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Textiles
Textile Expert

 

 

Kashish Anand has been in the industry for 3.5 years and mentored in Textile testing applications with our global textile partner SDL Atlas. He has developed a good understanding of textile standards and tests by working through the globe and experiencing industry trends.

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Metals & Construction


Shawn Byrd is a Technical Manager at Tinius Olsen Testing Machine Co. in Horsham, PA, US. Shawn is a member of the following ASTM International Committees, D30 on Composite materials, E28 on Mechanical Testing and F16 on Fasteners. These groups have over 900 members combined and are responsible for 204 standards. Shawn is also involved with ASTM working on collaborative projects with colleges and professional industries.

 

  • Testing in Construction FAQ
  • CLARIFICATION ON ACCEPTANCE CRITERIA AS PER IS-456

    Dear Sir,

    We have tested 190 concrete cube samples (190 X 3 speciments) taken during batching of concrete at batching plant from 01.10.10 to 15.11.10.The quality of ingredients like sand, aggregate,cement and water used for manufacturing concrete were of same quality. The concrete mixer is having capacity of 0.5 M3. My questions are :

    Q No. 1. How I shall identify a 'Batch' of concrete.

    Q No. 2. While calculation Standard Deviation, test result of first 30 samples (acceptable as per Cl. 15.4) have to be considered (say sample no.1 to 30). For calculation S.D. for next 30 samples (sample no. 31 to 60) shall I consider only 30 samples or 60 samples (sample no.1 to 60) together and so on.

    Q No. 3.As per Cl. 16.1 a) Mean strength from any group of four cubes (ammendment no.3) have to be considered :- From where shall I start grouping ? shall I satrt from start date like 1-4,5-8,9-12 etc. ? Please clarify.

    Q No. 4. Suppose sample no.1,2,3 (01.10.10) are from individual foundations and 4-10 (02.10.10) are from one single foundation and 11-16 (03.10.10) are from another single foundation. Grouping is made taking 1-4, 5-8,9-12 ,13-16.Now, if group 1-4 fails (as per Cl.16.1a) but 5-8 passes then what will be the fate of the single foundation (sample no. 4-10).

    I shall be oblised if you kindly clarify my doubts.

    (Manas Sarkar)

    B.C.E.

     

    Dear Manas,

    Q.No.1 “Batch” theoretically means the quantity of concrete mixed at one time. But for the purpose of Quality Control, we do not have to test every batch of concrete. The frequency of sampling and how to ensure that the samples are representative is described in Clause no. 15.2.

    Q.No.2 The Clause 15.4 means that we have to cast three specimens of concrete from each sample. (Please notice the difference between samples and specimens). The three specimens are to be tested at the same time. If the results of all three specimens are within 15 percent of each other, then the test is valid and the average value for that sample should be recorded. If not, the results of thissample should be rejected. In case, the Specifications say that the Standard Deviation of 30 samples is to be calculated, then these have to be 1 to 30 and 31 to 60 and so on.

    Q.No.3 From the averages of four, it is implied that they can be any four consecutive samples, that is 1 to 4, 2 to 5, 3 to 6 and so on. The acceptance criterion is given in Table no. 11 of the same code.

    Q.No.4 If there are doubts regarding the integrity of the structure, we should resort to Non Destructive Testing. The suggestion in such cases is, that since the correlations between Rebound Hammer Values and the Ultrasonic Pulse Velocity depend on the quality of sand, cement and aggregates, the tables and charts given in books or manufacturers are not very reliable. If we carry out these tests every time we conduct a compression test, we can have our own data base which is based on our own cement, sand and aggregates. We can then use this data base with confidence. Some of the results going out of specified limits does not spell disaster and does not mean replacement of concrete. Structure should be tested in such cases.

    I trust this answers your question.

    Sincerely,

    Dr. Sharma

  • I am a railway engineer. I am retired Dy Chief Engineer. I am now a internal consultant for railway private sidings. Some bridges are also constructed. My question is what should be the frequency of testing of concrere?

    To keep control on the quality of concrete produced, it is required to cast a number of specimens from random samples and test them at suitable intervals. Indian Standard IS: 450-2000 stipulates that random samples from fresh concrete shall be taken as specified in IS: 1199-1959 and cubes shall be made, cured and tested at 28 days as described in IS:516-1959. The test result of a sample should be the average of the strength of three specimens (constituting the sample). The individual variation should be no more than ± 15 percent of the average. If it is more the test result of the sample is invalid. The random sampling procedure is adopted to ensure that each concrete batch shall have a reasonable chance of being tested i.e. the sampling should be spread over the entire period of concreting and cover all mixing units.

     

    The Indian Code of Practice prescribes minimum frequency of sampling of 1,2,3 and 4 number of samples respectively, for 1-5, 6-15, 16-30 and 31-50 cubic meters of concrete being used in the job.

     

    For concrete quantity of 51 cubic meters and above, the number of samples shall be 4 plus one additional sample for every 50 cubic meter of concrete or part thereof. At least one sample should be taken from each shift. In case of continuous production e.g. ready mix concrete plant, the frequency of sampling may be as per agreement. Additional samples may be required for various purposes such as 7 days strength, accelerated tests, time of striking formwork etc.  

     

    As far as the requirements of specifications with regard to the acceptance criteria is concerned, IS: 456-2000 stipulates that the mean strength be related to the grade and the standard deviation of any four non-overlapping  consecutive test samples.

  • Do Tinius Olsen have an air Permeability unit I need a Blaine type BS 4359, the glass U tube on my existing unit has cracked and I cannot get a replacement?

    Yes we do make the Blaine type air permeability unit based on BS 4359. It is a fairly standard item and there should not be any problem in supplying a spare glass u-tube

  • Hi I work in a lab doing QA tests on concrete cubes and cylinders, we are looking into prism block testing should I use ASTM C39 as my pint of reference? And are there any recent changes I should consider?

    Yes, the method given in the ASTM C39  "Standard Test method for Comressive Strength of Cylindrical Concrete Specimens" can be used for testing concrete specimens of prismatic shape. If the requirement is of compressive strength only, there are no extra precautions to be taken, other than those required normally for cylindrical specimens.

  • I have an old Forney type dial compression machine, can Tinius Olsen help me with a retro fit or upgrade, I need to get a digital display on the unit?

    Yes it can be done. Tinius Olsen can definitely help in the matter. Please send the relevant details to info@tiniusolsen.com

  • Is it true that the finer the grain of the concrete mix, the stronger the resultant concrete will be?

    It is true that the finer the grain, the higher the strength of resultant concrete. But this is only half the story. Finer grains (like those of Silica fume) help in filling up voids of concrete which are otherwise filled by air. We need higher sizes of aggregate also to get strength. The aggregates should be well graded and larger the maximum size of aggregate the smaller the quantity of cement to get the same strength. Thus for the same cement quantity, maximum size of aggregate will give a higher strength provided the aggregate is well graded.

    Thus to get maximum strength for a given quantity of cement we should have finer particles as well as higher sized particles and all aggregate should be well graded.

  • Microdeval Testing Machine - BS EN1097-1 standard

    Dear Mr.Sharma,

    Greetings of the day.

    We, M/S. SAIF BIN DARWISH is the leading producer of aggregates, different sizes of rocks, road base, sub base and armour rocks for concrete, Highways, infrastructure and backfilling projects in United Arab of Emirates.

    We are in the need of Micro-Deval Testing Machine -  BS EN1907-1 standard. since you are producing wide range products, we look forward to get best offer for Micro-Deval testing machine at the earliest.

    Thanking you.

    With best regards,

    Anbu Johnson, Asst.Quarry Manager, SBD Crushers, Siji, Fujairah, United Arab of Emirates

     

    Dear Mr. Johnson

    While we do manufacturer a wide range of testing equipment for concrete, cement, aggregate, soil and asphalt testing, unfortunately, at present, we don't have a Micro-Deval Testing machine in our Product Range.

    Sincerely

    Dr shrama

  • Dr Sharma I am in purchasing Saudi Arabia - could you please tell me what basic items should I be looking for in a fresh concrete test set? The QA manager here says we are testing in accordance with ASTM C138, 143, 192, 231 and 470

    The ASTM 138 deals with the Test Methods for Density, Yield and Air Content of Concrete

    The equipment required is 

    1. Balance

    2. Tamping Rod

    3. Internal Vibrator

    4. Measure - A cylindrical containe made of steel or other suitable material

    5. Strike off Plate

     6. Mallet

    Similarly you may look at the other standards mentioned in your letter and find out the equipment required. In case of any difficulty please do let me know.

  • Please explain the procedure of use of elongation & flakiness gauges?

    The properties of fresh and hardened concrete depend on the shape of the aggregates as well as other characteristics. The shape of three dimensional bodies is difficult to describe, it can be simplified by describing certain geometric characteristics such as the flakiness and elongation index. These are defined as follows;

     

    Flakiness Index is the percentage by weight of particles in it, whose least dimension  (thickness) is less than three-fifths of its mean dimension. The test is not applicable to particles smaller than 6.3 mm in size.

     

    Elongation Index  is the percentage by weight of particles in it, whose largest dimension (length) is greater than one and four-fifths times its mean dimension. The test is not applicable to particles smaller than 6.3 mm in size.

     

    Procedure for using Gauge for Flakiness Index

    A balance of suitable capacity, gauge for Flakiness Index and a set of Sieves of relevant sizes as  per the specified Standard  will be required.

     

    Sample size will be such that at least 200 pieces of any fraction to be tested will become available. The aggregates will be dried to a constant weight in an  oven at a temperature of 110º ± 5ºC and  weighed to the nearest 0.1g. The aggregates will then be sieved  through the set of prescribed sieves.

     

    Each fraction is then gauged for thickness through the slots of the gauge. All the pieces passing through the gauge are collected and weighed to an accuracy of 0.1 percent of the weight of the sample.

     

    The Flakiness Index is the total weight of the material passing various gauges and sieves expressed as a percentage of the total weight of the sample gauged.

     

    Elongation Index

    Similar procedure is used for the determination of Elongation Index. Sample is first dried and then sieved through the set of Standard Sieves. Each fraction is then gauged through the slots of the Elongation Gauge. The Elongation Index is the total weight of the material retained on the various length gauges expressed as a percentage of the total weight of the sample gauged.

  • Testing of foundation

    Dear Sir,

    We are into the bussiness of Construction of Transmission Line towers, which needs a lot of concrete work.

    Currently our projects are running in Nagpur,Yawatmal in Maharashtra (India), Hence I was looking for an agency for testing of foundation at site.

    Can you do help about it ???

    Regards

    Farooq Ahmed

     

    Dear Farooq,

    Thank you for you inquiry. Unfortunately we only manufacture and sell the testing equipment, we don't perform any testing services, additionally, I'm not familiar with any independent test houses close to your projects. Sorry I can't help you further...

  • Tinuis Olsen testing machine load rate

    I am working in laboratory as lab technician and i am using the T.O. machine in testing materials.

    My question is as the load is controled with a load valve, but what does the numbers indicate ie 0 to 50 

     

    The test machine is as shown below.

     TINIUS OLSEN UTM 2000KN CAPACITY MODEL AC8500 S/N 1****0

     

    The machine you've referenced is a 400,000lbf capacity Deluxe Super L hydraulic testing machine with extra height and a low base. The machine was made in 1970 and was sold to a customer in Australia. I assume you refer to the graduations behind the loading capstan - these numbers have no significance other than as a guide to open the capstan to, to approach a similar loading rate for each test. As the hydraulic oil heats up, the loading rate will change and will need to be adjusted, so these graduations were simply there as a helpful guide for operators.

  • The smell of concrete would obviously depend upon its ingredients, but in general it smells like fresh lime put in water. I do not know how to describe its smell but a good concrete smells good

    According to classical indian literature the quality of soil can be judged by its taste and smell. A good soil suitable for foundations smells like sandal wood. A bad soil smells like a rotten egg. Probably it was an indication of organic matter present in the starta !

  • What is the difference between concrete and mortar?

    The difference between the concrete and the mortar is due to the size of aggregates present. Whereas in mortars we use only fine aggregates, that is sand or its equivalent, in concrete we use both fine and coarse aggregates.

    It is well known that the strength of concrete depends on the the maximum size of aggregates, beside other factors. Therefore if concrete can be used in a given situation, it should be used in preference to mortar as it would work out cheaper.

  • What is the range of slump for ordinary design mix and pumpcrete design mix?

    Regarding the Slump – normal concrete slump is about 2 inches (50 mm). For Concrete that need to be pumped, these values are about 4 to 5 inches that is 100 to 125 mm. These values depend on the amount of sand and size of aggregates in the mix. Some guidance is given in the table below.

    Recommended Slumps for Various Types of Construction

     

        Concrete Construction                                                     Slump (in inches)

                                                                                            Maximum               Minimum

    1. Reinforced foundation walls and footings                          3                           1
    2. Plain footings, caissons, substructure walls                        3                           1
    3. Beams and reinforced walls                                            4                           1
    4. Building columns                                                           4                           1
    5. Pavement and slabs                                                      3                           1
    6. Mass concrete                                                              2                           1

     

    For Concrete Mixes that are to be Pumped

     

    Maximum Size of Aggregate                     9 mm     18 mm   25 mm   37 mm     37 mm

    Percent of Sand                                         60          43             45           39             40

    Cement (Pounds per Cubic Yard)               565          525            525        510           565

    Slump, inches                                             4          3 to 4           5          3 to 4      3 to 4

     

    I trust this answers your question.

  • What is the toughest grade of concrete?

    Whereas the grades of concrete commonly used have strengths varying  from 15 to 35 Mpa, but for special purposes special concretes are manufactured. They include the use of silica fume, fibre reinforcement and polymers. Concretes having strengths upto 125 Mpa have been produced to the best of my knowledge. As you can imagine these records are broken every now and then.

Plastics

 

Harold E “Harry” Yohn serves as Product Applications Specialist for Tinius Olsen Testing Machine Co. in Horsham, PA, US. Harry has been with the company since 1996. He has 26 years of experience in the field of mechanical and physical testing of plastics .In 1990, Harry became a member of ASTM International Committee D20 on Plastics, and he is now a vice chair of the committee (Programs), a group of about 1000 members responsible for 473 standards. He is also Subcommittee chairman for D20.30 on Thermal Properties of Plastics and chair of D20.10.02 Impact Properties as well as chair of several task groups within the committee.

 

 

Hardness


 

 

Sean Malloy serves as Product Applications Specialist for Tinius Olsen Testing Machine Co. in Horsham, PA, US. Sean joined the company in 2011 and brought his years of industrial experience with him. Sean supports our hardness testing equipment product line and has been through months of intensive training and is ready to answer your questions.

 

  • Testing Hardness FAQ
  • Can I use a carbide ball indenter on a block that wasn't calibrated with a carbide ball?

    Yes, you can but your reading will be lower, up to 1 point lower than normal.

  • How do I know when to replace my test block?

    Here are a few things that will help you decide when to replace your test block

    1. Signs of rust or oxidation
    2. Space - not enough room to perform an indentation (Distance from indentations 2 to 3 times the diameter of the indentation, based on the ASTM/ISO standard block was calibrated to)
    3. Under carriage of test block being marred (top side of test blocks should only be used for indentations)
    4. Dropping the test block on the floor.
    5. Surface is no longer the same finish as originally provided. (test blocks should not be refinished/resurfaced)

    Certified test blocks are an efficient way of checking the accuracy of your machine. With daily use of test blocks, it is possible to determine issues with your machine prior to compromising test samples.

  • If I'm not sure of the hardness of a material. What Rockwell scale should I use?

     If the sample is very thin, start with HR30N. If the sample is thick, try the HRA scale. Both scales use a diamond indenter. It is difficult to damage a diamond indenter. You can adjust the scale based on your results. A Hardness Conversion chart will assit you with adjusting to another scale based on the initial results. Information regarding the hardness chart can be found ASTM E-18. Contact ASTM on the WEB at www.astm.orghttp://www.astm.org or by asking your loacel Tinius Olsen rep for our wall posters of conversion charts.

  • What would assist me in choosing between Vickers or Knoop testing?

    The Vickers indenter is a diamond ground to the shape of a square based pyramid with an angle of 136 degrees between faces. The depth of the indent it makes is about 1/7 of its diagonal length. The Vickers indenter penetrates about twice as far into the specimen as the Knoop indenter. Therefore, the Vickers test is less sensitive to surface conditions than the Knoop test. Because the indent is influenced less by the flatness and parallelism of the top and bottom specimen surfaces and their finish, it can be used on materials that are not suited for Knoop testing. However, because of the greater depth of the indent, the Vickers test is not as suitable for testing very thin foils and other materials as is the Knoop test. For equal loads, the Vickers indent (because of its shorter length) is more sensitive to errors in measuring the indent.

    If you are trying to decide between Vickers or Knoop testing, you have already made the decision of using a light load/force to perform your test. If you understand how the indenters are designed, making this decision can be made quickly. The Vickers diamond is a pyramid design with an angle of 136 degrees on all four sides. This design is to penetrate the surface deeper than a knoop indenter. This allows the surface prep to not affect the readings as much as it would a knoop test.

  • Are the ranges the same for every Rockwell Scale?

    At the low hardness end of a ball scale the ball may penetrate too deeply causing the cap to come into contact with a specimen which would damage the cap. In the case of a diamond indenter the sensitivity of the test diminishes as the diamond indenter penetrates further down the conical portion of the diamond. At the high end of the hardness scales, these limits result from the likelihood of fracturing or reducing the life of a diamond indenter such as testing carbide on C scale as opposed to the recommended A scale. A ball indenter is likely to have a flat spot as a result of testing above HRB95.

  • Can you describe a Knoop indenter and what it is used for?

    The Knoop indenter is an accurately ground diamond forming a rhombic based pyramid. An indent seen perpendicular to the specimen surface is rhombic in outline with diagonals having an approximate ratio of 7 to 1. Because of the Knoop indenter's geometry, indents of accurately measurable lengths are obtained with light loads. The depth of the indent is about 1/30th of the length of the long diagonal. Because of this it is well suited to testing very thin layers of plating case hardened steel, thin metal and foils, thin layers of decarburization and hard, brittle materials. The indenter is very sensitive to the flatness of the specimen's surface, the parallelism of the top and bottom surfaces, and especially to the degree of surface finish.

  • How frequently should I have my tester verified/calibrated/PM'd?

    Good Question. The answer can be found in the standard to which you follow for your testing (ASTM / ISO).  you can also Check with your Quality dept. The majarity of machines are verified/calibrated once a year. Ultimately you get to decide. We have seen quarterly, every six moths, annually, and 18 month intervals.  The P/M should be found in the instruction manual provided with your machine. It is usually cost effective to combine P/M with your calibration.

  • How often do I need to have my test block calibrated?

    There is no published specification at this time which mandates block recalibration

  • How often should I have my Rockwell tester calibrated. I do HRC and HR45T.

    Hi John,

    Calibration or Verification is performed following the standard you are testing to. The most commonly used standars are ASTM E18 and ISO  6508-1. If you are following ASTM E18, you would have three differnt types of verification:

    1. Direct verification
    2. Indirect verification
    3. Daily verification

    The Direct verification is typically performed when your machine is made and when repairs are made that could affect the application of the test force. See ASTM E18 for specifics.

    Indirect verification, as per ASTM E18, is recommended when the machine arrives to your facility new, approximately every 12 months, but should be no longer than 18 month interval. This verification could be shorter. Typically your Quality Dept. would make this determination.

    Daily verification is self explanatory. This verification is required by ASTM E18 after changing any or all of the following: the indenter, test force or anvil.

    I would recommend getting a copy of ASTM E18.

    I hope this information helps

  • Is there a table or chart that lists typical material types that are suitable for testing on Rockwell scales?

    Yes the table is found in ASTM E-18. Contact ASTM on the WEB at www.astm.orghttp://www.astm.org There is also a materials testing Web site at www.matweb.comhttp://www.matweb.com . You can get the same chart and conversion posters from your Local Tinius Olsen Sales Rep

  • The material that I am testing is too thin causing dents on the underside of the specimen. Can I stack several of these test pieces on top of each other to increase the thickness?

    No, stacking one or more additional layers of metallic material together can not make up for an insufficient material thickness. The material flow between the layers will produce inaccurate measurements.

  • The readings on my tests are running a few points high.

    Make sure you have the proper load selected. If you have too light of a load selected, the indent will be considerably shallow.

  • What could cause bad results from my hardness tester?

    Knowing what machine is being used and your definition of "bad" results, would help me be more specific answering your question. Here is a few general areas to check and rule out as the cause.

    The use of certified test blocks can help you determine if the readings are higher or lower than they should be. Here are a few suggestions based on the results on certified test blocks.

    If your results are higher than expected:

    1. Is correct load selected?
    2. Verify the dwell time is not too short
    3. Is the indentor/ penetrator damaged
    4. Dead weight tester - do weight move freely

    Results are lower than expected

    1. Dirt /rust/grease on stage
    2. Dirt/rust/grease on sample or test block
    3. was p/m performed, and to much grease was applied to the spindle
    4. check the bearings for the spindle
    5. Was the correct load applied 
    6. Verify the dwell time 
    7. If it's a micro tester, are you too close to the indenter (Typically you need to be in focus with an objective, then the distance should be correct)

    The list above is generalized, but might be a good start. Knowing the tester being used, testing scale, and the results can help in correcting your issue.

    If you need more specific information, you can contact at : info@tiniusolsen.com

  • What is the depth of penetration for Regular Rockwell scales?

    One Rockwell number represents a penetration of .002mm (0.000080 in.) Therefore, a reading of HRC 60 indicates a penetration from minor to major load of (100 - 60) X 0.002mm = 0.080 mm or 0.0032 in. A reading of HRB 80 indicates a penetration of (130 - 80) X 0.002 mm = 0.100 mm or 0.004in. Note: The numbers 100 and 130 above are the infinite hardness numbers for those scales.

  • What is the depth of penetration for Superficial Rockwell scales?

    One Superficial Rockwell number represents a penetration of 0.001 mm or 0.000040 in. Therefore, a reading of 30N80 indicates a penetration from minor to major load of (100 - 80) X 0.001 = 0.020 mm or 0.0008 in. Note: The number 100 used in the calculation is the infinite hardness number used for all Superficial scales.

  • What is the difference between Micro and Macro Vickers?

    Micro indentation uses loads from 10grams to 1000grams. Macro indentation uses loads above 1000 grams.

  • What is the difference between Rockwell and Vickers ?

    The easy answer is Rockwell tests produces a hardness value base on a depth measurement, Vickers tests are primarily based on a opticle measurement to produce a hardness values.

    Rockwell and Vickers tests are hardness tests that can be performed on the same types of samples (size and thickness will vary). The Rockwell test uses a specific load (Rockwell Scale dependant) applied through an indenter or penetrator,  pressing into the sample for a specific amount of time. The time is boken down to 3 segments: the preload (lighter load), main load (heavier load), and the recovery load (lighter load). the change in depth of the penetrator from the end of the preload to the end of the recovery load coorelates to a hardness value.

    Vickers tests differs from Rockwell by not measuring hardness by depth but optically measuring the indentation (measured length, times measured width, divided by two, to produce a mean dimension or D1 x D2/2= mD) via  high powered microscope. This measurement then coorelates to the hardness value in Vickers. Vickers tests only apply load once for loanger dwell time (10-14 seconds) then Rockwell (Total time is typically 8 seconds or less).

    Vickers tests can be performed with low loads of 20 grams to 120 Kgf,  this allows the ability to test thinner samples.  Rockwell loads are 15 Kgf to 150 Kgf for the main load and 3 Kgf or 10 Kgf for preload and recovery load.

  • Why should I use verification blocks and are they all the same?

    Verification blocks are used to check your hardness tester for accuracy. It is good practice to perform a verification daily, that is if you are using the tester everyday. Better stated, use the verification block before each time the tester is used. If the Verification block is certified, you can trust the results and identify if your hardness tester is performing in top condition. ASTM and ISO have specific requirement for the use of verification blocks, the when and how. I would recommend following the recommendations of the standard you are following with tyour testing. Make sure to have a certificate with your veryification block. This certificate will have the information to help identify the perform of your tester on this block. It is good practice to use a low and high value block for the same scale being tested. This will allow you to verify the range of your tester in the scale your are using. All test blocks are not the same. Make sure the test block has a Certificate, that shows calibration performed to ASTM or ISO guidelines.

 

 

 

 

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