Numerical studies on the heat dissipation process in elastomers under rotating loading direction

Elastomeric components such as car bearings and vibration dampers are subjected to dynamic loads with various amplitudes and loading directions during operation. To better understand the lifetime expectancy of these components it is required to implement a material model that sufficiently accounts for the material thermo-mechanical behaviour. This paper implements a finite viscoelastic model which includes heat dissipation and addresses the effect of inelasticity on the self-heating and the applied loading conditions. The material model is implemented in a user subroutine and finite element calculations are carried out on a simple shear loading with rotating directions. The self-heating effect and the resulting variation of the dissipation induced forces are shown and discussed. With the aid of the presented material model, thermo-mechanically coupled simulations can be performed. Based on the results, the required loading limits and boundary conditions for the mechanical fatigue tests can be defined to minimise the thermal fatigue effects.

Self-sensing performance of metakaolin geopolymer with carbon nanotubes subjected to repeated compressive loading

Alkaline activated binders showing enhanced piezoresistive properties have recently attracted increased interest in research of their application in smart self-sensing components. This study is focused on metakaolin geopolymer mortar doped with 0.05 and 0.10% carbon nanotubes, a conductive filler that effectively increases electrical conductivity without considerable deterioration of mechanical properties. Self-sensing performance of composites incorporated with electrodes and attached strain gauge was tested during different regimes of compressive loading cycles with continuous monitoring of strain and resistivity. Although the differences in sensitivity and repeatability were observed, all samples including the reference material have shown good response to applied loading.

Finite Element Analysis of Gasket in Pressure Vessel

Pressure vessel is a closed container designed to hold liquids or gases at a pressure which are higher than the surrounding atmospheric pressure. These pressure vessels are not made as a single component but manufacture with an assembly of many other components and connected through bolted joints or riveted joints or welded joints. These joints are susceptible to failure and cause leakage of the liquid or gas which are very dangerous and sometimes causes heavy loss of life, health and property. Hence proper care has to be taken during the design analysis processes by following ASME section VIII division 1 which specifies the design-by-formula approach while division 2 contains a set of alternative rules based on design by Analysis (FEA) to determine the expected deformation and stresses that may develop during operation. The ASME section-VIII division-2 standards are used for the design of pressure vessel. Leakage in gasketed flanged joints have always been a great problem for the process industry. The sealing performance of a gasketed flanged joints depends on its installation and applied loading conditions. The present project work involves the design procedure and stress analysis (Structural Analysis) for the leak proof pressure vessel at the gasket under three different gasket conditions. Keywords: 1. FEM, 2. ASME, 3. ANSYS, 4. Gasket,5. Displacement,6. Stress

About the Memory of Transformation-Induced Plasticity in 35NCD16 Carbon Steel Subjected to Various Thermomechanical Histories

This study deals with Transformation-Induced Plasticity (TRIP) observed in the martensitic transformation of 35NCD16 ferritic steel. In this study, TRIP tests were carried out for two different cases: First, after only free dilatometric (FD) tests, which is used as the reference test for the considered applied stress; second, with TRIP tests being performed similarly to the first case (same thermal cycle, same applied stress) but with pre-thermomechanical loading histories applied. Such histories may be FD tests, TRIP tests, elastoplastic history, etc. The comparison between the results of TRIP test (a) and TRIP test (b) indicates if TRIP holds the memory of the applied loading histories. The current obtained results tell us that TRIP does not hold any significant memory. During the martensite à austenite transformation, the material may present recovery from strain hardening. Waiting for more details about the physical phenomena responsible for the absence of TRIP memory, one can point out the importance of this result as it enables one to use the same specimen for several TRIP tests. However, this result must be validated using other combinations of loading histories (such as multiaxial and cyclic, among others).

On a Novel Approximate Solution to the Inhomogeneous Euler–Bernoulli Equation with an Application to Aeroelastics

This paper focuses on the development of an explicit finite difference numerical method for approximating the solution of the inhomogeneous fourth-order Euler–Bernoulli beam bending equation with velocity-dependent damping and second moment of area, mass and elastic modulus distribution varying with distance along the beam. We verify the method by comparing its predictions with an exact analytical solution of the homogeneous equation, we use the generalised Richardson extrapolation to show that the method is grid convergent and we extend the application of the Lax–Richtmyer stability criteria to higher-order schemes to ensure that it is numerically stable. Finally, we present three sets of computational experiments. The first set simulates the behaviour of the un-loaded beam and is validated against the analytic solution. The second set simulates the time-dependent dynamic behaviour of a damped beam of varying stiffness and mass distributions under arbitrary externally applied loading in an aeroelastic analysis setting by approximating the inhomogeneous equation using the finite difference method derived here. We compare the third set of simulations of the steady-state deflection with the results of static beam bending experiments conducted at Cranfield University. Overall, we developed an accurate, stable and convergent numerical framework for solving the inhomogeneous Euler–Bernoulli equation over a wide range of boundary conditions. Aircraft manufacturers are starting to consider configurations with increased wing aspect ratios and reduced structural weight which lead to more slender and flexible designs. Aeroelastic analysis now plays a central role in the design process. Efficient computational tools for the prediction of the deformation of wings under external loads are in demand and this has motivated the work carried out in this paper.

Sequentially Working Origami Multi-Physics Simulator (SWOMPS): A Versatile Implementation

This work presents the underlying implementation of a new origami simulator (SWOMPS) that allows for adaptability and versatility with sequential analyses and multi-physical behaviors of active origami systems. The implementation allows for easy updating of origami properties, realistic simulation with multi-physics based actuation, and versatile application of different loadings in arbitrary number and sequence. The presented simulator can capture coupling between multiple origami behaviors including electro-thermo-mechanical actuation, heat transfer, self-stress induced folding, inter panel contact, applied loading forces, and kinematic/mechanical deformations. The simulator contains five different solvers, including three for mechanical loading, one for self-folding, and one for thermal loading. The paper presents details of this code package and uses three practical examples to highlight the versatility and efficiency of the package. Because various loadings and different origami behaviors can be modeled simultaneously and/or sequentially, this simulator is well suited for capturing origami behaviors in practical real-world scenarios. Furthermore, the ability to apply an arbitrary number and sequence of loadings is useful for design, optimization, or system control studies where an unknown set of loads are needed to fold functional active origami. The coded implementation for this simulator and additional examples are made available to encourage future expansions of this work where new sequential and multi-physical behaviors in origami can be explored.

Contractile behavior of the gastrocnemius medialis muscle during running in simulated hypogravity

Vigorous exercise countermeasures in microgravity can largely attenuate muscular degeneration, albeit the extent of applied loading is key for the extent of muscle wasting. Running on the International Space Station is usually performed with maximum loads of 70% body weight (0.7 g). However, it has not been investigated how the reduced musculoskeletal loading affects muscle and series elastic element dynamics, and thereby force and power generation. Therefore, this study examined the effects of running on the vertical treadmill facility, a ground-based analog, at simulated 0.7 g on gastrocnemius medialis contractile behavior. The results reveal that fascicle−series elastic element behavior differs between simulated hypogravity and 1 g running. Whilst shorter peak series elastic element lengths at simulated 0.7 g appear to be the result of lower muscular and gravitational forces acting on it, increased fascicle lengths and decreased velocities could not be anticipated, but may inform the development of optimized running training in hypogravity. However, whether the alterations in contractile behavior precipitate musculoskeletal degeneration warrants further study.

Quantification of vertical, lateral, and longitudinal fastener demand in broken spike track: Inputs to mechanistic-empirical design

To address a recent challenge related to broken spikes in premium elastic fastening systems that have led to at least ten derailments and require manual walking inspections as well as build upon mechanistic-empirical (M-E) design principles for future fastening system component design, this paper quantifies the vertical, lateral, and longitudinal fastening system loads under revenue service traffic in a curve that has regularly experienced spike fastener fatigue failures. Previous data has indicated that the high rail of Track 3 experienced the most failures at this location. The data from this investigation sheds light into why failures are more predominant at this location than others and how the vertical, lateral, and longitudinal loads cannot be considered independently. Specifically, while the magnitude of the applied loading was the lowest on the high rail of Track 3, the threshold for failure was also the lowest given the operations at this location led to unloading of the high rail, thus indirectly highlighting the importance of friction within a fastening system. The data also show the high rail of Track 3 was subjected to the highest L/V load ratios and was an outlier in the typical lateral load reversals applied likely leading to spike stress reversals and thus a shorter fatigue life. Finally, based upon the data, it is recommended that to mitigate spike failures, as well as similar fastener challenges in other track types (e.g. rail seat deterioration, etc.) railroads should ensure trains operate close to the balance speed and use fastening system that transfer loads through friction. This study also provides novel data for M-E design of fastening systems.

Analysis of a Support Base Stand using Finite Element Analysis

In this paper, deformation, Von-Mises stress, and failure analysis were carried out on a base stand using ANSYS workbench. The structural design was carried out using SolidWorks software and then imported into the ANSYS workbench for analysis. The investigation is performed using four different materials, i.e., structural steel, aluminum alloy, carbon fiber, and copper alloy, with an applied loading force of 1000 N at the tip of the structure. This technique highlights a complete reaction of the structure to the loading force, therefore providing room for structural optimization to reduce the risk of unexpected failure and unnecessary material wastage. The results obtained were compared and analyzed to identify the best material capable of withstanding the subjected force. Based on the Von-mises result, Carbon fiber has the highest possible maximum stress value of 4.70e+07 Pa, followed by structural steel, then Copper alloy. At the same time, the aluminium alloy has the least minimum Von-Mises. Structural steel is the very best option based upon the analysis outcomes. Its factor of safety is above unity in all the designs, which indicates that the structure has been over-designed. For that reason, it is suggested that the structure needs to be enhanced. Keywords: Finite element analysis, base stand, ANSYS, deformation, von mises stress.

Comparison of Testing Method Effects on Cracking Resistance of Asphalt Concrete Mixtures

As an inherent characteristic of materials, the fracture toughness is an important parameter to study the cracking behavior of asphalt concrete mixtures. Although material compositions and environmental conditions have a significant effect on the fracture toughness, for a certain material and testing environment, the test condition including the specimen configuration and loading type may also affect the obtained fracture toughness. In this paper, the effect of specimen configuration and applied loading type on the measured pure mode-I fracture toughness (KIc) is investigated. In order to achieve this purpose, using a typical asphalt mixture, four different test specimens including Semi-Circular Bend (SCB), Edge Notch Disc Bend (ENDB), Single Edge Notch Beam (SENB) and Edge Notch Diametral Compression (ENDC) disc are tested under pure mode I. The mentioned specimens have different shapes (i.e., full disc, semi-disc and rectangular beam) and are loaded either with symmetric three-point bending or diametral compressive force. The tests were performed at two low temperatures (−5 °C and −25 °C) and it was observed that the critical mode-I fracture toughness (KIc) was changed slightly (up to 10%) by changing the shape of the test specimen (i.e., disc and beam). This reveals that the fracture toughness is not significantly dependent on the shape of the test specimen. However, the type of applied loading has a significant influence on the determined mode I fracture toughness such that the fracture toughness determined by the disc shape specimen loaded by diametral compression (i.e., ENDC) is about 25% less than the KIc value with the same geometry but loaded with the three-point bending (i.e., ENDB) specimen. In addition, the fracture toughness values of all tested samples were increased linearly by decreasing the test temperature such that the fracture toughness ratio (KIc (@-25 °C)/KIc (@-5 °C)) was nearly constant for the ENDB, ENDC, SCB and SENB samples.