Tag Archives: Flatwise

Compression testing involves crushing a sample or a component between two moving platens, either vertically or horizontally. Load and displacement are measured using load cell and extensometer or strain gages. The test helps to measure load bearing capabilities of material or component under compressive loads. Some simple examples where this property is required are design of tower structures, columns, bridge structure, etc. The test is relatively simple conduct and one can get yield strength, ultimate strength, Modulus, etc., of materials. This test is also used in assessing flow stress properties of materials, specifically metals and alloys that are required in manufacturing process like rolling, forging extrusion of metal and alloys. These tests are generally conducted at high temperatures and strain rates.

Type of Compression Testing

Compression tests are classified in to static and dynamic modes based on speed of testing. Static tests are done generally at speeds less than 1mm/ min, while dynamic tests are done at speeds > 10mm /min. Static tests are further classified in to axial and plane strain compression testing. Axial testing is conducted to gather engineering properties like yield strength, ultimate stretch, etc., used in design of equipment, structures, etc., while plane strain compression is done at high temperature to gather flow properties of metals and alloys for use in manufacturing processes like metal rolling, extrusion, forging, etc. In addition, tests like flat wise compression testing is done to evaluate the collapse properties of laminates and composites.

Specimen Geometry and Preparation

Typical specimen geometry for axial compression are cylindrical specimens of 10mm x 20mm long for metallic, ceramic and polymer materials. Plane strain compression geometry involves typically sheet type of sample with width to thickness in a ratio > 5. Flat wise compression testing of composites and laminates is done on a simple flat rectangular strip with side support to minimize risk of bucking under compression

Testing Conditions and Equipment

Most compression tests for gathering engineering properties are done at ambient conditions and low speeds <1mm/min. Occasionally such testing is done in low temperature or cryogenic region. The rate 0f loading is generally low quasi static loading conditions. These tests are done in standard test frame used for tensile testing. For high speed compression a cam type plastometer or Hopkinson bar type test units are used.

Capability – At TTL, we conduct compression testing of metals, alloys, ceramics, polymer sand composite materials for OEM customers from aerospace, automotive, power generation and mining market. We have several test frames and fixtures to do both axial and plane strain, as well as flat wise compression under static quasi static condition. For high speed compression we have drop towers for both materials and fabricated components. If required we have test cells to run static compression tests at low and high temperatures.

Some relevant standards:

• ASTM C39 – Standard test methods for compressive strength of cylindrical concrete specimen
• ASTM C365 – Standard Test Method for Flatwise Compressive Properties of Sandwich Cores
• ASTM D695 – Standard test methods for compressive properties of rigid plastics
• ASTM D642 – Standard Test Method for Determining Compressive Resistance of Shipping Containers, Components, and Unit Loads
• ASTM D1621 – Standard Test Method for Compressive Properties of Rigid Cellular Plastics
• ASTM D3410 – Standard Test Method for Compressive Properties of Polymer MatrixComposite Materials with Unsupported Gage Section by Shear Loading
• ASTM E9 – Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature