8.3.2 Bend Testing Explained

Key Concepts of Bend Testing

1. Definition

Bend Testing is a destructive testing method used to evaluate the ductility and integrity of welds. It involves bending a welded specimen to a specified angle and inspecting it for any cracks or defects that may appear.

2. Types of Bend Tests

There are several types of bend tests, including:

• Face Bend Test: The specimen is bent with the weld face on the outer surface.
• Root Bend Test: The specimen is bent with the weld root on the outer surface.
• Side Bend Test: The specimen is bent with the weld running along the length of the bend.

3. Purpose of Bend Testing

Bend Testing serves several important purposes:

• Ductility Assessment: Determines the ability of the weld to deform without cracking.
• Quality Control: Ensures that the weld meets specified standards and specifications.
• Defect Detection: Identifies any internal or surface defects that may not be visible through visual inspection.

4. Procedure of Bend Testing

The procedure for conducting a bend test typically involves the following steps:

1. Specimen Preparation: Cut a sample from the welded joint and prepare it according to the test standard.
2. Marking: Mark the specimen to identify the weld location and orientation.
3. Bending: Place the specimen in a bending jig and apply force to bend it to the specified angle.
4. Inspection: Examine the bent specimen for any cracks or defects.
5. Evaluation: Compare the results against the acceptance criteria specified in the test standard.

5. Acceptance Criteria

The acceptance criteria for bend tests are typically based on the following factors:

• Crack Length: The maximum allowable length of any crack that may appear.
• Crack Depth: The maximum allowable depth of any crack.
• Surface Condition: The overall appearance of the bent specimen, including any surface defects.

Examples and Analogies

Imagine Bend Testing as bending a paperclip. Just as bending a paperclip repeatedly can cause it to break, bending a welded specimen can reveal its susceptibility to cracking.

Think of the Face Bend Test as bending a piece of paper with writing on one side. Just as the writing on the paper is visible when bent, the weld face is visible when the specimen is bent in this test.

Consider the Root Bend Test as bending a piece of paper with writing on the other side. Just as the writing on the other side becomes visible, the weld root is exposed when the specimen is bent in this test.

Visualize the Side Bend Test as bending a piece of paper along its length. Just as the paper bends along its length, the weld runs along the length of the bend in this test.