Papers by Keyword: Strength Ratio

Abstract: Geotechnical engineering in tension damage is one of the major failure modes. For a long time, Brazil test has practical significance and wide application value that has been used to determine the tensile strength of rock. When the specimen center destroyed tensile stress play a major role that is the theoretical basis of Brazil test. This is uniaxial tensile stress state, but the reality is complex stress state. Theoretical analysis shows that the Brazilian test does not truly reflect the tensile strength of rock, its test results to error. In this paper, two-parameter parabolic Mohr strength criterion for this error analysis, and propose amendments to the formula.

Abstract: The strength ratio, thickness ration of blanks and the microstructure of weld seam play important role in the formability of tailor welded blanks (TWB). With numeric simulation technology in different conditions such as different thickness and different strength combination of TWB’s materials, the forming limit depth (FLD) of tailor welded blanks is analyzed. The affect of the thickness ratio and strength ratio on forming limit depth is investigated, the laws influencing the formability of TWB square box are summarized, and approaches are presented to increase the FLD. The results of simulation and practice indicate that reducing the difference of the thickness ratio, choosing lower strength material for thicker blank, and adopting right heat treatment can improve the forming limit depth. Keywords: Tailor Welded Blanks; Forming Limit Depth; Thickness Ratio; Strength Ratio

Abstract: To propose a prediction formula of compressive strength of concretes containing fly ash (FA concrete), over 1600 strength data are collected from previous studies and discussed in this study. In particular, the study focuses on developing strengths of FA concrete. The study deals with test data of concrete with wide range of FA replacement, namely 0-50% by mass of cement. Compressive strength at age of 7 days has strongly relation to the cement-water ratio, so the strength can be predicted by using only water and cement contents. In addition, early age strengths within 7 days can be estimated by using the Goral curve based on strength ratio. Strength after the age of 7 days can be predicted by using replacement ratio of fly ash because the strength ratios are proportional to the replacement ratio. Based on the findings, a simplified formula for predicting compressive strength at various ages is proposed in the paper.

Abstract: It’s necessary to establish criterion of recycled fine aggregate for the application of recycled concrete and recycled mortar. Strength ratio and water demand ratio are important technical indexes of recycled aggregate. In this paper, a series experiments are hereby performed to determine testing and classification method for recycled fine aggregate. The experimental results indicate that fineness modulus of recycled sand influences inversely the strength ratio and water demand ratio. Furthermore strength ratio of various aggregates decreases with the increasing of water demand ratio in using identical cement type. The present paper also provides definition and testing method of water demand ratio and strength ratio. Consequently the quality classification criterion for recycled aggregate is proposed based on the double-control concept of water demand ratio and strength ratio and has been adopted by national code “Recycled fine aggregate for concrete and mortar”(Revision for Approval).

Abstract: The strength ratio between two blanks of tailor welded blanks (TWBs) plays an important role in the formability aspect. To study the strength ratio effects on the formability of TWB is significant while more and more TWBs were applied in auto industry. The formability of TWBs square cup was analyzed by numeric simulation technology in the terms of different strength combination TWBs. The results indicate that the formality goes worse dramatically when the strength ratio bigger than 2.0 and the crack located on the higher strength blank side when the crack appeared. The results are applicable.

Abstract: A series of formulas about two-parameter parabolic Mohr strength criterion(2-PP Mohr criterion) are derived. Based on the results of uniaxial tension and uniaxial compression tests, the parameters involved in the criterion can be easily determined, then the criterion in terms of the major principal stress and the minor principal stress is derived, and the damage pattern is also discussed. At last, the formulas about the rupture angle and the friction angle are presented, and their relationship is also given. 2-PP Mohr criterion can describe not only shear but also tensile failure. In this criterion the ratio of the uniaxial compression strength and the uniaxial tension strength is not confined as in Griffith criterion. The formula about the rupture angle provides steady theoretical foundation for determining the direction of crack faces and damage patterns in the computation of macro crack propagation. In fact, Griffith criterion is only a special case of the two-parameter parabolic Mohr strength criterion proposed in this present paper.