| 1. |
- Biermann, D., et al.
(author)
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Modelling and simulation of thermal effects in internal traverse grinding of hardened bearing steel
- 2016
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In: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 0007-8506. ; 65:1, s. 321-324
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Journal article (peer-reviewed)abstract
- Internal traverse grinding with electro-plated cBN wheels combines the advantages of both internal hard turning and internal grinding, enabling a high material removal rate along with a high surface quality. The drawback, however, is a high thermal load on the workpiece, resulting in shape and dimension errors of the finished part. This paper deals with the compensation of these manufacturing errors with a hybrid simulation system. It combines thermo-mechanically coupled finite element models on both meso- and macro-scale with a scale-bridging kinematic simulation system, enabling the prediction of the resulting temperatures and the development of corresponding simulation-based compensation strategies.
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| 2. |
- Buhaug, H., et al.
(author)
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One effect to rule them all? : A comment on climate and conflict
- 2014
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In: Climatic Change. - Dordrecht : Springer Netherlands. - 0165-0009 .- 1573-1480. ; 127:3-4, s. 391-397
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Journal article (other academic/artistic)abstract
- A recent Climatic Change review article reports a remarkable convergence of scientific evidence for a link between climatic events and violent intergroup conflict, thus departing markedly from other contemporary assessments of the empirical literature. This commentary revisits the review in order to understand the discrepancy. We believe the origins of the disagreement can be traced back to the review article's underlying quantitative meta-analysis, which suffers from shortcomings with respect to sample selection and analytical coherence. A modified assessment that addresses some of these problems suggests that scientific research on climate and conflict to date has produced mixed and inconclusive results.
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| 3. |
- Holtermann, Andreas, et al.
(author)
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A practical guidance for assessments of sedentary behavior at work: A PEROSH initiative
- 2017
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In: Applied Ergonomics. - : Elsevier BV. - 0003-6870 .- 1872-9126. ; 63, s. 41-52
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Journal article (peer-reviewed)abstract
- Sedentary behavior is defined as sitting or lying with low energy expenditure. Humans in industrialized societies spend an increasing amount of time in sedentary behaviors every day. This has been associated with detrimental health outcomes. Despite a growing interest in the health effects of sedentary behavior at work, associations remain unclear, plausibly due to poor and diverse methods for assessing sedentary behavior. Thus, good practice guidance for researchers and practitioners on how to assess occupational sedentary behavior are needed. The aim of this paper is to provide a practical guidance for practitioners and researchers on how to assess occupational sedentary behavior. Ambulatory systems for use in field applications (wearables) are a promising approach for sedentary behavior assessment. Many different small-size consumer wearables, with long battery life and high data storage capacity are commercially available today. However, no stand-alone commercial system is able to assess sedentary behavior in accordance with its definition. The present paper offers decision support for practitioners and researchers in selecting wearables and data collection strategies for their purpose of study on sedentary behavior. Valid and reliable assessment of occupational sedentary behavior is currently not easy. Several aspects need to be considered in the decision process on how to assess sedentary behavior. There is a need for development of a cheap and easily useable wearable for assessment of occupational sedentary behavior by researchers and practitioners
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| 4. |
- Holtermann, R., et al.
(author)
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A Hybrid Approach to the Modelling and Simulation of Grinding Processes
- 2014
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In: Proceedings of the 11th World Congress on Computational Mechanics (WCCM XI); 5th European Conference on Computational Mechanics (ECCM V); 6th European Conference on Computational Fluid Dynamics (ECFD VI). - 9788494284472 ; , s. 1932-1937
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Conference paper (peer-reviewed)abstract
- We present recent advances in the modelling and simulation of Internal Traverse Grinding, a high performance grinding process incorporating a high rate of material removal combined with a high surface quality. Due to a special grinding wheel geometry, the latter two goals are achieved in just one pass of the tool through the axisymmetric workpiece. The simulation framework we present generally consists of three components. The first one is a parametric plane strain, h-adaptive finite element model capturing the material penetration of a single cBN grain on a meso-scale during the machining process. Secondly, a topography analysis procedure as well as a kinematic simulation have been developed to measure and analyse the surface topography of an actual grinding wheel. We then use this information to model the grinding wheel surface in the latter kinematic simulation. This enables us to perform an exact calculation of the transient penetration history of every grain intersecting with the workpiece bulk. The superposition of these results is then used in the third component of the simulation framework, namely a process scale workpiece model currently under development which captures the effects of thermo-mechanical loads on the workpiece undergoing material removal and thus, in the near future, shall enable us to predict potential unwanted phase transformations of the bulk surface as well as size and shape errors of the finished part. In this contribution, we will focus on the first two parts of the simulation framework, namely the meso-scale as well as the kinematic simulation and the coupling between the two scales.
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| 5. |
- Holtermann, R., et al.
(author)
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Numerical Determination of Process Values Influencing the Surface Integrity in Grinding
- 2016
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In: 3rd CIRP Conference on Surface Integrity. - : Elsevier BV. - 2212-8271. - 9781510824621 ; 45, s. 39-42
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Conference paper (peer-reviewed)abstract
- Internal traverse grinding with electroplated cBN wheels using high-speed process conditions combines high material removal rates and a high surface quality of the workpiece in one single grinding stroke. In order to capture the macroscopic and mesoscopic thermo-mechanical loads onto the workpiece during internal traverse grinding, numerical simulations are conducted at the two scales. This results in a hybrid approach coupling two finite element models with a geometric kinematic simulation. The article focuses on the influence of multiple grain engagements onto a surface layer region using a two-dimensional chip formation simulation.
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| 6. |
- Schumann, S., et al.
(author)
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Determination of the Thermal Load Distribution in Internal Traverse Grinding using a Geometric-Kinematic Simulation
- 2015
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In: 15th CIRP Conference on Modelling of Machining Operations (15TH CMMO). - : Elsevier BV. - 2212-8271. ; 31, s. 322-327
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Conference paper (peer-reviewed)abstract
- During grinding processes, numerous grains interact with the workpiece material producing mechanical and thermal loads on the surface. In the field of thermal simulation of grinding processes, a widely used approach is to substitute numerous cutting edges by a single moving distributed heat source of a specific geometrical shape referring to the theory of Carslaw and Jaeger. This heat source is then moved across the modelled workpiece according to the specific kinematics of the grinding process. The geometrical shape of the substituted heat source can usually be determined using different approaches, e.g., predefined distribution functions or, more precisely, based on measurements of the shear stress within the contact zone. Referring to the state of the art, it is not possible to measure the shear stress within the contact zone during internal traverse grinding with roughing and finishing zone because of its very complex engagement conditions and the non-rectangular shape of its contact zone. In this work, a novel approach to determining a heat source distribution based on a geometric-kinematic simulation for internal traverse grinding is presented. This simulation identifies the ideal geometrical interaction of workpiece and grinding wheel. For this purpose, the specific material removal rate for each grain is calculated and accumulated with respect to the contact zone resulting in a three-dimensional thermal load distribution. This heat source can be used in finite element simulations to determine the thermal load on the workpiece. (C) 2015 The Authors. Published by Elsevier B.V.
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