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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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Research on Joining High Pressure Die Casting Parts by Self-Pierce Riveting (SPR) using Ring-Groove Die Comparing to Heat Treatment Method

Bollhoff Inc.-Xuzhe Zhao
Chang’an University-Dean Meng
  • Technical Paper
  • 2020-01-0222
To be published on 2020-04-14 by SAE International in United States
Nowadays, the increasing number of structural high pressure die casting (HPDC) aluminum parts need to be joined with high strength steel (HSS) parts in order to reduce the weight of vehicle for fuel-economy considerations. Self-Pierce Riveting (SPR) has become one of the strongest mechanical joining solutions used in automotive industry for the past several decades. Joining HPDC parts with HSS parts can potentially cause joint quality issues, such as joint button cracks, low corrosion resistance and low joint strength. The appropriate heat treatment will be suggested to improve SPR joint quality in terms of crack reduction. But the heat treatment can also result in the blister issue and extra time and cost consumption for HPDC parts. The relationship between the microstructure of HPDC material before and after heat treatment with the joint quality is going to be investigated and discussed for interpretation of cracks initiation and propagation during riveting. The SPR joint quality will be evaluated based on interlock distance, the minimum remaining thickness (Tmin), shear strength etc. Instead of using heat treatment method, the…
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Experimental Study on Static and Fatigue Performance of Self-Piercing Riveted Joints and Adhesively Bonded Self-Piercing Riveted Joints Connecting Steel and Aluminum Components

FCA US LLC-Mingchao Guo, Ghassan El-Tawil
  • Technical Paper
  • 2020-01-0177
To be published on 2020-04-14 by SAE International in United States
This paper describes an experimental study on the performance of self-piercing riveted (SPR) joints and adhesively bonded SPR joints connecting steel and aluminum components under both quasi-static and cyclic loading. The joint configurations cover a wide range of material gauges, types and grades. Two and three thickness joints, with and without adhesive are also part of this study. Load versus deflection behavior, load carrying capacity, fatigue life and the failure modes for each type of joint are discussed. This study focuses on the influence of dissimilar material and adhesives to the joint performance.
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Quantification of Clamp Loss and Subsequent Loosening of Automotive Hub-Knuckle Joints under Time-Varying Proving Ground Loading

FCA US LLC-Sandip Datta, Parag Nittur
  • Technical Paper
  • 2020-01-0181
To be published on 2020-04-14 by SAE International in United States
Threaded fasteners or bolted joints are used extensively in automotive assemblies. There are standard procedures to evaluate joint performance under block cycles or road loads. The deciding load case for such joint design is slippage analysis of the joint.There are studies done to evaluate the theoretical and experimental behavior of these joints. There are different ways of understanding the interaction between the bolt and the nut under different loading scenarios. However, none have provided a satisfactory method of quantifying bolt loosening or loss of clamp load under cyclic loading, where no slippage is observed.Under varying loads, initial relaxation of the joint is followed by a loss of clamping load. Below a critical value, complete loss of clamping load progresses very rapidly and this results in a loose joint. The loss of clamping load below the critical value happens at a transition stage when both elastic deformations of the bolt as well as external moments contribute to rapid loosening.This study provides an overall understanding of geometric parameters that contribute to sudden loss of clamping load and…
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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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Analysis of Sheet Metal Joining with Self-Piercing Riveting

Oakland University-Srecko Zdravkovic, Sergey Golovashchenko
  • Technical Paper
  • 2020-01-0223
To be published on 2020-04-14 by SAE International in United States
Self-piercing riveting (SPR) has been in production in automotive industry since early 1990s. A substantial amount of experimental work was traditionally required in order to find an appropriate combination of rivet and anvil design to satisfy the required joint parameters. Presented study is describing the methodology of numerical simulation of SPR process and its experimental validation for Aluminum alloys and steels. Among material properties, the required information for numerical simulation includes stress-strain curves validated for the range of strains taking place in SPR process (up to 2.0 of true strain for sheets and up to 0.4 of true strain for the rivet) and parameters of fracture model for all involved materials: all sheets in the stack and the rivet material. Experimental data on stress-strain curves for extended range of strains was obtained based upon multistep rolling tensile testing procedure for the sheet metals. Parameters of the fracture model for sheets were defined by custom hole expansion test, and the parameter of the fracture model for the rivet was defined via expanding the tubular portion of…
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Evaluation of High Resistance Connection in Automotive Application

General Motors LLC-Manoj Modi, Brad Galgoci
  • Technical Paper
  • 2020-01-0926
To be published on 2020-04-14 by SAE International in United States
Electrical connections have a normal operational temperature range. A high resistance, such as a poor connection, in an electrical circuit has been reported to cause a temperature increase exceeding normal operational range at the connection.This study measures the temperature increase in a typical automotive bolted battery cable connection with low to zero torque values and simulated high resistance under different load conditions. The torque is changed from maximum design value to 0 Nm and the temperature increase at the connection is measured. The high resistance connections, manually created by adjusting the contacts, are tested for several power loss values at the connection. The temperature rise under these conditions at the connection is measured and subsequently recorded.The maximum temperature increase at the bolted cable connection recorded at low torque values including 0 Nm torque compared to the maximum typical design value of 17 Nm is 10.5 °C. The maximum temperature increase for the high resistance bolted connection is a function of the power loss and the voltage drop at the connection.
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Predicting Fatigue Life of Axle Components: A Unique Modeling Approach

American Axle & Manufacturing, Inc.-Anoop Vasu, Shizhu Xing, Jifa Mei, William Webster, Scott Jacob, Jerry Chung, Ravi Desai
  • Technical Paper
  • 2020-01-0606
To be published on 2020-04-14 by SAE International in United States
Loss of lubrication within an axle assembly due to the formation of through-thickness cracks in structural components can result in severe durability issues for the internal parts (gears, splines, bearings, etc.). One such example of a structural crack resulting in lubrication leakage can be observed in the cover pan of a Salisbury axle that has been subjected to cyclic fore-aft loading conditions (which are intended to replicate the loads acting on the axle during vehicle acceleration or deceleration). Investigation of the cover pan crack locations was performed using Magnetic Particle Inspection (MPI) and indicated the formation and propagation of multiple cracks adjacent to the cover pan bolt holes. Finite Element Analysis (FEA) was performed in order to simulate the fore-aft beaming test and was able to successfully identify the critical crack locations; however, crack initiation calculations yielded extremely conservative predictions, likely resulting from the large stress-riser induced by the pretensioned bolted joint. Additional physical testing intended to characterize the propagation of a surface crack initiating at a bolt-edge-contact location showed that an SAE 1010 steel…
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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
This paper describes a study on identifying a suitable thickness for finite element modeling a “deformable washer” to simulate bolted joints for vehicle level durability analysis based on experimental results. First, a test matrix table is introduced, which is based on representative vehicle structures for different bolt/nut sizes, bolt grades, sheet gages, and sheet materials etc. Then coupon tests, both static and fatigue, are illustrated. Next, the corresponding finite element model with different thickness of “deformable washers” and results are presented. Following that, the optimal “deformable washer” thickness is recommended based on statistical parameters (mean and standard deviation) of the relative differences between finite element analysis results and physical test results. Lastly, a case study is demonstrated for the proposed strategy. The results indicate that the recommended modeling strategy overcomes the limitations of rigid element (RBE2) connections for bolt joint modeling and predicts reasonable results comparable to the physical test results.
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Nuts, Self-Locking, Nickel Alloy, UNS N07001 Classification: 180 ksi/1400 °F Procurement Specification

E-25 General Standards for Aerospace and Propulsion Systems
  • Aerospace Standard
  • AS7253C
  • Current
Published 2020-04-06 by SAE International in United States
This procurement specification covers all metal, self-locking wrenching nuts, plate nuts, shank nuts, and gang channel nuts made of a corrosion and heat resistant nickel-base alloy of the type identified under the Unified Numbering System as UNS N07001.
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