This application relates to an apparatus and method for detecting a microcrack using orthogonality analysis of a mode shape vector and a principal plane in a resonance point. The apparatus may include a measurement unit comprising multiple sensors and configured to measure whether a crack exists at a measurement target, and an analysis unit configured to determine whether a crack exists, on the basis of measurement values of the respective sensors. The measurement unit includes a fixing jig configured to fix the measurement target, an excitation means configured to apply a predetermined impact to the measurement target, and multiple acceleration sensors attached at predetermined locations on the measurement target. The analysis unit may further calculate frequency responses of the measurement target to the impact applied by the excitation means, and determine whether a crack exists by analyzing the number of resonance points and independence of the resonance points.

According to one embodiment, a diagnostic method includes changing a position of a mechanical structure to be diagnosed with a drive unit based on an acceleration command, the acceleration command being generated based on a log swept sine (LOGSS) signal, calculating an impulse response based on the acceleration command and measured acceleration of the mechanical structure, the measured acceleration being measured by an accelerometer, analyzing at least one of a linear characteristic and a nonlinear characteristic relating to the mechanical structure based on the impulse response, and diagnosing the mechanical structure based on the at least one of the linear characteristic and the nonlinear characteristic relating to the mechanical structure.

A method for preparing a SiC ingot includes: disposing a raw material and a SiC seed crystal facing each other in a reactor having an internal space; subliming the raw material by controlling a temperature, a pressure, and an atmosphere of the internal space; growing the SiC ingot on the seed crystal; and collecting the SiC ingot after cooling the reactor. The wafer prepared from the ingot, which is prepared from the method, generates cracks when an impact is applied to a surface of the wafer, the impact is applied by an external impact source having mechanical energy, and a minimum value of the mechanical energy is 0.194 J to 0.475 J per unit area (cm.sup.2).

A tester for evaluating pullout load capacity and bond quality of anchor bolts embedded in concrete includes a Schmidt hammer for measuring a rebound number and an ultrasonic pulse velocity tester for measuring the transit time of a pulse transmitted through concrete surrounding an anchor bolt. The rebound number and the transit time are combined and matched against a database record which identifies the pullout load capacity and the bond quality. The transit time is matched to thresholds of transit times associated with porosity, internal cracking, air voids, and water pockets located around the embedded anchor bolt. The Schmidt hammer is further modified by the incorporation of a digital level for measuring the vertical and horizontal angles of inclination of the plunger with the concrete surface, a guide tube for supporting the plunger, and by using a convex plunger tip for improved registration with anchor bolt head.

This application relates to an apparatus and method for detecting a microcrack using orthogonality analysis of a mode shape vector and a principal plane in a resonance point. The apparatus may include a measurement unit comprising multiple sensors and configured to measure whether a crack exists at a measurement target, and an analysis unit configured to determine whether a crack exists, on the basis of measurement values of the respective sensors. The measurement unit includes a fixing jig configured to fix the measurement target, an excitation means configured to apply a predetermined impact to the measurement target, and multiple acceleration sensors attached at predetermined locations on the measurement target. The analysis unit may further calculate frequency responses of the measurement target to the impact applied by the excitation means, and determine whether a crack exists by analyzing the number of resonance points and independence of the resonance points.

The penetrometer includes a chassis, a mast mounted thereon and positioned substantially vertically during a test, a rod string, including a tip penetrating the ground that is positioned at one end of the rod string, an anvil that bears against the rod string at an end opposite the tip, a hammer striking the anvil, elements for raising the hammer along the mast up to a fall height, at which the hammer is released, and elements for measuring the sinking of the tip into the ground. The penetrometer further includes an electronic control unit for controlling the fall height, and configured to select the fall height adopted for the test based on the sinking of the tip measured by the measuring elements during one or more earlier tests, and mechanical elements controlled by the control unit for triggering the fall of the hammer at the height selected by the control unit.

A method and a test fixture for evaluating a junction between an electrical lead trace and a busbar are described, and include an electric power supply disposed to supply electric power to the electrical lead trace and an electric monitoring device disposed to monitor electrical potential across the junction. A mechanical stress-inducing device is disposed to apply mechanical stress proximal to the junction. The electric monitoring device monitors the electrical potential across the junction of the electrical lead trace coincident with the mechanical stress-inducing device applying mechanical stress proximal to the junction when the electric power supply is supplying electric power to the electrical lead trace. Electrical integrity of the junction is evaluated based upon the monitored electrical potential across the junction.

This disclosure provides methods of predicting the steady state small scale critical temperatures (S4 T.sub.c) of polymer resins and pipes therefrom.

An impact testing machine is configured. The impact testing machine includes: a testing machine body that applies a load having a prescribed speed to a test piece and conducts a test; a controller that controls the testing machine body; a video camera that photographs the test piece; and a pulse generator. The controller includes: a detection signal capturing unit that captures a detection signal of the load in a prescribed measurement sampling period; and a synchronizing signal output unit that outputs a sampling synchronizing signal that is synchronized with the measurement sampling period. The pulse generator includes: a photographing instruction signal generator that generates a photographing instruction signal by multiplying or dividing the sampling synchronizing signal, and outputs the photographing instruction signal to the video camera. The photographing instruction signal issues a photographing instruction to the video camera.

A device and method are provided for determining whether a laminate is bonded or debonded from its substrate. The device and method provide simple, accurate, rapid, cost-effective, and reliable means for assessing the bonding state of a laminated substrate.