V3331026_2nd_Attempt_SOW.pdf

Request for Quote No. DTRT5717Q80090

PR # V3331026

Department of Transportation Volpe National Transportation System Center

Ductile Fracture of Stainless Steel Rail Equipment

Statement of Work

1. Introduction

The Volpe Center has ongoing projects sponsored by the Federal Railroad Administration (FRA) to examine the crashworthiness and structural integrity of railroad equipment for commodity transport of liquefied natural gas (LNG) and tenders used to carry and supply LNG as a fuel to adjacent locomotives. Prototypes of fuel tenders are currently being tested by Union Pacific Railroad, BNSF Railway, and Florida East Coat Railway (FECR). FECR is planning to transport LNG as a commodity using intermodal UN-T75 ISO tanks in well cars, with one tank per car.

The Alaska Railroad is currently transporting LNG with two ISO tanks per flat car. LNG transport by rail, both as a commodity and as a fuel, is expected to increase in the coming years.

There is concern for the integrity on tanks during train accidents. Traditional railroad tank cars have been involved in accidents where puncture of the tanks occurred due to car-to-car impacts.

Such impacts have occurred when a long freight train derailed, the train buckled, and the couplings between cars broke. Tank punctures have occurred due to impacts to the tank from stiff underframe components of other cars. Such an accident occurred in the town of Lac Mégantic, Quebec, Canada on July 6, 2013. Forty-seven people were fatally injured due to the derailment and subsequent fire. The train included seventy-two tank cars filled with crude oil.

The principal method for evaluating the crashworthiness of rail equipment includes development of accident scenarios of concern and analysis of the performance of the rail equipment in the scenarios. Such analyses can range from simplified physics-based models to detailed computer simulations. Results from such simulations and analyses can include information on the integrity of the tank, the decelerations experienced by the equipment, and the trajectory of the equipment.

Being able to accurately calculate material failure is essential in analyzing whether or not a tank ruptures in an accident scenario. Material failure is a complex phenomenon; a great deal of simplification is often made in order to be able to estimate material failure. Such simplifications necessarily compromise the accuracy of the material failure analysis. There is a need to develop high fidelity material failure algorithms and procedures for accurately evaluating the potential for tank rupture in train accidents. Such procedures must necessarily include testing, in order to validate the analysis models, and strongly connect the analysis results to reality.

2. Objective

The objectives of this effort are to measure and map the material failure envelope for the stainless steel used in cryogenic tanks, to develop closed-form algorithm for calculating tank rupture load, and to develop scale-model test conditions for measuring tank rupture load.

3. Tasks

The work in the following task descriptions will be performed:

Task 1: Calibration of plasticity and fracture initiation of stainless steel The contractor shall conduct a comprehensive experimental program to characterize the stainless steel used in LNG tank manufacturing. The contractor shall cut and prepare all needed specimens from the samples provided. All plasticity and fracture test specimens for this task shall be extracted from a single parent material sample with their loading axes aligned in three different directions: 0, 45, and 90 degrees. At least two samples shall be extracted for each direction. At least four types of tests shall be conducted. Each type of test shall be conducted at least six times- twice for each of three directions. All tests will be simulated with FEA models using the plasticity and fracture algorithm proposed by the contractor. Results from this task include the measured force-displacement curves and the stress-strain curves derived from the test data, including large strains. Parameters required for the simulations shall be calibrated from the test measurements according to the contractor’s established procedures. Simulation results shall include the load (stress) path to fracture for each test. This approach shall include an algorithm for computing the material fracture initiation envelope, detailed requirements for material plasticity and fracture tests, prescriptions for simulating the tests, and criteria for comparing simulation predictions and test measurements.

Task 2: Calibration of fracture propagation and validation on fracture mechanics specimens The contractor shall develop experimental test on fracture mechanics specimens ranging from typical high-constraint compact tension specimens to low-constraint tension specimens. This type of test will assess ductile tearing resistance of the material under quasi-static loading condition with stable crack propagation. Based on the model parameters calibrated in previous task for fracture initiation, ductile crack propagation parameters are adjusted by means of strain softening approach adequately implemented in contractor’s algorithm. By selecting only one geometry, the strain softening parameters are adjusted for large crack extension including blunting, initial and stable crack propagation. Validation will be performed on the remaining specimen geometries previously selected with the sponsor preferences.

Task 3: Effect of temperature on material behavior LNG has a temperature of -260 oF at atmospheric pressure. Consequently, the temperature of the inner tank material of the LNG container can approach -260 oF. At -260 oF the ductility and of the material properties of the stainless steel used for the inner tank material are expected to be substantially different from those properties at room temperature. The contractor shall conduct a limited testing program at low temperature for the given material and its corresponding model parameters will be implemented into a user defined subroutine for industrial purposes.

Task 4: Close-form solution for tank car puncture Three important extensions of the Suh and Wierzbicki analytical solution for local indentation of cylinders will be made, the contractor shall evaluate:

i. The effect of the partially filled tank with an inert gas at the top will be included using the concept of the added mass in fluid-solid interaction. A relative contribution of the strength of the cylinder wall, fluid inertia and compression of gas will then be estimated.

ii. The critical indentation depth for fracture initiation and the first phase of tearing of the wall will be determined using the simplified kinematics of the dented area and the concept of plain strain critical fracture.

iii. Finally, a strain rate correction factor will be introduced to relate critical indentation depth to the impact velocity on a tank car.

Task 5: Intermediate scale test requirements and numerical simulations The contractor shall develop test requirements for an intermediate-scale quasi-static test. For the test, the tank shall be placed on a flat surface, and slowly dented and punctured by a blunt needle-like impactor, which impinges on the center of the tank. The impactor shall have a square face, which is 12 inches x 12 inches with ½ inch edge-radius when fullscale. The contractor shall determine support conditions which allow stable application of the load. The test article description shall be developed from parametric studies, using the closed-form solution developed in Task 3 and finite-element analyses. Starting from a double-walled pressure vessel of railroad service size, the contractor shall analyze fullscale, ¼ scale, 1/8, and 1/16 scale models. The dimensions to be scaled include the external dimensions of the tank, the internal pressure of the tank, and the face of the impactor. The same material shall be modeled for all scales. Tank wall thickness shall be parametrically varied in the sub-scale analyses, to compensate for the inability to scale material properties. Comparisons shall be made of the normalized force-displacement characteristics. Impactor force shall be normalized to the force needed to rupture the tank;

impactor displacement shall be normalized to the diameter of the tank. The scaled-model tank thickness which results in a reasonably close match to the normalized full-scale force-displacement characteristic shall be selected. Qualitative comparisons shall be made of the modes of deformation, and shall be considered in selecting the scale and thickness of the test article. These test requirements shall include a detailed description of the test article, a description of the loading condition, and a description of the critical test measurements.

5. Deliverables

Reporting Requirements

1. Technical Reports/Technical Notes

The results of these studies shall be described in presentations or final report. Publication and distribution of all reports and other documents produced as a result of this effort are at the sole discretion of the U.S. Government. The reports will be delivered according to the timeline detailed in Table 1. The results of the tasks are to be described in four presentations and a report. The Contractor acknowledges the Government's support in the publication of any material based on or developed under this contract, stated in the following terms: This material is based upon work supported by the Department of Transportation Volpe Center under the awarded Purchase Order.

All material, except scientific articles or papers published in scientific journals, must, in addition to any notices or disclaimers by the Contractor, also contain the following disclaimer: Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of Transportation Volpe Center. In addition, the Volpe Center will be given a fourteen day review period of any publication by contractor as a result of these studies.

Table 1 Description of Deliverables

Task Deliverable Contents Due Date Task 1 Presentation/MS

Power Point Test and simulation requirements for fracture initiation.

Criteria for comparing simulation results and test measurement.

Measured force vs displacement graphs for all tests.

Simulated load path to initiation for all tests.

September 01, 2017

Task 2 Presentation/MS Power Point

Test and simulation requirements for crack propagation.

Criteria for calibration parameters using fracture mechanics specimens.

Mesh size effect on resistance tearing curves (R-curves).

January 01, 2018

Task 3 Presentation/MS Power Point

Scope and limitations of the proposed analytical solution.

Simplified model of fluid-structure interaction including inert gas effect.

Critical indentation depth for fracture initiation in static

April 01, 2018

Task 4 Presentation/MS Power Point

Requirements for sub-scale tests.

Dimensional analysis for scaling down full scale tests to intermediate one.

August 01, 2018

Task 5 Presentation/MS Power Point

Test and simulation requirements for fracture initiation.

Criteria for comparing simulation results and test measurement.

Measured force vs displacement graphs for all tests.

Simulated load path to initiation for all tests.

December 01, 2018

2. Quarterly Summary Management Status Report For the duration of the period of performance, the contractor shall prepare and submit within 15 days of the end of each quarter (three month period) an electronic copy of a Quarterly Summary Management Status Report. There shall be a total of six (6) reports for the 18 month/6 quarter period of performance. The monthly report shall present a brief description of the progress of the contract, including work accomplished during the reported month, problem areas encountered, action(s) taken, and work planned for the next reporting period. Status Reports shall be emailed to the Technical Point of Contact in MS Word format or Adobe Acrobat format files.

3. Meetings and Oral Presentations The contractor shall meet with the Technical Point of Contact every eight weeks at the contractor’s site to keep the Technical Point of Contact informed and up to date on the progress of work. Meetings shall take place at mutually agreed upon dates and times. Meetings are expected to last approximately 2 hours. The invitees for such meetings will be at the sole discretion of the U.S. Government. There shall be a total of nine (9) meetings for the 18 month period of performance.

4. Software All software developed to perform the tasks and develop the information used to complete the study in accordance with the statement of work is a deliverable. The software deliverables shall not require any additional proprietary software (i.e., in-house compilers, interpreters, or applications software that is not commercially available) in order to execute and be employed as an analysis tool. Commercially available software may be used to develop the software deliverables. Copies of all software developed; including

6. Acceptance

All deliverables shall be delivered in electronic form, MS PowerPoint for any presentations, MS Word for the final report, MS Word or Adobe Acrobat for the Status Reports, and native format for any software. Presentations and reports shall be emailed to the Technical Point of Contact. All software developed in the performance of this statement of work shall be delivered to the Technical Point of Contact on a memory stick by the final monthly meeting.

7. Period of Performance

The period of performance for this purchase order is May 08, 2017 - December 01, 2018.

8. Place of Performance

The place of performance is the contractor's facilities on the MIT campus, 77 Massachusetts Avenue, Cambridge, MA 02139.

9. Travel

No travel by the contractor is planned for this effort.

10. Technical Point of Contact

David Jeong, Senior Engineer Structures and Dynamics Division Volpe Center, V-333 55 Broadway Cambridge, MA 02142 617-494-3654 David.Jeong@dot.gov