lab4 - Introduction Four-point bending tests will be...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Introduction Four-point bending tests will be performed on steel 1045 hot-rolled, aluminum 6061, and PMMA. Each bending specimen will be rectangular in cross-section and come machined with a notch in the center in order to determine the effects the notch has on the specimen’s load-carrying ability. There will be two different specimens for both steel 1045 and aluminum 6061; one will have a sharp notch and the other will have a round notch. PMMA will be tested with a sharp notch only, however two specimens will be tested; one with the notch in compression, the other with it in tension. The differences between the sharp and round notches will be examined for the different materials and the data from the notch bending tests will be compared to data obtained in un- notched bending tests. The two properties that will be compared in the notch test to the un-notched bending test are apparent yield strength ( σ . y ) and the modulus of rupture in bending ( R B ). The apparent yield strength is where the notched specimen leaves the linear- elastic region, however this value may be higher or lower than the actual yield strength ( σ y ) due to the phenomena of notch strengthening and notch weakening. The modulus of rupture in bending is the maximum fiber stress at failure. Also, photoelasticity will be examined as a way to look at principal stains by passing circularly polarized light through a material. Procedure The sharp notch radius was measured using a microscope. This value was only measured for one specimen and was assumed to be the same for all other machined sharp notches. However, the diameters of the round notches were measured once for every specimen using digital calipers. The overall beam height, and beam thickness were each measured three times and averaged, while the notch depth was only measured once per sample. Next, a specimen was centered in the Instron Model 4400. The aluminum 6061 and steel 1045 samples were all loaded with the notch at the bottom, while the PMMA specimens were loaded one with the notch at the top and one with the notch at the bottom. After the initial measurements were entered into the computer and the program was set up to record position and load in even increments in time, a steadily increasing four-point bending load was applied to the sample. The test was stopped at negative 0.3kN for aluminum 6061 and steel 1045. The specimens were then fractured by hand and the fracture surfaces were observed and recorded. Final measurements of the width at the top and bottom of each sample were recorded as well. Next, a photoelasticity demonstration was done in order to visualize the stress in a beam with and without a notch. The specimen tested was PSM-1, a transparent, birefringent polycarbonate that is
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This lab report was uploaded on 04/20/2008 for the course GE 312 taught by Professor Reis during the Spring '06 term at University of Illinois at Urbana–Champaign.

Page1 / 4

lab4 - Introduction Four-point bending tests will be...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online