Efficient and accurate Simulation method simulation methods are key for all development processes in all industries. Without simulation all influences of design changes, material choices, load situations, etc., on the performances of parts, sub-systems and systems, need to be confirmed by time consuming and expensive test procedures. On the other hand, including these influences into the design process by simulation together with efficient optimisation strategies allows to balance different performances, while allowing cost-efficient and ecological manufacturing as well as keeping a low weight of the complete system at the same time. To gain accurate results in a simulation, it is not sufficient to just model the geometry correctly; a main challenge is to model theMaterialbehaviour material behaviour correctly. State of the art for metal based structures is to use Materialdata material data that have been gained in experiments. Especially for fatigue performances, the expected lifetimeFatigue fatigue material data is derived from databases or so called material laws. This approach does not take into account any manufacturing influences, even though these can locally lead to much improved behaviour. Therefore these parts are often still over-designed with respect to fatigue. For composite materials this approach is not even valid anymore as the behaviour strongly depends on theManufacturing process manufacturing process. Those influences can be analysed if one looks closer, i.e. at a different scale. The behaviour at the smaller scale then defines the material behaviour at the global scale. This process may even be recursive: even smaller scales are needed for the behaviour of intermediate scales—even down to atomistic levels. It is clear that such approaches can lead to tremendous computational cost. Therefore it is a key need to keep the process efficient, on one hand by analysing the methodologies on each scale, on the other hand by intelligent choice of the best method at each location.

The aim of this study is to deal with the simulation of intralaminar fatigue damage in unidirectional composite under multi-axial and variable amplitude loadings. The variable amplitude and multi-axial loading is accounted for by using the damage hysteresis operator based on Brokate method [6]. The proposed damage model for fatigue is based on stiffness degradation laws from Van Paepegem combined with the ‘damage’ cycle jump approach extended to deal with unidirectional carbon fibres. The parameter identification method is here presented and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the Ladevèze damage model and the permanent shear strain accumulation based on Van Paepegem’s formulation. This approach is implemented into commercial software (Siemens PLM). The validation case is run on a bending test coupon (with arbitrary stacking sequence and load level) in order to minimise the risk of inter-laminar damages. This intra-laminar fatigue damage model combined efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level. This work concludes on the next challenges to be addressed (validation tests, multiple-loadings validation, failure criteria, inter-laminar damages…).

Short-fiber reinforced parts show a distinct anisotropic behavior, caused by the alignment of the fibers during the injection molding process. The injection molding simulation provides the local probability distribution of the fibers (orientation tensor). By applying multi-scale material models it is possible to estimate the local anisotropic stiffness. This leads to considerable more accurate results in a subsequent FEA as with isotropic approaches. This is true even if higher temperatures lead to local plasticity. Tools that enable this integrative simulation approach have been established in the last years. To account for the anisotropic fatigue behavior an interpolation of fatigue strength at a discrete fiber orientation distribution is often used by estimating the anisotropic stiffnesses in direction of the orientation tensor principal directions. This is in most cases not appropriate. In the paper an approach is described that uses a so-called Master SN curve concept which estimates SN curves for varying local fiber orientation distributions. For the application case of high temperatures and local plasticity several enhancements were implemented and tested. The methodology is verified at the example of an oil-filter system under pressure at elevated temperature.

Traditionally fatigue damage is associated with time dependent loading, in the form of local stress or strain histories. But there are load situations both in the lab testing as well as in the real world, where the determination and definition of the loads are more efficiently conducted in the frequency domain. Be it as deterministic sine sweeps or random stationary processes. For uni-axial loads the simulation of these signals on shaker tables has been analyzed in the past.But if we go to multiple loads which are somehow correlated new aspects have to be taken into account as the correlation or phasing have an important impact on the fatigue life - imagine the loads on a truck frame where there is a definite correlation between the loads from the front and rear axles.In this paper we present the methodology to handle multiple loads and also how to correctly handle the local stresses evaluated from multiple correlated signals, if used for a fatigue analysis. We show why traditional equivalent stress approaches bases on von Mises or principal stresses are problematic and the critical plane approach should be used. We discuss on how information on the behavior with respect to in-phase and out-of-phase loading can be analyzed and how it can be used to design better test setups on the shaker table. (C) 2013 The Authors. Published by Elsevier Ltd.

Optimized Analysis Process for the Fatigue Analysis of Cast Iron Structures Taking into Account the Local Material Structure. The manufacturing process has in many cases a large influence on the local fatigue behavior of structures. Ignoring it enforces the use of worst case material data and therefore highly conservative and heavy designs. For the fatigue design of casted structures one uses in today's practice mostly homogeneous material properties. This paper presents a full simulation process chain, taking into account the locally varying microstructure from casting and demonstrates the process chain using the tools Magmasoft - Abaqus - Virtual.Lab Durability on the example of an nodular cast iron component.

Kurzfassung Der Herstellungsprozess hat in vielen Fällen einen großen Einfluss auf die Betriebsfestigkeit von Bauteilen. Wird dieser vernachlässigt, führt dies im Allgemeinen zu unnötig konservativer Bauteilauslegung und hohen Bauteilgewichten. So wird in der Betriebsfestigkeitsberechnung für Gusseisenkomponenten heute – mangels quantitativer Informationen – meist von homogenen Materialeigenschaften ausgegangen. In diesem Beitrag wird ein durchgehender Berechnungsprozess entlang der Programmpakete Magmasoft – Abaqus – Virtual. Lab Durability vorgestellt, der die erstarrungsbedingt örtlich variierenden Gefügeeigenschaften im Bauteil berücksichtigt. Der Prozess wird exemplarisch an einem Sphäroguss-Bauteil demonstriert.

In the last two decades the development time of vehicles has been drastically reduced from eight to three years due to the application of advanced numerical and experimental methods. The specifications including comfort, driving behaviour and durability for every new model are being raised for every vehicle. The development responsibility is passed on to the supplier who, at the start, with limited information, makes a commitment with a fixed price for the production lead time. The aim of the paper is to show the damage operator approach with creep extensions integrated into the LMS Virtual.Lab Durability thermal fatigue module. The subject of the investigation is a turbocharger turbine housing that is exposed to high mechanical and thermal loads leading to considerable creep during its usage. The presented strain-life approach is based on the isothermal cyclically stable stress-strain and Manson-Coffin-Morrow strain-life curves. The finite element model of the turbocharger turbine housing is analysed numerically. A new extension to the Neuber approximation formulas that include viscoplastic correction is used to facilitate the finite element analysis runs. Results are compared with full finite element analysis and with tests.

The need of weight reduction for fuel reduction and CO2 regulations enforces the use of light-weight materials for structural parts also. The importance of reinforced composites will grow in this area. While the structural behavior and the simulation up to high strain-rate processes for those materials has been in the focus of investigation for many years, nowadays the simulation of high cycle fatigue behavior is getting important as well. Efficient fatigue analysis for metals was developed by understanding the microscopic behavior (crack nucleation and initiation) and bringing it to the macroscopic level by combining it with the matching test data (SN curves etc.). Similar approaches can be applied to composite materials as well. The paper gives a comprehensive review of fatigue simulation of fibre reinforced composite, based on the authors’ experience in this field for different types of composites like random fiber reinforced to textile reinforcements, from detailed

The article focuses on the application of a recently developed damage operator-based lifetime calculation to a thermomechanically loaded exhaust downpipe. The damage operator approach enabling online continuous damage calculations for isothermal and non-isothermal loading with mean stress corrections is reviewed. The article also highlights an extension of the strain-life approach to take into account viscoplastic effects and creep. The transient results from thermal and structural analyses using finite element analyses have been applied to the exhaust downpipe in LMS Virtual.Lab and the damage predicted. Tested exhaust downpipes were then subjected to the same loading conditions as in the calculation, and load cycles were repeated up to the point of failure. Simulated and test results are comparable.

Nowadays, mechanical industries operate in a highly competitive environment, therefore the process of developing a component from concept through detailed Computer-Aided Engineering (CAE) and performance validation is optimized for reduced development time and increased product performance. To continuously improve the product design and performance and reduce the costs and time to market, the design and performance engineering is shifted more and more towards virtual modeling and simulation processes from the expensive test-based design evaluations. Secondly, the booming introduction of active and adaptive systems in mechanical structures leads to a ‘mechatronics systems’ revolution, which further improves the product performance at the expense of increased system complexity. It is noted that the potential of structural dynamics test and analysis methods for addressing a structural dynamics design assessment or design optimization depends largely on the confidence that one can have in the results. That is, the results must be accurate, characteristic for the actual problem (and not be the result of testing artifacts) and representative for the actual behavior of the investigated structure. In this context, a key aspect is to be aware of the key sources of uncertainty in the designed product, and the impact thereof on the product performance in terms of structural dynamics, crashworthiness and/or acoustics. This paper reviews the main elements of test data and modal modeling uncertainty and assesses the impact of the uncertainty on some typical modeling problems taken from automotive and aerospace industry.

In the last decades the development time of vehicles has been drastically reduced due to the application of advanced numerical and experimental methods. Specifications concerning durability and other functional attributes for every new model improve for every vehicle.In particular, for machines and components under variable multiaxial loading, fatigue evaluation is one of the most important steps in the design process. Appropriate material testing and simulation is the key to efficient life prediction.However, the life of automotive components, power plants and other high-temperature facilities depends mostly on thermo-mechanical fatigue (TMF). This is due to the normally variable service conditions, which contain the phases of startup, full load, partial load and shut-down.Within this context, there are several requirements for making accurate life predictions: a proper material model with material parameters derived from testing, modeling of stress-strain response during cyclic loading, a multiaxial fatigue criterion, a proper damage accumulation model and component testing to evaluate the correlation between life prediction models and experiments.For high temperatures the influence of creep, creep fatigue and viscoplastic stress relaxation have to be considered both in an accurate way and efficiently.The present paper presents the damage operator approach enabling online continuous damage calculation for isothermal and non-isothermal loading with mean stress correction. The cycle closure point, cycle equivalent temperature, threshold temperature and separate rainflow counting (mandatory for the equivalent temperature approach) are not necessary any more for the damage operator approach. In fact, for constant temperature, both approaches are equivalent for the second run of block loading. It also highlights an extension of the strain-life approach to take into account viscoplastic effects and creep.