Pengujian Keteguhan Lengkung Statis (Static Bending Strength Test)

Summary

This practical session focuses on testing the mechanical properties of wood, specifically static bending strength. The experiment involves measuring the modulus of elasticity (MoE) and modulus of rupture (MoR), which reflect the wood’s stiffness and maximum strength, respectively. The test uses a universal testing machine to apply force on a wood sample, and the results are recorded to determine these properties. The process includes sample preparation, setup, and step-by-step measurements, with a graphical representation of the force versus deflection curve to analyze the behavior of the material under stress. The session also explains the conventional and digital methods for interpreting results.

Takeaways

• 😀 The test conducted is a static bending strength test on wood, which determines the modulus of elasticity (MOE) and modulus of rupture (MOR).
• 😀 The MOE measures the wood's ability to resist deformation under stress, while the MOR measures the maximum stress it can withstand before failure.
• 😀 The test uses a universal testing machine (UTM) to apply load and measure the deflection of a wood sample placed on two supports.
• 😀 The sample's dimensions (length, thickness, and width) must be measured accurately before the test to calculate the necessary values.
• 😀 The standard length between the supports is determined by the sample's thickness, ensuring a consistent testing setup.
• 😀 During testing, load is applied to the wood sample until it reaches a point where the wood bends significantly, followed by eventual fracture.
• 😀 Two primary calculation formulas are used: one for the modulus of elasticity (MOE) and another for the modulus of rupture (MOR).
• 😀 The test measures how much the wood deforms (deflection) under a specific load, with the data used to generate a stress-strain curve.
• 😀 The curve shows the wood’s behavior, including the elastic region (where deformation is recoverable) and the plastic region (where permanent deformation occurs).
• 😀 After the wood sample fractures, the maximum load it withstood is recorded, which is used to calculate its MOR value.
• 😀 The testing process helps determine the strength and stiffness of the wood, which is essential for applications like beams and roof supports.

Q & A

What is the focus of the experiment discussed in the video?

The experiment focuses on testing the mechanical properties of wood, specifically static bending strength, which involves determining the modulus of elasticity (MOE) and the modulus of rupture (MOR).

What does the modulus of elasticity (MOE) represent in the context of this test?

The modulus of elasticity (MOE) measures the wood's ability to resist deformation under stress in the elastic range, essentially indicating the stiffness or rigidity of the material.

How is the modulus of rupture (MOR) different from MOE?

The modulus of rupture (MOR) measures the maximum bending strength of the wood until it breaks or fails, whereas MOE is concerned with the material's behavior within its elastic limit, before permanent deformation occurs.

What is the purpose of the setup where the wood is placed on supports and a load is applied?

The setup is designed to simulate the real-world conditions where the wood is used, such as in beams or roof supports, by applying a load to measure how the wood bends and eventually breaks under stress.

What are the key dimensions of the wood sample used in this test?

The key dimensions of the wood sample include its thickness, width, and length. Specifically, the length of the sample should be 360 mm, the width 20 mm, and the thickness 20 mm.

Why is the sample's thickness and width measured precisely before testing?

Precise measurement of the sample's dimensions is crucial to ensure the correct application of the formula for calculating MOE and MOR, as these values depend on accurate physical properties of the wood.

What kind of testing machine is used for this experiment?

The Universal Testing Machine (UTM) is used to apply a controlled load to the wood sample and measure the resulting deflections and forces to determine the mechanical properties.

What is the significance of the graph produced during the test?

The graph represents the relationship between the applied load and the resulting deflection. It shows both the elastic and plastic regions of the material's behavior, ultimately helping to calculate MOE and MOR.

How do the different stages of the load-deflection graph help in determining the wood's properties?

In the initial stage, the graph is linear, representing elastic deformation, where the material returns to its original shape. As the load increases and enters the plastic region, the curve bends, indicating irreversible deformation. The maximum point on the graph indicates the material's breaking point, representing the MOR.

What is the role of the deflectometer in the testing process?

The deflectometer measures the deflection of the wood sample as it is loaded. It helps in determining how much the material bends under a given load, providing data for calculating MOE and MOR.