The crushed stone impact testing machine is mainly used in the automotive industry to carry out corresponding detection tests on the automotive shell coating.It is a comprehensive evaluation of the mechanical properties of the entire coating system,which can reflect the flexibility,adhesion between layers,and compatibility of the coating.It is also one of the extremely important testing items for evaluating the secondary mechanical properties of the coating.It is one of the important tests for domestic and foreign automotive manufacturers to conduct automotive testing.

　　Testing principle:

　　Make a large number of small,sharp edged steel balls or crushed stones impact the surface of the layer in a short period of time,and conduct the entire experiment at a controllable temperature.After the stone strike is completed,remove the loose coating with tape to expose the remaining stone strike marks on the sample.Analyze the degree of damage to the coating to determine its resistance to stone strikes.

　　At present,the following two major systems of coating stone impact resistance testing and evaluation methods are widely used both domestically and internationally.

　　SAE system

　　The Society of Automotive Engineers(SAE)has developed SAE J400,which is commonly used by automotive companies such as General Motors and Ford in the United States.

　　The anti stone impact method used by Japanese automotive companies is similar to SAE J400"Anti Stone Testing of Automotive Surface Coatings",but there are differences in the specifications,test temperatures,and evaluation methods of stone.Due to the large number of joint ventures with Japanese automobile companies in our country,JIS's shooting method is also quite common.

　　ISO system

　　The ISO 20567-1"Determination of Stone Resistance of Paints and Varnishes-Part 1:Multiple Impact Test"developed by the International Organization for Standardization(ISO)is derived from the German industrial standard DIN 55996-1:2001"Testing of Crushed Stone Impact Strength of Coating Materials-Part 1:Multiple Impact Test".Therefore,in Europe,the German Institute for Standardization The French Standardization Association and the Austrian Standardization Association have both cited this standard to establish their own testing standards.