How Tensile Testing Device Works?

Tensile testing device SCOPE

The test method describes methods for determination of strength of attachment of press-studs (poppers), jeans buttons, rivets and snap fasteners to garments.

PRINCIPLE

A sample is taken from the garment, consisting of a sandwich of several fabric layers, through which a press-stud (popper) has been applied. This is subjected to a known load, applied in such a way that the two halves of the press-stud component are pulled in opposing directions, thus tending to prise the two halves apart. Male and female halves of the press-stud are tested separately.

APPARATUS

Tensile testing device of the constant rate of elongation type, capable of determining the applied load to +/- 5% accuracy at a rate of traverse 50+ mm/minute.

Preparation of test specimens and materials (removal from the garment): Cut a parallel strip of fabric from the garment that contains a single male or female press-stud so that the press stud component is positioned centrally on a fabric strip approximately 30mm wide by 150mm long.

TEST PROCEDURE

• Condition for a minimum of 4 hours at 65+/- 2%rh and a temperature of 20+/- 2  degrees
• Testing must take place in a conditioned environment.
• Grip the specimen in the jaws of the tensile test device. Determine the force to remove the press stud component.
• Test a minimum of ten male and ten female components.

REPORT

• Report the average press-stud removal force (in Newtons) for the 10 male        components separate from the 10 female components.
• Report the minimum press-stud removal force (in Newtons) for the male and female components separately.
• Report if the fabric has broken down and if so at what force, even if the press-stud has not been removed.

Incomplete Heat-Setting-

Definition and Causes

• With synthetic knit and woven fabrics and with fabrics containing Spandex yarns, a complete Thermo-fixing process must take place.
• This is done to ensure that after finishing a dimensionally stable fabric is produced and prevents the fabric to exhibit wrinkles and edge curling.
• This is normally done by exposing the surface of the fabric to temperatures of 360-380 degrees Fahrenheit for a certain period of time (dwell time).
• This dwell time will be dependant on type of fabric, percentage of the Spandex yarn and the size of the heating chambers.
• In certain cases in order to prevent heat damage a small quantity of wetting/penetrant type of chemicals need to be added in the Pad tank.

Preventive Suggestions

All technical aspects of the heat-setting process must be examined and appropriate steps need to be taken.

Corrective Measures:A refinishing at a higher than the original temperature will be required.

Excessive Over-Feed and Under-Feed-

Definition and Causes

• During the drying process the control and stabilizing fabric’s weight (Yield) is an important function.
• This is, normally, done by devices known as Over-feed (or under-feed) rollers and wheels.
• In knit fabrics to increase the weight, these devices are made to increase the density of the knitted courses across the width of the fabric in a uniform and precise way.
• This is referred to as Over-feeding and its excessive use will cause severe crease lines on the selvedge of the fabric on both sides.
• To decrease the weight, a reverse action takes place. Excessive use of this Under-feed action will cause the fabrics to develop severe creases, particularly, in the middle portion.
• These problems do not appear in woven fabrics.

Preventive Suggestions:A correct and precise method of finishing, based on the type of fabric must be used.

Corrective Measures:With cotton fabrics, a refinishing at a correct measure of under-feed or over-feed will correct the problem.

Conclusion

With synthetic fabrics, a rewashing of the fabric at pressurized conditions and at high temperatures will be necessary for Tensile Testing Device