Comparison of Load Carrying Capacity of Three and Four Lobed Polygonal Shaft and Hub Connection for Constant Grinding Diameter

Polygonal shafts are used in power transmission as alternatives to keyed and splined shafts. They are designed using DIN standards. This research explores the loading strength of the standardized three lobed (P3G) and four lobed (P4C) polygonal shafts and hubs manufactured from the same stock size, subjected to torsional bending load at various fits. Due to complex conformal contact (nonlinear model) between the shaft and the hub, there is no analytical solution and, therefore, Finite Element Method had been used to determine the stresses, after validating experimentally and using the DIN standard. From the analysis, it was found that the hub experienced greater stress than the shaft in all cases and the major stress in a polygonal shaft and hub connection is the contact stress. The clearance fit was found to be the most detrimental fit and the interference fit to be the most suitable for larger power transmission. Owing to its small normal axial stress and hub displacement, the P4C clearance fit has its use in low power transmission where a sliding fit is a requirement. The maximum von Mises stress was located below the surface for P4C and P3G clearance fit, suggesting failure from pitting and fretting on these shafts. All of the stresses were found to be higher in P4C than P3G for similar loading. Therefore, for general use, the P3G profile with an interference fit is recommended.

Modeling of the Gas-Controlled Crack Growth: Non-Ideal vs Ideal Sink

We consider delamination crack growth controlled by gas diffusion into crack. Initially, with small pressure, the crack can be considered as an ideal sink. However, as crack grows, the pressure becomes greater, and therefore the crack cannot be considered an ideal sink anymore. In this research for both ideal- and real-sink conditions, closed-form solutions for the dependence of the radius of the growing delamination on time are obtained.

On the Effective Properties of 3D Metamaterials

A continuum-based model is developed for the octet-truss unit cell in order to describe the effective mechanical properties (elastic modulus) of the lattice structure. This model is to include different geometric parameters that impact the structural effects; these parameters are: lattice angle, loading direction, thickness to diameter ratio, diameter to length ratio, and ellipticity. All these geometric parameters are included in the stiffness matrix, and the impact of each parameter on the stiffness tensor is investigated. Specifically, the effect of the lattice angle on the elastic moduli is discussed, and the loading direction of the highest elastic modulus is investigated for different lattice angles. Furthermore, the Gurtin-Murdoch model of surface elasticity is used to include the size effect in the stiffness tensor, as well as anisotropy of this model is investigated.

Evaluate the Importance of Shear Modulus in Dynamic FEM of Flexible Pavement Considering AC Cross-Anisotropy

Goal of this study is to evaluate the effect of shear modulus variation on pavement responses, such as stress-strain, under dynamic load incorporating the AC cross-anisotropy. A dynamic Finite Element Model (FEM) of an instrumented asphalt pavement section on Interstate 40 (I-40) near Albuquerque, New Mexico, is developed in ABAQUS to determine stress-strain under truck tire pressure. Laboratory dynamic modulus tests were conducted on the AC cores to determine the temperature and frequency varying modulus values along both vertical and horizontal directions. The test outcomes are used to produce cross-anisotropic and viscoelastic parameters. Resilient modulus tests are conducted on granular aggregates from base and subbase layer to determine the nonlinear elastic and stress-dependent modulus values. These material parameters are integrated to the FEM through a FORTRAN subroutine via User Defined Material (UMAT) in the ABAQUS. The developed FEM is validated using the pavement deflections and stress-strain data under Falling Weight Deflectometer (FWD) test. The validated dynamic FEM is simulated under the non-uniform vertical tire contact stress. For the parametric study to investigate the effect of shear modulus variation on pavement responses, the validated FEM is simulated by varying the shear modulus in the AC layer. The results show that the variation in shear modulus along a vertical plane barely affects the tensile strain at the bottom of the AC layer and vertical compressive strains in both AC and unbound layers.

Computational Modeling of Anterior and Posterior Pelvic Organ Prolapse (POP)

Pelvic Organ Prolapse (POP) is a condition of the female pelvic system suffered by a significant proportion of women in the U.S. and more across the globe, every year. POP is caused by the weakening of the pelvic floor muscles and musculo-connective tissues due to child birth, menopause and morbid obesity. Prolapse of the pelvic organs namely the urinary bladder, uterus, and rectum into the vaginal canal can cause vaginal discomfort, strained urination or defecation, and sexual dysfunction. To date, success rates of native tissue POP surgeries vary from 50–70% depending on the definition of cure and time-point of assessment. A better understanding of the mechanics of prolapse may lead to improvement in surgical outcomes. In the current work, the mechanics of progression of anterior and posterior vaginal prolapse were modeled to understand the effect of bladder fill and posterior vaginal stresses using computational approaches. A realistic and full-scale female pelvic system model, comprised of the urinary bladder, vaginal canal, uterus, rectum, and fascial connective tissue, was developed using image segmentation methods. All of the relevant loads and boundary conditions were applied based on a comprehensive study of the anatomy and functional morphology of the female pelvis. Hyperelastic material models were adopted to characterize all pelvic tissues, and a non-linear analysis was invoked. In the first set of simulations, a realistic bladder filling and vaginal tissue stiffening in prolapse were modeled and their effects on the anterior vaginal wall (AVW) were estimated in terms of the induced stresses, strains and displacements. The degree of bladder filling was found to be a strong indicator of stress build-up on the AVW. Also, vaginal tissue stiffening was found to increase the size of the high stress zone on the AVW. The second simulation consisted of modeling the different degrees of posterior vaginal wall (PVW) prolapse, in the presence of an average abdominal pressure. The vaginal length was segmented into four sections to study the localized stresses and strains. Also, a clinically well-known phenomena known as the kneeling effect was observed with the PVW in which the vaginal wall displaces away from the rectum and downward towards the vaginal hiatus. All of these results have relevant clinical implications and may provide important perspective for better understanding the mechanics of POP pathophysiology.

Dynamic Simulation of Large Flow Solenoid Valve

A nonlinear dynamic model of a large flow solenoid is presented with the multi-physics dynamic simulation software called SimulationX. Validation is performed by comparing the experimental results with the simulated ones. The dynamic characteristics of the large flow solenoid valve are analyzed. Different structural parameters are modified in this research and the diameter of the orifice is proved to be one of the most important parameters which influences the pressure response most.

A Coupled Temperature-Displacement Numerical Analysis of Hydraulic Press Workspace

The analysis is performed on a hydraulic press which is intended for use in the automotive industry and is a part of a production line. The final phase of manufacture of interior and acoustic parts takes place in this press. These interior and acoustic parts are made of sandwich fabric which is inserted into the heated mould of the press and by treatment with a defined pressure (or, more precisely, a defined compression) and temperature, it is formed into its final shape. This press has a frame with four columns and it is not preloaded. Two double acting hydraulic cylinders placed on an upper cross beam exert the compressive force. Due to continuously increasing demands on the accuracy and quality of products not only in the automotive industry, it is necessary to ensure compliance with the accuracy of certain values of machine operation. Especially in this case, the value of accuracy substantially depends on the clamping plates of the press, for which a certain value of flatness is required, both at room temperature and at elevated temperatures. To achieve this accuracy, it is necessary to guarantee sufficient stiffness of the machine to resist the pressing force with the smallest deformation possible. Another crucial factor affecting the accuracy of the machine is heating of the heated clamping plates. Unequal heating of parts of the frame causes additional deformation that has to be quantified and eliminated. The main aim was to verify the design of the press by numerical computation and gather knowledge for modifying the topological design of the press so that it fulfils the required customer parameters of flatness and parallelism for different types of loading. A computational model of the press was created for the numerical solution of a coupled temperature-displacement numerical analysis. The analysis was performed using the finite element method in Abaqus software. The press is symmetrical in two orthogonal planes and the load of the press is considered to be centric. On the basis of these two factors it was possible to carry out the analysis by considering only a quarter of the press. The analysis was used to investigate the effects of static and combined loads from the pressing force and heat on the press. The influence of a cooling circuit located in the press frame for the reduction of frame deformation (and deformation of clamping plates) was investigated. Contacts were defined among individual parts to ensure the computational model had characteristics as close as possible to the real press. The analysis was solved as stationary, on the basis that the cooling of the tool between individual pressing cycles is negligible. The insulating plates are made of a particulate composite material which was considered to have isotropic properties depending on the temperature. For strength evaluation of composite materials all individual components of the stress tensor were examined according to the maximum stress criterion. Hook’s law was considered to be valid for the metallic materials. Von Mises criterion was used to evaluate the strength of the metallic materials. The geometry of the press was discretized using 3D linear thermally coupled brick elements with 8 nodes and full integration (C3D8T). There were approximately 174,000 elements in total. Design procedures for designing a press frame with higher work accuracy (flatness) were proposed with the example of the simplified model of the press table. With these methods it is possible to achieve times higher accuracy than is achieved with conventional method.

Deformation and Failure Mechanisms of Austenitic Piping Under the Influence of Oxyhydrogen Reactions

The present paper deals with the deformation and failure mechanisms of austenitic piping under the influence of oxyhydrogen reactions for the safety evaluation of incident scenarios in technical installations based on previous work of the author [1–5]. For the characterization of the processes, detonation tests performed at the Materials Testing Institute University of Stuttgart (MPA Stuttgart) have been used. The aim of these experiments was to study the detonation processes in head spray cooling piping of boiling water reactors. The experiments were performed on austenitic pipes with an outer diameter of O. D. = 114.3 mm and various wall thicknesses. Oxyhydrogen was used in its stoichiometric ratio of 2H2+O2 mixed with various amounts of an inert gas component. These tests have shown that less amounts of reactive gas may result in a stronger reaction of the pipe structure. This observation is attributed to the influence of the so-called overdriven detonation. Depending on the ratio of oxyhydrogen to the inert gas component and the pipe-wall thickness, adiabatic shear bands can occur in the piping structure. Adiabatic shear bands are very narrow zones with intense localized shear deformations due to the conversion of a significant portion of strain energy into heat. In order to describe this phenomenon numerically, a strain-based failure model was used which can reflect material damage over a wide range of different stress states. However, it has shown that damage of the studied material depends significantly on the Lode angle. Furthermore, no clear dependence of the failure limit on the loading rate has been found for the studied material. For the constitutive description of the material behavior under the occurring loading rates and temperatures suitable material models were selected and the required parameters have been evaluated experimentally and verified by numerical methods. With the aid of this constitutive description of the material behavior and the failure model numerical simulations of the detonation tests were carried out.

Ring Specimen Geometry for Determining the Ductility of Tubulars

Pressure vessels designed in accordance with the ASME BPVC code are protected against local ductile failure. Recent work has shown that local ductile failure highly depends on the stress state characterized by both stress triaxiality (T) and the Lode parameter (L). In this paper, the effect of stress state on the ductility of a tubular steel is studied. Two ring specimen configurations were optimized to allow the determination of the ductile failure locus of both tensile and plane strain loadings. The geometry of both ring specimen configurations was optimized to achieve a plane strain (L = 0) condition and a generalized tension (L = −1) condition. Notches with different radii were machined on both types to achieve a wide range of stress triaxiality. Specimens were manufactured from SA-106 carbon tubular steel and were tested to determine the ductile failure loci as a function of T and L. Failure locus of SA-106 steel was constructed based on the failure instants and was found to be independent of the variation in the Lode parameter. The ASME-BPVC local failure criterion showed close agreement with experimental results.

Design, Fabrication, and Characterization of a Soft Multi-Fingered Hand

This paper describes the design, fabrication, testing and modeling of the SUR Hand. The SUR Hand is a soft, under actuated robotic hand. Through an iterative design and manufacturing process, SUR Hand’s soft, actuating components have been adapted from the original PneuFlex, pneumatically actuated finger to be highly flexible and capable of actuating a precision force. This paper shows how altering the design parameters of the fingers altered their overall performance. Furthermore, it details the experimental setup for testing the components, as well as the modeling methods used. Finally, it shows the process for creating and validating a geometric model that characterizes proper grasping strategies, assuming a passive palm component.