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Scratch resistance testing of automobile interior and exterior parts

Author:QINSUN Released in:2023-09 Click:103

Scratch resistance testing of automobile interior and exterior trim parts

At present, scratch resistance testing is a routine testing item for quality control surface of automobile interior and exterior trim parts. Changes that occur when hard objects (keys, coins, etc.) are scratched and other environmental stresses occur, such as leaving scratches on the surface of paint and plastics, causing discoloration and changes shine and cause hairs on the surface of fabrics.

Test principle:

The basic principle of the five-finger scratch resistance tester is that the scratching head acts on the surface of the sample to be tested with a certain pressure, and at the same time the scraping head and the test The sample moves relative to each other at a certain speed, and the trajectoryof movement is usually a straight line (or a circle). Then the scratched part of the test sample surface is visually inspected or measured with an instrument to determine the corrosion resistance of the test sample.

Test sample:

The sample for scratch test should be flat. This may be a specially manufactured test sample using the same process as the product, or it may be obtained from parts and components. Cut out the flat areas.

Test method:

1. When relative movement, the scraping head can move and the test sample does not move;
2. Head scratching The test sample does not move while the test sample moves;

3. In a test, some only require one scratch on the head sample to be tested, and some require repeated scraping several times, or on different partsof the test sample. Scratching, resulting in multiple scratches.

Evaluation of the results:

Main observations: whether there are scratches on the appearance, whether the surface is distorted and whether there are color changes and shine.

Five-finger scratch resistance test method:

A five-finger scratch resistance tester is used. The test sample is installed on the instrument test bench, with five scraping rods (commonly known as five-finger mounting bracket, the scraping rod can be easily assembled and disassembled. Its scraping tip is spherical and generally has two specifications, with a diameter of 1mm or 7mm. It can be assembled according to requirements. Loads are installed above the scraping rods. Different loads are usually installed on the five scraping rods, such as a set of 15.0 N, 10.0 N, 7.0 N, 3.0 N., and loads of 2.0 Nor a set of 20.0 N, 15.0 N, 13.0 N, loads of 8.0 N, 5.0 N, etc. When testing, all five scraping rods cannot be used. Scraper rods can be suspended or uninstalled. to the corresponding positions as needed. During the test, the tip of the scraping rod is placed on the surface of the test sample under load. The surface can freely float up and down with the surface. There are two ways current instruments achieve strumming motion. One is that the scraping rod moves horizontally and the test sample does not move. The other is that the scraping rod remains horizontally stationary and the test sample moves horizontally. The scraping distance is generally 100-200mm, the scraping speed is 100mm/s.

Visual evaluation method:

Usually the tested sample is placed under the illumination of sunlight from the skyNordic or artificial light source D65, and the test sample is in a horizontal state relative to the evaluator. If necessary, rotate the sample to be tested to obtain the best viewing angle. For linear scratches, the 10% parts at the start and end of the scratch line are not considered and only the middle 80% part is evaluated. The evaluation results can be mainly divided into the following situations: < br />
a. Only evaluate whether there are damaging scratches on the surface of the test sample, such as cracks, material deformation, scratches exposing the substrate, hair, etc. ;

b. When using different loads in a multiple pass scratch test, observe each scratch line and determine the maximum load that will not scratch the surface of the test specimen;

c. Rating assessment. Different standards and differentrents materials have inconsistent definitions of rating levels. For example, for plastic samples, the regulations are very detailed. The tested damages are divided into three situations and the levels are specified respectively. The three types of damage are: scratches, i.e. deformation or cracking of the surface; bleaching (Discoloration), i.e. the scratched area can be seen turning white or discolored from different angles; scratches, that is, the surface has a change in gloss or polishing phenomenon, but not deformation or whitening.
For textiles, grades are specified based on the degree of lint accumulation, and there are even illustrated standards to guide judgment.

Scraping head:

The material, shape and size of the scraping head are often decisive for the scratch test method. Different methods ofThe scratch test have different scratch test methods. Wiping your head is usually different. Here are some commonly used scraping heads.

a. Hemispherical or spherical tip. The commonly used diameters are 1mm, 0.75mm, 0.5mm, made of steel, and the surface is heat treated to meet certain hardness requirements, such as 485HV (ISO 18262), and polished.

b. Special scraper. Shape and size are specified by specific methods and are generally not universal. The material is usually steel and the surface is heat treated to a certain hardness and polished.

c. Trombone. No. 1, size about 32mm × 7mm