Hardheid Gesprek Chart, sakrekenaar & Toetse vir Rockwell, Brinell, Vickers en Meer

Inleiding: Wat is Hardheid

Hardheid is die eiendom van enige materiaal om vervorming sy vorm te weerstaan ​​wanneer dit blootgestel aan 'n eksterne krag. Hardheid toets is belangrik vir tegniese en ingenieurstoepassings, aangesien dit help om die hardheid en treksterkte van materiaal te bepaal.

It helps to develop a clear understanding of whether the specimen being tested is suitable for specific applications. It helps industries to make safe and high-quality end products which meet the safety regulations and guidelines laid down by the relevant authorities.

The different types of hardness and various methods of hardness testing and determining the hardness values are discussed below:

kras Hardheid

Scratch hardness is the ability of a material to resist deformation usually by scratches and abrasions. Scratch hardness is one type of hardness which is measured when a specimen surface is scratched by a stylus which is dragged along its surface under a fixed test load.

Kras hardheid metode definieer die weerstand van 'n materiaal te ploeg deur 'n harde pen. Dit meet die hardheid van die materiaal en sy vermoë om skrape en skaafplekke te weerstaan. Oor die algemeen, 'n skrapie hardheidstoetser bestaan ​​uit 'n stylus, draagbare monster hou stadium,-load toepassing toestel, en 'n verwerking van data en vertoning eenheid.

Die vroegste nuuts hardheid toetse is uitgevoer deur Friedrich Mohs in 1820 wat ook ontwikkel die Mohs-skaal. Die krap hardheidstoets meet die weerstand van die monster te breek of permanente vervorming as gevolg van wrywing veroorsaak word deur die stylus langs die oppervlak.

Hierdie toets gebruik 'n harder materiaal om die monster oppervlak wat bestaan ​​uit 'n relatief sagter materiaal krap. Wanneer jy nodig het om 'n deklaag te toets, dan krap hardheid verwys na die krag wat nodig is deur die film aan die substraat te sny. Mohs-skaal word gebruik vir die meet van die kras weerstand van die materiaal saam met 'n meettoestel bekend as hardheidsmeter.

inkeping Hardheid

Inkeping hardheid verwys na die hardheid van 'n materiaal wat bepaal word deur die maak van 'n inkeping op die oppervlak met behulp van 'n toepaslike indenter onder 'n toets lading.

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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.Outomatiese rewolwer digitale display Lae load Vickers Hardheid 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.

Die toets vragte toegepas vir mikro-inkeping hardheid toetse is baie laer en kan wissel tussen 1 tot 1000gf. Mikro-inkeping toetse kan gebruik word vir die meet van veranderinge in hardheid op 'n mikroskopiese skaal. Vickers metode en Knoop hardheid toets metodes is twee gewilde mikro-inkeping hardheid toets metodes.

Inkeping hardheid toetse kan vatbaar vir foute wees. Die belangrikste bronne van foute terwyl meet hardheid sluit in swak tegniek, onbehoorlike kalibrasie van die toets toerusting, onbehoorlike afwerking van die monster oppervlak, ens Die toets oppervlak moet vry wees van enige stof, oksidasie, of smeer om betroubare skattings van hardheid kry. Die indenter moet ook loodreg op die monster oppervlak wees as enige neiging tot gevolg sal hê in foutiewe hardheid metings.

rebound Hardheid

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.Outomatiese rewolwer Geprogrammeerde digitale display Vickers Hardheid 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.

Kies die beste Hardheid toets metode

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

Daar is verskillende tipes van metodes vir hardheid toets wat moet versigtig gekies word vir die kry van die mees akkurate en betroubare hardheid metings.

Rekenaar microhardness Tester (semi-outomatiese) vir Geprogrammeerde Carrier Table
Rekenaar microhardness Tester (semi-outomatiese) vir Geprogrammeerde Carrier Table

Faktore wat oorweeg moet word voordat die kies van die ideale hardheid toets metodes sluit in- die tipe materiaal wat getoets moet word, die hardheid van die materiaal om getoets te word, homogeniteit van die materiaal, grootte van die monster, as bevestiging is nodig vir hardheid toets, dikte van die monster, ens

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Rockwell hardheidstoets

Rockwell hardheid toets is die mees algemene en 'n vinnige metode vir die toets hardheid. Dit is oor die algemeen ideaal vir toetsing hardheid van larges grootte monsters.

Dit kan gebruik word óf op die vergadering reël of in laboratoriums vir toetsing hardheid. Dit maak gebruik van 'n staal bal of diamant-tipped keël indenter vir die meet van hardheid, afhangende van die hardheid van die materiaal om getoets te word.

To start the Rockwell test, a minor load of generally 10Kgf is applied on the indenter. The indenter then moves under the test load on to the specimen surface. While the indenter is still under the influence of the minor test load, an additional major test load is also applied to it. This ensures better indentation on the specimen surface which is clear and measurable.

The Rockwell method of hardness testing is popular as it is not influenced by either the operator’s bias or the roughness of the surface whose hardness is being tested.

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 Hardheid Tester (Klassieke Tipe)

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 hardheid waarde is bereken deur die omskakeling kaarte. Daar is byna 30 Rockwell skale maar die meeste van die materiaal gedek deur Rockwell C en B skale. Die hardheid waardes in Rockwell toets verteenwoordig as (byvoorbeeld) 70 HRB waar 60 is die hardheid lesing op die B skaal.

 

Brinell hardheidstoets

Die Brinell hardheidstoets is een van die oudste en mees gebruikte metodes vir hardheid toets van materiale. Hierdie metode is ontwikkel deur JA Brinell in die jaar 1900. Dit is ideaal vir die meet van die hardheid van monsters wat te rof of kursus word gemeet deur ander metodes is.

Die Brinell metode behels die gebruik van 'n hoër toets vragte wat kan gaan na 3000Kgf en 'n bal indenter algemeen 10mm in deursnee.Elektriese Oppervlakte Rockwell Hardheid 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.

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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 hardheidstoets

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.Outomatiese rewolwer digitale display Lae load Vickers Hardheid 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 Hardness Test

Knoop hardheid toets metode is 'n alternatief vir die Vickers metode. Dit is 'n microhardness meet metode wat geskik is vir die meet van die hardheid van broos en bros materiale soos keramiek. Dit is ook nuttig vir hardheid toets van klein langwerpige gebiede soos coatings.

Die Knoop metode gebruik ook 'n piramidale diamant as indenter, maar die indenter is verleng in plaas daarvan om 'n regte piramide as in die Vickers metode. Sedert die metode wat gebruik word vir hardheid toets van broos materiaal, dit maak gebruik van mikro vragte van tot 1Kgf.

Die indenter wat in hierdie metode dring die monster oppervlak net die helfte so diep as in die Vickers metode, wat dit ideaal vir hardheid toets van die bros monster maak.

As gevolg van die vorm van die indenter, die Knoop metode is meer geskik vir die meet van meer verleng monsters soos 'n deklaag. Dit is belangrik om daarop te let dat die monster oppervlak behoorlik moet bereid wees om voor die afneem van die Knoop toets om te verseker akkurate en betroubare hardheid metings.

 

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