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Dynamic behavior of in-cylinder pressure causing fatigue failure of reed valves

Subros Ltd.-Ankit Shukla, Paulson Parayil, Arun Kumar Goel, Kamal Sharma
  • Technical Paper
  • 2020-28-0031
To be published on 2020-04-30 by SAE International in United States
For years, researchers have presented numerous studies that consider interaction between working fluid and reed valve motion in displacement compressors. The computing capacities and available CFD and FEA simulation tools have allowed modeling of fully coupled interaction of fluids and moving structures. The present paper describes our experience and results from developing a simplified model of a multi-cylinder reciprocating piston compressor and estimation of pressure surge during sudden acceleration of such compressors. The results show that sudden speed change causes surge in pressures due to formation of pressure waves that reflect back and forth within cylinder. For the chosen geometry and operating conditions, the duration of such waves is much shorter (~ 0.2ms) as compared to longer response time of reed valves (1 ms) that are stiff and highly inelastic. These high pressure waves eventually exceed the fatigue limit of reed valves and cause failures. These pressure waves also influence the performance of reciprocating by causing noise and vibrations which eventually dissipate in to heat thereby lowering the COP of compressor. Simulation results compare well…
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Improvement of Tightening Reliability of Bolted Joints Using Elliptical Confidence Limit in Calibrated Wrench Method

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
The calibrated wrench method is used in the tightening of bolts in manufacturing industries in the case of a large amount of tightening work. It is important to apply a large initial clamping force to ensure tightening reliability and prevent self-loosening, fatigue breakage, and so forth. In this method, the clamping force of bolted joints is controlled using a torque wrench. However, since the clamping force is indirectly applied by a wrench, it varies greatly in the case of a large amount of tightening in a factory. Therefore, the calibrated wrench method is not so accurate from the viewpoint of clamping force control. It is conventionally thought that the distribution of the clamping force has the shape of 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. Here, we show that the distribution of equivalent stress also has an elliptical confidence limit. Considering the permitted limit for working load stress on a bolted joint, the elliptical distribution has…
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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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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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Loads Cascading for Full Vehicle Component Design

CAEfatigue, Ltd.-Neil Bishop
Desktop Engineering Ltd.-Andy Woodward
  • Technical Paper
  • 2020-01-0762
To be published on 2020-04-14 by SAE International in United States
Frequency domain methods of analysis are now being used for the evaluation of fatigue for large vehicle systems and these methods offer advantages over equivalent time domain approaches in a number of ways, including analysis efficiency and the usefulness of derived results. One big potential advantage is to be able to do localized sub-component analysis using “cascaded” loads. Such sub-components can be analyzed with refined parameters such as more sophisticated damping. Local parts can also be re-analyzed at a different phase in the design program. This paper will demonstrate the approach and show examples of the method.
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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 with the measured powertrain load time history. Strain based fatigue life analysis is carried out 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.
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Review and Assessment of Multiaxial Fatigue Limit Models

FCA Canada Inc.-Shiping Zhang
FCA US LLC-Sean McKelvey, Eniyavan Subramanian, Yung-Li Lee
  • Technical Paper
  • 2020-01-0192
To be published on 2020-04-14 by SAE International in United States
The purpose of this paper is to provide a comparison of multiaxial fatigue limit models and their correlation to experimental data. This paper investigates equivalent stress, critical plane and invariant based multiaxial fatigue models. Several methods are investigated here and are compared based on their ability to predict multiaxial fatigue limits from data published in literature. The equivalent stress based LTJ model, with its ability to account for non-proportional loading, provides very accurate predictions of the fatigue limit under multiaxial loading. This accuracy comes from the model constant which is calculated based on multiaxial fatigue data. This is the only model investigated that requires multiaxial fatigue testing to generate the model parameters. All other models rely on uniaxial test results. Of the five stress based critical plane approaches investigated, the model proposed by Susmel and Lazzarin shows the greatest correlation with the multiaxial fatigue limit data. Overall, the invariant based prismatic hull method has the best agreement with the data found in literature. Additionally, a new critical plane model has been proposed. This new model…
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Random Vibration Fatigue Life Assessment of Transmission Control Module (TCM) Bracket Considering the Mean Stress Effect due to Preload

General Motors LLC-Neeraj Carpenter, Sudeep Yesudas, Michael D. Nienhuis
  • Technical Paper
  • 2020-01-0194
To be published on 2020-04-14 by SAE International in United States
Transmission Control Module (TCM) bracket is mounted on the vehicle chassis and is subjected to the random load excitation due to the uneven surface of the road. Assembly of the TCM bracket on the vehicle chassis induces some constant stress on it due to bolt preload, which acts as a mean stress along with the varying random loads. It is important for a design engineer and CAE analyst to understand the effect of all sources of loads on vehicle mount brackets while designing them. The objective of this study is to consider the effect of mean stress in the random vibration fatigue assessment of TCM bracket. The random vibration fatigue analyses are performed for all the three directions without and with consideration of mean loads and results are compared to show the significance of mean stresses in random vibration fatigue life. It was found from this study that mean stress affects the vibration fatigue life and it can increase or decrease the fatigue damage depending upon the nature of the mean stress.
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Edge-Quality Effects on Mechanical Properties of Stamped Non-Oriented Electrical Steel

General Motors LLC-Peggy Jones, Margarita Thompson, Yew Sum Leong, Paul Crepeau
General Motors Technical Center India-Virupakshappa Lakkonavar, Swaroop Kavi
  • Technical Paper
  • 2020-01-1072
To be published on 2020-04-14 by SAE International in United States
The market for electric vehicles and hybrid electric vehicles is expected to grow in the coming years, which is increasing interest in design optimization of electric motors for automotive applications. Under demanding duty cycles, the moving part within a motor, the rotor, may experience varying stresses induced by centrifugal force, a necessary condition for fatigue.Rotors contain hundreds of electrical steel laminations produced by stamping, which creates a characteristic edge structure comprising rollover, shear and tear zones, plus a burr. Fatigue properties are commonly reported with specimens having polished edges. Since surface condition is known to affect fatigue strength, an experiment was conducted to evaluate the effect of sample preparation on tensile and fatigue behavior of stamped specimens.Tensile properties were unaffected by polishing. In contrast, polishing was shown to increase fatigue strength by approximately 10-20% in the range of 105-107 cycles to failure.
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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…