Bending Stress Lab Report

I. Introduction

The purpose of this lab was to observe and record the bending stress and elastic properties multiple materials. A three-point bend is when a force is applied to the center of an object while it is supported on each side. This experiment was performed to record each material's flexural behavior so applications can be made with appropriate materials. The objective was to calculate the elastic modulus for each material tested.

II. Methodology

To start the lab, one measures and records the height and width of the Rectangular Bar specimens (steel, aluminum, sawbones) and the diameter of the Cylindrical specimens (Birch, oak dowel, acrylic, glass) in mm using a digital caliper. To be precise, measurements are made three times,

material load vs deflection graph

The failure of the materials, acrylic (GPa), glass (GPa), and sawbones (GPa) occurred in a brittle manner snapping completely in half; whereas, the birch dowel (GPa), oak dowel (GPa), steel (GPa), and aluminum (GPa) failed in a ductile manner resulting in a bent shape.

IV. Discussion

The limitations of this experiment were how precise the computer program was for measuring the breaking loads for each trial, the computer's precision for measuring the length change (y-max) of the material's deformation, and how consistent the MTS machine was at applying the same load for each trial. A confounding factor in this experiment was applying a load to a metal until it has started to yield instead of breaking like the other materials. Stress at failure for each specimen:

The elastic moduli for birch (), oak (), and glass

() varied from what is commonly deemed as their elastic moduli which is () for birch, () for oak (), and () for glass. The calculated values could for the birch and oak could be off due to water absorption and knots or other varied growth patterns. The glass's elastic moduli may be off due to the varied composition of the glass which comes from different companies using slightly different types of