Dart Impact Tester: Working Principle, Test Procedure, & Standards

Evaluating a material's ability to withstand sudden impacts or shocks is crucial in industries such as automotive, construction, and manufacturing. Engineers and quality control specialists often encounter the challenge of determining whether a material can endure real stress without breaking. Standard strength tests typically do not accurately simulate dynamic loading conditions. 

This is where a dart impact tester is used, providing a precise solution to the problem by mimicking rapid impact forces and assessing a material's toughness. This equipment, through standard procedures, ensures that materials comply with safety and performance standards, ultimately minimizing structural failure risk. In this article, we will learn everything about the dart impact tester, its testing procedures, and other important related concepts.

What is Dart Impact Tester?

Dart Impact Tester measures the impact resistance of materials, such as plastic films, by determining the energy transferred to the material by a free-falling dart before a fracture or puncture occurs. It simulates real-life conditions in which a material is impacted, like when being shipped or handled.

This test is performed by free-falling a dart-shaped projectile from a specified height onto a test specimen, typically a sheet or a film of the material being tested. The dart is free-falling from a specified height and strikes the specimen at a controlled velocity. The force or energy required to puncture or fail the material is then determined, which provides very valuable information relating to its impact resistance properties.

How Dart Impact Tester Works?

A Dart Impact Tester is an apparatus that is specifically used to find out the impact strength or toughness of plastic sheets, films, and other materials. It simulates the impact of a falling object on a material to test if the material is resistant to the impact without rupturing. The test is most useful in packaging, plastic manufacturing, and quality control sectors.

Step-by-Step Test Procedure for Dart Impact:

• Step 1: Sample Preparation: A plastic sheet or film is cut to a specified size and conditioned (when necessary) to proper specifications.
• Step 2: Mounting the Sample: The sample is held firmly in a circular clamp over the bottom opening.
• Step 3: Dart Setup and Choice: Depending on the test procedure (Method A or B), an appropriate dart size and initial weight are chosen:

1. Method A: 38 mm diameter dart dropped 660 mm.
2. Method B: 50 mm diameter dart released from 1524 mm.

• Step 4: Releasing the Dart: The dart is released from the specified height to freely fall onto the center of the clamped specimen.
• Step 5: Observation of Failure: The sample is tested to determine whether it has burst. Based on the outcome, the dart weight is added to or subtracted from in the subsequent iteration.
• Step 6: Calculation of Impact Resistance: With the aid of statistical methods (e.g., the staircase method), we derive the mean failure weight (g). This is used to calculate the energy (Joules) consumption of the sample.

Dart Impact Tester Working Principle

The Dart Impact Tester works on a free-fall impact principle, and a hemispherical dart (or projectile) drops from a specific height onto a horizontally clamped test specimen. Impact strength of the material is characterized by the energy at which the material fails (breaks or punctures).

Main Components of Dart Impact Tester

• Dart (Projectile): A steel dart of a given weight and diameter with a hemispherical tip.

• Clamping Unit: Closely presses the sheet or film to prevent slipping during the test.

• Drop Mechanism: A regulated mechanism that releases the dart from a height previously established.

• Base Platform: Supports the specimen and records the impact.

• Weight Sets: Additional weights to be added to the dart weight if desired.

• Detection System (Optional): Sophisticated versions have sensors that automatically detect penetration or failure.

What is Dart Impact Test Procedure for Plastic? 

The Dart Impact Test for plastic films is all about checking how tough and sturdy they are. It works by seeing how much energy it takes to break the film when a weighted dart falls on it. Here’s how the test goes:

Preparing the Sample:

• You get the sample ready based on certain standards, like ASTM D1709-15a, ASTM D3029-82a, or IS 2508 – 1984. 
• It’s clamped down using a circular device to keep it from moving during the test.

Setting Up the Test:

• The dart impact tester needs to be set up and adjusted to match the test standard. 
• You decide the dropping height of the dart – it can be either 660mm or 1524mm. 
• Sometimes, a vacuum pump is used to hold the sample in place.

Running the Test:

• The dart is dropped from the chosen height onto the sample. 
• This is done several times, and a digital counter tracks the number of trials.

Analyzing Results:

• After the test, you look at the results to find out the impact failure weight – that's the weight that makes half of the samples fail. 
• You can figure out how resistant the plastic film is based on the energy it absorbs during the impact.

 

Things That Affect Results

• The weight and shape of the dart
• The height from which the dart drops
• How the sample is clamped and the pressure used
• The type of plastic film being tested
• The conditions under which the test happens

Common Standards of Dart Impact Tester

Dart Impact Testers follow all industrial standards that help test how well plastic films and sheets resist impacts. These standards keep things consistent and reliable, so everyone gets the same kind of results. Here are the most common standards you might run into:

1. ISO 7765-1

• Full Name: Plastics — Determination of Impact Resistance by the Free-Falling Dart Method — Part 1: Staircase Methods
• Published by: International Organization for Standardization (ISO)

Key Features:

• Similar to ASTM D1709 but internationally harmonized
• Uses the staircase method to calculate the average failure energy
• Preferred in European and Asian countries

2. IS 2508 (India)

• Full Name: Specification for Polyethylene Films and Sheets
• Published by: Bureau of Indian Standards (BIS)

Key Features:

• Refers to the dart impact as one of the mechanical tests
• Often used for regulatory compliance in Indian plastic manufacturing

3. JIS K7124 (Japan)

• Full Name: Testing Methods for Impact Resistance of Plastic Film and Sheet
   
• Published by: Japanese Industrial Standards (JIS)

Key Features:

• Specifies the dart drop method and test conditions
• Similar to ASTM and ISO with local modifications

Conclusion 

The Dart Impact Tester is an important tool for checking how well plastic films and sheets can handle impacts, especially in packaging and quality checks. It works by dropping a weighted dart from a set height to see how tough the material is. 

Following standard guidelines, like ASTM D1709 and ISO 7765-1, helps make sure the results are reliable and can be repeated. Knowing how this tester works, as well as the testing steps and the relevant standards, can help manufacturers make better products, lower the chances of material failures, and meet global quality standards.

Presto Instruments is a leading dart impact tester manufacturer in Sri Lanka, committed to global quality standards. Our equipment is designed to improve product reliability, reduce defects, and ensure consistent performance. Trusted by industries worldwide, we offer reliable and customized solutions to meet your testing needs. Contact us today.