What Is an Impact Printer?
Impact test is generally a test method to determine the safety, reliability and effectiveness of products for military and civilian equipment when they are subject to impact or action by external forces.
Impact test
- Shock tests are divided into three types: 1. Prescribed pulse test methods using sine waves for testing; 2. Shock spectrum test methods; 3. Prescribed test machine test methods.
- According to the temperature, the impact test is divided into:
- Shock test at room temperature. The test is carried out at room temperature, usually in the range of 23 ± 5 .
- Low-temperature impact test; keep it in a low-temperature medium for a certain period of time, and quickly remove it after the temperature reaches the requirements to complete the impact test.
- 1. The medium can be ice-water mixture (0 degrees Celsius)
- 2. Other temperature can use low temperature tank, according to different temperature, you can choose alcohol or liquid nitrogen to keep the sample warm.
- Impact testing machines (pendulum and drop hammer): manual impact testing machines,
- 1. Impact energy
- 1 host, 2 pendulums, 1 protective fence, 1 centering plate for each, special purpose
- GB / T 2423.5-1995 Environmental testing for electric and electronic products. Part 2: Test methods Test Ea and guidelines: Impact;
- GJB150.5-86;
- IEC 60068-2-27: 2008 Basic Environmental Test Procedures Part 2: Test Methods Test Ea and Guidelines: Impact
- GJB150.18-86 impact test
- GB / T229-2007 Charpy pendulum impact test method for metallic materials
- There are different standards according to different fields. For example, the implementation standard of Seating Tester is BIFMA X5.1 2011 08; BIFMA X5.1 2011 11.3; EN 1730: 2000 6.6; ENV 581-2: 2000 6.2.2.3; EN 1728: 2001 6.15; impact tests are mentioned.
- As of 2013, few laboratories can conduct impact tests.
- A kind of dynamic mechanical performance test, mainly used to determine the work consumed by breaking a certain shape of a sample, also known as impact toughness test.
- According to the sample shape and breaking mode, the impact test is divided into three types: bending impact test, torsional impact test and tensile impact test. The beam bending impact test method is simple to operate and has the widest application. Its test principle is shown in Figure 1.
- Impact test
- The work consumed by the impact sample is called the impact work Ak. Divide A k by the cross-sectional area F at the notch to obtain the impact toughness ak in J / cm2. The ak value has no clear physical meaning because the impact energy is not consumed uniformly along the cross-sectional area of the notch. Therefore, the ak value cannot be used directly in design calculations. The same metal material, the sharper and deeper the notch, the smaller the plastic deformation volume, the smaller the absorption work, and the lower the toughness of the material. Therefore, for samples of different sizes and notches, the results obtained cannot be converted and compared with each other.
- The flexural impact test was proposed by G. Charpy in the early 20th century and has been widely used since. It is mainly used in engineering to evaluate the quality of metallurgical and processing technology, and to measure the toughness-brittleness transition temperature. If the fatigue cracks are prefabricated on the sample, the load-time curve and load-displacement curve can be obtained by using oscillograms or other methods. The fracture toughness K Id at which dynamic cracking occurs and the fracture toughness at which the crack has stopped growing can also be measured. K IA et al. (See Strengthening of metals).
- Toughness-brittleness transition is a phenomenon in which the transition of a metallic material from a ductile state to a brittle state causes a sharp decrease in impact toughness as the temperature decreases. The relationship between the typical impact energy and temperature of metal materials is shown in Figure 3. From the perspective of toughness, the most important thing is to know the toughness-brittleness transition temperature T k (° C). T k is usually obtained from the relationship between impact energy (or impact toughness), fracture topography, deformation characteristics, and temperature. The method is: Select the temperature corresponding to a certain impact energy as T k; If Charpy V-notch sample is used, the T k corresponding to the impact energy of 15 foot-pounds (20.34J) is represented by V15TT; Or use the temperature when the 50% crystalline fracture on the fracture area is Tk , expressed as 50% FATT; and the temperature at which the impact work curve starts to rise to define Tk , which is the zero plastic transition temperature, expressed as NDT. Obviously, Tk varies with different selection criteria. When using Tk , we must pay attention to the definition of Tk .
- Other tests: The traditional flexural impact specimens are too small to reflect the stress state in the actual component, so they cannot meet special requirements. Since the 1950s, methods such as the drop weight test and the dynamic tear test have been proposed. In fact, they are all flexural impact tests using large Charpy specimens. The drop weight test (DWT) is mainly used to determine the NDT of metal steel plates. The thickness of the sample is the same as the actual thickness and the width is increased. The dynamic tear test (DT) is used to determine the dynamic tear work and NDT.
- According to the NDT obtained from the drop weight test and the dynamic tear test, a fracture analysis chart (FAD) can be established to characterize the relationship between stress, defects and operating temperature.