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Journal Article

Applying Virtual Statistical Modeling for Vehicle Dynamics

2010-04-12
2010-01-0019
Dimensional variation simulation is a computer aided engineering (CAE) method that analyzes the statistical efforts of the component variation to the quality of the final assembly. The traditional tolerance analysis method and commercial CAE software are often based on the assumptions of the rigid part assembly. However, the vehicle functional attributes, such as, ride and handling, NVH, durability and reliability, require understanding the assembly quality under various dynamic conditions while achieving vehicle dimensional clearance targets. This paper presents the methods in evaluating and analyzing the impacts of the assembly variations for the vehicle dynamic performance. Basic linear tolerance stack method and advanced study that applies various CAE tools for the virtual quality analysis in the product and process design will be discussed.
Journal Article

Composite Thermal Model for Design of Climate Control System

2014-04-01
2014-01-0687
We propose a composite thermal model of the vehicle passenger compartment that can be used to predict and analyze thermal comfort of the occupants of a vehicle. Physical model is developed using heat flow in and out of the passenger compartment space, comprised of glasses, roof, seats, dashboard, etc. Use of a model under a wide variety of test conditions have shown high sensitivity of compartment air temperature to changes in the outside air temperature, solar heat load, temperature and mass flow of duct outlet air from the climate control system of a vehicle. Use of this model has subsequently reduced empiricism and extensive experimental tests for design and tuning of the automatic climate control system. Simulation of the model allowed several changes to the designs well before the prototype hardware is available.
Journal Article

CAE Applications and Techniques used in Calculating the Snaps Insertions and Retentions Efforts in Automotive Trims

2014-04-01
2014-01-1032
A snap-fit is a form-fitting joint, which is used to assemble plastic parts together. Snap-fits are available in different forms like a projecting clip, thicker section or legs in one part, and it is assembled to another part through holes, undercuts or recesses. The main function of the snap-fit is to hold the mating components, and it should withstand the vibration and durability loads. Snap-fits are easy to assemble, and should not fail during the assembling process. Based on the design, these joints may be separable or non-separable. The non- separable joints will withstand the loads till failure, while separable joints will withstand only for the design load. The insertion and the retention force calculation for the snaps are very essential for snap-fit design. The finite element analysis plays a very important role in finding the insertion and the retention force values, and also to predict the failure of the snaps and the mating components during this process.
Journal Article

High-Fidelity Transient Thermal Modeling of a Brake Corner

2016-09-18
2016-01-1929
There is an increasing interest in transient thermal simulations of automotive brake systems. This paper presents a high-fidelity CFD tool for modeling complete braking cycles including both the deceleration and acceleration phases. During braking, this model applies the frictional heat at the interface on the contacting rotor and pad surfaces. Based on the conductive heat fluxes within the surrounding parts, the solver divides the frictional heat into energy fluxes entering the solid volumes of the rotor and the pad. The convective heat transfer between the surfaces of solid parts and the cooling airflow is simulated through conjugate heat transfer, and the discrete ordinates model captures the radiative heat exchange between solid surfaces. It is found that modeling the rotor rotation using the sliding mesh approach provides more realistic results than those obtained with the Multiple Reference Frames method.
Journal Article

Effect of Operational Testing and Trim Manufacturing Process Variation on Head Injury Criterion in FMVSS 201 Tests

2008-04-14
2008-01-1218
This paper analyzes the difference in impact response of the forehead of the Hybrid III and THOR-NT dummies in free motion headform tests when a dummy strikes the interior trim of a vehicle. Hybrid III dummy head is currently used in FMVSS201 tests. THOR-NT dummy head has been in development to replace Hybrid III head. The impact response of the forehead of both the Hybrid III dummy and THOR dummy was designed to the same human surrogate data. Therefore, when the forehead of either dummy is impacted with the same initial conditions, the acceleration response and consequently the head Injury criterion (HIC) should be similar. A number of manufacturing variables can affect the impacted interior trim panels. This work evaluates the effect of process variation on the response in the form of Head Injury Criterion (HIC).
Journal Article

A Springback Compensation Study on Chrysler 300C Stamping Panels Using LS-DYNA®

2008-04-14
2008-01-1443
Springback compensation studies on a few selected auto panels from the hot selling Chrysler 300C are presented with details. LS-DYNA® is used to predict the springback behavior and to perform the iterative compensation optimization. Details of simulation parameters using LS-DYNA® to improve the prediction accuracy are discussed. An iterative compensation algorithm is also discussed with details. Four compensation examples with simulation predictions and actual panel measurement results are included to demonstrate the effectiveness of LS-DYNA® predictions. An aluminum hood inner and a high strength steel roof bow are compensated, constructed and machined based on simulation predictions. The measurements on actual tryout panels are then compared with simulation predictions and good correlations were achieved. Iterative compensation studies are also done on the aluminum hood inner and the aluminum deck lid inner to demonstrate the effectiveness of LS-DYNA® compensation algorithm.
Journal Article

Computer Simulation of Automotive Air Conditioning - Components, System, and Vehicle: Part 2

2008-04-14
2008-01-1433
In 1972, the first SAE paper describing the use of computer simulation as a design tool for automotive air conditioning was written by these authors. Since then, many such simulations have been used and new tools such as CFD have been applied to this problem. This paper reviews the work over that past 35 years and presents several of the improvements in the basic component and system models that have occurred. The areas where “empirical” information is required for model support and the value of CFD cabin and external air flow modeling are also discussed.
Journal Article

Quality Inspection of Spot Welds using Digital Shearography

2012-04-16
2012-01-0182
Spot Welding is an important welding technique which is widely used in automotive and aerospace industry. One of the keys of checking the quality of the welds is measuring the size of the nugget. In this paper, the Shearographic technique is utilized to test weld joint samples under the thermal loading condition. The goal is to identify the different group of the nuggets (i.e. small, middle, and large sizes, which indicate the quality of spot welds). In the experiments, the sample under test is fixed by a magnet method from behind at the four edges. Thermal loading was applied in the back side and the sample is inspected using the digital Shearographic system in the front side. Results show the great possibility of classifying the nugget size into three groups and the measurement is well repeatable.
Technical Paper

A Predictive Process for Spring Failure Rates in Automotive Parts Applications

1991-02-01
910356
This paper discusses an analytical technique for computing the failure rate of steel springs used in automotive part applications. Preliminary computations may be performed and used to predict spring failure rates quickly at a very early stage of a product development cycle and to establish program reliability impact before commitment. The analytical method is essentially a combination of various existing procedures that are logically sequenced to compute a spring probability of failure under various operational conditions. Fatigue life of a mechanical component can be computed from its S-N curve. For steels, the S-N curve can be approximated by formulae which describe the fatigue life as a function of its endurance limit and its alternating stress. Most springs in service are preloaded and the actual stress fluctuates about a mean level. In order to compute an equivalent alternating stress with zero mean, an analytical method based on the Goodman Diagram is used.
Technical Paper

Statistical Energy Analysis of Airborne and Structure-Borne Automobile Interior Noise

1997-05-20
971970
This paper describes the application of Statistical Energy Analysis (SEA) and Experimental SEA (ESEA) to calculating the transmission of air-borne and structure-borne noise in a mid-sized sedan. SEA can be applied rapidly in the early stages of vehicle design where the degree of geometric detail is relatively low. It is well suited to the analysis of multiple paths of vibrational energy flow from multiple sources into the passenger compartment at mid to high frequencies. However, the application of SEA is made difficult by the geometry of the vehicle's subsystems and joints. Experience with current unibody vehicles leads to distinct modeling strategies for the various frequency ranges in which airborne or structure-borne noise predominates. The theory and application of ESEA to structure-borne noise is discussed. ESEA yields loss factors and input powers which are combined with an analytical SEA model to yield a single hybrid model.
Technical Paper

Lead-time Reduction in Stamping CAE and Die Face Development using Massively Parallel Processing in Forming Simulations

2007-04-16
2007-01-1678
Since 1997, General Motors Body Manufacturing Engineering - Die Engineering Services (BME-DES) has been working jointly with our software vendor to develop and implement a parallel version of stamping simulation software for mass production analysis applications. The evolution of this technology and the insight gained through the implementation of DMP/MPP technology as well as performance benchmarks are discussed in this publication.
Technical Paper

Friction Stir Welding of Aluminum for Automotive Closure Panel Applications

2008-04-14
2008-01-0145
Friction stir welding (FSW) shows advantages for joining lightweight alloys for automotive applications. In this research, the feasibility of friction stir welding aluminum for an automotive component application was studied. The objective of this research was to improve the Friction Stir Spot Welding (FSSW) technique used to weld an aluminum closure panel (CP). The spot welds were made using the newly designed swing-FSSW technique. In a previous study (unpublished), the panel was welded from the thin to thick side using both an 8 mm and a 10 mm diameter tool. The 10 mm tool passed various fatigue tests; however, the target was to improve performance of the 8 mm tool, especially to increase the number of cycle before the first crack appearance during fatigue testing. In this study fatigue tests and static strength was recorded for weld specimens that were welded from thick-to-thin with an 8 mm diameter tool.
Technical Paper

Adaptive nth Order Lookup Table used in Transmission Double Swap Shift Control

2008-04-14
2008-01-0538
The new Chrysler six-speed transaxle makes use of an underdrive assembly to extend a four-speed automatic transmission to six-speed. It is achieved by introducing double-swap shifts. During double-swap shift, learning the initial clutch torque capacity of the underdrive assembly's subsystem has a direct impact on the shift quality. A new method is proposed to compute and learn the initial clutch torque capacity of the releasing element. In this paper, we will outline a new mathematical method to compute and learn the accurate starting point of the clutch torque capacity for double swap shift control. The performance of the shift is demonstrated and the importance of the adaptation to shift quality is highlighted. An nth order lookup table is presented; this table contains n rows and m columns. Every row defines a relationship between the dependent variable such as actuator duty cycle and one independent variable such as transmission oil temperature, input torque or battery voltage.
Technical Paper

Transient One-Dimensional Thermal Analysis of Automotive Components for Determination of Thermal Protection Requirements

2008-04-14
2008-01-0733
During initial phases of vehicle development process, it is usually required to understand the temperature profile for all components. It is usually more effective and less costly if the thermal issues are determined and addressed before actual vehicles are built. Computational Fluid Dynamics (CFD) analysis tools are typically used for thermal management of the vehicle environment. However, for transient thermal analysis problems, running a full CFD requires solving the mass, momentum, and energy equations. This typically requires a lengthy computation time and extensive computer resources. The problem becomes more challenging when trying to conduct CFD analysis for several design iterations and for different duty cycles that may be of a transient nature. Therefore, the application of one-dimensional analysis early in the development phase can help point out the areas of prime concern.
Technical Paper

Application of Tuned Mass Damper to Address Discrete Excitation Away From Primary Resonance Frequency of a Structure

2009-05-19
2009-01-2125
Tuned mass dampers (TMDs) or vibration absorbers are widely used in the industry to address various NVH issues, wherein, tactile-vibration or noise mitigation is desired. TMDs can be classified into two categories, namely, tuned-to-resonance and tuned-to-discrete-excitation. An overwhelming majority of TMD applications found in the industry belong to the tuned-to-resonance category, so much of information is available on design considerations of such dampers; however, little is published regarding design considerations of dampers tuned-to-discrete-excitation. During this study, a problem was solved that occurred at a discrete excitation frequency away from the primary resonance frequency of a steering column-wheel assembly. A solution was developed in multiple stages. First the effects of various factors such as mass and damping were analyzed by using a closed-form solution.
Technical Paper

Optimizing the Fastening Strategy & Joint Integrity to Reduce Stresses in Ring Gear Bolts on Rear Differential Assemblies

2009-04-20
2009-01-0411
Ring gear bolts in differentials are often modified in size to accommodate the additional clamp load that is required due to an increase in torque from a vehicle's powertrain. Depending on a given program several constraints need to be considered. These include cost, validation time, reliability / durability and timing for implementation. In this paper, a Finite Element Analysis (FEA) procedure for analyzing stresses in ring gear bolts within a rear differential assembly is outlined and the computational results are then compared to quasi-static bench test results that were developed to measure bending and tension loads in the ring gear bolts during loading and unloading of the axle pinion. A dynamometer test is then developed to duplicate the failure mode and provide a comparison of the design changes proposed and the expected improvement in durability.
Technical Paper

Mechanical and Thermophysical Properties of Magnesium Alloy Extrusions

2010-04-12
2010-01-0410
Magnesium alloy extrusions offer potentially more mass saving compared to magnesium castings. One of the tasks in the United States Automotive Materials Partnership (USAMP) ?Magnesium Front End Research and Development? (MFERD) project is to evaluate magnesium extrusion alloys AM30, AZ31 and AZ61 for automotive body applications. Solid and hollow sections were made by lowcost direct extrusion process. Mechanical properties in tension and compression were tested in extrusion, transverse and 45 degree directions. The tensile properties of the extrusion alloys in the extrusion direction are generally higher than those of conventional die cast alloys. However, significant tension-compression asymmetry and plastic anisotropy need to be understood and captured in the component design.
Technical Paper

Effect of Simulated Material Properties and Residual Stresses on High Cycle Fatigue Prediction in a Compacted Graphite Iron Engine Block

2010-04-12
2010-01-0016
Casting, machining and structural simulations were completed on a V8 engine block made in Compacted Graphite Iron (CGI) for use in a racing application. The casting and machining simulations generated maps of predicted tensile strength and residual stress in the block. These strength and stress maps were exported to a finite element structural model of the machined part. Assembly and operating loads were applied, and stresses due to these loads were determined. High cycle fatigue analysis was completed, and three sets of safety factors were calculated using the following conditions: uniform properties and no residual stress, predicted properties and no residual stress, and predicted properties plus residual stress.
Technical Paper

Technical Potential for Thermally Driven Mobile A/C Systems

2001-03-05
2001-01-0297
Aqua-ammonia absorption refrigeration cycle and R-134a Vapor jet-ejector refrigeration cycle for automotive air-conditioning were studied and analyzed. Thermally activated refrigeration cycles would utilize combustion engine exhaust gas or engine coolant to supply heat to the generator. For the absorption system, the thermodynamic cycle was analyzed and pressures, temperatures, concentrations, enthalpies, and mass flow rates at every point were computed based on input parameters simulate practical operating conditions of vehicles. Then, heat addition to the generator, heat removal rates from absorber, condenser, and rectifying unit, and total rejection heat transfer area were all calculated. For the jet-ejector system, the optimum ejector vapor mass ratio based on similar input parameters was found by solving diffuser's conservation equations of continuity, momentum, energy, and flow through primary ejector nozzle simultaneously.
Technical Paper

Automotive A/C System Integrated with Electrically-Controlled Variable Capacity Scroll Compressor and Fuzzy Logic Refrigerant Flow Management

2001-03-05
2001-01-0587
This paper describes the recent efforts on developing an automotive climate control system throughout integrating an electrically-controlled variable capacity scroll compressor with a fuzzy logic control-based refrigerant flow management. Applying electrically-controlled variable capacity compressor technology to climate control systems has a significant impact on improving vehicle fuel economy, achieving higher passenger comfort level, and extending air and refrigerant temperature controllability as well. In this regard, it is very important for automotive climate control engineers to layout a system-level temperature control strategy so that the operation of variable capacity compressor can be optimized through integrating the component control schemes into the system-level temperature control. Electronically controlled expansion devices have become widely available in automotive air conditioning (A/C) systems for the future vehicle applications(1, 2, 3 and 4).
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