David Anthony Wagner

Nonlinear analysis of automotive door weatherstrip seals

Abstract Automotive door system weatherstrip seals play a major role in determining door closing effort, isolating the passenger compartment from water and reducing the wind noise inside the vehicle. Using nonlinear finite element analysis, a seal cross section can be analyzed for compression load deflection (CLD) behavior, contact pressure distribution and aspiration due to a pressure differential across the seal. The seal CLD response, the deformed shape during compression, the contact pressure distribution and the aspiration pressure difference are all important seal performance factors that are considered in door weathership seal design. The analyses described herein and the associated design evaluations can be performed before any prototype hardware is developed if sufficient geometry and material property information is available.

Calibrating material parameters to model the thin-walled components made of die cast AM60B magnesium alloy

As a novel lightweight metal, die cast AM60B magnesium alloy continues to be considered as a potential replacement for steel in certain automotive components. However, proper numerical model representing this alloy has not yet been fully explored. Thus, an optimisation methodology was developed to calibrate the material parameters needed for four available material laws, namely, MAT_99, MAT_81, MAT_24 and MAT_107 in LS-DYNA explicit FEA package (LSTC, Livermore, CA). The basic idea was to combine computations with a set of optimisation procedures to systematically adjust various material parameters until the calculated mechanical responses optimally match those measured experimentally. The optimisation was based on uni-axial tensile coupon tests at different nominal strain rates, ranging from quasi-static to 800 s−1. The optimisation results were evaluated using component experimental data from both slow- and high-speed axial crushing and quasi-static four-point bending tests of a thin-walled top-hat structure, and then quantified using a gross correlation index (GCI). Calculated results indicate that using the material constants generated from this set of procedures, all of the four material models replicated experimentally obtained stress–strain curves well, and yielded similar values of GCI (The difference was less than 4%). But only MAT_99 could accurately capture the damage patterns as observed in structural component experimental tests, thus being considered the best among the four material types studied. It is also concluded that the damage behaviour of AM60B alloy is sensitive to the strain hardening model and failure criterion selected.

Application of AM60B magnesium alloy material model to structural component crush analysis

Simulations of energy absorbing structural components made of die cast magnesium alloy AM60B under axial crush and bending conditions require determination of accurate material parameters when using finite element (FE) analysis. This paper presents two optimisation-based methodologies to calibrate material parameters for such simulations. The processes combine computations with a set of optimisation procedures to systematically adjust the material input parameters until the calculated mechanical responses optimally matched those measured experimentally. Results indicate that material input generated from these procedures replicates both experimentally obtained forcedeflection curves and material fracture pattern well, thus enhancing model predictability in crashworthiness using AM60B.

Elongation Variability of AM60 Die Cast Specimens

Tensile properties of die cast magnesium AM60 were investigated by testing tensile bar specimens obtained from three sources. The first series of tensile bars were cut from eight locations from multiple copies of a die cast magnesium AM60 automotive instrument panel beam. The second series were cut from six-inch square AM60 die cast plates in both the parallel and perpendicular to the flow direction. The last series of specimens were die cast AM60 tensile bars. The measured yield stress did not significantly depend on the specimen source and matched published values. However, the elongation as determined by the engineering strain at break in the tensile test varied significantly for samples cut from the automotive instrument panel beams and those cut from the six-inch by six-inch plates. The elongation remained constant for the cast tensile bars. Statistic General Linear Models were used to study the effect of casting conditions on both the yield stress and the strain at break. Sample location within the beams was the main factor for the material property variation.Copyright

Modeling foam damping materials in automotive structures

Foam damping materials judiciously placed in automotive structures efficiently reduce the vibration amplitudes of large, relatively flat exterior body panels such as the hood, roof, deck lid (trunk) and door skin. These polymer foams (typically epoxy or vinyl) have mechanical properties that depend on the foam homogeneity, degree of expansion, temperature and frequency of excitation. Standard methods for determining true bulk mechanical properties, such as Youngs modulus, shear modulus and damping terms, are discussed along with methods for determining engineering estimates of the properties as used in automotive applications. Characterizing these foam damping materials in a component or full body finite element structural model as discrete springs and dashpots provides an accurate and economical means to include these features. Example analyses of the free vibrations and forced response of a hood are presented accompanied by test data that demonstrate the accuracy of the structural model. A parametric study investigates the effect of foam material stiffness and damping properties on hood vibration amplitudes under dynamic air loading. A methodology is discussed to reduce the hood vibration level under cross-wind conditions to an acceptable level with the use of foam materials.

Comparative LCA Study of Lightweight Auto Parts of MMLV Mach‐I Vehicle as Per ISO 14040/44 LCA Standards and CSA Group 2014 LCA Guidance Document for Auto Parts

Weight reduction in automotive design and manufacture is a priority across the industry, as strict new regulations push for greater vehicle efficiency and CO2 reduction in the US, Europe and Asia.

A viscoelastic analogy for solving 2-D electromagnetic problems

Abstract Solving a viscoelastic material boundary value problem provides the voltage, electric field and displacement current results to a certain class of electromagnetic problems. By means of the electromagnetic-viscoelastic analogy described herein, a solid mechanics finite element program can analyze a two-dimensional harmonic oscillation (constant frequency) electromagnetic problem for “lossy” dielectric materials. For this special class of electromagnetic field problems, the Maxwell equations reduce to a two-dimensional Laplace equation with complex coefficients. This form identically matches the viscoelasticity field equations. This paper develops the electromagnetic-viscoelastic analogy from the basic governing field equations. The analogy is implemented in ABAQUS, a general solid mechanics finite element program. Simple one- and two-dimensional examples prove the accuracy and usefulness of the analogy.

NVH Performance of Lightweight Glazing Materials in Vehicle Design

Fuel economy and NVH (noise, vibration, and harshness) performance of vehicles are important parameters in a customer’s vehicle purchase decision. Lightweight vehicle designs are necessary to help with fuel economy improvements. In this research work, the weight saving potential and NVH performance of different lightweight glazing materials are investigated to help the lightweight design effort. The lightweight glazing materials included in this study are “Material A”, “Material B”, “Material C” with regular lamination, and “Material C” with acoustic lamination. The results of this research work indicate that the lightweight glazing materials have 30% to 40% weight saving potentials without NVH penalty. These materials have much higher damping properties than conventional tempered glass so they can compensate for the mass reduction influence on vehicle NVH. The tire patch noise reduction, vehicle transparency, and wind noise results of “Vehicle A” tested with different lightweight backlight designs indicate that there is almost no acoustic response difference between the tempered glass and other lightweight alternative backlight designs. Damping loss factor measurements indicate that “Material C” with acoustic PVB (polyvinyl-butyral) has the highest damping loss factor value of 37%. The “Material C” backlight with acoustic PVB is the best among all the lightweight alternatives and brings 29% weight reduction without any NVH degradation. Statistical Energy Analysis (SEA) results also indicate that it is possible to eliminate the NVH degradation by using glazing material having high material damping properties or using laminated panels having damping loss values in the range of 6% to 20%. In this paper, we only address the weight reduction and NVH performance of light weight glazing materials but not the costs or any potential assembly procedure changes.Copyright

Service Life Heat Exposure Effects and ALuminm Aluminum Extrusion Crash Properties Relationship Under Static Axial Loading

Relationship between service life heat exposure and extruded aluminum structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum alloy extrusions each of which is subjected to two heat treatments. The aluminum extrusion investigated are 6063T6, 6061T6, 6260T6, 6014T6, and 7129T6. The two heat treatments are 177°C for 30 minutes and 200°C for 24 hours. The 200°C/24 hours treatment represents the most severe thermal exposure i.e. components adjacent to exhaust pipes and manifolds. The 200°C heat treatment is in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. These ten crash members were subjected to static axial crushing at a speed of 25.4 mm/minute (1 in/min). Force-time data was collected and responses were plotted for all tests. Force-displacement responses were integrated for the crush energy management and mean axial crush load for each of the aluminum extruded crash members. Bar charts were then generated to describe the crush loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Severe service life simulated heat exposure was found to affect the mean crush load and crush energy management of the aluminum structural crush members. The heat exposure effects on the crashworthiness of the extruded aluminum members ranged from a reduction of 8% to over 20% in the mean crush load and crush energy management with highest variation observed with the 6260T6 aluminum extrusion.Copyright

Aluminum High Pressure Vacuum Die Casting Applications for the Multi Material Lightweight Vehicle Program (MMLV) Body Structure

Vehma/Cosma Engineering a Division of Magna International, the U.S. Department of Energy and Ford Motor Company initiated the Multi Materials Lightweight Vehicle (MMLV) Project in 2012. The goal was to design and build prototype vehicles, maintaining donor vehicle architectural space in an effort to reduce mass relative to a 2002 baseline vehicle target. The result of this study was a 23.5% reduction in vehicle weight compared to the current donor vehicle.