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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 Univ-Ken-ichi Manabe, Satoshi Kobayashi
Tokyo Metropolitan Univ.-Soichi Hareyama
  • 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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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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Strength Evaluation and Validation of Structural Joints.

VE Commercial Vehicles, Ltd.-Nikhil Soman, Ankit Desai
  • Technical Paper
  • 2020-01-0485
To be published on 2020-04-14 by SAE International in United States
Many methods have been developed to evaluate the fatigue life of structures when the its joints are as per ideal case. But if the joints are loosening, it leads to increase in loading on the other members which causes failures. Most commonly in commercial vehicle segment welding joint & Bolting joints are most popular ones. It is very easy to find out bolts strength & loosening effect in static conditions. But when vehicle is moving (i.e. dynamic condition), same method cannot be used. For this we have developed methodology to predict the bolts loosening in dynamic condition using vibration data. Similarly, loading may differ on the structural members if the welds are failing in dynamic conditions. To overcome this problem, in our organization we have a solution. Of course to simulate welding failures fatigue analysis is mandatory. We are using notch-stress approach for evaluating the welding strength of the joint. This method does not need weld material data instead it increases the amplitude stress appearing on nodes representing welding joint. We have correlated both 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. In addition, comparison of load carrying capacity and fatigue strength between SPR and resistance spot welded joints is also discussed.
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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 components. There are standard procedures to evaluate joint performance under block cycles or road loads. The deciding load case for such joint design is the 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 has provided a satisfactory method of quantifying the bolt loosening or loss of clamp under cyclic loading where initially no slippage is observed. Under varying loads, initial relaxation of the joint is followed by a loss of clamping load to below the critical value. Below a critical value, complete loss of clamping load happens very rapidly and 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…
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A Crack Detection Method for Self-Piercing Riveting Button Images through Machine Learning

Chongqing University-Ling Jiang, Xuyang Wang, Zhenfei Zhan
Ford Motor Company-Li Huang, Shiyao Huang, Garret Huff, Amanda Freis
  • Technical Paper
  • 2020-01-0221
To be published on 2020-04-14 by SAE International in United States
Self-piercing riveting (SPR) is a key joining technique for lightweight materials, and it has been widely used in the automobile manufacturing. Manual visual crack inspection of SPR joints could be time-consuming and might rely on high-level training for engineers to distinguish features subjectively. This paper presents a machine learning based crack detection method for SPR button images. Firstly, sub-images were cropped from the button images and preprocessed into three categories (cracks, edges, others) as training samples. Then, Artificial Neural Network (ANN) was chosen as the classification algorithm for sub-images. During the training of ANN, three pattern descriptors were proposed as feature extractors of sub-images respectively, and compared with validation samples. Lastly, a search algorithm was developed to extend the application of the learned model from sub-images to the original button images. The preliminary results on non-cracked and cracked button images show that the proposed crack detection method could achieve an acceptable performance.
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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 PhD
  • Technical Paper
  • 2020-01-0189
To be published on 2020-04-14 by SAE International in United States
According to increasing the demands of light-weight design in the automotive industry, the usage of thinner and lighter materials such as aluminum alloy has led to significant weight reduction. The joining of these materials has required new technologies in joining/fastening rather than welding. Flow drill screw (FDS) is one of the latest technologies to fasten sheet metal panels. This paper discusses the results of an evaluation of the fatigue characteristics of FDS joints based on experimental data and observations from the literature. It was observed that the important geometric parameters of FDS joints are the gap between panels and the extruded (or bulged) zone during screwing. Major failure modes were observed as panel failure which cracks grow from the inner surface of the panel around the bulged zone. In this paper, the fatigue evaluation procedure for FDS joints using the mesh-insensitive equilibrium-based structural stress (ESS) method was proposed. The ESS-based simplified modeling procedure was used for the fatigue evaluation procedure development for FDS joints. The effectiveness and applicability of the ESS-based simplified procedure for modeling…
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Analysis of Sheet Metal Joining with Self-Piercing Riveting

Oakland Univ.-Sergey Golovashchenko
Oakland University-Srecko Zdravkovic
  • 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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An extended structural stress method for predicting fatigue life of non-welded axle components

AAM (American Axle & Mfg Inc)-Anoop Vasu, Shizhu Xing, Jifa Mei, William Webster, Scott Jacob, Jerry Chung
American Axle & Manufacturing-Ravi Desai
  • Technical Paper
  • 2020-01-0606
To be published on 2020-04-14 by SAE International in United States
Leaking in a cover-pan of an axle assembly can result in severe durability issues. Preliminary tests of axle assembly for a fore-aft beaming test (replicating the load on the axle while accelerating or decelerating the vehicle) exhibited MPI indications of crack/leak adjacent to multiple bolt holes on the cover-pan. FEA results were able to capture the critical locations accurately. However, the crack initiation predictions were extremely conservative in nature due to the stress riser next to the bolted joints. Testing also indicated that a surface crack due to the bolt-edge-contact could withstand significant load cycles before a leak is formed (through thickness crack in the cover-pan). A unique simulation framework is implemented to perform the crack propagation life of the axle component. Traction structural stress method, build to predict the propagation life of welded components, was extended to predict the life of non-welded components. Unlike the welded components, mean-stress effect needs to be considered for predicting the propagation life. The test results from multiple axle designs indicate that the suggested method could predict the cover-pan…
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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…