Analysis of Brazing Stresses in Ceramic-Metal Joints in High-Vacuum Devices

1989 ◽  
Vol 111 (1) ◽  
pp. 21-25 ◽  
Author(s):  
K. L. De Weese ◽  
C. E. Toups ◽  
C. K. H. Dharan
Keyword(s):  
Temperature Dependence ◽  
Material Properties ◽  
High Vacuum ◽  
Nonlinear Behavior ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Metallographic Analysis ◽  
Analysis Model ◽  
Element Analysis ◽  
Sample Test

Significant stresses are induced in brazed metal-to-ceramic joints during cool-down. Analysis of such stresses is complicated by nonlinear material behavior and uncertainties in material properties at and near the braze temperatures. In this study, stresses induced during cool-down from the brazing temperature are analytically determined for a coaxial RF (radio frequency) window, which is an integral component of many traveling-wave tube (TWT) devices. The approach is to use nonlinear finite element analysis which takes into account plastic deformation of the metal components as well as the temperature dependence of material properties. Details of the modeling techniques, analytical assumptions and boundary conditions employed are discussed. In addition, metallographic analysis of the brazed test assemblies is described. Analytically predicted stress distributions showed reasonably good correlation with both the location and direction of cracks observed in the ceramic component of brazed sample test assemblies. The results of this investigation emphasize the need for accurate material properties for the braze alloys used in such joints, including temperature dependence, as well as an understanding of their nonlinear behavior, for the stress analysis model to be accurate. In addition, the important role of joint geometry in the minimization of cool-down stresses in brazed metal-ceramic assemblies is described.

scholarly journals Impact of residual stress evoked by pyramidal embossing on the magnetic material properties of non-oriented electrical steel

2021 ◽  
Author(s):  
Ines Gilch ◽  
Tobias Neuwirth ◽  
Benedikt Schauerte ◽  
Nora Leuning ◽  
Simon Sebold ◽  
...  
Keyword(s):  
Magnetic Material ◽  
Residual Stress ◽  
Magnetic Flux ◽  
Material Properties ◽  
Electrical Steel ◽  
Maximum Energy ◽  
Material Behavior ◽  
Electrical Machine ◽  
Element Analysis ◽  
Steel Sheets

AbstractTargeted magnetic flux guidance in the rotor cross section of rotational electrical machines is crucial for the machine’s efficiency. Cutouts in the electrical steel sheets are integrated in the rotor sheets for magnetic flux guidance. These cutouts create thin structures in the rotor sheets which limit the maximum achievable rotational speed under centrifugal forces and the maximum energy density of the rotating electrical machine. In this paper, embossing-induced residual stress, employing the magneto-mechanical Villari effect, is studied as an innovative and alternative flux barrier design with negligible mechanical material deterioration. The overall objective is to replace cutouts by embossings, increasing the mechanical strength of the rotor. The identification of suitable embossing geometries, distributions and methodologies for the local introduction of residual stress is a major challenge. This paper examines finely distributed pyramidal embossings and their effect on the magnetic material behavior. The study is based on simulation and measurements of specimen with a single line of twenty embossing points performed with different punch forces. The magnetic material behavior is analyzed using neutron grating interferometry and a single sheet tester. Numerical examinations using finite element analysis and microhardness measurements provide a more detailed understanding of the interaction of residual stress distribution and magnetic material properties. The results reveal that residual stress induced by embossing affects magnetic material properties. Process parameters can be applied to adjust the magnetic material deterioration and the effect of magnetic flux guidance.

scholarly journals Nonlinear Material Behavior Analysis under High Compression Pressure in Dynamic Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Muhammad Zubair Zahid ◽  
Shahid Ikramullah Butt ◽  
Tauqeer Iqbal ◽  
Syed Zohaib Ejaz ◽  
Zhang Faping
Keyword(s):  
High Pressures ◽  
Cost Benefit Analysis ◽  
Nonlinear Behavior ◽  
Cost Benefit ◽  
Piezoelectric Sensor ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Chamber Pressure ◽  
Compression Pressure ◽  
Pressure Transducers

Gun chamber pressure is an important parameter in proofing of ammunition to ensure safety and reliability. It can be measured using copper crushers or piezoelectric sensor. Pressure calculations in copper crusher method are based on linear plastic deformation of copper after firing. However, crusher pressure deformation at high pressures deviates from the corresponding values measured by piezoelectric pressure transducers due to strain rate dependence of copper. The nonlinear deformation rate of copper at high pressure measurements causes actual readings from copper crusher gauge to deviate from true pressure values. Comparative analysis of gun chamber pressure was conducted for 7.62 × 51 mm ammunition using Electronic Pressure, Velocity, and Action Time (EPVAT) system with piezoelectric pressure transducers and conventional crusher gauge. Ammunitions of two different brands were used to measure chamber pressure, namely, NATO standard ammunition and non-NATO standard ammunition. The deformation of copper crushers has also been simulated to compare its deformation with real time firing. The results indicate erratic behavior for chamber pressure by copper crusher as per standard deviation and relative spread and thus prove piezo sensor as more reliable and consistent mode of peak pressure measurement. The results from simulation, cost benefit analysis, and accuracy clearly provide piezo sensors with an edge over conventional, inaccurate, and costly method of copper crusher for ballistic measurements due to its nonlinear behavior.

Finite Element Analysis on Nitinol Medical Applications

2002 ◽  
Author(s):  
Xiao-Yan Gong ◽  
Alan R. Pelton
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Element Analysis ◽  
Highly Nonlinear ◽  
Device Applications ◽  
Specific Material

Nitinol, an alloy of about 50% Ni and 50% Ti, is a very unique material. At constant temperature above its Austenite finish (Af) temperature, under uniaxial tensile test, the material is highly nonlinear and capable of large deformation to the ultimate strain on the order of 15%. This material behavior, known as superelasticity, along with its excellent biocompatibility and corrosion resistance, makes Nitinol a perfect material candidate for many medical device applications. However, the nonlinear material response also requires a specific material description to perform the stress analysis. The user developed material subroutine from HKS/West makes the simulation of the Nitinol devices possible. This article presents two case studies of the nonlinear finite element analysis using ABAQUS/Standard and the Nitinol UMAT.

scholarly journals Modeling of Nonlinear Material Behavior in Microstructurally Engineered Ferroelectric Ceramics

2007 ◽  
Author(s):  
Joshua Robbins ◽  
Pavel M. Chaplya
Keyword(s):  
Residual Stress ◽  
Material Properties ◽  
Remanent Polarization ◽  
Material Behavior ◽  
Ferroelectric Ceramics ◽  
Nonlinear Material ◽  
Problem Domain ◽  
Polycrystalline Structure ◽  
Linear Behavior ◽  
Random Microstructure

Ferroelectric ceramics can be tailored at the microscale to have an ordered arrangement of crystal axes. Such grain-oriented ceramics can exhibit material properties far superior to conventional ceramics with random microstructure. A microstructurally based numerical model has been developed that describes the 3D non-linear behavior of ferroelectric ceramics. The model resolves the polycrystalline structure directly in the topology of the problem domain. The developed model is used to predict the effect of microstructural modifications on material behavior. In particular, we examine the internal residual stress after poling for idealized configurations of random and grain-oriented microstructures. The results indicate that a grain-ordered microstructure produces a significant increase in remanent polarization without detriment to internal residual stress.

Analytical Methodology for Evaluating Stress and Strain of Pipeline Exposed in Flood

2010 ◽  
Author(s):  
Xiaolin Wang ◽  
Jian Shuai ◽  
Xiaomin Guo
Keyword(s):  
Large Scale ◽  
Pipeline Steel ◽  
Limit State ◽  
Assessment Method ◽  
State Theory ◽  
Nonlinear Material ◽  
Stress And Strain ◽  
Analysis Model ◽  
Element Analysis ◽  
Analytical Methodology

River-crossing pipeline is threatened by flood which could induce pipeline being eroded and exposed, moreover, floating in a large scale. Under the combined effects of dynamic wave, buoyancy, gravity and resistance of bank soil, pipeline presents spatial deformation. A mechanical analysis model is built according to loadings on pipeline and deformation of pipeline. Taking into account nonlinear soil-pipe interaction, axial force, nonlinear material property of pipeline steel and spacial deformation of pipeline, an analytical methodology for evaluating pipeline deformation and stress distribution is developed. Compatibility equation of pipeline physical elongation and geometrical elongation is derived, by which pipeline stress and strain are calculated with iterative method. Based on proposed methodology, a computer program is developed and a series of cases of pipeline in flood are analyzed with it. Compared with finite element analysis, results of proposed methodology are well accepted. Finally, safety assessment method for pipeline in flood is proposed based on limit state theory and the safety of pipeline exposed in mountain torrent are evaluated.

scholarly journals Coupled Multi-Disciplinary Simulation of Composite Engine Structures in Propulsion Environment

1992 ◽  
Author(s):  
Christos C. Chamis ◽  
Surendra N. Singhal
Keyword(s):  
Acoustic Analysis ◽  
Acoustic Noise ◽  
Computational Simulation ◽  
Aircraft Engine ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Element Analysis ◽  
Composite Mechanics

A computational simulation procedure is described for the coupled response of multi-layered multi-material composite engine structural components which are subjected to simultaneous multi-disciplinary thermal, structural, vibration, and acoustic loadings including the effect of hostile environments. The simulation is based on a 3D finite element analysis technique in conjunction with structural mechanics codes and with the acoustic analysis methods. The composite material behavior is assessed at the various composite scales, i.e., the laminate/ply/fiber and matrix constituents, via a nonlinear material characterization model. Sample cases exhibiting nonlinear geometrical, material, loading, and environmental behavior of aircraft engine fan blades, are presented. Results for deformed shape, vibration frequencies, mode shapes, and acoustic noise emitted from the fan blade, are discussed for their coupled effect in hot and humid environment. Results such as acoustic noise for coupled composite-mechanics/heat transfer/structural/vibration/acoustic analyses demonstrate the effectiveness of coupled multi-disciplinary computational simulation and the various advantages of composite materials compared to metals.

Finite Element Analysis of Composite Piezoelectric Actuators Incorporating Nonlinear Material Behavior

2010 ◽  
Author(s):  
M. A. Siddiq Qidwai ◽  
Virginia G. DeGiorgi
Keyword(s):  
Electric Field ◽  
Predictive Modeling ◽  
Nonlinear Modeling ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Element Analysis ◽  
Linear Material ◽  
Bimorph Actuators ◽  
Computational Resources ◽  
The Impact

There is always the question of choosing the appropriate constitutive model when simulating and analyzing piezoelectric material performance. Linear material modeling typically requires less computational resources; however this approach may not accurately capture the performance. In this paper, the scope of linear predictive modeling was analyzed by comparison with nonlinear modeling. Monomorph and bimorph actuators were modeled with each approach, and their respective performances were compared. It was found that even under small magnitudes of electric field, differences arise between the two approaches. The magnitude of the deviations depended upon actuator composition, applied electric field and boundary conditions. The impact of these differences can be considerable, such as for precision-based applications and cyclic applications where initial design errors could compound.

Analysis of Effects of a Double-Tube Parallel Tunnel Excavation on Underground Pipelines

2013 ◽  
Vol 395-396 ◽  
pp. 477-480
Author(s):  
Dong Liang Guo ◽  
De Shen Zhao
Keyword(s):  
Material Properties ◽  
Its Region ◽  
Underground Pipeline ◽  
Analysis Model ◽  
Element Analysis ◽  
Tunnel Excavation ◽  
Finite Element Analysis Model ◽  
Underground Pipelines ◽  
Deformation Law ◽  
Parallel Tunnel

The interaction of a double-tube parallel tunnel excavation will greatly influence on underground pipeline of its region. This paper, taking Dalian Spring Street subway station as the background, uses the finite difference software to establish 3-D finite element analysis model to simulate the effects of tunnel excavation on underground pipeline, in which different embedment, material properties and diameters are considered. By analyzing of the settlement and deformation law of pipeline, the least affected pipeline conditions are drawn to provide corresponding guidance for subsequent underground projects.

Response of Dolos Concrete Armor Units to Impact Loads

1991 ◽  
Vol 113 (4) ◽  
pp. 286-291 ◽  
Author(s):  
J. W. Tedesco ◽  
P. B. McGill ◽  
W. G. McDougal
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Concrete Strength ◽  
Impact Resistance ◽  
Nonlinear Material ◽  
Impact Loads ◽  
Model Formulation ◽  
Element Analysis ◽  
The Impact

A finite element analysis is conducted to determine the critical impact velocities for concrete dolos. The model formulation includes deformations at the contact surface and nonlinear material properties. Two dolos orientations are considered: vertical fluke seaward and horizontal fluke seaward. In both cases, the larger units fail at lower angular impact velocities. It is also shown that doubling the concrete strength increases the impact resistance by approximately 40 percent.

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