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With deflected-disc dampers, digressive force-velocity shapes are achieved via the combined effects of disc stack stiffness and hub-offset. The degree of digressiveness can be adjusted to alter vehicle performance by changing the proportion of these parameters. Optimizing this relationship can yield substantial vehicle performance improvements, but the time consuming iterative process of developing a new disc stack for each hub-offset discourages experimentation. To enable more efficient digressiveness comparisons, a regression-based computational method has been developed which converts disc stack stiffness from one hub-offset to other offsets directly, without iteration. Once an initial disc stack for one offset has been tuned by traditional methods, stacks for other offsets can be calculated that maintain overall damper control.

A simulation methodology is developed for the Constant Radius Constant Speed (CRCS) analysis to predict the ISO4138 [1] road test performance. The CRCS analysis can be used to predict the vehicle steady-state handling characteristics such as understeer, rear cornering compliance, and roll gradient, etc. The Yaw-Rate Control methodology is applied to replace the traditional driver-in-the-loop path-following approaches. Comparing to the path-following approaches, the proposed method is simpler to use, more efficient, accurate, and robust.

The preform annealing process is a two-stage stamping method for shaping non age-hardenable (i.e. 5000 series) aluminum sheet panels in which the panel is heat treated in between the two steps to improve overall formability of the material. The intermediate annealing heat treatment eliminates the cold work accumulated in the material during the first draw. The process enables the ability to form more complex parts than a conventional aluminum stamping process. A demonstration of local annealing for this process was conducted to form a one-piece aluminum liftgate inner panel for a large sport utility vehicle using the steel product geometry without design concessions. In prior work, this process was demonstrated by placing the entire panel in a convection oven for several minutes to completely anneal the cold work.

Generally linear finite element analysis (FEA) is used to predict fatigue life of spot welded joints in a vehicle body structure. Therefore, the effect of plastic deformation at the vicinity of the spot welded joints is not included on fatigue prediction. This study introduces a simple technique to include the plastic deformation effect without performing elastic-plastic finite element analysis. The S-N curve obtained from fatigue test results is modified to consider this effect. Tensile strength test results of spot welded joint specimens were utilized to find the load range for FEA equivalent to the applied load range for fatigue tests. To demonstrate the proposed approach, fatigue test results of advanced high strength steels (AHSS) for lap-shear and coach peel specimens were used. Both the specimen types were tested at various constant amplitudes with the load ratios of R=0.1 and 0.3.

The ability to make accurate decisions concerning early body-in-white architectures is critical to an automaker since these decisions often have long term cost and weight impacts. We address this need with a methodology which can be used to assist in body architecture decisions using process-based technical cost modeling (TCM) as a filter to evaluate alternate designs. Despite the data limitations of early design concepts, TCM can be used to identify key trends for cost-effectiveness between design variants. A compact body-in-white architecture will be used as a case study to illustrate this technique. The baseline steel structure will be compared to several alternate aluminum intensive structures in the context of production volume.

Understanding the flow characteristics and, especially, how the aerodynamic forces are influenced by the changes in the vehicle body shape, are very important in order to improve vehicle aerodynamics. One specific goal of aerodynamic shape optimization is to predict the local shape sensitivities for aerodynamic forces. The availability of a reliable and efficient sensitivity analysis method will help to reduce the number of design iterations and the aerodynamic development costs. Among various shape optimization methods, the Adjoint Method has received much attention as an efficient sensitivity analysis method for aerodynamic shape optimization because it allows the computation of sensitivity information for a large number of shape parameters simultaneously.

General Motors (GM), OnStar and the University of Michigan International Center for Automotive Medicine (ICAM) have formed a partnership to investigate and analyze real world rollover crashes involving GM vehicles equipped with rollover sensing technology and rollover-capable roof rail airbag systems. Candidates for the study are initially identified by OnStar, who receive notification of a rollover crash through the vehicle's Automatic Crash Response system. If the customer agrees to participate in the study, medical, vehicle and crash scene information are quickly gathered. This information is then reviewed by the medical and GM engineering communities to provide field relevant learning on injury mechanisms and vehicle system performance in rollover events. This paper provides a detailed review of the field case studies collected to date.

An air suspension system can consist of many different components. These components include an air compressor, air springs, pneumatic solenoid valves, height sensors, electronic control unit, air reservoir, air lines, pressure sensor, temperature sensor, etc. The system could be designed as a 2-corner rear air suspension or a 4-corner air suspension. In this paper, the pneumatic models of air suspension systems are presented. The suspension system models are implemented in AmeSim. The suspension controls are implemented using Matlab/Simulink. The compressor was modeled using the standard AmeSim element with known mass flow rate as a function of pressure ratio. Air lines were modeled using a friction submodel of pneumatic pipe and control (isolation) valves are modeled using 2 position, 2 port pneumatic servo valves. The air spring is modeled as a single pneumatic chamber, single rod jack with spring assistance to account for spring nonlinearities.

A comprehensive analysis has been performed for floating bearings applied in a turbocharger. It is found that Couette power loss for a full-floating bearing (the floating ring rotates) decreases with increasing inner and outer clearances, while its Poiseuille power loss increases with increasing inner and outer film clearances. In comparison with a semi-floating bearing (the floating ring does not rotate), a full-floating bearing can reduce both Couette and Poiseuille power losses. However, floating bearing is found to have a smaller minimum film thickness for a given dynamic loading from rotor-dynamics. The total power loss reduction for typical full-floating bearings ranges from 13% to 27%, which matches well with some published experimental data. In general, the speed ratio increases with increasing outer film clearance, while it decreases with increasing inner film clearance because of shear stresses on the outer and inner film.

Presented in the paper is a comprehensive analysis for floating piston pin. It is more challenging because it is a special type of journal bearing where the rotation of the journal is coupled with the friction between the journal and the bearing. In this analysis, the multi-degree freedom mass-conserving mixed-EHD equations are solved to determine the coupled pin rotation and friction. Other bearing characteristics, such as minimum film thickness, pin secondary motions in both connecting-rod small-end bearing and piston pin-boss bearing, power loss etc are also determined. The mechanism for floating pin to have better scuffing resistance is discovered. The theoretical and numerical model is implemented in the GM internal software FLARE (Friction and Lubrication Analysis for Reciprocating Engines).

An engineering approach was developed to extract the failure plastic strain, thinning failure strain, and major in plane failure strain for finite element simulation applications. This approach takes into account the failure strain dependency on the element size when element deletion scheme is invoked in the simulation of material fracture. Both localized necking fracture and tensile shear fracture can be predicted when appropriate elements and material models are used in LS-DYNA simulations. This leads to a more accurate prediction of fracture and tearing in the finite element simulation of vehicle structure and crash loading conditions.

An extruded Mg-Al-Mn (AM30) magnesium alloy was subjected to uniaxial compression along the extrusion direction (ED) and the extrusion radial direction (RaD) at 450 °C and different strain rates. The microstructure and texture of the AM30 alloy under different deformation conditions were examined. Texture evolution was characterized by electron backscatter diffraction (EBSD). The activity of different deformation modes including twinning were simulated using the visco-plastic self-consistent (VPSC) and the simplistic Sachs polycrystal plasticity models. The results show that the microstructure and the mechanical property of the Mg alloy strongly depend on the strain rate, with twinning activated at strain rates >0.5 s−1. Dynamic recrystallization and twinning interacted with each other and affected the final microstructure and mechanical property of the magnesium alloy.

Today, nearly half of the world population lives in urban areas. As the world population continues to migrate to urban areas for increased economic opportunities, addressing personal mobility challenges such as air pollution, Greenhouse Gases (GHGs) and traffic congestion in these regions will become even a greater challenge especially in rapidly growing nations. Road transportation is a major source of air pollution in urban areas causing numerous health concerns. Improvements in automobile technology over the past several decades have resulted in reducing conventional vehicle tailpipe emissions to exceptionally low levels. This transformation has been attained mainly through advancements in engine and transmission technologies and through partial electrification of vehicles. However, the technological advancements made so far alone will not be able to mitigate the issues due to increasing GHGs and air pollution in urban areas.

One of the most critical and important fracture mechanisms in a FMVSS207/210/225[1] test is the pull-thru of bolts from the body structure or spot weld separation. There are no analytically proven methods of making a judgment of pull-thru occurring except through evaluation of the plastic strain or through the thickness strain value around projection welds on Weld nut/stud bolt or spot welds. Therefore it is essential to have accurate criteria to evaluate the pull-thru. During elastic deformation, the sheet steel deforms while the quasi-static force is being applied and then returns to its original shape when the force is released. But when the force causes a stress that exceeds the yield strength, the sheet steel will permanently elongate with each additional unit of force applied, and it will not return to its original shape and size.

Insulation coordination requirements for electrical equipment applications are defined in various standards. The standards are defined for application to stationary mains connected equipment, like IT, power supply or industrial equipment. Protection from an electric shock is considered the primary hazard in these standards. These standards have also been used in the design of various automotive components. IEC 60664-1 is an example of the standard. Automobiles are used across the world, in various environments and in varied usage by the customers. Automobiles need to consider possible additional hazards including electric shock. This paper will provide an overview of how to adapt these standards for automotive application in the design of High Voltage (HV) automotive components, including High Voltage batteries and other HV components connected to the battery. The basic definitions from the standards and the principles are applied for usage in automotive applications.

The GD₃ or GD Cubed method of problem prevention has been applied to product changes and to test results at the component, subsystem and vehicle level. GD₃ stands for Good Design - Good Discussion - Good Dissection. Good Discussion of changes (Design Review Based on Failure Mode) identifies BUDS of PROBLEMS that may arise from interfaces and areas of change. Good Dissection (Design Review Based on Test Results) is applied to physical test samples during and after tests to identify Buds of Problems that may not be obvious from inspection of the parts or test results. The paper first describes implementation of the GD₃ principles and methods supporting Good Discussion (DRBFM) and Good Dissection, and then discusses how they are applied and embedded in the Vehicle Development Process at General Motors Co.

The internal flow in an injector is greatly affected by cavitation formation, and this in turn impacts the spray characteristics of diesel injectors. In the current work, the performance of the Homogeneous Relaxation Model (HRM) in simulating cavitation inside a diesel injector is evaluated. This model is based on the assumption of homogeneous flow, and was originally developed for flash boiling simulations. However, the model can potentially simulate the spectrum of vaporization mechanisms ranging from cavitation to flash boiling through the use of an empirical time scale which depends on the thermodynamic conditions of the injector fuel. A lower value of this time scale represents a lower deviation from thermal equilibrium conditions, which is an acceptable assumption for small-scale cavitating flows. Another important advantage is the ability of this model to be easily coupled with real fuel models.

This paper examines Smart Electric Power Management as it pertains to when the vehicle charging system is active. Over the past decade there have been several factors at play which have stressed the demands placed upon the vehicle electrical power system. Many of these factors present challenges to electrical power that are at cross-purposes with one another. For example, demands of new and existing electrical loads, customer expectations about load performance and battery life, and the push by governments' world-wide for increased fuel economy (FE) and reduced CO2 emissions all have direct impact and can be directly impacted by decisions made in electric power design. As the electrification of the vehicle has progressed we now have much more specific vehicle state data available and the means to share this information among on-board computers through serial data link connectivity.

Three different acoustic finite element models of an automobile passenger compartment are developed and experimentally assessed. The three different models are a traditional model, an improved model, and an optimized model. The traditional model represents the passenger and trunk compartment cavities and the coupling between them through the rear seat cavity. The improved model includes traditional acoustic models of the passenger and trunk compartments, as well as equivalent-acoustic finite element models of the front and rear seats, parcel shelf, door volumes, instrument panel, and trunk wheel well volume. An optimized version of the improved acoustic model is developed by modifying the equivalent-acoustic properties. Modal analysis tests of a vehicle were conducted using loudspeaker excitation to identify the compartment cavity modes and sound pressure response to 500 Hz to assess the accuracy of the acoustic models.

Conventional HVAC systems adjust the position of a temperature door, to achieve a required air temperature discharged into the passenger compartment. Such systems are based upon the fact that a conventional (non-hybrid) vehicle's engine coolant temperature is controlled to a somewhat constant temperature, using an engine thermostat. Coolant flow rate through the cabin heater core varies as the engine speed changes. EREVs (Extended Range Electric Vehicles) & PHEVs (Plug-In Hybrid Electric Vehicles) have two key vehicle requirements: maximize EV (Electric Vehicle) range and maximize fuel economy when the engine is operating. In EV mode, there is no engine heat rejection and battery pack energy is consumed in order to provide heat to the passenger compartment, for windshield defrost/defog and occupant comfort. Energy consumption for cabin heating must be optimized, if one is to optimize vehicle EV range.