Showing papers on "Direct shear test published in 1991"

Joint conductivity variation due to normal and shear deformation

Abstract: Coupled shear conductivity tests have been performed on natural joints in magmatic, metamorphic and sedimentary rocks. Conductivity, normal and shear displacements and stresses were recorded. Whether joint conductivity increases or decreases with ongoing shear, depends on the joint/rock properties and the stresses applied. The uniaxial compressive strength, joint compressive strength, joint roughness coefficient, normal stress acting across the joint and shear displacement are anticipated to be the major parameters and a first attempt of quantification is undertaken

Point-load strength: An index for classification of rock material

Abstract: Point-load strength (Is) as a measure for the determination of rock strength and for estimating uniaxial (unconfined) compressive strength (UCS) are described and both put together and used for rock strength classification of brittle and hard rocks. The estimated point-load strength values of specimens of varying sizes and also the values corrected to a standard thickness of 50 mm, and the resultant point-load strength values (Is-50) have been used to estimate the uniaxial (unconfined) compressive strength which correlates well with actual recorded uniaxial (unconfined) compression test results. Using graphical and mathematical relationships between the observed and estimated UCS and Is values, a conversion factor of 16 is obtained for estimating uniaxial (unconfined) compressive strength values from point load strength results. A nomogram for computing point-load strength index and a system for the classification of rock material are presented.

Reinforcing Soil with Aligned and Randomly Oriented Metallic Fibers

Abstract: Laboratory direct shear box tests were used to evaluate the strength behavior of a reinforced uniform silty sand. The reinforcement elements consisted of flexible, semirigid, and rigid metallic fibers. The orientations of the fibers to the shear plane were varied and had a marked effect on the shear resistance. Increases in peak and residual strengths of 100 and 300%, respectively, were observed over unreinforced sand. Specimens reinforced with randomly oriented flexible fibers also exhibited a similar improvement of strength parameters.

Fatigue Properties of Wood in Tension, Compression and Shear

Abstract: The fatigue properties of wood laminates have been investigated in tension, compression and shear Fatigue lives in compression are significantly less than in tension, and S-N data at five R ratios has yielded a set of constant-life lines, the form of which is related to the failure mode of the wood observed by scanning electron microscopy A point of inflection in the constant-life lines at the transition between all compressive and partially tensile fatigue loading is a new observation S-N curves for wood laminates have been produced for shear across the radial-longitudinal and tangential-longitudinal planes, and the latter plane is observed to be more resistant to fatigue loads Samples with four times the cross-sectional area of standard-sized samples have been fatigued at R=−1 and no significant difference in fatigue life is apparent It appears that the absence of a size effect in tension-compression results from the orthotropic structure of wood which is insensitive to variations in the density of surface flaws

Dynamic Mechanical Properties of Pressure-Sensitive Adhesives

Abstract: The performance of pressure-sensitive adhesives (PSA) is related to the viscoelastic response of the bulk adhesives as well as to the surface energies of the adhesives and adherend. Testing the performance of a pressure-sensitive adhesive involves both the formation and destruction of a bond. For the typical tack, peel strength, and shear strength tests, the bonding conditions, such as the applied stress and dwell time, are specified, as are the debonding conditions of strain rate for tack and peel, and stress for time to failure in the shear test. To perform satisfactorily as a pressure-sensitive adhesive, the material must respond to a deforming force in a prescribed manner during both bonding and debonding. It must adhere to the substrate during bonding and exhibit a measurable resistance to separation at debonding conditions. In each of these steps, both the rate and extent of deformation are important. Bonding is a low rate process at low deformation, when the adhesive is brought into contact with a surface, while debonding in the tack or peel tests is a high rate process at high deformation relative to the thickness of the adhesive. The shear strength test is essentially a creep test carried to high deformation. Thus, the viscoelastic behavior of the adhesive controls its response in adhesive testing and is a major factor in its performance.

Soil-geosytnhetics interface strength characteristics: a review of state-of-the-art testing procedures

Abstract: Selection of appropriate geosynthetic materials for use in leachate collection and liner systems for solid and hazardous waste landfills requires a knowledge of the strength chracteristics of the soil-geosynthetic interface. Because there are several direct shear test procedures currently being used to evaluate soil-geosynthetic interface strength characteristics, these test procedures were reviewed and evaluated with respect to the effects of the test procedures themselves on test results. The review revealed that there is a wide range of interface strength characteristics reported and that there are significant variations in how interface testing is done.

Friction and passive resistance in soil reinforced by plane ribbed inclusions

Abstract: A theoretical analysis, supported by laboratory investigations, of stress transfer between soil and ribbed reinforcement has been performed to evaluate the individual contributions of friction and passive resistance to overall pullout resistance. The laboratory experiments consisted of direct shear tests of rigid ribbed inclusions with various rib spacings. Optical monitoring and a carbowax solidification technique assisted in the identification of failure surfaces. A plasticity model, based on Sokolovski's method, was evolved for a fully developed passive component of the pullout resistance. A parametric study revealed the significance of each of the model parameters. The optimum rib spacing is one which allows the maximum number of full passive zones to develop per length of reinforcement. For a rib height and width of 2·5mm, the optimum spacings were found to be 25mm for loose and 33mm for dense Ottawa sands. Une analyse theorique, basee sur des etudes faites en laboratoire, a ete effectuee du transfer...

Measurements of Strength Parameters of Concrete-Rock Contact at the Dam-Foundation Interface

Abstract: A long-term dam safety program has been initiated by Ontario Hydro to evaluate the safety of existing dams. Most of the dams in operation were constructed between 1910 and 1975. The larger dams are often of the concrete gravity type founded on rock. As an integral part of this program, laboratory methods for the measurement of the complete strength envelope of bonded concrete-rock contact and strength parameters of unbonded contact have been developed. The principal method and interpretation of each type of test are described in this paper. Typical results of tests on samples of dam-foundation interface recovered from existing dams are presented. The methods developed enable the determination of the strength envelope appropriate for the working stress level during operation of dams and the direct measurement of tensile strength and cohesion, thus removing the uncertainty of extrapolation for the cohesion component of strength in conventional triaxial and direct shear tests.

Measurement of soil strength in simple shear tests

Abstract: During a simple shear test the axes of stress rotate and, in a conventional apparatus in which the only stresses measured are the normal and shear stresses on horizontal planes, it is not possible ...

Fatigue Properties of Microelectronics Solder Joints

Abstract: Low cycle fatigue studies of solder joints designed and fabricated to represent generic interconnection structures typical of what might be used in packaging microelectronics have been carried out to assist in the development of a better understanding of the fundamental mechanical properties that determine the reliability of such structures. These studies involve micro scale joints (micro-joints) of both eutectic and 95/5 Pb/Sn solders fabricated by several different processes. In addition to a discussion of the results of recent tests reflecting specified loss-of-strength failure criteria and extensive post-test failure mode analysis of, primarily, 95/5 Pb/Sn micro-joints, descriptions of (1) the design and fabrication of the custom shear test vehicles and (2) the high-resolution electro-mechanical loading system used to apply cyclic loadings under isothermal conditions will be presented. This computer controlled system provides for the application of fully or partially reversed shear strains (with or without dwells) to either prototypes or custom test vehicles, and can be operated to maintain either total or plastic strain control during cycling.

A novel shear test for plasma-sprayed coatings

Abstract: A test method has been developed which allows the determination of the shear stress necessary to cause adhesive or cohesive failure of plasma-sprayed coatings. The shear stress measured turns out to be very sensitive to a change of spraying parameters and the quality of substrate surface preparation and is therefore well suited to describe the quality ofthe substrate/coating system for metallic as well as ceramic coatings. Sample preparation and testing are easy and inexpensive. In the case of ceramic coatings the Weibull modulus approach can be used to characterize the interface.

Shear moduli in Scandinavian clays; measurements of initial shear modulus with seismic cones; empirical correlations for the initial shear modulus in clay

Abstract: The shear stress-strain relations in soils have mainly been studied in the laboratory. Comparisons with field tests, however, have shown that there are considerable disturbance and time-effects in the laboratory tests. The initial shear modulus should therefore preferably be determined by field tests. A large number of investigations have shown that the various methods of field testing with cross-hole and down-hole techniques normally give compatible results. Compatible results are also obtained when a seismometer is incorporated in an ordinary CPT probe and the shear wave velocity is measured at regular intervals as the penetration test proceeds. The shear wave is then normally created by a hammer-blow on a steel-bar pressed against the soil by the weight of the drill rig. This is a cost-effective method and the equipment is commercially available. From the results in this investigation, it appears that the shear deformations created in this way may exceed the "elastic" range of deformations in the upper parts of soft soil profiles. An evaluation of the shear strain in the test therefore ought to be made and the results corrected for excessive shear strains.

The application of the iosipescu shear test to structural adhesives

Abstract: : The Iosipescu shear test method, adapted for adhesives, was used to evaluate shear stress-strain properties of five epoxy-based film adhesives. The shear strength of some adhesives, determined by this technique, was found to differ greatly from that determined by either lap shear and/or thick adherend tests. Accurate measurements of the adhesive bond-line deformation enabled evaluation of the adhesive elastic and plastic properties as well as the calculation of shear modulus. A high-speed video camera was employed to augment observation on the joint deformation.(Author)

Ring shear characteristics of clays in fractured-zone-landslide

Abstract: 破砕帯地すべりのすべり層の粘性土の残留強度特性をリングせん断試験により調べた. その結果, 残留状態におけるせん断抵抗角φrは10°～30°程度であること,φrと塑性指数Ipあるいは粘土分含有量CFとの間に従来指摘されているような相関は認められないこと, また,φrは粘土鉱物と粒度の影響を大きく受けることなどが明らかになった.

Iosipescu Shear Test Apparatus Applied to Wood Composites

Abstract: In-plane and transverse (through-the-thickness) shear strength properties were evaluated for three wood composite materials. A modified Iosipescu test apparatus was used to determine shear strength relative to the six possible material orientations. In-plane shear was also characterized using ASTM D1037-87 test standards. The Iosipescu shear test method was developed originally for metals testing. However, different forms of the test device have evolved for purposes of shear evaluation with numerous nonisotropic materials being evaluated. Previous research for various materials has shown satisfactory results with repeatability and apparent shear failure. The current research specifically utilized the University of Wyoming version of the original shear test device. Iosipescu test results for in-plane shear strength were comparable to values derived from the ASTM test method. Transverse shear strength values were found to exceed the magnitude of previously published ASTM test results. Greater directional or material orientation differences were observed for transverse shear properties.

Prediction of ultimate shear strength of vertical joints in large panel structures

Abstract: Load-bearing precast concrete walls are designed to transmit large shear forces through the vertical joints between the reinforced concrete panels. The resistance to shear is provided by the shear strength of the in-isitu concrete of the joint and the dowel action of the reinforcement crossing the joint. In this paper the available empirical, theoretical, and shear friction design formulas for the prediction of the ultimate shear capacity of joints are compared. A modified formula for castellated and plane joints based on the Mohr-Coulomb's failure criterion is proposed and calibrated using test data available in the literature.

The effect of surface pretreatment on carbon fibre–polyimide matrix composite bonding

Abstract: The single lap shear test and the wedge test were used to evaluate the effect of surface pretreatment on the strength and durability of adhesively boned composite joints. Both types of joints were placed in three different environments: (1) room temperature, desiccator, 1000 h; (2) 204°C, 1000 h; (3) immersion in boiling water for 3 days for the single lap shear test and until failure for the wedge test. The failure surfaces were analyzed using XPS to determine the locus of failure. An oxygen plasma was found to be the best pretreatment. The improvement in adhesive bonding following exposure to an oxygen plasma in comparison to the other surface pretreatment was attributed to several factors—a reduction in fluorocarbon contamination caused better wetting of the composite surface and also may lead to covalent bonding at the composite/primer interface.

Development in wedge shear testing of unsaturated clays and gravels

Abstract: Means for measuring the shear strength at large strains in the wedge shear test over about the same range of normal stresses as at peak strength are described. By the same means it is now possible to prolong the test for larger shear displacements when loading is near-vertical; to perform a re-shear test on cut planes; to obtain a strength envelope using a single test mould; and to perform a multi-stage shear teat if desired. A double-cut, cylindrical teat mould is described which enables clays or fine gravels to be sheared, in the same moulds in which they have been compacted, along planes relevant to the slope stability of embankments. A sufficiently accurate shear strength envelope can be obtained from two such cylindrical wedge shear tests (cylwests) which can be performed within 1 h. A larger version of this set-up, using a portable frame and a prismatic box cut to provide a shear plane area of 9OO cm2 as in the in situ wedge shear teat (iswest), is also described. This version (priswest) has been us...

Fracture characteristics of cement-stabilized soils

Abstract: Fracture characteristics of cement-stabilized soil under Mode I (tensile) and Mode II (in-plane shear) were investigated on a series of cube specimens. The linear elastic fracture mechanics approach was applied to study the stress distribution in the specimens and also to determine the constitutive equations for fracture parametersKI andKII. The experimental studies were carried out on a range of 100 mm soil-cement cube specimens modified for fracture testing by inserting a series of slots. It was shown that results predicted by numerical models were in acceptable agreement with the experimental observations. The fracture parameterKI was found to be in the range 0.11–0.17 MN m−3/2 and the parameterKII in the range 0.31–0.45 MN m−3/2. This result indicated that the soil-cement exhibited a greater resistance to shear fracture than was expected.

Stress–strain behaviour of sands in triaxial and direct simple shear tests

Abstract: The behaviour of a natural sand in triaxial compression and direct simple shear tests was compared by means of dimensionless analysis of parameters controlling the evolution of stresses and strains...

Use of the in-process bond shear test for predicting gold wire bond failure modes in plastic packages

Abstract: A strong relationship is found between in-process (post wirebond) bond shear test results on gold ball bonds and post-process, post-board mount wire pull results. The shear test results detect clear differences in shear strength and failure mode between two types of bond pad structures. Significant variation due to the level of ultrasonic power used in bonding was also found. The subsequent wire pull results obtained from units receiving full package assembly and simulated customer board mount agreed with the in-process shear findings of both pad structure and bonding process effects. The results have promising implications for the use of in-process bond shear as a tool for improving ball bond reliability through wirebond process control and bonding parameter optimization. >

Shear strength of sand-geomembrane interfaces for cover system and lining design

Abstract: The paper discusses an experimental program involving 450 direct shear tests in which values were developed for the design of soil-geomembrane cover systems and linings. Interface shear strength parameters are reported as a function of soil type and unit weight, polymer type, normal stress, repeated loadings, and physical features of the surfaces. Recommendations are given for choosing interface shear strength parameters and applying them to design geomembrane-based containment systems for waste impoundments.