A wooden beam undergoes a bending test to examine its flexural behavior and to calculate the Modulus of Elasticity and Modulus of Rupture of the wood. This test helps in understanding how the beam behaves when subjected to a load, and how much stress it can withstand before it breaks. By studying the bending of the wooden beam, engineers and researchers can analyze the strength and stiffness of the wood and determine its suitability for various applications. The Modulus of Elasticity is a measure of the wood’s ability to bend without permanently deforming, while the Modulus of Rupture indicates the maximum amount of stress the wood can withstand before breaking. Overall, the bending test on a wooden beam provides valuable insights into the physical properties and performance of the wood, which can help inform decisions about its use in construction, manufacturing, and other industries.
Equipment Required
The equipment being referred to is a 10 ton Buckton Universal Testing Machine (UTM) along with deflection gauges, a wooden beam, and a measuring tape. The UTM is a device used to test the strength and durability of materials by subjecting them to controlled amounts of force. The deflection gauges are used to measure the amount of deformation or bending that occurs in the material being tested. The wooden beam is likely a specimen that is being tested, and the measuring tape is used to record the dimensions and other measurements of the specimen. Together, these tools and equipment can provide valuable data on the properties of materials and help engineers and scientists make informed decisions about their use in various applications.
Theory and Principle
To determine the modulus of elasticity in bending and bending strength, a load is applied to the center of a test piece that is supported at two points. The test piece is typically a beam or a similar structural element. The load is applied in a way that creates a bending moment in the test piece, which causes it to deflect.
The modulus of elasticity is calculated by using the slope of the linear region of the load-deflection curve. This means that the deflection of the test piece is measured at different loads, and the slope of the curve that connects these points is used to determine the modulus of elasticity.
The bending strength of each test piece is calculated by determining the ratio of the bending moment M, at the maximum load Fmax, to the moment of its full cross-section. This means that the maximum load that the test piece can withstand without breaking is determined, and the bending moment at that load is divided by the moment of the cross-section of the test piece.
For a simply supported beam with central loading, the deflection under the load can be calculated using known equations and formulas. This is important because the amount of deflection is a key factor in determining the modulus of elasticity and bending strength of the test piece.
Where,
W =Applied load
L = Effective span of the beam
E = Young’s Modulus of wood
I = Moment of inertia
Test Procedure
To conduct a bending test on a wooden beam using a Universal Testing Machine (UTM), certain steps need to be followed. Firstly, the bending device must be inserted into the UTM. Subsequently, the width and depth of the wooden beam are measured and noted down. The support is then adjusted to the required distance and clamped to the lower table of the UTM.
To ensure proper testing, the transverse test pan is fixed to the lower side of the lower cross head of the UTM. It is then fixed onto the rollers of the transverse test brackets, in a manner that the load is centered. The length of the span of the beam between the supports for central loading is then measured.
In order to begin the testing process, the load pointer is adjusted to zero by lifting the lower table. The load is then applied while noting down the deflection corresponding to each load from the vernier scale on the UTM. Finally, the maximum deflection and the maximum load are recorded for analysis and interpretation of the results obtained from the bending test.
Observation and Calculation
b=____ mm, h= ____mm, l=____mm
Breaking Load (Pmax): _____ tons
Modulus of Rupture =
The modulus of rupture is a material property that indicates the maximum amount of stress that a material can withstand before breaking or fracturing. It is often denoted in megapascals (MPa) and is used as a measure of a material’s strength and resistance to fracture.
On the other hand, the modulus of elasticity is a material property that represents the material’s ability to deform elastically under stress. It is also known as Young’s modulus and is often denoted in pascals (Pa) or gigapascals (GPa). The modulus of elasticity can be used to calculate the amount of stress a material can withstand before it undergoes permanent deformation or plasticity.
Both the modulus of rupture and modulus of elasticity are important material properties that are used in engineering and materials science to understand how materials behave under different types of stress and loading conditions. These properties can help engineers and designers select the appropriate materials for specific applications and ensure that structures and components are able to withstand the loads and stresses they will encounter in use.
The modulus of elasticity, a fundamental mechanical property, is typically denoted in units of gigapascals (GPa). It describes the ability of a material to deform elastically in response to an applied load, and is a key parameter in the design and analysis of structures and materials. GPa is an abbreviation for gigapascals, which is a unit of pressure or stress equal to one billion pascals. The modulus of elasticity is also sometimes referred to as Young’s modulus, after the scientist who first proposed the concept in the early 19th century. By measuring the deformation of a material under a controlled load, it is possible to determine its modulus of elasticity and use this information to predict its behavior in real-world applications.
Test Precautions
To ensure ease of reading the deflection against each reading, it is recommended to apply loads gradually. This gradual application of loads can also prevent any potential damage to the gauges that are being used to measure deflection. However, it is important to remove these gauges before the failure load is reached as they may get damaged otherwise.
Additionally, it is crucial to prioritize safety when using a machine to apply loads. During the application of loads, particles may be generated which can cause injury if they come into contact with someone. Therefore, it is advised to stay away from the machine while the load is being applied to ensure the safety of everyone involved in the process.