Investigation of Structural and Material Effects on Crashworthiness of Advanced High Strength Steel Columns

An experimental and numerical study was performed to evaluate the crashworthiness of several advanced high strength steels. The behavior of two Dual Phase (DP) steels and an HSLA steel are compared by examining the crush response of longeron column specimens, experimentally and computationally. The closed section columns, fabricated by spot welding formed channel sections, in both single hat and double hat configurations were exposed to 182 kg and 454 kg axial impacts at different velocities. Final column height and impact force history were recorded and compared with results of finite element simulation of the columns. Good agreement was found between experiments and computations.

Meshless Analyses of Fracture, Plasticity and Impact

The governing equations for rate-independent large strain plasticity are formulated in the framework of meshless method. The numerical procedures, including return mapping algorithm, to obtain the solutions of boundary-value problems in computational plasticity are outlined. The crack growth process in elastic-plastic solid under plane strain conditions is analyzed. The large strain plastic response of material under high-speed impact is simulated. Numerical results are presented and discussed.

An Energy Boundary Element Formulation for Predicting the Acoustic Field Around a Vehicle at High Frequencies Due to Airborne Noise Sources

An Energy Boundary Element Analysis (EBEA) formulation is presented for calculating sound radiation from a source with arbitrary shape at high frequency. The basic integral equation for the EBEA is derived including a half-space boundary condition. The time and frequency averaged acoustic energy density and acoustic intensity constitutes the primary variables of the new formulation, and the corresponding Green’s functions are derived. The governing equations for the EBEA are established and the numerical formulae for the coefficients of the system matrix, the acoustic energy density, and the acoustic intensity are derived using a Gaussian quadrature. The EBEA formulation and the corresponding numerical implementation are validated by comparing EBEA results to test data for the acoustic field around a vehicle that originates from an airborne noise source. Good correlation is demonstrated between numerical predictions and test data.

Event Data Recorder Pre-Crash Data Sources for General Motors Vehicles

The Event Data Recorder (EDR) found in some 1994 model year and newer General Motors (GM) passenger vehicles has the ability to record up to five seconds of pre-crash data. Such as vehicle speed, engine speed, percent throttle application and brake application before a predetermined deceleration event as well as crash data such as delta-v’s. The pre-crash and crash data can be downloaded by properly equipped and trained personnel using the Vetronix Crash Data Retrieval (CDR) System. However, this data must not simply be taken at face value; the Accident Analyst must be aware of the nature of the differing types and sources of the data, and must ensure that the systems supplying the data was in a normal operating mode and not in a default mode or in a “limp home” mode due to pre existing problems. This paper discusses how different environments and scenarios that the vehicle can be operated in changes how the vehicle will respond to driver inputs thus effecting pre-crash data recorded by the Event Data Recorder.

Development of a Stochastic Approach for Vehicle FE Models

This paper describes the development of a mathematical model capable of providing realistic simulations of vehicle crashes by accounting for uncertainty in the model input parameters. The approach taken was to couple advanced and efficient probabilistic and reliability analysis methods with well-established, high fidelity finite element and occupant modeling software. Southwest Research Institute has developed probabilistic analysis software called NESSUS. This code was used as the framework for a stochastic crashworthiness FE model. The LS-DYNA finite element model of vehicle frontal offset impact and the MADYMO model of a 50th percentile male Hybrid III dummy were integrated with NESSUS to comprise the crashworthiness characteristics. The system reliability of the vehicle is computed by defining ten acceptance criteria performance functions; four occupant injury criteria and six compartment intrusion criteria. The reliability for each acceptance criteria was computed using NESSUS to identify the dominant acceptance criteria of the original design. The femur axial load acceptance criteria event has the lowest reliability (46%) followed by the HIC event (58%) and the door aperture closure event (73%). One approach to improve the reliability is to change vehicle parameters to improve the reliability for the dominant criteria. However, a parameter change such as vehicle strength/stiffness may have a beneficial effect on certain acceptance criteria but be detrimental to others. A system reliability analysis was used to include the contribution of all acceptance criteria to correctly quantify the vehicle reliability and identify important parameters. A redesign analysis was performed using the computed probabilistic sensitivity factors. These sensitivities were used to identify the most effective changes in model parameters to improve the reliability. A redesign using 11 design modifications was performed that increased the original reliability from 23% to 86%. Several of the design changes include increasing the rail material yield strength and reducing its variation, reducing the variation of the bumper and rail installation tolerances, and increasing the rail weld stiffness and reducing its variation. The results show that major reliability improvements for occupant injury and compartment intrusion can be realized by certain specific modifications to the model input parameters. A traditional (deterministic) method of analysis would not have suggested these modifications.

Probabilistic Analyses for the Performance Characteristics of the Main Bearings in an Operating Engine Due to Variability in Bearing Properties

This paper presents the development of surrogate models (metamodels) for evaluating the bearing performance in an internal combustion engine. The metamodels are employed for performing probabilistic analyses for the engine bearings. The metamodels are developed based on results from a simulation solver computed at a limited number of sample points, which sample the design space. An integrated system-level engine simulation model, consisting of a flexible crankshaft dynamics model and a flexible engine block model connected by a detailed hydrodynamic lubrication model, is employed in this paper for generating information necessary to construct the metamodels. An optimal symmetric Latin hypercube algorithm is utilized for identifying the sampling points based on the number and the range of the variables that are considered to vary in the design space. The development of the metamodels is validated by comparing results from the metamodels with results from the actual simulation models over a large number of evaluation points. Once the metamodels are established they are employed for performing probabilistic analyses. The initial clearance between the crankshaft and the bearing at each main bearing and the oil viscosity comprise the random variables in the probabilistic analyses. The maximum oil pressure and the percentage of time (the time ratio) within each cycle that a bearing operates with oil film thickness less than a user defined threshold value at each main bearing constitute the performance variables of the system. The availability of the metamodels allows comparing the performance of several probabilistic methods in terms of accuracy and computational efficiency. A useful insight is gained by the probabilistic analysis on how variability in the bearing characteristics affects its performance.

On the Challenges of Quieting a Freight Locomotive Cab Interior

The primary purpose of this paper is to discuss some of the challenges—both from an engineering standpoint and economically—facing the railway industry in improving the noise and vibration characteristics in locomotive cabs. To this end, we will first establish the vibration characteristics of a typical locomotive cab used in freight locomotives in North America. Next, we will evaluate the effect of separating the cab structure from the reminder of the locomotive structure by elastomeric mounts. This cab configuration is commonly referred to as “soft-mounted cab,” in contrast to a “hard-mounted cab,” which is rigidly attached to the remainder of the locomotive structure. The structural dynamics of a production locomotive cab is studied in a laboratory environment. The cab is excited by a hydraulic actuator, in a manner closely resembling field inputs. After establishing the baseline vibrations of the cab, the study presents the results of vibration tests for the soft mounted cab. A comparison between the hard-mounted and soft-mounted cabs indicate that soft mounting the locomotive cab can result in substantial noise and vibration reduction at all locations in the cab, and therefore provide: • more crew comfort, • less equipment damage, and • manufacturing cost savings. The paper will also discuss the effect of the measures that are needed for quieting the cab, such as soft mounting it, on the locomotive manufacturers from an engineering and business perspective.

Air-Assisted Marine Vehicles for Future Use in Transoceanic Transportation

The technical aspects of two types of advanced marine vehicles, Air Cavity Ship and Wing-In-Ground, are considered for future use in transoceanic transportation. Both concepts utilize the air medium to improve technical and economic characteristics of transportation means. The air is supplied under the bottom hull sections of the Air Cavity Ship, reducing the overall wetted surface and consequently hydrodynamic drag. A contact with water is completely eliminated in the case of the Wing-in-Ground, which moves above the water. This results in enhancing the lift-drag ratio in comparison with a flight in the open air. The principles, experience, and research opportunities on the way to make these concepts applicable for transportation are discussed.

Advances in Actuation Systems to Improve Vehicle Performance and Safety

Actuation and modeling for drive-by-wire applications are discussed. Previous work in advanced actuation for two automotive systems, active suspension and camless engines, is surveyed, outlining the major advancements throughout the previous decade. More recent research in these areas is discussed and focuses on recent improvements to system modeling and design. Specifically, a four-corner suspension model and a piezoelectric piloted hydraulic actuator for engine valve actuation are introduced. The four-corner suspension model addresses the three-dimensional parameters associated with active suspension design and improves upon the accepted quarter-car model. The piezoelectric based camless engine actuator is introduced as the next generation of camless engine actuation systems and addresses control issues through the relationship between input voltage and piezoelectric displacement.

Advances in the Railroad Locomotive Crashworthiness

The paper describes locomotive and fuel tank crashworthiness research being conducted by the Federal Railroad Administration for improved safety of the locomotive crew under collision scenarios. The research involves static and dynamic impact strength evaluations of locomotive structural components. These evaluations which are based on full scale tests and simulations using finite element analysis are described in this paper. Correlations between the test and simulation results are also presented in some cases.