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A universal testing machine (UTM) can perform a wide variety of tests, applying tensile and compression forces and measuring the load-displacement response of the test specimen. A critical element of the complete system is its versatile software, used to program the testing procedure. This software allows precise control of the machine, enabling quality control methods to be implemented across all industries.

Here, we provide an overview of some universal tester applications, demonstrating the diversity of test samples, loading variations and industry sectors where this common principle meets unique requirements.

Raw materials for final products

Documenting material properties is often a key factor in quality control and R&D divisions. Materials testing is a well-established technique to determine the physical attributes of any ‘raw’ material from metals, plastics and composites to rubber and even wood.

A material’s mechanical properties are characteristics related to its elastic and inelastic responses at an internal, atomic level under applied force and are derived from its stress-strain relationship. The test standards against which these calculations are compared are therefore hard facts derived from the pure laws of physics. In one of the most important materials test methods, a universal tester in tensile mode grips a standard-shaped ‘dumbbell’ specimen and pulls until a relevant event occurs—the material ‘yielding’ or fracturing—signifying the end of the required measurement range.

Metal materials high tension test
A high-capacity twin-column UTM performing a material properties analysis on a metal test piece. Large grips are required to keep the specimen secure under high tensile loads and an extensometer is essential instrumentation to accurately record these low values of elongation. The software screen displays a typical stress-strain curve of an elastic material under tension; showing the characteristic shape we use to calculate fundamental material properties, such as Young’s modulus of elasticity, from salient points on this curve. Image courtesy of Mecmesin, a PPT Group company

Cooked materials for fresh produce

Food science has many parallels with manufacturing materials theory as the behavior of the test specimen is determined by the qualities of its inner structure. Whilst we check the physical properties of raw engineering materials most often to ensure failure does not occur in real-world situations, the way a foodstuff breaks down is what we want to guarantee and control in this case.

The primary instrument for measurement of the physical properties of food is termed a ‘texture analyzer’, but behind this sector-specific branding is a universal tester. Hardware fixtures and appropriate software programs again force deformation of the sample, and the measured results determine attributes which correlate to established sensory qualities.

The test standards here are generally much more subjective—a matter of taste. However, the sensory attributes of taste (and smell) are not physical attributes and therefore are not measured with a universal testing machine. The terms ‘soft’, ‘crisp’, ‘tender’, ‘chewy’ and others are commonly used to describe the ‘mouthfeel’ of food. The measured values from a texture test are usually assigned as pass/fail based on the expert opinion of a human panel within the company itself. Certain food sectors do have exact values expected from texture tests as a means of consistently grading food produce. Meat tenderness is calculated with industry-standard blades to perform a shear force test, and thickening gels (gelatin, hydrocolloids) have their firmness, termed ‘Bloom strength’, measured for informative labelling of the raw product’s concentration recommendations.

Food processors use this texture analysis strategy to optimize their ingredients and formulation practices and provide preparation instructions for end-consumers. The associated packaging manufacturers benefit from studies of how the texture changes over time whilst within the packaging—shelf life.

Bread freshness compression white slice test slicing samples software and OmniTest.
The ideal texture for fresh bread is a level of softness. The consumer perceives freshness from the ease of compression—in the mouth whilst biting and chewing or with the hand when preparing something like a sandwich. A universal tester fitted with a compression probe is used to depress the bread and the resulting curve shape informs the food scientist that the texture meets the required standard. Peak forces and areas below the graph simultaneously provide a broad texture profile to further differentiate between test batches. This TPA test replicates two ‘chew’ cycles by compressing twice. Image courtesy of Mecmesin, a PPT Group company

As many cosmetics products are used on the skin, quantifying their finger feel is also achieved by universal tester measurements. The efficiency with which a semi-solid product, such as a crème or lotion, flows from its packaging dispenser or through its production channels—filler-line nozzles, for example— is also greatly influenced by its physical texture.

The Food and Drug Administration (FDA) is responsible for assuring the safety, efficacy, and security of certain products including food and cosmetics. Section 21 of the Code of Federal Regulations (CFR) Part 11 relates to guidelines for using electronic records and signatures, therefore software which facilitates this compliance is a necessary feature of any universal testing system used in these sectors.

Manufactured products for functional performance

Finished products by necessity undergo quality assurance testing as a final check that performance and legislative targets are being met. We have seen an example of a high-loading industrial application of a universal tester for metallic raw materials, but such is the drive for quality in the commercial world, that this equipment is a smart investment in any manufacturing business. The cosmetics and personal care segment is fiercely competitive and customer loyalty is a strong factor in a brand’s success. Products are expected to work (and be packaged) beautifully yet be durable in daily use.

Cosmetics thick applicator brush tuft pull out OmniTest.
A cosmetics brush manufacturer takes advantage of the versatility of a universal tester to quality-check the retention integrity of the bristles. Offering a range of brushes for different cosmetic product applications, the use of bespoke fixtures to consistently locate each brush design geometry to be aligned with the bristle tuft upper grip. This flexibility of one aspect of the system enables the same ferrule and adhesive integrity test method to be implemented for the entire product offering. Image courtesy of Mecmesin, a PPT Group company

Wrap up

The strength and beauty of universal testers lies in their flexibility in both performing quality assurance testing and futureproofing themselves. An initial outlay for the hardware gains the core of the testing system as the addition of specialist fixtures and software program development continue to add value and stay abreast of evolving external quality drivers.