In other words where the bending moment changes its. In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero line. A 4 point flexure fixture produces peak stresses along an extended region of the specimen hence exposing a larger length of the specimen with more potential for defects and flaws to be highlighted. Explanation: Contra-flexure contra (opposite) + flexure (bending) In a bending beam, a point is known as a point of contra flexure if it is a location at which no bending occurs.
In four-point bending a uniform maximum moment and an area of tension at the bottom of the specimen is achieved. This localization of stress is ideal for testing for specific isolation of stress on a component or material.įour-point bending is used effectively to measure the bond strength. The 3 point flexure fixture produces its peak stress at the specimen mid-point with reduced stress elsewhere. Bending tests vary greatly based on the product being tested.
The materials that are tested using the flex test method vary from metal, plastic, wood, laminates, particle board, dry wall, ceramic tile, to glass. Two types of bending tests are generally used to determine flexural stress and flexural strain, the 3 point bend and 4 point bend.
Or, it may involve bending a material until the material experiences a break and determining both the load and deflection required to initiative the break limit. Bending tests may involve taking the sample material to a specific limit and determining the load measurement and its relationship to a load specification (pass/fail). A component’s or material’s flexural strength provides high level of understanding into the modulus of elasticity in bending, flexural stress and flexural strain.īend testing measures the ductility of materials. such as ASTM D790, a three-point flexure for plastics, which uses a standard 16:1 span-to-thickness ratio or ASTM D6272 which is a four point flexure. As the demand for high quality and reliable components and materials increases, flexural or bending tests have become an important test method in both the manufacturing process and research and development to define a material’s ability to resist deformation under load.
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