A Quantified Study of the Resistance of Duplex Stainless Steels to HISC: Part 2 - Significance of the hydrogen permeation properties and severity of stress raisers, on hydrogen transport and cracking

The quantified microstructural analysis carried out on a wrought and a hot isostatically-pressed (HIP) UNS S31803 duplex stainless steel (DSS) in the Part 1 publication of this study 1, established the significance of the three-dimensional (3D) distribution and morphology/geometry of the ferrite and austenite phases on hydrogen transport through two DSS product forms. This paper is a follow-on to Part 1, and focuses on the role of the other two key, interrelated components of hydrogen-induced stress cracking (HISC): stress/strain, and hydrogen. For this purpose, experimental hydrogen permeation measurements, and environmental fracture toughness testing (i.e. J R-curve testing) using conventional and non-standard single-edge notched bend test specimens were used. These particularly enabled interpretation of the hydrogen permeation and transport test data, and evaluation of suitability of environmental fracture toughness test methods for the assessment of resistance to HISC in DSSs. The latter is discussed, both from laboratory and component integrity perspectives, in the context of the findings from the 3D microstructural characterisation of the two phases, the role of stress raisers and their severity, and hydrogen transport through the bulk and from the surface.

Minimum design metal temperature of Q345R determined by exemption curve in ASME VIII-2 and its derived methods

In order to prevent the brittle fracture accident, minimum design metal temperature of ferrite steel should be limited. After the minimum design metal temperature curve in American Society of Mechanical Engineers VIII-2 (2007) was proposed, much related research has been done in recent years. In this paper, firstly the theoretical basis of four methods used to determine the minimum design metal temperature was introduced. Secondly, the mechanical properties of Q345R was measured by tensile test, Charpy v-notch impact test and fracture toughness test Thirdly, minimum design metal temperature curve of Q345R that determined by four methods were obtained. There are obvious difference between the curves of Q345R that determined by four methods. It can be concluded that low temperature fracture toughness of Q345R is underestimated when classifying Q345R into exemption curve A in American Society of Mechanical Engineers VIII-2 (2007).

The Effect of Loading Rate on Fracture Toughness of Concrete using Type I Fracture Toughness Test Flattened Brazilian Disc (FBD) Mode

Mining activities in open pit and underground mines will always be associated with rock breaking or stripping activities (both mechanical and blasting), so that this can affect the structure and strength of rocks. The strength of the rock is strongly influenced by the presence of initial cracks (pre-existing cracks) and rock anisotropy conditions associated with discontinuous plane conditions. Fracture mechanics is a science that illustrates how a fracture can occur and propagate during applied stress on material. The main parameter in fracture mechanics is called fracture toughness which shows the resistance of the material to propagate the crack. There are several mode in determining type I fracture toughness, one of which is type I fracture toughness Flattened Brazilian Disc (FBD) mode. Type I fracture toughness test is carried out using a compression machine in a laboratory and is conducted on concrete samples consisting of 3 (three) various samples, with a ratio of cement and sand composition of 1:1, 1:2, and 2:1. This test also uses different loading rate values, namely 2.50 mm/min, 2.70 mm/min, and 2.83 mm/min. The results of the type I fracture toughness value from each loading rate will be compared to determine the effect of the loading rate on the value of type I fracture toughness. The obtained fracture toughness value is also related to the physical and mechanical properties of the samples. Based on the results of tests, it can be seen that the loading rate affects the value of fracture toughness, the increase in fracture toughness value is followed by the higher loading rate. In addition, it can be seen that the fracture toughness value is directly proportional to the uniaxial compressive strength value and the indirect tensile strength value. The average correlation value obtained is R2 = 0.9884 (indicating a strong relationship).

The Structuring and Empowerment Policy of Losari Beach Street Vendors Based on The Concept of Smart City

Mining activities in open pit and underground mines will always be associated with rock breaking or stripping activities (both mechanical and blasting), so that this can affect the structure and strength of rocks. The strength of the rock is strongly influenced by the presence of initial cracks (pre-existing cracks) and rock anisotropy conditions associated with discontinuous plane conditions. Fracture mechanics is a science that illustrates how a fracture can occur and propagate during applied stress on material. The main parameter in fracture mechanics is called fracture toughness which shows the resistance of the material to propagate the crack. There are several mode in determining type I fracture toughness, one of which is type I fracture toughness Flattened Brazilian Disc (FBD) mode. Type I fracture toughness test is carried out using a compression machine in a laboratory and is conducted on concrete samples consisting of 3 (three) various samples, with a ratio of cement and sand composition of 1:1, 1:2, and 2:1. This test also uses different loading rate values, namely 2.50 mm/min, 2.70 mm/min, and 2.83 mm/min. The results of the type I fracture toughness value from each loading rate will be compared to determine the effect of the loading rate on the value of type I fracture toughness. The obtained fracture toughness value is also related to the physical and mechanical properties of the samples. Based on the results of tests, it can be seen that the loading rate affects the value of fracture toughness, the increase in fracture toughness value is followed by the higher loading rate. In addition, it can be seen that the fracture toughness value is directly proportional to the uniaxial compressive strength value and the indirect tensile strength value. The average correlation value obtained is R2 = 0.9884 (indicating a strong relationship).

Design of Groundwater Sustain Irrigation Network System in Panca Lautang Area, Sidrap Regency, South Sulawesi

Mining activities in open pit and underground mines will always be associated with rock breaking or stripping activities (both mechanical and blasting), so that this can affect the structure and strength of rocks. The strength of the rock is strongly influenced by the presence of initial cracks (pre-existing cracks) and rock anisotropy conditions associated with discontinuous plane conditions. Fracture mechanics is a science that illustrates how a fracture can occur and propagate during applied stress on material. The main parameter in fracture mechanics is called fracture toughness which shows the resistance of the material to propagate the crack. There are several mode in determining type I fracture toughness, one of which is type I fracture toughness Flattened Brazilian Disc (FBD) mode. Type I fracture toughness test is carried out using a compression machine in a laboratory and is conducted on concrete samples consisting of 3 (three) various samples, with a ratio of cement and sand composition of 1:1, 1:2, and 2:1. This test also uses different loading rate values, namely 2.50 mm/min, 2.70 mm/min, and 2.83 mm/min. The results of the type I fracture toughness value from each loading rate will be compared to determine the effect of the loading rate on the value of type I fracture toughness. The obtained fracture toughness value is also related to the physical and mechanical properties of the samples. Based on the results of tests, it can be seen that the loading rate affects the value of fracture toughness, the increase in fracture toughness value is followed by the higher loading rate. In addition, it can be seen that the fracture toughness value is directly proportional to the uniaxial compressive strength value and the indirect tensile strength value. The average correlation value obtained is R2 = 0.9884 (indicating a strong relationship).

Electrical Conductivity of Glass Fiber-Reinforced Plastic with Nanomodified Matrix for Damage Diagnostic

The electrical conductivity of glass fiber-reinforced plastic (GFRP) with epoxy matrix modified by multiwall carbon nanotubes (MWCNT) was studied. The electrical conductivity of nanomodified lamina and multi-layered GFRP was investigated on several levels using a structural approach. Components of the electrical conductivity tensor for unidirectional-reinforced monolayer were calculated similarly as in micromechanics using the conductivity of the nanomodified matrix. The electrical conductivity of multilayer composite was calculated using laminate theory and compared with values measured experimentally for various fiber orientation angles. Calculated and experimental data were in good agreement. The voltage distribution measured throughout the laminate allowed detecting the damage in its volume. The electrode network located on the laminate surface could determine the location, quantification, and geometry of the damage in the GFRP lamina modified with MWCNT. Experimental and calculated electrical resistance data for GFRP double-cantilever beam specimens were investigated in Mode I interlaminar fracture toughness test. Results demonstrate that electrical resistance could be successfully used for the diagnostic of the crack propagation during interlaminar fracture of the MWCNT-modified GFRP.

Assessing Fracture Toughness and Impact Strength of PMMA Reinforced with Nano-Particles and Fibre as Advanced Denture Base Materials

Statement of Problem: Polymethyl methacrylate (PMMA) denture resins commonly fracture as a result of the denture being dropped or when in use due to heavy occlusal forces. Purpose: To investigate the effects of E-glass fibre, ZrO2 and TiO2 nanoparticles at different concentrations on the fracture toughness and impact strength of PMMA denture base. Materials and Methods: To evaluate fracture toughness (dimensions: 40 × 8 × 4 mm3; n = 10/group) and impact strength (dimensions: 80 × 10 × 4 mm3; n = 12/group), 286 rectangular tested specimens were prepared and divided into four groups. Group C consisted of the PMMA specimens without any filler (control group), while the specimens in the remaining three groups varied according to the concentration of three filler materials by weight of PMMA resin: 1.5%, 3%, 5%, and 7%. Three-point bending and Charpy impact tests were conducted to measure the fracture toughness and impact strength respectively. Scanning Electron Microscope (SEM) was utilised to examine the fractured surfaces of the specimens after the fracture toughness test. One-way analysis of variance (ANOVA) followed by Tukey post-hoc tests were employed to analyse the results at a p ≤ 0.05 significance level. Results: Fracture toughness of groups with 1.5 and 3 wt.% ZrO2, 1.5 wt.% TiO2, and all E-glass fibre concentrations were significantly higher (p < 0.05) than the control group. The samples reinforced with 3 wt.% ZrO2 exhibited the highest fracture toughness. Those reinforced with a 3 wt.%, 5 wt.%, and 7 wt.% of E-glass fibres had a significantly (p < 0.05) higher impact strength than the specimens in the control group. The heat-cured PMMA modified with either ZrO2 or TiO2 nanoparticles did not exhibit a statistically significant difference in impact strength (p > 0.05) in comparison to the control group. Conclusions: 1.5 wt.%, 3 wt.% of ZrO2; 1.5 wt.% ratios of TiO2; and 1.5 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% of E-glass fibre can effectively enhance the fracture toughness of PMMA. The inclusion of E-glass fibres does significantly improve impact strength, while ZrO2 or TiO2 nanoparticles did not.

Effect of Plastic Constraint and Cladding on Semi-Elliptical Shaped Crack in Fracture Toughness Evaluation for a Reactor Pressure Vessel Steel

In the structural integrity assessment of a reactor pressure vessel (RPV), the fracture toughness (KJc) should be higher than the stress intensity factor at the crack tip of a semi-elliptical shaped under-clad crack (UCC), which is prescribed in JEAC4206-2016. However, differences in crack depth and existence of cladding between the postulated crack and fracture toughness test specimens would be affected to the plastic constraint state and KJc evaluation. In this study, we performed fracture toughness tests and finite element analyses to investigate the effect of plastic constraint and cladding on the semi-elliptical shaped crack in KJc evaluation. The apparent KJc value evaluated at the deepest point of the crack exceeded 5% fracture probability based on the Master Curve method estimated from C(T) specimens, and the conservativeness of the current integrity assessment method was confirmed. Few initiation sites were observed along the tip of semi-elliptical shaped crack other than the deepest point. The plastic constraint state was also analyzed along the crack tip, and it was found that the plastic constraint at the crack tip near the surface was lower than that for the deepest point. Moreover, it was quantitatively showed that the UCC decreased the plastic constraint. The local approach suggested higher KJc value for the UCC than that for the surface crack, reflecting the low constraint effect for the UCC.