ASTM D4812

Introducing ASTM D4812 - Industrial Physics  

ASTM D4812 is a global ASTM pendulum-impact testing method for measuring the impact resistance of unnotched plastic cantilever beams.  

A pendulum-impact test will tell you how much energy you need to break a test specimen of specified size under stipulated conditions.  

The ASTM D4812 impact test method determines a plastic’s resistance to breakage by flexural shock. It does this by measuring the energy extracted from the single swing of a pendulum-type hammer as it strikes and breaks the test specimen. Otherwise known as the pendulum velocity. 

Pendulum-impact test machines are standardized to comply with certain requirements. This includes a fixed height of hammer fall that ensures the same velocity of the hammer at the moment of the impact test.  

ASTM D4812 advises on using pendulums of different initial energies and weights for specimens of different impact strengths. Manufacturers of pendulum-impact testing equipment are permitted to use different lengths and constructions of pendulums with possible differences in pendulum rigidities.  

The result of this impact testing method is reported as energy absorbed per unit of specimen width. 

Breaking down the breaking test  

The ASTM D4812 test method deals with three categories of failure to assist with your impact testing:  

• Complete break: the specimen is broken into two or more pieces 
• Partial break: an incomplete break that has fractured at least 90% of the specimen’s depth 
• Non-break: an incomplete break where the fracture extends less than 90% of the specimen’s depth. 

If a plastic sample shows more than one type of failure after the pendulum-impact test then the report will indicate the average impact value for each type of failure. 

The value of the ASTM D4812 impact test lies mainly in the areas of quality control and materials specification. The fact that a material shows twice the energy absorption of another under these test conditions doesn’t indicate that this same relationship will exist under another set of test conditions. Under different conditions you may even find that your ranking of materials could change. 

ASTM D4812 results

The energy lost by the pendulum as the specimen breaks represents the sum of the energies required to produce the following results: 

• To initiate fracture of the specimen 
• To propagate the fracture across the specimen 
• To throw the free end (or pieces) of the broken specimen (toss correction) 

• To bend the specimen 
• To produce vibration in the pendulum arm 
• To produce vibration or horizontal movement of the machine frame or base 
• To overcome friction in the pendulum bearing and in the indicating mechanism, and to overcome windage (pendulum air drag) 
• To indent or deform plastically the specimen at the line of impact 
• To overcome the friction caused by the rubbing of the striking nose (or other part of the pendulum) over the face of the bent specimen 

ASTM D4812 testing insight

The frame and base of the pendulum-impact testing machine should be sufficiently rigid and strong enough to handle the energies of tough specimens without motion or excessive vibration. The arm of the pendulum-impact testing device itself can’t be made very massive because the greater part of its mass must be concentrated near its center of percussion at the striking nose.  

Locating the striking nose precisely at the center of percussion reduces vibration in the pendulum arm when working with brittle specimens. But even so, if you have a tough specimen then you’re likely to lose some energy through pendulum-arm vibration, even when the striking nose is properly positioned. The actual amount varies depending on the pendulum design. In a well-designed pendulum-impact testing machine of sufficient rigidity and mass the losses should be small.  

ASTM D4812 testing equipment  

So, how can Industrial Physics improve your ASTM D4812 testing?  

We can support all types of impact testing, from pendulum impact, falling dart and falling weight impact testing through to low temperature brittleness testing. 

Need a clear vision of how well your samples will fare during manufacture, storage and transportation? An IP pendulum-impact tester simulates the real world challenges that your products will face. 

Advanced pendulum impact testing system 

The Ray-Ran advanced pendulum impact testing system uses microprocessor technology to determine the energy required to break or rupture plastic or ceramic specimens, composites and nonferrous metals. It’s just what you need for testing to ASTM D4812 standards.  

It’s just the job for Izod, Charpy or tension impact testing. It’s perfect for pipe and puncture  impact testing. Plus you can use it for small diameter pipe testing and component impact and puncture tests.  

Need ASTM testing solutions? Get in touch

So, what’s impacting upon your product performance? We’ll help you to strike at the heart of the matter and get the best from any impact test. Just get in touch today!  

Contact us - Industrial Physics 

Your global test and inspection partner for ASTM D4812