoustic analyses.

A methodology to study the sound radiation of engine valve covers is presented. The analysis process uses a nonlinear static simulation followed by a steady state dy-namics simulation to determine the sound pressure field due to the vibration of the engine cover. The effects of assembly loads are included. The methodology is dem-onstrated with two representative engine valve covers using acoustic finite and/or infinite element methods. Good correlation between the analysis results and avail-able experimental data is achieved.

The National Highway Traffic Safety Administration (NHTSA) mandates the use of certain test procedures to determine automobile roof crush resistance. In the test the force-deflection behavior of the roof structure is meas-ured by quasi-statically pressing a precisely positioned rigid plate against the automobile. As part of the design process, the test is often simulated analytically. As with many quasi-static processes, the roof crush resis-tance test can be simulated in Abaqus/Standard or Abaqus/Explicit. In this technology brief the modeling techniques used for each analysis product are presented, and it is shown that both products can be used to simu-late a roof crush resistance test effectively.

A methodology to study friction-induced squeal in a com-plete automotive disc brake assembly is presented. The analysis process uses a nonlinear static simulation se-quence followed by a complex eigenvalue extraction to determine the dynamic instabilities that are manifested as unwanted noise. The effects of assembly loads; nonuni-form contact pressure between the brake linings and disc; velocity-, temperature-, and pressure-dependent friction coefficients; friction-induced damping; and lining wear can be included. The methodology is demonstrated with a representative disc brake assembly. Good correlation be-tween the analysis results and available experimental data is achieved.

Spot-welded, thin-walled curved beams, which constitute the main structural members in many automobile and other ground vehicle body structures, play a significant role in absorbing energy during a collision. Due to their extensive use, it is important to study the collapse charac-teristics of these curved members (Ref. 1). Abaqus/Explicit can be used effectively to simulate the quasi-static collapse of spot-welded structural members accu-rately.

A wide range of loading conditions must be considered in the design of a tire. Computational simulations of a quasi-static, steady-state dynamic and nonlinear transient dy-namic nature must be completed. In addition, the com-plexity and size of typical tire models highlight the need for efficient solution techniques.

This work describes a numerical methodology based on the Finite Element approach able to simulate the dynamic maneuver of the full vehicle running on fatigue reference roads. The basic idea of present work stays in combining a moderately complex and general tire model with traditional full-vehicle methods, including both implicit and explicit finite element techniques, in order to predict – within the early design phases when no prototypes are available - the loads transmitted to the vehicle running on the real fatigue reference roads. Some issues related to application of tire finite element model to a long simulation time in an explicit solution have been discussed. The real fatigue load is digitalized and implemented as a rigid body in the explicit code.

Snow traction is an important tire performance parameter for product applications in markets where snow is present for several months during the year. It is very difficult to perform multiple tests because proving grounds and consistent test conditions are available only for limited periods of time and due to prototyping and test expense. This paper deals with the simulation aspects of the snow traction test using Abaqus. The first part of this paper describes the chosen test method and offers a review of the available simulation technology. A modeling methodology for realistic snow interaction is examined using small-scale simulations, in order to evaluate its applicability to snow traction simulations.

Automotive vehicles undergo various ranges of road loads according to the driving conditions. Sometimes it experiences unusually large overload such as pot-hole impact or curb strike whose forces are several times of the vehicle weight. Those overloads may induce plastic deformations at some components and these plastic deformations reduce the fatigue life of the components. In some cases, the fatigue crack initiation points may be changed due to the residual stresses which were generated by the overloads. Predicting the fatigue life by general fatigue analysis methodology, which uses linear stress analysis results and linear damage accumulation rule, is very difficult if any component contains residual stresses.

Product development is becoming more complex. It involves not only system simulation requirements, but also the need to manage and share huge amounts of engineering information that is housed throughout the world. It quickly becomes complex when getting into detailed system simulation for powertrain applications such as sealing products.

Skid a full vehicle against a curb in lateral and longitudinal direction are two out of several tests to proof the strength of a suspension. Knowing the internal forces acting on suspension components during such an event is extremely important for being able to dimension safety critical parts correctly. Measuring these loads is an elaborate task, because the use of wheel force transducers is not possible due the risk of damaging them. It is necessary to apply strain gauges and force cells instead.
Therefore the possibility of a fully virtual approach using Abaqus/Explicit would be of great value. A Mc Pherson front suspension has been used as an example to demonstrate :
• Retrieving internal suspension forces

In this study, carried out by fka, the hood of the VW Golf V is taken as an example to analyze the potential of a hybrid construction of aluminum and steel. Structural stiffness, oil canning and dent resistance behavior are analyzed using Abaqus/Standard. With the objective of reducing the total hood weight, the performance of the hood is compared to reference values of the series production steel hood.

Fatigue life prediction has reached a high level in respect to practical handling and accuracy in the last decades. As a result of insecure or lacking input data deviations between numerical results and test results in terms of cycles till crack initiation are possible. On the one hand, the accuracy of Finite Element results gets better and better because of greatly increasing computer power and mesh density. Whereas on the other hand, the situation is much more critical regarding load data and especially regarding local material properties of the components.
In the last few years also the possibilities of process simulation have improved in such, that at least a few local material properties or quality indicators can be predicted with sufficient reliability.

In 2006 BMW made a decision to use Abaqus/Explicit for all issues concerning passive safety in the virtual design process. Code quality and reliability of simulation results were identified as the primary reasons to change, and from that decision point forward, all product development teams began migration activities to switch to Abaqus/Explicit. Meanwhile, the entire vehicle design and development process within BMW began to undergo fundamental changes, from one which previously incorporated key milestones involving physical prototypes, to one which seeks to largely eliminate physical prototypes and associated physical tests. Nowadays, BMW design engineers will get the first feedback from physical tests only after the series production tools have been manufactured.