Inside Radius Research Articles

Yielding onset in FGM thick-walled spherical shells under thermo-mechanical loading

Based on von Mises yield criterion, a thermoelasto-plastic analysis of a thick-walled spherical shell composed of functionally graded material (FGM) subjected to internal pressure and thermal gradient is conducted in order to accurately predict the onset radius of yielding within the vessel wall. The modulus of elasticity, thermal conductivity and thermal expansion coefficients, and yield stress of FGM are assumed to follow power-law functions in radius according to Erdogan’s model. The equilibrium differential equation of the shell under thermo-mechanical loading in steady-state conduction heat transfer are derived analytically and then solved to determine through-thickness variations of the radial and circumferential stresses and radial displacement in elastic and perfectly plastic zones in the vessel wall. The presented approach leads to the definition of new formulation to predict the onset radius of yielding. Moreover, a neural network (NN) solution to reliable quantify the influence of all uncertain input parameters with respect to uncertain output parameter is utilized. The numerical results showed that for various FGM parameters and specific thermal gradient, the plastic zone can commence from inside radius, outside radius, simultaneously in both radii, or may be launched in the intermediate radius of the spherical shell wall.

High strength steel unlipped channel sections subjected to ETF loading: Laboratory testing, numerical simulations and web crippling design

This paper presents web crippling and structural design of high strength steel unlipped channel sections under end-two-flange (ETF) loading based on experimental and finite element investigations. The experimental programme was composed of six grade S690 and four grade S960 test specimens, and the corresponding test set-up, procedures and results were reported in detail. The web crippling test results were used in the numerical modelling programme to validate the developed FE models, which were then adopted to perform parametric studies to enlarge parameter ranges of the bearing length, web slenderness and inside bend radius. Given that codified design rules for S690 and S960 high strength steel unlipped channel sections undergoing web crippling are absent, the corresponding normal strength steel design provisions, as stipulated in the European code EN 1993-1-3 and American specification AISI S100, were evaluated for their suitability to high strength steel unlipped channel sections. It is shown that the ultimate strength of high strength steel unlipped channel sections nonlinearly increases with increasing bearing length but with decreasing web slenderness and inside bend radius. The design methods of current EN 1993-1-3 and AISI S100 provide inaccurate and scattered resistance predictions for high strength steel unlipped channel sections. Finally, a modified AISI S100 design method and a slenderness-based design method were proposed, which can outperform the codified design methods.

Tests, simulations and web crippling design of S690 and S960 high strength steel unlipped channel sections under end-one-flange loading

This paper presents experimental and numerical investigations into the web crippling behaviour and structural design of high strength steel unlipped channel sections under end-one-flange loading. An experimental programme including six grade S690 and four grade S960 steel test specimens was firstly carried out, and the corresponding test set-up, procedures and results were reported. The web crippling test results were subsequently used in a finite element programme to validate developed finite element models, which were then adopted to perform parametric studies to cover wider parameter ranges of the bearing length, web slenderness and inside bend radius. It is found that the ultimate web crippling strength of high strength steel unlipped channel sections increases with increasing bearing length but decreasing web slenderness and inside bend radius. Considering that relevant codified design provisions are absent, the design rules of normal strength steel unlipped channel sections, as prescribed in EN 1993-1-3, EN 1993-1-5 and AISI S100, were assessed for their suitability to high strength steel unlipped channel sections. The codified design methods provide inaccurate and scattered resistance predictions for high strength steel unlipped channel sections under end-one-flange loading. Thus, an improved AISI S100 design method and a novel slenderness-based design method were proposed, which can outperform the codified design methods.

Effects of Lip Length and Inside Radius-to-Thickness Ratio on Buckling Behavior of Cold-Formed Steel C-Sections

Cold-formed steel (CFS) sections constructed with high-strength steel have gained prominence in construction owing to their advantages, including a high strength-to-weight ratio, shape flexibility, availability in long spans, portability, cost-effectiveness, and design versatility. However, the thin thickness of CFS members makes them susceptible to various forms of buckling. This study focuses on addressing and mitigating different types of buckling in columns and beams by manipulating the lip length (d) and the ratio of inside radius to thickness (Ri/t) in CFS C-sections. To achieve this objective, a comprehensive analysis involving 176 models was conducted through the Finite Element Method (FEM). The findings reveal that an increase in lip length leads to a corresponding increase in critical elastic buckling load and moment (Pcrl, Pcrd, Pcre, Mcrl, Mcrd, and Mcre). It is recommended to utilize a lip length greater than or equal to 15 mm for both columns and beams to mitigate various buckling types effectively. Conversely, an increase in the ratio of inside radius to thickness (Ri/t) results in an increase in critical elastic local buckling load (Pcrl) and moment (Mcrl). Thus, lip length (d) significantly influences column and beam buckling, whereas Ri/t exhibits a relatively impactful effect. Subsequently, the experimental test results were used to verify finite element models. These insights contribute significant knowledge for optimizing the design and performance of CFS C-sections in structural applications.

Multi-stream radial structure of cold dark matter haloes from particle trajectories: deep inside splashback radius

Abstract By tracking trajectories of dark matter (DM) particles accreting onto haloes in cosmological N-body simulations, we investigate the radial phase-space distribution of cold dark matter (CDM) haloes, paying attention to their inner regions deep inside the halo boundary called the splashback radius, where the particles undergo multi-stream flows. Improving the analysis by Sugiura et al., we classify DM particles by the number of apocenter passages, p, and count it up to p = 40 for each halo over a wide mass range. Quantifying the radial density profile for particles having the same value of p, we find that it generally exhibits a double-power law feature, whose indices of inner and outer slopes are well-described by −1 and −8, respectively. Its characteristic scale and density are given as a simple fitting function of p, with a weak halo mass dependence. Interestingly, summing up these double-power law profiles beyond p = 40 reproduces well the total density profile of simulated haloes. The double-power law nature is persistent and generic not only in mass-selected haloes but also in haloes selected in different criteria. Our results are compared with self-similar solutions that describe the stationary and spherical accretion of DM. We find that even when introducing a non-zero angular momentum, none of them explain the radial multi-stream structure. The analysis with particle trajectories tracing back to higher redshifts suggests that the double-power law nature has been established during an early accretion phase and remains stable.

Experimental investigation on cold-formed Z-sections under two-flange loadings

This article presents the updated web crippling coefficients of cold-formed Z-sections under two-flange loading conditions. AISI Specification defines end-two-flange (ETF) and interior-two-flange (ITF) load cases under two-flange loading conditions. The web crippling capacity can be calculated by the empirical equation provided by AISI, Eurocode, and IS Specifications. This empirical equation is associated with web crippling coefficients. This coefficient is not updated for the Z-section under two-flange loadings after the development of the AISI test standard for web crippling investigations. Hence, the authors conducted an experimental investigation of cold-formed Z-sections using 28 tests under ETF and ITF load cases. The experimental investigation is carried out according to AISI guidelines. The result of the experimental work is validated with finite element analysis (FEA) results. The web crippling capacity obtained from experimentation and FEA are compared with AISI, Eurocode, and IS Specifications. It is observed that web crippling strength prediction from cold-formed specifications is over-conservative under both ETF and ITF load cases. This research also highlighted the effect of higher web height to thickness and inside bend radius to thickness ratio. Hence, the authors suggested new web crippling coefficients that can better predict the web crippling capacity of Z-sections according to the AISI Specification.

Investigation of cold work effect, Karren (AISI) and ECCS (Euro Code3) equations validity and tension failure modes in thick plate cold-formed steel angle sections

In this study, tensile behavior of thick cold-formed steel angles with the thickness ranges from 2 to 15 mm was investigated experimentally. For the comparison purposes, corresponding steel strips were also tested and the yield stress, ultimate strength and over-strength factor, and tension failure modes of the two sets of specimens were compared. In order to verify the accuracy of Karren equation in predication of the average yield stress of the studied thick cold-formed steel angles, the results of experimental study was compared with that of this equation. The Karren equation was expanded to account for the effects of virgin plate ductility and inside bend radius of cold-formed steel angle section in determination of the over-strength factor and accordingly, practical design curves were proposed. ECCS(Euro Code3) formula was discussed and in order to evaluation of its accuracy, its calculated results were compared with the test results and Karren(AISI) equation calculated results, tension failure modes of the cold-formed and hot rolled angles and their tension stress distribution caused of cold work effect was studied.

Generation of Electricity From a Hydraulic Turbine in the Djonou River (Benin)

The shortage of electricity in rural areas despite the hydraulic potential they possess is becoming a challenge for Benin. To date, nearly 140,000 people spread over the 42 lakeside villages of this country live in energy inaccessibility, insecurity and poverty. To overcome this situation, the present study is therefore interested in the production of electrical energy on an experimental basis in low water periods thanks to an Archimedean screw turbine which operates at low flow rates and height of fall on the river. Djonou located in southern Benin a few kilometers from the University of Abomey-Calavi. The geometrical and hydraulic parameters of the screw were therefore determined and the device was modeled using Autocard software. A prototype was then made with local recycled materials and tested on the river. The screw specifications indicate an inside and outside radius of 0.072 m and 0.135 m. The length of the screw was set at 0.46 m for a blade radius estimated at 0.137 m. The number of screw blades is equal to 2 with a flow rate of 0.049 $ m^{3}/s $. The inclination angle of the screw is $25^{\circ}$. The device on the experimental site produces a voltage of 16 V and provides a current of about 0.12 A which can power a 2 W lamp. This performance of the prototype made on a small scale is a reliable indicator of the optimal use of this technology in the national hydraulic network of Benin to supply populations with electrical energy.

Dynamic investigation and alleviative measures for the skidding phenomenon of lubricated rolling bearing under light load

The skidding phenomenon occurs during the operation of rolling bearing under the light load owing to the design error, which will intensify the surface damage and lead to noise and abnormal vibration. In this study, a skidding dynamics model of lubricated rolling bearing is established considering the interactions between the roller and races, as well as the cage. The effect of lubricant on the dynamic characteristics of the rolling bearing is characterized as the lubricating oil stiffness, central film thickness, time-varying friction coefficient between the roller and race, passing flow resistances of rollers, and resistance torques. In addition, the nonlinear contact and structure deformations of rollers are formulated. For mitigating the skidding phenomenon of the roller under light load, the effect of roller number, inside radius of the hollow roller, density and viscosity of the lubricant, interference fit, and radial load are analyzed. The results indicate that the skidding phenomenon of the roller is induced by the lesser tangential roller-race friction forces and larger passing flow resistances of rollers. It is helpful to intensify the interactions at the roller-race interface or/and decrease the running resistance by reducing the roller number, decreasing the lubricant density, or choosing the correct viscosity of the lubricant. Besides, the effect of interference fit and increasing radial load is significant on the premise of not changing the design parameters of the rolling bearing.

Numerical investigation of inside peak particle velocities for predicting the vibration influence radius of vibratory pile driving

The vibration influence radius of vibratory pile driving is commonly predicted by the peak particle velocity (PPV) at the ground surface rather than inside the soil. In this paper, a vibratory penetration model is established in FLAC3D to investigate both surface and inside PPVs. The computation time of the model is significantly decreased by a density scaling method. The surface PPV attenuation in simulation shows a good agreement with a field test. When the distance from the pile axis is identical, the maximum PPV is inside the soil rather than at the ground surface. Then, the PPV at all points are illustrated as an isoline map, where the inside vibration influence radius is larger than that of surface. Additionally, the inside influence radius is still bigger as two construction parameters (the centrifugal force and the static force) change. The centrifugal force can slightly increase the inside influence radius and the static force has little effect on the radius. This work could advance vibration measurements for predicting the influence radius of vibratory pile driving.

Analytical methods for the efficiency of annular fins with rectangular and hyperbolic profiles under partially wet surface conditions

In this study, we analytically investigate the performances of annular fins with rectangular and hyperbolic profiles under partially wet conditions. We propose four equations for the profiles of enthalpy difference, four equations for heat transfer rates, and four equations for fin efficiency which is a function of interface radius. We then present four equations for evaluating interface radius. Results indicate that the heat transfer rate and efficiency of an annular fin with a rectangular profile is higher than that with a hyperbolic profile. The efficiency under partially wet conditions is between those under fully dry and fully wet conditions. The efficiency of fully dry fins is independent of relative humidity; however, for fully wet and partially wet conditions, efficiencies increase with decreasing relative humidity. At the same relative humidity, heat transfer rate increases with an increasing ratio of outside radius to inside radius. In contrast, fin efficiency decreases. Highlights By analytical method, the partially wet annular fin performances are investigated. Partially wet fin efficiency of annular fin of rectangular profile is presented. Partially wet fin efficiency of annular fin of hyperbolic profile is presented.

Finite Pure Plane Strain Bending of Inhomogeneous Anisotropic Sheets

The present paper concerns the general solution for finite plane strain pure bending of incompressible, orthotropic sheets. In contrast to available solutions, the new solution is valid for inhomogeneous distributions of plastic properties. The solution is semi-analytic. A numerical treatment is only necessary for solving transcendent equations and evaluating ordinary integrals. The solution’s starting point is a transformation between Eulerian and Lagrangian coordinates that is valid for a wide class of constitutive equations. The symmetric distribution relative to the center line of the sheet is separately treated where it is advantageous. It is shown that this type of symmetry simplifies the solution. Hill’s quadratic yield criterion is adopted. Both elastic/plastic and rigid/plastic solutions are derived. Elastic unloading is also considered, and it is shown that reverse plastic yielding occurs at a relatively large inside radius. An illustrative example uses real experimental data. The distribution of plastic properties is symmetric in this example. It is shown that the difference between the elastic/plastic and rigid/plastic solutions is negligible, except at the very beginning of the process. However, the rigid/plastic solution is much simpler and, therefore, can be recommended for practical use at large strains, including calculating the residual stresses.

Tensile behavior of clayey soils during desiccation cracking process

Desiccation cracking is a common phenomenon on Earth's surface. It is a typical form of soils' tensile failure caused by drying-induced tensile stress. Understanding soil tensile behavior during the drying process is of great significance for revealing the soil desiccation cracking mechanism. In this investigation, fiber Bragg grating (FBG) technique was employed to develop a new restrained ring, which is able to continuously monitor the evolution characteristics of soil tensile strain as well as tensile stress during the desiccation cracking process. Desiccation tests were carried out on two clayey soils (a lean clay and a fat clay). Saturated slurry samples (inside radius of 25 mm, outside radius of 75 mm and height of 30 mm) were prepared with initial water contents of 58.1% for the tested lean clay and 106.6% the tested fat clay, and were subjected to continuous drying under constant environmental condition (25 ± 1 °C of room temperature, 50 ± 5% of relative humidity). Moreover, a camera was mounted above the soil sample to capture the surface changes as well as the initiation and propagation of desiccation cracks. The results show that the developed FBG-based restrained ring can effectively identify the tensile behavior of the soil during the desiccation cracking process. Both the evolution of tensile stress and graphic variation show three typical periodic features that are well matched with soil vertical deformation, lateral shrinkage and cracking. With decreasing water content, tensile stress gradually increases at first and then increases more rapidly. Once the tensile stress reaches the peak value, desiccation cracks initiate and a sudden reduction in tensile stress is observed. Finally, the tensile stress reaches a residual stage. We consider the maximal tensile stress during the drying process to correspond to the tensile strength of the tested material. It is found that clay content has a significant influence on the cracking tensile strength of soils. The fat clay with a higher clay content shows a larger cracking tensile strength (about 410 kPa) compared with the lean clay (about 90 kPa).

Probability study of airplane crash on Kartini Reactor site area

Abstract. Probability study of airplane crash at Kartini Reactor site has been carried out. Objective of this study is to determine probability of airplane crash coming from airports around Kartini Reactor site to Kartini Reactor Site. This study was carried out in several stages, namely identification of airports around Kartini Reactor site, initial screening using SDV values (10 km for small airport and 16 km for large airport), probability calculation of airplane crash at Kartini Reactor site and comparing the calculation result with applicable regulations. Based on the identification results there are four airports / runways around the Kartini Reactor site, they are Adi Sutjipto Airport, Adi Sumarmo Airport, Depok Runway, and Yogyakarta International Airport where distance from airport to the site between 2.26-48.23 km. After screening using SDV value, that is known only Adi Sutjipto Airport which is inside SDV radius of Kartini Reactor, so that probability of airplane crash from Adi Sutjipto Airport is calculated, i.e. 3,769x10-8 events/year is. This value is still under the provisions in BAPETEN Regulation No. 4 of 2018 i.e. maximum 10-7 events/year. So it can be concluded that Kartini Reactor is safe from the possibility of airplane crash.

Design and development of soft robotic hand for vertical farming in spacecraft

<p>For colonization in deep space we need to explore the feasibility of a bioregenerative system in microgravity or artificial gravity environments. The process has various complexities form ranging to biological obstacles to engineering limitations of the spacecraft. Concentration of microbes in the confinements of a spacecraft can be fatal for the crew. In this paper, a solution to the elevated microbial levels by farming using robots is discussed. The soft robotic arm is made up of Asymmetric Flexible Pneumatic Actuator (AFPA). The AFPA under internal pressure will curve in the direction of the side having greater thickness as the expansion of the thinner side (outside radius) will be more than thicker side (inside radius) due to differential expansion and moment induced due to eccentricity. Simulation results demonstrate that bending based on AFPA can meet the designed requirement of application. The AFPA is used for five fingers of the robotic hand. The safe, soft touch and gentle motion of the bellow (AFPA) gives the feel of real human hand. The internal pressure of the AFPA is controlled using a solenoid valve which is interfaced using an Arduino microcontroller for hand like moves. The bending of the fingers and degree of freedom (DOF) of the joints of the hand is controlled using an IMU and flex sensor. Wireless connection of the hand and the control system is implemented using XBee pro 60mW with a range of 1 miles. The pneumatic soft robotic hand is made up of solenoid valve, Mini Compressor, AFPA bellow, and Servos. This soft robotic hand has many advantages such as good adaptability, simple structure, small size, high flexibility and less energy loss. As an extension Manual control of the robot using a virtual reality environment and well as some possible aspects of an automated farming systems can be considered as future additions.</p>

The evaluation on shock absorption performance of buffer layer around the cross section of tunnel lining

The buffer layer around the cross section of lining structure would be the most simple and effective shock absorption measure, which can cut off the transferring paths of adverse effects from surrounding rock to lining structures. Meanwhile, it can reduce the seismic action intensity and minimize the extra pressure from surrounding rock by changing seismic acting patterns. This paper presents outcomes by investigating the interaction between lining structure and surrounding rock during excitation as well as deriving influencing parameters with regard to shock absorption performances of buffer layer. Afterwards, series numerical calculations are systematically carried out with attention given to the seismic-induced deformation responses of rock-layer-lining system. Finally, an elaborated evaluation method for assessing shock absorption performance of buffer layer with an evaluation expression is proposed, which is validated by series shaking table model tests and numerical simulations. This evaluation expression would be able to guide the selection and construction of buffer layer according to the geological conditions and construction circumstances by changing geometric and material parameters. The evaluation result would have uniqueness once all the parameters are confirmed. From this expression and its derivation process, the following findings can be drawn: (1) The cross section of tunnel has the identical particular deformation pattern in each constructing phase during excitation regardless of the existence of lining structure and buffer layer, that is, the two orthogonal diagonal diameters of cross section alternatively expand and contract. (2) The geometric and material parameters simultaneously determine the shock absorption performances of buffer layer, which grows in direct proportion to geometric variables but decreases in inversely proportion to material variables. (3) When the ratio of lining inside radius to buried depth is equal to 0.2 (i.e. r0/H = 0.2), the buried depth of tunnel engineering should be the ideal position for adopting buffer layer. Meanwhile, when the ratio of buffer layer thickness to lining inside radius is equal to 0.2 (i.e. tb/r0 = 0.2), it can be confirmed the optimal thickness of buffer layer. (4) The evaluation expression of shock absorption performance is independent of seismic waveforms but involved in the excitation intensities and the destruction states of lining structure.

Uticaj Al2O3 nanočestica na toplotne performanse pulsirajuće toplotne cevi zatvorene petlje

With the rapid development of electronic technology, many new promising ideas and technologies were introduced into thermal management, one of which is pulsating heat pipe (PHP), which is different from traditional heat transfer strategy. Hence, an investigation on pulsating heat pipe with multi turns will be conducted in order to examine nanoparticles effect on heat transport ability. The pulsating heat pipe consists of copper tube having inside radius of 1 mm, thickness of 0.5 mm and total length of 1605 mm. The investigation is done with acetone with a filling proportion of 60% for different % mass concentration of 1%, 2%, 3%, 4% and 5% of Al2O3 nanoparticles for differed heat contribution from 20 W to 60 W . From the results of different % mass concentration, the most reduced value of thermal resistance is 0.28 K/W at 1% mass concentration. Hence the PHP operates better with 1% mass concentration of Al2O3 nanoparticles.

Web crippling behaviour and design of aluminium lipped channel sections under two flange loading conditions

Aluminium alloys have recently drawn significant attention in structural applications due to its outstanding mechanical characteristics. Thin-walled members fabricated by aluminium alloys can be more competitive in construction industries than the conventional cold-formed steel sections, particularly in areas with high humidity and severe environmental conditions. Nevertheless, they are more vulnerable to various types of instability due to their relatively low elastic modulus compared to steel. Applying high concentrated load transversely on thin-walled members can cause critical damage to the web of the cross section called web crippling. Although a large number of studies has been performed to investigate the web crippling mechanisms on different types of sections, the existing studies are primarily of the empirical nature and thus merits further investigations. To fill the research gap, this study was thus performed based on our previously conducted experimental work to further comprehend the web crippling phenomenon of the roll-formed aluminium lipped channel (ALC) sections under the loading conditions of end-two-flange (ETF) and interior-two-flange (ITF). This was done through numerical investigations followed by a parametric study which are reported herein in details. A wide range of roll-formed ALC sections covering web slenderness ratios ranged from 28 to 130, inside bent radii ranging between 2 mm and 8 mm, bearing lengths ranged from 50 mm to 150 mm, and three sheeting aluminium alloy grades (5052-H32, 5052-H36 and 5052-H38) were considered in the parametric study. The acquired web crippling database was then used to assess the consistency and accuracy of the current design rules used in practice. It was found that the web crippling capacity determined by the current international specifications are unsafe and unreliable, whereas the predictions of the recently proposed equations agree very well. Furthermore, a Direct Strength Method (DSM)-based capacity prediction approach was proposed and then validated against the web crippling database acquired here as well as the experimental and numerical data for cold-formed steel lipped channel sections used in the literature.

Influence of mould curvature on the metallurgical performances of beam blank continuous casting

ABSTRACT A 3-D finite volume mathematical model was established by customizing pull velocity field function of solidified shell, to simulate the coupled fluid flow, heat transfer, and solidification of beam blank continuous casting, taking into consideration of the effects of mould curvature on the metallurgical performances. When the central impact stream reaches to a certain depth, part of it circulates to scour the solidified shell, causing the remelting of shell at fillet and narrow face centre from about 370 mm down the meniscus to mould exit. The differences of strand surface temperature and shell thickness between inside and outside radius caused by the mould curvature are obvious only at the fillet of the mould exit. The fillet of outside radius having the highest temperature but the thinnest solidified shell is prone to arising quality problems. The metallurgical performances under different casting speed and superheat indicated that the strand surface temperature arises and shell thickness decreases integrally at the mould exit as the casting speed increases. The superheat has the same influence trend as the casting speed does, but the sites it affects are concentrated in the fillet and narrow face centre.

Numerical Modeling and Design of Lipped Channel Beams Subject to Web Crippling under One-Flange Load Cases

Web crippling failure governs the behavior of thin cold-formed steel lipped channel beams (LCBs) used in floor systems. This paper describes a numerical modeling–based research study undertaken to investigate the web crippling behavior of LCBs under one-flange load cases and to develop improved design equations for possible inclusion in the cold-formed steel design standards. Finite-element models were developed to simulate the web crippling behavior of LCBs and their accuracy was verified using 36 web crippling tests of LCBs conducted under one-flange load cases using the new standard test method. A detailed numerical parametric study was then undertaken to investigate the web crippling behavior of LCBs using the verified finite element models of LCBs. This numerical parametric study provided an extensive web crippling capacity database and improved the understanding of the effects of key web crippling parameters such as inside bent radius, bearing length, and yield stress on the web crippling capacity. Using these results, new and improved web crippling design equations were proposed in this paper for LCBs under one-flange load cases. They include both unified web crippling equations and the direct strength method–based equations. This paper demonstrated the improved accuracy of the proposed equations and their potential for inclusion in the cold-formed steel design standards.