Cantilever Impact Tester Operation Principle

Material impact detection, introduced to the operating principle of the cantilever beam impact testing machine complex and changeable, Jinan Yongmao Machinery Co., Ltd. Technical Department careful analysis of the program to carefully understand.

The determination of impact strength of plastics in China is generally conducted using simple beam impact testing machines and cantilever beam impact testing machines. Samples can be divided into two types: no-notch and notch, which can be completed by automatic notch sampler and manual notch sampler. A notched impact test simulates the impact of materials under harsh conditions.

During the impact test, the pendulum was hung from the vertical position on the arm of the rack and lifted the lift arm by a lift angle α. The pendulum gained a certain level of energy. Release the pendulum, allow it to fall freely, break the spline placed on the support, and when it is raised up in the opposite direction, push the pointer and read the work A that was consumed to break the sample from the dial reading to calculate the impact. strength:

(kg?cm/cm2)

b, d are the width and thickness of the sample, respectively, and for the notched sample, d is the remaining thickness of the removed notch. The value read from the scale is the work consumed by the impact sample. This also includes the sample's "fly-out work", expressed as a relation:

W is the pendulum weight, L is pendulum length, α and β are the lifting angles before and after the pendulum impact, A is the power consumed by the impact sample, and Aα and Aβ are the pendulums to overcome the air within the α and β angle respectively. The power consumed by the resistance; for the "fly-out work," it is generally believed that the last three items can be ignored and can therefore be abbreviated as:

For a fixed instrument, α, W, L are known, the tester can thus draw a reading plate according to the β size, and directly read the power consumed by the impact sample. In fact, the part of the fly-out work is different due to the different conditions of the test sample, and the test equipment has different conditions, sometimes accounting for 50% of the reading A. In brittle materials, the flying work is often very large, and the flying power of a thick sample is also larger than a thin sample. Therefore, when the test conditions are not the same, the numerical values are often difficult to quantitatively compare and are only suitable for the comparison of the same material under the same measurement conditions.

The part of the energy absorbed by the fracture of the sample appears to be an area phenomenon on the surface. In fact, it involves how large the volume of energy that participates in the absorption of impact energy is a volume phenomenon. If a certain material generates a segment motion under a certain load (yield strength), and thus increases the number of segments participating in the external force, that is, the volume of the impact absorbing energy increases, its impact strength becomes large.

Generally brittle materials are mostly face-to-face type fractures, while tough materials are mostly irregular fractures, and whitish near the fractures. The volume involved is large. If the tough material does not break after impact, but has been destroyed, the impact strength is expressed as "continuous".

Because the test is performed at a high speed, impurities, bubbles, micro cracks, etc. have a great influence, so the conditions of the samples before and after the measurement must be carefully observed.