In terms of safety and environmental impact, trivalent chromium plating is a potential surface treatment which alternates conventional hexavalent chromium plating. In order to improve the tribological properties, including friction characteristics, of the coating from trivalent baths, the authors attempted to incorporate silicon carbide (SiC) fine particles in the coating. Composite coating incorporating SiC particle deposited on a mild steel rod substrate successfully reduced the friction coefficient against alumina rod even while no significant increase in film hardness was achieved by particle incorporation. The effect of the coating hardness on the reduction in friction coefficient was limited. It was supposed that a possible reason for friction reduction was attributed to the reduction in the contact area by the incorporated particles. Coating surface texture modified by incorporating SiC particle should have contributed to the reduced friction because the texture allowed to bury wear debris and SiC particles detached from the film. Such a feature was supposed to promote reduced shear resistance as well as eliminate three-body abrasive wear.

It is increasing to utilize the high-strength connection with the shear performance of wood for timber structures. However, it doesn't have enough data to understand the shear performance of wood, especially, in the long-term. In this study, the long-term performance of timber was investigated using the developed tensile shear test method. The creep and creep limit tests were conducted for long-term shear performance in parallel to the grain. Both tests were loaded at 30-80 % load levels, and the strength modification factors and the deformation modification factors were calculated. The initial deformations of long-term loading tests were equivalent to those of control shear tests. The strength modification factor calculated from the creep limit tests was considered to be 60-70%. The deformation modification factors calculated from the creep tests were well above 2 for both the Japanese building standard law and the power law.

Understanding the time-dependent behavior of rock is crucial in rock engineering and geoscience for tasks such as long-term stability assessments of underground structures and to elucidate long-term deformation of the crust. Creep tests, which are used to investigate time-dependent deformation under constant stress, have been used extensively in studies on rocks. However, most previous creep tests were conducted over periods of less than a few weeks, and only a few tests have been performed over several years. The authors initiated a uniaxial compression creep test with tuff submerged in water at a creep stress of 30% of its strength on May 23, 1997, and have continued this test for more than 26 years. This paper provides an overview of this creep test, including the methodology employed and long-term maintenance. Although slight changes in creep stress, temperature, and humidity have affected the recorded creep strain, its long-term trend can be approximated by a power function of time and is similar to the trends of creep strains observed at higher creep stresses. Compared to previous bending creep tests conducted with dry granite for 30 years, the creep test in this study showed minimal differences in creep stress level and strain rate, despite differences in rock type, loading conditions, and test environment. The current creep test with tuff will be continued for as long as possible.

Concrete form of tunnel lining is generally demolded earlier than other concrete structures. In particular, the demolding of ceiling form of tunnel lining is approximately 12-20 hours of concrete age. Note is that such early strength of concrete is hardly examined at site. Hence, a proper strength-estimation of tunnel lining concrete at early age is needed to demold the concrete form. Strength development of concrete at early age must be strongly related to cement hydration process. To develop a non-destructive testing (NDT) technique evaluating concrete strength, a hyperspectral camera which can quantify cement hydration was used in this study. Hyperspectral images consist of wide-range wavelength, it can obtain invisible variations of hydrated cement compared to general red-green-blue (RGB) images. A fundamental study was conducted to examine cement hydration by using the hyperspectral camera. The study proposed a cumulative reflectance for quantitative evaluation of the hyperspectral image. The study examined the relation between the cumulative reflectance and compressive strength of hydrated cement paste. In addition, chemical reaction of alite and calcium hydroxide in the cement paste were examined to quantify the cement hydration. The fundamental test revealed that the cumulative reflectance is applicable to estimate cement hydration degree. The NDT technique using hyperspectral image has a possibility for estimating the strength of tunnel lining concrete.