Duresa Conversió Gràfic, calculadora i Proves de Rockwell, Brinell, Vickers i Més

Introducció: Què és la duresa

La duresa és la propietat de qualsevol material per a resistir deformacions a la seva forma quan se sotmet a una força externa. l'assaig de duresa és important per a aplicacions tècniques i d'enginyeria, ja que ajuda a determinar la duresa i la resistència a la tracció dels materials.

Ajuda a desenvolupar una comprensió clara de si la mostra que s'està provant és adequat per a aplicacions específiques. Ajuda a les indústries perquè els productes de gamma alta qualitat segura i que compleixen amb les normes de seguretat i directrius establertes per les autoritats competents.

A continuació s'analitzen els diferents tipus de duresa i diversos mètodes de prova de la duresa i la determinació dels valors de duresa:

Duresa al ratllat

duresa al ratllat és la capacitat d'un material per resistir la deformació en general per esgarrapades i abrasions. duresa al ratllat és un tipus de duresa que es mesura quan una superfície de la mostra està ratllat per un llapis òptic que és arrossegada al llarg de la seva superfície sota una càrrega de prova fix.

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.

Aquesta prova utilitza un material més difícil de ratllar la superfície de la mostra que està fet d'un material relativament més tou. Quan es necessita per provar els revestiments, a continuació, ratllar duresa refereix a la força que és necessària per tallar a través de la pel·lícula al substrat. escala de Mohs s'utilitza per mesurar la resistència al ratllat de material juntament amb un dispositiu de mesurament conegut com sclerometer.

La duresa de indentació

duresa de penetració es refereix a la duresa d'un material que es determina en fer una osca en la seva superfície usant un penetrador apropiat sota una càrrega de prova.

READ  What is a non-destructive hardness test?

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.Visualització automàtica de torreta digital de baixa càrrega Vickers Duròmetres

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.

La duresa de rebot

duresa de rebot que també es coneix com a mesures de duresa dinàmica la duresa d'un material mitjançant la determinació de l'altura a la qual una punta de diamant rebots martell quan es deixa caure des d'una altura en l'espècimen. Aquest tipus de duresa està relacionada amb l'elasticitat.

duresa de rebot es mesura generalment mitjançant la prova Leeb rebot duresa. Aquest mètode va ser desenvolupat en 1975 per Leeb i Brandestini mitjançant l'ús d'un mesurador de duresa portàtil. Aquest provador proporciona una nova alternativa per a l'equip d'assaig de duresa tradicional generalment intricats i complexos.Visualització automàtica de torreta programat digital provador de duresa Vickers

El mètode d'assaig de duresa Leeb rebot segueix procediments estandarditzats. La velocitat del cos oscil·la entre 1,4 m / s a ​​3 m / s. Sota aquest mètode, es mesura la velocitat del cos abans i després de l'impacte per determinar la duresa de la proveta.

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.

Selecció del mètode de Millor Assaig de duresa

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

There are different types of methods for hardness testing which needs to be selected carefully for getting the most accurate and reliable hardness measurements.

Equip de microduresa Tester (semiautomàtica) per Programada Taula d'operadors
Equip de microduresa Tester (semiautomàtica) per Programada Taula d'operadors

Factors which need to be considered before selecting the ideal hardness testing methods include- the type of material to be tested, the hardness of the material to be tested, homogeneity of the material, size of the specimen, if mounting is necessary for hardness testing, thickness of the specimen, etc.

READ  How to test the hardness of copper

Assaig de duresa Rockwell

Rockwell hardness testing is the most common and fast method for testing hardness. It is generally ideal for testing hardness of larges sized samples.

It can be used either on the assembly line or in laboratories for testing hardness. It uses a steel ball or diamond-tipped cone indenter for measuring hardness depending upon the hardness of the material to be tested.

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.Duròmetre Rockwell (tipus clàssic)

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 hardness value is calculated using the conversion charts. There are nearly 30 Rockwell scales but most of the materials are covered by Rockwell C and B scales. The hardness values in Rockwell testing are represented as (example) 70 HRB where 60 is the hardness reading on the B scale.

 

Assaig de duresa Brinell

The Brinell hardness test is one of the oldest and most widely used methods for hardness testing of materials. This method was developed by JA Brinell in the year 1900. It is ideal for measuring the hardness of specimens which are too rough or course to be measured by other methods.

The Brinell method involves usage of higher test loads which can go up to 3000Kgf and a ball indenter generally 10mm in diameter.Elèctrica superficial Rockwell Duròmetre

Per al mesurament de la duresa dels metalls i aliatges més toves, càrregues de prova més petits de fins 500Kgf també s'utilitzen. La càrrega de prova per defecte s'aplica a la indentador esfèric que es manté a la superfície de la mostra en general durant 10-15 segons i després es va traslladar.

La profunditat d'indentació realitzada pel penetrador en la superfície de la mostra es mesura llavors i va estudiar usant un equip òptic avançat que assegura una millor precisió i fiabilitat.

La taula de conversió Brinell s'utilitza llavors per convertir el diàmetre mig de l'osca feta al valor de duresa Brinell corresponent. Utilitzant les taules de conversió, el valor de duresa Brinell també es pot convertir en la resistència a la tracció corresponent.

El mètode Brinell d'assaig de duresa ve amb alguns desavantatges també. L'operador pot cometre errors en el mesurament de la profunditat de indentació en la superfície de la mostra que pot afectar considerablement les mesures de duresa.

READ  What information does a hardness test reveal?

Atès que el mètode implica equip òptic avançat i sofisticat per al mesurament de la duresa de l'espècimen, és més costós en comparació amb el mètode Rockwell. També pren més temps per a la prova de duresa com necessita ser preparada abans de la prova de la superfície de la mostra.

El mètode Brinell també no funcionarà amb precisió si la superfície de la mostra és massa prima és a dir, menys de 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.

Assaig de duresa Vickers

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.Visualització automàtica de torreta digital de baixa càrrega Vickers Duròmetres

El penetrador utilitzat en aquest mètode és en la forma d'una piràmide recta. Una càrrega d'assaig s'aplica sobre el penetrador que pressiona contra la superfície de la mostra deixant d'aquesta manera una indentació.

Les longituds diagonals d'aquestes marques de indentació es mesuren utilitzant sistemes òptics, el que resulta en lectures de duresa alta precisió. La permanència temps- el temps durant el qual s'aplica la força de prova mitjançant el penetrador en la superfície- espècimen és generalment d'entre 10-15 segons en aquest mètode.

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.

Assaig de duresa Knoop

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.

 

deixa una resposta

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

Chat with us
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