Exhibit 3 Test Method for Tungsten Carbide Inserts in Underbody Blades.docx

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Attached to
Replaceable Cutting Edges for Snowplow Underbody and Wing Bl
Solicitation number
RFP 591 260000002244 1
Issued by
Michigan

About this file

This is a test method specification document for the Michigan Department of Transportation (MDOT) establishing quality assurance procedures for replaceable cutting edges with tungsten carbide inserts used on snowplow underbody and wing blades. The document outlines the testing protocol that contractors must follow to demonstrate compliance with current MDOT specifications for the brazed connection between tungsten carbide inserts and underbody blades. Sampling requirements specify that two blades per shipment (defined as any delivery within a three-week period) or four blades per yearly order, whichever is greater, shall be tested before final acceptance and payment. From each blade, four sample specimens are extracted, with two samples taken from each third point of the blade for testing purposes.

The testing procedure requires contractors to submit manufacturer certification that brazing material meets a minimum rated shear strength of 207,000 kPa (30,000 psi), with certifications forwarded to MDOT laboratory groups. Acceptance criteria mandate that averaged shear strength values for tested blades meet or exceed 138,000 kPa (20,000 psi), with no voids or brazing gaps permitted. If one originally sampled blade fails to meet the minimum requirement, a second blade from the same shipment must be tested; failure of this second blade results in rejection of the entire shipment. If two or more originally sampled blades fail the shear strength requirement, the entire shipment is rejected. Visual inspection for brazing workmanship consistency, voids, and oxidation is also required as part of the acceptance determination process.

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Exhibit 3 Test Method for Tungsten Carbide Inserts in Underbody Blades Michigan Test Method 719-01

1. SCOPE

1.1Testing of the brazed connection between the tungsten carbide inserts and the underbody blades will determine if the underbody blades meet the current MDOT specifications. Contractors will provide documentation that their blades meet the below specifications. If documentation is not provided or if MDOT requests to verify that the blades meet the current specifications, the following steps in section 3.1 will be taken.
2.TESTING EQUIPMENT
2.1Electro-hydraulic test machine.
2.1.1Fixture for shear testing of the brazed connection.
2.1.2Microscope (20X minimum).
3.SELECTION AND QUANTITY OF SAMPLES TO BE TESTED
3.1Two blades per shipment (a shipment shall be considered any delivery that takes place within a three [3] week period) or four (4) blades per yearly order, whichever is greater; shall be sampled and tested by the MDOT before final acceptance and payment is made.
3.2From each blade four sample specimens shall be taken. Two samples shall be taken from each third point of the blade for four specimens.
4.BRAZING REQUIREMENTS
4.1The MDOT specification for cutting edges with tungsten carbide inserts for moldboard assemblies requires that the inserts be securely brazed over the entire length and surface of the blade groove. Workmanship shall be consistent with sound brazing practice with no evidence of voids or use of shims. A visual inspection will be performed to determine if there are any voids present. Any observed voids in the brazing shall be noted on the test report. Brazing gaps, excessive voids, or oxidated surface not holding brazing material shall be cause for rejection of the shipment.
4.2The brazing material shall be a high strength alloy type with a minimum rated shear strength of 207,000 kPa (30,000 psi). Certification, that meets the required specifications, from the manufacturer of the brazing material is required to be submitted with the invoices to the Central Office. This certification will be forwarded to the appropriate MDOT laboratory groups.
5.PREPARATION OF THE TEST SPECIMEN
5.1Each underbody blade to be tested shall be sawed so that an individual insert and the blade base materials surrounding that insert are removed from the overall blade. The test specimen shall be machined to 19 mm to 22 mm (3/4 inch to 7/8 inch) thickness x 19 mm (3/4 inch) and 25 mm (1 inch) long.
6.PROCEDURE
6.1The test load shall be applied to the insert along the longitudinal axis at a rate not to exceed 350 1bft/sec (1560 N●m/sec). The peak load value is observed and recorded (failure of the insert does not change the peak loading value observed).
6.2The peak load is divided by the actual surface area of the insert to blade interface (approximately 0.000968 square meters [0.000968 square feet]) to obtain the shear loading value in Newtons per square meter (pounds per square inch).
6.3The inserts may shatter during shear testing, causing a lower kPa (psi) value. If the primary mode of specimen failure is shattering of the insert and the shear strength value is less than 138,000 kPa (20,000 psi) the tester may elect to either test additional samples or exclude the specimen from the average test value for that blade. A minimum of three (3) shear test values per blade must be used to calculate a valid average.
6.4The shear loadings values from the test specimens from each blade shall be averaged to obtain a final test value for each blade.
7.ACCEPTANCE OR REJECTION OF THE SHIPMENT
7.1In addition to the brazing workmanship specified in Section 4.1 the shear strength of the brazed connection is evaluated to determine if the shipment is to be accepted or rejected. If the averaged shear strength of each blade tested meets or exceeds the 138,000 kPa (20,000 psi) minimum requirement the entire shipment shall be considered accepted and payment made.
7.2If for any reason the averaged shear strength of any originally sampled blade falls below a minimum of 138,000 kPa (20,000 psi) one of two things shall occur:
7.2.1If one originally sampled blade fails to meet the 138,000 kPa (20,000 psi) requirement, a second blade from the same shipment delivery point shall be tested. Failure of this second test blade constitutes a cause for rejection of the entire shipment
7.2.2If two or more originally sampled blades fail to meet the 138,000 kPa (20,000 psi) minimum shear strength requirement this shall constitute a cause for rejection of the entire shipment being tested.

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