Mechanical Engineering Commons^™

Non-Destructive Testing (Ndt) By Laser Shearography And Fringe Projection, Xiaoran Chen, Morteza Khaleghi, Ivo Dobrev, Cosme Furlong

Morteza Khaleghi

Non-destructive testing (NDT) is critical to many precision industries because it can provide important information about the structural health of critical components and systems. In addition, NDT can also identify situations that could potentially lead to critical failures. Specifically, NDT by optical methods have become popular because of their non-contact and non-invasive nature. Shearography is a high-resolution optical NDT method for identification and characterization of structural defects in components and has gained wide acceptance over the last decade; however, as a drawback, shearography cannot locate the position of defects in 3D. To overcome this limitation, we are combining shearography with …

The Formulation And Computation Of The Nonlocal J-Integral In Bond-Based Peridynamics, Wenke Hu, Youn Doh Ha, Florin Bobaru, Stewart A. Silling

Florin Bobaru Ph.D.

This work presents a rigorous derivation for the formulation of the J-integral in bond-based peridynamics using the crack infinitesimal virtual extension approach. We give a detailed description of an algorithm for computing this nonlocal version of the J-integral.We present convergence studies (m-convergence and δ-convergence) for two different geometries: a single edge-notch configuration and a double edge-notch sample.We compare the results with results based on the classical J-integral and obtained from FEM calculations that employ special elements near the crack tip.We identify the size of the nonlocal region for which the peridynamic J-integral value is near the classical FEM solutions.We discuss …

The Meaning, Selection, And Use Of The Peridynamic Horizon And Its Relation To Crack Branching In Brittle Materials, Florin Bobaru, Wenke Hu

Florin Bobaru Ph.D.

This note discusses the peridynamic horizon (the nonlocal region around a material point), its role, and practical use in modeling. The objective is to eliminate some misunderstandings and misconceptions regarding the peridynamic horizon. An example of crack branching in a nominally brittle material (homalite) is addressed and we show that crack branching takes place without wave interaction. We explain under what conditions the crack propagation speed depends on the horizon size and the role of incident stress waves on this speed.

Convergence, Adaptive Refinement, And Scaling In 1d Peridynamics, Florin Bobaru Ph.D., Mijia Yabg Ph.D., Leonardo F. Alves M.S., Stewart A. Silling Ph.D., Ebrahim Askari Ph.D., Jifeng Xu Ph.D.

Florin Bobaru Ph.D.

We introduce here adaptive refinement algorithms for the non-local method peridynamics, which was proposed (in J. Mech. Phys. Solids 2000; 48:175–209) as a reformulation of classical elasticity for discontinuities and long-range forces. We use scaling of the micromodulus and horizon and discuss the particular features of adaptivity in peridynamics for which multiscale modeling and grid refinement are closely connected. We discuss three types of numerical convergence for peridynamics and obtain uniform convergence to the classical solutions of static and dynamic elasticity problems in 1D in the limit of the horizon going to zero. Continuous micromoduli lead to optimal rates of …

Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.

Florin Bobaru Ph.D.

The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as ‘long-range’. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical …

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.

Florin Bobaru Ph.D.

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

Continuum Modeling On Size-Dependent Properties Of Piezoelectric Nanostructures, Zhi Yan

Electronic Thesis and Dissertation Repository

Piezoelectric beam- and plate-based nanostructures hold a promise for device applications in the nanoelectromechanical systems (NEMS) due to their superior mechanical and electromechanical coupling properties. “Small is different”, nanostructured piezoelectric materials exhibit size-dependent properties, which are different from their bulk counterparts. For predicting the unique physical and mechanical properties of these novel nanostructures, continuum mechanics modeling has been regarded as an efficient tool. However, the conventional continuum models fail to capture the size effects of nanostructures and thus are not directly applicable at the nanoscale. Therefore, it is necessary to develop modified continuum models for piezoelectric nanostructures by incorporating the …

Reliability-Based Design Optimization Of Concrete Flexural Members Reinforced With Ductile Frp Bars, Bashar Behnam, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

In recent years, ductile hybrid FRP (DHFRP) bars have been developed for use as tensile reinforcement. However, initial material costs regain high, and it is difficult to simultaneously meet strength, stiffness, ductility, and reliability demands. In this study, a reliability-based design optimization (RBDO) is conducted to determine minimum cost DHFRP bar configurations while enforcing essential constraints. Applications for bridge decks and building beams are considered, with 2, 3, and 4-material bars. It was found that optimal bar configuration has little variation for the different applications, and that overall optimized bar cost decreased as the number of bar materials increased.

Loaded Shift Tester Sram, Nick Cox, Sam Shaffer, Michael Polka

Mechanical Engineering

This report details the design, manufacturing, and testing of a loaded shift tester for the SRAM Bicycle Corporation. The machine is used to perform developmental and qualification tests on various bicycle drivetrain components. Using SolidWorks, the design team created a solid model of the machine on the computer, then ordered and manufactured the parts required to build it. The machine was tested to ensure that all the parts worked together, and was finally delivered to SRAM when it was deemed ready.

Hoist To Transfer Athletes From Wheelchair Into A Kayak, Jennifer Batryn, Javier Mendez, Kyle Mooney

Mechanical Engineering

No abstract provided.

Adaptive Golf Device, Nick Baker, Katie Delaurentis, Grant Martens, Liz Allison

Mechanical Engineering

Our primary objective was to design a golf device that enables its user, who has limited leg movement and control, to be able to produce a balanced golf swing. Ultimately, the device maximizes the golfer's independence, and increases the accuracy of and power behind each shot. Specifically, the device was designed around the needs and requirements of Dr. Joshua Pate, Professor of Adapted Recreation at James Madison University. Dr. Pate has cerebral palsy limiting his lower body mobility and making it difficult for him to produce a balanced golf swing.

Exploration Station Kidshake Table, Jeremy Duhe, Philip Hopkins, Matt Ostiguy, Samantha Weiner

Mechanical Engineering

The KIDShake Table is an all mechanical earthquake shake table sponsored by the Exploration Station Children's Museum of Grover Beach. This interactive exhibit has two working mechanisms, a hand crank and pull rope, that provide two axis movement for knocking down block structures. This table was built and designed for a target age of 10 years.

Drape Forming Machine, Adam Johnson, Will Schlosser, Brian Miller

Mechanical Engineering

The goal of this project was to build a prototype machine that formed multiple sheets of debulked pre-preg OOA carbon fiber into a 2-foot long trapezoidal shape. The machine was required to do this process semi-automatically.

Bicycle Wheel Test Machine, Dylan Harper, Kevin Hom, Ross Williams

Mechanical Engineering

In recent years, the cycling industry has witnessed huge advancements in bicycle components and materials. The age old goals of speed and low weight are still present today, but the pursuit of these goals may be reducing the structural stability of various components integral to wheel performance, including the wheel hub bearings. These bearings are invaluable to bicycles but little is known about how the forces and loads applied to a bicycle affect the performance of these bearings. Broken axles and hubs are indicators of significant stresses within the hub, but little is known about how the resulting deformation affects …

Dedion Axle Senior Project, Nick Schraan, Mark Shushnar, William Swenson, Ramy Tall

Mechanical Engineering

The sponsor, EV Grid Inc. is a company looking to the future with the development of a vehicle to grid infrastructure. The vehicle in development is a Ford E-250 Van which had been converted to electric drive with a front motor, rear drive layout. The sponsor wanted to move the electric motor to the rear and develop an axle to support this change. By eliminating the driveshaft, a more efficient use of battery space could be utilized. The goal of this project is to design and fabricate a prototype deDion rear axle which incorporates a system of drive components that …

Multilink Suspension & Steering System For Cal Poly Formula Electric, Tristan French, Alissa Roland, Maximilian Sluiter

Mechanical Engineering

The purpose of this project was to design a suspension that would improve the performance of the Cal Poly SAE Formula Electric car around a racing track Performance would be quantified through skidpad, slalom, and straight-line acceleration tests as well as autocross lap times. The approach to meeting the objective was to increase the steady-state lateral acceleration and quicken the transient response while maintaining predictable handling so that the driver could extract maximum performance from the car.

The car uses round-section (motorcycle) tires at a large negative camber angle because the lateral force generated by a pair of negatively-cambered tires …

Evs Sports Knee Brace Testing Machinefinal Design Report, Silvia Aguilar, Nick Mattison, Chris Mccarthy

Mechanical Engineering

The purpose of this document is to report on the development of a test machine for EVS’ Web and Axis knee braces. Between September 2012 and June 2013, Team CSN, comprising of Nick Mattison, Silvia Aguilar, and Chris McCarthy, have methodically planned, designed, built, and tested this machine. The overarching goal of this unique machine is to address the need for both hyperextension and fatigue testing. From here on out this report dives into details of the machine with an Appendix C reporting testing results of said knee braces.

Rapid Decompression Containment System, Evan Domingue, Michelle Rudney, Daniel Trees

Mechanical Engineering

Cal Poly students; Evan Domingue, Michelle Rudney and Daniel Trees; are working with General Atomics Aeronautical Systems, Inc. (GA, ASI) and engineer John Wilcox to complete a senior project. The senior project is focused on finding a solution to meet the requirement set forth in MIL-HDBK 1791 4.2.5.2 for rapid decompression which requires cargo items to be designed with pressure relief devices or to be configured for air shipment as to prevent any part from becoming a projectile in the event of catastrophic loss of aircraft cabin pressure. The goal of this project is to design a safe, cost-effective, and …

Rebounder Fatigue Test Machine, Caroline Reeves, Will Robertson, Ethan Flory

Mechanical Engineering

JumpSport, a company that designs and sells trampolines and trampoline accessories, has sponsored this senior project team to design, build, and test a trampoline fatigue test machine. The machine must simulate a person jumping on the trampoline to test the life of JumpSport’s fitness trampolines and kids’ trampolines. Partway through the design process, the objectives were altered and this senior project team was tasked with merging with another Cal Poly senior project group to create an all-inclusive test machine to accommodate both full-trampoline testing and individual bungee cord testing.

The final design is centered on a slider crank linkage driven …

Design, Fabrication, And Testing Of An Emr Based Orbital Debris Impact Testing Platform, Jeffrey J. Maniglia Jr.

Master's Theses

This paper describes the changes made from Cal Poly’s initial railgun system, the Mk. 1 railgun, to the Mk. 1.1 system, as well as the design, fabrication, and testing of a newer and larger Mk. 2 railgun system. The Mk. 1.1 system is developed as a more efficient alteration of the original Mk. 1 system, but is found to be defective due to hardware deficiencies and failure, as well as unforeseen efficiency losses. A Mk. 2 system is developed and built around donated hardware from the Naval Postgraduate School. The Mk. 2 system strove to implement an efficient, augmented, electromagnetic …

Design And Fundamental Understanding Of Minimum Quantity Lubrication (Mql) Assisted Grinding Using Advanced Nanolubricants, Parash Kalita

Graduate Theses and Dissertations

Abrasive grinding is widely used across manufacturing industry for finishing parts and components requiring smooth superficial textures and precise dimensional tolerances and accuracy. Unlike any other machining operations, the complex thermo-mechanical processes during grinding produce excessive friction-induced energy consumption, heat, and intense contact seizures. Lubrication and cooling from grinding fluids is crucial in minimizing the deleterious effects of friction and heat to maximize the output part quality and process efficiency. The conventional flood grinding approach of an uneconomical application of large quantities of chemically active fluids has been found ineffective to provide sufficient lubrication and produces waste streams and pollutants …

Design Of Experimental Methods To Test The Performance Of Pads And Helmets Under Blast Loading Conditions, Kurtis Palu

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Improvised explosive devices (IEDs) have become a primary weapon in conflicts against US and allied forces. Improvements in body armor and medicine have increased the survivability of such events. These factors have caused an increase in traumatic brain injury (TBI) and mild traumatic brain injury (mTBI) induced by primary blast waves. Injury mechanisms caused from primary blast waves are not clearly understood or defined. How primary blast waves interact with materials or between narrow gaps found between helmet pads is not known. Two novel test fixtures were developed to provide a basic understanding of these two issues.

The first fixture …

Transient Small Wind Turbine Tower Structural Analysis With Coupled Rotor Dynamic Interaction, George R. Katsanis

Master's Theses

Structural dynamics is at the center of wind turbine tower design - excessive vibrations can be caused by a wide range of environmental and mechanical sources and can lead to reduced component life due to fatigue, noise, and impaired public perception of system integrity. Furthermore, periodic turbulent wind conditions can cause system resonance resulting in significantly increased structural loads. Structural vibration issues may become exacerbated in small wind applications where the analytical and experimental resources for system verification and optimization are scarce. This study combines several structural analysis techniques and packages them into a novel and integrated form that can …

Vulnerability Of Progressive Collapse In Reinforced Concrete Flat-Plate Buildings, Jinrong Liu

College of Engineering: Graduate Celebration Programs

• Progressive collapse is the spread of initial local failure, causing partial or
  even total collapse of a building.
• Flat plate structure is widely used for office and residential buildings.
• There is a large inventory of older flat plate building without continuous slab bottom reinforcement through columns.
• Limited knowledge exists regarding the risk of disproportionate collapse in
  older flat-plates under sudden column removal during abnormal events.
• Reliable mechanical model is needed for structural evaluation.

Application Of Higher Order Hamiltonian Approach To Nonlinear Vibrating Systems, Hassan Askari

Hassan Askari

No abstract provided.

Enhanced Nucleate Boiling On Horizontal Hydrophobic-Hydrophilic Carbon Nanotube Coatings, Xianming Dai, Xinyu Huang, Fanghao Yang, Xiaodong Li, Joshua Sightler, Yingchao Yang, Chen Li

Faculty Publications

Ideal hydrophobic-hydrophilic composite cavities are highly desired to enhance nucleate boiling. However, it is challenging and costly to fabricate these types of cavities by conventional micro/nano fabrication techniques. In this study, a type of hydrophobic-hydrophilic composite interfaces were synthesized from functionalized multiwall carbon nanotubes by introducing hydrophilic functional groups on the pristine multiwall carbon nanotubes. This type of carbon nanotube enabled hydrophobic-hydrophilic composite interfaces were systematically characterized. Ideal cavities created by the interfaces were experimentally demonstrated to be the primary reason to substantially enhance nucleate boiling

Computational Dynamics For The Flexible Multi-Body System, Yu Liu

Mechanical & Aerospace Engineering Theses & Dissertations

Research in computational dynamics has tremendously developed in the recent years because of the demand for analysis and simulation of various multi-body systems in the growing bio-medical, mechanical and aerospace industries. These multi-body systems are made of individual bodies that are interconnected via mechanical joints. Mathematically, these joints that connect the bodies can be described as constraint equations imposed upon the motions of the involved free bodies. This process will result in an equation of motion expressed in the form of a differential-algebraic equation (DAE). This is one of the main difficulties when dealing with the multi-body system because these …

Mechanics Of Blast Loading On Post-Mortem Human And Surrogate Heads In The Study Of Traumatic Brain Injury (Tbi) Using Experimental And Computational Approaches, Shailesh Govind Ganpule

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Blast induced neurotrauma (BINT) has been designated as the “signature injury” to warfighters in the recent military conflicts. The occurrence of traumatic brain injury (TBI) in blasts is controversial in the medical and scientific communities because the manifesting symptoms occur without visible injuries. Whether the primary blast waves alone can cause mechanical insult that is comparable to existing traumatic brain injury thresholds is still an open question, and this work is aimed to address this issue.

In the first part of this dissertation, mechanics of primary blast loading on Realistic Explosive Dummy (RED) head with and without helmets is studied …

Finite Element Simulation Of Wind Turbine Aerodynamics: Validation Study Using Nrel Phase Vi Experiment, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs

Ming-Chen Hsu

A validation study using the National Renewable Energy Laboratory (NREL) Phase VI wind turbine is presented. The aerodynamics simulations are performed using the finite element arbitrary Lagrangian–Eulerian–variational multiscale formulation augmented with weakly enforced essential boundary conditions. In all cases, the rotor is assumed to be rigid and its rotation is prescribed. The rotor-only simulations are performed for a wide range of wind conditions, and the computational results compare favorably with the experimental findings in all cases. The sliding-interface method is adopted for the simulation of the full wind turbine configuration. The full-wind-turbine simulations capture the blade–tower interaction effect, and the …

Analysis Of Alternative Ductile Fiber-Reinforced Polymer Reinforcing Bar Concepts, Bashar Behnam, Christopher D. Eamon

Civil and Environmental Engineering Faculty Research Publications

Steel-reinforced concrete structural components are often associated with significant maintenance costs as a result of reinforcement corrosion. To mitigate this problem, fiber-reinforced polymer (FRP) bars have been used in place of traditional steel reinforcement for some applications. The non-ductile response of typical FRP bars is a concern, however. To overcome this problem, hybrid ductile FRP (HDFRP) bars have been developed for use in concrete flexural members with resulting ductility indices similar to sections reinforced with steel. In this study, five different HDFRP bar concepts are analyzed and compared in terms of ductility, stiffness, and relative cost. Of primary interest is …