What is Compression Testing? The Theory and Applications

Compression testing is used to determine how a product or material reacts when it is compressed, squashed, crushed or flattened by measuring fundamental parameters that determine the specimen behavior under a compressive load.

These fundamental parameters include the elastic limit, which for "Hookean" materials is approximately equal to the proportional limit, and also known as yield point or yield strength, Young's Modulus (these, although mostly associated with tensile testing, may have compressive analogs) and compressive strength.

Compression testing can be undertaken as part of the design process, in the production environment or in the quality control laboratory, and can be used to:

  • Assess the strength of components e.g. automotive and aeronautical control switches, compression springs, bellows, keypads, package seals, PET containers, PVC / ABS pipes, solenoids etc.
  • Characterise the compressive properties of materials e.g. foam, metal, PET and other plastics and rubber
  • Assess the performance of products e.g. the expression force of a syringe or the load-displacement characteristics of a tennis ball

What are the Types of Compression Testing?

Types of compression testing include:

  • Flexure/Bend
  • Spring Testing
  • Top-load/Crush

What are the Benefits of Compression Testing?

Compression testing provides data on the integrity and safety of materials, components and products, helping manufacturers ensure that their finished products are fit-for-purpose and manufactured to the highest quality.

The data produced in a compression test can be used in many ways including:

  • To determine batch quality
  • To determine consistency in manufacture
  • To aid in the design process
  • To reduce material costs and achieve lean manufacturing goals
  • To ensure compliance with international and industry standards

Materials Under Compression

Certain materials subjected to a compressive force show initially a linear relationship between stress and strain. This is the physical manifestation of Hooke's Law, which states:

E = Stress (s) / Strain (e)

where E is known as Young's Modulus for compression. This value represents how much the material will deform under applied compressive loading before plastic deformation occurs. A material's ability to return to its original shape after deformation has occurred is referred to as its elasticity. Vulcanized rubber, for instance, is said to be very elastic, as it will revert back to its original shape after considerable compressive force has been applied.

Once a certain force or stress threshold has been achieved, permanent or plastic deformation will occur and is shown on graphs as the point where linear behavior stops. This threshold is known as the proportional limit and the force at which the material begins exhibiting this behavior is called the yield point or yield strength. A specimen will then exhibit one of two types of behavior; it will either continue to deform until it eventually breaks, or it will distort until flat. In either case a maximum stress or force will be evident, providing its ultimate compressive strength value.

Each of these parameters offers useful information relating to the physical characteristics of the material in question.

Some materials, such as a PET bottle, distort during a compression test and are measured by the degree of distortion, whereas other materials such as ceramics fracture, produce a definitive compressive strength value.

Applications of Compression Testing

Compression testing is used to guarantee the quality of components, materials and finished products within a wide range industries. Typical applications of compression testing are highlighted in the following sections on:

  • Aerospace and Automotive Industry
  • Construction Industry
  • Cosmetics Industry
  • Electrical and Electronic Industry
  • Medical Device Industry
  • Packaging Industry
  • Paper and Board Industry
  • Plastics, Rubber and Elastomers Industry
  • Safety, Health, Fitness and Leisure Industry

Aerospace and Automotive Industry

Applications of compression testing in the aerospace and automotive industry include:

  • Actuation tests on pedals, switches and solenoids
  • Spring testing

Construction Industry

Applications of compression testing in the construction industry include:

  • Measuring the flexural strength of sheet construction materials, insulation boards and roofing panels
  • Penetration tests on plasterboard, pipes and shotcrete

Cosmetics Industry

Applications of compression testing in the cosmetics industry include:

  • Actuation force testing of sprays and dispensing pumps
  • Break strength testing of lipsticks, lip balms, lip and eye liners
  • Compaction strength of powder compacts and eye shadows
  • Testing the force to dispense creams and lotions from containers and sachets

Electrical and Electronic Industry

Applications of compression testing in the electrical and electronic industry include:

  • Actuation force testing of push buttons and switches
  • Compression testing of LCD screens and keypads

Medical Device Industry

Applications of compression testing in the medical device industry include:

  • 3-point bend testing of needles
  • Actuation force testing of metered dose inhalers and pen injectors
  • Sharpness, insertion and penetration force testing of needles and scalpel blades
  • Syringe plunger actuation and "travel" force assessment

Packaging Industry

Applications of compression testing in the packaging industry include:

  • Compressive strength testing of cardboard packaging
  • Dispensing pump actuation force
  • Top-load testing of:
    • Bevcans
    • Cardboard and plastic containers
    • PET bottles

Paper and Board Industry

Application of compression testing in the paper and board industry include:

  • Compressive strength testing of cardboard

Pharmaceuticals Industry

Applications of compression testing in the pharmaceuticals industry include:

  • Gel strength and gel rupture testing
  • "Press-out" force of blister packs
  • Compression testing of tablets and capsules to measure characteristics:
    • Breaking
    • Coating strength
    • Crumbling
    • Hardness
    • Powdering

Plastics, Rubber and Elastomers Industry

Application of compression testing in the plastics, rubber and elastomers industry include:

  • 3-point bend testing to identify flexural properties of plastics

Safety, Health, Fitness and Leisure Industry

Applications of compression testing in the safety, health, fitness and leisure industry include:

  • Assess the performance of cricket, golf and tennis balls
  • Compression tests on car seat safety harnesses

Compression Testing Standards

There are many standards for compression testing, developed by organisations such as ASTM, BS, DIN, ISO and MIL.

They include:

  • ASTM C864-05, ASTM D575-91, D905-98, D1710-02, D6147-97, D6713-01, ASTM E9-89a, ASTM F628-06
  • BS 7325:1990, BS EN 2591-612:2001, BS EN 12365-2:2003, BS EN 61300-2-11:1997, BS EN 61212-2:1996, BS ISO 844:2001
  • IEC 61300-2-11:199
  • ISO 7743:2008, ISO 9895:1989, ISO 15527:2007

Compression Testing Systems Available from Mecmesin

From simple test stand and gauge combinations up to fully computer-controlled systems powered by Emperor® software, Mecmesin compression testing machines offer varying grades of sophistication at an affordable price.

MultiTest-i Compression Testers from Mecmesin

Mecmesin's top-of-the-range MultiTest-i compression testers, driven by Emperor™ force testing software provide full programmable control and a suite of comprehensive evaluation tools for performing a vast array of compression tests.

Emperor's flexible programming structure gives you the freedom to design and customise tests to suit your specific requirements. With almost limitless capabilities, Emperor will provide detailed information about your tests, enabling you to evaluate your products or materials performance throughout its life-cycle.

Features of Emperor™ force testing software include:

  • Ideal for R&D and Quality Control Labs
  • High speed data capture - 2000 Hz
  • Run to load, displacement or time
  • Intelligent command functions provide limitless test flexibility
  • Operator prompt / delay / resume test facility
  • Extensive suite of calculations e.g. peak and average
  • Loadcell deflection compensation
  • Auto-loadcell recognition / configuration
  • Real-time graphs with zoom and label function
  • Automatic export to Excel and SPC packages

A range of capacities are available to meet your exact testing requirement, from the single column MultiTest 1-i through to the advanced twin-column 50-i, which has been specifically designed to test large or high load samples and products.

MultiTest-xt Compression Testers from Mecmesin

Operated via an easy-to-use touch screen, Mecmesin's MultiTest-xt compression testers are the ideal solution for fast and efficient routine testing on the production floor.

The MultiTest-xt requires minimal training to begin performing quick, accurate in-line production tests, with the press of just two buttons. Clear colour-coded pass/fail indicators allow smooth, efficient quality control checks, whilst a range of calculations provide ample data interrogation options.

Features of MultiTest-xt compression testers include:

  • User-friendly touch screen interface
  • Easy-to-use, requires minimal set-up & training
  • Flexible - choice of 3 program modes
  • Create and store multiple test programs
  • 5 'Favourite' buttons for fast access to frequently used tests
  • Measures force and displacement
  • Colour-coded Pass/Fail indication
  • Ideal for routine use in production areas
  • Self-contained system - no PC required
  • Capacities from 1kN to 50kN

MultiTest-dV Compression Testers from Mecmesin

Mecmesin's entry-level MultiTest-dV test stands are a cost-effective solution for straightforward compression tests.

Features of MultiTest-dV compressie testers include:

  • Simple to operate
  • Combines with Mecmesin's digital gauges; AFG & BFG
  • Rugged design suitable for factory floor
  • Combines with data acquisition software for additional test evaluation options
  • Capacities from 1kN to 2.5kN

Manual Compression Testers from Mecmesin

For simple compression testing applications a Mecmesin manual test stand, such as an MDD used with either a Basic Force Gauge (BFG) or Compact Force Gauge+ (CFG+) offers an affordable solution.

Grips and Fixtures for Mecmesin Compression Testers

Mecmesin grips and fixtures are integral components of our test systems and Mecmesin has a comprehensive range of grips and fixtures to meet your compression testing application and budget.

Mecmesin supplies many specially designed grips to ensure consistent test performance, repeatability and minimal sample movement.

Compression plates are one such example where variants are available for specific applications, a few of which are:

  • Self-leveling: for applications where parallel alignment is critical.
  • Hardened and ground: have a smooth, scratch-resistant surface. Ideal for tests that might damage a normal compression plate such as springs.
  • Vented: for crush/top-load testing of containers, such as PET bottles. Circular vents allow air to escape from the container during compression, and an integrated nose cone helps to position containers centrally, minimising bottle slippage.

Fixtures are also available for applications involving flexure/bend tests and spring tests. Spring supports maintain vertical alignment of springs during compression testing, improving the level of safety for the operator and accuracy of results. Three and four-point bend jigs are engineered to support samples in the correct position for flexure testing.

For specialised requirements Mecmesin's team of experienced application engineers can design customised fixtures to match your specification.

Summary

Mecmesin has a range of compression testing systems used to perform a wide variety of test applications. Whatever your budget, Mecmesin compression testing machines offer varying grades of sophistication at an affordable price to ensure you:

  • Optimise your designs
  • Ensure consistency in manufacture and improve your productivity
  • Bring products to market faster to maximise growth in turnover and profit
  • Reduce material costs and achieve lean manufacturing goals
  • Ensure products are manufactured to international standards and industry specifications.

This information has been sourced, reviewed and adapted from materials provided by Mecmesin Limited.

For more information on this source, please visit Mecmesin Limited.

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