Tensile Pull Test

As pointed out by Milewski (1993), the tensile test methods can be subdivided into (i) tests in which the coatings are being pulled off from the substrate with the help of a counter fixture glued or soldered to the coating and (ii) tests in which the coatings are pulled off from an appropriately formed auxiliary fixture without an adhesive (Ollard-Sharivker test). 

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The data in Table 2.9 represents a composite list of pertinent thermal and viscoelastic properties for barrier dressing materials, and the following observations can be drawn these data. The tensile (pull) testing results of barrier dressing are listed in Table 2.10. 

Modulus of rupture (MOR) n. During a stress versus strain test, tensile pull test, of a material a stress (force or load) is approached where the material ruptures, breaks and separates which is sometimes referred to as the modulus (stress/strain) at rupture. Also referred to as the ultimate tensile strength and force at break... 

FIG. 14 Printed circuit board JR-01 used for thermomechanical fatigue testing utilizing the thermal cycling conditions from -40 to 125°C, with 30-min dwell times at the temperature extremes. Testing also included a shear test for chip components, and a tensile pull test for QFP leads. 

One of the simplest and most useful tests performed on reflow-attached flip chips to determine the adequacy of the solder joints (i.e., C4) is a tensile pull test (Fig. 31). This is done by adhesively attaching a metal stud to the back of a joined chip and pulling the joints in tension at a slow strain rate (approximately 1.0x10 sec ). The pull force is measured during the test using an appropriate load cell. The pull strength is a useful parameter, but the failure mode is a very important indicator of joint quahty. Planar failure at the solder joint interfaces is indicative of a weak and unacceptable interface condition. 

Fig. 21 is a plot that depicts the relative strengths of several features of a solder joint. In a properly fabricated joint, the intermetallic compounds are very strong and deform elastically, but should never fracture. In a tensile test, a properly formed high Pb/Sn solder joint always fails within the bulk solder which implies that the strengths of the interfaces depicted in Fig. 25 are greater than the strength of the solder. Note that the stress-strain behavior of only one interface is shown in Fig. 26. Although each interface shown in Fig. 25 exhibits a different stress-strain behavior, each must possess a tensile strength greater than the solder. If an interface in the structure is weaker than the solder, it will result in a brittle, planar failure in a tensile pull test. A change in fracture mode from plastic solder fracture to brittle elastic interface fracture is usually an indication that a terminal is defective. Lead-rich solders are usually weaker and more ductile than tin-based solders (Fig. 26).

Some modifications of the standard tensile pull test may be required for lead-free solders with high-Sn contents which are typically stronger than high Pb-Sn solders causing failures in the chip insulator or chip carrier. This can confuse data interpretation but is not necessarily a concern if the pull strength is adequate, and no joint interfaces fail. 

Although the USP defines the knot-pull tensile strength test in terms of a surgeon s knot, most surgeons use a variety of other knots depending on... 

The tensile strength test [Figure 3.1 (1)] (ASTM-638) employs samples of a specified shape, typically a dogbone, as depicted in Figure 3.2. The sample is clamped at one end and pulled at a constant rate of elongation until the center of the specimen fails. 

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

Bond strength between PC overlays and portland cement concrete substrate was measured using the pull-out test method [7], The tensile bond test is illustrated in Fig. 1. Specimens were thin overlays, about 1/2-in. (1.3-cm) thick, cast directly (without the use of a primer) on sandblasted portland cement concrete slabs. Circular grooves (4-in./10. 8-cm diameter) were cored through the overlays and into the portland cement concrete substrate. Circular steel disks... 

Pull tests were carried out using an Instron machine. The procedure used for determining the pull strength is given in a subsequent paper.(4) Pull tests were also performed in aqueous environments. After the curing step, the rods were immersed in boiling water for 2 h. The lower jaw of the Instron tensile tester was modified to perform pull tests in an aqueous medium. 

Tensile strength, Tensile strength is evaluated by pull testing on metal lap-shear coupons, most often aluminum. The standard test method is ASTM D1002, Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading (Metal-to-Metal) Alumi-... 

The elongation in a sample is the extensional strain that has built up in a polymer undergoing tensile or pulling tests. It is usually reported as "elongation at break", the strain or distension that caused the polymer sample to snap. Modulus, G, is the proportionality eonstant between strain and stress in a sample. Mathematically, it is the slope of the plot of stress versus strain. 

Instron tester Instron testers measure the flexural, tensile, and compressive strength of plastics as well as the stress-strain curves at ambient temperatures. They are commonly found in most materials testing laboratories. Instron testers come in a range of sizes (generally related to the maximum tensile pull that can be exerted) and types. They are manufactured by the Instron Machine Company. 

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