This paper presents an in-situ observation, using neutron imaging, of delayed crack propagation in a high-strength martensitic steel specimen. Delayed cracking is believed to be caused by hydrogen embrittlement occurring due to the slow diffusion and accumulation of hydrogen ahead of a crack front, causing decreased ductility and eventual cracking under constant load. The experiment involved mechanical loading of a single-edge-notch bend specimen while submerged in an electrolyte solution (H<inf>2</inf>O + 3.5% NaCl) under cathodic polarization to facilitate hydrogen ingress. Intermittent crack propagation was observed for 12 h after the environment had been removed. The stress state at each crack configuration was extracted from a three-dimensional elastic–plastic finite element simulation, which was tailored to match the quantitative information acquired from the neutron radiographs of the fracture process. To gain insight into the evolution of hydrogen concentration with crack propagation, a modeling scheme for stress-assisted hydrogen diffusion was also employed.

This work presents a systematic investigation of the combined effect of hydrogen embrittlement and loss of constraint. The fracture mechanics experiments are performed on an advanced martensitic high strength steel using a single-edge-notch bend specimen, with different crack over height ratio, subjected to electrochemical in-situ hydrogen charging at various loading rates. It is found that the environmentally driven ductile-to-brittle transition region in fracture toughness is obtained for both the high and low constraint specimen configurations. This region is characterized by a change from transgranular dimple rupture to an intergranular mode of fracture. The transition region for the low constraint specimen is shifted towards longer hydrogen exposure times, which is an effect of the reduced hydrostatic stress ahead of the crack front compared to the high constraint specimen. The low constraint specimen exhibits significant plastic straining, which is reflected in a significant decrease in the fracture toughness due to hydrogen assisted transgranular dimple rupture.

In this work, an experimental-numerical screening method for studying the elastic-plastic properties in high strength steel subjected to environmentally assisted degradation due to hydrogen is proposed. The experiments were performed on single-edge-notch bend specimens loaded with a monotonic constant displacement rate, and the specimens were electrochemically hydrogen pre-charged and/or in-situ. A systematic investigation was conducted of the influence of current density, pre-charging time and loading rate on the fracture mechanical properties. It was found that the loading rate had the greatest effect on the J-R curves, and that the environmental ductile-to-brittle transition region was obtained in a less than a day of experimental time. In this transition region it was found from the fractography that the dominating mode of failure changed from dimple to dominating intergranular fracture.

This paper presents the application of computational fluid dynamics technique in civil and underground industries to evaluate fluid behaviour in a Marsh funnel. The numerical approach, based on computational fluid dynamics, simulated an incompressible two-phase Newtonian flow by means of the Volume-of-Fluid method. A complementary analytical proposed which provided a quick, field-ready method to assess the fluid field in the Marsh funnel. A supplemental experimental effort evaluated the results obtained from both the analytical calculation and numerical simulation. Results showed that the application of computational fluid dynamics technique gives the desired results in studying fluid flows in civil and underground industries. Proposed analytical solution is also capable of accurately predicting the fluid flow and thus can complement the experimental and numerical approaches. Further, the proposed analytical approach can be an alternative method for faster evaluation of fluid, although it needs to be calibrated with either the numerical or the experimental studies.

This work studies multilinear McShane-Stieltjes integrals of vector-valued functions defined on intervals in R^n.

We studied the application of a stratified seasonal hot water storage tank with a heat pump connected to medium-, low- and very-low-temperature space heat emissions for a single-family house in Stockholm, Sweden. Our aim was to investigate the influence of heat emission design temperature on the efficiency and design parameters of seasonal storage in terms of collector area, the ratio of storage volume to collector area (RVA), and the ratio of height to diameter of storage tank. For this purpose, we developed a mathematical model in MATLAB to predict hourly heat demand in the building, heat loss from the storage tank, solar collector heat production, and heat support by heat pump as a backup system when needed. In total, 108 cases were simulated with RVAs that ranged from 2 to 5 (m³ m⁻²), collector areas of 30, 40, and 50 (m²), height-to-diameter-of-storage-tank ratios of 1.0, 1.5, and 2.0 (m m⁻¹), and various heat emissions with design supply/return temperatures of 35/30 as very-low-, 45/35 as low-, and 55/45 (°C) as medium-temperature heat emission. In order to find the best combination based on heat emission, we considered the efficiency of the system in terms of the heat pump work considering coefficient of performance (COP) of the heat pump and solar fraction. Our results showed that, for all types of heat emission a storage-volume-to-collector area ratio of 5 m³ m⁻², with a collector area of 50 m², and a height-to-diameter ratio of 1.0 m m⁻¹ were needed in order to provide the maximum efficiency. Results indicated that for very-low-temperature heat emission the heat pump work was less than half of that of the medium-temperature heat emission. This was due to 7% higher solar fraction and 14% higher COP of heat pump connected to very-low-temperature heat emission compared to medium-temperature heat emission.

In this paper we define and consider multilinear Stieltjes integralsfor vector-valued functions defined on a closed bounded interval in \mathbb{R}^n. Theconvergence of the Stieltjes sums is considered in the Riemann, Moore-Pollardand Henstock-Kurzweil sense.

In this paper we consider the existence of the Henstock-Kurzweil-Stieltjes multilinear integral for the case when the integrands are regulated functions and the integrators semiregulated functions of bounded semivariation.

We prove the existence of the Henstock-Kurzweil-Stieltjes multilinear integral for the case when the integrands are regulated functions and the integrators semiregulated functions of bounded semivariation.

In this note we consider oscillation of regulated functions.

We improve and simplify the proof of the existence theorem for multilinear

Stieltjes integral in the Riemann-Stieltjes and Moore-Pollard sense and

introduce multilinear Henstock-Kurzweil-Stieltjes integral.