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- Billur, E., et al.
(författare)
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Factors affecting the accuracy of flow stress determined by the bulge test
- 2011
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Ingår i: Special Edition: 10th International Conference on Technology of Plasticity, ICTP 2011. - 9783514007840 ; , s. 726-731
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Konferensbidrag (refereegranskat)abstract
- The determination of the flow stress curve at room temperature, using the bulge test under biaxial deformation conditions, has been extensively studied. However, two Issues still deserve close examination: (1) validity of assuming a spherical bulge shape and (2) the effects of yield criterion and/or normal anisotropy. In this paper, we present experimental measurements to validate spherical assumption, as well as a methodology to calculate flow stress curves, all the way up to the failure point, that are free from the effects of anisotropy. Experimental studies were conducted on draw quality steel (DQS) and several grades of Dual Phase (DP) Advanced High Strength Steels (AHSS). © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.
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| 3. |
- Heikkilä, Irma, 1965-, et al.
(författare)
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Clean forming of stainless steel and titanium products by lubricious oxides
- 2012
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Ingår i: Proceedings of NORDTRIB. - Trondheim : NTNU. - 9788214052701
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Konferensbidrag (refereegranskat)abstract
- Big social benefits can be attained through increased use of stainless steel or titanium in new sheet metal applications. Unfortunately, forming of these materials is often a challenging and costly operation, that can lead to environmental and health problems when solving the technical limitations. One possible method to overcome these problems is to use an oxide layer with optimised properties to reduce friction during forming, either as a substitute to lubricants, or acting as a conversion layer for environmental friendly lubricants. The most beneficial group of oxides for low friction is called lubricious oxides with a rutile crystal structure. Oxides of Ti, Mo, V, and Zn can build rutiles under certain contact temperatures during rolling and forming. The aim of this investigation is to evaluate if oxides designed on metal sheets display a lubricious effect under conditions similar to industrial forming processes. Preliminary evaluations show a beneficial influence of two oxides types, on stainless steel and on titanium. More work is needed to test the lubricating effect in other forming operations and to analyse the sustainability aspects for products manufactured with this alternative surface.
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| 4. |
- Löfving, Malin E S, 1979, et al.
(författare)
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Evaluation of flexible automation for small batch production
- 2018
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Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 25, s. 177-184
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Konferensbidrag (refereegranskat)abstract
- Traditionally it has been difficult to use automation in small batch production with high variation in volumes and high mix of products. However, this is changing as there exist new types of flexible automation. The purpose of this paper is to understand the requirements on enterprises to use automation in small batch production, and evaluate flexible automation technologies suitable for small batch production. The study is based on literature reviews and interviews. Identified requirements are for example to change between manual access and automation, and easy programming. The results show that a flexible mobile robot automation may fulfill a majority of the identified requirements.
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| 5. |
- Löfving, Malin E S, 1979, et al.
(författare)
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Guide for Automation of Low VolumeProduction
- 2020
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Ingår i: Advances in Transdisciplinary Engineering. - 9781614994398 ; 13, s. 13-23
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Konferensbidrag (refereegranskat)abstract
- There is a remaining need from both academia and practitioners, to gainfurther knowledge about the decision making process for automation of low volumeproduction. This paper includes insights of drivers for automation, the developmentof a guide for low volume production and the outcome of using the guide. Theresearch in this study is based on both empirical data and theoretical considerations.The empirical data was collected in five case studies and a questionnaire. This paperis part of a research project with the main objective to develop knowledge about howflexible automation may contribute to improvements in efficiency, ergonomics,quality and production economics in different industries with low volumeproduction. One of the results in the project was a comprehensive guide, developed,refined and improved in an iterative collaborative process, where tools and parts ofthe guide were tested and verified by five manufacturing case companies. The paperdescribes briefly the development process of the guide and content. The requirementsof the guide derived from literature, case companies, questionnaire as well asindustrial experts. The resulting guide can be used in several ways, depending on therequirements of the application. The guide includes guiding principles, a decisionmodel for the analysis of the company, choice of automation and facts aboutautomation. In the end of the project, four companies had invested or decided toinvest in different types of automation.
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| 8. |
- Wadman, Boel, et al.
(författare)
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Influence of surface texture on the galling characteristics of lean duplex and austenitic stainless steels
- 2010
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Ingår i: Duplex World 2010 Conference & Exhibition. - Beaune, France.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations of sheet materials and lubricants. The strip reduction test, a severe sheet forming tribology test was used to simulate the conditions during ironing. This investigation shows that the risk of galling is highly dependent on the surface texture of the duplex steel. Trials were also performed in an industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed to high strain levels in tools normally applied for forming of austenitic steels, but tool adaptations are needed to comply with the higher strength and springback of the material.
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| 10. |
- Wadman, Boel, 1960
(författare)
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Mechanisms of Uniform Corrosion of Zirconium Alloys in Water and Steam
- 1993
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Zirconium alloys are used in key components in nuclear reactors, e.g. fuel cladding tubes in pressurised water reactors. Current trends towards extended burnup of the nuclear fuel in these reactors have accentuated the demand for Zr alloys with higher uniform corrosion resistance under irradiation and lower hydrogen absorption. The first part of this work was performed to investigate the matrix composition, that was proposed to influence the uniform corrosion resistance of Zircaloy, the traditional fuel cladding material. The first direct measurements were made of the concentrations of the alloying elements Fe, Cr and Ni in the matrix in five Zircaloy materials, using atom probe microanalysis. In all five materials the matrix was highly depleted with respect to alloying elements. Only 100-200 wt.ppm of Fe, Cr and Ni remained in the matrix, which is approximately 10% of the bulk composition. The measured concentrations correspond well to recent diffusion and solubility data for Zircaloys. In the second part of this study the oxide microstructure was related to the corrosion resistance and hydrogen uptake of zirconium alloys with different composition and heat treatments. The initial oxidation in air or water of Zr-4 needles was studied with atom probe analysis and transmission electron microscopy (TEM). The grain size of the thin oxide layers was approximately 5 nm, and the oxide composition was ZrO. Thin foil cross-sections were prepared of the metal-oxide interface and of the oxide layers grown in static autoclave at 400 °C steam on Zircaloy-4 and Zr-0.5Sn- 0.53Nb. Oxides in the thickness range 1-42 µm were examined with TEM. For comparison, one low-annealed Zr-4 material with high uniform corrosion rate was also investigated. In the metal-oxide interface of all materials, small columnar ZrO2 grains (Ã? 15 x 100 nm) were observed growing in direct contact with the metal. No amorphous layer was found in the oxide-metal interface or between columnar grains. Thin oxide layers (pre-transition, Ã? 1 µm) were dense, while thick (post transition) oxide layers contained some cracks close to equiaxed grains. On the low-annealed Zr-4, thick oxide layers contained a high number of equiaxed grains, and intergranular pores and cracks were frequent even close to the interface. The metal-oxide interface had a less ordered structure, with shorter columnar or equiaxed oxide grains. In post-transition oxide layers of the Zr-Sn-Nb alloy (which had a lower relative hydrogen uptake) a crystalline 20-100 nm thick intermediate layer in the metal-oxide interface was found.
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