Posted by Richard Gedney on Thu, Mar 18, 2010 @ 12:34 PM
ADMET offers electromechanical and servo-hydraulic fatigue testing systems for tension, compression, torsion and biaxial testing applications. All systems are engineered to meet your needs (The eXpert 81T 30Nm Torsion Fatigue Tester shown in the video is for medical device testing.).
ADMET equips each fatigue tester with a high-speed closed-loop multi-channel controller called MTESTQuattro(R) Dynamic. MTESTQuattro(R) will produce sine, square and triangular waveforms based on force, displacement, torque or angle amplitude control. Users can manually adjust control gains and end point values on the fly or activate amplitude control so that the controller automatically adjusts the end point values to ensure waveform amplitudes stay within tolerance. Biaxial systems employ two axis of control which can be programmed to operate independently or in unison.
Posted by Debbi Cohen on Thu, Mar 18, 2010 @ 08:51 AM
A suture is a medical device that doctors use to hold skin, internal organs, blood vessels and all other tissues of the human body together, after they have been severed by injury or surgery. They must be strong enough to hold the tissue and flexible enough to be able to tie into knots easily.
Suture tensile strength determines where the suture can be used inside or outside of the body and for how long it is intended to remain. Sutures are absorbable or non-absorbable and in some cases, have needles attached.
Below we describe a typical suture tensile test and what type of equipment is needed to perform this test.
Types of Suture tests
1)Standard tensile pull test.
2)Knot pull tensile test- the knot is centered in between the grips.
3)Creep test- Pull to a desired load and hold.
Procedure for straight pull
1)Insert non-absorbable suture sample into pneumatic cord and yarn grips. The guage length is usually 10 inches from grip to grip with a 2.5 inch grip separation.It is very important that the sample
is lined up properly or it will impact the results of the test.
2) Set profile to pull suture at desire speed to a desired load or until the sample breaks. We used 12 in/min.
3)After sample breaks, the test stops.
Results
From the data we can tell the tensile strength and peak load of nonabsorbable suture.
In other tests, we can tell the strength of a suture with and without a knot pull, and the strength of absorbable or non-absorbable sutures. In addition, you can perform creep tests and cyclic tests.
Reports can be customized using MTESTQuattro from
ADMET.
Suture sizes are defined by the United States Pharmacopeia (U.S.P.) Atraumatic needles are manufactured in all shapes for most sizes. The actual diameter of thread for a given U.S.P. size differs depending on the suture material class.
Many textile ASTM methods are used for thread testing.
Posted by Andrew DeWolfe on Mon, Mar 15, 2010 @ 02:43 PM
ASTM D1414 (D 1414) covers multiple properties of O-Rings. Part of the specification includes tension testing for determining the breaking force, tensile strength, and ultimate elongation of an o-ring. The tension test is intended to be performed on a universal testing machine (tensile testing machine). If you are going to perform this test, you should read the entire specification from ASTM. This is a quick summary to decide if this test is right for you, and to point out what equipment you need to perform the test.
Here is a short video of the test:
Test Procedure:
1. Lubricate the grip spools with oil (not required if doing step # 4)
2. Load the o-ring on both the upper and lower spools
3. Begin the test by separating the grips at a speed of 20 inches per minute
4. Rotate one spool one revolution per six inches of travel (not required if doing step # 1)
5. End the test after sample break (rupture)
Analysis obtained:
1. Breaking Force
2. Tensile Strength
3. Ultimate Elongation
Equipment required:
1. Universal testing machine (tensile testing machine) with these minimum specifications: (similar to those in ASTM D412)
A. Servo-controlled to keep a constant rate of speed during the test (+/- 2 inches/min)
B. At least 30 inches of crosshead travel or more for high elongation materials
C. Most small and common 1kN (225 pound) load capacity machines will work for the loads of the materials tested to this specification
D. All of our eXpert 2600 series dual column machines meet these requirements, and it is also common to use our single column eXpert 7601 XL with 53 inches of crosshead travel.
2. ASTM D1414 requires special grips. These grips have interchangeable spools with various diameters for a wide variety of o-rings. The spools rotate freely on a pin extending from the grip. If using the motorized version, the bottom grip and spool is connected to a small variable speed electric motor to enable rotation during the test to minimize stresses. Other more primitive and costly systems have been employed that generate rotation from the upward movement of the crosshead. However, the optional motorized version is easier to use and is usually less expensive.
ADMET Motorized ASTM D1414 O-Ring Fixture
3. If you don't want to use the motorized fixture, the specification allows you to lubricate the spools instead. In this case, you would just use two of the upper grips.
Posted by Andrew DeWolfe on Thu, Feb 25, 2010 @ 01:30 PM
One of the most common specifications that our customers follow is ASTM D882 which is the Standard Test Method for Tensile Properties of Thin Plastic Sheeting. This test is very similar to the common ASTM D638 test whereby plastic material is pulled until in breaks in order to measure elongation, tensile modulus, tensile yield strength, and tensile strength at break. However, it is designed specifically for thin sheeting and film less than 1 mm (0.04") thick.
Read more about the test and find out what equipment is required in one of our other posts. Here is a video of how the ASTM D882 film tensile strength test is performed:
Ask an Engineer a question about your application- click here
Posted by Andrew DeWolfe on Fri, Feb 12, 2010 @ 08:16 AM
To determine the breaking strength, elongation, etc. of threads, yarns, or other single strand textiles, ASTM D2256 is by far the most common specification that is followed. This is a relatively simple tensile test whereby thread is pulled at a constant rate of speed until it breaks. Please see the video below that shows how the test is performed:
1. Load thread into pneumatic or manual rope grips
2. Gage length (length of thread between grips) should be 10"
3. One grip should pull the thread at a servo controlled constant rate of 12" per minute.
Common measurements obtained:
1. Breaking Force (Maximum force)
2. Breaking Tenacity
B=F/T
B = Breaking Tenacity
F = Breaking Force
T = Linear Density in units of tex or denier
3. Elongation
4. Initial Modulus
5. Chord Modulus (Suggested elongation are 0% and 10%)
6. Breaking Toughness (Energy)
Tensile testing machine requirements:
1. Servo controlled constant rate of extension (CRE) tensile testing machine (if you have an ADMET machine, don't worry, all ADMET machines are servo controlled and can do CRE testing)
2. Pneumatic or manual rope grips where the thread is wrapped around a mandrel (circular feature) or a "horn" shape and is then pinched in the grips. This prevents premature thread breakage.
3. Software that can automatically calculate all measurements (we use our MTESTQuattro software).
Tips:
1. Make sure your data acquisition is set high because the test is short as thread breakage happens quickly. We set our machines to 1,000 Hz to take 1,000 load and position measurements every second.
2. Make sure your thread is lined up evenly between the top and bottom grip. Slight errors in alignment can significantly alter the repeatability. By design, our "V" shaped channel pneumatic grips prevent misalignment.
ADMET "Horn" style pneumatic thread / rope grip with "V" channel alignment feature.
Posted by Debbi Cohen on Mon, Feb 08, 2010 @ 11:59 AM
Biaxial - torsion and tension and compression universal testing example. There are many different products that require biaxial testing. Biaxial loading can be used to measure basic material properties and also the behavior of specific features of interest under biaxial loading conditions. For example, a company may want to test a spinal implant maintaining tensile or compressive force or axial displacement constant and increasing the torque or angle of twist. Another company may want to test a intramedullary fixation device by maintaining torque or angle of twist and increasing load or axial displacement. Many ASTM and ISO standards require biaxial testing.
We used a Croc sandal to show an example of biaxial testing. The Croc was secured to the bottom grip. The strap of the Croc was attached to the top vice grip. At 20 in/min we cycled up and down 1 inch while twisting back and forth 45 degrees. We wanted to see how much wear the sandal strap could tolerate before it became stretched and ineffective. Think about the materials that you are testing. Could you use a biaxial testing machine to get more information to your customers about the features of your products? This test was performed using an
ADMET eXpert 2610 5kN dual column system with a 10Nm torque actuator and a triaxial load cell. The system can be configured according to your specifications.
Posted by Debbi Cohen on Sun, Jan 31, 2010 @ 08:19 AM
Many different types of testing profiles can be used to test a syringe. There are ASTM and ISO standards, for example,
ISO7864 and ISO9626, as well as individual company specified testing profiles. You may want to discover how much force it takes the press the plunger with and without liquid, or you may want to determine how easy or difficult the
luer lock is to remove or to connect, or you may want to examine the pressure of the liquid when forced out of the syringe at a high speed, and more. In this example, we filled a syringe with a needle hub attached by luer lock with water. We compressed the plunger through its 1.75 inches of travel. We were interested in measuring the average force required to push the fluid through syringe. To obtain an accurate load average measurement, we needed to ignore the "noise" at the beginning and end of the stroke. We programmed our machine to average the load between 0.5 - 1.5 inches of displacement. This syringe test was performed on an
ADMET eXpert 7601, Single Column, 1kN testing system equipped with an
eP Digital Controller and a syringe testing fixture. This test gave us information on the force required to compress the plunger to a certain position.
The test profile is as follows;
- Preload to .01 lbs
- Compress syringe plunger 1.5 inches
- Measure Average Load and Peak Force
Posted by Andrew DeWolfe on Wed, Jan 27, 2010 @ 02:24 PM
This video shows an example of a Rubber Property Test - Adhesion to Flexible Substrate as specified in ASTM D413 (D 413) & ASTM D378 (D 378)
Requirements for Type A Test - 180 degree peel
1) Sample size: 25mm wide, 150mm long, separate layers enough to fit in grips.
2) Universal testing machine (tension / tensile testing machine) accurate to with +/- 1% of speed and load measurements. We used our eXpert 7601.
3) Tensile grips - hold specimen and prevent slipping during test. This test used vise grips with serrated inserts.
Posted by Andrew DeWolfe on Mon, Jan 25, 2010 @ 02:02 PM
This test measures the force required to close a lid on a travel coffee mug. We used our eXpert 2610 universal testing machine to perform the test, but it would have worked just as well with one of our smaller single column eXpert 7601 or eXpert 5601 testers.
This test is very simple- the compression platen moves down to press the lid onto the coffee mug and measures the peak force required to close the lid. However, the technology required to perform repeatable testing is complex. The closing event happens quickly so you need to record the data very fast. For this test our data collection rate was 1000 Hz, or in other words, we took 1000 load and position measurements every second. The peak load measurement is significantly impacted by the speed of the test. Therefore, a servo controlled testing machine is required to maintain a constant testing speed (in this case 10" per minute). Servo control senses the slow down in speed caused by the load of the test specimen and tells the motor to move faster to keep the speed constant.
This type of test is applicable for a wide range of products. A few examples we have tested that are similar in concept are: automotive center console lids, headphone jacks, and consumer goods packaging.
You can see a video of the test below.
Posted by Andrew DeWolfe on Mon, Jan 11, 2010 @ 08:16 AM
The International Tennis Federation (ITF) developed a specification that is used to determine the forward and return deformation characteristics of a tennis ball. Many conceptually similar tests can be used by companies who do not make tennis balls as this compression test is a good overall quality control check of many products - whether it be a basketball, football, soccer ball, golf ball, dog toy, etc.
To perform the test on a tennis ball, do the following:
1) Compress the ball to a load of 18 pounds
2) Measure the distance the ball had to be compressed to reach a load of 18 pounds (forward deformation)
3) Continue to compress the ball until it has been compressed a total of 1 inch.
4) Uncompress the ball
5) Measure the distance when the ball again reaches 18 pounds (return deformation)
6) Uncompress the ball and note both the forward and return deformation
The video below shows an example of this test being performed on our eXpert 7601 testing machine.
If you have any questions please feel free to visit our website or call us @ (800) 667-3220