A New Analytical Method for Calculating Maximum Junction Temperature of Packaged Devices Incorporating the Temperature Distribution at the Base of the Substrate

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
J. H. L. Ling ◽  
A. A. O. Tay
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Analytical Method ◽  
Analytical Methods ◽  
Thermal Analyses ◽  
Closed Form Solution ◽  
Form Solution ◽  
Junction Temperature ◽  
Uniform Temperature ◽  
Element Analysis

All current analytical methods for calculating junction temperature of field effect transistor (FET) and monolithic microwave integrated circuits (MMIC) devices have assumed a constant uniform temperature at the base of the substrate. In a packaged device, however, where the substrate is attached to a carrier, finite element thermal analyses have shown that the temperature distribution along the base of the substrate is not uniform but has a bell-shaped distribution. Consequently, current analytical methods which attempt to predict the junction temperature of a packaged MMIC device by assuming a constant uniform temperature at the base of the substrate have been found to be inaccurate. In this paper, it is found that the temperature distribution along the base of a substrate can be well approximated by a Lorentz distribution which can be determined from a few basic parameters of the device such as the gate length, gate pitch, number of gates, and length of substrate. By incorporating this Lorentz temperature distribution at the base of the substrate with a new closed-form solution for the three-dimensional temperature distribution within the substrate, a new analytical method is developed for accurately calculating the junction temperature of MMIC devices. The accuracy of this new method has been verified with junction temperatures of MMIC devices measured using thermoreflectance thermography (TRT) as well as those calculated using finite element analysis (FEA).

Analytical and Numerical Studies of a Thick Anisotropic Multilayered Fiber-Reinforced Composite Pressure Vessel

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Isaiah Ramos ◽  
Young Ho Park ◽  
Jordan Ulibarri-Sanchez
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Structural Damage ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
Analytical Results ◽  
Composite Pressure Vessel

In this paper, we developed an exact analytical 3D elasticity solution to investigate mechanical behavior of a thick multilayered anisotropic fiber-reinforced pressure vessel subjected to multiple mechanical loadings. This closed-form solution was implemented in a computer program, and analytical results were compared to finite element analysis (FEA) calculations. In order to predict through-thickness stresses accurately, three-dimensional finite element meshes were used in the FEA since shell meshes can only be used to predict in-plane strength. Three-dimensional FEA results are in excellent agreement with the analytical results. Finally, using the proposed analytical approach, we evaluated structural damage and failure conditions of the composite pressure vessel using the Tsai–Wu failure criteria and predicted a maximum burst pressure.

Validation of Nitinol SMA Characteristics Using Finite Element Analysis and Closed Form Solutions

2013 ◽  
Vol 856 ◽  
pp. 147-152
Author(s):  
S.H. Adarsh ◽  
U.S. Mallikarjun
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fe Analysis ◽  
Element Analysis ◽  
Complex Behaviour ◽  
Closed Form Solutions

Shape Memory Alloys (SMA) are promising materials for actuation in space applications, because of the relatively large deformations and forces that they offer. However, their complex behaviour and interaction of several physical domains (electrical, thermal and mechanical), the study of SMA behaviour is a challenging field. Present work aims at correlating the Finite Element (FE) analysis of SMA with closed form solutions and experimental data. Though sufficient literature is available on closed form solution of SMA, not much detail is available on the Finite element Analysis. In the present work an attempt is made for characterization of SMA through solving the governing equations by established closed form solution, and finally correlating FE results with these data. Extensive experiments were conducted on 0.3mm diameter NiTinol SMA wire at various temperatures and stress conditions and these results were compared with FE analysis conducted using MSC.Marc. A comparison of results from finite element analysis with the experimental data exhibits fairly good agreement.

Strengthening of wide-flange columns under load

1990 ◽  
Vol 17 (5) ◽  
pp. 835-843 ◽  
Author(s):  
H. Marzouk ◽  
S. Mohan
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Critical Load ◽  
Closed Form Solution ◽  
Welding Process ◽  
Form Solution ◽  
Element Analysis ◽  
Welding Stress ◽  
Existing Structures ◽  
Welding Sequence

The present work deals with formulation of theoretical and analytical methods leading to the development of column strength curves. The formulations were developed for both elastic and inelastic behaviour. Two types of reinforcement have been developed for strengthening the W-shape columns under load. Since the column strength curves are based in part on the magnitude and distribution of residual stresses, it is extremely important to consider the new pattern of residual stresses due to welding process. Also, the welding sequence will affect the magnitude and distribution of residual stresses. Theoretical formulations leading to a closed-form solution for the prediction of critical load were developed for two types of strengthening using the superposition of original residual, new welding, and initial loading stresses. A nonlinear finite element analysis based on the large deformation theory of stability was used to predict the strengthened column critical load. It takes into consideration the effect of cooling residual stresses and new welding residual stresses. The formulations were incorporated with gradual penetration of yielding, the spreading of inelastic zones along the member length, the presence of residual stresses, and strain hardening of the material. Experiments were carried out to determine the actual capacity of strengthened columns. Seven specimens were tested using two and four strengthening plates. The welding stresses were measured through a series of experiments, and it was found that the parabolic distribution is a very close approximation to the actual new welding stress distribution. Key words: reinforcement of steel columns, welding stresses, welding sequence, strengthening of existing structures, buckling, steel plating, finite element.

Using Isochronous Method to Calculate Creep Damage in Pressure Vessel Components: Part 2

2017 ◽  
Author(s):  
Chithranjan Nadarajah ◽  
Benjamin F. Hantz ◽  
Sujay Krishnamurthy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Vessel ◽  
Closed Form Solution ◽  
Creep Damage ◽  
Form Solution ◽  
Creep Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Good Agreement

This paper is Part 2 of two papers illustrating how isochronous stress strain curves can be used to calculate creep stresses and damage for pressure vessel components. Part 1 [1], illustrated the use of isochronous stress strain curves to obtain creep stresses and damages on two simple example problems which were solved using closed form solution. In Part 2, the isochronous method is implemented in finite element analysis to determine creep stresses and damages on pressure vessel components. Various different pressure vessel components are studied using this method and the results obtained using this method is compared time explicit Omega creep model. The results obtained from the isochronous method is found to be in good agreement with the time explicit Omega creep model.

Ratcheting due to Thermal Stratification

2019 ◽  
Author(s):  
R. Adibi-Asl ◽  
D. O’Kane ◽  
E. Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Temperature Distribution ◽  
Thermal Stratification ◽  
Fluid Flows ◽  
Uniform Temperature ◽  
Element Analysis ◽  
Steady State Condition ◽  
Thermal Ratcheting ◽  
The Finite Element Analysis

Abstract Thermal ratcheting is required to be checked by most of the piping design codes, specifically the ASME B&PV Code. For cases where the variation of temperature distribution is not uniform, the existing ratchet check methodology for piping is inadequate and therefore the finite element analysis (FEA) is often used to perform ratchet checks. Thermal stratification, in which cold and hot fluid flows are layered in a relatively steady state condition, is a good example of non-linear/non-uniform temperature distribution across the pipe. This paper develops straightforward equations to address thermal stratification in piping. Finite element analysis is used to benchmark the results.

Pure Bending of Curved Beams of Thin-Walled Rectangular Box Section

1991 ◽  
Vol 58 (1) ◽  
pp. 154-156 ◽  
Author(s):  
R. D. Cook
Keyword(s):  
Finite Element ◽  
Analytical Method ◽  
Circumferential Stress ◽  
Closed Form Solution ◽  
Form Solution ◽  
Finite Element Analyses ◽  
Curved Beams ◽  
Pure Bending ◽  
The Subject ◽  
Thin Walled

A closed-form solution of the subject problem is presented. The analytical method resembles that used by Bleich (1933) to study curved beams of I or T section. It is found that the circumferential stress may be smaller than a perpendicular stress that arises from flexing of parts of the box. Accuracy of the solution is verified by comparison with finite element analyses.

scholarly journals Finite Element Analysis of the Precracked Line Scratch Test

2000 ◽  
Vol 657 ◽  
Author(s):  
A.A. Volinsky ◽  
L. Mercado ◽  
V. Sarihan ◽  
W.W. Gerberich
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Crack Length ◽  
Closed Form Solution ◽  
Scratch Test ◽  
Form Solution ◽  
Interface Fracture ◽  
Mems Devices ◽  
Element Analysis ◽  
Thin Line

ABSTRACTIn MEMS packages and silicon devices, the adhesion of interconnects to the substrate is a critical reliability issue. A Precracked Line Scratch Test (PLST) is among one of the available tests to measure the thin line adhesion. In the test, an initial crack is introduced at the interface between the thin line and the substrate. The line is then loaded from the precracked end. The load is recorded continuously while the crack propagates before and after the line buckles. This precracked line scratch test has been applied earlier to tungsten thin lines on silicon wafers [1]. A macroscopic version of the test was also performed to evaluate the analytical model [2]. In the macroscopic tests, polycarbonate lines were bonded to steel substrates with cyanoacrylate.In this paper, finite element analysis is performed for the Precracked Line Scratch Test before line buckling. The energy release rates and phase angles are calculated based on the corresponding load and crack length. The results are then compared to the closed-form solution. Macroscopic experimental model along with the finite element solution has provided a way to derive the interface fracture toughness as a function of the crack length based on the load and crack length history. With the analysis in place, the precracked line scratch test can be used conveniently to study the adhesion of interconnects to passivation layers, MEMS devices and packages on different scales.

Material Property Identification of Artificial Degenerated Intervertebral Disc Models — Comparison of Inverse Poroelastic Finite Element Analysis with Biphasic Closed Form Solution

2013 ◽  
Vol 29 (4) ◽  
pp. 589-597 ◽  
Author(s):  
M. Nikkhoo ◽  
Y.-C. Hsu ◽  
M. Haghpanahi ◽  
M. Parnianpour ◽  
J.-L. Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Intervertebral Disc ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fe Analysis ◽  
Hydraulic Permeability ◽  
Element Analysis ◽  
Property Identification

ABSTRACTDisc rheological parameters regulate the mechanical and biological function of intervertebral disc. The knowledge of effects of degeneration on disc rheology can be beneficial for the design of new disc implants or therapy. We developed two material property identification protocols, i.e., inverse poroelas-tic finite element analysis, and biphasic closed form solution. These protocols were used to find the material properties of intact, moderate and severe degenerated porcine discs. Comparing these two computational protocols for intact and artificial degenerated discs showed they are valid in defining bi-phasic/poroelastic properties. We found that enzymatic agent disrupts the functional interactions of proteoglycans which decreased hydraulic permeability and aggregate modulus but increased the Poisson's ratio. The fatigue loading, which damages disc structure, and squeezes and occludes the matrix pores, further decreased the hydraulic permeability and the Poisson's ratio but increased the elastic modulus. The FE simulations showed the stress experienced during the creep test increases with severe degeneration but steady-state fluid loss decreases for the both moderate and severe degenerated discs. Discriminant analysis declared that the probability of correct classification using the FE analysis is higher than the results of the closed form solution. The specimen-specific models extracted from FE analysis can be additionally used for complimentary investigations on disc biomechanics.

Vibration of Thick Rectangular Plates of Bimodulus Composite Material

1981 ◽  
Vol 48 (2) ◽  
pp. 371-376 ◽  
Author(s):  
C. W. Bert ◽  
J. N. Reddy ◽  
W. C. Chao ◽  
V. S. Reddy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Thickness ◽  
Closed Form Solution ◽  
Form Solution ◽  
Fiber Direction ◽  
Rectangular Plates ◽  
Element Analysis ◽  
Arbitrary Boundary ◽  
Special Cases

A finite-element analysis is carried out for small-amplitude free vibration of laminated, anisotropic, rectangular plates having arbitrary boundary conditions, finite thickness shear moduli, rotatory inertia, and bimodulus action (different elastic properties depending upon whether the fiber-direction strain is tensile or compressive). The element has five degrees of freedom, three displacements and two slope functions, per node. An exact closed-form solution is also presented for the special case of freely supported single-layer orthotropic and two-layer, cross-ply plates. This solution provides a benchmark to evaluate the validity of the finite-element analysis. Both solutions are compared with numerical results existing in the literature for special cases (all for ordinary, not bimodulus, materials), and good agreement is obtained.

Analytical Method of Buried Steel Pipelines Subjected to Strike-Slip Faults

2017 ◽  
Author(s):  
Ying Li ◽  
Bin Wang ◽  
Xin Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Analytical Method ◽  
Analytical Methods ◽  
Pipe Steel ◽  
Nonlinear Finite Element Analysis ◽  
Strike Slip ◽  
Nonlinear Finite Element ◽  
Element Analysis ◽  
Analytical Methodology

Based on the summary of the existing analytical methods of buried steel pipelines at crossings with active strike-slip faults, an improved analytical methodology herein is proposed. Based on Karamitros model, the Ramberg-Osgood stress-strain relationships of pipe steel and the effects of nonlinear soil-pipeline interaction in both the axial and transverse directions are taken into account. Compared with existing analytical methodologies and 3D nonlinear finite element analysis, the analytical methodology presented is suitable for engineering applications due to exact and conservative results.

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