Characteristic Tearing Energy and Fatigue Crack Propagation of Filled Natural Rubber

Below the incipient characteristic tearing energy (T0), cracks will not grow in rubber under fatigue loading. Hence, determination of the characteristic tearing energy T0 is very important in the rubber industry. A rubber cutting experiment was conducted to determine the T0, using the cutting method proposed originally by Lake and Yeoh. Then, a fatigue crack propagation experiment on a edge-notched pure shear specimen under variable amplitude loading was studied. A method to obtain the crack propagation rate da/dN from the relationship of the crack propagation length (Δa) with the number of cycles (N) is proposed. Finally, the T0 obtained from the cutting method is compared with the value decided by the fatigue crack propagation experiment. The values of T0 obtained from the two different methods are a little different.

Thermographic Investigation of Fatigue Crack Propagation in a High-Alloyed Steel

Crack propagation experiments under constant stress intensity conditions were performed on SEN specimen of a high-alloyed steel. The experiments were accompanied by thermo elastic stimulated lock-in thermography investigations. The experiments showed that the crack propagation rate decreases with increasing crack length. Concurrent an increase in the dissipated energy in an area beside the crack flanks as well as in front of the crack tip was observed. The size of the plastic zone was also determined by thermographic measurements and was found to be constant during the crack propagation experiment. The increase of the dissipated energy doesnt reflect in the size of the plastic zone but seems to be responsible for the decrease of the crack propagation rate.

Study on the Damage Tolerance of a Stiffened Panel with a Skin Pad

During the development of an aircraft structure design, designers draw out a skin-stringer panel with a skin pad on the basis of a conventional skin-stringer panel(skin is directly connected with stringer by rivets or there was a sheet betweeen skin and stringers) to reduce the manufacturing cost. In this paper, we calculated the SIF of three kinds of skin-stringer panels by FE. And then, we analyze the damage tolerance of these structures by fortran program. Especially we carried out a crack propagation experiment of a skin-stringer panel with a skin pad and compared it with the results of a static analysis. Finally we researched the influence of the thickness of a skin pad on the damage tolerance. According to the researches above we concluded the advantages of the skin-stringer panel with a skin pad on the damage tolerance, and presented some suggestions about the thickness of a skin pad.

Crack Propagation Experiments on Flip Chip Solder Joints

ABSTRACTThe paper presents crack propagation experiments on real flip chip specimens applied to reversible shear loading. Two specially designed micro testers will be introduced. The first tester provides very precise measurements of the force displacement hysteresis. The achieved resolutions have been I mN for force and 20 nm for displacement. The second micro tester works similar to the first one, but is designed for in-situ experiments inside the SEM. Since it needs to be very small in size it reaches only resolutions of 10 mN and 100nm, which is sufficient to achieve equivalence to the first tester. A cyclic triangular strain wave is used as load profile for the crack propagation experiment. The experiment was done with both machines applying equivalent specimens and load. The force displacement curve was recorded using the first micro mechanical tester. From those hysteresis, the force amplitude has been determined for every cycle. All force amplitudes are plotted versus the number of cycles in order to quantify the crack length. With the second tester, images were taken at every 10th … 100th cycle in order to locate the crack propagation. Finally both results have been linked together for a combined quatitive and spatial description of the crack propagation in flip chip solder joints.