Role of ambient pressure in keyhole dynamics based on beam transmission path method for laser welding on Al alloy

2018 ◽  
Vol 99 (5-8) ◽  
pp. 1639-1651 ◽  
Author(s):  
Xiaoxiao Han ◽  
Xinhua Tang ◽  
Tiange Wang ◽  
Chendong Shao ◽  
Fenggui Lu ◽  
...  
Keyword(s):  
Laser Welding ◽  
Ambient Pressure ◽  
Al Alloy ◽  
Transmission Path ◽  
Keyhole Dynamics ◽  
Beam Transmission

Role of Stress in the Stress Corrosion Cracking of a Mg-Al Alloy

CORROSION ◽  
1973 ◽  
Vol 29 (6) ◽  
pp. 251-260 ◽  
Author(s):  
W. R. WEARMOUTH ◽  
G. P DEAN ◽  
R. N. PARKINS
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Al Alloy

scholarly journals The history effect in bubble growth and dissolution. Part 1. Theory

2016 ◽  
Vol 800 ◽  
pp. 180-212 ◽  
Author(s):  
Pablo Peñas-López ◽  
Miguel A. Parrales ◽  
Javier Rodríguez-Rodríguez ◽  
Devaraj van der Meer
Keyword(s):  
Bubble Dynamics ◽  
Ambient Pressure ◽  
Time History ◽  
Interfacial Concentration ◽  
Interface Concentration ◽  
Governing Differential Equation ◽  
History Of ◽  
History Effect ◽  
Isothermal Regime

The term ‘history effect’ refers to the contribution of any past mass transfer events between a gas bubble and its liquid surroundings towards the current diffusion-driven growth or dissolution dynamics of that same bubble. The history effect arises from the (non-instantaneous) development of the dissolved gas concentration boundary layer in the liquid in response to changes in the concentration at the bubble interface caused, for instance, by variations of the ambient pressure in time. Essentially, the history effect amounts to the acknowledgement that at any given time the mass flux across the bubble is conditioned by the preceding time history of the concentration at the bubble boundary. Considering the canonical problem of an isolated spherical bubble at rest, we show that the contribution of the history effect in the current interfacial concentration gradient is fully contained within a memory integral of the interface concentration. Retaining this integral term, we formulate a governing differential equation for the bubble dynamics, analogous to the well-known Epstein–Plesset solution. Our equation does not make use of the quasi-static radius approximation. An analytical solution is presented for the case of multiple step-like jumps in pressure. The nature and relevance of the history effect is then assessed through illustrative examples. Finally, we investigate the role of the history effect in rectified diffusion for a bubble that pulsates under harmonic pressure forcing in the non-inertial, isothermal regime.

scholarly journals Effect of inert agents on the flammability parameters of selected gases and organic liquid vapours

2019 ◽  
pp. 108-114
Author(s):  
Paulina Flasińska
Keyword(s):  
Ambient Pressure ◽  
Organic Liquid ◽  
Explosion Hazard ◽  
European Standard ◽  
Flammability Limits ◽  
Open Spaces ◽  
Limiting Oxygen Concentration ◽  
Selection Of ◽  
Safe Working

Flammable substances may form explosive atmospheres when mixed with air. To prevent their formation or minimise the risk of their occurrence, it is necessary to understand the properties of the mixtures of flammable substances and to apprehend the properties characterising the course of a potential explosion. To minimise the risk of a fire or an explosion, a process called inerting is used in which, e.g. nitrogen plays the role of an inert agent. The article discusses the method for testing the flammability limits, the “bomb” method, in accordance with the European standard PN-EN 1839 and the limiting oxygen concentration (LOC) according to the European standard PN-EN 14756. The study shows the influence of inert gas on the flammability range of selected substances: hydrogen, methane, and hexane, which in practice allows the assessment of the explosion hazard of closed and open spaces, the establishment of safe working conditions, and the selection of equipment operating in given explosion hazard zones. The tests were carried out at 25 °C for hydrogen and methane and at 40 °C for hexane, at ambient pressure.

scholarly journals Molecular-scale investigation of the oxidation behavior of chromia-forming alloys in high-temperature CO2

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Richard P. Oleksak ◽  
Rafik Addou ◽  
Bharat Gwalani ◽  
John P. Baltrus ◽  
Tao Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Power Systems ◽  
High Purity ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
Critical Role ◽  
Atomic Scale ◽  
Atomic Diffusion ◽  
Carbon Transport

AbstractCurrent and future power systems require chromia-forming alloys compatible with high-temperature CO2. Important questions concerning the mechanisms of oxidation and carburization remain unanswered. Herein we shed light onto these processes by studying the very initial stages of oxidation of Fe22Cr and Fe22Ni22Cr model alloys. Ambient-pressure X-ray photoelectron spectroscopy enabled in situ analysis of the oxidizing surface under 1 mbar of flowing CO2 at temperatures up to 530 °C, while postexposure analyses revealed the structure and composition of the oxidized surface at the near-atomic scale. We found that gas purity played a critical role in the kinetics of the reaction, where high purity CO2 promoted the deposition of carbon and the selective oxidation of Cr. In contrast, no carbon deposition occurred in low purity CO2 and Fe oxidation ensued, thus highlighting the critical role of impurities in defining the early oxidation pathway of the alloy. The Cr-rich oxide formed on Fe22Cr in high purity CO2 was both thicker and more permeable to carbon compared to that formed on Fe22Ni22Cr, where carbon transport appeared to occur by atomic diffusion through the oxide. Alternatively, the Fe-rich oxide formed in low purity CO2 suggested carbon transport by molecular CO2.

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