Long-term water absorption tests for frost insulation materials taking into account frost attack

Analysis 1

This article is written by J. Adamus, P. Lacki, M. Motyka. The qualifications of the author's are engineers of civil constructions and mechanics. Audience of this article are students, master's students, professors, scientists and engineers of constructions and mechanics.

This article is about that the growing demand for high strength, lightweight and corrosion-resistant drawn parts has created increasing interest in the use of titanium and its alloys. Additional benefits may result from the use of tailor-welded blanks, allowing for significant savings in material, and the possibility of applying higher strength sheets exactly where needed. When forming welded blanks, it is necessary to overcome many technological barriers which are not reflected in technical literature. Therefore, some prior experience in numerical simulations is needed before embarking on further studies of welded blanks formability. For this purpose, it is necessary to determine the mechanical parameters of the base materials, as well as the fusion and heat-affected zones.

The obtained results allow for improvement to the numerical model of sheet-metal forming welded blanks and consequently, it will allow for better agreement between the numerical and empirical results.

Prime examples of sources that author's used are:

[9] M. Hyrcza-Michalska, J. Rojek, O. Fruitos, Numerical simulation of car body elements pressing applying tailor welded blanks – practical verification of results, Archives of Civil and Mechanical Engineering 10 (4) (2010) 31–44.

[10] C.P. Lai, L.C. Chan, Comparative study of forming titanium tailor-welded blanks under single and multi-stage forming process at elevated temperatures, in: Proceeding of the 11th World Conference on Titanium (Ti-2007), 2007, 1013– 1016.

[11] C.P. Lai, L.C. Chan, C.L. Chow, Warm forming simulation of titanium tailor-welded blanks with experimental verification, in: Materials Processing and Design – Proceeding of the 9th International Conference on Numerical Methods in Industrial Forming Processes, Porto, Portugal, (2007), pp. 1621–1626.

[12] J. Sinke, C. Iacono, A.A. Zadpoor, Tailor made blanks for the aerospace industry, International Journal of Material Forming 3 (1) (2010) 849–852.

[13] J. Sinke, A.A. Zadpoor, R. Benedictus, Tailor made blanks for aerospace industry, in: B.L. Kinsey, X. Wu (Eds.), Tailor Welded Blanks for Advanced Manufacturing, Woodhead Publishing Limited, Cambridge UK, 2011, pp. 181–202.

[14] A.A. Zadpoor, J. Sinke, R. Benedictus, Mechanics of tailor-welded blanks: an overview, Key Engineering Materials 344 (2007) 373–382.

In the article the sources given like below: Hyrcza-Michalska et al. [9], Lai and Chan [10], Lai et al. [11], Sinke et al. [12,13] and Zadpoor et al. [14] have pointed out that additional benefits may result from the use of so-called tailor-welded blanks. [14] have pointed out that additional benefits may result from the use of so-called tailor-welded blanks.

The author's statment of purposeto analyse titanium welded blanks as a material used for drawn parts. For instance, Adamus [26,27], Adamus and Lacki [28,29], Ceretti et al. [30], Lacki et al. [25], Motyka and Sieniawski [31], and Yang et al. [32] discussed that forming titanium sheets is not an easy task, especially titanium alloys which are characterised as being poorly drawable at ambient temperature. The tailor-welded blank concept is even more difficult. The weld poses an additional obstacle in forming. Adamus et al. [35], Akman et al. [15], Lacki et al. [25], Lai et al. [33,11,10], Li et al. [16], Winowiecka et al. [34] and Zadpoor et al. [14] pointed out that it limits the ductility of TWBs.

Methods used in the article are "Specific material zones distinguished on basis of scratch test and metallographic observations", "Specific material zones distinguished on basis of hardness measurements and metallographic observations"," Microstructure of the EBW joint between Gr 5 and Gr 2", "Metallographic examinations".

The authors comes to conclusion that, all the experimental studies have shown that there are at least 5 areas with different mechanical properties in EBW titanium blanks. By extension, the authors hypothesise that nonuniformity in material flow during sheet-metal forming processes. Therefore, a numerical model of sheet-metal forming should take into consideration these zones. It allows for increasing the accuracy of numerical simulation results. Further studies will be focused on searching mathematical correlation between titanium material hardness and its mechanical properties.

Analysis 3

The authors of this article are W.Kollek and U.Radziwanowska. Possibly the paper is addressed for engineers especially for those working in civil and mechanical. The article about energetic efficiency of gear micropumps . Authors used International Symposium, International and National journals and sources for the article.

The purpose of the article is to analyze pump design that belongs to microhydraulic elements group. The paper also provides numerical calculations for the pump as well as the results of the static mechanical analysis of gear mycropump body.

The author used two models: geometric and discrete as their evidence. The method used for analysis and calculations was finite element method and the method was conducted using Ansys Multiphysics software.

As a result of the analysis of stress and displacement distribution a mass optimization of the pump was provided. In this optimized pump maximum stress was at 134 MPa with safety factor 2.9

Also displacement of 0.02 mm was recorded. The main result of the article is that optimized mycropump has a minimum of 30% increase in energetic efficiency ratios to primary body.

The authors conducted that optimized pump with a reduced weight while maintaining mechanical properties is important for production because there is a possibility to increase efficiency of production and reduce production price of the pump.

Analysis 4

Long-term water absorption tests for frost insulation materials taking into account frost attack

This article is written by Toni A.Pakkala, Jukka Lahdensivu..The qualifications of the author's are Tampere University of Technology. Audience of this article are students, master's students, professors, scientists and engineers of constructions and mechanics.

This article is about that Water absorption of several different frost insulation materials. Materials was tested for four years. On the basis of the research the water absorption on XPS specimens is significantly minor compared to EPS specimens that were studied. The most significant result was that freezing of test specimens did not affect on water absorption of XPS specimens but had a major effect on water absorption of EPS specimens. With frozen EPS specimen the absorption continued increasing even after 48 months of immersion. Presumably the reason for such a behaviour is that the pore structure of EPS is not able to resist the tension caused by freezing water and therefore cracks are formed. Thus, more water absorbs inside the EPS through the cracks and it causes cracking deeper in the specimen which is why absorption increases after every freezing period.

Prime examples of sources that author's used are:

The author's statment of purposeto protect the building and the foundation as well as car and railways from freezing in the Nordic countries where the soil is frost susceptible.

For instance, The thickness of frost insulation material depends on the cold content of the year. The maturity used in calculations in Finland varies between 35,000 Kh (south coastal area) and 65,000 Kh (northern Lapland) (Finnish Meteorological Institute, 2013). Typical thickness of frost insulation is, respectively, 100–150 mm, see Fig. 1. Incomplete or incorrectly installed frost insulation can cause damage not only to the foundations of the building but also the walls, ceiling or roof structures. The frost insulation plans, quality of the products and installation of frost insulation must be paid special attention. It is crucial that frost susceptible soil will stay always unfrozen. Thermal insulation materials used for frost protection are typically expanded polystyrene (EPS) or extrusion-compressed polystyrene (XPS). Both EPS and XPS products have several different purposes of use and therefore different grades. The grade of thermal insulation depends on the needed load bearing capacity of thermal insulation.

Methods used in the article are " Immersion", " Weighing of specimens",

" Freeze–thaw"

The authors comes to conclusion that, On the basis of the research the water absorption on XPS specimens is significantly minor compared to EPS specimens that were studied. The most significant result was that freezing of test specimens did not affect on water absorption of XPS specimens but had a major effect on water absorption of EPS specimens. With frozen EPS specimen the absorption continued increasing even after 48 months of immersion. Presumably the reason for such behavior is that the pore structure of EPS is not able to resist the tension caused by freezing water and therefore cracks are formed. Thus, more water gets absorbed inside the EPS through the cracks and it causes cracking deeper in the specimen which is why absorption increases after every freezing period.

The individual issue affecting on water absorption of XPS specimens the most was the manufacturing time. The oldest specimens (18 months from manufacturing) did absorb less than half compared to a month old specimens. The result indicates that ageing time is important not only because of shrinkage of material but also for water absorption.

The specimens were exposed to much higher moisture stress during the tests than frost insulation plates exposed in normal structures. Experimental arrangement will correspond to a situation, where frost insulation will stay permanently under groundwater or perched water table e.g. when subsurface drainage has lost its ability to function. For this reason it is not possible to draw a conclusion for eligibility of tested materials for typical frost insulation. On the other hand, the target service life for frost insulation is long, generally 50 years at least, and the condition of frost insulation is not possible to find out without excavation and laboratory tests. This is the reason why short time test of frost insulation materials should be exposed to harsh circumstances.

Analysis 5

Date: 2016-01-03; view: 656