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Technical Paper

Comparing stress gradient and other concepts for fatigue analysis of notched components

2022-03-29
2022-01-0252
Nowadays simulation of the fatigue life is an essential part of the development of components in the automotive and machinery industry. Weak points can be identified fast and reliable with respect to stiffness, strength and lightweight. A pure virtual optimization of the design can be performed without the need of prototypes. Only for the production release a final test is necessary. A lot of parameters influence the fatigue life as the local stress, material, surface roughness, size of the component, temperature etc. Notches have the strongest impact on fatigue life, depending on radius and shape. Stresses at the notch base are increased because the load flow is forced through a reduced cross section, or changes its direction around an inwardly curved edge. But notches cause not only an increase of the local stress. Also, the local fatigue strength is increased because of a support effect from the neighboring areas, where the stress is already reduced.
Technical Paper

A study on editing method of road load spectrum of automobile rubber isolator using time-frequency domain methods

2022-03-29
2022-01-0272
In order to enhance the efficiency of durability testing of automobile parts, a time-frequency domain accelerated editing method of road load time series of rubber mount on powertrain was discussed. Based on Stockwell Transform method and Accumulative Power Spectral Density, a new time-frequency domain accelerated editing method (ST-APSD) was proposed. The accumulative power spectral density was obtained by ST of the load time series signal of automobile powertrain rubber mounting force which is acquired by the real vehicle in the test field. Based on the accumulative power spectral density, the threshold value was proposed to identify and delete the small damage load fragments, and then the acceleration spectrum was obtained.
Technical Paper

Technical Keynote: Durability Validation for Variable Vehicle Usage

2022-03-29
2022-01-0255
Durability engineering for vehicles is about relating real operational loading to the actual strength of the product and its components. In the first part of this presentation, we show how to calculate failure probabilities and safety factors based on the load and strength distributions. We discuss the uncertainty within the estimations, which is considerably large in case of extremely small failure probabilities as required for safety critical components. In the second part, we focus on modelling and simulating the loads based on real vehicle usage, such that the resulting statistics allows to understand and quantify the usage variability. The idea is, to simulate thousands of vehicle life spans of, say, 300.000 km or 15.000 h of operation each. The input data for such simulations typically consists of a combination of geographic data (like road network, topography, road conditions, traffic data, and points of interest) and properly segmented rich data from measurement campaigns.
Technical Paper

US EPA NVFEL Repeatable-Vehicle Program – Emission Lab Testing System Performance Quality Monitoring

2022-03-29
2022-01-0568
According to US FCR the vehicle emission testing system must be monitored and checked periodically, and NVFEL TATD has developed a quality control monitoring program named “Repeatable-Vehicle Program”, the current vehicle selected is a proper sized and featured sedan, so called RepCar. The vehicle emission lab cell test used a chassis dyno to simulate some road driving conditions, a CVS system to collect exhaust sample and analyzed by a group of chemical benches. The testing condition is satisfied the FCR requirement and controlled during the testing procedure. A specific driving cycle including two phases was designed to evaluate vehicle power system at different speed load performance and measurement instruments accuracy under different concentration range. The phase1 is modified FTP505, phase2 is the most aggressive part of US06, and at the end of phase2 driving trace had a 30-second constant 75 mph cruising followed by a coast down.
Technical Paper

Dynamic durability prediction of fuel cells using Long short-term memory neural network

2022-03-29
2022-01-0687
Durability performance prediction is a critical issue in fuel cell research. During the demonstration operation of fuel cell commercial vehicles in China, this issue has attracted more attention. In this article, the long short-term memory neural network (LSTMNN), which is an improved recurrent neural network (RNN), and the demonstration operation data are used to establish the prediction model to predict the durability performance of fuel cell stack. Then, a model based on back-propagation neural network (BPNN) is established to be a control group. The demonstration operation data is divided into training group and validation group. The former is used to train the prediction model, and the latter is used to verify the validity and accuracy of the prediction model. The outputs of the prediction model, as the durability performance evaluation indexes of fuel cell, are the polarization curve (current-voltage curve) and the voltage decay curve (time-voltage curve).
Technical Paper

A method for acquiring and editing the load spectrum of the drive-shaft system for an all-terrain vehicle

2022-03-29
2022-01-0268
The durability road test of a vehicle is an important test to verify the reliability of vehicle components. In order to carry out the durability bench test for drive shaft systems of all-terrain vehicles, a method for acquiring time domain signals of articulation angles of the CVJ, input torque, and rotational speeds of drive shaft systems is proposed. The acquired load spectrum of drive shaft systems is preprocessed including deleting small amplitudes, de-drifting, deburring, filtering, etc. Peaks and valleys are extracted from the preprocessed load spectrum. Based on the graphic method and the estimator stabilization method, the upper and lower thresholds of the time domain extrapolation of the load spectrum are determined, and then the peaks and valleys excesses that exceed the upper and lower thresholds are extracted. The generalized pareto distribution function is used to fit the distribution of peaks and valleys excesses.
Technical Paper

Thermomechanical behavior of an automotive exhaust aftertreatment application

2022-03-29
2022-01-0277
An aftertreatment system is the back-end component of an automotive exhaust system, used mainly to reduce pollutant emissions. This system is exposed to high thermal loads which can exceed temperatures of 900 oC , usually they operate at temperatures under 600 oC - 700 oC, depending of the engine application. The durability assessment of a system under thermomechanical loads can be challenging due to the complexity of the technical problem, which involves complex material behavior at high temperatures and results in high thermomechanical strains and stresses. This study presents a computational approach for the lifetime assessment of an exhaust aftertreatment system subjected to thermomechanical loading. The method is composed of a fluid flow analysis to compute the temperature fields which are mapped to a mechanical analysis combined with a nonlinear elastoviscoplastic material behavior. Lastly, the lifetime of the overall assembly is assessed through a fatigue analysis.
Technical Paper

Design for Six Sigma (DFSS) Optimization of Vehicle IIHS Small Overlap Rigid Barrier (SORB) Impact Performance Using a Simplified Spring-Mass CAE Model

2022-03-29
2022-01-0781
In the modern practice of the vehicle crashworthy design development and its impact performance validation, virtual full vehicle crash models have been widely and successfully utilized as the analysis tool by many safety CAE engineers. Recently, a typical full-vehicle front impact model has grown in size up to over 3 million finite elements to enable analysis of highly localized and transient responses of vehicle structure deformation under the impulsive loads. This full vehicle model takes 10 ~15 computer hours per run even on a fast Massively Parallel Process(MPP) server. The CPU time will increase if the full-vehicle model is applied for analysis of the offset-barrier events in which the test vehicle receives barrier impact loading for a longer duration.
Technical Paper

Optimization of Body Joint Stiffness and Structure

2022-03-29
2022-01-0756
The global stiffness of the body (B.I.W) is an important factor in performance such as durability, R&H, and NVH. It is also theorized that the high stiffness of each joint structure is necessary for the high stiffness of the overall body structure. Despite much research on this, the correlation between joint stiffness and body (B.I.W.) stiffness has not been clearly identified. Therefore this study studied the effect of joint stiffness on body global stiffness and set the target stiffness required for each joint. A design approach to meet the required stiffness level was studied and optimal joint structure was designed. Research procedures include: 1. Select the scope of joint research 2. Boundary Condition Setting and Result Processing Method for Joint Stiffness Verification 3. Analysis of Joint Stiffness current level 4. Body Stiffness Sensitivity of Each Joint 5. Joint Stiffness Sensitive Components 6. Setting the target stiffness value for each joint 7.
Technical Paper

Integrated Evaluation of Constant Amplitude Life Tests Towards SN Curves and Endurance Limit

2022-03-29
2022-01-0250
Establishing SN curves from constant amplitude life tests and locating the endurance limit are indispensable tasks in durability engineering. For both regimes, finite life and endurance limit, there are many approaches available, like linear regression or maximum likelihood. Especially on low load levels, tests may run very long and one may suspend them before failure. Especially the stair case method for evaluating the endurance limit systematically produces almost 50 percent suspended results. Hence, when data for both regimes is available, those run-outs need to be considered in a statistically proper way. If both regimes are evaluated separately it is often ambiguous if a single observations may be used for estimating the endurance limit or for the finite life re-gime. In this paper, we present an integrated approach, for simultaneous evaluation of both regimes. Every single ob-servation is mapped to one of the regimes with certain probabilities.
Technical Paper

An Engineering Approach to Consider Stress Concentrations in Fatigue Life Predictions on Automotive Body Structures

2022-03-29
2022-01-0261
This paper proposes a new procedure for more accurate durability predictions on the edges of structural components especially on notch regions. Current CAE procedures based on elemental stress often require iterative mesh refinement to correlate predictions to experimental cracking on the edges of components. The new proposed procedure is based on element nodal stress. It is first studied theoretically on a rectangular plate with different element sizes and options and demonstrates an improvement over elemental stress methods. It is then studied on multiple examples of experimental cracks and successfully predicts issues where current elemental stress methods do not. In addition, it avoids the iterative mesh refinement associated with current methods. In summary, the new method based on nodal stress is more accurate, more efficient, and improves first time through capability on the edges of structural components.
Technical Paper

Powertrain NVH CAE Process Enhancement Using Non-linear Interaction Modelling

2022-03-29
2022-01-0615
NVH CAE is considered as one of the aspects of engine component design process. Following the best practices for CAE throughout the industry is the current trend which tend to miss the fact of improving it as per the continuously evolving component designs. Continuous improvement is necessary in existing methods and procedures to enhance CAE methodologies. Correlation of CAE models with measurement results increases stakeholders’ confidence and further allows to try out various combinations to reduce product development cycle time as well as cost. Engine components are connected with each other at periphery through bolted connection with required torque. This study focuses on improvement of standard automotive connection modelling method through inclusion of non-linearity at the engine components interfaces. NVH simulation predictions improves significantly through its incorporation in comparison with existing practices.
Technical Paper

A Parametric Sensitivity Study of Predicted Transient Abuse Loads for Sizing Electric Drive-Unit and Driveline Components

2022-03-29
2022-01-0680
The design and development of electric vehicles poses many unique challenges that are typically not present in the design and development of traditional vehicles powered by an internal combustion engine. One such challenge involves accurately predicting driveline abuse torque loads early in the design cycle to aid in sizing drive-unit and driveline components. Since electrified drivelines typically lack a torque-limiting ‘fuse’ element such as a torque converter or slipping clutch, they are particularly vulnerable to sudden transient events involving high wheel acceleration or deceleration. Therefore, component sizing must account for the loads caused by such events, and these loads must be accurately quantified early in the design cycle. This load-prediction problem can be tackled by performing abuse maneuver simulations early in the design process, and varying key vehicle design parameters to gauge their influence on the simulated loads.
Technical Paper

A DFSS approach to optimize the Hood design parameters to improve durability performance

2022-03-29
2022-01-0771
In the Vehicle front closure development process, it is very important to meet the durability functional attributes such as Fit and finish, slam event and ease of closing effort. Conventionally softer seal & bump-stop stiffness properties are required for better flushness, but a stiffer seal & bump-stop will help to arrest the hood over travel during the slam event. It is always a challenging and iterative process to arrive at an optimum combination of these design parameters to meet both the flushness and slam targets. This paper highlights the six sigma approach to identify the effect of various control factors like Seal & Bump stop stiffness, latch position, bump-stop design clearance to meet the durability functional attributes. This approach suggests optimum design which is less sensitive to noise factors such as build tolerances on the latch position and the bump-stop design clearance.
Technical Paper

Development of a CAE Modeling Technique for Heavy Duty Cargo Weight using a DFSS Methodology

2022-03-29
2022-01-0774
Cargo box is one of the indispensable structures of a pickup truck which makes it capable of transporting heavy cargo weights. This heavy cargo weight plays an important role in durability performance of the box structure when subjected to road load inputs. Finite element representation for huge cargo weights is always challenging, especially in a linear model under dynamic proving ground road load durability analysis using a superposition approach. Any gap in virtual modeling technique can lead to absurd cargo box modes and hence durability results. With the original computer aided engineering (CAE) approach, durability results could not correlate much with physical testing results. It was crucial to have the right and robust CAE modeling technique to represent the heavy weight to provide the right torsional mode of the cargo box and good durability results.
Technical Paper

Analytical Method for Console Lid Latch Squeak and Rattle Risk Assessment and Validation

2022-03-29
2022-01-0314
Squeak and Rattle (S&R) noise in automotive vehicle components is a direct measure of vehicle build quality. With the recent advances in electric propulsion technology the cabin interior has become even more quieter, but S&R remains one of the major sources of noise inside the cabin. Also, customer surveys such as J D Power shows that console and glove box latch mechanism are the prominent source of vehicle interior noise. The commonly used design for console lid latch consists of latch pawl preloaded against the console bin in closed condition. The goal of design is to optimize the preload such that the latch remains in contact with the bin under all operating conditions. But inadequate design, poor manufacturing quality control and material degradation after several usage causes the loss of preload. Hence, S&R noise emerges due to friction or impact between the parts which induces undesirable vibration and noise.
Technical Paper

Enhanced SAE 3 link Leaf Spring Model to Generate Durability Virtual Loads

2022-03-29
2022-01-0289
Heavy-duty truck vehicles are generally equipped with leaf spring suspensions. Conventionally, beam elements are used in multibody software to build the leaf spring model to calculate virtual loads. Beam elements require a high computation time due to their numerous degrees of freedoms and force components introduced by beam connections, interleaf contacts, friction, etc. Again, in these simulations, solvers frequently fail in durability loads analysis due to sudden spike in accelerations, high suspension articulation coming from severe road profiles. These drawbacks lead to the use of simplified three-link mechanism models to simulate the leaf spring’s behavior, which is computationally faster. However, the current approach is less accurate as compared to the beam element model because this model has only a torsional spring which accounts for vehicle bounce condition.
Technical Paper

Positional Accuracy of Portable GPS Devices during Different Ride Stages

2022-03-29
2022-01-0828
GPS devices can produce a wealth of data about cyclists’, scooterists’, and other riders’ road paths and route usage. However, prior research has demonstrated that GPS positional accuracy is less reliable for more nuanced roadway positioning, such as which lane a vehicle occupies, as well as within-lane movements, such as acceleration and deceleration⁠. This limitation presents a substantial challenge for crash reconstructionists that may have access to GPS data and require second-by-second positional accuracy to determine such nuanced maneuvers and vehicle positioning in their analysis. The purpose of this study was to examine the positional accuracy of several GPS units during three different ride stages: acceleration, deceleration, and constant speed. The same devices were also tested for stationary accuracy, power cut-off, and simulated impact scenarios.
Technical Paper

Development of a Built-in Type Dashboard Camera with Reliability and Usability

2022-03-29
2022-01-0111
Dashcam, which is considered essential parts of vehicles in Korea, are installed in most vehicles for reasons such as accidents, evidence of threatened driving of other vehicles, and insurance premiums. Aftermarket dashcam have been developed with many improvements such as higher resolution camera and LCD application, but still have problems in usability and durability. The first problem is a separate device mounted on the top of the windshield, which obstructs the driver's view and may injure the driver due to a collision impact. In addition, the connection of the power supply may cause a vehicle breakdown such as a fire due to a worker's mistake or a product defect. Secondly, in order to view the stored video, it is troublesome to remove the SD card and check it on the computer. Moreover, since the LCD is so small, it is difficult to search and play the desired video from the list in many saved files.
Technical Paper

Achieving compliance with RTCA DO-254/EUROCAE ED-80 Design Assurance Guidance for Airborne Electronic Hardware: Quality Management Perspective

2022-03-08
2022-01-0007
RTCA DO-254/ED-80 “Design Assurance Guidance for Airborne Electronic Hardware” is a widely accepted industry standard to ensure safety in avionics hardware. FAA and EASA have recognized DO-254 as an acceptable means of compliance with the applicable airworthiness regulations for the electronic hardware. While microprocessor based complex hardware utilization in safety critical avionic hardware are increasing, and DO-254 compliance is mandated by the certification authorities, development of DO-254 compliant or safety certifiable hardware is becoming more and more important and provides competitive advantage in the industry. The avionics manufacturers need to correlate their existing processes and procedures with DO-254 in order to satisfy DO-254 objectives in their own quality management system structure, which may be challenging and tricky.
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