Adeeb Rahman

Measuring sideslip and camber characteristics of bicycle tyres

Sideslip and camber tyre properties, the forces and moments a tyre generates as it rolls forward under different circumstances, have been found to be important to motorcycle dynamics. A similar situation may be expected to exist for bicycles, but limited bicycle tyre data and a lack of the tools necessary to measure it may contribute to its absence in bicycle dynamics analyses. Measuring these properties requires holding the tyre at a fixed orientation with respect to the pavement and its direction of travel, and then measuring the lateral force and torque about the steer axis generated as the tyre rolls forward. Devices exist for measuring these characteristics of automobile tyres. One device is known to exist specifically for motorcycle tyres, and it has been used at least once on bicycle tyres, but the minimum load it can apply is nearly double the actual load carried by most bicycle tyres. This paper presents a low-cost device that measures bicycle tyre cornering stiffness and camber stiffness.

The effect of fire loading on a steel frame and connection

The objective of this paper is to investigate the behavior of steel shear connections subjected to severe fire loading conditions. A time-history transient FE analysis is used to model the fire loading. A detailed 3D FE model of an extended shear tab steel connection used in a beam-column joint is developed. The shear tab plate is welded to the web of the column and it is connected to the web of the beam by tightened bolts. The change in steel material properties such as the modulus of elasticity, yield and ultimate strength, and the coefficient of thermal expansion are considered as functions of increasing temperature resulting from fire loading. Stress-strain curves for steel at elevated temperatures are used in the model. Two cases of boundary conditions are studied: one representing a roller at the far end of the beam, another assumes that the beam is pin supported. The base of the column is maintained as a fixed support, while the upper edge of the column is free to deflect in the vertical direction as shown in Figure 2. Pre-tensioning loads are modeled to represent the tightening of the bolts. A fire curve based on tests conducted in accordance with ASTM E119, is applied to the connection and the structural members. Results show deflection, rotations, and distortion fields of the structural components for both conventional and new fire resisting steel. Mechanical and thermal plastic strain and stress fields are predicted, documenting yielding, plasticity and ultimate failure in the plate, bolts and structural members. This is a 3D nonlinear model that provides graphical and empirical results for a variety of steel connections that could be used for comparison with established experimental results if available. Design recommendations, failure limitations, and material selection and specifications can be suggested for steel connections in such fire loading.

Finite Element Analyses of Flush End-Plate Connections between Steel Beams and Columns at Elevated Temperatures

This paper presents a finite element analysis procedure developed to study the behaviour of a flush end-plate connection between steel beams and a column at elevated temperatures and generates temperature-rotation diagrams that describe the behaviour of the connection. The analysis uses a highly detailed three dimensional finite element model that is created using the commercial ANSYS software. The steel connection properties are selected in a way that reflects commonly used connections in steel framed buildings. The results of the finite element model are calibrated and compared to the results of experimental fire tests conducted on similar connections. This comparison shows a deviation of about 12% which is reasonable considering the complexity and the nonlinear nature of the analysis. Furthermore, the same methodology used to create the finite element model of isolated steel connections is then used to create a sub-frame constructed with similar connections. Both the applied loads and the dimensions of the model represent a part of a typical steel framed building that is subjected to a fire outbreak in one of its bays. The results indicate that at low temperatures, the main beam is snugly fixed and the joints at both sides provide full rigidity whereas at elevated temperatures the central deflection is rapidly increased because of plastic hinge formation. Although this frame has not been tested in reality, the finite element model gives a prediction of the failure mechanism of such a frame under fire loads without the use of expensive full scale testing facilities.

CT-scan based FEA for the assessment of the effect of bone density on femur's fracture

The apparent correlation between bone density and susceptibility to fracture was evaluated using finite element modeling. Based on computed tomography data of an actual femur bone, a versatile virtual model was created and modified in order to simulate different bone geometries and densities. Under typical load conditions the highest strains were calculated for the inferior side of the femur shaft, and the anterior side of the femur neck close to the trochanter. Strain values consistently decreased with raising cortical bone content.

Evaluation of the Low-Cycle Fatigue Life in Seven Steel Bar Types

AbstractThe low-cycle fatigue (LCF) behavior of steel in energy-dissipating seismic connections is an important consideration, especially in light of the interest in performance-based seismic design. In this study, the LCF performance of seven steel bar types (AISI 8620, 1018, 1045, 1117, 1215, 4140 and ASTM A36 steel) was experimentally examined and compared. The bar specimens were subjected to sinusoidal strains of constant amplitude from zero to peak strains of 4%, 6%, or 8%. Equations that relate the applied strain amplitudes with the number of cycles to failure were developed and compared. In addition, relationships for calculating the total dissipated energy corresponding to the applied strain amplitude were proposed based on the experimental results. This study demonstrated that, in general, the LCF resistance of AISI 1045 steel type outperformed the other steel materials at a strain amplitude of ±2%. However, at ±3 and ±4% strain amplitudes, the LCF lives of ASTM A36 and AISI 1117 bars outperforme...

Finite element analysis of tension-loaded ASTM A325 bolts under simulated fire loading

Purpose Nuts and bolts have been used as fasteners of steel structures for many years. However, these structures remain susceptible to fire damage. While conducting fire experiments on steel structures is sometimes necessary, to better understand their behavior, such experiments remain costly and require specialized equipment and testing facilities. This paper aims to present a highly accurate three-dimensional (3D) finite element (FE) model of ASTM A325 bolt subjected to tension loading under simulated fire conditions. The FE model is compared to the results of experimental testing for verification purposes and is proven to predict the response of similar bolts up to certain temperatures without the need for repeated testing. Design/methodology/approach A parametric 3D FE model simulating tested specimens was constructed in the ANSYS Workbench environment. The model included the intricate details of the bolt and nut threads, as well as all the other components of the specimens. A pretension load, a tension force and a heat profile were applied to the model, and a nonlinear analysis was performed to simulate the experiments. Findings The results of the FE model were in good agreement with the experimental results, deviations of results between experimental and FE results were within acceptable range. This should allow studying the behavior of structural bolts without the need for expensive testing. Originality/value Detailed 3D FE models have been created by the authors have been created to study the behavior of structural bolts and compared with experiments conducted by the authors.

Behavior of ASTM A325 bolts under simulated fire conditions: experimental investigation

Purpose Heavy hex structural bolts have been used in a wide range of steel structures for many years. However, these structures remain susceptible to fire damage. Conducting fire experiments on full-scale steel structures is costly and requires specialized equipment. The main purpose of this research is to test, analyze and predict the behavior of ASTM A325 bolts under tension loading in simulated fire conditions and develop a reliable finite element model that can predict the response of similar bolts without the need for repeated testing. Design/methodology/approach The experimental work was conducted at the University of Wisconsin-Milwaukee, where an electric furnace was custom-built to test a bolted specimen in tension under elevated temperatures. A transient-state testing method was adopted to perform a group of tests on 12.7 mm (½”) – diameter A325 bolts. The tests were divided into two groups: the first one was used to calibrate the equipment and choose a final testing arrangement and the second group, consisting of four identical tests, was used to validate a finite element model. Findings The temperature-displacement and load-displacement response was recorded. The tested bolts exhibited a ductile fracture in which a cup-and-cone shaped failure surface was formed in the threaded section at the root of the nut. ASTM A325 bolts are widely used by engineers in building and bridge construction, the results of this research enable engineers to determine the behavior and strength of ASTM A325 bolts when such bolts when exposed to fire event. Research limitations/implications Structural bolts are used to connect structural members, and they are part of structural assembly. To study the behavior of the bolts, the bolts only were investigated in a fire simulated in a furnace. The bolts studied were not part of a structural assembly. Practical implications The results of this study enable engineers to evaluate the condition of ASTM A325 bolts when subjected to fire loading. Originality value Tests were conducted at the University of Wisconsin – Milwaukee’s structures laboratory to study the effect of fire on an ASTM A325 bolts. Many tests under fire loading have been performed by researchers on different components of steel structures, this study focuses on studying the behavior of ASTM A325 bolts which are widely used in the USA.

Benchmarking Bicycle and Motorcycle Equations of Motion

In 2007, Meijaard, et al. [1] presented the canonical linearized equations of motion for the Whipple bicycle model along with test cases for checking alternative formulations of the equations of motion or alternative numerical solutions. This paper describes benchmarking three other implementations of bike equations of motion: the linearized equations for bicycles written by Papadopoulos and Schwab [2] in JBike6, the non-linear equations for bicycles outlined by Schwab [3] and implemented in MATLAB as a Cornell University class project, and the non-linear equations for motorcycles implemented in FastBike from the Motorcycle Dynamics Research Group at the University of Padua. [4] Some implementations are easier to benchmark than others. For example, JBike6 is designed to produce eigenvalues and easily exposes the coefficients of its linearized equations of motion. At the other extreme, the class project non-linear equations were not originally intended to generate eigenvalues and are implemented in a single 48×48 matrix. Finally, while FastBike does generate eigenvalues, its equations of motion incorporate tire and frame compliance, which cannot be completely disabled. Instead, the tire stiffness parameters must be increased, but not so much as to cause convergence errors in FastBike. In the end, all three implementations generate eigenvalues that match the published benchmark values to varying degrees. JBike6 comes the closest, with agreement of 12 digits or more. The class project is second, with agreement of 12 digits for most forward speeds, but with a loss of measurable agreement near the capsize speed due to a peak in the eigenvalue condition number. Unfortunately, FastBike is limited at this time to exporting eigenvalues with no more than two decimal places, and so agreement can only be found to ±0.005.Copyright