Search Results (30)

This paper focuses on the behavior of anchor channels in the event of fire. The contribution of this project lies in the necessity coming from the market to study the fire resistance of anchor channels more thoroughly, considering the modes of failure to which they are subjected. The aim of this paper is to transform the method based on tests into a numerical method that allows calculation of the fire resistance at any time under fire conditions, for all fire scenarios (whether it is a standard fire or using performance-based design approaches). A 3D transient thermal model was developed using ANSYS 19.1 to determine the thermal distribution of anchor channels, simulated in uncracked concrete under ISO 834-1 fire conditions. Subsequently, a design model for steel-related failure modes under fire conditions was employed. The model consists of coupling the characteristic resistances of the anchor channel at ambient temperature with temperature-based reduction factors for steel-related failure modes to obtain the calculated fire resistances. The model was compared with fire test results available in the literature, and the comparison yielded satisfactory results, confirming its reliability and accuracy in capturing the relevant phenomena under fire conditions. The results of this research show that the model presents a good candidate to replace the current method of qualification of anchor channels under fire conditions. Full article

This paper concerns measurements and CFD simulations of vacuum-insulated glazing (VIG), which consists of two glass panes separated by a narrow gap from which air has been removed. Distancers, e.g., in the form of small balls, are inserted into this gap every few centimeters to prevent the glass from deflecting. In the first part, simulations of two-pane VIG thermal transmittance with the Ansys Fluent program are described, resulting in thermal transmittance of VIG without the network of distancers equal to 2.18 W/(m²K) and with the distancers equal to 2.29 W/(m²K). The influence of the supports on the thermal transmittance of VIG is also determined. The CFD results show that the supporting balls increase the two-pane VIG thermal transmittance by about 0.15% with respect to the glazing without the distancers. Then, VIG is analyzed both numerically and tested in two measurement stands. Firstly, the tests are performed in a guarded hot-plate apparatus, according to the EN ISO 8302 standard. The two-pane glazing with one low-emissivity coating has a measured thermal transmittance equal to 1.75 W/(m²K). Other measurements were undertaken in the calorimetric chamber equipped with the hot-box apparatus. The results of the numerical assessment are then compared to the measurements of the existing three-pane vacuum-insulated glazing with two low-emissivity coatings, the same as simulated. The procedure follows the EN ISO 8990 standard. Measurement results of 1.10 W/(m²K) are compared to the simulation results of VIG thermal transmittance equal to 1.09 W/(m²K). A satisfactory agreement is reached. Additionally, this paper considers a new correction coefficient to thermal transmittance according to standard EN 673 in order to achieve a proper calculation of vacuum-insulated glazing in the center-of-glass region. The authors propose to use an adjustment coefficient of 1.05 when calculating the thermal transmittance of vacuum-insulated glazing without taking into account convection in the vacuum space and the thermal influence of distancers. Full article

The air attenuation of pure tones as a function of temperature and humidity is well known and described in ISO and ANSI standards. However, room acoustic measurements are performed in octave bands, which is the reason for the complicated, non-linear behavior of the air attenuation. It is known that room acoustic measurement results depend on air temperature and humidity, and these atmospheric data should always be reported in connection with room acoustic measurements. A calculation model for the air attenuation can make it possible to normalize the room acoustic results. For accurate results, it is possible to apply a summation method on each time sample in the impulse response. An approximation to the air attenuation at and above 1 kHz is possible by linearization using the pure-tone attenuation of two different frequencies, one frequency valid for the early part of the impulse response and another frequency valid for the later part of the impulse response. The purpose of the suggested methods is to make it possible to normalize room acoustic measurements to a standard atmosphere. Full article

One of the most basic issues in fluid mechanics is the description of flow in closed flows; more precisely, the calculation of pressure drops and the description of the flow form. Therefore, in this paper, the numerical simulation of the flow through the elbow was presented. This case was used to comprehensively describe the most important phenomena that should be taken into account during closed flows. The elbow was chosen as one of the most frequently used fittings in practice. The simulation was made with ANSYS Fluent, with the use of the turbulent model k-ω, SIMPLE simulation method, and at Reynolds number $Re=500-100,000$. The minor and major pressure loss were presented and discussed in the paper. The minor loss coefficient at the high Reynolds number was equal to around 0.2, which is close to the value of 0.22 used in engineering calculations. The influence of the Reynolds number on the shift of the stream separation point in the elbow was described. The secondary flow in the elbow was observed and the vortex structure was discussed and shown with the use of the Q-criterion (Q iso surface for level 0.005). This analysis allowed us to better visualize and describe the complex flow structure observed in the investigated case. Full article

Inaccuracies from devices for non-invasive blood pressure measurements have been well reported with clinical consequences. International standards, such as ISO 81060-2 and the seminal AAMI/ANSI SP10, define protocols and acceptance criteria for these devices. Prior to applying these standards, a sample size of N >= 85 is mandatory, that is, the number of distinct subcjects used to calculate device inaccuracies. Often, it is not possible to gather such a large sample. Many studies apply these standards with a smaller sample. The objective of the paper is to introduce a methodology that broadens the method first developed by the AAMI Sphygmomanometer Committee for accepting a blood pressure measurement device. We study changes in the acceptance region for various sample sizes using the sampling distribution for proportions and introduce a methodology for estimating the exact probability of the acceptance of a device. This enables the comparison of the accuracies of existing device development techniques even if they were studied with a smaller sample size. The study is useful in assisting BP measurement device manufacturers. To assist clinicians, we present a newly developed “bpAcc” package in R to evaluate acceptance statistics for various sample sizes. Full article

The current study investigated the geometry optimization of a hybrid-driven (based on the combination of air pressure and tendon tension) soft robot for use in robot-assisted intra-bronchial intervention. Soft robots, made from compliant materials, have gained popularity for use in surgical interventions due to their dexterity and safety. The current study aimed to design a catheter-like soft robot with an improved performance by minimizing radial expansion during inflation and increasing the force exerted on targeted tissues through geometry optimization. To do so, a finite element analysis (FEA) was employed to optimize the soft robot’s geometry, considering a multi-objective goal function that incorporated factors such as chamber pressures, tendon tensions, and the cross-sectional area. To accomplish this, a cylindrical soft robot with three air chambers, three tendons, and a central working channel was considered. Then, the dimensions of the soft robot, including the length of the air chambers, the diameter of the air chambers, and the offsets of the air chambers and tendon routes, were optimized to minimize the goal function in an in-plane bending scenario. To accurately simulate the behavior of the soft robot, Ecoflex 00-50 samples were tested based on ISO 7743, and a hyperplastic model was fitted on the compression test data. The FEA simulations were performed using the response surface optimization (RSO) module in ANSYS software, which iteratively explored the design space based on defined objectives and constraints. Using RSO, 45 points of experiments were generated based on the geometrical and loading constraints. During the simulations, tendon force was applied to the tip of the soft robot, while simultaneously, air pressure was applied inside the chamber. Following the optimization of the geometry, a prototype of the soft robot with the optimized values was fabricated and tested in a phantom model, mimicking simulated surgical conditions. The decreased actuation effort and radial expansion of the soft robot resulting from the optimization process have the potential to increase the performance of the manipulator. This advancement led to improved control over the soft robot while additionally minimizing unnecessary cross-sectional expansion. The study demonstrates the effectiveness of the optimization methodology for refining the soft robot’s design and highlights its potential for enhancing surgical interventions. Full article

In order to design an involute spline made of PEEK (polyetheretherketone)-based material with better performance and improve the design rules of involute splines, initially, an involute splines design theory for PEEK (polyetheretherketone)-based materials is presented, which combines international standards (ISO 4156, 1. 2. 3, 2005), American standards (ANSI B92.2M. 1989), and traditional empirical formulas. Second, using the involute splines calibration method in international standards as a guide, we developed the involute splines calibration method for PEEK-based materials by estimating the impact of energy consumption caused by viscoelasticity on temperature field calibration. Next, the contact characteristics of the designed spline were analyzed using ABAQUS2022 software to confirm the accuracy and reliability of the design and calibration methods. Finally, finite element simulation was used to analyze the influence of different pressure angles, moduli, combined lengths, and other parameters on the contact characteristics of the spline in order to realize the optimal design of PEEK-based material involute splines, to offer a theoretical foundation and improved design methodology for cylindrical straight-tooth involute splines. Full article

The increasing usage of autonomous and automatic systems within the automotive industry is steering us towards a more interconnected world. This enhanced interconnectivity fosters a more streamlined driving experience, reduces costs, and provides timely driver assistance. The electric/electronic (EE) architectures of modern vehicles are inherently complex due to the multitude of components they encompass. Contemporary architectures reveal that these components converge at an electronic control unit (ECU) called the central gateway, which could potentially represent a single point of failure. While this central unit is typically adequately safeguarded, the same cannot be said for the connected components, which often remain vulnerable to cyber threats. The ISO/SAE 21434 standard paved the way for automotive cybersecurity and could be used in parallel with other standards such as ISO 26262 and ISO PAS 21488. Automatic collision notification (ACN) is one of the most typical systems in a vehicle, and limited effort has been dedicated to identifying the most suitable architecture for this feature. This paper addresses the existing security and privacy gap of this feature by conducting a comparative analysis of security threats in two distinct ACN architectures. Notably, despite ACN architectures exhibiting inherent similarities, the primary distinction between the two architectures lies in their strategies for crash estimation and detection, followed by subsequent communication with emergency response teams. A rigorous security assessment was conducted using the ISO/SAE 21434 standard, employing the TARA and STRIDE methodologies through the Ansys medini analyze software. This analysis identified an average of 310 threats per architecture, including a significant number of high-level threats (11.8% and 15%, respectively), highlighting the importance of a comprehensive evaluation. Full article

The current work concerns the problem of estimating the aerodynamic forces and moments induced by the wind on the fast-erecting 63K crane by Liebherr. In the first step, scaled sectional models of the tower truss and horizontal jib truss are prepared for experimental analysis in an aerodynamic tunnel. Next, the aerodynamic forces and moments are measured in the aerodynamic tunnel. It is assumed that the direction of the wind changes from 0° to 180° in 15° steps for both of the studied sectional models. The experimental tests are carried out for two levels of turbulence intensity. In the case of the model of the vertical part of the studied crane, the turbulence intensities are assumed to be equal to 3% and 9%. In the case of the horizontal crane jib, they are 3% and 12%, respectively. In the second step, a CFD analysis is performed with the use of Ansys Fluent R22 software. The standard k-ε model with a standard wall function of the turbulent flow is utilized. The airflow around the studied structures is modeled with the use of polytetrahedral cells. A relatively good agreement between the numerical and experimental results is observed. The obtained values are compared to the appropriate standard, namely PN-ISO 4302. Full article

This article is focused on a case study of the topology optimisation of a bike stem manufactured by selective laser melting (SLM) additive technology. Topology optimisation was used as a design tool to model a part with less material used for transferring specific loads than the conventional method. For topology optimisation, Siemens NX 12 software was used with loads defined from the ISO 4210-5 standard. Post-processing of the topology-optimised shape was performed in Altair Inspire software. For this case study, the aluminium alloy AlSi10Mg was selected. For qualitative evaluation, the mechanical properties of the chosen alloy were measured on the tensile specimens. The design of the new bike stem was evaluated by Ansys FEA software with static loadings defined by ISO 4210-5. The functionality of the additively manufactured bike stem was confirmed by actual experiments defined by ISO 4210-5. The resulting new design of the bike stem passed both static tests and is 7.9% lighter than that of the reference. Full article

This study investigates the behavior of three concrete beams reinforced with steel and GFRP bars under fire exposure. The fire tests of three beams were conducted including one control steel-reinforced concrete (RC) beam and two GFRP-RC beams. The beams were exposed to fire according to the standard fire curve ISO 834 for 3 h. The investigation parameters included the reinforcement types (i.e., steel and GFRP bars) and diameter of GFRP bars. Based on the experimental results, during fire exposure, the deflection rate of the steel-RC beam was lower than the ones reinforced with GFRP bars. The critical temperatures measured at steel and GFRP bars in the steel-RC and GFRP-RC beams were 593 °C and 300–330 °C, respectively along with the fire durations of 83 and 33–36.4 min, respectively. The different GFRP bar sizes did not affect the fire resistance process. The steel-RC beam had greater fire resistance than the GFRP-RC beams. All test specimens had a fire resistance time lower than two hours. In addition, the 2D simplified finite element method (FEM) using commercial software ANSYS was performed to predict the thermal response of the beam section. Compared with experimental results, the FE model can reasonably predict the thermal responses of the beam sections. Full article

Exponentially growing technologies such as intelligent robots in the context of Industry 4.0 are radically changing traditional manufacturing to intelligent manufacturing with increased productivity and flexibility. Workspaces are being transformed into fully shared spaces for performing tasks during human–robot collaboration (HRC), increasing the possibility of accidents as compared to the fully restricted and partially shared workspaces. The next technological epoch of Industry 5.0 has a heavy focus on human well-being, with humans and robots operating in synergy. However, the reluctance to adopt heavy-payload-capacity robots due to safety concerns is a major hurdle. Therefore, the importance of analyzing the level of injury after impact can never be neglected for the safety of workers and for designing a collaborative environment. In this study, quasi-static and dynamic analyses of accidental scenarios during HRC are performed for medium- and low-payload-capacity robots according to the conditions given in ISO TS 15066 to assess the threshold level of injury and pain, and is subsequently extended for high speeds and heavy payloads for collaborative robots. For this purpose, accidental scenarios are simulated in ANSYS using a 3D finite element model of an adult human index finger and hand, composed of cortical bone and soft tissue. Stresses and strains in the bone and tissue, and contact forces and energy transfer during impact are studied, and contact speed limit values are estimated. It is observed that heavy-payload-capacity robots must be restricted to 80% of the speed limit of low-payload-capacity robots. Biomechanical modeling of accident scenarios offers insights and, therefore, gives confidence in the adoption of heavy-payload robots in factories of the future. The analysis allows for prediction and assessment of different hypothetical accidental scenarios in HRC involving high speeds and heavy-payload-capacity robots. Full article

The demand for Liquefied natural gas (LNG) has rapidly increased over the past few years. This is because of increasingly stringent environmental regulations to curb harmful emissions from fossil fuels. LNG is one of the clean energy sources that has attracted a great deal of research. In the Republic of Korea, the use of LNG has been implemented in various sectors, including public transport buses, domestic applications, power generation, and in huge marine engines. Therefore, a proper, flexible, and safe transport system should be put in place to meet the high demand. In this work, finite element analysis (FEA) was performed on a domestically developed 40 ft ISO LNG tank using Ansys Mechanical software under low- and high-cycle conditions. The results showed that the fatigue damage factor for all the test cases was much lower than 1. The maximum principal stress generated in the 40 ft LNG ISO tank container did not exceed the yield strength of the calculated material (carbon steel). Maximum principal stress of 123.2 MPa and 107.61 MPa was obtained with low-cycle and high-cycle analysis, respectively, which is 50.28% less than the yield strength of carbon steel. The total number of cycles was greater than the total number of design cycles, and the 40 ft LNG ISO tank container was satisfied with a fatigue life of 20 years. Full article

The biomechanical behavior of the universal link (titanium base) prosthetic abutment with different heights in implant-supported restorations was evaluated. Forty regular implants (4 × 10 mm) in titanium were used, divided into two groups according to the abutment height (n = 20): 4.5 × 4 mm (short) and 4.5 × 5.5 mm (long). Using CAD/CAM technology, zirconia crowns were milled and cemented onto the prosthetic abutments. Half of the specimens were submitted to the initial maximum fracture load test in a universal testing machine. The long abutments presented fracture load (41.1 ± 6.96 kgf) statistically similar to the short abutments (49.5 ± 7.68 kgf). The other half of the specimens were submitted to mechanical cycling (2,000,000 cycles, 2 Hz with a stainless-steel antagonist with a diameter of 1.6 mm), following ISO 14801:2007. Subsequently, the survival of the specimens was evaluated using the survival analysis function, Kaplan–Meier and Mentel–Cox (log- rank) (p < 0.05). The finite element analysis was performed in similar conditions to those used for the in vitro test through computer-aided engineering software (version 19.2, ANSYS Inc., Houston, TX, USA). The biomechanical behavior of both models was similar regardless of the evaluated structure of the set. It was concluded that both short and long abutment presents promising fatigue behavior and stress distribution for use in long-term implant-supported restorations. Full article

Modern autonomous vehicles with an electric/electronic (E/E) architecture represent the next big step in the automation and evolution of smart and self-driving vehicles. This technology is of significant interest nowadays and humans are currently witnessing the development of the different levels of automation for their vehicles. According to recent demand, the components of smart vehicles are centrally or zonally connected, as well as connected to clouds to ensure the seamless automation of driving functions. This necessity has a downside, as it makes the system vulnerable to malicious attacks from hackers with unethical motives. To ensure the control, safety, and security of smart vehicles, attaining and upholding automotive cybersecurity standards is inevitable. The ISO/SAE 21434 Road vehicle—Cybersecurity engineering standard document was published in 2021 and can be considered the Bible of automotive cybersecurity. In this paper, a comparison between four different E/E architectures was made based on the aforementioned standard. One of them is the traditional distributed architecture with many electronic control units (ECUs). The other three architectures consist of centralized or zonally distributed high-performance computers (HPCs). As the complexity of autonomous E/E systems are on the rise, the traditional distributive method is compared against the HPC (brain)-based architectures to visualize a comparative scenario between the architectures. The authors of this paper analyzed the threats and damage scenarios of the architectures using the ISO/SAE 21434 standard, “Microsoft Threat Analysis Tool - STRIDE”, TARA, and “Ansys Medini Analyze”. Security controls are recommended to mitigate the threats and risks in all of these studied architectures. This work attempted to mitigate the gap in the scholarly literature by creating a comparative image of the E/E architectures on a generalized level. The exploratory method of this research provides the reader with knowledge on four different architecture types, their fundamental properties, advantages, and disadvantages along with a general overview of the threats and vulnerabilities associated with each in light of the ISO/SAE 21434 standard. The improvement possibilities of the studied architectures are provided and their advantages and disadvantages are highlighted herein. Full article