Novel computational methods for high‐dimensional stochastic sensitivity analysis

This paper presents three new computational methods for calculating design sensitivities of statistical moments and reliability of high‐dimensional complex systems subject to random input. The first method represents a novel integration of the polynomial dimensional decomposition (PDD) of a multivariate stochastic response function and score functions. Applied to the statistical moments, the method provides mean‐square convergent analytical expressions of design sensitivities of the first two moments of a stochastic response. The second and third methods, relevant to probability distribution or reliability analysis, exploit two distinct combinations built on PDD: the PDD‐saddlepoint approximation (SPA) or PDD‐SPA method, entailing SPA and score functions; and the PDD‐Monte Carlo simulation (MCS) or PDD‐MCS method, utilizing the embedded MCS of the PDD approximation and score functions. For all three methods developed, the statistical moments or failure probabilities and their design sensitivities are both determined concurrently from a single stochastic analysis or simulation. Numerical examples, including a 100‐dimensional mathematical problem, indicate that the new methods developed provide not only theoretically convergent or accurate design sensitivities, but also computationally efficient solutions. A practical example involving robust design optimization of a three‐hole bracket illustrates the usefulness of the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Hochtemperaturprüfung – Ein Beitrag zur Werkstoffentwicklung und ‐qualifizierung sowie Simulation der Bauteilbeanspruchung

High temperature testing – A contribution to alloy development, alloy qualification and simulation of component loading In parallel to continued developments of steam and gas turbines as well as traffic engineering machines on the one hand, and marginal conditions like low specific fuel consumption and sufficient environment‐friendliness on the other hand, the aim of improving the degree of efficiency by augmenting process parameters such as temperature and pressure is being followed. These efforts impact especially components of thermic machines and facilities subject to high thermal and mechanic exposure. Still largely unexplored is the interaction between microstructure characteristics determined through chemical composition, production processes and heat treatment, changes in the microstructure due to multiaxial load and the time‐dependent deformation and stability resulting hereof. With regard to this background, improved methods of material properties determination, their modelling and transfer on the component enable to optimize wall thicknesses and degrees of efficiency. In the course of evaluation of static and cyclic material properties carried out also on faulty specimens, uncertainties occur which can originate from the testing process and analysis, as well as being influenced by the material itself and its process of production. Altogether, the demand for reliable determination of material properties and methods of scatterband treatment and their mathematical‐statistical evaluation is in business. For simulation, consistent material datasets that describe the complex interaction between temperature, period of exposure and type of exposure are needed. Summarizing, the tasks dealt with qualify the entire process from production to the operational behaviour of components.     

Real‐time Reliability Evaluation with a General Wiener Process‐based Degradation Model

The aim of this paper is to investigate the issue of real‐time reliability evaluation based on a general Wiener process‐based degradation model. With its mathematical tractability, the Wiener process with a linear drift has been widely used in the literature, to characterize the dynamics of the degradation process or its transformation. However, the nonlinear degradation process, which can't be properly linearized, exists in practice. The dynamics of such a degradation process can't be accurately captured by linear models. Here, a general Wiener process‐based degradation model is proposed, which covers a variety of Wiener process‐based models as its limiting cases. A two‐stage method is presented to estimate the unknown parameters. Two real‐time reliability evaluation procedures are presented for different conditions: one is the analytical evaluation procedure, and the other is the simulated evaluation procedure. It is shown that when new degradation information is available, the evaluation results can be adaptively updated. Moreover, to check out the proposed degradation model, a graphical method is provided. Finally, the validity of the proposed evaluation method is illustrated by a numerical example and two real‐world examples. Copyright © 2013 John Wiley & Sons, Ltd.     

Spannungs‐Dehnungs‐Linien von Porenbeton bei hohen Temperaturen: ein erster Schritt zur versuchsbasierten Bemessung gemäß EN 1996‐1‐2

Stress‐strain curves of AAC at high temperatures: a first step toward the performance‐based design according to EN 1996‐1‐2 In this paper, the performance‐based approach for the design of autoclaved aerated concrete (AAC) masonry walls subjected to fire is presented. The problems associated with the calculation methods in the current version of EN 1996‐1‐2 for the assessment of AAC loadbearing walls are explained. The current version of EN 1996‐1‐2 offers only tabulated data as a reliable method for structural fire assessment. The content of current Annex C and D is generally considered as not being reliable for design because of the absence of an adequate validation by experimental tests. For this reason, a proposal is made for the improvement of the input parameters for mechanical models based on experimental tests on AAC masonry. On this basis, new stress‐strain curves as a function of temperature are proposed here and then compared with the stress‐strain curves currently included in the Annex D of EN 1996‐1‐2. The comparison results point out that the current curves do not correspond to the effective behaviour of AAC masonry under fire conditions. The proposed curves can be used as base to be implemented in the new version of EN 1996‐1‐2.     

Die Integration der Lebensdauerberechnung in den Fahrzeugentwicklungsprozess am Beispiel MIG‐geschweißter Bauteile aus Aluminium im Fahrwerksbereich

Integration of the lifetime calculation in the automobile development process based on MIG‐welded aluminium chassis components The lifetime prediction results for metallic components depend significantly on the required calculation inputs. These inputs include the finite‐element‐meshing of the component geometry, the material properties and the load time histories for the component. In the present study the influence of the finite‐element‐modelling on the lifetime prediction is investigated, based on a line‐welded aluminium chassis component. Of special interest is the modelling of the weldline. For the lifetime calculation the software tool FEMFAT from “Engineering Center Steyr” is used. The evaluation of the lifetime prediction results for weldlines is based on a local stress approach. The qualification of the calculation for the product development process is described, based on typical BMW weldline S‐N‐curves.     

On inter‐element forces in the FEM‐displacement formulation,and implications for stress recovery

This paper describes a new technique for the determination of the inter‐element forces and tractions, as well as stress state at nodes, as a post‐processing step after the solution of standard FE‐displacement calculation. The work is motivated in the context of a broader development of a procedure to simulate fracture processes using a discrete approach without the need of double‐noded interface elements. The technique, easily implementable, is based on the double minimization of an objective function, representing the error between the inter‐element stress tractions and the projection of the best‐fit stress tensor T along the planes of the interfaces converging at an element corner node. The formulation is illustrated with some basic examples in which the resulting stress tensors and inter‐element forces are compared to theoretical solutions and to the results obtained by using a traditional stress average smoothing method. Copyright © 2005 John Wiley & Sons, Ltd.     

Out‐of‐plane bending moments in masonry walls – Analysis of different calculation methods

In the course of the revision of EN 1996‐1‐1, a new proposal has been made for the calculation of internal forces in frame‐type structures for the determination of bending moments due to slab rotation. In addition to a stiffness reduction for masonry walls in conjunction with the special features of partially supported slabs, which is already usual in Germany, the calculated ever‐present minimum loadbearing capacity of a wall is also increased due to a reduction of the maximum applied load eccentricity. Another major change is the direct implementation of wind loads in the method to determine the internal forces. To ensure that these changes do not lead to a safety deficit or an uneconomic reduction of the loadbearing capacity compared with the current situation, the results of extensive comparative calculations are presented. In addition, it is examined whether the proposal could conflict with further investigations to extend the conditions for application of the simplified design procedures according to EN 1996‐3. It is shown that the new draft provides similar results to the current method and that there are no concerns about its application. Also, the investigations to extend the conditions for application of the simplified calculation methods can be based on the new proposal without concerns.     

Adapting second‐order response surface designs to specific needs

Experimental design strategies most often involve an initial choice of a classic factorial or response surface design and adapt that design to meet restrictions or unique requirements of the system under study. One such experience is described here, in which the objective was to develop an efficient experimental design strategy that would facilitate building second‐order response models with excellent prediction capabilities. In development, careful consideration was paid to the desirable properties of response surface designs. Once developed, the proposed design was evaluated using Monte Carlo simulation to prove the concept, a pilot implementation of the design carried out to evaluate the accuracy of the response models, and a set of validation runs enacted to look for potential weaknesses in the approach. The purpose of the exercise was to develop a procedure to efficiently and effectively calibrate strain‐gauge balances to be used in wind tunnel testing. The current calibration testing procedure is based on a time‐intensive one‐factor‐at‐a‐time method. In this study, response surface methods were used to reduce the number of calibration runs required during the labor‐intensive heavy load calibration, to leverage the prediction capabilities of response surface designs, and to provide an estimate of uncertainty for the calibration models. Results of the three‐phased approach for design evaluation are presented. The new calibration process will require significantly fewer tests to achieve the same or improved levels of precision in balance calibration. Copyright © 2008 John Wiley & Sons, Ltd.     

Energy Conservation Ordinance 2014 – On the way to the nearly zero energy building / EnEV 2014 – auf dem Weg zum Niedrigstenergiegebäude

The tightening of the Energy Conservation Ordinance in 2016 provides the first step toward the introduction of nearly zero energy buildings. The level of performance for residential buildings after 2020 will most likely attain an energy quality close to the primary energy consumption of the KfW Efficiency House 55 today, at least regarding performance. The following report describes the requirements methodology of the Energy Conservation Ordinance 2014, including the KfW promotion, and provides calculation examples to clarify the issues.     

Experimental Determination of Shear‐Thinning Behaviour During Extrusion of Rubber Blends

Abstract: In this contribution, the influence of an extrusion process on the viscosity function of rubber blends is identified. This knowledge is required for realistic numerical simulations of injection heads and extrusion tools used for the fabrication of rubber profiles. The experimental basis of this investigation is tests with both, capillary and extrusion rheometer. The latter is a combination of an industrial extruder and an extrusion tool with a circular cross‐section, allowing application of material characterisation methods used for capillary experiments. Thus, the determination of the viscosity function of extruded rubber blends is possible. Additional capillary experiments enable the determination of the influence of an extrusion on the viscosity of rubber blends. For the identification of material parameters, a non‐linear iteration scheme is used, which is proven to be applicable for rubber compounds and rubber blends. The validation of the extrusion rheometer tests is performed by means of numerical back‐calculation of the corresponding pressure measurements.     

Example calculation of the sound insulation of a floor slab between residential units according to DIN 4109‐2:2016 / Beispielhafte Berechnung der Luftschalldämmung einer Wohnungstrenndecke im Mauerwerkbau nach DIN 4109‐2:2016

The DIN 4109 series of standards has been revised in recent years and harmonised with European design codes. After the drafts of DIN 4109 were issued in November 2013, the documents shall now be finally published in summer 2016. The calculation procedure according to DIN 4109‐2 is based on the simplified procedure from EN 12354:2000, in which the noise transmission routes are calculated individually, similarly to the calculation for framed buildings according to supplement 1 to DIN 4109. The procedure according to DIN 4109‐2 is based on formulae, which are filled with figures from the building element catalogue of parts 3‐2 to 3‐6. This article shows examples of calculation steps for the determination of the weighted airborne sound reduction R'_w,Raccording to DIN 4109‐2:2016 for a floor slab between residential units.     

A FEM‐based virtual test‐rig for hybrid metal‐composites clinching joints

A 3D FEM‐based virtual test‐rig tool for the hybrid metal‐composites clinching technology is developed and built in the commercial finite element software Abaqus. The proposed tool consists of two modules: a module to simulate the hybrid clinching process and another to predict the strength of the clinched joints. At first, experimental results concerning the hybrid metal‐composites (EN AW‐5754‐PA6GF30) clinching are presented. Then, the developed virtual tool is described in detail outlining the constitutive models implemented for the hybrid pairing sheets as well as illustrating the proposed FE numerical procedures. Later, the developed tool is applied to the hybrid pairing EN AW‐5754‐PA6GF30. In comparison to the conducted experiments, the simulation results obtained show the applicability and accuracy of the developed virtual testing tool.     

High yield spray forming of small diameter tubes using pressure‐gas‐atomization

The economy of the spray forming process is restricted by the generation of overspray, which in many cases cannot be re‐introduced into the process by re‐melting or co‐injection. Especially for small deposits, such as small diameter tubes (diameter <100 mm), the amount of overspray can become large in conventional spray‐forming processes. In this work, an alternative process with a pressure‐gas‐atomizer operating at low melt flows is presented. Tubes with diameters of 50 mm and 90 mm were spray‐formed and analyzed regarding yield and porosity. It was found that yields up to 96% can be achieved with porosities below 1% if proper process parameters are identified and used. An evaluation of the yield and the corresponding achievable porosity is conducted to identify resource‐efficient sets of parameters.     

Schweißzusatzwerkstoffe können/müssen nicht immer die Anforderungen der Grundwerkstoffe erfüllen

Weld metal as strong as base metal? The development of new steels is always a challenge for the manufacturer of filler metals. In many cases it is obvious that some properties of the base metal cannot be fulfilled with matching filler metals. In some cases, dissimilar filler metals can solve the problem in some cases, there is no chance to meet the requirements of the base metal (for example yield strengths of new ultra high strength steels). This paper deals with different kinds of new steels and the requirements for the weld metal with examples from motor car industry (Mangan Austenite), crane (Ultra high strength steels), earthmoving machinery (Wear‐resistant steels) and offshore (Supermartensitic steels). Specific problems will be discussed and best solutions will be highlighted. These examples make clear that the success of new kinds of steels in the market depends on solving the joining problems of these steels.     

Tragfähigkeitstafeln für unbewehrtes Mauerwerk nach DIN EN 1996‐3/NA:2019‐12

Load‐bearing capacity tables for unreinforced masonry according to DIN EN 1996‐3/NA:2019‐12 Practical design aids are important tools in the day‐to‐day business of structural design. The design of primarily vertically loaded masonry walls in usual building construction can be carried out with the help of so‐called load‐bearing capacity tables. A table value is read off exclusively as a function of the geometric conditions, which – multiplied by the masonry compressive strength – results in the load‐bearing capacity of the wall for cold design and in case of fire. By comparing the acting and resisting force, the verification of structural design can be provided in a simple and yet economical form. The bearing capacity tables based on the simplified calculation methods according to DIN EN 1996‐3/NA:2019‐12 [1], [2] and DIN EN 1996‐1‐2/NA:2013‐06 [3], [4] are presented in this paper. Compared to the previous edition of Part 3 of Eurocode 6, the extended scope of application is taken into account, as well as the normative changes to the construction method with partially supported slabs.     

Construction and validation of a scale of assessment of self‐care behaviors with arteriovenous fistula in hemodialysis

Several guidelines recommend the importance of educating the patient about the care of vascular access. Nurses have a key role in promoting the development of self‐care behaviors by providing the necessary knowledge to patients, so that they develop the necessary skills to take care of the arteriovenous fistula (AVF). This article describes the process of building a scale of assessment of self‐care behaviors with arteriovenous fistula in hemodialysis (ASBHD‐AVF). This is a cross‐sectional study in which the development, construction, and validation process followed the directions of the authors Streiner and Norman. This is a convenience sample, sequential, and nonprobabilistic constituted by 218 patients. The study was conducted in two stages during 2012–2014. The first phase corresponds to the scale construction process, 64 patients participated, while the second corresponds to the evaluation of metric properties and 154 patients participated. The principal component analysis revealed a two‐factor structure, with factorial weights between 0.805 and 0.511 and between 0.700 and 0.369, respectively, explaining 39.12% of the total variance of the responses. The Cronbach's alpha of the subscale management of signs and symptoms is 0.797 and from the subscale prevention of complications is 0.722. The ASBHD‐AVF revealed properties that allow its use to assess the self‐care behaviors in the maintenance and conservation of the AVF.     

Using Combined Bipolar Semantic Scales and Eye‐Tracking Metrics to Compare Consumer Perception of Real and Virtual Bottles

Three‐dimensional virtual representations of consumer products are expected to gain relevance in e‐commerce applications as low cost virtual reality headsets arrive on the market in the next years. However, there are a limited number of studies related to the perceptual evaluation of virtual products and their packaging where virtual and real (photographic) representations are compared. As part of an extensive exploration toward understanding product perception in virtual stores, this work presents a study with 38 participants in which consumer perceptions of a photographic and a virtual representation of a beer bottle are examined. Perceptual evaluation is assessed using two metrics: first, an evaluation was performed by applying a bipolar semantic scale based on four axes: novelty, resolution, style and emotion. Second, eye‐tracking metrics were employed to analyse participant gaze behaviour during the visualization of stimuli. Virtual bottles were modelled using a medium polygonal load (5 K polygons per bottle), and render quality was also medium to intentionally recreate the computing limitations of smartphone‐based virtual reality headsets. Results show that a medium render quality alters consumer perception and responses using semantic scales. Eye‐tracking analysis confirms that the orientation of the bottle and how it is presented also affect consumer perception. While some orientations result in similar eye‐tracking metrics, others show different results. Copyright © 2015 John Wiley & Sons, Ltd.     

Loadbearing capacity of infill masonry walls considering the deformation‐based membrane effect

According to currently valid codes, it is not possible to determine the loadbearing capacity of unreinforced infill walls considering the deformation‐based membrane effect by incorporating the exact support conditions. One reason for this is the lack of a validated calculation procedure, which in addition to the equilibrium conditions also realistically represents the compatibility conditions of these systems. In the present paper, therefore, a new non‐linear analytical calculation procedure is presented. The main focus of the analysis of walls subject to area loading is the incorporation of the support conditions and thus the consideration of the deformation‐based membrane compressive force. Through generalised formulation and a standardised notation of the determination equations, different material behaviours and various support conditions can be taken into account with few parameters. On the action side, both lighter loading like wind loads and heavier loading like explosion loads can be considered. Through the implementation of the partial factor concept, it is possible to comply with the requirements of European codes and thus ensure the applicability of the analysis model.     

Refined second order semi‐analytical design sensitivities

Accurate and efficient calculation of second order design sensitivities in a finite element context is often difficult. The semi‐analytical (SA) method is efficient and easy to implement but has accuracy problems even for first order shape design sensitivities. To overcome accuracy problems a refined semi‐analytical (RSA) method has been developed for first order sensitivities. The present paper investigates the application of the RSA method to second order design sensitivities. It is found that second order RSA sensitivities are significantly more accurate than their SA counterparts. Copyright © 2002 John Wiley & Sons, Ltd.     

Charakterisierung von Randentkohlungsvorgängen bei der Austenitisierung des Wälzlagerstahls 100Cr6. Teil 2: Modellierung des Kohlenstoff‐Tiefenverlaufs mit Hilfe der Methode der Finiten Elemente

Characterization of Decarburisation Processes During Austenitising of the Rolling Bearing Steel 100Cr6. Part 2: Modelling of the Carbon Concentration Profile by Means of the Finite Element Method The quantitative measurement of carbon concentration‐distance curves serves as fundamental prerequisite for the evaluation of rim zone properties connected with decarburisation processes in material science. This was shown in part 1 of the present work with two samples from through‐hardenable rolling bearing steel 100Cr6 (SAE 52100) austenitised in different oxidising atmospheres by position dependent determination of hardness, residual stresses, and X‐ray line broadening ({211} α’‐Fe diffraction line). In practice, it is important to predict carbon concentration‐distance curves under prevailing heat treatment conditions or to conclude conversely from profile measurements. Based on a refined kinetics model of a diffusion‐controlled process, part 2 therefore presents a simulation tool developed by means of the finite element method (FEM). Apart from the concentration dependence of the diffusion coefficient, it also considers the decarburisation induced austenite‐ferrite phase transformation, the time dependent influence of scaling, and variable atmosphere conditions. The interpretation of the carbon concentration‐distance curves, measured very accurately in the rim zone of both 100Cr6 samples by secondary ion mass spectrometry (SIMS), confirms the possibilities of application of the new numerical tool.