Performance Work Statement_SS.pdf

PERFORMANCE WORK STATEMENT

Mechanical and Environmental Cracking Testing Services for Aluminum Coupons

Rev. 2-26-2021

1.0 Scope

NSWCCD Code 612 is assisting the Unmanned Maritime Systems (UMS) Program

Office, PMS 406, to analyze the properties of forgings produced from aluminum alloys

7175-T74 and 6061-T6. Mechanical properties must be determined in air to validate that forging properties are within program specifications. Environmental fracture performance must also be evaluated in representative forgings to inform component service life. Only sparse fracture properties data for saltwater exposure are available in literature because these materials are typically used for aerospace and ground transportation applications.

Prior demonstration conducted under Contract N0016718P0270 (FY18 award) confirmed that testing capability exists to rapidly determine the environmentally assisted fracture properties of aluminum material. The current work will utilize the same or similar test methods to conduct more thorough evaluation on the same, in addition to traditional mechanical testing in laboratory air. In the 2.5 years since the prior contract, Code 612 now understands that multiple commercial vendors with environmental and fracture testing expertise can conduct similar testing based on our improved understanding of the test parameters and expected material properties/ response. Code 612 has also conducted similar testing in-house on these materials. These experimental results are urgently needed to inform ongoing design analyses and risk assessments.

2.0 Background

The primary objective of this contract is to determine the mechanical properties of various

7175-T74 and 6061-T6 forgings in air, as well as to determine the fracture properties in saltwater using accelerated fracture mechanics test methods. The most critical material performance parameter to be determined is the “threshold stress intensity factor (K) for environmentally assisted crack growth”, referred to herein as KI-EAC. Data are also needed that quantify environmentally-assisted crack growth rates (referred to as da/dt) that occur in seawater once K exceeds KI-EAC. These critical environmental cracking metrics may be measured through use of (1) a direct current potential difference (dcPD) system, which measures crack length during testing to calculate K, or (2), specific strain gauging installations on test specimens, wherein collected data are mainly analyzed through back-calculation after testing and fractographic analysis is complete. The KI-EAC test operates by holding a constant K at various levels until minimal environmental crack growth is measured, with total test duration not to exceed 8 weeks. This test duration is significantly reduced compared to an alternative method utilized in the past for aluminum alloys (e.g.

ASTM E1681), which requires a minimum of 10,000 hours (about 14 months) and numerous specimens to generate a single KI-EAC value. For KI-EAC value comparison, the

ASTM E1681 test will be included in the test program on a limited basis. The da/dt test is performed under slowly-rising displacement or K control to test the sample at all stress intensities above KI-EAC, and measure the environmentally-assisted crack growth rate. The da/dt test duration shall not exceed 4 days.

Environmental fracture testing shall form the base of the contract and shall be performed by the prime Contractor, and standard mechanical testing may be performed according to options, as defined in Table 1.

Table 1. Test types and quantities for Contractor testing services option test type / standard minimum quantity maximum quantity notes

Base compact tension, C(T)

Type A

(rising-displacement/K test)

20 80 Prime contractor shall perform all tests

Base compact tension, C(T)

Type C

(constant-K test)

10 36 Prime contractor shall perform all tests

Base compact tension, C(T)

Type D

(deadload test)

20 40 Prime contractor shall perform all tests

Tension Testing

ASTM E8

0 500

Compression Testing

ASTM E9

0 500

Elastic Modulus

ASTM E111

0 200 compact tension, C(T)

Type B

(J-integral test)

0 350 most expected to be at room temperature, up to

50% may be at cold temperature precrack C(T) specimens in fatigue 50 506 pre-cracking parameters will be specified in Task

Orders, max. qty at the limit of all C(T) samples side-groove machining of

C(T) specimens 50 506 side-groove parameters will be specified in Task

Orders

The contract shall be awarded in the form of an indefinite delivery, indefinite quantity

(IDIQ), wherein the Base is guaranteed within the specified test specimen ranges and the

Options presented in Table 1 may be exercised within the contract period of performance

(POP). All exercised options shall be executed such that the requested tasking can be completed before closure of the POP.

3.0 Applicable Documents

The following specifications and standards form a part of this contract to the extent specified herein. The version of the specification or standard shall be the most recent version issued at the time of contract award, unless otherwise specified.

In the event of a conflict between the text of this document and the references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.

3.1 ASTM E 8/E8M, Standard Test Methods for Tension Testing of Metallic Materials

3.2 ASTM E9, Standard Test Methods of Compression Testing of Metallic Materials at

Room Temperature

3.3 ASTM E83, Standard Practice for Verification and Classification of Extensometer

Systems

3.4 ASTM E111, Standard Test Method for Young’s Modulus, Tangent Modulus, and

Chord Modulus

3.5 ASTM E340, Standard Practice for Macroetching Metals and Alloys

3.6 ASTM E399, Standard Test Method for Linear-Elastic Plane-Strain Fracture

Toughness KIC of Metallic Materials

3.7 ASTM E647, Standard Test Method for Measurement of Fatigue Crack Growth Rates

3.8 ASTM E1681, Standard Test Method for Determining Threshold Stress Intensity

Factor for Environment-Assisted Cracking of Metallic Materials

3.9 ASTM E1820, Standard Test Method for Measurement of Fracture Toughness

3.10 ISO/IEC 17025, General Requirements for the Competence of Testing and

Calibration Laboratories

3.11 NIST Technical Note 1679, “Repeatability and reproducibility of compression strength measurements conducted according to ASTM E9”, Sep 2009

4.0 General Requirements

4.1 Contractor’s Progress, Status and Management Report

The Contractor shall provide a monthly status report. The report shall include a summary of work completed, work schedule status, planned work for the next month, problem areas with proposed solutions, funding expended (current period and cumulative), and remaining balance. The monthly status report shall include input from the prime Contractor as well as all associated sub-Contractors as applicable.

(CDRL A001)

4.2 Test Laboratory Certification

The Contractor, and Sub-Contractors as applicable, shall be responsible for maintaining NADCAP certification A2LA to ISO/IEC 17025, and/or alternative certifications as approved by the Government, for all services provided as part of this contract for the full contract period of performance.

5.0 Testing of Machined Specimens

5.1 General Testing Requirements

5.1.1 The Contractor or Sub-Contractors, if applicable, shall conduct testing of machined specimens as specified in the Task Orders issued by NSWCCD, with quantities for Contractor testing as provided by Table 1. The testing shall be conducted according to the requirements of Section 6.0 and the

Task Orders.

5.1.2 The Contractor and sub-Contractors, if applicable, shall notify the

Government via e-mail when recalibration/recertification of test equipment used in the performance of the contract occurs.

5.1.3 The Contractor and sub-Contractors, if applicable, shall be responsible for initiating mechanical testing within five (5) business days of the date that the samples are received, or in a timeframe approved by the Government prior to the shipment of samples.

5.2 Specimen Pre-cracking and Side-Groove Machining

5.2.1 Specimens requiring a pre-crack prior to mechanical testing will be identified in the Task Orders. The Contractor or Sub-Contractors, if applicable, shall prepare each test specimen as required by pre-cracking the starter notch in fatigue. This process may be conducted in ambient air. The

Contractor or Sub-Contractors, if applicable, shall precrack in accordance with parameters provided in the Task Order for each specimen.

5.2.2 Specimens requiring side-grooves prior to mechanical testing will be specified in the Task Orders. The Contractor or Sub-Contractors, if applicable, shall machine side-grooves into the specimens as required after completion of pre-cracking, with dimensions as specified in the Task Order for each specimen.

5.3 Detailed Testing Requirements

5.3.1 Tensile Testing (ASTM E8/E8M, ASTM E83)

5.3.1.1 The Contractor or Sub-Contractor, if applicable, shall perform quasi-static tensile testing in accordance with ASTM E8/E8M.

5.3.1.2 The Contractor shall operate the testing machine in crosshead control with constant speed when determining yield properties, that is, “Method A” as described in ASTM E8/E8M-16a Section 7.6.4.1.

5.3.1.3 After yield behavior and strain of at least 5% have been recorded, the rate of testing may be increased in accordance with ASTM

E8/E8M-16a Section 7.6.5.

5.3.1.4 The Contractor shall use an extensometer of Class B-2 or better for extension measurement (see ASTM E83-16), and at least 5% strain shall be recorded. The recording of strain until the maximum load is preferred.

5.3.1.5 The test temperature for tensile specimens shall be room temperature, unless otherwise specified by Task Order.

5.3.1.6 The Contractor shall handle fracture surfaces of broken specimens so as to prevent oxidation or other surface damage, and preserve by a light coat of lacquer that is soluble in a common solvent (e.g.

acetone or ethanol) shortly after the completion of testing.

5.3.2 Compression Testing (ASTM E9, ASTM E111, ASTM E83, NIST

Technical Note 1679)

5.3.2.1 The Contractor or Sub-Contractor, if applicable, shall conduct compressive strength tests in accordance with requirements of

ASTM E9 for displacement control (or “crosshead” control). The crosshead speed shall be set to achieve a strain rate in the elastic portion no greater than 0.005-inch/inch per minute.

5.3.2.2 The Contractor shall conduct compressive strength tests at constant crosshead speed until a total axial strain of at least 3.0% is reached.

5.3.2.3 The Contractor shall use contact extensometers of Class B-2 or better (see ASTM E83-16) s for determination of yield properties, per ASTM E9-09 Section 6.5.

5.3.2.4 Per ASTM E9-09 Section 9.2, if the modulus of elasticity (i.e.

Young’s Modulus) is the primary quantity to be determined, the

Contractor shall follow the test method of ASTM E111, including the use of Class B-1 or better contact extensometers. The need to determine the modulus of elasticity as the primary test quantity will be specified to the Contractor in the Task Order.

5.3.2.5 The Contractor shall position the attachment points of the extensometer(s) at distance of approximately one specimen diameter away from each end of the specimen. For example, the minimum length of a 0.5-inch diameter test specimen would be

2-inches, when using a 1-inch extensometer. For a 0.25-inch diameter sample, the minimum specimen length would be 1.0-inch when using a 0.5-inch extensometer.

5.3.2.6 The Contractor shall measure sample diameter and length with an accuracy of +/- 0.001-in., both before and after the compression test.

The final engineering strain should be compared to the final strain recorded by the extensometer during the test. Initial and final geometries shall be recorded and any discrepancies between measured strain and extensometer strain shall be reported.

5.3.2.7 The test temperature for compression specimens will be at room temperature, unless otherwise specified by Task Order.

5.3.2.8 Molybdenum disulfide or similar lubricant shall be used on the ends of the samples to reduce friction and potential for barreling effects.

5.3.2.9 The Contractor shall measure and verify that the bearing surfaces are parallel within 0.0002-inch/inch prior to the start of testing for each test frame used (See ASTM E9-09 paragraph 6.1.1.).

5.3.2.10 Two extensometers of the appropriate class, positioned diametrically opposed, shall be used for all Elastic Modulus tests.

The use of two diametrically opposed extensometers provides the most consistent strain measurement and elastic modulus.

5.3.3 In-air Fracture Toughness Test (ASTM E1820)

5.3.3.1 The Contractor or Sub-Contractor, if applicable, shall test compact tension specimens at a quasi-static rate according to the requirements of ASTM E1820. The specimen quantities, identification codes, and orientations will be specified by the Task

Order.

5.3.3.2 The Contractor or Sub-Contractor, if applicable, shall perform and record all measurements and calculations required by Section 10 of

ASTM E1820-17.

5.3.3.3 The test temperature will be specified by the Task Order. It is anticipated that most tests will be conducted at room temperature, although some tests may include temperature as low as 28F.

5.3.3.4 The Contractor shall ensure that pre-cracking and side-grooving has been accomplished per the Task Order, prior to conduct of fracture toughness testing per ASTM E1820.

5.3.3.5 The Contractor shall protect all specimen fracture surfaces from oxidation or other forms of physical damage, and return post-test samples to the Government if requested.

5.3.4 Environmentally Assisted Crack Growth, Rising Displacement/K Test

(non-standardized test method)

5.3.4.1 The Contractor shall test compact tension specimens at a slow, rising displacement- or K-rate. The testing rate of interest (i.e.

“dK/dt”) will be specified by the Government. The specimen quantities, identification codes, and orientations will be specified by the Task Order.

5.3.4.2 Testing shall be conducted with a specimen immersed in synthetic seawater or 3.5% saltwater solution, and other environmental conditions as specified by the Task Order, including temperature, pH, applied cathodic potential, and aeration.

5.3.4.3 The initial K during test shall be no greater than 5-ksi√in.

5.3.4.4 The test shall determine crack length and crack velocity (da/dt) during increase of the applied stress intensity factor, to at least 25-ksi√in. or as otherwise specified by the Task Order.

5.3.4.5 Crack growth shall be resolved at 1x10-8 mm/s or greater resolution, and crack length must be resolved at a minimum increment of 0.01 inch.

5.3.4.6 Rising Displacement/K testing shall not exceed 4 days per specimen.

5.3.5 Environmentally Assisted Crack Growth, Constant-K Test (non-standardized test method)

5.3.5.1 The Contractor shall test compact tension specimens to determine crack growth rate as a function of the applied K and environmental conditions. The specimen quantities, identification codes, and orientations will be specified by the Task Order.

5.3.5.2 Testing shall be conducted with a specimen immersed in synthetic seawater or 3.5% saltwater solution, and other environmental conditions as specified by the Task Order, including temperature, pH, applied cathodic potential, and aeration.

5.3.5.3 Testing shall begin using K-control to initiate a growing, environmentally assisted fatigue crack. Fatigue crack growth rate

(FCGR) and stress ratio shall be recorded to illustrate the effects of varying hold times and ramp times during this step.

5.3.5.4 Following observance of static crack propagation, the test shall transition using K-control to quasi-static loading by introducing longer hold times. Crack velocity (“da/dt”) shall be recorded as a function of the applied stress intensity factor.

5.3.5.5 The applied stress intensity factor shall be systematically decreased using K-control until the measured crack velocity is reduced to the target value of approximately 3x10-9 mm/s. The stress intensity factor corresponding to a sustained crack velocity of 3x10-9 mm/s or less shall be recorded as the observed value of the threshold for environmentally assisted crack growth (KI-EAC).

5.3.5.6 The testing system utilized to conduct the Constant-K test must be able to achieve crack growth resolution of 1x10-9 mm/s or greater resolution, and crack length must be resolved at a minimum increment of 0.001 inch.

5.3.5.7 KI-EAC values shall be recorded in K-control while varying the electrode potential over a range of -1100 to -850 mVSCE, unless otherwise specified by the Task Order.

5.3.5.8 Constant-K testing shall not exceed 8 weeks per test specimen.

5.3.6 Threshold Testing for Environmentally Assisted Crack Growth (ASTM

E1681)

5.3.6.1 The Contractor shall test compact tension specimens to determine the threshold stress intensity factor for environmentally assisted cracking according to the procedure of ASTM E1681 for aluminum. The specimen quantities, identification codes, and orientations will be specified by the Task Order. It is anticipated that testing to ASTM E1681 will commence after all rising displacement tests have been completed.

5.3.6.2 Testing shall be conducted with all specimens immersed in synthetic seawater or 3.5% saltwater solution for a continuous period of 10,000 hours, per Section 8.4 of ASTM E1681-03

(2013). Other requirements for environmental conditions, including temperature, pH, and cathodic potential, will be determined at a later date and specified in the Task Order.

5.3.6.3 Testing shall include a minimum of two applied K values below the expected threshold value, one applied K value equivalent to the anticipated threshold value, and two applied K values above the expected threshold value, unless otherwise specified by the Task

Order.

5.3.6.4 Each applied K level shall include a minimum of 4 test specimen replicates, unless otherwise specified by the Task Order.

5.3.6.5 Testing shall be conducting using a dead load. Loading methods including fixed displacement or bolt loading are prohibited.

5.3.6.6 Crack growth shall be measured using either the dcPD system or strain gauging throughout each ASTM E1681 test, achieving a minimum crack length measurement resolution of 0.01 inch or greater resolution.

5.3.6.7 The Contractor shall record all values and calculations as required by Section 10 of ASTM E1681-03 (2013).

6.0 Reporting of Materials Characterization Tests

6.1 General Reporting Requirements

6.1.1 The Contractor shall submit a report (CDRL A002) summarizing test results from each of the materials characterization tests performed by the

Contractor, or sub-Contractor as applicable. Reports shall comply with requirements contained in the applicable test specification and shall include sufficient detail so that readers can understand what test(s) was/were performed; key testing parameters utilized; issues encountered during testing, if any; corrective measures taken, if any; and results obtained.

6.1.2 Raw data for all materials characterization tests shall be submitted to the

Government as part of the testing reporting requirement (CDRL A003).

Raw data can be submitted within the testing summary report (see Section

6.1.1), as an appendix to the testing summary report (see Section 6.1.1), or as a separate deliverable (for example, document, spreadsheet, CD).

6.1.3 Materials characterization test reports (see Section 6.1.1) and raw data (see

Section 6.1.2) shall be submitted to the Government no later than 14 calendar days after completion of testing unless otherwise agreed to by the Government.

6.2 Detailed Reporting Requirements

6.2.1 Tensile Test Results (ASTM E8)

6.2.1.1 The following information from each tensile test shall be reported to the Government in accordance with CDRL A002 and CDRL

A003:

0.2% offset yield strength, which shall be determined by the method described in ASTM E8-16 Section 7.7.1.

Ultimate tensile strength.

Original gauge length, percent elongation, and reduction of area as determined by ASTM E8-16 Section 7.11.

Location of fracture, if applicable.

Stress-strain diagram.

Raw stress-strain data pairs and sensor measurements in tabular format (including elapsed time, load, displacement, and strain).

6.2.2 Compression and Modulus of Elasticity Test Results (ASTM E9/ASTM

E111)

6.2.2.1 The following information from each compression test shall be reported to the Government in accordance with CDRL A002 and

A003:

Modulus of elasticity, which shall be calculated as described in

ASTM E111-04 (Reapproved 2010) Section 9.2.

0.2% offset yield strength, which shall be determined by the method described in ASTM E9-09 (Reapproved 2018) Section 9.3.

Compressive strength at 2.0% axial strain, as described in ASTM

E09-09 (Reapproved 2018) Section 9.5.

Stress-strain diagram.

Raw stress-strain data pairs and sensor measurements in tabular format (including elapsed time, load, displacement, and strain).

6.2.3 In-air Fracture Toughness Test (ASTM E1820)

6.2.3.1 The Contractor shall record a photographic image of each fracture surface, suitable for visual identification of the pre-crack length and the final extent of crack propagation. The Contractor shall provide a final test report including results for all tests, recorded data, and fracture surface photographs in accordance with CDRL A002 and

A003. Results shall include all applicable values and measurements listed in Section 10 of ASTM E1820-17.

6.2.4 Environmentally Assisted Crack (EAC) Growth, Rising Displacement/K

Test (non-standardized test method)

6.2.4.1 Following testing, the Contractor shall determine and record the pre-crack length and final extent of crack propagation through examination of the fracture surface. The final extent of cracking during the test shall be marked by fatigue cycling prior to separating the specimen, if necessary.

6.2.4.2 The Contractor shall record a photographic image of each fracture the final extent of crack propagation. The Contractor shall provide a final test report including results for all tests, recorded data, and fracture surface photographs in accordance with CDRL A002 and

A003. Results shall include the J-R curve with power law fit, Jth, J0.2mm offset, J vs. da/dt, and all associated figures and tables.

6.2.5 Environmentally Assisted Crack Growth, Constant-K Test (non-standardized test method)

6.2.5.1 Following testing, the Contractor shall determine, record, and report the pre-crack length and final extent of crack propagation through examination of the fracture surface. The final extent of cracking during the test shall be marked by fatigue cycling prior to separating the specimen, if necessary.

6.2.5.2 The Contractor shall record a photographic image of each fracture the final extent of crack propagation. The Contractor shall provide a final test report including results for all tests, recorded data, and fracture surface photographs in accordance with CDRL A002 and

A003. Test results shall include the following:

Fatigue crack growth rates, stress ratio, and applied K and cathodic potentials during the initial fatigue cracking phase;

Observed threshold KI-EAC values and applied cathodic potentials as defined by 5.3.5;

Plot of crack size vs. time for the duration of the test;

Summary of all applied K values, polarization voltages, and computed crack growth rates (“da/dt”) for the duration of the test.

6.2.6 Threshold Testing for Environmentally Assisted Crack Growth (ASTM

E1681)

6.2.6.1 During testing, the Contractor shall use strain gauging or dcPD to collect crack growth data.

6.2.6.2 Following testing, the Contractor shall determine, record, and report the pre-crack length and final extent of crack propagation through direct examination of the fracture surface. The extent of cracking may be marked by fatigue cycling prior to separating the specimen, if necessary.

6.2.6.3 The Contractor shall record a photographic image of each fracture the final extent of crack propagation if possible. The Contractor shall obtain high magnification images for at least one specimen at every applied K-level via scanning electron microscopy (SEM) or other method suitable to identify the occurrence of EAC.

6.2.6.4 The Contractor shall provide a final test report including results for all tests, recorded data, and fracture surface photographs in accordance with CDRL A002 and A003. Test results shall include the pass/fail status of each specimen, any measured crack growth rates for failed specimens, as well as all other requirements of

Section 10 of ASTM E1681-03 (2013).

7.0 Government Furnished Information/Property (GFI/GFP)

7.1 GFI

Drawings of the First Article forgings and prolongs will be provided at the time of Contract/Option Award.

Drawings for all mechanical test specimens, including requirements for dimensions, tolerances, and surface finishes as applicable.

Drawing of the mock-up to be machined from a FAT unit to support nondestructive testing. (Section 4.6.11)

NIST Technical Note 1679 (Section 6.3.2.8)

7.2 GFP

Full scale forgings, prolong remnants, and plates will be provided to the Contractor at the time of Contract/Option Award, or following receipt and inspection of materials by the Government. It is anticipated that material will be available no earlier than October

2021.

8.0 Return of GFI/GFP

The Contractor and sub-Contractors, if applicable, shall be responsible for shipping excess material and all tested specimens back to the Government at the Contractor’s expense within fourteen (14) calendar days of completion of testing, or in a timeframe as otherwise agreed to by the Government.

9.0 Security

All work under this contract is Unclassified. US citizenship is required for all individuals performing testing work. All GFI/GFP, drawings and test data are to be designated as “For

Official Use Only – Distribution Statement D”.

9.1 Any Contractor reports involving work under this contract produced for independent publication must be submitted to NSWCCD and approved by the Government for public release.

10.0 Enterprise-Wide Contractor Manpower Reporting Application (ECMRA)

N/A

11.0 Place of Performance

The place of performance for all tasking will be principally ON-SITE (at the Contractor’s or sub-Contractor’s facility). Travel by the Contractor or sub-Contractor, if applicable, is not anticipated for the performance of this tasking. The Government reserves the right to witness testing as determined necessary and/or in the best interest of the Government.

12.0 Period of Performance

The Period of Performance is from October 2021 through October 2023.

Points of Contact

The Primary Technical Advisor (TA) and Contracting Officer’s Representative (COR) is

TO BE DETERMINED.

All shipments of materials per Section 9.0 shall be addressed as follows:

NAVAL SURFACE WARFARE CENTER, Carderock Division

9500 MacArthur Boulevard

West Bethesda, MD 20817-5700

Attn: COR TO BE DETERMINED, Code XXX