- - AGRICULTURE CORE CURRICULUM - -

(CLF2000) Advanced Core Cluster: AGRICULTURE MECHANICS

 (CLF2300)  Unit Title: ARC WELDING

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 (CLF2306)    Topic: WELD TESTING              Time              Years
                                                2 Hours     1 / 2 / 3 / 4
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          Topic Objectives: Upon completion of this lesson, the student
                            will be able to:

          Learning Outcome: #:

             (G-7) - Test welds for quality and strength.

          Special Material and Equipment: Various pieces of metal showing 
                       various welds, clamps, hammers, furnace or other 
                       device to heat metal, welding apparatus, and safety 
                       gear

          References: Burke, Stanley R., & Wakeman, T. J. (1990). MODERN
                         AGRICULTURAL MECHANICS (2nd ed.). Danville, IL:
                         Interstate Publishers.
                       Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS:
                          FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar
                          Publishers.
                       Phipps, Lloyd J., & Reynolds, Carl L. (1990).
                         MECHANICS IN AGRICULTURE (4th ed.). Danville, IL:
                         Interstate Publishers.

          Resources:  Deere & Company. (1987). WELDING (6th ed.) 
                         (Fundamentals of Service (FOS) Series). Available 
                         from: John Deere Technical Services, Dept. F, John 
                         Deere Road, Moline, IL 61265 (Available in
                         Spanish)
                       Giachino, Joseph W., & Weeks, William  (1976). 
                         WELDING SKILLS AND PRACTICES (5th ed.). Available 
                         from: American Technical Society, Chicago, IL 60637
                       Hobart Brothers Company. (1978). TECHNICAL GUIDE FOR 
                         SHIELDED METAL ARC WELDING. Available from: Hobart 
                         Brothers Company, Troy, OH 45373

          Evaluation: Quiz by the instructor and satisfactory completion of 
                       weld testing activities.

TOPIC PRESENTATION: WELD TESTING
A. Visual Examination

   1. Look at the weld through a magnifying glass for a thorough 
       examination. The surface qualities of the weld (for example, cracks, 
       undercuts, inadequate or excessive penetration, lack of fusion, bead 
       size, contour) can easily be seen. Use a weld gauge to check bead 
       size and contour.

B. Destructive Testing

   1. Destructive testing entails loading the weld to the point that the 
       sample piece fails.

   2. The main types of destructive tests are for tensile strength, shear, 
       and weld uniformity.

       a. Both a tensile strength test and a shear test require a tensile 
           strength testing machine which has the ability to pull the welded 
           piece until it breaks.

       b. Weld uniformity can be tested by two different methods, the nick-
           break test and the free-bend test.

           1) The nick-break test is done by notching the weld placement 
               1/4" to 3/8" on each side and then placing it in a press to 
               rupture the weld specimen.

           2) The purpose of the nick-break test is to check the fractured 
               weld surface for porosity, gas pockets, slag inclusions, 
               overlaps, penetration, and grain size.

           3) The free-bend test can be done by using a vise or a special 
               holding tool. The weld bead is ground until it is flush with 
               the base metal surface. The grinding should be done so the 
               grinding wheel marks run across the weld in the direction of 
               the bead in order not to weaken the weld.

           4) The purpose of the free-bend test is to bend the weld specimen 
               in order to check ductility.

C. Nondestructive Testing

   1. Nondestructive testing employs various methods that evaluates welds 
       without impairing their function and usefulness.

       a. Magna-flux is used to determine the presence of very fine cracks 
           and other flaws.

       b. Dye penetrant inspection shows surface defects.

       c. Various testing machines can be used to find flaws and check for 
           hardness.
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       ACTIVITY:

       1. Perform a nick-break test on a weld.

       2. Perform a free-bend test on a weld.

       3. Perform visual examination of a weld using professionally 
           built inspection equipment.
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7/23/91 RRE/DF/tf


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