Lab 2 Rock tensile strength: Brazilian test

Summary

This video explains the process of performing a tensile strength test using the Brazilian density strength method. The procedure involves applying force to a cylindrical rock sample, measuring its diameter and length, and observing the fracture point. Key steps include sample measurement, setup of the loading frame, alignment checks, and data analysis. The video highlights how to calculate tensile strength based on the peak load and dimensions of the sample, emphasizing the importance of precision during both the testing and analysis phases.

Takeaways

• 🧪 The focus of this lab (Laboratory 2) is on measuring tensile strength using the Brazilian tensile strength test.
• 📏 The sample used in this test is a cylindrical rock with equal length and diameter, and force is applied along the cylindrical side.
• 💥 The test generates tensile strength, causing a fracture in the rock, and the tensile strength is estimated from the peak load and sample dimensions.
• 📊 Steps in the analysis include sample measurement, loading frame setup, fracturing, and data analysis—similar to Laboratory 1.
• 📐 The diameter is measured in different directions to ensure the sample is as circular as possible, while length measurement is less critical compared to Lab 1.
• 🔄 The alignment of the top and bottom parts of the frame is checked to ensure they are parallel using a level tool.
• ⚙️ The control setup monitors two key parameters: the load and displacement, with displacement measurement being optional in this lab.
• ⏩ Two speeds are used in the setup: one for movement and one for displacement, and the lower frame is raised until it touches the upper frame.
• 🛡️ Protective plastic is placed around the sample in case the rock explodes during the test.
• 📸 After the rock fractures, a force drop is observed, and data is captured for further analysis, including calculating tensile strength based on the peak load.

Q & A

What is the main focus of the laboratory experiment discussed in the transcript?

The main focus of the laboratory experiment is to measure the tensile strength of a cylindrical rock sample using the Brazilian Tensile Strength test method.

What shape is the rock sample used in the tensile strength test?

The rock sample used in the tensile strength test is cylindrical, with the diameter and length being the same.

How is the tensile strength generated during the test?

Tensile strength is generated by applying force along the cylindrical side of the sample, which causes a fracture in the rock.

What are the key measurements needed before starting the tensile strength test?

The key measurements needed are the diameter and the length of the sample. These measurements help in estimating the tensile strength once the peak load is known.

Why is it important to check the circularity of the sample during the preparation phase?

It is important to check the circularity of the sample to ensure that the sample is as close to a perfect cylinder as possible. An irregular shape may affect the accuracy of the tensile strength measurement.

How does bedding direction influence the tensile strength test?

Bedding direction can affect the tensile strength of the sample depending on how the stress is applied during the test. It is important to check for bedding direction before proceeding.

Why is it necessary to level the top and bottom parts of the frame before testing?

It is necessary to level the top and bottom parts of the frame to ensure that the load is applied evenly across the sample. Misalignment could result in inaccurate measurements.

What are the two main parameters controlled during the tensile strength test?

The two main parameters controlled during the test are the load and the speed of displacement.

What indicates that the sample has fractured during the test?

The sample is considered to have fractured when the load applied reaches a peak and then suddenly drops.

How is the tensile strength calculated after the test is completed?

Tensile strength is calculated using the peak load applied during the test, along with the sample's length and diameter measurements.

Outlines

00:00

🧪 Introduction to Tensile Strength and Brazilian Density Test

In this section, the speaker introduces the topic of tensile strength testing for cylindrical rock samples, specifically using the Brazilian Density Strength Test. The method involves applying force along the cylindrical side of the sample to generate tensile strength and fracture the rock. The tensile strength can be calculated using the peak load and by measuring the sample's dimensions (length and diameter). The procedure is similar to what was covered in a previous lab session, and involves sample measurement, loading frame setup, fracturing, and data analysis.

05:00

🧩 Importance of Sample Measurement and Quality Control

The speaker emphasizes the need for careful sample measurement and quality control. Two key factors are highlighted: ensuring the sample is as circular as possible, and considering the impact of bedding direction on tensile strength. Multiple measurements of the diameter and length are taken to ensure accuracy, although the length is less critical compared to the first lab session. Special attention is given to whether the sample has bedding, as this could affect the results of the tensile strength test.

🔧 Setting Up the Loading Frame

This section covers the setup of the loading frame used in the tensile strength test. The speaker explains that the top and bottom parts of the frame must be parallel, which is checked using a level. Once the frame is properly aligned, the sample can be positioned for testing. The speaker explains the control system, noting that while vertical displacement is not necessary for this test, it can still be measured if additional data is needed. Various functions on the control panel are described for adjusting the speed and monitoring the test.

🚀 Preparing for the Tensile Strength Test

The speaker discusses the final preparation steps before the tensile strength test begins. Two speeds (screen speed and displacement speed) are used to carefully position the sample in the frame. As the lower frame moves up and touches the upper frame, the force increases slightly, signaling that the sample is in place. Safety precautions are also mentioned, including the use of protective plastic around the sample to prevent injury in case the rock explodes during testing.

🔨 Conducting the Fracture Test

In this section, the speaker explains the process of conducting the fracture test. The lower part of the frame is moved up to increase the load on the sample. As the load increases, it will reach a peak before dropping when the rock fractures. The test is stopped once the force drops, and a picture of the fractured sample is taken. The data collected is stored for further analysis.

📊 Data Analysis and Tensile Strength Calculation

The final section covers data analysis and the calculation of tensile strength. Using the previously measured length and diameter of the sample, along with the peak load recorded during the test, the tensile strength of the rock can be calculated. The speaker concludes by mentioning that this data will be used for reporting and further analysis.

Keywords

💡Tensile Strength

Tensile strength refers to the resistance of a material to breaking under tension. In the context of the video, it is a crucial property being tested in rocks to understand their ability to withstand forces that pull them apart. The Brazilian test method, as discussed, measures this strength by applying a load to a cylindrical sample.

💡Brazilian Test

The Brazilian test, also known as the Brazilian tensile strength test, is a method for measuring the tensile strength of materials, especially rocks. In this video, the method involves applying force to the sides of a cylindrical sample to induce a tensile fracture. The results help in determining the material's strength under tension.

💡Cylindrical Sample

A cylindrical sample refers to the rock specimen used in the tensile strength test, characterized by having equal diameter and length. In the video, this sample is the subject of various measurements (diameter and length) before the tensile test is performed. Ensuring the sample is as circular as possible is important for accurate test results.

💡Fracture

Fracture refers to the breaking or cracking of a material when subjected to stress. In the video, a fracture is induced in the rock sample during the tensile strength test when the applied load exceeds the material's limit, leading to the failure of the rock. Observing the fracture helps in understanding the material's strength properties.

💡Load Cell

A load cell is a sensor or device used to measure force or load. In this tensile strength test, the load cell measures the force applied to the cylindrical sample until it fractures. The peak load recorded by the load cell is crucial for calculating the tensile strength of the material.

💡Sample Measurement

Sample measurement involves taking precise measurements of the cylindrical sample’s diameter and length before conducting the tensile test. These dimensions are critical for calculating tensile strength. As described in the video, measurements are taken in different directions to ensure the sample is circular and to account for potential irregularities.

💡Loading Frame

The loading frame is the apparatus used to apply force to the sample in the tensile strength test. In the video, the frame is aligned carefully, and adjustments are made to ensure that the top and bottom parts are parallel, which is necessary for consistent and accurate force application during the test.

💡Bedding Direction

Bedding direction refers to the orientation of layers within the rock sample, which can affect its strength properties. In the video, it is mentioned that the bedding direction must be checked because it may influence the tensile strength depending on how the load is applied to the sample.

💡Displacement

Displacement in this context refers to the movement of the sample within the loading frame as the force is applied. While vertical displacement is mentioned as less critical in this test compared to others, it is still measured in some cases to provide additional data regarding the movement of the sample during testing.

💡Data Analysis

Data analysis involves interpreting the results from the tensile strength test. After the sample fractures, the peak load and the measurements of the sample (length and diameter) are used to calculate the tensile strength. This process, as outlined in the video, includes recording the maximum force and analyzing the resulting fracture pattern to determine the material's behavior under stress.

Highlights

Introduction to tensile strength and the Brazilian density strength test.

Description of using a frame to apply force on a cylindrical sample.

Explanation of how force is applied along the cylindrical side to generate tensile strength and fracture.

Method to estimate tensile strength based on peak load, sample length, and diameter.

Steps for analysis: sample measurement, loading frame setup, fracturing, and data analysis.

Importance of quality checking the sample to ensure it is as circular as possible.

Impact of bearing direction on tensile strength depending on stress application.

Measuring sample diameter in different directions to check circularity.

Less criticality of parallel faces for length measurement compared to laboratory 1.

Checking for bedding direction in the sample.

Ensuring the frame's top and bottom parts are parallel using a level.

Setting the sample and controlling parameters: load and displacement.

Using two speeds: screen speed and displacement speed for the frame.

Protective measures: placing protective plastic around the sample during measurement.

Observing load increase and drop during fracturing to determine fracture.

Stopping analysis, capturing fracture data, and structuring the data file for the report.

Calculating tensile strength using sample dimensions and highest applied load.

Transcripts

this talk is going to be

for the laboratory number two in our

attorney number two

we are going to talk about tensile

strength

the method that we use to measure

that inside strength is called brazilian

density

strength test in here

we use a frame to apply a force on a

cylindrical sum

in this cylindrical sample diameter and

length

have the same length

and the force that we are applying

is along the cylindrical side

of the sample in this case

when we apply the load we generate

a tensile strength generating the

fracture

in the rock we can estimate

the tensile strength based on the

peak load and by the sample and

by knowing the length and the diameter

of the

ceiling

the steps that we are going to

[Music]

use to for this analysis

are the same that we already seen in

laboratory 1

which are sample measurement loading

frame setup

fracturing and data analysis

what we observe is that again we need to

measure and quality check the sample

that we are going to use in our analysis

the main points in here are two first

samples are not going to be perfectly

selenium

this case we have to check that the

sample

or the cylinder is as circular as

possible

second that is

if we have bearing bearing

direction may affect the tensile

strength

depending on how we apply the stress on

the sample

to analyze the sample we are going to

measure

two values diameter

d and length

l in the case of the diameter

we are going to measure in different

directions

just to check that the side that the

sample is

circular and we are going to use the

address

for the length we are going to measure

at different directions

in this case compared to our retina re1

we don't need the sample to be to have

parallel

and faces so length

measuring is not as critical as we

observe

in laboratory one however we have to

check

whether we have bedding and if we have

bedding direction

so now we are going to

analyze and

to check if the frame is

a properly settled for the work

first we have to check if

the top and the bottom part of the frame

are parallel or not to check that

we use a level and what we check is

actually is that

the level at the top and the bottom are

aligned one exit with each other

then we can proceed to sit in the sample

again as in our 31 we are going to

have the the control

where we check two main parameters first

the load a second displacement

in the laboratory two this vertical

displacement

is not going to be necessary however you

can measure

it in case that you need some additional

information

to measure whether we are moving

the sample up or down we can use

develops up or down and to control the

speed

we can check speed and go to the menu

here f2 is going to you to be used

to control the digits while f3 and

f4 are going to check where to

increase or decrease the digit that we

are

stepping on once we confirm the speed

we just hit speed to go back to the menu

before

in this work again we are going to use

two speeds

screen speed and displacement speed

using certain speed then we can

sit ourselves it means that

we are going to move up

our lower frame until

it touches the upper part of the frame

when that happens we'll see that the

force

slightly increases now we are ready to

do the measurement so

we just have to place protective plastic

around

in case that the frag that the rock is

so

explodes during the measurement

so now that we have the leveling check

and that we see the sample we are going

to go

to a factory the fracturing what we are

going to do is

just we are going to keep moving up the

lower part of the frame

but we are going to observe an

increase in the load that we are

applying

this load is going to reach a minimum

and then

it's going to have a drop when the

fractal fades

when the rock phase and

by the end of the after the data

analysis

we can see a video where we are applying

and strength on the sample until it

fractures

so as i mentioned before we have to move

up

we expect to see a forced rope and then

we immediately stop the analysis

take a picture of the fracture and

struck the data file

for our report finally

we can proceed with our data analysis

to calculate the tensile strength we

already have the length

and the diameter of the sample so we

have to

[Music]

find which was the highest load

that we are applied in our load cell

and from this value we can calculate

that inside strength

you