Bend Testing

What is it? Long beam has an applied load perpendicular to its main (longitudinal) axis.

What is it? Often accompanied with two or more point supports.

What is it? Measures flexural strength, σ Also used for testing welds Remember that strength and “stress” here are used interchangeably Also used for testing welds

Bend Test Bend tests, not to be confused with drop tests. Gradual application of load instead of instant shock.

Bend! Three kinds of bend tests discussed today Wrap-Around Bend Test (Simple) 3 – Point Bend Test 4 – Point Bend Test

Wrap-Around Guided Bend Test A specimen of thickness, T, is bent using a hand tool similar to a plumber’s pipe bender.

Wrap-Around Guided Bend Test A specimen of thickness, T, is bent using a hand tool similar to a plumber’s pipe bender.

Wrap-Around Guided Bend Test Welds are often tested using this method.

3 – Point Bend Test Like a compression test, but with three points

3 – Point Bend Test

3 – Point Bend Test Insert Video

3 – Point Bend Test Measuring Stress F b d L

3 – Point Bend Test Measuring Stress F = Load (N) L = Length between supports (mm) b = width (mm) d = thickness (mm)

Application Testing structural components like Glulams Layers of timber glued together, often used in structures

Application Glulam

Application Glulam

Application Glulam

Application Glulam Testing

Application Why? What was different about the test in the video? Characterize limits What was different about the test in the video?

4 – Point Bend Test

4 – Point Bend Test Measuring Stress F/2 F/2 b d L

4 – Point Bend Test Measuring Stress F/2 F/2 b d L Loading Span

4 – Point Bend Test Measuring Stress IF Loading Span is 1/3 of support span: IF Loading Span is 1/2 of support span:

Bend Tests What’s the difference? Type of Bend Test 3-Point 4-Point Type of Material Homogeneous (plastics) Non-Homogeneous (composites & wood) Stress Concentration Small and concentrated under the center loading point Larger region to avoid premature failure Specimen Deflection Typically measured with the crosshead position Typically measured with a deflectometer

Bend Tests Deflectometer is to transverse loading (bend testing) Extensometer is to longitudinal loading (tensile testing)

Internal Behavior Beam experiences both compression AND tension during bend testing

Sources: Title slide image: http://www. mpa. uni-stuttgart Sources: Title slide image: http://www.mpa.uni-stuttgart.de/organisation/fb_1/abt_12/index.en.html Wrap-Around guided bend test: http://www.twi-global.com/technical-knowledge/job-knowledge/bend-testing-073/ http://www.twi-global.com/technical-knowledge/job-knowledge/bend-testing-073/ http://www.publiclogic.com/fish/1/DSC07471.JPG http://www.esabna.com/us/en/education/knowledge/qa/problems-passing-guided-bend-tests.cfm http://www.composites.ugent.be/movies/anim_Can_with_water.gif http://www.substech.com/dokuwiki/lib/exe/fetch.php?w=&h=&cache=cache&media=3-point_flexure.png http://rocketmaterials.org/datastore/fins/Bend/3-point-bend.JPG http://img.archiexpo.com/images_ae/photo-g/glulam-timber-pedestrian-bridges-70349-4290457.jpg http://www.ecs.csun.edu/hpv/images/IMG_1395.jpg