Effects of Stress on the Adhesion of Metals to Polyimides

1988 ◽  
Vol 130 ◽  
Author(s):  
K. Seshan ◽  
R. H. Lacombe ◽  
J. B. Wagner
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Mechanical Stress ◽  
Transition Zone ◽  
Gradual Transition ◽  
Adhesive Properties ◽  
Adhesive Interface ◽  
Pull Testing ◽  
Pi System ◽  
Discrete Layer

AbstractThis paper describes the effects of ambient, thermal and mechanical stress on the adhesion of titanium (Ti) to polyimide (PI). Pull testing on the Ti/PI system shows that metal/polyimide bonding degrades when the composite is thermally cycled. A thermochemical mechanism is proposed that accounts for the interface degradation. We do not treat the adhesive interface as a discrete layer, but rather as a gradual “transition zone” between metal and polymer -- a zone that may grow, and/or change in composition and stress state, thus altering the adhesive properties. The mechanism predicts discontinuities that may develop in the transition zone. Through the use of finite element techniques, it is demonstrated that when loads and displacements are imposed on the composite containing interface discontinuities, large localized stresses develop. Such stresses could explain the experimentally observed low strength failures.

scholarly journals Buckling of regular, chiral and hierarchical honeycombs under a general macroscopic stress state

2014 ◽  
Vol 470 (2167) ◽  
pp. 20130856 ◽  
Author(s):  
Babak Haghpanah ◽  
Jim Papadopoulos ◽  
Davood Mousanezhad ◽  
Hamid Nayeb-Hashemi ◽  
Ashkan Vaziri
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Closed Form ◽  
Plane Stress ◽  
Plane Stress State ◽  
Cellular Structures ◽  
Two Dimensional ◽  
Buckling Strength ◽  
Macroscopic Stress ◽  
Unit Cells

An approach to obtain analytical closed-form expressions for the macroscopic ‘buckling strength’ of various two-dimensional cellular structures is presented. The method is based on classical beam-column end-moment behaviour expressed in a matrix form. It is applied to sample honeycombs with square, triangular and hexagonal unit cells to determine their buckling strength under a general macroscopic in-plane stress state. The results were verified using finite-element Eigenvalue analysis.

Process-Oriented Stress Modeling and Stress Evolution During Cu/Low-K BEOL Processing

2004 ◽  
Vol 812 ◽  
Author(s):  
Charlie Jun Zhai ◽  
Paul R. Besser ◽  
Frank Feustel
Keyword(s):  
Stress State ◽  
Mechanical Stress ◽  
Plane Stress ◽  
Cmos Technology ◽  
Film Deposition ◽  
Stress Evolution ◽  
Process Step ◽  
Dual Damascene ◽  
Process Oriented ◽  
Low K

AbstractThe damascene fabrication method and the introduction of low-K dielectrics present a host of reliability challenges to Cu interconnects and fundamentally change the mechanical stress state of Cu lines. In order to capture the effect of individual process steps on the stress evolution in the BEoL (Back End of Line), a process-oriented finite element modeling (FEM) approach was developed. In this model, the complete stress history at any step of BEoL can be simulated as a dual damascene Cu structure is fabricated. The inputs to the model include the temperature profile during each process step and materials constants. The modeling results are verified in two ways: through wafer-curvature measurement during multiple film deposition processes and with X-Ray diffraction to measure the mechanical stress state of the Cu interconnect lines fabricated using 0.13um CMOS technology. The Cu line stress evolution is simulated during the process of multi-step processing for a dual damascene Cu/low-K structure. It is shown that the in-plane stress of Cu lines is nearly independent of subsequent processes, while the out-of-plane stress increases considerably with the subsequent process steps.

The gabbro–dyke transition zone demonstrated on Tviberg, Solund–Stavfjord Ophiolite Complex

1996 ◽  
Vol 133 (5) ◽  
pp. 573-582 ◽  
Author(s):  
K. P. Skjerlie ◽  
H. Furnes
Keyword(s):  
Transition Zone ◽  
Basaltic Magma ◽  
Source Region ◽  
Geochemical Evolution ◽  
Dyke Swarm ◽  
Gradual Transition ◽  
Ophiolite Complex ◽  
Plutonic Complex ◽  
Plutonic Rocks ◽  
High Level

AbstractThe transition zone between 100 % dykes and high-level plutonic rocks of the Solund-Stavfjord Ophiolite Complex is complex due to the existence of many lithologies with different and variable contact relationships. The rocks of the plutonic complex vary in composition from FeTi basaltic to quartz dioritic, and the grain sizes vary from fine to pegmatitic. Felsic varieties are produced by fractional crystallization of basaltic magma as demonstrated by geochemical evolution and by gradual transition from gabbro to quartz diorite. Patches of fractionated dioritic rocks may show both gradual and intrusive relationships with the surrounding host gabbro. This demonstrates that late-stage liquids commonly left the source region and locally intruded the surrounding parent rocks. The high-level plutonic rocks are thoroughly epidotized and are cut by dykes consisting of granoblastic epidote and quartz. The high-level plutonic complex is associated with irregular bodies of fine- to medium-grained plagioclase-porphyritic diabase of high MgO content. These diabase bodies are intruded by dykes that become progressively more regular in shape. The plutonic complex locally shows intrusive relationships with the overlying 100% dyke complex, but is itself cut by two dyke swarms. The dykes of the first swarm formed while the plutonic complex experienced sinistral shear strain, and the dykes are generally less regular and thinner than the dykes of the second swarm. This indicates that the dykes of the first swarm intruded while the rocks of the plutonic complex were still hot, while the next dyke swarm intruded later when the rock complex was colder. Dykes of both swarms range in composition from slightly to strongly fractionated, suggesting that the magma chambers they were expelled from underwent significant fractionation in between magma replenishment. Numerous dykes of both swarms carry large quantities of glomeroporphyritic aggregates of plagioclase and altered clinopyroxene, indicating that the source area to the dykes very often was a crystal mush.

BIDIMENSIONAL FINITE ELEMENT ANALYSIS OF SPUR GEAR: STUDY OF THE MESH STIFFNESS AND STRESS AT THE LEVEL OF THE TOOTH FOOT

2009 ◽  
Vol 33 (2) ◽  
pp. 175-187 ◽  
Author(s):  
Mohamed Nizar Bettaieb ◽  
Mohamed Maatar ◽  
Chafik Karra
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Spur Gear ◽  
Fortran Program ◽  
Mesh Stiffness ◽  
Element Analysis ◽  
Gear Mesh ◽  
Finite Element Software ◽  
Time Calculation ◽  
Finite Element Meshing

The purpose of this work is to determine the spur gear mesh stiffness and the stress state at the level of the tooth foot. This mesh stiffness is derived from the calculation of the normal tooth displacements: local displacement where the load is applied, tooth bending displacement and body displacement [15]. The contribution of this work consists in, basing on previous works, developing optimal finite elements model in time calculation and results precision. This model permits the calculation of time varying mesh stiffness and the evaluation of stress state at the tooth foot. For these reasons a specific Fortran program was developed. It permit firstly, to obtain the gear geometric parameters (base radii, outside diameter,…) and to generate the data base of the finite element meshing of a tooth or a gear. This program is interfaced with the COSMOS/M finite element software to predict the stress and strain state and calculate the mesh stiffness of a gear system. It is noted that the mesh stiffness is periodic and its period is equal to the mesh period.

A Finite Element for the Analysis of Shell Intersections

1996 ◽  
Vol 118 (4) ◽  
pp. 399-406 ◽  
Author(s):  
W. J. Koves ◽  
S. Nair
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Three Dimensional ◽  
Shell Element ◽  
Theory Of Elasticity ◽  
Shell Elements ◽  
Asme Code ◽  
Form Theory ◽  
Computation Scheme ◽  
Shell Intersections

A specialized shell-intersection finite element, which is compatible with adjoining shell elements, has been developed and has the capability of physically representing the complex three-dimensional geometry and stress state at shell intersections (Koves, 1993). The element geometry is a contoured shape that matches a wide variety of practical nozzle configurations used in ASME Code pressure vessel construction, and allows computational rigor. A closed-form theory of elasticity solution was used to compute the stress state and strain energy in the element. The concept of an energy-equivalent nodal displacement and force vector set was then developed to allow complete compatibility with adjoining shell elements and retain the analytical rigor within the element. This methodology provides a powerful and robust computation scheme that maintains the computational efficiency of shell element solutions. The shell-intersection element was then applied to the cylinder-sphere and cylinder-cylinder intersection problems.

Finite-element modelling of thermo-mechanical stress distribution in laser beam ceramic tile grout sealing process

2006 ◽  
Vol 220 (10) ◽  
pp. 1497-1508 ◽  
Author(s):  
A Liaqat ◽  
S Safdar ◽  
M A Sheikh
Keyword(s):  
Thermal Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Laser Beam ◽  
Mechanical Stress ◽  
Ceramic Tile ◽  
Element Model ◽  
Ceramic Tiles ◽  
Temperature Dependent ◽  
Heat Effects

Laser tile grout sealing is a special process in which voids between the adjoining ceramic tiles are sealed by a laser beam. This process has been developed by Lawrence and Li using a customized grout material and a high power diode laser (HPDL). The process has been optimally carried out at laser powers of 60–120 W and at scanning speeds of 3–15 mm/s. Modelling of the laser tile grout sealing process is a complex task as it involves a moving laser beam and five different materials: glazed enamel, grout material, ceramic tile, epoxy bedding, and ordinary Portland cement substrate. This article presents the finite element model (FEM) of the laser tile grout sealing process. The main aim of this model is to accurately predict the thermo-mechanical stress distribution induced by the HPDL beam in the process. For an accurate representation of the process, the laser was modelled as a moving heat source. A three-dimensional transient thermal analysis was carried out to determine the temperature distribution. Temperature-dependent material properties and latent heat effects, due to melting and solidification of the glazed enamel, were taken into account in the FEM, thereby allowing a more realistic and accurate thermal analysis. The results of the thermal analysis were used as an input for the stress analysis with temperature-dependent mechanical properties. The results obtained from the FEM are compared with the published experimental results.

Random Loads Fatigue: The Use of Spectral Methods Within Multibody Simulation

2005 ◽  
Author(s):  
Claudio Braccesi ◽  
Filippo Cianetti ◽  
Luca Landi
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Dynamic Simulation ◽  
Fatigue Damage ◽  
Spectral Methods ◽  
Mechanical Systems ◽  
Frequency Domain Method ◽  
Stress And Strain ◽  
Damage Evaluation ◽  
Multibody Dynamic

The evaluation of the fatigue damage performed by using the Power Spectral Density function (PSD) of stress and strain state is proving to be extremely accurate for a family of random processes characterized by the property of being stationary. The present work’s original contribution is the definition of a methodology which extracts stress and strain PSD matrices from components modelled using a modal approach (starting from a finite element modelling and analysis) within mechanical systems modelled using multibody dynamic simulation and subject to a generic random load (i.e. multiple-input, with partially correlated inputs). This capability extends the actual stress evaluation scenario (principally characterised by the use of finite element analysis approach) to the multibody dynamic simulation environment, more powerful and useful to simulate complex mechanical systems (i.e. railway, automotive, aircraft and aerospace systems). As regards the fatigue damage evaluation, a synthesis approach to evaluate an equivalent stress state expressed in terms of the PSD function of Preumont’s “equivalent von Mises stress (EVMS)”, starting from the complete stress state representation expressed in terms of PSD stress matrix and easily usable in the consolidated spectral methods, is proposed. This approach allows and has allowed the use of the above methods such as the Dirlik formula as a damage evaluation method. An additional result is the conception and implementation of a frequency domain method for the component’s most probable state of stress, allowing quickly identification of the most stressed and damageble locations. The described methodologies were developed and embedded into commercial simulation codes and verified by using as a test case a simple reference multibody model with a simple flexible component.

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