A reaction-driven evolving network theory coupled with phase-field fracture to model polymer oxidative aging

2021 ◽  
Vol 150 ◽  
pp. 104347
Author(s):  
Shabnam Konica ◽  
Trisha Sain
2020 ◽  
Author(s):  
Shabnam Konica ◽  
Trisha Sain

High temperature oxidation in polymers is a complex phenomenon, driven by the coupled diffusion-reaction process, causing changes in the amorphous network structure and resulting in property degradation. Prolonged oxidation in polymers results in the formation of a coarse, oxide layer on the outer surface and induces spontaneous cracking inside the material. In this paper, we present a chemical reaction-driven evolving network theory coupled with phase-field fracture to describe the effect of oxidation in polymers across different length scales. The theory considers the coupling between oxygen diffusion, chemical reactions, large deformation of polymers, and phase-field fracture in a thermodynamically consistent way. Guided by the statistical mechanics, the network theory has been introduced to model the reaction induced chain scissions and crosslinking events causing significant changes in the three-dimensional network structure. Further, these microscale events have been considered as the reason behind macroscopic mechanical property degradation, namely oxidative embrittlement. Finally the network theory is coupled with a phase-field fracture model to capture the macroscale damage and fracture in the polymer under stress-coupled oxidation conditions. We derive the specific constitutive forms for all the physical-chemical processes based on the thermodynamic inequality conditions, and numerically implement the theory in finite elements by writing ABAQUS user-defined element (UEL) subroutine. To present the model's capability, numerical examples with standard fracture geometries have been studied. The simulation results have demonstrated the model's capability of predicting the effect of oxidative aging on the polymer's response.


PAMM ◽  
2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Jannik Voges ◽  
Daniel Juhre

Author(s):  
G. Mackiewicz Ludtka

Historically, metals exhibit superplasticity only while forming in a two-phase field because a two-phase microstructure helps ensure a fine, stable grain size. In the U-5.8 Nb alloy, superplastici ty exists for up to 2 h in the single phase field (γ1) at 670°C. This is above the equilibrium monotectoid temperature of 647°C. Utilizing dilatometry, the superplastic (SP) U-5.8 Nb alloy requires superheating to 658°C to initiate the α+γ2 → γ1 transformation at a heating rate of 1.5°C/s. Hence, the U-5.8 Nb alloy exhibits an anomolous superplastic behavior.


Author(s):  
Huda Ibrahim ◽  
Hasmiah Kasimin

An effi cient and effective information technology transfer from developed countries to Malaysia is an important issue as a prerequisite to support the ICT needs of the country to become not only a ICT user but also a ICT producer. One of the factors that infl uences successful information technology transfer is managing the process of how technology transfer occurs in one environment. It involves managing interaction between all parties concerned which requires an organized strategy and action toward accomplishing technology transfer objective in an integrated and effective mode. Using a conceptual framework based on the Actor Network Theory (ANT), this paper will analyse a successful information technology transfer process at a private company which is also a supplier of information technology (IT) products to the local market. This framework will explain how the company has come up with a successful technology transfer in a local environment. Our study shows that the company had given interest to its relationships with all the parties involved in the transfer process. The technology transfer programme and the strategy formulated take into account the characteristics of technology and all those involved.  


2014 ◽  
Vol 1 (1) ◽  
pp. 47-56
Author(s):  
Milan Palat

Bu çalışmanın amacı, Türkiye’den göç ve Almanya’nın ekonomik göstergeleri arasındaki ilişkiyi, nicel metot yöntemleri kullanarak değerlendirmektir. Türkiye’nin belirsiz Avrupa ile bütünleşme beklentilerine rağmen  Avrupa Birliğinin köklü üyelerine olan Türk göçü devam edecektir. Çok sayıda Türk azınlığın yaşadığı ve hayat standartlarının yüksek olduğu Almanya, Hollanda ve Fransa’ya  büyük bir göç dalgası gerçekleşebilir. Çalışmanın istatistiksel bölümünün sonuçları, toplam göç ile gayri safi yurtiçi hasıladaki büyüme arasında pozitif, toplam göç ile işsizlik arasındaki negatif ve tahmin edilen bağımlılık yönüyle uygunluk içerisinde olan toplam göç ile aylık gelir arasında pozitif ilişki olduğunu göstermektedir. Türkiye’den göçle işsizlik arasındaki ilişki, toplam göçle olan ilişkiden daha düşüktür. Ancak, Almanya’daki yabancı mevcudiyeti ile Türkiye’den göç arasında bir ilişki bulunmaktadır. Bu durum, var olan göçmen topluluğunun olduğu yerin, yeni göçmenleri, köken bağlarına dayanarak cezbetmesi ve maliyet- riskler sebebiyle göçün düşük seviye de olduğuna dayanan kuramsal Ağ teorisi görüşü ile uygunluk göstermektedir. Göç ve işsizlik arasında gözlenen ilişki, Almanya’ya göçün  işgücü piyasasında talepte meydana gelen değişime karşılık geldiği gerçeğini göstermektedir. İşsizlik ve göç olgularının meydana geliş zamanlarında bir aralık  olsa bile  göç, Alman emek pazarında var olan dengesizliklerin azaltılmasında nispeten etkili bir mekanizma gibi görünmektedir. ENGLISH TITLE & ABSTRACTTurkish Immigration to the European Union: The Case of GermanyThe objective of the paper was to evaluate the relationships between immigration from Turkey and economic indicators in Germany using  quantitative methods. Despite Turkey’s unclear European integration prospects, it is predicted that Turkish immigration to  established member countries of the EU will continue. The strongest waves may flow to Germany, Netherlands or France, where numerous Turkish minorities are already present and where the living standards are high. Results from the statistical analysis of the paper showed a positive correlation between immigration total and the growth of gross domestic product. On the other hand, a negative correlation of immigration total and unemployment was found and a positive relationship between immigration total and income total which is in agreement with the expected dependency direction. With regards to  immigration from Turkey it is less correlated to unemployment than immigration total. But there is a correlation between immigration from Turkey and the stock of foreigners in Germany This is in accordance with the theoretical concept of network theory where an existing community of migrants keeps attracting new migrants because the costs and risks associated with migration are lower, thanks to established linkages to the country of origin. The observed correlation of migration and unemployment points to the fact that immigration to Germany responds to changes in demand in the labour market. Even though a time lag may occur in the case of unemployment and immigration, migration appears to be a relatively effective mechanism to offset existing imbalances in German labour markets. 


2017 ◽  
Vol 23 (2) ◽  
pp. 100-121
Author(s):  
Michel Chambon

This article explores the ways in which Christians are building churches in contemporary Nanping, China. At first glance, their architectural style appears simply neo-Gothic, but these buildings indeed enact a rich web of significances that acts upon local Christians and beyond. Building on Actor-Network Theory and exploring the multiple ties in which they are embedded, I argue that these buildings are agents acting in their own right, which take an active part in the process of making the presence of the Christian God tangible.


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