The TABER V-5 Stiffness Tester

The stiffness and resilience characteristics of materials up to 10,000 Taber Stiffness Units can be assessed with the TABER^® V-5 Stiffness Tester, Models 150-B, 150-E, or 150-T. This high-precision device offers precise test measurements for specimens with thicknesses ranging from 0.004” to 0.297” to within ±1.0 %. Materials consist of various sheet materials such as felts, wire, tubing, rubber, plastics, metals, textiles, and paper.

Description

The TABER V-5 Stiffness Tester includes a bidirectional pendulum weighing device. This technology is essential for determining a material's stiffness or resilience since it offers a precise and responsive way to measure tiny load increments. Testing is possible in nine categories, from highly rigid (such as plastics) to very lightweight and flexible (such as cellophane or thin metallic foils).

Image Credit: Taber Industries

Specimens are mounted on the Taber V-5 Stiffness Tester using a clamping system for test ranges 2 through 9. When they are on the pendulum, the lower faces of the specimen clamp jaws are precisely in the center of rotation.

This assures consistent test duration and deflection angle, resulting in precise and reproducible findings. Both jaws of the specimen clamp are adjustable, allowing the test specimen to be precisely positioned in the center regardless of material thickness. Two rollers apply force on the specimen’s lower end. The rollers, connected to a driving disc placed directly behind the pendulum, press against the test specimen, deflecting it from its upright position.

The specimen deflects farther from its initial position as the pendulum exerts increasing force on it. The test point reading is obtained when the pendulum mark lines up with the proper drive disc mark (7 1/2° or 15°). This indicates the dial point’s stiffness reading.

The range in which the test is being administered and the scaling factor to be applied will determine the final reading. The equipment outputs the moment stress applied to the test specimen in TABER Stiffness Units (g cm).

Range weights can be added to the pendulum to test materials with various stiffness characteristics. A compensator range weight is fixed to the pendulum's top for materials that weigh incredibly little. The pendulum must have range weights of 500, 1000, and 2000 “Taber Units” fixed to the bottom for stronger materials. For test ranges 7, 8, and 9, a range weight set of 3000 and 5000 Taber units is optional.

When testing extremely light and flexible materials using Taber’s optional Sensitivity Range Attachment (also called SR or High Sensitivity Attachment), which has a Taber Stiffness Unit value between 0 and 1, Range 1 is utilized.

Cellophane, synthetic and natural fibers, tissue paper, metallic foils, films, etc. are a few examples. The attachment's two components are the Driven Pins Holder, which is fastened between the clamp jaws, and the Driving Pins Holder, which is fixed to the studs in lieu of the left—and right-hand rollers.

Customers have widely used the Taber V-5 Stiffness Tester to assess the stiffness properties of wires and cables. The tester now includes a “v-notch” in the clamps to enable this testing. The recommended samples are carefully centered in the notch, measuring between 3 and 8 mm in diameter and 70 mm in length, to avoid pinching or crimping the sample.

It is advised to secure wire and cable samples with a diameter of less than 3 mm at a spot inside the clamp’s flat area. Samples with curvature should be avoided as they may interfere with the stiffness tester's ability to operate properly and set up. Test findings have to be utilized just for comparison, i.e., comparing materials, lots, etc.

Video Credit: Taber Industries

Models

TABER Stiffness Tester - Model 150-T (115/230 V, 50/60 Hz) – The Stiffness Tester Model 150-T has an LCD operator touchscreen interface with many display settings. Test results are immediately translated to the user-selected stiffness range and shown graphically on the interface.

Results are presented in Taber Stiffness Units or Millinewton Meters, and data can be simply saved or transmitted to a computer. This instrument, like the type 150-E, calculates the average, standard deviation, and high/low values. Additionally, operators can operate in manual mode and choose the direction, deflection, and amount of deflection cycles.

TABER Stiffness Tester - Model 150-E (115/230 V, 50/60 Hz) - The Stiffness Tester Model 150-E has an on-board computer that automatically calculates and records stiffness testing results. Stiffness readings are automatically translated to the user-specified stiffness range, removing the need to manually multiply data by a scaling factor. This device also computes the average, standard deviation, and high/low values. Operators can pick the direction, deflection, and number of cycles using the 16-button keypad. In addition, the instrument, like the Model 150-B, can be operated manually.

Data from the Model 150-E Stiffness Tester can be printed or transferred to a PC via the accessory connections. Up to 1,000 measurements can be kept in non-volatile memory. In addition to the inbuilt real-time clock and calendar, saved readings can be tagged with an optional user-defined label. An optional RS232 Serial to USB Adapter Cable is recommended for downloading data.

TABER Stiffness Tester - Model 150-B (110 V, 60 Hz) – The Model 150-B is a manually controlled device that is modeled after the original Taber V-5 Stiffness Tester. The Model 150-B is lightweight and portable, with telescopic tripod legs. Electronic components are housed in a robust enclosure. The model 150-B requires the user to manually record stiffness testing data, average the findings, and multiply by a scaling factor.

Evaluation

The average reading is calculated following a 15° (or 7 1/2°) deflection of the test material to the left and right. The number designated in the Set-Up Chart for that specific range is multiplied by this. The material’s stiffness value, expressed in Taber Stiffness Units, is the product.

Taber Stiffness Units are defined as the bending moment of 1/5 of a gram given to a 1 1/2" broad specimen at a 5-centimeter test length and flexed to a 15° angle. A stiffness unit is comparable to one gram centimeter.

E = 0.006832 • (1/(w • d³ • θ)) • S_T

Where E = Stiffness in flexure in pounds per square inch

w = specimen width in inches

D = specimen thickness in inches

θ = deflection of specimen converted to radians (15° = 0.2618 radians, 7.5° = 0.1309 radians)

S_T = Taber Stiffness Units

Resilience is a material’s elastic quality that can be quantified using the following formula, which finds the ratio of basic stiffness to initial stiffness:

 % of Resilience = (Basic Stiffness • 100) / Initial Stiffness

Initial stiffness is the initial reading acquired immediately after stretching the specimen to the end point of deflection (usually 15°), and it is commonly used to compare relative stiffness characteristics.

Basic stiffness refers to the loss of stiffness induced by "elastic fatigue," or the realignment of molecules that occurs when a specimen is kept at the endpoint of deflection.

TAPPI Test Method T543 explains how to convert Taber Stiffness Units to Genuine Gurley™ Stiffness Units using the equation below. The correlation test investigations between Taber and Gurley stiffness values ranged from 20 to 150 g cm on Taber.

S_T = 0.01419S_G - 0.935

Where S_T = Taber Stiffness Units

S_G = Gurley Stiffness Units

To convert Taber Stiffness Units to Millinewton-Meters, use the following equation:

"X" mN-m = S_T • 0.098067

Where S_T = Taber Stiffness Units

To convert Taber Stiffness Units to Pound-Inch, use the following equation:

"X" lb-in = S_T • 0.000868

Where S_T = Taber Stiffness Units

The Taber V-5 Stiffness Tester’s exceptional sensitivity accentuates material variances. As a result, it is advised that 5 or more samples be evaluated, with the average result used to determine stiffness. Variations in testing could be caused by how the specimen is clamped or how the clearances between the rollers and specimen are changed. It is crucial to note:

• Do not flex a sample before testing
• Take care not to crush the sample by overtightening the clamps
• Excessive compression of the sample reduces the material’s thickness, resulting in inconsistent and erroneous stiffness values due to a lower cross-sectional area at the clamp

Some materials have an intrinsic grain that stems from their production process. This often affects stiffness and must be factored into test processes by examining materials in both directions. It is best to prepare and test 5 to 10 specimens in each grain orientation for testing.

Test Methods

The Taber V5 Stiffness Tester satisfies test methods including Tappi T 489, Tappi T 566, ISO 2493, and JIS P 8125. Additional accessories might be required.

The table below serves as a guide while setting up the instrument to identify the test range for the evaluated material.

Source: Taber Industries

*Auxiliary Range Weight Set (range 3000 - 5000 Taber Units) is sold separately and required for ranges 7 - 9.