Hörku viðskipta Mynd, Reiknivél og Próf fyrir Rockwell, Brinell, Vickers og meira

Inngangur: Hvað er Harka

Harka er eign hvers konar efni til að standast aflögun lögunar sinnar þegar það er tekið til ytri krafta. Harka próf er mikilvægt fyrir tæknifólk forrit eins og það hjálpar til við að ákvarða hörku og togstyrk af efni.

Það hjálpar til við að þróa skýra skilning á því hvort sýnið er prófað er hentugur fyrir ákveðin forrit. Það hjálpar atvinnugreinum til að gera öruggt og hár-gæði endir vara sem uppfyllir öryggisreglur og leiðbeiningar mælt er fyrir um viðeigandi yfirvöldum.

Mismunandi tegundir af hörku og ýmsar aðferðir við að hörku prófanir, og ákvarða hörku gildin eru rædd hér á eftir:

Scratch Harka

Scratch hörku getu efni til að standast aflögun yfirleitt með rispum og sár. Scratch hörku er ein tegund af hörku sem er mældur þegar sýni yfirborðið er klóra af stíll sem dregin eru eftir yfirborði hennar undir föstu próf álag.

Scratch hardness method defines the resistance of a material to plowing by a hard stylus. It measures the hardness of the material and its ability to resist scratches and abrasions. Generally, a scratch hardness tester consists of a stylus, portable sample holding stage, load-applying device, and a data processing and display unit.

The earliest scratch hardness tests were conducted by Friedrich Mohs in 1820 who also developed the Mohs scale. The scratch hardness test measures the resistance of the specimen to fracture or permanent deformation due to friction caused by the stylus along its surface.

Þetta próf notar fara verr efni til að klóra frá sýninu í yfirborði sem er gerður úr tiltölulega mýkri efni. Þegar þú þarft til að prófa húðun, þá klóra hörku átt við gildi sem er nauðsynlegt til að skera í gegnum kvikmynd á undirlag. Mohs kvarði er notað til að mæla klóra mótstöðu af efni ásamt fyrir mælibúnað þekktur sem sclerometer.

inndrátt hörku

Inndrátt hörku er átt við hörku eru úr efni sem er ákvarðað með því að gera inndreginn á yfirborði þess með því að nota viðeigandi indenter undir prófunarhleðslu.

READ  How to test the hardness of plastic

There are many different indentation testing methods which measure the depth of indentation made on the specimen surface for measuring its hardness. Indentation hardness tests can be further subdivided into two categories- macro indentation tests and micro-indentation tests. Macro indentation tests make use of large test loads in excess of 1Kgf and can go up to 3000Kgf in some cases.Sjálfvirk virkisturn Digital Display Low Load Vickers hörku Tester

The prominent type of macro indentation testing methods includes Rockwell hardness testing method, Brinell method, Vickers test, Knoop hardness testing method, etc. Micro-indentation testing, on the other hand, is used for measuring the hardness of soft metals, thin and small specimen, etc.

The test loads applied for micro-indentation hardness tests are much lower and can range between 1 to 1000gf. Micro-indentation tests can be used for measuring changes in hardness on a microscopic scale. Vickers method and Knoop hardness testing methods are two popular micro-indentation hardness testing methods.

Indentation hardness tests can be prone to errors. The main sources of errors while measuring hardness include poor technique, improper calibration of the testing equipment, improper finishing of the specimen surface, etc. The test surface needs to be free from any dirt, oxidation, or lubrication to get reliable estimates of hardness. The indenter should also be perpendicular to the specimen surface as any inclination will result in faulty hardness measurements.

rebound harka

Rebound hardness which is also known as dynamic hardness measures the hardness of a material by determining the height to which a diamond-tipped hammer bounces when it is dropped from a height on to the specimen. This type of hardness is related to elasticity.

Rebound hardness is generally measured using the Leeb rebound hardness test. This method was developed in 1975 by Leeb and Brandestini by using a portable hardness tester. This tester provided a new alternative to the usually intricate and complex traditional hardness testing equipment.Sjálfvirk virkisturn Sérstilling Digital Display Vickers hörku Tester

The Leeb rebound hardness testing method follows standardized procedures. The velocity of the body ranges between 1.4 m/s to 3 m/s. Under this method, the velocity of the body before and after the impact is measured to determine the hardness of the specimen.

The ratio of the impact velocity to the rebound velocity gives the dynamic Leeb hardness of the test specimen. The object used for making the impact on the specimen can be tungsten carbide cobalt, ceramic or diamond, or a ball-shaped indenter with different radius.

The sample hardness determined by this method is represented as (example) 750 HL D in which 750 denotes the hardness value, HL denotes “Hardness according to Leeb” and D represents Leeb method with spherical impact body of tungsten carbide-cobalt with a radius of 1.5 mm and weight of 4.5 grams.

Val á bestu Hörku prófunaraðferð

The hardness of a material depends on a number of factors like homogeneity of the material, type of material, its size, and condition.

Það eru mismunandi tegundir af aðferðum til að hörku próf sem þarf að vera valið vandlega til að fá sem mest nákvæmar og áreiðanlegar hörku mælingar.

Computer Míkróharka Tester (Semi-sjálfvirk) til að forrita Carrier töflu
Computer Míkróharka Tester (Semi-sjálfvirk) til að forrita Carrier töflu

Þættir sem þarf að huga að áður en að velja hið fullkomna hörku prófunaraðferðir include- tegund efnis að prófa, hörku efnisins sem prófa skal, einsleitt efni, stærð sýnis, ef fara þarf um hörku próf, þykkt á lífveru, etc.

READ  What is Moh’s hardness test?

Rockwell hörku Test

Rockwell hörku próf er algengasta og fljótur aðferð til að mæla hörku. Það er almennt tilvalið fyrir próf hörku stærsti stór sýni.

Það er hægt að nota annað hvort á færiband eða í rannsóknarstofum til að prófa hörku. Það notar stál boltanum eða demantur-áfengi keila indenter til að mæla hörku eftir því hörku efni til að prófa.

Til að hefja Rockwell próf, minniháttar álag á almennt 10Kgf er beitt á indenter. The indenter færist þá undir prófunarhleðslu á til the sýnishorni yfirborðið. Þó að indenter er enn undir áhrifum minniháttar próf álag, til viðbótar stórt próf álag er einnig beitt til þess. Þetta tryggir betri inndrátt á eintak yfirborðinu sem er skýr og mælanleg.

The Rockwell aðferð við hörku próf er vinsæll eins og það er ekki fyrir áhrifum af annaðhvort hlutdrægni rekstraraðilans eða ójöfnur á yfirborðinu sem harka er verið að prófa.

It does not make use of any sophisticated or costly optical equipment for measuring the hardness of specimen, which makes it a cost-effective method for hardness testing. It is a non-destructive method for hardness testing which means that the sample specimen being tested is not destroyed and it can be used for other purposes after the testing procedure is completed.Rockwell hörkumæli (classical Type)

This method has its drawbacks also as it is not very accurate compared to other methods of hardness testing. Small deviation in measuring the indentation depth can throw off the hardness readings considerably.

If the indenter in this method is worn out, then it can provide faulty hardness measurements which are non-reliable.

Rockwell hörku gildi er reiknað með því að nota eður töflur. Það eru næstum 30 Rockwell vog en megnið af efnum fellur undir Rockwell C og B vog. Fyrir hörku Gildin í Rockwell prófunum, eru fulltrúa sem (dæmi) 70 HRB þar sem 60 er hörku lestur á B mælikvarða.

 

Brinell hörku Test

Brinell hörku próf er einn af elstu og mest notaðar aðferðir til hörku prófun efna. Þessi aðferð var þróuð af JA Brinell árið 1900. Það er tilvalið til að mæla hörku sýnum sem eru of gróft eða námskeið til að mæla með öðrum aðferðum.

Brinell Aðferðin felst notkun hærri prófunarhleðslu sem getur farið upp í 3000Kgf og boltinn indenter almennt 10mm í þvermál.Electric Surface Rockwell hörku Tester

For measuring the hardness of softer metals and alloys, smaller test loads of up to 500Kgf are also used. The predetermined test load is applied to the spherical indenter which is held to the specimen surface for generally for 10-15 seconds and then moved.

The indentation depth made by the indenter on the specimen surface is then measured and studied using advanced optical equipment which ensures better accuracy and reliability.

The Brinell conversion chart is then used to convert the average diameter of the indentation made to the corresponding Brinell hardness value. Using the conversion charts, the Brinell hardness value can also be converted into the corresponding tensile strength.

The Brinell method of hardness testing comes with few drawbacks also. The operator can make mistakes in measuring the indentation depth on the specimen surface which can considerably impact the hardness measurements.

READ  Difference between Rockwell, Vickers and Brinell Tests

Since the method involves advanced and sophisticated optical equipment for measuring the specimen hardness, it is costlier compared to the Rockwell method. It also takes more time to test hardness as the specimen surface needs to be prepared before testing.

The Brinell method will also not work accurately if the specimen surface is too thin i.e. less than 9.6 mm.

The hardness readings using the Brinell method are represented as 600 HBW where 600 denotes the hardness value and HBW denotes “Brinell Hardness” with tungsten ball indenter. If steel ball indenter is used then the readings will be represented as 600 HBS where HBS denotes “Brinell Hardness” with steel ball indenter.

Vickers hörku Test

The Vickers test uses the same principle as the Brinell method with the only exception being the type of indenter being used.

The type of indenter needs to be changed under the Brinell method depending on the type of material being tested. However, the same diamond indenter is used in the Vickers method for measuring the hardness of all specimen types.Sjálfvirk virkisturn Digital Display Low Load Vickers hörku Tester

The indenter used in this method is in the form of a right pyramid. A test load is applied on the indenter which presses itself against the specimen surface thereby leaving an indentation.

The diagonal lengths of these indentation marks are measured using optical systems, resulting in highly accurate hardness readings. The dwell time- the time for which the test force is applied through the indenter on the specimen surface- is generally between 10-15 seconds in this method.

The Vickers test using micro-test loads which are much lesser compared to the Brinell method. It is a microhardness testing method which is best suited for measuring the hardness of materials which are too thin or small for macro hardness testing.

This method is best suited for measuring the hardness of thin sheets of metals, small specimens, etc. The Vickers test is a non-destructive method which ensures that the specimen can be used after the testing is complete. There are a few limitations of the Vickers method.

It requires the specimen surface to be free from any imperfections and thus time is needed for preparing the specimen surface before conducting the test. It takes at least 30-60 seconds for conducting this test and the time is exclusive of the time taken for preparation of the specimen surface.

Vickers testing is not recommended for bulk production in assembly lines and is more suited for laboratory testing. The hardness measurements in the Vickers test are represented as 700 HV/10 where 700 is the Vickers hardness value which has been arrived at by using a 10Kgf test force.

Knoop hörku Test

Knoop hardness testing method is an alternative to the Vickers method. It is a microhardness measuring method which is suitable for measuring the hardness of fragile and brittle materials like ceramics. It is also useful for hardness testing of small elongated areas like coatings.

The Knoop method also uses a pyramidal diamond as indenter, but the indenter is elongated instead of being a right pyramid as in the Vickers method. Since the method is used for hardness testing of fragile materials, it uses micro loads of up to 1Kgf.

The indenter used in this method penetrates the specimen surface only half as deep as in the Vickers method, which makes it perfect for hardness testing of the brittle specimen.

Due to the shape of the indenter, the Knoop method is better suited for measuring longer elongated specimens like coatings. It is important to note that the specimen surface should be prepared properly before conducting the Knoop test for ensuring accurate and reliable hardness measurements.

 

Skildu eftir skilaboð

Your email address will not be published. Required fields are marked *

Spjallaðu við okkur
Chat with us
Leave a Message & We will reply within 12 Hours!
Connecting...
Leave a Message & We will reply within 12 Hours!
Leave a Message & We will reply within 12 Hours!
:
:
:
Leave a Message & We will reply within 12 Hours!
:
:
This chat session has ended
Was this conversation useful? Vote this chat session.
Good Bad