V. L. Newhouse

Bio: V. L. Newhouse is an academic researcher from Drexel University. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Approaches for the generation of stress waves in concrete

Abstract: This paper reviews several existing, as well as potential, stress-wave-generating techniques for concrete. The generating techniques under study include standard ultrasonic pulse generators, high-energy ultrasonic toneburst systems, and simple impact. In addition, the use of laser sources and ultrasonic lithotripters are proposed. The novelty of this review is that the methods are analyzed considering applications to existing concrete NDE methods. The strengths and weaknesses of each generation technique are discussed. Some of the methods are demonstrated through laboratory tests on a variety of specimen types. A description of each technique and conclusions concerning the appropriateness of each technique are also made.

Depth detection of surface-breaking cracks in concrete plates using fundamental Lamb modes

Abstract: Surface-breaking cracks affect the material and structural properties of concrete members, e.g. concrete plates. Therefore, the non-destructive measurement of the crack depths is important to assess the structural strength and serviceability of concrete plates. In this paper, a theoretical transfer function for a pulse propagating as Lamb modes is used to study the effects from the dispersion of Lamb modes and the participation of high-order Lamb modes. It is found that the fundamental symmetric Lamb mode dominates when a vertical Morlet pulse is applied at the surface; thus, wavelet transform is used for the analysis of the surface responses to extract information of the fundamental Lamb mode. The recently proposed wavelet transmission coefficient (WTC) is sensitive to normalized crack depths up to one-third of the wavelength. The crack depth is successfully evaluated not only in numerical simulations but also in experimental tests.

Acoustic methods for the nondestructive testing of concrete: A review of foreign publications in the experimental field

Abstract: Acoustic methods for experimental studies of the problems of nondestructive testing that are used in the analysis of the strength and other physical properties of concrete are reviewed on the basis of an analysis of foreign publications The classical through transmission, pulse-echo, and impact-echo methods, changes in the internal structure of concrete under loading, and factors that influence the correlation between the strength and acoustic-wave velocity are considered

Monitoring the setting times and strength gain of mortar using ultrasonic guided waves

Abstract: A guided wave approach that characterises the setting and hardening of early age mortar during the first twenty-four hours of hydration is presented. Using a through-transmission system, the method measures the energy leakage of the fundamental torsional wave mode from a cylindrical steel rod to the surrounding mortar. The evolution of the mortar properties are related to the energy leakage or attenuation of the guided wave. The study shows that the technique is useful for monitoring the strength development and the microstructure of varying water-cement ratios (w/c = 0.40, 0.50, and 0.60). In addition, the effects of chemical (accelerant and retardant) and mineral (silica fume and fly ash) admixtures on the guided wave are also presented and discussed. Compressive strength and setting time measurements were performed on the various mortar mixtures. Correlations were developed relating the energy leakage of the guided wave to the compressive strength and the setting times of the mortar.

Ultrasound and Sound Generation Alternatives for Concrete Structures

Abstract: Stress wave generation must be improved so that the innovative application of existing and new ultrasonic and sonic nondestructive testing techniques to concrete structures can follow This paper summarizes the experimental analysis of stress wave generating techniques for application to concrete structures which may serve as alternatives to commonly used techniques Electromechanical and piezoelectric-based sources which are driven by AM burst signals are analyzed The behavior of these alternative sources is compared to that of an impact source and a traditional piezoelectric source in terms of signal controllability and signal penetrating ability in concrete Part of this analysis is based upon tests performed on portland cement concrete specimens In this way the applicability to rough surfaces, such as those found on unprepared concrete structures is considered Descriptions of all generation methods are included and limitations of each method are detailed