November 22, 2019

Tensile Testing & Materials Testing Guide

What is Tensile Material Testing or Compression Testing?

A tensile test which is also sometimes called a tension or pull test, is one of the most basic and normally destructive tests you can perform on a material. The material is subjected to a controlled force in tension, (pulling apart), until ultimately it breaks.

The results from a tensile test are used to help engineers select the correct material for a particular application, or in quality control during the manufacturing process. While pulling on the material, you can find out how its strength is compared to how much it will elongate.

A Universal Testing Machine or Tensile Tester can also be used for performing the tests in compression as well, so not only you can pull something apart, you can crush or compress it as well

What can Tensile Material Testing or Compression Testing show me?

A huge amount of information can be learnt about a particular material or substance from tensile or compression testing. As you pull or push on the material until it breaks, you can obtain a tensile or compressive profile. The resulting curve will show how the material has reacted to the forces being applied. The point in which the sample fails, is often of great interest and is referred to as the Ultimate Strength or UTS.

Hooke’s Law

Most materials that are tested using a Tensile or Universal Testing Machine, will show to begin with a linear relationship between the applied force (stress) and the elongation (strain) of the sample tested. In this linear region of the test, the line obeys the relationship that is defined as “Hooke’s Law” where the ratio of stress to strain is constant or.

Hookes Law

E is the slope of the line in this region, where stress (σ) is proportional to strain (ε),This is referred to as the modulus of elasticity or Young’s Modulus

Young’s Modulus, Elasticity Modulus or Tensile Modulus

Modulus of elasticity is a measure of stiffness, but only, of the linear region of the curve. If the material specimen has the load applied within its linear region, it will return to its same shape and condition when the load is removed. At the point where the curve no longer shows linearity, therefore deviates from the straight line relationship, Hook’s Law no longer applies, so some permanent dimensional deformation will occur. This point is called the elastic or proportional limit. From this point, the specimen reacts plastically to any increase in load or stress. The material will not return to its original, un-stressed condition, size or shape, if the load is removed.

Yield Strength or Yield Point

This is the point in which a material stops deforming elastically and starts to deform plastically, therefore when the load is removed it doesn’t return to its original condition.

Offset Yield Point or Proof StressTensile Test

For some materials the yield point is not easily identified, e.g. some plastics and metals. An offset method is then used to calculate the yield strength. BS A4 Part 1, BS EN 10002 and ASTM E8, provide a detailed method for metals, and ASTM D638 for plastics. The offset is specified as a percentage of the strain, this usually 0.2% for metals and 2% for plastics.

The Stress “R” is determined from the intersection point “r” when the line of the elastic region is drawn from offset “m” becomes the yield strength by the offset method.

The tensile curves of certain materials do not have a well-defined linear region. In this case there are alternative methods of determining the modulus of the material as well as the Young’s Modulus.These are the secant modulus and the tangent modulus.

Strain

This is expressed in two main ways, Engineering strain and True strain. Engineering (sometimes called Cauchy) strain, is the most common expression of strain. It is expressed as a ratio of the total deformation of the initial dimension to the original length. Strain

The True strain is similar but is based on the instantaneous length of the specimen as the test progresses

Strain 2 Li is the instantaneous length and Lo is the initial length.

Ultimate Tensile Strength (UTS)

Ultimate Tensile Strength which is often shortened to tensile strength (TS) or ultimate strength, is the maximum load a specimen sustains during a test. This is not necessarily equated to the strength at the break of the specimen. Some materials are brittle, ductile or some may even exhibit both properties.

Stress Strain Graph

AML Instruments range of Tensile Testers can be configured and supplied with the correct fixtures and grips to enable them to perform a multitude of different tests and they can also test many different materials and substances.

Paper and Board Tensile Material Testing

The Tensile Strength of paper and board is critical to many converting and manufacturing processes, such as printers, carton manufactures and tissue products. Stringent tolerances are set by customers of the paper mills to ensure the paper or board will run correctly through their machinery and will produce a quality product for the end user.

The tensile strength of paper is usually expressed as kN/m and the machine is set to move the grips at a constant rate of elongation (speed). The sample which is a strip, normally has a width of between 15mm to 25mm.

Tensile index = tensile strength/grammage, quoted in Nm/g

Tensile Energy Absorbed TEA

Another test often performed is the tensile energy absorbed. This is calculated from the area under the load / elongation curve, the units of the test are J/m²

Wet tensile tests for paper are performed in accordance with BS 2922/2

In the manufacture of tissue products, puncher, dry and wet tensile tests (Finch method) are often required. These tests are performed to the requirements of British standard and International standard BS EN ISO 1925/4 and BS EN ISO 1925/5

Crush and Compression Resistance Testing

CCT Concora Crush Testing

Concora or corrugated crush testing is used to determine the edge profile compression strength of an fluted strip of a corrugating paper. in a Laboratory The Tappi T824 covers this method and the results are expressed in the units kN/m

ECT Edge Compression Testing

ECT is used to determine the load bearing strength of corrugated board to loads that act in parallel to the fluting. The BS EN ISO 3037 gives details of this method; results are expressed in the units kN/m.

FCT Flat Crush Testing

FCT testing is used to determine the load bearing strength of corrugate board to loads that act perpendicular to the fluting. The British Standard BS EN 23035 and International Standard ISO 3035 give details of this method; results are expressed in the units kPa.

RCT Ring Crush Testing

RCT is used to determine the compressive strength of paper and board. A round sample of material is inserted into an annular groove is loaded until failure; results are expressed in the units kN/m

Tensile and Compressive Tests on Polymers (Plastics)

Compression Test On A BottlePolymers play a vital part in everyone’s life in the 21st century. Some of the uses include, packaging, automotive, healthcare, construction, aerospace and electronics.
There are many different tensile and compressive tests possible and even more standards available from different standards institutes around the world. Below is a list of the main standards used in industry. AML will of course help you select the best test and relevant standard for your testing needs.

Tensile BS 2782:3 methods 326A-326C

Tensile strength and elongation BS 2782:3, ASTM D638, ASTM D882, ISO 527-1,2,3, ISO 1798, ISO 1926, JIS K7127, JIS K7161, JIS K7162

Flexural: ASTM D790, ASTM D6272, JIS K7017, JIS K7171

Compression ASTM D695, ASTM D1621, ASTM D3846, ISO 844, ISO 604, JIS K7092, JIS K7181

Dynamic / Fatigue: ASTM F1614

Determination of the bearing strength of rigid plastics: ASTM E1012

Peel, Tear and Coefficient of Friction (CoF):ASTM D903, ASTM D1894, ISO 8067, BS ISO 8295, ISO 6383-1, ISO 11897, JIS K6854-2, JIS K7125, ISO 7886-1

Shear: ASTM D3163, ISO 8067

The tensile properties of polymers (plastics) that are regularly measured are tensile strength, yield strength, % elongation, elastic modulus and tensile energy absorbed.

Tensile and Compressive Tests on Metallic Materials (metals)

Tensile Testing

What is Tensile or Compressive Testing

There are a huge range of standards that cover the tensile and compressive tests of metallic (metals) Below are a list of the most common ones.

StandardDescription
ASTM B598This standard covers the determination of the yield strength (0.01%, 0.02%, and 0.05% offset), at room temperature. It is intended for copper alloys in tempers commonly used for spring applications, and materials thicker than 0.010 in. (0.25 mm).
ASTM E209This standard covers the method, equipment, and specimens for compression tests on metallic materials.
ASTM E21This standard covers the method and equipment for the determination of tensile strength, yield strength, elongation, and reduction of area of metallic materials at elevated temperatures.
ASTM E238This standard covers the a pin-type bearing test of metallic materials to determine bearing yield strength and bearing strength.
ASTM E292This standard covers the determination of the time for rupture of notched specimens under conditions of constant load and temperature
ASTM E345This standard covers the tension testing of metallic foil at room temperature in thicknesses less than 0.006 in. (0.150 mm).
ASTM E8This standard covers the tension testing of metallic materials in any form at room temperature, in particular the methods of determination of yield strength, yield point elongation, tensile strength, elongation, and reduction of area.
ASTM E9This standard covers the apparatus, specimens, and method for axial-load compression testing of metallic materials at room temperature.
BS 4A 4-1.2:1967This standard covers the specification for test pieces and test methods for metallic materials. Tensile tests. Tensile tests – elevated temperature. Metric units
BS 4A 4-1.3:1967This standard covers the specification for test pieces and test methods for metallic materials. Tensile tests. Uninterrupted creep and rupture tests. Metric units.
BS EN 10002-1:2001This standard covers the tensile testing of metallic materials. Method of test at ambient temperature.
BS EN 10002-5:1992This standard covers the tensile testing of metallic materials. Method of test at elevated temperatures.
BS EN 10319-1:2003This standard covers metallic materials. Tensile stress relaxation testing. method for testing machines.
BS EN 13523-7:2001This standard covers coil coated metals. Test methods. Resistance to cracking on bending (T-bend test).
BS EN 23312:1993, ISO 3312:1987This standard covers Sintered metal materials and hard metals. Determination of Young’s modulus.
BS EN 23327:1993, ISO 3327:1982This standard covers hard metals. Determination of transverse rupture strength.
BS EN ISO 7438:2000This standard covers metallic materials. Bend test.
BS EN ISO 7500-1:2004This standard covers metallic materials. Verification of static uniaxial testing machines. Tension/compression testing machines. Verification and calibration of the force-measuring system
BS EN ISO 7622-2:1996This standard covers steel cord conveyor belts. Longitudinal traction test. Measurement of tensile strength.
BS EN ISO 8491:2004This standard covers metallic materials. Tube (in full section). Bend test.
BS EN ISO 8496:2004This standard covers metallic materials. Tube. Ring tensile test.
EN ISO 7438This standard covers metallic materials. Bend test.
ISO 10113This standard covers metallic materials. Sheet and strip. Determination of plastic strain ratio.
ISO 10447This standard covers resistance welding. Peel and chisel testing of resistance spot and projection welds.
ISO 1099This standard covers metallic materials. Fatigue testing. Axial force controlled method.
ISO 3327This standard covers hard metals. Determination of transverse rupture strength.

 

Metal products and materials that are regularly undergo Tensile and Compressive testing are:

 

  • Wires & Cables
  • Ropes & Chains
  • Metal Fabrications
  • Sheet metals
  • Machined components
  • Fasteners such as, screws, bolts, nails etc.
  • Castings
  • Steel plates
  • Pipes & Tubes
  • Welds

Some tests that are performed on metallic materials (metals) are:

  • Compression
  • Flexure
  • Fatigue
  • Peel
  • Tear
  • Friction (coefficency of friction COF)
  • Shear
  • Cyclic
  • Tension
  • Tensile
  • Torsion

Adhesive tensile and compressive testing

The use of adhesives is common place, from the use in:

  • Packaging
  • Books and magazines
  • Building and construction
  • Automotive
  • Aerospace
  • Medical
  • Adhesive tapes

Standards and test methods used for adhesive tensile testing:

 

  • ASTM C633 Adhesion or Cohesion Strength of Thermal Spray Coatings
  • ASTM D1335 Tuft Bind of Pile Yarn Floor Coverings
  • ASTM D903 Adhesive Bonds, Peel or Stripping Strength
  • ASTM F2458 Wound Closure Strength of Tissue Adhesives and Sealants
  • EN 1465 Lap Shear Strength, Adhesives, Rigid to Rigid Bonded Assemblies
  • EN 1719 Tack Measurement Pressure Sensitive Adhesives Loop Tack
  • EN 1939 Peel Adhesion Self Adhesive Tapes
  • FINAT Test Method 2 Peel Adhesion 90°
  • ISO 11339 T-Peel Test Flexible to Flexible Bonded Assemblies
  • ISO 2411 Coating Adhesion Rubber-Coated Plastics-Coated Fabrics
  • ISO 4587 Adhesives Tensile Lap Shear Strength Rigid to Rigid
  • ISO/TS 11405 Tensile Adhesion and Bond Strength of Dental Materials and Adhesives
  • ASTM D1335 Tuft Bind of Pile Yarn Floor Coverings
  • ASTM D1876 Peel Resistance for Adhesives, T-Peel Test
  • ASTM D903 Adhesive Bonds, Peel or Stripping Strength
  • ASTM F2256 Strength Properties of Tissue Adhesives by T-Peel Testing
  • EN 1719 Tack Measurement Pressure Sensitive Adhesives Loop Tack
  • EN 1939 Peel Adhesion Self Adhesive Tapes
  • FINAT Test Method 2 Peel Adhesion 90°
  • ISO 11339 T-Peel Test Flexible to Flexible Bonded Assemblies
  • ISO 36 Rubber Vulcanized and Thermoplastic Adhesion to Textile Fabric

AML Instruments of Lincolnshire East Midlands supply a huge range of Tensile Tester, Universal Testing Machines and Compression Testers which with the range of over 2000 Grips and Fixtures we also supply can perform just about any test imaginable.

Looking for information on our extensive range of Tensile Testers and Universal Testing Machines click on the links

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