Autoclave Upgrade for Corrosion Fatigue Testing

Expand the University of Idaho’s current fatigue testing capabilities to include an autoclave load frame that supports testing of metals as well as operating conditions experienced in nuclear power plants. =Problem Definition=

Background


The objective of this project is to expand the University of Idaho’s current fatigue testing capabilities to include an autoclave load frame for use in fatigue testing of materials with a focus in metals to be used in nuclear power plants. Currently, no system is on hand to accomplish the fatigue testing environment desired by Dr. Stephens. Currently, there are two load frames with furnaces capable of reaching temperatures up to 700°F, but neither of them have an airtight seal installed. The proposed new system will be able to tolerate temperatures of up to 750°F and 3000 psi while delivering 10,000 lbs of force.

Currently, the lab’s load frames can do fatigue creep testing in an air environment. Fatigue tests slowly apply a tensile load which tears apart a specifically shaped sample over an extended period. The growth rate of the crack is of interest because it is used to predict the lifespan of the material in other applications. The proposed system will perform the same style of tests but will be capable of testing the response of the material to corrosive and pressurized environments.

Deliverables
The scope of this project includes designing/purchasing all of the components for the fatigue testing apparatus, assembling it, and testing it for proper usability as defined in the following deliverables.

Initial Client Meeting & Expectations The initial client meeting was conducted on June 14th, 2018. Dr. Stephens and Nicholas Schaber prepared the following list of Primary Objectives for the project.
 * Load Frame Upgrades
 * Loading system (motor/drive/gearbox, rated to &asymp;10 kips)
 * Load cell (coinciding with applied loads)
 * Load cell calibrated in line with seal
 * Load train displacement measurement (LVDT)
 * Extension rates up to 0.05 mm/s
 * Lid lifting/holding device
 * Load Control and Measurement
 * Feedback control loop (load controlled)
 * User interface for load frame
 * Programmable loading waveforms including:
 * Variable strain rate
 * Fatigue (cyclic loading, variable frequencies)
 * Creep-fatigue (variable hold time and set loading)
 * Constant load
 * Crack measurement/monitoring (DCPD)
 * User interface over/under warnings (temp, pressure, load)
 * Autoclave Upgrades
 * High temperature/pressure dynamic seal
 * Lid modifications
 * Loading rod
 * Internal load support
 * Isolated through-lid fittings for DCPD wires
 * Operating temperature of 400&deg;C (&asymp;750&deg;F)
 * Operating pressure of 20MPa (&asymp;3000psi)

Specifications Utilizing the above list of deliverables from the client, a refined list of specifications has been produced. The full document is available in the "Additional Documentation" section.

The following is a shortened list of our most important specifications and deliverables.


 * Functionality
 * UI should emulate that of other load frame currently in use by U of I
 * Emergency stop function digitally via LabView UI and mechanically via physical “button”
 * Extension rates up to 0.05mm/s during testing
 * The loading system (motor/drive/gearbox) design shall be able to deliver a maximum load of at least 10,000 pounds.
 * Design shall be able to accommodate standard sized test specimens
 * All components shall have 99% reliability. A DFMEA will take this into account
 * Programmable loading waveforms including:
 * Variable strain rate
 * Fatigue (cyclic loading, variable frequencies)
 * Creep fatigue (variable hold time and set loading)
 * Constant load
 * Crack measurement/monitoring via DCPD


 * Evironmental Requirements
 * All internal autoclave components shall be designed to withstand temperatures of at least 300° C
 * All internal autoclave components and seals shall be designed to withstand pressures of at least 28MPa (4000 psi)
 * All internal autoclave components and seals shall be designed to withstand the same corrosives as the 316H stainless steel that the autoclave is made of

Acronyms used in this text
 * UI:  User Interface
 * LVDT: Linear Variable Differential Transformer
 * DCPD: Direct Current Potential Drop

=Project Learning=

Dynamic Seal
With the design shown in Figure 1, a rod is moved linearly through the top of the autoclave pressure chamber. This requires a strong, Dynamic Seal to handle the movement of the rod while containing the required maximum temperature, pressure, and corrosive environment.

Actuation System
Referring again to Figure 1, an Actuator System is needed to raise and lower the gripper arm attached to the test specimen. This system needs to be robust enough to provide the test loads required for fatigue testing of the specimen.

Hydraulic
 * Advantages
 * Capable of delivering faster load frequencies (15-60 Hz)
 * Higher max speed ramp up rate and turnaround rate
 * Significantly less expensive
 * More commonly available components
 * Disadvantages
 * Requires an external pump and cooling
 * Larger amount of individual components

Electric
 * Advantages
 * Simpler system (less individual components)
 * Smaller footprint in lab
 * Disadvantages
 * More expensive overall
 * Slower load frequency capabilities (~1 Hz)
 * Lower Lifetime

Decision Matrix In order to make an informed decision on the type of actuation system we needed to purchase, a decision matrix was created. The categories, weights, and values of the matrix were all discussed and agreed upon by the team as a whole. Using this decision matrix, we were able to easily settle on a hydraulic actuation system as our best candidate for this project.

=Prototyping=

=Validation=

=Final Design=

=Team Members=

=Additional Documentation= Presentations File:2018 AutoclaveExperts DesignReviewPresentation.pdf File:2018_AutoclaveExperts_Snapshot2Storyboard.pdf

Documents

Project Schedule

File:2018_AutoclaveExperts_GanttChart8-1-18R4.pdf

Meeting Minutes

File:2018 AutoclaveExperts MeetingMinutes.pdf

Product Requirements

File:2018_AutoclaveExperts_ProductRequirementsR3.pdf

Client Interview

File:2018_AutoclaveExperts_QuestionsForClient.pdf

Team Contract

File:2018_AutoclaveExperts_TeamContract.pdf