The sintering parameters of hot-pressing diamond drill bit mainly contains the sintering temperature, holding time, sintering pressure and the pressurized method. The length of holding time is directly related to the performance of diamond drill bit. This article mainly discusses the effect of holding time on the performance of diamond drill bit. First, a general formula of diamond drill bit is chosen. A group of samples in this parameter were loaded and sintered. Holding time is set as variable, while other parameters remain the same. The optimal holding time for this formula is obtained through the mechanical properties tests on the samples’ bending, tension, compression, and hardness, and fracture analysis using scanning electron microscopy (SEM).

A tentative experiment has been conducted on polymer modified cement concrete now widely used. By filtering through 297 kinds of traces of polymer modified cement concrete samples tentatively mixed, we acquire a proper mix proportion, according to which, a total of 75 groups of 225 polymer modified cement concrete specimens are produced. After further selective preference of these specimens, ultrasonic test is done on the selected ones under different loading conditions. Afterwards, signal processing is accomplished by using wavelet transformation and we preliminarily find a kind of acousto-elastic sensitive concrete material which is comparatively sensitive to stress. This kind of material is produced by mixing epoxy resin, styrene-acrylic emulsion, acrylic emulsion, auxiliaries and iron powder into cement concrete together. The sensitivity of ultrasound and stress of this kind of modified concrete behaves preferably well as follows: at the low stress stage, not only the correlativity curve of ultrasound velocity and stress but also the correlativity curve of weighted spectrum area and stress arises apparently. If this kind of material can be applied to the practical engineering successfully, the acousto-elastic test accuracy of the concrete service stress will be greatly improved.

For the task of evaluating the inclusions in the steel specimen under high efficiency testing condition, it is important to make it clear that what testing sensitivity the ultrasonic method can reach for a specimen of large size, especially a thick one. In this paper, this problem is researched and discussed. Before experimental researching, we simulated the focused ultrasonic field formed in the steel specimen by DPSM (Distributed Point Source Method), the frequency ranges from 7.5MHz to 15MHz. DPSM analysis reveals that the ultrasonic field of certain strength can be formed in the thick steel specimen of coarse grain, and the focused transducer of 15MHz is suitable for the inclusion evaluation of thick steel specimens. Then, with the help of a precise micro-step C-scan equipment and the 15Mhz transducer (13mm Diameter, 255mm focal length), the ultrasonic test sensitivity research work was carried out on the thick steel specimen, by the way of testing the inclusions which's size were as tiny as possible, and located as far from the testing surface as possible, and at last, the ultrasonic detection results were testified by mechanical dissection. The dissected inclusions which can be tested are grouped into 8 different grades by its size, it is demonstrated that the deepest inclusion can be tested in the specimen is about 80mm beneath the testing surface by ultrasonic method, and reflection area is about 0.02mm2, equivalent to a circle inclusion of diameter 0.16mm. In addition, there are some semi-quantitative relationships can be drawn among the grade of inclusion, the location depth of inclusion in the specimen, and the reflected ultrasonic signal strength from the inclusion, this give a way of evaluating the inclusion size in the thick steel specimen by the focused ultrasonic method.