To accurately assess mechanical properties of micro- and nano-sized specimens, a reliable material testing system is indispensable. However, due to small sizes of these test specimens, in-situ measurement of their mechanical behavior necessitates installing the tester within high-magnification microscopes such as SEM. Traditionally, researchers have used wired methods by placing the tester inside the SEM chamber and connecting it to an external controller via electrical feedthrough. Unfortunately, this approach is cumbersome. In addition, it limits its compatibility with other SEMs. In this study, we developed a compact controller capable of driving 3-axis piezoelectric actuators with nanometer-level displacement control resolution via Bluetooth communication. This innovative setup enables wireless control and data acquisition from outside the closed confines of an SEM chamber. To validate the versatility of our tester, we conducted both a nanoindentation test on a fused silica specimen using a Berkovich indenter in a wired configuration and a copper micropillar compression test wirelessly using a flat punch indenter within an SEM. By installing this tester in various measurement systems, researchers could observe deformation patterns in real time, making it a valuable tool for investigating deformation mechanisms of diverse micro- and nano-sized specimens.

The main shaft of a mechanical press inevitably includes significant stress concentrations that can trigger severe mechanical damage and finally lead to failure under repetitive use. In this study, an efficient procedure to quantitatively evaluate the fatigue life of the shaft system including the main shaft and its support bearings, based on the macroscopic failure analysis of the main shaft broken during actual use, was investigated. For this purpose, the bearing support was modeled as an elastic foundation, and the elastic foundation stiffness value was varied to determine the optimal value that best simulates the failure behavior, especially with respect to the failure location and failure sequence, of an actual shaft. While the finite element mesh size was kept the same, only the effect of elastic foundation stiffness was investigated. The optimum value for the main shaft investigated in this study was approximately 60 N/mm³, and the fatigue life of the shaft was evaluated based on the conventional maximum principal stress theory. Based on this, two modified designs to enhance the fatigue life of the existing shaft are proposed.

A reliable tensile test technique for PDP’s barrier rib materials was introduced. A tensile specimen was prepared by punching out of green sheet, curing the specimen in a high temperature furnace, attaching sand paper tabs on each grip ends, and then attaching two strain gages for the strain monitoring and specimen alignment. Preliminary tensile tests were successfully done with the specimens made from ZnO-based lead-free green sheet. The specimens cured at 3 different maximum curing temperatures were tested to demonstrate the applicability of the test method. The Young’s modulus was 88 ± 4 GPa regardless of the maximum curing temperature. The ultimate tensile strength was decreased with increasing the temperature. The tensile test method proposed in this study was proven to be reliable, useful and easy to estimate the bulk mechanical properties of barrier rib materials.

Hydroforming is a cost-effective way of shaping malleable metals such as steel into lightweight, structurally stiff and strong pieces. With the increased use of the hydro formed components in automotive and aerospace industries, it is important to know the variations of the mechanical properties in the hydro forming process for the safe and durable design purposes. The principal goal of this paper is to suggest a procedure to evaluate the variations of tensile and fatigue properties before and after a hydroforming process. A miniature specimen, which is 0.2 ㎜ thick and 2.3 ㎜ wide, is devised and tested to measure local mechanical properties. The effects of specimen size, defects, surface roughness, and hydro forming on the tensile and fatigue behaviors are discussed.

Thin films play an important role in many technological applications including microelectronic devices, magnetic storage media, MEMS and surface coatings. It is well known that a thin film’s material properties can be very different from the corresponding bulk properties and thus there has been a strong need for the development of a miniature tester to measure the mechanical properties of a thin film. Two testers are designed and set up in small size of 62 ㎜ width, 20 ㎜ depth and 90-120 ㎜ height to fit in a chamber of scanning electron microscope (SEM). One tester has a homemade 0.2 N load cell and a low-priced electromagnetic actuator. The other has a commercial 5 N load cell, a 52 ㎛ piezoelectric actuator and some novel grips. Two types of 3.5 microns thick polysilicon specimen are tested to prove the testers’ applicability. The strain is measured by the two ways. Firstly, it is measured by an ISDG system in the atmosphere for the reference. Secondly, the same test is repeated in a SEM chamber to monitor the strain as an in-situ experiment. The strain is evaluated by observing the gap change between two markers.

Techniques and procedures are presented for measuring mechanical properties on thin-film polysilicon. Narrow platinum lines are deposited 250 ㎛ apart on tensile specimens that are 3.5 ㎛ thick and 600 urn wide. Load is applied by a piezo-actuator and by hanging weights. Strain is measured by an ISDG at temperatures up to 500℃. Measurements of the elastic modulus with jig modifications, loading speed and temperature change are presented first. And then, the preliminary data for the coefficient of thermal expansion and creep behavior are presented as a reference.