Name: testing steel for strength and toughness
Uploaded: 2024-09-12T16:16:25.000Z
Duration: 1 min 18 s
Channel: JoVE

מאפיינים מכניים של פלדה כגון חוזק מתיחה נקבעים על ידי מבחן מתח שבו דגימה נמשכת במכשיר אחיזה.
קריאות מבחן המתח משמשות לשרטוט עקומת מתח-מאמץ המייצגת את התכונות הבולטות של הדגימה כמו הגבול הפרופורציונלי, נקודת התשואה, החוזק הסופי והקרע.
מבחן הפיתול מפעיל מומנט חיצוני על דגימה גלילית כדי לסובב אותה באופן אחיד ולמדוד את מודולוס הגזירה.
מבחן ההשפעה Charpy V-notch נערך בדרך כלל כדי למדוד קשיחות פלדה באמצעות דגימה מחורצת שנפגעה על ידי זרוע מתנדנדת. האנרגיה הנספגת בשבר מחושבת מהפרש הגובה לפני ואחרי הפגיעה.
בדיקת כיפוף מבוצעת כדי למצוא את היכולת של פלדה להתנגד לכיפוף. זה כרוך בכיפוף דגימת פלדה לזווית מסוימת סביב רדיוס קבוע מראש.
נוכחות ומידת הסדקים בצד המתוח של העיקול קובעים את כישלונו עקב כיפוף.
קשיות הפלדה נקבעת בדרך כלל על ידי מבחן קשיות רוקוול, המודד עד כמה חרוט יהלום או כדור פלדה חודר לדגימה בתנאים מסוימים.

מאפיינים מכניים של פלדה

Mechanical Characteristics of Steel

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המאפיינים המכניים של פלדה נבדקים באמצעות מגוון מבחנים שמעריכים את החוזק, הקשיחות והגמישות שלה. בדיקות אלו כוללות הערכות מתיחה, פיתול, פגיעה, כיפוף וקשיות, וכל אחד מהם מספק מידע חיוני על התאמת הפלדה ליישומים מסוימים.

מבחן המתיחה הוא הבסיס לקביעת חוזק מתיחה. בבדיקה זו דגימת פלדה נמתחת באמצעות מכשיר אחיזה עד שהיא נשברת. הנתונים שנאספים במהלך המבחן משמשים ליצירת עקומת מתח-עיוות, המדגישה תכונות מפתח כמו הגבול היחסי, נקודת הכניעה, החוזק האולטימטיב ונקודת השבירה.

בדיקת הפיתול כולל הפעלת מומנט על דוגמת פלדה גלילית למדידת הפיתול וחישוב מודול הגזירה. מבחן זה עוזר להבין את התנהגות הפלדה תחת כוחות פיתול.

הקשיחות של הפלדה נמדדת על ידי מבחן V-notch של צ'ארפי, שבו פוגעים בדוגמה מחורצת בעזרת זרוע מתנדנדת. האנרגיה שנספגת על ידי הדוגמה במהלך השבירה מחושבת מהפרש הגובה של הזרוע לפני ואחרי הפגיעה.

מבחן כיפוף מעריך את יכולת הפלדה לעמוד בכוחות כיפוף. הוא כולל כיפוף של דוגמת פלדה בזווית מסוימת וסביבה רדיוס קבוע, תוך התבוננות בסדקים בצד המתוח כדי לקבוע כשל.

לבסוף, קשיות הפלדה נמדדת באמצעות מבחן הקשיות של רוקוול, שבו נמדדת חדירת קונוס יהלום או כדור פלדה תחת עומס קבוע.

ביחד, מבחנים אלו מספקים פרופיל מקיף של התכונות המכאניות של פלדה, ומנחים את השימוש בה בפרויקטים הנדסיים ובבנייה.

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מאפיינים מכניים של פלדה כגון חוזק מתיחה נקבעים על ידי מבחן מתח שבו דגימה נמשכת במכשיר אחיזה.
המתח ...

Education

JoVE Core

Civil Engineering

הנדסה אזרחית

Unit 1

יחידה 1

Masonry Materials

KEY TERMS AND CONCEPTS

מונחי מפתח ומושגים

testing steel for strength and toughness

Steel is tested for strength, toughness, and flexibility using several standard mechanical tests. These tests help show how steel will behave in real use. They also help engineers choose steel for the right job.

A tension test measures tensile strength. In this test, a steel specimen is pulled in a gripping device until it breaks. The results are used to draw a stress-strain curve. That curve shows the proportional limit, yield point, ultimate strength, and the point of rupture.

A torsion test measures how steel responds to twisting force. A cylindrical specimen is given torque, which is a turning force. The test shows how much the steel twists and helps calculate the shear modulus. This information explains steel behavior under twisting loads.

Steel toughness is checked with the Charpy V-notch test. In this impact test, a notched specimen is struck by a swinging arm. The energy absorbed during fracture is found from the difference in the arm height before and after impact. A bending test is also used to see how well steel resists bending. The sample is bent to a set angle and around a fixed radius, and cracking on the tension side shows whether it fails.

Hardness is measured with the Rockwell hardness test. This test uses a diamond cone or steel ball pressed into the steel under a fixed load. The depth of penetration shows how hard the steel is. Together, these tests give a full picture of steel’s mechanical properties for engineering and construction work.

Testing Steel for Strength and Toughness

masonry

Masonry Materials and Structural Uses

Masonry uses stone and man-made units such as bricks, clay tiles, terra cotta, and concrete blocks to build structures. These units can form walls, floors, and arches. Masonry is valued for strength, durability, and a wide range of visual finishes. The units are laid in rows called coursing. Mortar, a mix of water, cement, and sand, binds the units together. Building with masonry is hands-on and can be done with basic tools. A trowel applies mortar, a hammer helps adjust placement, and levels...

mortar

Mortar in Masonry: Strength and Finish

Mortar is a key construction material used to bind masonry units together. It is made from Portland cement, hydrated lime, sand, and water. In walls, it fills gaps between units and helps spread weight more evenly across the structure. That reduces weak spots and supports a stronger build. Mortar also protects masonry from outside conditions. It acts as a barrier against water and wind, which helps safeguard the inside of the structure. It can also help correct surface irregularities in...

mortar properties

How Mortar Performance Is Measured

Mortar performance is measured by several key properties that matter in masonry work. These include workability, water retention, bond strength, durability, compressive strength, volume change, and appearance. Together, these properties help determine how well mortar can be placed, bonded, and finished. Workability is the ability of mortar to be applied and moved easily. Good workability means the mortar spreads smoothly and does not sag or fall off the surface. This helps masonry units stay...

bricks

How Bricks Are Made and Fired

Bricks are made from fired clay and come in many shapes, sizes, and colors. They are a basic building material used in construction. The brickmaking process begins with local clay or shale, which is crushed, ground, and screened to make a fine material. Next, the refined clay is mixed with water to form a workable mass. That mixture can be shaped in three main ways: soft mud, dry press, or stiff mud. Soft mud bricks are made in molds with high moisture content. They may be water-struck or...

brick sizes

Brick Sizes and Modular Masonry

Brick sizes are important in construction because they affect both the look of a building and its structural strength. Bricks are measured by three dimensions: width, thickness, and length. Builders often design them to fit modular measurements, usually in multiples of 4 inches or 8 inches in width, so they work well with other building materials. Most bricks are modular bricks. These bricks are sized to include the mortar joint, which is the layer of mortar that bonds masonry units together.

brick classifications

Types of Bricks in Construction

Bricks used in construction are grouped by where they are used and by their structure. The main types include facing bricks, building bricks, hollow bricks, paving bricks, and firebricks. These categories show how one material can serve different jobs in a structure. Facing bricks, also called face bricks, are used where both strength and appearance matter. They form the visible surface of a wall, so their look is important. Building bricks are usually placed in hidden parts of a structure,...

brick durability, strength, and appearance

How Brick Quality Affects Masonry Performance

Brick quality affects how masonry holds up, looks, and performs over time. Durability, strength, and appearance are all used to judge which bricks fit a specific job. These features help builders choose bricks for walls, facades, and other construction uses. Durability is closely tied to freeze-thaw action. In freeze-thaw, water absorbed by a brick expands when it freezes. That expansion can damage the brick, especially if the water melts and refreezes. Bricks are graded for durability as SW,...

brick masonry

Brick Wall Bonds and Wythes

Brick masonry is built from individual bricks set in mortar to form walls. A key unit in this system is the wythe, which is a vertical layer of bricks one brick thick. Inside a wythe, bricks can be arranged in different courses, or rows, to build the wall. The most common course is the stretcher course. In this pattern, each brick lies with its long edge horizontal and its face parallel to the wall. Thicker walls are made by joining multiple wythes together. Builders use headers, which are...

brick cutting techniques

Brick Cuts for Fitting Wall Spaces

Brick cuts help fit bricks into small spaces in a wall. A mason uses a hammer with a chisel-pointed end for basic shaping. The mason strikes the brick with sharp, precise blows. For more exact cuts, a power saw with a water-cooled diamond blade is used. Cut bricks are also named by size. A half-bat is a brick cut to half its original length. A three-fourth bat is cut to three-fourths of its length. These cut pieces help fill gaps and keep the wall pattern aligned. Some cuts are made for...

mortar joints in brick masonry

Mortar Joint Profiles and Brick Finishing

Mortar joints hold brick masonry together and help give the wall strength. They fill the spaces between bricks and support the finished structure. Joint thickness can vary from less than one-fourth inch to more than half an inch, depending on the need and the application. As the mortar starts to harden, workers tool the joints. Tooling means compacting and shaping the mortar. This step improves the look of the brickwork and helps it stand up better to bad weather. Brick masonry can be...

spanning openings in brick walls

Brick Wall Supports for Doors and Windows

Brick wall supports help keep openings for doors and windows stable. These supports hold up the weight of the wall above the opening. The main options are lintels, corbels, and arches. Lintels are the main support used to span an opening. They can be made from reinforced concrete, steel-reinforced brick masonry, or simple steel angles. Lintels are usually easy to install and are often hidden inside the brickwork, so they are not visible in the finished wall. Corbels provide only limited...

reinforced brick masonry

Steel-Reinforced Brick Wall Construction

Steel-reinforced brick wall construction uses steel bars and grout to make masonry walls stronger. The steel can be placed inside the hollow cores of bricks or between two layers of masonry called wythes. Grout, a fluid mix of Portland cement, aggregate, and water, holds the steel and brick together. Deformed steel reinforcement bars are set in the collar joints or in the hollow cores of the bricks. The system includes both vertical and horizontal steel bars. Vertical bars must be at least...

types of building stone

Building Stone Uses and Rock Types

Building stone is a natural construction material cut from rock deposits and shaped into the sizes needed for building work. It is grouped into three main rock types: igneous, sedimentary, and metamorphic. Each group has different properties that make it useful for specific parts of a structure. Igneous rocks form when magma or lava cools and solidifies. Granite is a common example. It is durable and resists weathering, so it works well in parts of buildings that face severe weather. <br...

quarrying of stone

Stone Extraction and Block Shaping

Stone extraction and block shaping begin in a quarry, where large blocks are removed safely and efficiently. Quarry workers may use controlled explosions, but they also use precise cutting and drilling methods. The goal is to separate stone from the rock face without damaging the material. One common method uses a diamond belt saw to make a vertical cut in the quarry face. The blocks can be very large, sometimes about 50 feet long and 12 feet high. After the cut, workers drill at the base of...

stone masonry

Stone Masonry Types and Jointing

Stone masonry is a building method that uses individual stones to form structures. It is usually divided into two main categories: rubble masonry and ashlar masonry. Rubble masonry uses uneven, naturally shaped stones. These may be river rocks or fragments from quarries. A mason often has to choose each stone carefully and may shape it to fit the space, even when the stones differ in size and form. Ashlar masonry uses stones that are cut into square or rectangular shapes. This type creates...

manufacture of concrete masonry units

Concrete Block Curing and Block Types

Concrete masonry units are made by mixing stiff concrete from Portland cement, aggregates, and water. The mix is placed into metal molds and vibrated so it settles evenly and does not separate. The wet blocks are then removed from the molds and set on racks. After molding, the blocks are moved to curing. Curing can happen in a steam kiln, where the blocks are steam cured, or in an autoclave, where high-pressure steam curing is used. This step helps the blocks gain the hardness and durability...

laying concrete masonry

Building a Concrete Block Wall

Building a concrete block wall starts with careful base preparation, mortar placement, and block alignment. The area where the wall will be built is cleaned first. Then mortar is spread where the first row of concrete blocks will sit. The first blocks are often set at a corner to mark the wall boundaries. Mortar is placed on the face shells of the blocks, which are the outward-facing surfaces. It is also applied at the ends of each block. This helps form the vertical joints between blocks and...

steel manufacturing

From Iron Ore to Shaped Steel

Steel manufacturing turns iron ore into steel through several controlled stages. It starts in a blast furnace, where iron ore is layered with coke and crushed limestone. The coke is a fuel, and the limestone helps remove unwanted material from the molten metal. Air is blasted into the furnace, and the coke ignites. This produces carbon monoxide, which reduces the iron ore to pure iron. As the iron melts, limestone forms slag. Slag traps impurities such as silica, phosphorus, and alumina. The...

structural steel products

How Structural Steel Shapes Are Made

Structural steel shapes are made in a structural mill. The process starts with a beam blank. The steel is reheated and then sent through a series of rollers that gradually form it into its final shape. The spacing between the rollers can be changed to make different sections with the same nominal dimensions. After shaping, the steel leaves the mill as a continuous length. A hot saw then cuts it into manageable pieces. The cut pieces are cooled and passed through another set of rollers. These...

steel fastening techniques

How Steel Sections Are Joined

Steel sections are joined with rivets, bolts, or welding. Each method fits different structural needs and working conditions. These fastening techniques help assemble strong steel structures in practical ways. Riveting uses cylindrical steel fasteners with a specially designed head. The rivets are heated until white-hot and then placed through pre-drilled holes in the steel sections. A pneumatic hammer shapes the exposed end into a second head, which locks the pieces together. Bolting is...

mechanical characteristics of steel

Steel is tested for strength, toughness, and flexibility using several standard mechanical tests. These tests help show how steel will behave in real use. They also help engineers choose steel for the right job. A tension test measures tensile strength. In this test, a steel specimen is pulled in a gripping device until it breaks. The results are used to draw a stress-strain curve. That curve shows the proportional limit, yield point, ultimate strength, and the point of rupture. A torsion...

key terms and concepts

Explore how steel is evaluated with tension, torsion, impact, bending, and Rockwell hardness tests to measure strength, toughness, and flexibility.

Testing Steel for Strength and Toughness | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Testing Steel for Strength and Toughness

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