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Automated Driving System Safety: Miles for 95% Confidence in “Vision Zero”

Driving Safety Consulting LLC-Richard Allen Young
  • Technical Paper
  • 2020-01-1205
To be published on 2020-04-14 by SAE International in United States
Engineering reliability models from RAND, MobilEye, and Volvo concluded that billions of miles of on-road data were required to validate that the real-world fatality rate of an “Automated Driving System-equipped vehicle” (AV) fleet for an improvement over human-driven conventional vehicles (CV). RAND said 5 billion miles for 20%, MobileEye 30 billion for 99.9%, and Volvo 5 billion for 50% improvement. All these models used the Gaussian distribution, which is inaccurate for low crash numbers. The current study proposes a new epidemiologic method and criterion to validate real-world AV data with 95% confidence for zero to ten fatal crashes. The upper confidence limit (UL) of the AV fatal crash rate has to be lower than the CV fatal crash rate with 95% confidence. That criterion is met if the UL of the AV fatal crash incidence rate ratio estimate is below one. That UL was estimated using the mid-P exact method for calculating confidence limits for a dual Poisson process, using a one-tailed 95% confidence level. The required AV mileage was adjusted by trial and error…
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Tightening Reliability of Bolted Joints in Calibrated Wrench Method (Improvement of Initial Clamping Force Distribution and Optimum Tightening Torque by Elliptical Confidence Limit)

Tokyo Metropolitan University-Soichi Hareyama, Ken-ichi Manabe, Satoshi Kobayashi
  • Technical Paper
  • 2020-01-0218
To be published on 2020-04-14 by SAE International in United States
On tightening bolted joints, the calibrated wrench method is used in manufacturing industries for a large amount of tightening work. It is important to give high initial clamping force in respect of tightening reliability, prevention of self-loosening, the prevention from fatigue breakage, and so on. In this method the clamping force of bolted joints is controlled by grasping the wrench torque. However, since the clamping force is indirectly applied by wrench, it varies greatly in lot of tightening in factory, etc. Therefore, the calibrated wrench method is not so accurate from the viewpoint of clamping force control. It is thought that distribution of this kind is conventionally varied in a rhombus. When tightening torque and clamping force are considered to be two independent random variables, the clamping force is distributed within an elliptical confidence limit. We also show that the distribution of equivalent stress is obtained in an elliptical confidence limit. Considering the permitted limit for working load stress on a bolted joint, elliptical distribution has big margin to yield point than the shape of…
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Experimental Study on Static and Fatigue Behavior of a Short Glass Fiber Reinforced Polypropylene

FCA US LLC-Mingchao Guo, Congyue Wang, Jian Tao, Ramchandra Bhandarkar
InDepth Engineering Solutions-Johnson Joseph
  • Technical Paper
  • 2020-01-0190
To be published on 2020-04-14 by SAE International in United States
One approach of reducing vehicle weight is using composite materials. Fiber reinforced polypropylene is one of the most popular composite materials. To improve accuracy in prediction of durability performance of structures made of this kind of composite material, static and fatigue properties of a 30% fiber reinforced polypropylene have been physically studied. This paper describes details of test coupon design, fabrication and test setup of both quasi static and fatigue tests. In this study, various fiber orientation (0, 20, 90 degrees & knit line), temperature (-40, 23 and 80 degree C), mean stress (R=-1.0, -0.5, -0.2, 0.1 and 0.4) have been considered and the result of the tests discussed.
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Dynamic-static Optimization Design of Parking Robot Lifting Arm with Uncertain Parameters

Tongji University-Xiang Xu, Xinbo Chen, Zhe Liu, Yanan Xu, Yan Li, Yunkai Gao
  • Technical Paper
  • 2020-01-0511
To be published on 2020-04-14 by SAE International in United States
There are many uncertainties in engineering design, and the accumulated uncertainties will enlarge the overall failure probability of the structure system. Therefore, the structural design considering uncertainties is of high significance for improving its reliability. To address this issue, a dynamic-static structural topology optimization model is established and a reliability-based topology optimization (RBTO) with decoupling format is conducted in this study. At First, the design point which satisfies the constraint of target reliability indicator is obtained according to the reliability indictors of the first-order reliability method. Then, according to the sensitivity information of the random variable, the random variable is modified into a deterministic variable. Finally, the reliability-based deterministic topology optimization is performed by dividing the problem into two independent sub-problems of reliability analysis and equivalent deterministic topology optimization (DTO), and the feasibility of the structure optimization method is verified with the parking robot lifting arm. To meet the mechanical performances and lightweight requirements of the parking robot lifting arm, the mathematical model of dynamic-static multi-objective topology optimization for the lifting arm is established by…
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Fatigue life Prediction of HVAC pipe assembly for measured powertrain load by virtual simulation

FCA Engineering India Pvt., Ltd.-Sathish Kumar Pandi, C Elango, Kameswara Rao Appana, Roshan N. Mahadule, DivaKaruni Murali Krishna
  • Technical Paper
  • 2020-01-0188
To be published on 2020-04-14 by SAE International in United States
Structural durability of automotive components is one of the key requirements in design and development of today’s automobiles. Virtual simulations are used to estimate component durability to save the cost and time required to build the components and testing. The objective of this work is to find the service life of automotive HVAC pipe assembly by calculating cumulative fatigue life for operation under actual powertrain load conditions. Modal transient response analysis is performed using MSC-Nastran with the measured powertrain load time history. Strain based fatigue life analysis is carried out in n-code using modal superposition method (MSM). The estimated fatigue life was compared with the physical test results. This paper also explains the root cause of low fatigue life on pipe assembly and provide the solution. Keywords: Durability, HVAC Pipe, Powertrain, Modal Transient, Fatigue Life
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Design of the powder metal shift fork and sleeve

Czech Technical University-Gabriela Achtenova, Jiri Pakosta
  • Technical Paper
  • 2020-01-1322
To be published on 2020-04-14 by SAE International in United States
The paper will present the design of shift fork for automotive manual gearbox dedicated for the manufacturing with help of powder metal technology. Based on limitations and requirements of new production technology of shifting sleeve, a new prototype of shifting sleeve is created, for which are new shifting forks then designed. The form of the prototype of the shift sleeve respected the requirements of the new technology, but from cost reason, it was manufactured from steel. The shift fork was changed accordingly to the new form of the shift sleeve. The functionality of several forks with different tolerances was tested. Prototypes were put through functional and durability tests on testing bench in real automotive gearbox. The test were accomplished on the inertia test stand. Drawings and CAD models of tested prototypes, custom tools and designed shift forks will be described.
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Frame structure durability development methodology for various design phases

FCA Engineereing India Pvt., Ltd.-Raghavendra Byali, Venkatesh Naik
FCA US LLC-Chandra Thandhayuthapani, Barry Lin, Jianghui Mao
  • Technical Paper
  • 2020-01-0196
To be published on 2020-04-14 by SAE International in United States
It is a challenging task to find an optimal design concept for a truck frame structure given the complexity of loading conditions, vehicle configurations, packaging and other requirements. In addition, there is a great emphasis on light weight frame design to meet stringent emission standards. This paper provides a framework for fast and efficient development of a frame structure through various design phases, keeping durability in perspective while utilizing various weight reduction techniques. In this approach frame weight and stiffness are optimized to meet strength and durability performance requirements. Fast evaluation of different frame configurations during the concept phase (I) was made possible by using DFSS (Design For Six Sigma) based system synthesis techniques. This resulted in a very efficient frame ladder concept selection process. Frame gauge optimization during the subsequent development phase (II) utilizing a newly developed damage based approach greatly reduced the number of design iterations relative to a typical stress based approach. In the light weighting phase(III) that followed, a method was established to effectively locate and optimize lightening holes using fatigue…
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Experimental-numerical correlation of a multi-body model for comfort analysis of an heavy truck

CNH Industrial-Andrea Morello, Vladi Nosenzo, Enrica Capitelli
Politecnico di Torino-Enrico Galvagno, Michele Galfrè, Mauro Velardocchia
  • Technical Paper
  • 2020-01-0768
To be published on 2020-04-14 by SAE International in United States
In automotive market, today more than in the past, it is very important to reduce time to market and, mostly, developing costs before the final production start. Ideally, bench and the on-road tests can be replaced by multi-body studies because virtual approach guarantees test conditions very close to reality and it is able to exactly replicate the standard procedures. Approval authorities are starting to look at simulations to release homologation certificates. Therefore, today, it is essential to create very reliable models, able to forecast the vehicle behavior on every road condition (including uneven surfaces). The aim of this study is to build a reliable multi-body model of a heavy commercial vehicle and to correlate experimental and numerical data related to comfort analysis for validation purposes. Experimental results are recorded during tests carried out at different speeds and loading conditions on a Belgian blocks track. Simulation data are obtained reproducing the on-road test conditions in multi-body environment. The virtual vehicle is characterized by rigid and flexible bodies, the tire model used is FTire (Flexible Structure Tire…
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N&V Component Structural Integration and Mounted Component Durability Implications

General Motors LLC-Mark Stebbins, Joseph Schudt
  • Technical Paper
  • 2020-01-1396
To be published on 2020-04-14 by SAE International in United States
Exterior component integration has presented competing integration challenges for suitable exterior styling, safety, N&V structural feel and component durability balanced performances. Industry standard practice of N&V vehicle mode mapping uses vehicle source, path and receiver considerations for component mode frequency placement. Mounted component mode frequency performance can have an influence on structural feel and durability performances. Component integration headwinds have increased with additional nonstructural component styling content, component size, component mass and added sensor modules. Based on first principles, the effective mass of exterior mounted components are increased due to the geometric overhang from structure. Component input vibration levels are compounded due to the cantilevered nature as well as relative positioning to the suspension and propulsion vehicle source inputs locations. Examples of vehicle end mounted components include but are not limited to headlamps, side mirrors, end gates, bumpers and fascia. Our goal is to establish basic expectations for the behavior of these systems, and ultimately to consolidate our existing rational and approaches that can be applied to such integrated systems. The focus of this paper…
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A Robust Methodology for Predicting the Fatigue Life of an Automotive Closures System Subjected to Hinge and Check Link Load

Ford India Pvt., Ltd.-Nirmal Puthuvayil, Sivasankari S
RLE India Pvt., Ltd.-Thoheer Zaman
  • Technical Paper
  • 2020-01-0599
To be published on 2020-04-14 by SAE International in United States
Quality in the automotive industry symbolizes the development and the manufacturing of vehicles whose specifications meet customer requirements. Among the quality issues, opening and closing effort of any closures in a vehicle is a characteristic that strongly affects the customer first opinion about vehicle design. The closure opening and closing effort is affected by different uncertainties like opening angle, load to the check-link, hinge stoppage, materials and manufacturing process. A check stop & hinge stop load durability cycle occurs when a customer opens the closures beyond the closure detent position with a force applied on the check link or hinge check stops. Due to few uncertainties like abuse opening, manufacturing imperfections, weak mounting locations, the closures will be subjected to fatigue failure. The present study is aimed to introduce a probabilistic frame-work for fatigue life reliability analysis that addresses the uncertainties associated with door opening-closing effort due to check-hinge loads, door closure opening angles and hinge stop tolerance. A fatigue life probabilistic model of various closure systems was developed using Monte-Carlo simulation, where the stress…