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The effect of welding current and polarity, i.e. AC and DCEN, on imposed thermal cycles, mechanical properties, microstructural events and residual stresses was investigated in GTA welding of AA5052. A three-dimensional thermo-mechanical model was utilized to evaluate thermal responses and residual stresses distribution in the weldments. Tensile testing and hardness measurements were also conducted to study the effect of welding polarity on the mechanical properties of components. Microstructural observations utilizing optical microscopy were carried out to assess the microstructural evolutions. The results show that wide varieties of microstructures are produced in DCEN sample from cells at... 

Influence of gas tungsten arc welding on the thermal responses, residual stress distribution and final mechanical properties of the naturally age-hardened (T4) and artificially age-hardened (T6) AA2024 plates was studied. The results showed that age hardening and over-aging occurred in various sections of the heat-affected zone (HAZ) of T4 sample, depending on their locations, while in the HAZ of T6 sample, over-aging is the governing phenomenon. Also, subsequent natural aging occurred in HAZ, weld metal (WM) and partially melted material (PMM) of both weldments. This recent phenomenon is more obvious in the T4 sample in comparison with the T6 one. In both microstructures, weld metal is the... 

In this study, a three-dimensional model has been utilized for predicting thermal responses during tungsten arc welding of AA2024-T4 plates in which double ellipsoidal heat source model was employed to consider the moving torch in the model. Furthermore, tensile and hardness tests and microstructural evaluations have been carried out to investigate the mechanical properties and the microstructures within the welded metal. The results show that there is a region inside the heat-affected zone where hardness increases while in some parts of this region having temperatures higher than 250 C the hardness decreases significantly. Furthermore, natural aging occurs after welding; however, its... 

In logical literature, the phrase 'basic logic' refers to at least three different logical systems. The first one, basic propositional logic, BPL was introduced by Albert Visser in 1981. This logic is a subintuitionistic logic that can be obtained from intuitionistic logic by weakening of modus ponens. The second logical system with the name 'basic logic', is the system B that was introduced by G. Sambin and G. Battilotti in 1997. The goal of this logical system is to provide a common foundation for all usual non-modal logics. The third one is called 'basic logic' by P. Hajek in the field of Fuzzy Logic. We show that the two systems BPL and B do not have a direct relationship (i.e. none of... 

Let A be a subset of the constructive real line. What are the necessary and sufficient conditions for the set A such that A is continuously separated from other reals, i.e., there exists a continuous function f with f -1(0) = A? In this paper, we study the notions of closed sets and closure maps in constructive reverse mathematics  

In the context of intuitionistic analysis, we consider the set F consisting of all continuous functions φ{symbol} from [0, 1] to R such that φ{symbol} (0) = 0 and φ{symbol} (1) = 1, and the set I0 consisting of φ{symbol}'s in F where there exists x ∈ [0, 1] such that φ{symbol} (x) = frac(1, 2). It is well-known that there are weak counterexamples to the intermediate value theorem, and with Brouwer's continuity principle we have I0 ≠ F. However, there exists no satisfying answer to I0¬ ¬ =? F. We try to answer to this question by reducing it to a schema (which we call ED) about intuitionistic decidability that asserts "there exists an intuitionistically enumerable set that is not... 

The schema ED asserts that 'there exists an intuitionistically enumerable subset of N which is not intuitionistically decidable.' In this article, we prove that in the presence of Markov's Principle over Bishop's constructive analysis, ¬ED is equivalent to the principle of open induction on [0,1], via Specker sequences. © 2016. Oxford University Press. All rights reserved  

In classical analysis, every compact subset of ℝ is Lebesgue measurable, but it is not true in constructive analysis. In this paper, we prove that the statement 'every compact set K in a locally compact space X is integrable with respect to a positive measure μ' is equivalent to LPO, over Bishop's constructive analysis. We also prove that the existence of a compact subset of ℝ which is not Lebesgue integrable is equivalent to the schema ED, which asserts that 'there exists an intuitionistically enumerable subset of ℕ which is not intuitionistically decidable'. Moreover, classically, every open subset of ℝ is Lebesgue measurable, but it is not true constructively. We show that Lebesgue... 

In this paper we introduce a modal theory iHσ which is sound and complete for arithmetical Σ1-interpretations in HA, in other words, we will show that iHσ is the Σ1-provability logic of HA. Moreover we will show that iHσ is decidable. As a by-product of these results, we show that HA+□⊥ has de Jongh property. © 2018 Elsevier B.V  

A latarre is a lattice with an arrow. Its axiomatization looks natural. Latarres have a nontrivial theory which permits many constructions of latarres. Latarres appear as an end result of a series of generalizations of better known structures. These include Boolean algebras and Heyting algebras. Latarres need not have a distributive lattice. © 2017, Springer Science+Business Media B.V  

A latarre is a lattice with an arrow. its axiomatization looks natural. Latarres have a nontrivial theory which permits many constructions of latarres. Latarres appear as an end result of a series of generalizations of better known structures. These include Boolean algebras and Heyting algebras. Latarres need not have a distributive lattice. © 2017 Springer Science+Business Media B.V  

For the Heyting Arithmetic HA,HA is defined [14, 15] as the theory {A | HA-A}, where is called the box translation of A (Definition 2.4). We characterize the Σ1-provability logic of HA as a modal theory (Definition 3.17). © 2019 The Association for Symbolic Logic