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Material Nonlinearities Papers (71 entries)
 
180 Series Elements: Why Should One Use Them in Linear Analysis
  (ANSYS, Inc.)
  Presentation on 18x elements (continuum, beam, shell) and its features related to both linear and nonlinear analyses.
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Average Rating: 9.2 (81 votes)  
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A Compilation of Anand Parameters for Selected SnPb and Pb-free Solder Alloys
  Zane Johnson (University of Minnesota)
  "Finite-element (FE) simulation is widely used in electronic packaging. It is particularly useful in the design of solder joint attachments. To ensure fidelity, FE simulation must capture the highly nonlinear behavior of solder. One useful material model for solder is Anand’s viscoplastic model. A compilation of Anand parameters reported in the literature for a variety of solder alloys is provided."
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Average Rating: 10.0 (6 votes)  
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A Finite Element Model For Pre- And Post-Test Calculations of the FOREVER-Experiments
  H. G. Willschuetz, E. Altstadt, F. P. Weiss, B. R. Sehgal
  "An axis-symmetric Finite Element (FE) model is developed based on the multi-purpose code ANSYS/Multiphysics. Using the Computational Fluid Dynamics (CFD) module the temperature field within the melt pool and within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a creep model which takes into account large temperature, stress and strain variations." (Document 2)
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Average Rating: 9.8 (54 votes)  
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A Mathematical Model for Fiber Reinforced Hyperelastic Material and Results with Finite Element Method
  Mustafa Resit Usal, Melek Usal, Ahmet Kabul
  "In this research, constitutive equation has been obtained that characterizes nonlinear mechanical behavior of fiber reinforced hyperelastic material, whose matrix material is isotropic."
ANSYS 5.5
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Average Rating: 9.4 (8 votes)  
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A Non-Linear Domain Decomposition Method
  Iakov Mordukhovich Klebanov, Andrei Nikolaevich Davydov
  "A new domain decomposition technique for parallelization of physically non-linear problems in solid mechanics is developed. It is extended for any stress-strain diagrams. The approach is based on the approximating generalized models of subdomains that leads to a considerably fewer number of iterations requiring updating of substructure parameters. The analytical proof of the convergence of the theoretical iterative procedure and the demonstration of convergence of its numerical implementation with the help of ANSYS are presented."
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Average Rating: 9.4 (54 votes)  
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Accumulated Creep Strain and Energy Density Based Thermal Fatigue Life Prediction Models for SnAgCu Solder Joints
  Ahmer Syed
  "This paper describes in detail the life prediction models for SnAgCu solder joints. The models are based on published constitutive equations for this alloy and thermal cycle fatigue data on actual components. The approach uses advance finite element modeling and analysis techniques and is based on mechanics of deformation. Both accumulated creep strain and creep strain energy density based models are developed. The model has been correlated with a number of data points and predicts life within 25% in most cases. The framework of modeling and prediction methodology described here is fully compatible with the framework used for SnPb solder previously."
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Average Rating: 10.0 (12 votes)  
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Advanced Tools for Design and Analyses of High Temperature Cyclic Loaded Turbine Components
  U. Gampe, I. Martynov, J. Keyser
  "The paper presents a new concept to predict viscoplastic deformations in components under thermal mechanical loading. This approach is based both on material data from uniaxial creep tests and additional laboratory component tests to consider the influence of multiaxiality. This concept was used for analysis of feature tests of flat tensile specimens with central hole. The maximum test temperature was 600 °C and the surface of the hole was attacked by cyclic thermal shocks." (This paper refers to use of ANSYS User-Defined Materials. A related paper is Laboratory Component Testing for Investigation of Material Degradation from Creep-Fatigue Interaction.)
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Average Rating: 9.1 (28 votes)  
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Analysis and Modeling of Fiber-Wrapped Columns and Concrete-Filled Tubes
  Mohsen Shahawy, Tom Beitelman, and Amir Mirmiran
  "Carbon-wrapping of concrete column adds to its strength and ductility. The behavior of carbon-wrapped concrete is in general very similar to that of glass-wrapped concrete. The bilinear confinement that was developed- for glass-wrapped concrete can be applied to carbon-wrapped concrete. However, a better fit can be obtained by re-calibrating the model for an entire database that consists of both carbon-wrapped and glass-wrapped concrete. Such database needs to be accompanied by a set of accurate coupon tests on the properties of the jacket. The finite element modeling is also useful in predicting the response of carbon-wrapped concrete. A more accurate estimate of jacket properties make the analysis fit the test results better."
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Average Rating: 7.7 (37 votes)  
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Analysis Of Gasketed Flanges With Ordinary Elements Using APDL Control
  Yasumasa Shoji, Satoshi Nagata
  "The analysis of gasketted flanges is now becoming an essential technique to design pressure vessels or piping, because the design code is being modified. On the other hand, the gasket has an extreme nonlinearity which causes the analysis to be very difficult, especially using linear material properties. A finite element analysis program other than ANSYS has the element library for gasket element, but ANSYS does not have it yet."

"The authors developed a method to model this nonlinear gasket by using the elements available in ANSYS Rel. 5.5 for 2-dimensional axisymmetric analysis and those in Rel. 5.6 for 3-dimensional analysis. In this paper, the concept and the procedure of the modeling is introduced. The data input is possible using a template, without using any other ANSYS commands. The whole analysis execution is controlled by APDL."

[STI: Gasket elements are available from version 6.1 onwards, after this paper was written]
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Average Rating: 7.9 (29 votes)  
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Analysis Of Reinforced Concrete Structures Using ANSYS Nonlinear Concrete Model
  Antonio F. Barbosa and Gabriel O. Ribeiro
  "This paper considers the practical application of nonlinear models in the analysis of reinforced concrete structures. The results of some analyses performed using the reinforced concrete model of the general purpose finite element code ANSYS are presented and discussed."
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Average Rating: 9.0 (178 votes)  
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Analysis Of The FOREVER-Experiments Using A Finite Element Model
  Eberhard Altstadt, Thomas Moessner, Baj Ral Sehgal, Hans-Georg Willschütz
  "An axis-symmetric Finite Element (FE) model is developed based on the multi-purpose code ANSYS/Multiphysics. Using the Computational Fluid Dynamics (CFD) module the temperature field within the melt pool and within the vessel wall is evaluated. The transient structural mechanical calculations are then performed applying a creep model which takes into account large temperature, stress and strain variations." (Document 1)
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Average Rating: 7.5 (10 votes)  
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Anisotropic Plasticity and Failure Prediction in Wood Composites
  David M. Moses, Helmut G.L. Prion
  "Two case studies are summarized using anisotropic plasticity and the Weibull weakest link failure model to predict the behavior of wood and wood composites. The linear elastic orthotropic model normally used for wood is shown to be insufficient for the prediction of ultimate strength in wood. Non-linear, non-recoverable behavior in compression in each of the orthogonal material directions is of particular interest in cases where localized crushing governs the load-displacement behavior of wood."

"The anisotropic plasticity option in ANSYS was used to predict yielding and post-yield behavior for the wood composite used in this study because yield stresses in orthogonal directions were found to be in the ratio of 1:1.2:5. A user-programmable Fortran subroutine was developed for ANSYS to carry out the failure analysis (and to calculate the volume integration of the stresses) at each load-step in post-processing. The model was verified using two cases: I) the ASTM D143 shear block test, and II) bolted connections."
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Average Rating: 9.2 (32 votes)  
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ANSYS Cast Iron Material Model Matches Experimental Data
  (ANSYS, Inc.)
  "[The purpose of this paper is to] verify the accuracy of the ANSYS cast iron material model. Results from ANSYS are compared with experimental data for a biaxially loaded cruciform geometry."
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Average Rating: 9.5 (11 votes)  
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ANSYS Material Modeling: Hyperelastic Material Characterization
  (ANSYS, Inc.)
  Overview of the hyperelastic curve-fitting capabilities introduced in ANSYS 7.0.
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Average Rating: 10.0 (8 votes)  
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ANSYS Mechanical - A Powerful Nonlinear Simulation Tool
  Grama Bhashyam (ANSYS, Inc.)
  A whitepaper describing various ANSYS features in the area of nonlinear mechanics, including element formulation, constitutive models, and contact technology.
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Average Rating: 9.6 (14 votes)  
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Application of the Finite Element Method In Cold Forging Processes
  Cristina Maria Oliveira Lima Roque, Sérgio Tonini Button
  "In this study, the application of a commercial general finite element software - ANSYS - has been applied to model a forming operation. Models have been developed to simulate the ring compression test and to simulate a basic forming operation (upsetting) that is applied in most of the cold forging parts sequences." (Plasticity, contact, finite strain)
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Average Rating: 10.0 (16 votes)  
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Applying Anand Model to Represent the Viscoplastic Deformation Behavior of Solder Alloys
  G. Z. Wang, Z. N. Cheng, K. Becker, J. Wilde
  "A unified viscoplastic constitutive law, the Anand model, was applied to represent the inelastic deformation behavior for solders used in electronic packaging. The material parameters of the constitutive relations for 62Sn36Pb2Ag, 60Sn40Pb, 96.5Sn3.5Ag, and 97.5Pb2.5Sn solders were determined from separated constitutive relations and experimental results. The achieved unified Anand model for solders were tested for constant strain rate testing, steady-state plastic flow and stress/strain responses under cyclic loading. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress/strain responses of solder joints in service."
[ANSYS Nonlinear, version unknown]
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Average Rating: 10.0 (3 votes)  
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ASME Code and Ratcheting in Piping Components
  Tasnim Hassan and Vernon C. Matzen
  "The main objective of this research is to develop an analysis program which can accurately simulate ratcheting in piping components subjected to seismic or other cyclic loads. Ratcheting is defined as the accumulation of deformation in structures and materials with cycles. This phenomenon has been demonstrated to cause failure to piping components (known as ratchetingfatigue failure) and is yet to be understood clearly. The design and analysis methods in the ASME Boiler and Pressure Vessel Code for ratcheting of piping components are not well accepted by the practicing engineering community."
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Average Rating: 8.3 (3 votes)  
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Benchmark Tests on ANSYS Parallel Processing Technology
  Kentaro Suzuki
  "ANSYS Inc. has released parallel processing solvers, DDS (Distributed Domain Solver) and AMG (Algebraic Multigrid Solver) in ANSYS version 5.7 in order to meet the requirements from the market."

"In this paper, simple tests are first carried out to confirm the features and capabilities of DDS and AMG for different types of analyses. Furthermore, real-life problems such as thermal stress of an engine block (7.3 million DOF) and elastic-plastic-creep behavior of an IC packaging (about 84,000 DOF) are analyzed. The effectiveness of ANSYS parallel processing solvers is also studied."
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Average Rating: 5.0 (6 votes)  
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Cast Iron Plasticity
  (ANSYS, Inc.)
  Presentation on Cast Iron plasticity model introduced in ANSYS 6.1 (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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Average Rating: 9.4 (8 votes)  
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Compressive Strength of Solid Clay Brick Masonry under Eccentric Loading
  A. Brencich, C. Corradi, L. Gambarotta, G. Mantegazza, E. Sterpi
  "Arches, vaults and pillars generally experience eccentric normal force. As a consequence, the classical theories of masonry collapse, developed for concentrically compressed brickwork, are not directly applicable. In this paper experimental data on solid clay brick and lime-mortar masonry prisms, eccentrically loaded, are presented. Comparing the results to the response of a FEM model, some hints on the collapse mechanism of masonry show that the edge effects greatly affect the load carrying capacity of the brickwork. Besides, the plane section assumption is found to be acceptable up to the ultimate compressive strength, allowing relatively simple models to be used for arch-type structures." (Concrete SOLID65)
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Average Rating: 9.8 (26 votes)  
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Contact Analysis of Workpiece-Fixture System Under Time-Varying Machining Loads Using Finite Element Method
  N. Kaya, F. Öztürk
  "Proper fixture design is crucial to product quality in terms of precision, accuracy and finish of the machined part. Fixturing systems must be capable of positioning, holding and supporting the workpiece throughout the machining process. In this paper, modular fixture design verification analysis is carried out for time-varying machining forces using nonlinear finite element analysis. Chip removal effect is taken into account using element death technique and the frictional contact between workpiece and fixture elements is also considered. This paper also adresses applying optimal clamping forces in order to minimize the deformation. A case study is presented to demonstrate the suggested methodology."
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Average Rating: 10.0 (10 votes)  
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Creep Resistance and Creep Bending Resistance of Light Metal Matrix Composites for Research in Airframe Structural Effiency
  E. Neubauer and H.Peter Degischer
  "Main aim of the research in the frame of the AMTT programme was the testing of a fiber reinforced Al-alloy. For investigation of the creep behaviour of this material, creep tests under bending were performed. The tested material was Al99.85+0.1%Mg reinforced with Al2O3 fibers (Altex/Sumitomo), which was prepared by means of gas pressure infiltration. Main benefit of such a material for application would be the lowering of the weight of the material without a loss of properties." (see Appendix A for ANSYS use in this document)
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Average Rating: 9.5 (10 votes)  
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Dynamic FEA and Simulation for A Series of Blast-Resist-door
  Lu Xinzheng and Jiang Jianjing
  "A series of blast-resist-door were used widely. In order to know the behavior of the doors under blast load and verify the safety of the doors, dynamic finite element analysis and simulation are carried out with advanced FEA software, ANSYS/LS-DYNA and SAP. Contact surfaces are introduced to simulate the relation between the door leaf and doorframe, as well as the relation between the door hinges and bearings. Altogether 24 different load cases are analyzed to simulate various load conditions."
[ANSYS LS-DYNA, version unspecified]
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Average Rating: 9.2 (6 votes)  
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Dynamic Pile Testing and Finite Element Calculations for the Bearing Capacity of a Quay Wall Foundation
  F. Kirsch, B. Plaßmann, T. Huch, W. Rodatz
  "In April 1999 the construction of a new quay wall in the port of Hamburg started. In a first stage two new berths with an overall length of 1400 m will be built. In order to proof the bearing capacity of the foundation dynamic pile testing is performed to a great extent. To date more than thirty different piles were tested by the Institute for Foundation Engineering and Soil Mechanics of the Technical University of Braunschweig. In order to check for possible set-up effects redriven tests were performed. For comparison reasons static load tests were also carried out, one of which was done with an instrumented pile to allow skin friction and end bearing to be evaluated separately. The CAPWAP results proofed to be very helpful especially in those cases where the testing situation differed from the later service condition. Special questions called for detailed finite element analysis of the load-settlement behaviour of single piles in certain construction stages."
Although ANSYS is not explicitly mentioned, F. Kirsch also used ANSYS in two related papers, Stability of the vault developing over Soilcrete bodies and Ground Improvement and Its Numerical Analysis.
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Average Rating: 9.3 (7 votes)  
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Dynamic Shock Simulation Of A Computer Hard Drive Using an ANSYS/LS-DYNA Implicit-Explicit Sequential Solution
  Chris Andersen, John Stricklin
  "This paper describes a nonlinear transient dynamic analysis of a computer hard drive using ANSYS in combination with ANSYS/LS-DYNA. The model includes the enclosure, platters, spindle, read/write heads, and other key components. The objective of the analysis was to determine the interaction between the parts in this assembly, such as lift off and impact between the read/write heads and platters, when the hard drive is subjected to a 250 G half sinusoid shock load. This load simulates a shock test, which the manufacturer does to qualify hard drives." From 2000 Conference
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Average Rating: 9.2 (40 votes)  
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Effect of Package Design and Layout on BGA Solder Joint Reliability of an Organic C4 Package
  Biju Chandran, Deepak Goyal, and Jeffrey Thomas
  "Ball Grid Array (BGA) is currently the interconnect of choice for attaching microprocessors on a printed circuit board (PCB). The reliability of solder joints is one of the critical issues in BGA surface mount technology (SMT). During reliability testing, BGA fatigue failures were observed on test vehicles (TV). Finite element analysis and physical failure analysis were used to determine the risk to the product in the field. As part of this effort, parametric finite element analysis was carried out to determine the effect of design features like the package size, and BGA pattern on the propensity of fatigue failure. The results of the finite element analysis and physical failure analysis showed that the risk to fatigue failure was much greater on a peripheral / partial grid array package than in a full grid array package."
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Average Rating: 10.0 (3 votes)  
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Effect of Simulation Methodology on Solder Joint Crack Growth Correlation
  Robert Darveaux
  "A generalized solder joint fatigue life model for surface mount packages was previously published in Refs [1,2]. The model is based on correlation to measured crack growth data on BGA joints during thermal cycling. It was subsequently discovered by Anderson et.al. that the ANSYS TM 5.2 finite element code used in the model had an error in its method for calculating plastic work [3]. It was shown that significant error in life prediction could result by using a recent version of the code where the bug has been fixed. The error comes about since the original crack growth constants were derived based on plastic work calculations that had the bug.
In this paper, crack initiation and growth constants are re-calculated using ANSYS 5.6. In addition, several other model related issues are explored with respect to the crack growth correlations. For example, 3D slice models were compared to quarter symmetry models. Anand’s constitutive model was compared with Darveaux’s constitutive model. It was shown that the crack growth rate dependence on strain energy density always had an exponent of 1.10 +/- 0.15. This is in the range of the original correlation, so the accuracy of relative predictions should still be within +/- 25%. However, the accuracy of absolute predictions could be off by a factor of 7 in the worst case, if the analyst uses a modeling procedure that is not consistent with that used for the crack growth correlation. The key to good accuracy is to maintain consistency in the modeling procedure."

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Average Rating: 10.0 (6 votes)  
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Effects of Nonlinear Geometric and Material Properties on the Seismic Response of Fluid/Tank Systems
  He Liu, Daniel H. Schubert
  "To explore the effects large deformation and nonlinear material properties have on the seismic response of fluid/tank systems, the computer program ANSYS was selected to develop a Finite Element Analysis (FEA) model of a ground level, cylindrical steel shell and roof tank structure with contained fluid under seismic load. The ANSYS program was selected for its ability to include shell and structural steel elements, contained fluid elements, fluid-structure interactions, material and geometric nonlinearities, and contact type elements. For purposes of this study, analysis results from a linear elastic, small deformation fixed base model are compared with an elasto-plastic material property model with large deformation assumptions. Results show the significant difference in results based on the assumptions used and indicate that current design code based values may not be conservative in resultant loading calculations."
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Average Rating: 10.0 (34 votes)  
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Finite Element Analysis for Solder Ball Connect (SBC) Structural Design Optimization
  J.S. Corbin
  "Solder Ball Connect (SBC) is a second-level surface mount electronics packaging technology in which ceramic modules containing one or more chips are joined to a circuit card (FR-4) by means of an array of nonhomogeneous solder columns. These columns consist of a high-temperature-melting 90%Pb/lO%Sn solder sphere attached to the module and card with eutectic solder fillets. The solder structures accommodate the bulk of the strain (which is due to the thermal- expansion mismatch between FR-4 and the 9211 ceramic of the modules) generated during power cycling. If the solder structures are not properly designed, the thermal strain can be a source of premature fatigue failure. In this work, finite element analysis is used to characterize the plastic strains that develop in the SBC interconnection during thermal cycling. Since plastic strain is a dominant parameter that influences low-cycle fatigue, it is used as a basis of comparison for various structural alternatives. Designed experiment techniques are used to systematically evaluate the thermal strain sensitivity to structural variables. Results are used to identify an optimally reliable structure that is robust in terms of assembly-process variables."
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Average Rating: 10.0 (4 votes)  
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Finite Element Analysis Of Crowning Sealing Caps
  Henri Champliaud, L Van Ngan
  "Metal closures, with an integrated gasket, are widely used in the food industry to ensure the sealing of the glass bottles by setting. The success of this bottle-capping is due to the relevant choice of the variables in the manufacturing process. Actually, the effects of the various variables of the process are not precisely understood."

"In this paper, the leakage pressure of an assembly, with given parameters of a standard setting operation is predicted. The study is concentrated firstly on the simulation of setting the cap on the bottle, and secondly, on the global distribution of the efforts of contact on the gasket according to the internal pressure. Finally, the leakage pressure of the assembly is determined using practical tests that relate the leakage pressure with the global force exerted on the gasket."
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Average Rating: 7.1 (7 votes)  
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Finite Element Analysis Of Plasticity-Induced Crack Closure For Inclined Cracks
  L. W. Wei and M. N. James
  "The contact occurring in inclined cracks is a general contact problem, and thus a general contact analysis must be implemented in which a combined load and displacement control procedure is used. The commercial FE code ANSYS 5.4 used in this work provides the utilities to deal with general contact problems."
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Average Rating: 10.0 (11 votes)  
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Finite Element Based Solder Joint Fatigue Life Predictions for a Same Die Stacked Chip Scale Ball Grid Array Package
  Bret Zahn
  "Viscoplastic finite-element simulation methodologies were utilized to predict solder joint reliability for a same die size, stacked, chip scale, ball grid array package under accelerated temperature cycling conditions (-40C to +125C, 15min ramps/15min dwells). The effects of multiple die attach material configurations were investigated along with the thickness of the mold cap and spacer die. The solder structures accommodate the bulk of the plastic strain that is generated during accelerated temperature cycling due to the thermal expansion mismatch between the various materials that encompass the stacked die package. Since plastic strain is a dominant parameter that influences low-cycle fatigue, it was used as a basis for evaluation of solder joint structural integrity. The paper discusses the analysis methodologies as implemented in the ANSYS finite element simulation software tool and the corresponding results for the solder joint fatigue life. Some ANSYS parametric design language commands are included for the benefit of those readers who are familiar with the tool."
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Average Rating: 9.7 (15 votes)  
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Finite Element Modeling Of Damage Accumulation In Bolted Composite Joints Under Incremental Tensile Loading
  Th. Kermanidis, G. Labeas, K.I. Tserpes and Sp. Pantelakis
  "A three-dimensional progressive damage model was developed in order to simulate the damage accumulation of bolted single-lap composite joints under in-plane tensile loading. The parametric study includes stress analysis, failure analysis and material property degradation. Stress analysis of the three-dimensional geometry was performed using the ANSYS FE code. Failure analysis and degradation of material properties were implemented using a progressive damage model, which is incorporated in an ANSYS macro-routine."
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Average Rating: 8.3 (21 votes)  
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Finite Element Modeling of Elastic Modulus in Ductile Irons: Effect of Graphite Morphology
  S.H. Pundale, R.J. Rogers, G.R. Nadkarni
  "This investigation is the first to deal with the modeling and prediction of effective elastic modulus of ductile irons using finite elements. Both plane stress and axisymmetric formulations were used to predict elastic moduli. With finite elements, it is possible to include microstructural parameters that are extremely difficult or impossible to model analytically. Assuming that the graphite nodules act as voids, the effective elastic modulus was modeled by considering the effect of small strains for nodule variables of volume fraction, shape, size and distribution. (No matrix variables have been considered.)"
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Average Rating: 6.2 (4 votes)  
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Finite Element Modeling of Human Artery Tissue with a Nonlinear Multi-Mechanism Inelastic Material
  Sergey Sidorov
  "In this dissertation, a nonlinear multi-mechanism inelastic material model is formulated for modeling vascular tissue, collagen recruitment and elastin degradation. The model is implemented into the commercial finite element software package ANSYS with user programmable features."
ANSYS 10.0, USERMAT
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Finite Element Predictions of Plasticity-Induced Fatigue Crack Closure in Three-Dimensional Cracked Geometries
  Jeffrey Skinner, Jr.
  "Elastic-plastic finite element analyses were performed to predict the crack opening level profiles in semi-elliptical surface cracks."
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Average Rating: 8.6 (21 votes)  
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Gasket Materials
  (ANSYS, Inc.)
  Presentation on the gasket materials and companion interface elements, introduced at ANSYS 6.1 (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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Average Rating: 10.0 (2 votes)  
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HDPUG's Design for Lead-Free Solder Joint Reliability of High-Density Packages
  J. Lau, W. Dauksher, J. Smetana, R. Horsley, D. Shangguan, T. Castello, I. Menis, D. Love, B. Sulliv
  "The lead-free solder-joint reliability of the high-density packages, 256-pin PBGA (plastic ball grid array), 388-pin PBGA, and 1657-pin CCGA (ceramic column grid array), on PCB (printed circuit board) subjected to temperature cycling is investigated. Emphasis is placed on the determination of the creep responses (e.g., stress, strain, and strain energy density) of the lead-free solder joints of these packages. The lead-free solder is assumed to obey the Garofalo-Arrhenius creep constitutive law. The results presented herein should be useful for a better understanding of the thermal-mechanical behaviors of the lead-free solder joints in these high-density package assemblies."
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Average Rating: 8.3 (3 votes)  
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Hyper-Elastic Contact Analysis of a Push-Button Diaphragm Seal
  Jeffrey R. Annis
  "Presented is the non-linear finite element analysis of a rubber diaphragm seal utilizied in a pushbutton design. Analysis considerations encompassed, nonlinear hyper-elastic material behavior of the rubber, large deflection analysis of seal complex motion, and contact analysis with mating parts. Design parameters of primary interest were, seal deflection patterns and seal actuation force as a function of travel."
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Average Rating: 10.0 (14 votes)  
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Hyperelasticity
  (ANSYS, Inc.)
  Presentation on the various hyperelastic strain energy functions available in ANSYS (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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Average Rating: 9.0 (5 votes)  
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Implicit Creep
  (ANSYS, Inc.)
  Presentation on implicit creep (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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Average Rating: 10.0 (11 votes)  
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Methods for Modeling Bolts in the Bolted Joint
  Jerome Montgomery
  "Modeling bolts for three-dimensional finite element applications have, and still continue to raise questions. The limitations on model size sometimes make modeling of solid bolts impractical. Therefore, many analysts choose other methods to model bolts. Line elements with coupled nodes and line elements with spider beams are a couple of alternative approaches. This paper looks at a few methods for modeling pretension bolted joints using the finite element method (ANSYS 5.7). Pretension is modeled using ANSYS pretension elements (PRETS179) which can be used on solid or line element types. Surface-to-surface contact elements are used to account for varying contact distribution along flanges. Bolt head and nut behavior is modeled by, coupled nodes, beam elements, rigid body elements (RBE3), or solids. Bolt stud is modeled by solid elements, beam elements, pipe elements, or link elements. The choice of line elements versus solid elements is determined by the degree of complexity sought. The pros and cons of different simulations are also discussed."
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Average Rating: 9.3 (54 votes)  
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Modeling Diesel Engine Cylinder Head Gaskets using the Gasket Material Option of the SOLID185 Element
  Jonathan Raub
  "The modeling of diesel engine cylinder head gasket joints is complicated by the nonlinear response of the head gasket’s materials. Linearization of these material responses can lead to significant errors in the solution’s results. The 1-dimensional nonlinear approximation made by the Gasket material option of the SOLID185 element sufficiently captures the response of the nonlinear gasket materials while maintaining practical solution times for the large model sizes associated with multi-cylinder head gasket joint models. This paper will give an overview of the model building and assembly process used to create a head gasket joint model, describe the nonlinear nature of the materials used in the model, and present comparisons of the model’s results with experimental measurements."

[STI: There is a gasket-specific material & element in 6.1, not available at the time of the writing]
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Average Rating: 9.2 (26 votes)  
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Non-linear Finite Element Modeling of the Titanium Briquettes Hot Extrusion Process
  Alexey I. Borovkov, Denis V. Shevchenko
  "In this paper the mathematical model is developed to perform mathematical simulation of the hot extrusion process. The model makes it possible to observe the influence of various system parameters on the extrusion process. All researches were carried out with the use of the ANSYS 5.6 RFS FE-software system. During the research the modeling and analysis of various events that can be observed (material dead zone appearing, capsule crimping, capsule damage etc.) was successfully carried out. The mathematical model was created on the basis of contact thermo-mechanics relations with physical and geometrical non-linearities."
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Average Rating: 10.0 (11 votes)  
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Non-Linear Problems Of Steel Civil Engineering Structures
  Milan Vasek
  "The civil engineering structures are today designed with respect to the limit state of serviceability and limit states of the strength and stability. The design of more efficient and light structures leads to the nonlinear analysis of deflections and stresses. Some parts of structure could reach the yield point under the design load. Some parts of structure could lose their local stability. These complex problems of a different nature are possible to solve by FEM methods."
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Average Rating: 8.0 (37 votes)  
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Nonlinear Contact Analysis Techniques Using ANSYS
  (ANSYS, Inc.)
  Presentation on various aspects of 17x contact technology (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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Nonlinear Models of Reinforced and Post-tensioned Concrete Beams
  P. Fanning
  "Commercial finite element software generally includes dedicated numerical models for the nonlinear response of concrete under loading. These models usually include a smeared crack analogy to account for the relatively poor tensile strength of concrete, a plasticity algorithm to facilitate concrete crushing in compression regions and a method of specifying the amount, the distribution and the orientation of any internal reinforcement. The numerical model adopted by ANSYS is discussed in this paper. Appropriate numerical modelling strategies are recommended and comparisons with experimental load-deflection responses are discussed for ordinary reinforced concrete beams and post-tensioned concrete T-beams." (Concrete SOLID65)
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Average Rating: 9.6 (23 votes)  
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Nonlinear Stress Analysis and Optimization of a Welded Plate Steel Pro/ENGINEER Assembly
  Andrew J. Bax, Chris Andersen, Shane Vander Kooi
  From 1996 Conference
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Numerical Analysis of Plastic Encapsulated Electronic Package Reliability: Viscoelastic Properties of Underfill Resin
  Man-Lung Sham, Jang-Kyo Kim, Joo-Hyuk Park
  "The reliability and mechanical performance of electronic integrated circuit (IC) package is studied based on the finite element analysis."
ANSYS Nonlinear, version 5.7.
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Optimization in high-precision glass forming
  M. Sellier
  "The question of interest in the present study is the inverse problem for high precision glass forming, i.e. "How to design the mould and the temperature regime so that at the very end of the forming process we will get at room temperature a prescribed glass geometry with a precision in the order of the Micron?" The aim is to eliminate from the manufacturing process the costly and time-consuming postprocessing when the final shape does not conform precisely to the desired one."
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Optimizing Board-level Reliability of an Underfilled, Stacked Chip Scale Package
  Zane E. Johnson, Nathan R. Schneck
  "Previously benchmarked finite-element (FE) models of a stacked chip scale package (CSP) are used to identify optimum underfill material properties under drop-impact and accelerated temperature cycling (ATC) stress conditions. The simulation sets indicate that an underfill having a modulus of 2–6 GPa and CTE of 25 ppm/K maximizes drop life and does no harm to ATC performance for both Sn63Pb37 and SAC305 solder joints. The methodology described can be applied to other package styles, material sets, and stress conditions."
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Optimum Design of a Ceramic Tensile Creep Specimen Using a Finite Element Method
  Z. Wang, C. K. Chiang, and T. J. Chuang
  "An optimization procedure for designing a ceramic tensile creep specimen to minimize stress concentration is carried out using a finite element method." (Optimization, Creep, Contact)
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Parameter Studies For Enhanced Integrity Of Reciprocating Compressor Foundation Blocks
  Jayant S. Mandke, Anthony J. Smalley
  "The model development and analyses of reinforced concrete block used the ANSYS finite element program."
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Average Rating: 9.7 (34 votes)  
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Plastic Deformation and Loss of Joint Force by Creep in High Current Joints
  Josef Kindersberger, Helmut Löbl, Stephan Schoft
  "The mechanical stress distribution in aluminum busbar joints is calculated using the Finite Element Method. Based on the physical fundamentals of creep in aluminum the reduction of the joint force by creep depending on the temperature of the joints as well as on the initial joint force and on the washer is simulated." (Creep)
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Principles of Simulating Contact Between Parts using ANSYS
  David H. Johnson
  "The ANSYS finite element analysis (FEA) program offers a variety of elements designed to treat cases of changing mechanical contact between the parts of an assembly or between different faces of a single part. These elements range from simple, limited idealizations to complex and sophisticated, general purpose algorithms. FEA analysts are frequently faced with modeling situations where changing contact cannot be assumed negligible and ignored. Finding the best choices for contact elements, element options, solver, and solution options can drastically improve the model’s performance and reduce the analyst’s frustration with a contact simulation model."
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Average Rating: 9.3 (14 votes)  
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Ratcheting Simulations with Modified Abdelkarim-Ohno Cyclic Plasticity Model
  Radim Halama
  "In a search for a constitutive model for ratcheting simulations in rolling contact fatigue domain, the models by Chaboche and AbdelKarim-Ohno and the modificiation of AbdelKarim-Ohno model have been evaluated against a set of uniaxial and biaxial ratcheting responses of steel CS1026. It is difficult to simulate simultanously the uniaxial and multiaxial ratcheting responses with the AbdelKarim-Ohno model. This problem has been removed by modification described in the paper. The proposed model was implemented into the FE code Ansys using Fortran user‘s subroutine. The proposed cyclic plasticity model simulates all solved cases very well."
[ANSYS nonlinear, version 8.0]
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Simulation of Brake Block Induced Corrugation on Railway Wheels
  Ulf Sellgren
  "Railway wheels that are equipped with cast-iron brake blocks generate significantly more rolling noise than wheels with other types of braking devices or block materials. The roughness of the treads on cast-iron block-braked wheels has typically a peak at a wavelength around 6 cm. The complex interaction between quasi-static and dynamic mechanical behavior and thermal, chemical, and metallurgical effects in the block-wheel contact combined with the rolling and sliding situation in the wheel-rail contact has made it difficult to get an understanding of the causes from field measurements. Coupled transient thermal and quasi-static mechanical FE simulations with ANSYS show that thermoelastic instability (TEI) may be a major cause for the roughness initiation."
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Average Rating: 8.8 (8 votes)  
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Space-Time Finite Element Approximation and Numerical Solution of Hereditary Linear Viscoelasticity Problems
  J. Orlik, A. Ostrovska
  "In this paper we suggest a fast numerical approach to treat problems of the hereditary linear viscoelasticity, which results in the system of elliptic partial differential equations in space variables , who’s coefficients are Volterra integral operators of the second kind in time. We propose to approximate the relaxation kernels by the product of purely time- and space-dependent terms, which is achieved by their piecewisepolynomial space-interpolation. A priori error estimate was obtained and it was shown, that such approximation does not decrease the convergence order, when an interpolation polynomial is chosen of the same order as the shape functions for the spatial finite element approximation, while the computational effort is significantly reduced."
[ANSYS Nonlinear, version unknown]
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Super Elastic Alloy Eyeglass Frame Design Using the ANSYS Workbench Environment
  Peter R. Barrett and Patrick Cunningham (CAEAI)
  "Up front analysis at the concept stages of developing a device most often result in reduced time to market and a better more efficient product development cycle. Design Modeler (1) / DesignXplorer (2) and ANSYS Structural’s super-elastic material model (3) are used in this demonstration of a design process for an eyeglass frame. This example provides an illustration of using the parametric functionality of the ANSYS Workbench environment for a highly nonlinear application. The Workbench environment can be used to perform design iterations in conjunction with material laws only available in the standard ANSYS environment. A shape memory superelastic material law was formally included in ANSYS 8.0. The material law captures the super-elastic behavior of Nitinol (4) along with its unique hysteretic response under cyclic loading. In the demonstration, the eyeglass frame is subjected to crushing and cyclic loading events. Geometric design variables are varied in an attempt to increase the frame stiffness yet keep the peak strain levels in the frame below 10% strain, which is a typical elastic limit for Nitinol. The cyclic behavior of the material is also monitored under the design load to evaluate the potential of fatigue failure. The procedure demonstrates the ease in interfacing the suite of Workbench products with geometric, material and contact nonlinear analysis problems."

Presentation file also available here
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The Building Blocks of Simulation: A New Family of Elements for Stress Analysis
  (ANSYS, Inc.)
  Presentation on 18x family of elements (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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The Comparison of Biomechanical Breast Models: Initial Results
  C. Tanner, J.A. Schnabel, A. Castellano Smith, L.I. Sonoda, D.L.G. Hill, D.J. Hawkes, A. Degenhard,
  "We present initial results from evaluating the accuracy with which biomechanical breast models based on finite element methods can predict the displacements of tissue within the breast. We investigate the influence of different tissue elasticity values, Poisson’s ratios, boundary conditions, finite element solvers and mesh resolutions on one data set. MR images were acquired before and after compressing a volunteer’s breast gently. These images were aligned using a 3D non-rigid registration algorithm. The boundary conditions (surface displacements) were derived from the result of the non-rigid registration or by assuming no patient motion at the posterior or medial side. Three linear and two non-linear elastic material models were tested."
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The Numerical Analysis of Strain Behavior at the Solder Joint and Interface in a Flip Chip Package
  S.C. Chen, Y.C. Lin, C.H. Cheng
  "The aim of this study was to investigate the strain behaviors at the joint interface of a flip chip package during thermal cycling testing using a numerical method. Because the underfill and solder bump material properties exhibit a large non-linearity in the higher temperature range, the linear elastic assumption may lose accuracy during numerical analysis. This study compared the differences in interfacial stress or strain between the linear and non-linear material property assumptions. The viscoplasticity of the solder bump and temperature-dependent underfill properties were assumed in the non-linear analysis. The numerical results showed that the solder bump failure mechanism was a combination of fatigue and creep actions dominated by plastic shear strain. The tensile stress due to shrinkage and hardening in the solder joints in the low thermal cycle temperature dwell period could result in ablation at the joint interface."
ANSYS 5.6.1, Anand model
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Three-Dimensional Modeling Of A Bolted Connection
  David Johnson, Richard Englund, Brian McAnlis, Kevin Sari, and David Colombet
  "Two-dimensional, axisymmetric models are used to study the interaction and stresses developed in the threads of a bolted connection. One problematic issue with this approach is that the 2D model simulates the threads as separate rings of material, not as the actual continuous helix. Therefore, two-dimensional modeling cannot simulate the conditions of joint tightening and sliding along the helical thread flanks when the nut is turned. In addition, the analyst must justify the 2D axisymmetric assumption as appropriate to this truly three-dimensional system. This paper presents the modeling technique used to create a "mostly-brick" meshed 3D model of a nut and bolt joint."
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Average Rating: 9.6 (28 votes)  
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Towards Automated Determination of USERMAT for the Nonlinear Constitutive Behavior of Composites
  J. Michopoulos, P. Mast, R. Badaliance, L. Gause, T. Chwastyk, R. Foerch
  "Recent advances in finite element techniques and design optimization integration technologies along with the parallel hardware and software evolution have directed the CMS group to turn its attention to utilizing "of the shelf" technology of achieving the same goals. Thus, the "Z-mat" and "Z-Optim" packages from Northwest Numerics, Inc., have been utilized to extract the non-linear constitutive response from the available experimental data in an integrated and automated manner and in conjunction with the ANSYS/Mechanical infrastructure. The automation lies on the fact that the process automatically generates the code of a "USERMAT" subroutine that it can be subsequently used with any geometry and loading specification definable within the limits of ANSYS' non-linear element library. The geometry of the single notched specimen of NRL's In Plane has been used for developing and verifying the process."
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Average Rating: 7.5 (8 votes)  
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Transient Behavior of a Polymer Fill Material with Time Dependent Viscoelastic Properties
  John Thompson, Steven Groothuis, Hong Tang, Paul Koeneman
  "In an effort to simplify the implementation of viscoelastic material models into ANSYS, an ANSYS User-Programmable Feature (UsrFictive) has been modified to allow a more practical definition of viscoelastic material parameters. Standard ANSYS input of material data may be based upon temperature. Currently, ANSYS material data may not be a function of any other parameter. Many polymers used in industry are initially liquid and must be “cured” in a manufacturing process. This fact means that the properties will change over time. This application demonstrates one method of implementing a curing process simulation for a viscoelastic polymer."
[ANSYS Nonlinear, version 6.?]
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Uniaxial and biaxial ratchetting in piping materials - experiments and analysis
  S.C. Kulkarni, Y.M. Desai, T. Kanta, G.R. Reddy, P. Prasad, K.K. Vaze, C. Gupta
  "The performance of the Chaboche kinematic hardening model has been evaluated in this paper to predict the ratchetting responses for a broad set of uniaxial and biaxial loading histories. The investigations have been performed with reference to both uniaxial and biaxial experimental data, viz. (a) strain and stress controlled uniaxial tests on tensile specimens; (b) biaxial tests on straight pipes with constant internal pressure and cyclic bending load; and (c) a shake table test on elbow. The parameters of the Chaboche model have been calculated from the uniaxial strain controlled stable hysteresis loop. Amongst the various parameters in the Chaboche model, it has been found that the selection of the value of g3 plays a crucial role in achieving better simulation. The Chaboche model was observed to predict complete shakedown for g3 ¼ 0: On the other hand, the model closely simulated the experimental results for g3 ¼ 9: The same parameters have been used to analyze the biaxial loading condition. Ratchetting simulation studies by the Chaboche model have resulted in reasonably good agreement with experiments."
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User Implemented Nitinol Material Model in ANSYS
  Peter R. Barrett and Daniel Fridline
  "Nitinol is an acronym for NIckel TItanium Naval Ordinance Laboratory since the alloy was originally developed at the Naval Lab. It is used to describe a family of materials, which contain a nearly equal mixture of nickel and titanium. Nitinol alloys are attractive to the medical device industry because they are biocompatible and when processed correctly, are at their optimum superelastic behavior at body temperature.
"Nitinol exhibits a different stress-strain curve for loading and unloading that cannot be modeled with existing material models in ANSYS. This paper describes the implementation of a unique user material model in ANSYS that simulates the nitinol superelastic behavior. Example analyses are provided demonstrating the application of this material model for medical implant devices called stents."

[ANSYS Nonlinear, version unspecified]
Note that TB,SMA allows users to access built-in shape memory alloy constitutive model in ANSYS.
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USERMAT
  Document describing the USERMAT user material subroutine.
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Viscoelastic Properties of Filled Rubber. Experimental Observations and Material Modelling
  Bohdana Marvalova
  "The paper presents an application of a phenomenological material model for a viscoelastic stress response at large strains. The model is used for the simulation of carbon-black filled rubber in monotonic and cyclic deformation processes under isothermal conditions. The material stress response is decomposed into two constitutive parts which act in parallel: an elastic equilibrium stress response and a rate-dependent viscoelastic overstress response. The response of a particular filled rubber in the cyclic and relaxation tests was measured experimentally. The parameters of the constitutive functions are determined from the experimental data by an identification process employing nonlinear optimization methods. The paper concludes with a simulation by FEM of the cyclic loading of a simple rubber specimen."
[ANSYS Nonlinear, version 10]
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Viscoelasticity
  (ANSYS, Inc.)
  Presentation on the viscoelasticity model, introduced in ANSYS 6.1, available for both hypo- and hyper-elasticity (part of the "Advanced Analysis with ANSYS" seminar during the 2002 User's Conference).
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Average Rating: 8.5 (23 votes)  
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