Analysis of multi-axial impact tests of automotive plastic materials أداة الاختبار –

Multi-axial impact test analysis of automobile plastic materials

Automobiles facilitate people\'s travel, and their safety performance is the focus of people\'s attention. Car bumpers are safety devices that absorb and mitigate external impact forces and protect the front and rear of the body. 20 years ago, the front and rear bumpers of cars were mainly made of metal materials. They were stamped from a U-shaped steel profile with a thickness of more than 3 mm. The surface was chrome-plated, riveted or welded to the longitudinal beam of the chassis and had a large cross-section with the bodywork. The gap is like an added element. With the development of the automobile industry, automobile bumpers, as an important safety device, have also embarked on the path of innovation. In addition to their protective functionsoriginal, the front and rear bumpers of today\'s cars also seek harmony and unity with the shape of the body, as well as their own lightness. In order to achieve this goal, the front and rear bumpers of cars began to use plastic materials, called plastic bumpers. The impact resistance requirements of this plastic material are very good. So how do you test the impact resistance of plastic materials? This article presents a commonly used multiaxial impact test method.
Multi-axial impact is mainly used to test the impact resistance of polymer materials such as plastics. Taking a car bumper as an example, multi-axis impact measures the strength of the bumper, its deformation when loaded, and the overall energy absorption of the bumper when \'impact. This method can confirm whether a car\'s bumper has a certainn protective effect in the event of a road accident.
Multi-axis impact testing equipment mainly consists of multi-axis bench (falling weight block, falling weight and fixing device) and hot and cold box (this equipment ranges from -50℃~150℃, using liquid nitrogen refrigeration) and a set of data collection software.
The workThe principle of ng is to make the hammer head vertically impact the center of the sample surface at a standard speed to obtain the impact force distance curve or time curve. According to the curve record and the surface condition of the sample after impact, the condition and performance of the material can be judged. The sample must remain fixed during the test.
The impact head of the multi-axis impact equipment (Figure 1 and Figure 2) is a hemispherical hammer head with a smooth surface. There are 2 types of hammer heads: the diameter is de (20.0 ± 0.2), which meets ISO 6603, ISO 7765-2 standards. ASTM D5628, GMW14867 and other methods; the diameter is (12.7 ± 0.2) mm, meeting the testing standards of ASTM D3763, ASTM D5628 method FD, ASTM D7192, GMN10083 and other testing standards. The impact weight of this instrument is 12.7 kg. It is equipped with a total of 4 weight blocks, each weighing approximately 6.73 kg. The total impact mass can reach around 40 kg. During the impact test, the impact speed was about 2.5m/s-4.4m/s±0.1m/s, and the corresponding drop height was 300mm-1000 mm.
The standard sample is a disc with a diameter of 60mm or 140mm or a square with a side of 60mm or 140mm, and the inner diameter of the corresponding clamping device is 40mm or 100mm. The samples are generally made of injection molding materials, and their thickness is generally 2mm to 3mm. If some samples differ by 5% of the average thicknessne of the batch of samples, these samples will be rejected.
Before carrying out the impact test, the sample must be placed in the test chamber and conditioned at the specified temperature for at least 3 hours. When performed in non-ambient temperature conditions, cooling or heating temperatures may affect results. Each sample should be measured at three equidistant points in a circle with a central radius of 10 mm and the difference in thickness is approximately 0.02 mm.
Automotive interior parts include dashboards, sub-instruments, door panels, pillars, glove boxes, etc. In particular, dashboards and door panels have large surface areas, small wall thicknesses and complex structures, which require materials with excellent rigidity and toughness. Excellent rigidity can ensure that the interior parts will not deforment when installed on the body frame and during use; while excellent toughness, especially low temperature toughness, can guarantee the safety of drivers and passengers. If the low temperature resistance is poor, under very cold climatic conditions, the interior parts of the car will crack or even produce fragments during a collision, endangering the safety of drivers and passengers. Therefore, automobile interior parts must meet certain low temperature impact resistance requirements, especially low temperature impact performance from 0℃ to 30℃.
In order to improve the low temperature impact properties of materials, manufacturers often add a large amount of reinforcing agents during the production process, but this also reduces the stiffness of the material. For example, the flexural modulusand thermal deformation temperature are reduced, and stiffness and strength are not achieved. Thermal performance requirements. At present, the low temperature (-30°C) Izod impact resistance of polypropylene dashboard materials is generally about 4kJ/m2, but it will break under multi-impact conditions. axial of 6.6 m/s and -30°C.
With the continuous improvement of performance requirements for automobile interior parts, the requirements for multi-axis low temperature impact are also increasing and higher. The high-velocity multi-axis impact specimen is used to calculate the total energy absorbed by the specimen during specimen rupture. If it breaks during high-speed impact, it cannot meet the usage requirements of the material.
As a quick and accurate method to identify the impact resistance of materials, multi-axis impactis currently widely used in automobile material verification. CTI Automotive Mater\'s laboratory has this testing capability and, as a flagship project, it is at the forefront of the industry.

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