Effect of Design Parameters on Lubrication Behavior of Spur Gear Pairs

An involute spur gear pair meshing model is firstly provided in this study to achieve relevant data such as rolling velocity, sliding velocity, curvature radius etc. These data are needed in a transient, Newtonian elastohydrodynamic lubrication (EHL) model which is provided later. Based on these two models, the behavior of an engaged spur gear pair during the meshing process is investigated under dynamic conditions, film thickness, pressure, friction coefficient etc. could be achieved through the models. Then, power loss under certain operating condition is calculated. Relationship between power loss and lubrication performance is also analyzed.

Sensing Artificial Hole and Crack in Carbon Nanotube Enhanced Glass-Fiber Reinforced Composite Panel

Glass fabric epoxy resin based composite panels enhanced with carbon nanotubes were subjected to damage while changes in electrical resistance were obtained via embedded electrodes. The purpose of the study was to develop an alternative method to Electrical Impedance Tomography (EIT), which generates conductivity field, hence, indicating presence of various damages. The current method provides damage field by taking meticulous measurements of electrical resistance of panel. The method does not monitor conductivity as in the EIT but utilizes electrical resistance changes to detect damage. In the current form, it employs a network of 64 (8 × 8 grid) electrodes distributed evenly in a typical panel instead of the boundary electrodes used in EIT. Even though 64 electrodes were employed, fewer electrodes were sufficient to produce accurate indication of damage location and its size. In previous studies percolation threshold for carbon nanotube-epoxy mixture was determined, which enabled selection of optimal CNT concentration used in manufacturing of glass fiber reinforced panels. The glass fiber reinforced panels were manufactured by vacuum infusion method. The typical panel consisted of 10 glass fabric (S-2) plies. Copper electrodes were embedded beneath the top layer fabric ply. Electrical resistances measurements were obtained using four-probe technique. In the four-probe method, two outer electrodes are used to source a known current through the panel, while the two inner electrodes provide voltage drop needed to compute resistance. The technique minimizes contact resistance between electrodes and the composite, which could be order of magnitude larger than the material resistance being measured. Electrical resistance of cured glass fiber reinforced CNT-epoxy panels was first measured without any damage. Afterwards, damages in form of circular hole were inflicted to the panel starting with 1/8” diameter and enlarging it to 1/2” in steps of 1/8”. After the largest hole, 0.04” (∼1 mm) width cracks emanating from the hole were inflicted. During all measurements, electrical current passing through the source and sink electrodes was kept constant and changes in voltage from the inner probes were recorded. The thrust of the method is to incorporate a curve fit for quantifying the changes in resistance. The method can be applied to damage quantification in panels. The smaller spaced electrode distribution was more sensitive to smaller damages as expected, but the larger spaced electrodes network was sufficiently responsive to smallest damage. Experimental results were fairly good at predicting the damage and its magnitude. Results also indicated a very good agreement with the finite element simulations of the panels. Application of this technique can be a powerful tool for real time structural health monitoring of manufactured composites.

Impact Localization on a Composite Plate With Unknown Material Properties Using PWAS Transducers and Wavelet Transform

In this work, an impact experiment on a composite plate with unknown material properties (its group velocity profile is unknown) is implemented to localize the impact points. A pencil lead break is used to generate acoustic emission (AE) signals which are acquired by six piezoelectric wafer active sensors (PWAS). These sensors are distributed with a particular configuration in two clusters on the plate. The time of flight (TOF) of acquired signals is estimated at the starting points of these signals. The continuous wavelet transform (CWT) of received signals are calculated with AGU Vallen wavelet program to get the accurate values of the TOF of these signals. Two methods are used for determining the coordinates of impact points (localization the impact point). The first method is the new technique (method 1) by Kundu. This technique has two linear equations with two unknowns (the coordinate of AE source point). The second method is the nonlinear algorithm (method 2). This algorithm has a set of six nonlinear equations with five unknowns. Two MATLAB codes are implemented separately to solve the linear and nonlinear equations. The results show good indications for the location of impact points in both methods. The location errors of calculated impact points are divided by constant distance to get independent percentage errors with the site of the coordinate.

Full Frontal Crashworthiness of Carbon Fiber Composite Front Bumper Crush Can (FBCC) Structures

This research study highlights the testing method and relevant results for assessing impact performance of a carbon fiber composite front bumper crush can (FBCC) assembly subjected to full frontal crash loading. It becomes extremely important to study the behavior of lightweight composite components under a crash scenario in order to apply them to automotive structures to reduce the overall weight of the vehicle. Computer-aided engineering (CAE) models are extremely important tools to virtually validate the physical testing by assessing the performances of these structures. Due to lack of available studies on carbon fiber composite FBCCs assemblies under the frontal crash scenario, a new component-level test approach would provide assistance to CAE models and better correlation between results can be made. In this study, all the tests were performed by utilizing a sled-on-sled testing method. An extreme care was taken to ensure that there is no bottoming-out force for this type of test while adjusting the impact speed of sled. Full frontal tests on FBCC structures were conducted by utilizing five high-speed cameras (HSCs), several accelerometers and a load wall. Excellent correlation was achieved between video tracking and accelerometers results for time histories of displacement and velocity. The standard deviation and coefficient of variance for the energy absorbed were very low suggesting the repeatability of the full frontal tests. The impact histories of FBCC specimens were consistent and in excellent agreement with respect to each other. Post-impact photographs showed the consistent crushing of composite crush cans and breakage of the bumper beam from middle due to the production of tensile stresses stretched caused by straightening of the bumper curvature after hitting the load wall.

Peridynamics Using Irregular Domain Discretization With MOOSE-Based Implementation

In this paper, reformulation of classical bond-based peridynamic thermomechanical model for irregular domain decomposition and its MOOSE-based implicit formulation are presented. First, the irregular grid based peridynamic thermomechanical model is formulated and model parameters are derived. Following this, an implicit formulation for the solution of static or quasi-static problems is presented. Some aspects of the MOOSE-based implementation are given. After that, the formulation is verified against benchmark solutions for thermomechanic problems. Crack initiation and propagation in circular (2D) and cylindrical (3D) nuclear fuels at high temperature are studied using irregular grids.

Tunable Triangular Cellular Structures by Pneumatic Control of Dual Channel Actuators

Programmable matter, a material whose properties can be programmed to achieve desired density with volume change, shapes or structural properties (stiffness, strength, Poisson’s ratio, etc.) upon command, is an important technology for intelligent materials. Recently emerging soft robotics-based pneumatic control can be potentially used for the design of programmable matter due to its several advantages — quick response for actuation, stiffening effect with internal air pressure, easy to manufacture, inexpensive materials, etc. The objective of this work is to construct programmable two-dimensional (2D) cellular structures with pneumatic actuators, investigating the effect of local deformation of the pneumatic actuators on the macroscopic pattern generation and mechanical properties of cellular structures. We synthesize 2D soft triangular structures with pneumatic actuators embedding dual air channels wrapped with fiber reinforcement. The local deformation modes provide different macroscopic deformations of cellular structures. We build an analytical model integrating the deformation of a single actuating member with nonlinear deformation of cellular structures. Finite element based simulations and experimental validation are followed. This study integrates soft robotics with cellular structures for intelligent materials design, expanding the design space of materials with programming. The fast response of the tunable soft cellular structures may be an ideal for the application of acoustic metamaterials with tunable band gaps.

The Effect of a Quarter-Circle Corner Crack on the Distribution of the SIF Along the Front of a Non-Aligned Semi-Elliptical Surface Crack in an Infinitely Large Plate Under Uniaxial Tension

The evaluation of the mutual effect of non-aligned multiple cracks is a prerequisite in applying fitness-for-service codes. For non-aligned parallel cracks, during on-site inspection, one needs to decide whether the cracks should be treated as coalesced or separate multiple cracks for Fitness-for-Service. In the existing literature, criteria and standards for the adjustment of multiple nonaligned cracks are very source dependent, and those criteria and standards are often derived from on-site service experience without rigorous and systematic verification. Based on this observation, the authors previously reported on the influence of an embedded crack on an edge crack in 2-D scenarios and, more recently, in 3-D scenarios of the influence of a surface crack on a quarter-circle corner crack. However, realistic crack configurations detected using non-destructive methods are generally 3-D in nature and their influences are mutual. Thus the SIF distribution characteristics along the surface crack is equally important as the SIF distribution of the corner crack when Fitness-for-Service rules are to be applied. Therefore, non-aligned flaws with different configurations and shapes and the SIFs along their crack fronts are deemed necessary in order to obtain more practical guidance in the usage of rules speculated in Fitness-for-Service codes. In this study, the characteristics of the SIF distribution along a semi-elliptic non-aligned surface crack is examined under the influence of a quarter-circle corner crack of various geometries in an infinitely large plate. For any given geometry of a quarter-circle corner crack, a pair of horizontal (H) and vertical (S) separation distances between the two cracks is chosen followed by a detailed analysis of the effect of the quarter-circle corner crack on the 3D SIFs of the surface crack at different ellipticities. The analysis is repeated for various combinations of separation distances S and H. The results from this study are collectively significant to the understanding of the correlation between the criteria and standards in Fitness-for-Service community and the consequence of their usage in engineering practice.

Quench Polish Quench (QPQ) Coating Behavior Under Dynamic Loads

The selection of coating or surface treatments is a crucial step in the design of oil and gas equipment to protect against the deterioration caused by wear, corrosion, galling, fatigue, etc. Quench polish quench (QPQ) nitriding is a superior candidate to increase surface hardness for abrasion and galling resistance in carbon or stainless steels. The increased surface hardness improves the wear and corrosion resistance but reduces the surface material ductility. It is generally not recommended for application to V-shaped threads or sharp notches subjected to high stress. During well perforation in cased-hole completion, the detonation of the gun string along with the induced pressure wave in fluids generates a large-magnitude dynamic motion in the gun string. The peak load of a perforating event, from detonation to fluid-structure interaction, happens in the range of microseconds to milliseconds. The coupled wellbore hydrodynamic and structural dynamic shock load may cause an overstress failure in the millisecond scale but is usually overlooked in engineering practice. In this work, we investigated the behavior of QPQ coating under transient dynamic loads, employing both physical test and finite element analysis. We designed a combination of drop test fixture and specimens to simulate a notched specimen subjected to dynamic tensile loads. Two types of specimens were prepared in this study, QPQ-coated specimens and bare metal specimens without coating. The specimens without coating were tested to serve as a baseline for comparison. The methodology in this study provides a generic guideline for design of equipment potentially subjected to transient mechanical shock loads.

Correlating Dynamic Bifurcations With Impedance Measures for Multistable Structures

Slender, lightweight structures are demanded to meet efficiency targets or to enhance vehicle system performance characteristics. Yet, when subjected to static stress for load-bearing purposes, the flexible structural members may buckle. Furthermore, additional dynamic excitations may activate adverse snap-through responses in such post-buckled components, which accelerates fatigue and failure. The severe nonlinearity associated with these phenomena challenges traditional forms of analysis and necessitates studious experimental methods for conclusive system characterization and model validation. This research builds upon state-of-the-art analytical and experimental strategies to examine the complex forced, dynamic behaviors of built-up structures that contain one or more post-buckled members. An analytical modeling and solution formulation is reviewed that is uniquely amenable to the study of multistable structures and permits experimentally-observable measures of impedance to be identified. Through theoretical and experimental studies, the efficacy of the impedance measures is evaluated towards their usefulness in identifying the onset of dynamic bifurcations in the multistable structural dynamics. For moderate amplitudes of input energy, the analysis is found to provide qualitatively accurate prediction of the drive point impedance changes observed prior to dynamic bifurcations from low to high amplitude of displacement.

90 Degree Impact Simulation of Steel Wheel

The wheel is one of the important safety components of the vehicle. So, it is required to pass the dynamic rotating bending test, the dynamic radial fatigue test and the impact test. The 90-degree impact test represents the driving performance of a vehicle when the vehicle drives through the road pits, or drives in other harsh conditions. As for the steel wheel, there are no mandatory requirements for the impact test. In recent years, some steel wheel enterprises bring up 90-degree impact test for steel wheels in order to ensure the quality of their products. In this paper, a finite element simulation model of the steel wheel impact test bed under the case of 90-degree was established according to an enterprise’s impact test requirement. The software “ABAQUS” was used to simulate the 90-degree impact test. A wheel / tire overall model was assembled, considering the impacts of tire inflation and the tire preloading process. Then the deformation state of the rim under 90-degree impact load was analyzed to predict whether it could pass the requirements of relevant impact test successfully. The results show that the steel wheel does not meet the requirements of the impact test, which makes it necessary to study the steel wheel’s impact test and optimize the structure of the rim. This paper also provides a reference method for the impact simulation of the steel wheel.