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User Defined FE Based Connector Joints for Plastics

CAEfatigue Ltd-Neil Bishop, Paresh Murthy
Hella GmbH & Co. KGaA-Thomas Thesing, Odo Karger
  • Technical Paper
  • 2020-01-0186
To be published on 2020-04-14 by SAE International in United States
Spot Welds are a category of welds used extensively in automotive structures, normally for metals. The fatigue analysis of such spot welds can be evaluated using (a) the Point 2 Point (P2P) method where a beam or bar is used to connect the 2 surfaces being joined, (b) a more modern approach where the 1D element is replaced with an “equivalent” brick element, or (c) a third approach that falls somewhere between where a “spider” and circular ring of elements, is used to represent the spot weld. In all 3 cases there is an assumption that the cross section is circular. For some specialist cases such as plastic connectors, the cross section is not circular so a new user defined weld is proposed. This paper will describe the approach that is based on the concept that a user generated tensor line can be used (equivalent to the theoretical Force/Moment to stress algorithms built into the P2P approach) along with special S-N curves create for different joint shapes.
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Reducing Cycle Times of Refill Friction Stir Spot Welding in Automotive Aluminum Alloys

Brigham Young University-Brigham Larsen, Yuri Hovanski
  • Technical Paper
  • 2020-01-0224
To be published on 2020-04-14 by SAE International in United States
A major barrier, preventing RFSSW from use by manufacturers, is the long cycle time that has been historically associated with making a weld. In order for RFSSW to become a readily implementable welding solution, cycle times must be reduced to an acceptable level, similar to that of well developed, competing spot joining processes. In the present work, an investigation of the RFSSW process is conducted to evaluate factors that have traditionally prevented the process from achieving fast cycle times. Within this investigation, the relationship between cycle time and joint quality is explored, as is the meaning and measurement of cycle time in the RFSSW process. Claims and general sentiment found in prior literature are challenged regarding the potential for high-speed RFSSW joints to be made. The RFSSW weld design-as described by process parameters such as tool feed rate, tool rotational velocity, and plunge depth- is shown through experimentation to affect the loads and torques placed on RFSSW tooling and machines during the welding process. As cycle time is decreased, the load and torque on the…
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Coupled Weld-Rupture Analysis of Automotive Assemblies

ESI North America-Yogendra Gooroochurn, Ramesh Dwarampudi, Vijay Tunga
ESI US R&D-Megha Seshadri, Ravi Raveendra
  • Technical Paper
  • 2020-01-1076
To be published on 2020-04-14 by SAE International in United States
Lightweight driven design in the automotive industry and the push for Electric Vehicles mandate the use of innovative materials such as Steel (HSS, UHSS, AHSS) and Aluminum alloys. For steel suppliers to meet the strength requirements of high strength steels, they often alloy the steel chemistry (depending on mill capability, rolling capacity, quenching capacity, etc.). When used in welded assembly constructions, these steels, as compared to traditional steels, behave differently. Depending on the welding heat input, the material chemistry and thickness, they either harden or soften in the heat affected zone. Similar behavior is observed with the most commonly used aluminum alloys (5000 and 6000 series) in the automotive sector. For both alloy types, different strengthening mechanism are used to meet their initial strength requirements (by work hardening and by heat treating respectively) but they both undergo softening in the heat affected zone during welding. Regardless of the alloys, the material in the heat affected zone is affected and so is the performance of the weldment during service. FE analyzes of Welding and Performance have…
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Spatially Optimized Diffusion Alloys: A Novel Multi-Layered Steel Material for Exhaust Applications

Arcanum Alloys Inc.-Zachary Detweiler, David Keifer, Daniel Bullard
Tenneco Inc.-Adam Kotrba, Tony Quan, Winston Wei
  • Technical Paper
  • 2020-01-1051
To be published on 2020-04-14 by SAE International in United States
A novel Spatially Optimized Diffusion Alloy (SODA) material has been developed and applied to exhaust systems, a very aggressive environment with high temperatures and loads, as well as excessive corrosion. Traditional stainless steels disperse chromium homogeneously throughout the material, with varying amounts ranging from 11% to 18% dependent upon its grade (e.g. 409, 436, 439, and 441). SODA steels, however, offer layered concentrations of chromium, enabling an increased amount along the outer surface for much needed corrosion resistance and aesthetics. This outer layer, approximately 70µm thick, exceeds 20% of chromium concentration locally, but is only 3% in bulk, offering selective placement of the chromium to minimize its overall usage. And, since this layer is metallurgically bonded, it cannot delaminate or separate from its core, enabling durable protection throughout manufacturing processes and full useful life. The core material may be of various grades, however, so this study employs interstitial free steel (low carbon), which offers not only commercial advantages, but also eases manufacturing operations, as it is more formable than stainless steel grades. The material and…
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Influence of Weld Lines on the Mechanical Properties of Talc Filled Polypropylene

Ford Motor Company-Shiyao Huang, Patti Tibbenham, Lingxuan Su, Danielle Zeng, Jin Zhou, Xuming Su
University of Michigan-Ann Arbor-Mayme Philbrick
  • Technical Paper
  • 2020-01-1306
To be published on 2020-04-14 by SAE International in United States
Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). In this paper, two different injection molding tests were completed. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line region. Tensile samples were cut at different locations along the weld line on the injection molded plaques. The test results showed that both UTS and fracture strain increase when the sample locations are away from the insert. This trend is attributed to different meeting angles. Second, standard ISO tensile bars with and without weld line were injection molded to identify the size of the weld line affected zone. A FEA model was built in ABAQUS, where the tensile sample was divided into two different regions, the solid region and the weld line affected region. Stress-strain relationships of the solid region were derived from tensile tests of solid bars, while the mechanical properties of weld line affected zones were characterized from the weld line samples using…
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An Analytical Model for Predicting the Fatigue Behavior of Tubular Weldments Subjected to Compressive Loading

American Axle & Manufacturing, Inc.-Anoop Vasu, Shizhu Xing, Jifa Mei, William Webster, Scott Jacob, Jerry Chung, Ravi Desai
  • Technical Paper
  • 2020-01-0185
To be published on 2020-04-14 by SAE International in United States
It has been well-documented in academic literature that, when subjected to compressive cyclic loading (R = -∞), weldments can experience fatigue failure. However, unlike non-welded components, it has been shown that mean stress has a negligible impact on the fatigue life of welds (Gurney, 1979). Currently, most analytical weld prediction methods neglect the influence of mean stress and instead focus only on the relationship between the stress (or strain) amplitude and the respective number of cycles to failure. To better understand the influence of compressive mean stress on tubular weldment fatigue life, three case studies were performed under varying loading conditions: 1) Welds were subjected to compressive pre-stress using pretensioned bolts and then subjected to various cyclic loading conditions via three-point bending, 2) Welds without pre-stress were subjected to various cyclic loading conditions intended to generate compressive mean stress in the welds via three-point bending, 3) Welds without pre-stress were subjected to various cyclic loading conditions intended to generate a stress state of pure tension or pure compression in the welds via four-point bending. It…
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Fatigue Evaluation of Flow Drill Screw Joints Using the Equilibrium-Based Structural Stress Method

Engineering Mechanics Corp. of Columbus-Jeong Hong, Gery Wilkowski
  • Technical Paper
  • 2020-01-0189
To be published on 2020-04-14 by SAE International in United States
According to the increasing demands for light-weight design in the automotive industry, the use of thinner and lighter materials such as aluminum alloys for automotive parts has led to significant weight reduction. The joining of these materials has required development of new technologies in joining/fastening rather than welding. Flow drill screwing is one of the latest technologies created to fasten sheet metal panels.This paper discusses results of an evaluation of fatigue characteristics of flow drill screw (FDS) joints based on experimental data and observations from the literature. It was observed that the important fatigue-related geometric parameters of FDS joints were the gap between sheets and the extruded (or bulged) zone during screwing. Major failure modes were observed such as sheet failures where cracks grow from the inner surface of the sheet and around the extruded zone.In this paper, the fatigue evaluation procedure for FDS joints using the mesh-insensitive equilibrium-based structural stress (ESS) method was used. The ESS-based simplified modeling procedure was used for the fatigue-evaluation procedure for FDS joints. The effectiveness and applicability of the…
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Full Body Car Analysis in the Time and Frequency Domains - Sheet, Spot and Seam Weld Fatigue Benchmark Studies

CAEfatigue, Ltd.-Neil Bishop, Stuart Kerr
Desktop Engineering Ltd.-Andy Woodward
  • Technical Paper
  • 2020-01-0195
To be published on 2020-04-14 by SAE International in United States
The fatigue analysis of a full car body requires the sheet metal (sheet fatigue), spot welds (spot weld fatigue) and seam welds (seam weld fatigue) to be thoroughly evaluated for durability. Traditionally this has always been done (via separate processes) in the time domain but recently new techniques have been implemented to perform all of these tasks in the frequency domain with numerous advantages. This paper will summarize the frequency domain process and then compare the results (and performance) against the more usual time base result
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Crash Response of a Repaired Vehicle - Influence of Welding UHSS Members

University of Agder-Gulshan Noorsumar, Kjell Robbersmyr, Svitlana Rogovchenko, Dmitry Vysochinskiy
  • Technical Paper
  • 2020-01-0197
To be published on 2020-04-14 by SAE International in United States
Automakers generally recommend not to weld structural parts after a vehicle crash, and these should be replaced as a whole part in case of a crash event. Sectioning of these members is also not recommended and use of the repair manual is mandatory in case of fracture of such parts. However, repair shops may not adhere to these instructions and use incorrect repair procedures on these members which would modify their strength properties. This study analyses the impact of welding structural members in a vehicle like the A-pillar which use Ultra-High Strength Steels (UHSS) for reducing the weight of the vehicle and improving the crashworthiness of the structure. The research conducted in this paper highlights the differences in the crash performance of a repaired vehicle as opposed to baseline injury values for the vehicle. The performance of the modified vehicle when tested for different loadcases shows reduced crash performance as compared to the baseline performance and it can be concluded that welding or sectioning the UHSS parts would influence the crashworthiness of a vehicle. This…
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A Study on Bolted Joint Finite Element Modeling for Vehicle Level Durability Analysis

FCA US LLC-Weidong Zhang, Mingchao Guo
  • Technical Paper
  • 2020-01-0178
To be published on 2020-04-14 by SAE International in United States
Bolted joints are widely used connections in automotive vehicle structures. However, it has been a challenge to accurately predict static and fatigue behavior of the sheet metal adjacent to the bearing area of bolted joints when linear analysis approach is used. This paper describes an experiment study on static and fatigue behavior of sheet metal adjacent to bearing area of bolted joints which are typically found on vehicles. These joints cover different bolt sizes (M6 to M14), and nut types (hex nut, hex flange nut, round nut, welded nut etc.). Different sheet metal material grades were selected which were, mild steel, high strength steel, dual phase steel and aluminum. The joints were subjected to coach-peel loading condition, because fastened joints have lowest strengths under this condition. 25 different joint combinations were included in this experimental study. For both static and fatigue tests, three samples were tested for each joint type and loading condition combination. Digital Image Correlation (DIC) technique was used to measure strain distributions at critical locations of the samples. Displacement at the loading…