Numerical Study of the Percussive Riveting Process: Initial Results

2019 ◽  
Author(s):  
Sai C. Krovvidi ◽  
M. Ramulu ◽  
Per G. Reinhall
Keyword(s):  
Numerical Study ◽  
Bulk Material ◽  
Longitudinal Direction ◽  
Assembly Process ◽  
Dynamics Modeling ◽  
Assembly Method ◽  
Compressive Stresses ◽  
Riveting Process ◽  
Set Up ◽  
Residual Stresses And Strains

Abstract Percussive riveting is a dependable assembly method that produces high-quality joints in the aerospace industry. Its successful application is derived from its ease to implement in an assembly floor environment. The rivets are formed on the shank end of the rivet using a forming tool like a bucking bar and the head is constrained and impacted with a rapid succession of hits using a pneumatic gun with a special purpose die head. The rivet forms an interference fit joint because of the residual compressive stresses that are set up in the circumferential direction due to plastic flow of rivet material. These compressive stresses are balanced by tensile stresses in the skin and stiffener bulk material. Compressive stresses in the longitudinal direction help keep the skins pressed together. Research studies focused on the dynamics modeling of the percussive riveting process for robotic automation have not delivered an understanding of the temporal evolution of stress and strain fields in the vicinity of the rivet and the rivet hole. These studies aimed to produce joints of equal strength using automated assembly process compared with the manual assembly process. No modeling efforts have been published up to this point in time. This understanding is important in order to produce joints of predictable strength. A simulation effort for an unstiffened percussive riveting stackup assembly will be undertaken to study the trends of beneficial compressive residual stresses and strains within the bucked rivet. It is our goal to eventually estimate joint strength for prescribed sets of joint assembly parameters. The domain of interest will be restricted to few inches from the rivet axis.

Numerical Study of the Percussive Riveting Process: Simulation Results

2020 ◽  
Author(s):  
Sai C. Krovvidi ◽  
M. Ramulu ◽  
Per G. Reinhall
Keyword(s):  
Fatigue Strength ◽  
Numerical Study ◽  
Material Model ◽  
Thermomechanical Model ◽  
Strain Rate Effects ◽  
Assembly Method ◽  
Riveting Process ◽  
Assembly Technique ◽  
Residual Strains ◽  
Set Up

Abstract Percussive riveting is a widely used assembly method in the aerospace industry. The joints produced using this technique have consistently high fatigue strength. It is a manual assembly technique but automation has been introduced in certain instances on the work floor to assist assembly workers. In this paper, study was set up to analyze the effect of important geometric parameters on the residual stress and strain distributions within the riveting stackup. In the current paper, a realistic set of boundary conditions have been adopted with both movable riveting die and movable bucking bar in an axisymmetric thermomechanical model that has a countersunk rivet. The knowledge of this evolution is important to gain understanding of the differences between quasi-static squeeze riveting process and the percussive riveting process. The distribution of residual strains and stresses play an important role in influencing the fatigue strength of the assembled joined. Most if not all of the percussive research till date is focused on the process automation advances but enough work has not been done to understand the properties of the assembled joint using the percussive technique. The percussive results will be compared with quasi-static squeeze process results. Strain rate effects and thermal effects are negligible in the quasi-static process while these effects are present in the percussive process. So, the results and observations from quasi-static DOE will be used as a benchmark against which the percussive DOE results will be compared. The Johnson-Cook material model has been used for describing the flow stress of the alloys used in the percussive process.

scholarly journals Research of the reliability of a robotic assembly based on the effect of rotation and low-frequency vibrations

2021 ◽  
Vol 2131 (5) ◽  
pp. 052026
Author(s):  
M V Vartanov ◽  
T T Tran
Keyword(s):  
Mathematical Model ◽  
Rotational Motion ◽  
Low Frequency ◽  
Robotic Assembly ◽  
Assembly Process ◽  
Automatic Assembly ◽  
Rotational Movement ◽  
Assembly Method ◽  
Set Up ◽  
Technological Mode

Abstract Using various physical and technical effects in automatic assembly is a promising tendency to increase the technological reliability of the assembly process. The article presents a method for robotic assembly of cylindrical joints using the effect of rotational motion and low-frequency vibrations. The effect can be achieved by using low-frequency vibrations of the base part with the help of a vibrating device and the rotational movement of the installed part with the help of the rotational movement of the robot out-put link. The paper presented a mathematical model of the dynamics of the robotic assembly process of cylindrical joints. Experiments were set up and carried out to test the effectiveness of the proposed assembly method. The research results affirmed that with a rational technological mode of the robotic assembly process using the effect of rotation and low-frequency vibrations, the probability of jamming is completely eliminated and the assembly force is significantly reduced.

scholarly journals Concept for controlled adjustment of residual stress states in semi-finished products by gradation extrusion

2021 ◽  
Author(s):  
René Selbmann ◽  
Markus Baumann ◽  
Mateus Dobecki ◽  
Markus Bergmann ◽  
Verena Kräusel ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Experimental Tests ◽  
Residual Stress Distribution ◽  
Forming Process ◽  
Compressive Stresses ◽  
Energy Consuming ◽  
Stress States ◽  
Set Up ◽  
Time And Energy

AbstractThe residual stress distribution in extruded components and wires after a conventional forming process is frequently unfavourable for subsequent processes, such as bending operations. High tensile residual stresses typically occur near the surface of the wire and thus limit further processability of the material. Additional heat treatment operations or shot peening are often inserted to influence the residual stress distribution in the material after conventional manufacturing. This is time and energy consuming. The research presented in this paper contains an approach to influence the residual stress distribution by modifying the forming process for wire-like applications. The aim of this process is to lower the resulting tensile stress levels near the surface or even to generate compressive stresses. To achieve these residual compressive stresses, special forming elements are integrated in the dies. These modifications in the forming zone have a significant influence on process properties, such as degree of deformation and deformation direction, but typically have no influence on the diameter of the product geometry. In the present paper, the theoretical approach is described, as well as the model set-up, the FE-simulation and the results of the experimental tests. The characterization of the residual stress states in the specimen was carried out by X-ray diffraction using the sin2Ψ method.

scholarly journals Fast Two-Stage Computation of an Index Policy for Multi-Armed Bandits with Setup Delays

Mathematics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 52
Author(s):  
José Niño-Mora
Keyword(s):  
Numerical Study ◽  
Arithmetic Operation ◽  
Bandit Problem ◽  
Index Policy ◽  
Two Stage ◽  
Second Stage ◽  
Whittle Index ◽  
Set Up ◽  
Computing Method ◽  
Special Case

We consider the multi-armed bandit problem with penalties for switching that include setup delays and costs, extending the former results of the author for the special case with no switching delays. A priority index for projects with setup delays that characterizes, in part, optimal policies was introduced by Asawa and Teneketzis in 1996, yet without giving a means of computing it. We present a fast two-stage index computing method, which computes the continuation index (which applies when the project has been set up) in a first stage and certain extra quantities with cubic (arithmetic-operation) complexity in the number of project states and then computes the switching index (which applies when the project is not set up), in a second stage, with quadratic complexity. The approach is based on new methodological advances on restless bandit indexation, which are introduced and deployed herein, being motivated by the limitations of previous results, exploiting the fact that the aforementioned index is the Whittle index of the project in its restless reformulation. A numerical study demonstrates substantial runtime speed-ups of the new two-stage index algorithm versus a general one-stage Whittle index algorithm. The study further gives evidence that, in a multi-project setting, the index policy is consistently nearly optimal.

Load Characteristics of Steel and Concrete Tubular Members Under Jet Fire: An Experimental and Numerical Study

2010 ◽  
Author(s):  
Jeong Hyo Park ◽  
Bong Ju Kim ◽  
Jung Kwan Seo ◽  
Jae Sung Jeong ◽  
Byung Keun Oh ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Numerical Study ◽  
Fire Load ◽  
Adiabatic Wall ◽  
Fire Engineering ◽  
Ansys Cfx ◽  
Design Values ◽  
Computational Fluid Dynamics Cfd ◽  
Load Characteristics ◽  
Set Up

The aim of this study was to evaluate the load characteristics of steel and concrete tubular members under jet fire, with the motivation to investigate the jet fire load characteristics in FPSO topsides. This paper is part of Phase II of the joint industry project on explosion and fire engineering of FPSOs (EFEF JIP) [1]. To obtain reliable load values, jet fire tests were carried out in parallel with a numerical study. Computational fluid dynamics (CFD) simulation was used to set up an adiabatic wall boundary condition for the jet fire to model the heat transfer mechanism. A concrete tubular member was tested under the assumption that there is no conduction effect from jet fire. A steel tubular member was tested and considered to transfer heat through conduction, convection, and radiation. The temperature distribution, or heat load, was analyzed at specific locations on each type of member. ANSYS CFX [2] and Kameleon FireEx [3] codes were used to obtain similar fire action in the numerical and experimental methods. The results of this study will provide a useful database to determine design values related to jet fire.

Numerical Study of Methane and Air Combustion Inside Heat-Recirculating Combustors

2013 ◽  
Author(s):  
Yanxia Li ◽  
Zhongliang Liu ◽  
Yan Wang ◽  
Jiaming Liu
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Central Area ◽  
Small Scale ◽  
Inlet Velocity ◽  
Strong Convection ◽  
Simulation Results ◽  
Lean Fuel ◽  
Set Up

A numerical model on methane/air combustion inside a small Swiss-roll combustor was set up to investigate the flame position of small-scale combustion. The simulation results show that the combustion flame could be maintained in the central area of the combustor only when the speed and equivalence ratio are all within a narrow and specific range. For high inlet velocity, the combustion could be sustained stably even with a very lean fuel and the flame always stayed at the first corner of reactant channel because of the strong convection heat transfer and preheating. For low inlet velocity, small amounts of fuel could combust stably in the central area of the combustor, because heat was appropriately transferred from the gas to the inlet mixture. Whereas, for the low premixed gas flow, only in certain conditions (Φ = 0.8 ～ 1.2 when ν0 = 1.0m/s, Φ = 1.0 when ν0 = 0.5m/s) the small-scale combustion could be maintained.

scholarly journals Comparison Between Experiments and a Multibody Weakly Nonlinear Potential Flow Approach for Modeling of Marine Operations

2018 ◽  
Author(s):  
Pierre-Yves Wuillaume ◽  
Pierre Ferrant ◽  
Aurélien Babarit ◽  
François Rongère ◽  
Mattias Lynch ◽  
...  
Keyword(s):  
Potential Flow ◽  
Wave Structure ◽  
Body Motion ◽  
Dynamics Modeling ◽  
Flow Solver ◽  
Weakly Nonlinear ◽  
Validation Test ◽  
Nonlinear Potential ◽  
Set Up ◽  
Validation Tests

This paper presents validation tests for a new numerical tool for the numerical simulation of marine operations. It involves multibody dynamics modeling, wave-structure interactions with large amplitude body motion and cable’s dynamic modeling. Hydrodynamic loads are computed using the WS_CN weakly nonlinear potential flow solver, based on the weak-scatterer hypothesis. Large deformation of the wetted body surfaces can be taken into account. Firstly the ECN’s WS_CN solver capabilities are extended to multibody simulations. A first validation test is performed by comparing numerical results to the experimental data of [1]. Then, a second validation test is proposed. It consists in the ballasting operation of a spar. The experimental set-up is described.

Mathematical model of a robotized assembly in the presence of vibrations and gripper rotation

2020 ◽  
pp. 299-304
Author(s):  
M.V. Vartanov ◽  
Trung Ta Tran
Keyword(s):  
Mathematical Model ◽  
Friction Force ◽  
Rotational Motion ◽  
Robotic Assembly ◽  
Assembly Process ◽  
Dynamics Model ◽  
Assembly Method ◽  
Robot Gripper

The assembly method using the effect of rotational motion and vibration is considered. The presence of rotation allows to signifi cantly reducing the friction force in connection, which prevents the assembly process. The effect is achieved due to using the rotation of robot gripper and the vibrating device. A mathematical dynamics model of the robotic assembly process is presented

Experimental and numerical study of flood dynamics in a river-network-floodplain set-up

2020 ◽  
Vol 22 (4) ◽  
pp. 793-814
Author(s):  
Vijay Kisan Mali ◽  
B. Veeranna ◽  
Aditya Parik ◽  
Soumendra Nath Kuiry
Keyword(s):  
Numerical Study ◽  
River Network ◽  
Channel Network ◽  
Flood Prediction ◽  
River Floodplain ◽  
Flood Simulations ◽  
Set Up ◽  
Flood Dynamics ◽  
Accurate Scheme ◽  
2D Model

Abstract Flood simulations demand mathematical models, which are rigorously calibrated and validated against benchmarking datasets. For this purpose, experiments are conducted in a river-network-floodplain set-up. Hypothetical stepped hydrographs are passed through the channel-network, and fluvial flooding situations are created. Flood depths are recorded at various locations and evolving flood extents are extracted by image processing. TELEMAC 2D is tested against the observed data. The most accurate scheme for flood prediction is identified through sensitivity analysis. Inclusion of the turbulence model is found to improve the accuracy in predicting dynamic flood extents. The model seems to slightly overpredict inundation extents during the rising limb of the hydrographs and underpredict during the falling limb. In addition, certain aspects of a flood such as river–floodplain interaction and junction hydraulics cannot be reproduced with high precision by the 2D model. The experimental datasets can be a valuable resource to mathematical modellers and are freely downloadable.

scholarly journals Experimental and Numerical Study of a Thermal Expansion Gyroscope for Different Gases

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 360 ◽  
Author(s):  
Guillaume Kock ◽  
Philippe Combette ◽  
Marwan Tedjini ◽  
Markus Schneider ◽  
Caroline Gauthier-Blum ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Gas Flow ◽  
Numerical Study ◽  
Rotational Velocity ◽  
Measurement Range ◽  
Gas Temperature ◽  
Hot Air ◽  
Working Principle ◽  
Set Up ◽  
Different Gases

A new single-axis gas thermal gyroscope without proof mass is presented in this paper. The device was designed, manufactured and experimentally characterized. The obtained results were compared to numerical simulation. The working principle of the gyroscope is based on the deflection of a laminar gas flow caused by the Coriolis effect. A bidirectional hot air flow is generated by alternating activation of two suspended resistive micro-heaters. The heated gas is encapsulated in a semi-open cavity and the gas expands primarily inside the cavity. The thermal expansion gyroscope has a simple structure. Indeed, the device is composed of a micromachined cavity on which three bridges are suspended. The central bridge is electrically separated into two segments enabling to set up two heaters which may be supplied independently from each other. The two other bridges, placed symmetrically on each side of the central bridge, are equipped with temperature detectors which measure variations in gas temperature. The differential temperature depends on the rotational velocity applied to the system. Various parameters such as the heating duty cycle, the type of the gas and the power injected into the heaters have been studied to define the optimal working conditions required to obtain the highest level of sensitivity over a measurement range of around 1000°/s. The robustness of the device has also been tested and validated for a shock resistance of 10,000 g for a duration of 400 µs.

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