Lesson 10 Testing EG243
March 13, 2013
Lecture 10 Testing:
-square and .505 round tensile specimens
-”The Design and Methods of Construction of Welded Steel Merchant Vessels, 15 July
1946" book
-Charpy impact specimens
-Transverse and longitudinal shear test specimens
- examples of AWS D1.1 showing coupon removal
-examples of face, root, side bends
-x-ray films and test assemblies
- standards showing acceptable levels of porosity
- film cassette with exposed film
- Dye penetrant, cleaner, developer
- PT specimen
- MT equipment
- MT crack specimens
- UT equipment
- UT test assembly
- UT procedure
Lecture:
- Two types of testing. First consider Destructive Testing (Mechanical Testing). For welding,
DT is used to qualify procedures and welders, in the laboratory. Common Destructive tests:
- Page 576 Tensile: rectangular or .Page 575 .505 round: load/cross-sectional area = psi
- Also on Page 576 ductility: elongation/gage on tensile specimen Final gauge length
minus originalgauge lentgth divided by originl gauge length = % in 2 inches.
- Page 591 hardness: resistance to penetration indicates wear-resistance and strength.
(Directly related to tensile strength: ½ Brinell Hardness x 1000 = tensile psi.)
- Page 577 Another test done on a tensile testing machine is the shear test. Two types:
- transverse: max. force / (2 x width) .
- longitudinal: max. force / length of ruptured weld
- Page 576 – 7 fatigue: amount of stress, and number of stress cycles without failure and
the stress used.
- Page 583 impact test: Charpy specimens, ft-lbs. Absorbed from pendulum indicates
toughness. Show broken Liberty Ships in book “The Design and Construction…”
- page 582 (top): fillet break test: inspect broken weld faces.
- Page 579 bends: root, face, side. Face toward gap, rRoot toward gap, side bend either
side to the gap.
- Nondestructive Testing: To examine welds in production where samples can't be removed.
- Start Dye Penetrant (surface only)
Lesson 10 Testing EG243
March 13, 2013
- precleaning and penetrant application.
- Visual Testing is most common show:
- Overlap forms stress raiser.
- Porosity is often not visible on surface.
- Undercut: show plastic weld examples
- Crater cracks, caused by shrinkage, can be avoided by filling and reducing heat slowly.
- Underfill.
- Inadequate penetration: LOF in root
- Lamination, Delamination, Lamellar Tears caused by stress across thickness of plate.
Change joint design, make smaller passes to reduce stress.
- Magnetic Particle
- magnetic field created in workpiece by electromagnet or electric current is disrupted by
discontinuities:
-in MT this is revealed by attracting iron powder.
- in Eddy Current testing, the strength of the field is measured
- inspects surface and as much as 1/8" deep, but cannot locate flaws deep beneath the
surface.
- (show cracks)
- X-Ray (Radiography,volumetric)
- x-rays are blocked by metal, discontinuities allow more rays to pass through, film
devlops black.
- show Inclusions: nonmetallic materials, slag, silicates.
- ( show Incomplete Fusion, or LOF)
- Porosity: small amounts may be acceptable discontinuities, but more than allowed are
“defects”.(MIL-STD 2035 in PT Procedure).
- Not all inspected to same standard. Class I,II,III depends on type of service.
- Ultrasonic (volumetric)
- show diagram of use of trigonometry to map length and width of flaws.
- Finish Dye Penetrant (surface only)
- precleaning and penetrant application done at beginning of lecture
- clean off penetrant.
- apply developer.
- inspect.
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Today’s lab, from the Course Schedule in the 3 ring binders.
Booths 1-7 first demonstration. Booths 8 – 14 cut plates.