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Types of Corrosion in the Offshore Environment
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
The diffusion of the hydrogen into the grain boundaries causes material failure according to two mechanisms and theories; the first is called hydrogen embrittlement local plasticity (HELP) and the second is hydrogen enhancement de-cohesion (HEDC). According to HELP theory, hydrogen atoms are diffused into the void spaces between metal grains and bond together there. The atomic hydrogen causes dislocation in specific metal grains and plastic deformation, which eventually causes a crack in the material. Plastic deformation refers to permanent change in the shape of a material. In HEDC theory, hydrogen enlarges the atoms and molecules, which can then be fractured more easily by the application of stress. According to hydrogen cracking or embrittlement theory, materials with fine grins are at a lower risk of hydrogen attack compared to metals with coarse grains. One proven fact is that the susceptibility of a material to HISC corrosion is higher when the grains are perpendicular to the stress.
Mechanical Behavior of Materials
Published in Snehanshu Pal, Bankim Chandra Ray, Molecular Dynamics Simulation of Nanostructured Materials, 2020
Snehanshu Pal, Bankim Chandra Ray
Materials change their shape due to application of load. This is known as deformation. Elastic deformation is a type of deformation in which the regaining of original shape occurs after removal of the load. Elastic deformation exists in materials either in linear or non-linear manner. In general, metals and ceramics show linear elastic nature, whereas many polymers, gray cast iron, and concrete exhibit non-linear elastic nature. Materials under elastic limit show non-permanent deformation as well as a reversible process. Particularly, during elastic deformation of materials, their shape changes owing to stress application, and shape is regained after stress removal (i.e., only bonds stretching takes place in these deformations). Hooke’s law is valid for materials that exhibit a linear relationship (which means that materials exhibit a deformation rate proportional to load application rate) [1]. Hooke’s law states that stress is directly proportional to strain within the proportional limit. According to Hooke’s law, the relationship between stress and strain is as follows: σ=Eε
Glass Containers for Parenteral Products
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Robert Swift, Robert Schaut, Carol Rea Flynn, Roger Asselta
Similarly, as a material science term, elastic refers to the response of a material to the application and removal of a mechanical load that does not exceed the strength of the material. Elastic materials deform when loaded and then return to the original shape when the load is removed. The stiffness of a material can be characterized by its elastic modulus, also known as Young’s modulus, which is the ratio between the applied unit load, or stress, and the resulting unit deformation, or strain. In this respect, glasses are relatively stiff. Typically, the elastic modulus of glass is about the same as aluminum metal (5). Jiang et al. (90, 91) attached strain gages to the outer surface of glass vials to observe in real time the physical deformations of and corresponding stresses in the vials during freezing, frozen storage, and subsequent rewarming and thawing of various buffers and formulated drug products. Although it was not the objective of the studies, the work demonstrates the elastic deformation of the glass in response to the changing physical dimensions of the contents.
Evaluation of the effects of repeated disinfection on medical exam gloves: Part 2. Changes in mechanical properties
Published in Journal of Occupational and Environmental Hygiene, 2022
Robert N. Phalen, Jonathan Patterson, John Cuadros Olave, Samuel A. Mansfield, Jared S. Shless, Yoshika S. Crider, Helen O. Pitchik, Alliya S. Qazi, Ashley Styczynski, Roger LeMesurier, Daniel Haik, Laura H. Kwong, Christopher LeBoa, Arnab Bhattacharya, Youssef K. Hamidi
Additional considerations for degradation testing include: (1) use of a sensitive and predictive measure of the molecular changes occurring in the polymer; and (2) use of a measure that has lower associated variability. In an evaluation of 37 nitrile exam gloves, Phalen and Wong (2015) found lower overall variability with elastic modulus, compared to tensile strength. The elastic modulus, also referred to as stiffness or Young’s modulus, is a measure of a material’s resistance to elastic deformation. The authors also reported improved correlations between elastic modulus and measures of chemical resistance, as compared to tensile strength and elongation at break. Variability also appears related to glove material. Similarly, Garrido-Molina et al. (2021) observed lower variation with the elastic modulus (∼3%) of a nitrile exam glove, compared to tensile strength (∼6%). Additionally, the results of Gao et al. (2016) exhibited lower overall variation in tensile strength with five different latex glove products (maximum of ∼12%), as compared to eight different nitrile glove products (maximum of ∼38%). Nevertheless, the authors did not report elastic modulus. Based on these results, it is presumed that latex gloves show less variability in tensile test results than nitrile gloves.
Microstructure, mechanical properties and corrosion fatigue behaviour of biodegradable Mg–Zn–Y–Nd alloy prepared by double extrusion
Published in Corrosion Engineering, Science and Technology, 2021
Jinming Wang, Jun Wang, Qinyuan Fu, Kun Sheng, Mengyao Liu, Yufeng Sun, Di Mei, Yage Kou, Shijie Zhu, Shaokang Guan
Tensile tests were conducted on an MTS machine (Bionix 370.2) with a tensile rate of 0.5 mm min−1 at ambient temperature. The dog-bone samples with the gauge length of 20 mm and the diameter of 5 mm were used in the tests (Figure 2). The stress corresponding to 0.2% plastic deformation is taken as the yield strength. After tensile tests, the fractured surfaces were observed using a scanning electron microscope (SEM; FEI Quanta 200). Vickers hardness (HV) tests were performed using a microhardness tester (HXD-1000TMSC/LCD) with a load of 200 g and a dwell time of 10 s. The bulk samples with the length of 10 mm, the width of 8 mm and the height of 8 mm were used in the tests, and the values of HV were shown using the average of ten points randomly selected on the surface of samples.
One-dimensional analytical model for thermo-hydro-mechanical coupling behaviour of hydrates overlying layer during gas production
Published in Marine Georesources & Geotechnology, 2021
Bin Zhu, Songqing Yang, Lujun Wang, Deqiong Kong
Figure 11 shows the influence of F on the variation of compression throughout the 20 production cycles. When pore pressure load applies only, the total soil expansion is nearly zero at the end of 20 cycles (see Figure 11(b)). This phenomenon is mainly due to a fast accumulation and dissipation cycle of EPP (see Figure 8(b,d)). Deformation develops and recovers in an elastic body. However, when thermal load is applied, the overlying layer shows considerable expansive deformation over time (see Figure 11(a)). It shows that temperature load is the dominant factor to determine the expansion of soil layer. In the first 10 cycles (t < 1200 h), the overall expansion of the overlying layer increases with the decrease in F. When F is equals to 0.08, the expansion during the last 10 cycles (t > 1200 h) tends to diminish, and the soil expansion tends to stabilize. With greater permeability, the accumulation rate of thermal-induced pore pressure is close to the dissipation rate so that the expansion rate is somewhat alleviated. To sum up, during the gas production stage, the accumulation rate of EPP in the overlying layer is greater than the dissipation rate. Thus, the EPP accumulation was mainly induced by gas hydrate dissociation, whereas the expansion was mainly caused by the temperature load in the huff-and-puff processes.