Language
Country/Area
No result found
The Difference Between Engineering Pressure and Real Pressure: Why Your Compression Test Results Might Be Wrong
In materials science, compressive strength refers to a material's ability to resist compressive loads. However, many engineers may overlook the important difference between engineering pressure and true pressure when performing compression testing. This article will take a deeper look at these differences and reveal why they may make test results inaccurate.
Basic concept of compressive strength
Compressive strength is the maximum compressive load a material can withstand before complete failure. In a standard test procedure, a material sample is subjected to gradually increasing loads in a compressor, and the load changes are recorded in relation to the deformation to create a stress-strain curve.
Compressive strength is often a key specification when designing structures, yet half of all test results reveal little about the true material properties.
Measurement and deviation
Compression strength tests are usually performed under standardized conditions, where a compression test machine applies a load to a sample and records the strain within a specific stress region. However, a very important distinction is introduced here, that of "engineering pressure" versus "real pressure".
Engineering Pressure is based on the original cross-sectional area of the specimen at the start of the test, while True Pressure takes into account the change in cross-sectional area as the compressive load is applied. The result of this variation means that the true pressure may be higher than the engineering pressure for the same load.
Engineering pressure is only an idealized concept, which fails to accurately reflect the performance of materials under actual conditions.
Effects of contact friction
When performing compression tests, friction between contact points can greatly affect the accuracy of the test results. When a specimen is restrained under pressure, its lateral expansion is inhibited, which results in a visual oval deformation called the “barrel effect” that distorts the shape of the test specimen and affects load-bearing capacity.
The presence of friction in the test induces a non-uniform stress distribution, meaning that the pressure is higher in some areas than in others.
Necessity of Correction Methods
To improve test accuracy, engineers should use several methods to correct for deviations caused by friction and geometry. For example, appropriate lubricants may be used, or materials with friction reducing properties may be used to coat the specimen and test machine contact surfaces. This promotes more even load distribution, resulting in more accurate test data.
In addition, using advanced techniques such as numerical simulation and finite element analysis, it is possible to understand the material's behavior in more detail and predict its compressive strength under different conditions. These methods can provide a more comprehensive understanding of material performance, ensuring that failures do not occur in new material development and applications.
ConclusionCompression testing is an essential part of material testing, but the accuracy of test results is often affected by the difference between engineering pressure and true pressure. Engineers must be aware of these possible deviations and take actions to reduce their effects. Have you considered these key factors to ensure the reliability of your test results?
