Name: charpy v-notch testing of steel fracture
Uploaded: 2023-04-30T06:57:55.000Z
Duration: 7 min 32 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS+Phy.P3

HS+Phy.P3U2.5

charpy-impact-test-cold-formed-hot-rolled-steels-under-diverse

Charpy Impact Test of Cold Formed and Hot Rolled Steels Under Diverse Temperature Conditions

In this experiment we will test several Charpy specimens at different temperatures to illustrate the temperature effect on impact resistance of mild steel.
<ol>
	<li>To prepare the testing machine, first make sure the path of the hammer is clear of any obstructions. Once the path is clear, lift the hammer until it latches and secure the lock to prevent accidental release of the hammer.</li>
	<li>To prepare the specimens, use the cold box to cool one specimen of each metal to a temperature well below freezing.Use a hot plate to heat another specimen of each metal to a temperature above 200 &#176; F.</li>
	<li>Once the hammer is raised, insert the specimen into the machine using tongs making sure it is centered in the fixture with the notch facing away from the side to be impacted by the hammer.</li>
	<li>Once the specimen is ready, set the dial on the machine to exactly 300 ft-lbs. Important: Turn the dial using the knob. Do not push on the pointer!</li>
	<li>To begin the test, remove the lock and release the pendulum by pressing on the lever.</li>
	<li>After the specimen has been broken, the dial gage will read the energy absorbed by the specimen. Record this value.</li>
	<li>Once the absorbed energy is recorded, you may use the machine brake to stop the pendulum from swinging. Since using the brake changes the gage reading, be sure to record the data before using it.</li>
	<li>Once the pendulum has stopped, retrieve the specimen and determine the percent of area of the fractured face that has fibrous texture.</li>
</ol>

Impact testing, in the form of Charpy and Izod tests, is commonly used to measure the resistance of metallic materials to brittle fracture. The Charpy test uses a small beam specimen with a notch. The beam is loaded by a large hammer attached to a frictionless pendulum. The combination of the strain rate from this loading sequence and the presence of the V-notch that creates a local large stress concentration result in fast crack propagation and splitting of the specimen.
The test determines t...

charpy impact test of cold formed and hot rolled steels under diverse temperature conditions

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
One of the more insidious types of failures that can occur in structures are brittle fractures,which are mostly due to either poor quality materials or poor material selection. Brittle fractures tend to occur suddenly and without much material inelasticity; think of a bone fracture, for example. These failures often occur in situations where there is little ability for the material to develop shear stresses due to three-dimensional loading conditions, where local strain concentrations are high, and where a logical and direct force path was not provided by the designer. Examples of this type of failure were observed in the aftermath of the 1994 Northridge earthquake in multi-story steel structures. In these buildings, a number of the key welds fractured without displaying any ductile behavior. Fractures tend to occur near connections, or at interfaces between pieces of base materials, as welding tends to introduce local discontinuities in both, materials and geometry, as well as three-dimensional stresses due to cooling.
When specifying materials for a structure that will see very low operating temperatures (i.e., the Alaska pipeline) many cycles of loading (a bridge on an interstate highway), or where welding is used extensively, it is necessary to have a simple test that characterizes the material&#39;s robustness, or resistance to fracture. In the civil engineering field that test is the Charpy V-notch test, which is described in this lab. The Charpy V-notch test is intended to provide a very simplistic measure of the material&#39;s ability to absorb energy when subjected to an impact load.

After repeating the experiment for may specimens and temperature values, you can plot the temperature dependence of the energy absorbed and clearly see the existence of an upper and lower shelf (or flat horizontal portions). These shelves indicate that there are clear minima and maxima that can be achieved for a given material and processing. The main interest is in carefully quantifying the transition temperatures to minimize the risk that these fall within the operating temperatures of the structure being designed. Sim...

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
One of the more insidious types of failures ...

Toughness of a material can be measured using the Charpy V-notch test, a simple test that characterizes the material's robustness or resistance to fracture. Brittle failures are one of the most insidious structural failures, coming with no warning. To avoid this, applications involving very low operating temperatures, repeated cycles of loading, or extensive welding must make us of tough materials. Tough materials are much less likely to fail in a brittle manner. Toughness can be measured using the Charpy V-notch test. Testing involves hitting a notched specimen with a swinging hammer of known weight, calculating the energy absorbed by the specimen during impact, and observing the fracture surface. This video will illustrate how to perform the Charpy V-notch test and analyze the results.A tough material is one that is both strong and ductile. It can absorb more energy than materials that are less tough before failing. Along with the chemical composition of a material, changes in material processing and the loading situation can cause changes in the toughness of a material. The Charpy V-notch test is used to predict whether a material will behave in a brittle or ductile manner in se

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charpy v-notch testing of steel fracture

Charpy V-notch testing helps measure how steel handles impact before it fractures. It is a simple way to estimate a material's toughness, or its ability to absorb energy when hit suddenly. In civil engineering, this test is used to judge how likely a steel is to fail in a brittle way.

Brittle fracture is one of the most dangerous kinds of structural failure. It can happen suddenly and with little warning. The material does not bend much first, much like a bone fracture. These failures are more likely when materials are poor quality, poorly selected, or placed under conditions that limit shear stress and create high local strain.

The transcript also points to real structural problems where brittle fracture mattered. After the 1994 Northridge earthquake, several welds in multi-story steel buildings fractured without ductile behavior. Fractures often start near connections or between base materials. Welding can create local changes in material and shape, and it can also add three-dimensional stresses as the metal cools.

Because of these risks, engineers need a straightforward test for materials used in demanding settings. This includes structures exposed to very low temperatures, like the Alaska pipeline, or to many loading cycles, like a bridge on an interstate highway. The Charpy V-notch test gives a basic measure of whether a steel can resist fracture under impact loading.

Charpy V-Notch Testing of Steel Fracture

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This collection introduces students to fundamental concepts and protocols for material characterization, with specific emphasis on common construction materials such as steel, wood, and concrete.

Learn how the Charpy V-notch test measures steel toughness and helps engineers judge brittle fracture risk in welds, bridges, and cold-weather structures.

Charpy V-Notch Testing of Steel Fracture | JoVE K12

Overview

Principles of Charpy Impact Testing

Performing a Charpy Impact Test

Results

Applications

Summary

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Charpy V-Notch Testing of Steel Fracture

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