Internal Friction Values Research Articles

Effects of Proline on Internal Friction in Simulated Folding Dynamics of Several Alanine-Based α-Helical Peptides.

We have studied in silico the effect of proline, a model cosolvent, on local and global friction coefficients in (un)folding of several typical alanine-based α-helical peptides. Local friction is related to dwell times of a single, ensemble-averaged hydrogen bond (HB) within each peptide. Global friction is related to energy dissipated in a series of configurational changes of each peptide experienced by increasing the number of HBs during folding. Both of these approaches are important in relation to future atomic force microscopic-based measurements of internal friction via force-clamp single-molecule force spectroscopy. Molecular dynamics (MD) simulations for six peptides, namely, ALA5, ALA8, ALA15, ALA21, (AAQAA)3, and H2N-GN(AAQAA)2G-COONH2, have been conducted at 2 and 5 M proline solutions in water. Using previously obtained MD data for these peptides in pure water as well as upgraded theoretical models, we obtained variations of local and global internal friction coefficients as a function of solution viscosity. The results showed the substantial role of proline in stabilizing the folded state and slowing the overall folding dynamics. Consequently, larger friction coefficients were obtained at larger viscosities. The local and global internal friction, i.e., respective, friction coefficients approximated to zero viscosity, was also obtained. The evolution of friction coefficients with viscosity was weakly dependent on the number of concurrent folding pathways but was rather dominated by a stabilizing effect of proline on the folded states. Obtained values of local and global internal friction showed qualitatively similar results and a clear dependency on the structure of the studied peptide.

Microbial Induced Calcite Precipitate Improvement of Aeolian Soil for Use as a Construction Material

An environmentally friendly and successful technique of soil improvement known as Microbial Induced Calcite Precipitation (MICP) has attracted the attention of geotechnical engineers. This study was conducted to modify the engineering behaviour of an aeolian soil bio-treated with Bacillus brevis (B. brevis) to evaluate its suitability for use in construction works. Stepped B. brevis suspension density (i.e., 0.5, 2.0, 4.0, 6.0 and 8.0 McFarland standards equivalent to 0, 1.50 × 108, 6.0 × 108, 1.20 × 109, 1.80 × 109 and 2.40 × 109 cells/ml, respectively) and cementation reagent (i.e., 0.25, 0.5, 0.75 and 1.0 M), respectively, were utilized to activate the MICP process. Compaction was conducted using British Standard light (BSL) (or standard Proctor) energy. Tests results indicate that the engineering behaviour of the bio-treated non-plastic aeolian silt soil improved. The maximum dry density (MDD) and the angle of internal friction values marginally increased, while cohesion and optimum moisture content (OMC) decreased with higher B. brevis suspension density and cementation reagent concentration. Peak angle of internal friction and minimum cohesion were recorded at 1.5 x 108 cells/ml. Highest unconfined compressive strength (UCS) value of 215.58 kN/m2 was obtained for specimen treated with 25 % B. brevis (6.0 × 109 cells/ml): 75 % cementation reagent (0.75 M) mix ratio. The results recorded show that the improved aeolian soil could be used in engineering works.

Effect of Sc contents on the mechanical properties and damping capacity of Al–Zn–Mg–Cu–Zr–Sc alloys with different grain structures

Al–Zn–Mg–Cu–Zr–Sc alloys with different Sc contents were fabricated by casting, deformation, and T6 treatment. Deformation methods including rolling and friction-stir processing (FSP) were used to design their grain structure. A low additive amount (0.1) of Sc cannot refine the grains of the alloy with rolling and T6 treatment, and it instead coarsened the grains. The reason was the non-uniform distribution of nanosize Al3(Sc,Zr) phases that led to the occurrence of abnormal grain growth during homogenization. Meanwhile, the alloy with only 0.1Sc exhibited finer grains after FSP and T6 treatment than the alloys subjected to the same process but with higher Sc additive amount. Alloys with rolling-induced elongated grain structure exhibited better mechanical properties, and alloys with FSP-induced fine equiaxed grain structure exhibited higher high-strain and high-temperature internal friction values. These features are important performance parameters for applications in fields where vibration and noise are sensitive. The optimum additive amounts of Sc for alloys with elongated and fine equiaxed grain structures were 0.25 and 0.1, respectively.

STUDI NILAI KUAT GESER TANAH HAMBALANG BERDASARKAN KADAR AIR

Soft soils have low strength and easy to compress when they are loaded. A soil compaction test is performed to measure maximum soil density at the optimum water content to evaluate the strength of soft soil. To maintain these circumstances, however, efforts are necessary to preserve the water content at optimal levels, which is not easy. In actual condition the compacted soil can still be penetrated by water through soil cracks occurred especially on the slopes. The shear strength of the soil will decrease if rainwater infiltration is excessive. In a laboratory investigation, direct shear testing (ASTM D3080 - SNI 3420:2016) was used to determine how changes in the value of the Hambalang clay soil shear strength as reflected by the cohesion value (c) and the soil shear angle (f). Creating soil samples with a fixed density and variations in water content (w). The test results at w = 14.47% obtained c = 0.047 kg/cm2, f = 45.75⁰; at w = 21.75% obtained c = 0.203 kg/cm2, f = 33.39⁰, at w = 26.62% obtained c = 0.186 kg/cm2, f = 24.10⁰, at w= 31.59% obtained c = 0.086 kg/cm2, f = 21.90⁰ and at w = 33.70% obtained c = 0.082 kg/cm2, f = 21.21⁰. From these results it can be concluded that the largest of cohesion and angle of internal friction or strength parameter values will reach at optimum moisture content.

Effect of second-step austempering temperature on mechanical damping of austempered ductile iron

Austempered ductile iron(ADI) has good strength and toughness, which is widely used in aerospace, engineering machinery and automobile manufacturing. In the above application fields, the requirements of safety and comfort are gradually increasing, so ADI is required not only to have excellent mechanical properties, but also to have high damping properties. The performance of ADI is closely related to its heat treatment method. Therefore, it provides a theoretical basis for the application of ADI, and reveals its mechanism to some extent. The influence of two-step ADI’s mechanical properties and damping properties due to two-step austempering quenching temperature is the main content of this paper. The retained austenite with obvious coarsening of bundle ferrite and increased size is the experimental result obtained after the increase of austempering temperature in the second step. After that, when the austempering temperature in the second step increases, the retained austenite content will directly decrease. The tensile strength of ADI will increase first and then decrease with the increase of austempering temperature in the second step. And the value reaches the maximum of 1350MPa at 360°C. The yield strength of ADI, which reaches the maximum value (1252MPa) at 400 °C, will follow the increase of austempering temperature in the second step, and the elongation and impact energy of ADI will gradually decrease. The elongation and impact energy of ADI will gradually decrease with the increase of austempering temperature in the second step. The minimum values of 4.8% and 42J are obtained when the austempering temperature in the second step reaches 400 °C. The impact fracture morphology shows that the fracture mechanism will change from ductile fracture to brittle fracture with the increase of austempering temperature in the second step. The reason why the internal friction value (Q−1) of ADI with different austempering temperatures in the second step increases gradually is the increase of strain amplitude. There are obvious S-K peaks and Ge peaks, that is, the damping characteristics change with frequency.

An experimental study on the effect of particle size and non-homogeneity on the shear strength of soil

Soil deposits available in nature are often present as homogeneous mixtures of particles of different sizes and base minerals or as a combination of soils in different layers forming a non-homogeneous configuration. This variability in soil has great influence on the shear strength behaviour. In this study, different naturally occurring soil particle sizes and shapes (angular and flaky) have been utilized as reinforcements in the form of layers to determine their influence on the soil shear strength. Therefore, triaxial tests have been conducted on homogeneous sand (where particles are mixed proportionately), and on non-homogeneous sand (different layer combinations of different particle sizes as well as the inclusion of angular and flaky particles). It has been observed that there was a substantial increase in the shear strength for non-homogeneous arrangement compared to homogeneous sand sample. Furthermore, the addition of flaky particles from 10% to 30% by weight of fine grained sand increased the angle of internal friction (ϕ) and cohesion (c) values thereby increasing the shear strength. However, for angular-fine sand layer combination, the addition of 10-20% of angular particles by weight shows a significant increase in shear strength in comparison to 30-100% of angular particles.

Investigation of phase transition, mechanical properties, and damping behavior of NiTip/6061Al laminar composites

The microstructure, phase composition, phase transition process, mechanical properties, and damping behavior of NiTip/6061Al laminar composites were investigated by introducing a NiTi particle layer with phase transition characteristics into the 6061 aluminum matrix using rolling composite technology. No defects, such as cracks or holes, were found in the NiTi particle layer, and no agglomeration of the NiTi particles was recorded. The interlayer interface between the alloy particle layer and the 6061Al matrix was clear and well-combined, and no new phase formation occurred in the composite. The composites exhibited phase transition characteristics similar to NiTi alloy particles, and the phase transformation temperature of the composites increased gradually with an extended aging time of the NiTi-reinforced particles. Following aging strengthening, the NiTip/6061Al laminar composites demonstrated higher yield strength than the 6061-T6 aluminum alloy, while their tensile strength remained similar. Pre-aging treatment of the NiTi particles had only a minor effect on the mechanical properties of the composites. The damping capacity of the laminar composites surpassed that of the 6061-T6 aluminum alloy due to the synergistic enhancement of phase transition damping from the NiTi particles and interparticle interface damping within the particle layer The internal friction values of the NiTip/6061Al laminar composites at 60 °C and 350 °C were up to 0.0134 and 0.1146, respectively, which were 211% and 313% higher than those of the 6061-T6 aluminum alloy at the corresponding temperature. The storage modulus and the comprehensive damping performance (EIF) of the NiTip/6061Al laminar composites were higher than those of the 6061-T6 aluminum alloy.

Development of Innovative Plate Load Testing Equipment for In-Situ Saturated Clays Soils

This study proposes a method of gradually loading plate load on-site using lever arms to squeeze out pore water from clayey soils, allowing the soil to settle. Several types of tests were conducted, including a conventional field plate load test (CFPLT), a numerical field plate load test (NFPLT) and an innovative field plate load test (IFPLT) proposed in this study. Three trial pits with soils of varied engineering properties were studied using CFPLT, which employed the use of a heavy jack for load application, the NFPLT test using PLAXIS and an IFPLT, which employed a lever arm to magnify the applied static load. Disturbed soil samples collected from these trial pits were tested for index properties while the undisturbed soil samples were tested using the undrained triaxial compression test (UTCT) and laboratory consolidation tests. The results of the index properties classified these three clay soils as silt of low plasticity (ML) for clay from site 1, and clay of low plasticity (CL) for clay from site 2 and 3. The cohesion and angle of internal friction from the UTCT recorded cohesion values were 28, 29 and 37 kN/m2 for sites 1, 2 and 3, respectively, while the angle of internal friction values were 13, 8 and 6° for sites 1, 2 and 3, respectively. The plate load testing using the three methods showed similar graph pattern except that the allowable load occurred at approximately 350 kN/m2 for the CFPLT and 150 kN/m2 for the IFPLT. The high value of bearing capacity in CFPLT is due to the short period of time taken to load from a jack, which allowed the test to be completed within a short period of time. The ultimate bearing capacities computed from the laboratory test have values of 315.0, 231.0 and 270.0 kN/m2 for sites 1, 2 and 3, respectively. These values agree closely with the bearing capacities obtained for CFPLT but higher than the values recorded for the IFPLT. This is probably due to the long period of sustained loading during testing, which allowed for dissipation of pore water during each loading. Settlements obtained using the IFPLT were close to 25 mm, which is recommended as minimum settlements for building structures BS 8004, 1986.

Experimental identification of the fractional parameter of the fractional derivative standard linear solid model for fiber-reinforced rubber concrete

This paper studies the influence of different factors, such as polymer and fiber type and aging, on the internal friction and fractional parameter, which are determined for rubber concrete and fiber-reinforced rubber concrete by means of the Resonant Frequency and Damping Analyzer (RFDA Basic) implementing the Impulse Excitation Technique (IET). Both materials contained low molecular weight cis-polybutadiene rubber SKDN-N as the main binder. Another type of binding material has been used for further investigation of internal friction phenomena in polymer concrete. Namely, low molecular weight polybutadiene rubber (BR) of mixed microstructure was utilized to produce the samples for the experimental program. Two different types of fiber are used: metal and polymer fiber. It has been found that the addition of steel fiber reduces internal friction in the material, whereas propylene fiber acts as additional damping material and increases internal friction. BR-based concrete and fiber-reinforced concrete show rather high values of internal friction, i.e. behave more viscoelastically. BR-based concrete performs higher values of the fractional parameter, and, therefore, more obvious viscoelastic properties. Introduction of steel fiber in the mixture reduces the fractional parameter, since it plays the role of additional bonds in the material structure. However, addition of propylene fiber increases fractional parameter in both, SKDN-N and BR-based concretes. It can be explained by additional damping effect of the polymer fiber. The obtained results are compared with those for the reference specimens made of ordinary Portland cement concrete, and a certain influence of the selected parameters on the internal friction of the considered materials are established.

Scientific Study for the Internal Dynamic Friction between Warp and Weft Yarns of Woven Fabrics

Fabrics are typically classified based on their weight, which may vary widely from light, medium to heavy-weight fabrics. On the other hand, weaving machines are also often classified into light, medium, and heavy according to the weight of the woven fabric on them. Although, this classification method of weaving machines may be incorrect in many cases, as there isn’t necessarily a relationship between the weight of the woven fabric and the classification method for weaving machines in general. This is confirmed by the research in our hands. Where the research plan is based on the analysis of the internal friction forces between the warp and the wefts yarns, which are interlaced with each other within the fabric construction. Those internal friction forces have a significant impact on the force needed to beat up the wefts, based on Newton's third law "To every action, there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal and directed to contrary parts". According to the previous mechanical theory, it is expected that the required beating-up force values certainly depend on the number of interlacing rates within the woven construction repeat more than the fabric weight. The research paper revealed several important points, including determining a theoretical basis for calculating the internal friction values between warp and weft yarns within the woven fabric structure based on the warp yarns’ tension during the weaving process. By determining the values of internal friction, it is possible to estimate the values of some mechanical properties of the fabrics. These calculation values can also be used to determine the appropriate machine for the weaving process with high precision.

Effect of a multi-phase structure on the damping response of a novel high entropy alloy

• Dynamic behavior of a multi-phase high entropy alloy is investigated in a wide temperature range. • Effects of processing and the resulting phase constitution on the damping response is underlined. • The storage modulus and the internal friction values of the annealed alloys are improved. In this study, dynamic behavior of a novel multi-phase high entropy alloy (HEA) was investigated. Thermo-mechanical processes containing an 80% reduction in room temperature rolling followed by annealing at 750°C and 850°C were applied to modify the microstructure and the resulting damping properties of the HEA. Annealing at 750°C introduced the BCC phase, while at 850°C, the sigma phase was precluded in the microstructure, leading to over 1 GPa strength with decent ductility in the latter condition. The storage modulus and the internal friction values of the annealed alloys are noticeably improved, indicating that proper heat treatments could enhance both the mechanical response and the damping performance of this HEA.

Stability of damping capacity and mechanical properties of high-Zn-concentration Al–Zn–Mg–Sc alloy

The microstructure, damping capacity, mechanical properties, and the performance stability of high-Zn-concentration Al–Zn–Mg–Sc alloys after annealing treatment were studied. The Al–20Zn–0.5 Mg–0.5Sc alloy contained fine grains, a high number of solution atoms, Zn phases, Al 3 Sc phases, and high-density fine η and η' phases. Decreasing the Zn content led to the disappearance of the Zn phases and the decrease of intragranular η phases density and solution atom number. Increasing the Mg content did not increase the number of solution atoms but increased the size of the intragranular η phases. The Al–20Zn–0.5 Mg–0.5Sc alloy exhibited higher internal friction value and higher strength than the other two alloys because of its satisfactory grain boundaries and Al/Zn interface sliding ability at high temperature, as well as its high solid solution and second phase strengthening effects at room temperature. All annealed Al–Zn–Mg–Sc alloys exhibited excellent damping capacity and mechanical properties stability during the DMA test at the highest temperature of 360 °C due to their high structural stability. • A novel Al alloy with excellent damping capacity, mechanical properties, and performances stability was obtained. • The satisfactory GB and Al/Zn interface sliding ability led to the Al–Zn–Mg–Sc alloy exhibited well damping capacity. • The high solid solution and second phase strengthening effects led to the Al–Zn–Mg–Sc alloy exhibited high strength. • Sc addition and annealing led to the Al–Zn–Mg–Sc alloy exhibited excellent structural and properties stabilit.

Effect of Ti addition on the damping and mechanical properties of solid-solution FeCrCoNi alloys

A series of multicomponent (FeCrCoNi)100−xTix alloys with excellent mechanical and damping properties were designed and prepared. After solution treatment at 1327 K, the multicomponent alloys exhibited a face-centered cubic structure, and their microstructures showed typical equiaxed grain characteristics. The effects of different Ti contents on the microstructure, damping properties, and mechanical properties of the alloys were investigated; the strengthening and deformation mechanisms were also explored. The addition of solid-solution Ti atoms increased the number of weak pinning points in the alloy, resulting in significant improvement in the damping properties. The damping property of the FeCrCoNi alloy was expressed in terms of its internal friction (Q–1) value of 0.032. When the Ti content was 1 (at%), Q–1 was 0.051. However, further increase in Ti content increased the number of immovable dislocations, resulting in reduced damping properties (Q–1 =0.0469 and 0.036) when Ti contents were 3 and 5 at% respectively. Tensile property measurements showed that with increasing Ti content, the strength of the alloy improved significantly via solid-solution strengthening, and the alloy exhibited a typical plastic fracture. When the Ti content increased from 0 to 5 at%, the yield strength increased from 217 to 337 MPa, the ultimate tensile strength increased from 592 to 728 MPa, while the elongation decreased from 77.7 % to 57.6 %, respectively. The main processing strengthening mechanism of the FeCrCoNi alloy was dislocation strengthening; the alloy(with 3 at% Ti) exhibited the double influence of dislocation and stack fault, while the alloy (with 5 at% Ti) showed a change in mechanism from dislocation-dominated to stack fault-controlled. It is a promising damping material with a wide range of applications.

INFLUENCE OF MECHANICAL POLISHING ON THE PHYSICAL-MECHANICAL PROPERTIES OF MONOCRYSTALLINE p-SiGe SUBSTRATES

The effect of mechanical polishing on the structural-sensitive physical properties of the monocrystalline p-SiGe substrates has been investigated. Non-monotonic changes in the electrical characteristics, optical absorption spectra of infrared radiation, internal friction and shear modulus values on the (111) surfaces of SiGe substrates treated with a polishing compound containing different dispersions diamond particles have been shown. Defects formed in the polishing process interact with boron and technological origin oxygen and carbon atoms. Defects of deformation origin are formed in the mechanical processing at room temperature. In the absorption spectra of infrared irradiation a decrease of the concentration of carbon and oxygen atoms and Ci-Cs, Ci-Oi, V-O defects have been revealed. It is supposed that the non-monotonic changes in the electrophysical and physical-mechanical properties on the (111) surfaces of SiGe substrates are caused by changes in the electrical activity of defects and mechanisms of the dislocation-defect associations interaction, formed in the polishing processes.

Improving the sub-base materials at Al-Fao port in Basrah Governorate-South of Iraq by adding some synthetic polymers and cement

The improvement process by adding polymers and cement has been carried out to sub-base material used in the compaction processes, in order to observe their effects on the geotechnical properties of the sub-base such as compaction, unconfined compressive strength, shear strength, California bearing ratio and absorption ratio. It has been observed that there is a significant improvement in the geotechnical properties of the soil as the value of the maximum dry density increased from 2.144 to 2.220 g/cm3, while the value of the optimum moisture contents decreased from 6.3 to 5.2% with a percentage of 5 % of the first polymer (Polyvinyl Acetate & Polyol). It is also revealed that there is an increase in the value of the unconfined compressive strength after adding 5% of the first polymer and 5% cement to the sub-base sample, and then soaked in water for different periods of time, the result was 11550 kPa with a soaking period of 28 days. Also, the angle of the internal friction values increased in testing the direct shear strength from 35◦ to 45◦ by adding 5% of the first polymer, and cohesion occurrence among the particles of the material under the action of the polymer as a adhesive material, the value reached 200 kN/m2. The California bearing ratio increased from 49% to 64% by adding 5% of the first polymer, while the absorption ratio decreased considerably at the same ratio and material from 9.8% to 4.1%.

Achieved improvement of damping capacity in Ti Ni shape memory alloy through He-ion irradiation

TiNi shape memory alloys have been widely used to eliminate noise and mechanical vibrations. However, narrow working temperatures and low damping performance limit its applications. Here, a high damping capacity with the relaxational internal friction close to 0.0524 at 5 Hz and the intrinsic internal friction close to 0.04512 are detected after He ion irradiation. The internal friction value greater than 0.02 in a wide working temperature range of 200 K is reported. Further analyses indicate the critical role of He ion irradiation in increase of damping property. We demonstrate that the high broad internal friction could be derived from the interaction between He/H atoms and martensite twinning interface, and the change in twinning type (111¯) type I twinning to (001) compound twinning in the irradiated layer. The He ion irradiation strategy disclosed in the current work is expected to be a promising way to design high damping alloys.

Insights into effect of first-step austempering temperature on the microstructure and properties of austempered ductile iron

Austempered ductile iron (ADI) is a revolutionary material with high strength and hardness combined with excellent ductility and toughness. The discovery of a two-step austempering process has resulted in superior combination of all the mechanical properties. Therefore, ADI has many different applications in varying fields. One notable application of ADI is in transmission components for new energy vehicles. As the automotive continues to develop, ADI transmission components with higher damping properties are required, because the damping properties of ADI affect the vibration and noise of the transmission system. However, the mechanism behind the damping of ADI, as well as a full characterisation of the damping properties, has not been thoroughly investigated in the literature. Therefore, it is necessary to reveal the influencing factors and mechanism of the damping properties of ADI. In this paper, the effect of first-step austempering temperature on the microstructure, mechanical properties, and damping properties of ADI was investigated. The results revealed that the tensile strength, yield strength, and elongation of ADI all initially increased, until reaching a global maximum value (1320 MPa, 1230 MPa, and 13.2%, respectively) when the first-step austempering temperature was 280 °C, followed by a decrease in value. Interestingly, the impact energy of ADI initially decreased before reaching a global minimum and then increasing to a maximum value of 93.5 J, when the first-step austempering temperature reached 320 °C. With increasing strain amplitude, the internal friction values (Q−1) of ADI treated with different first-step austempering temperatures all increased gradually, and the Q−1 values of ADI with first-step austempering temperatures of 240 and 260 °C were higher than those of other samples. Moreover, the damping properties of ADI varied with frequency with obvious S-K peaks and Ge peaks.

Advanced Calculation Model of V-Belt Temperature Field

In the process of continuous high-strength operation of the harvester, structure aging, surface hardening, brittle fracture, and other features appear on V-belt due to temperature rise, which seriously affects the service life of the belt and stability of the whole machine. To predict the temperature distribution of V-belt and improve its service life, an advanced calculation method of temperature field suitable for multiwheel is proposed. First, on the basis of analysing the heat source of the transmission belt, the values of internal friction and external friction are calculated based on AVL Excite Timing Drive (AVL Excite TD). Secondly, two-dimensional temperature field finite element calculation model is established by analysing the heat balance equation, determining the heat flow distribution coefficient and heat convection conditions. Then, to verify the calculation model of the temperature field, the experimental setup and instrumentation are built based on Controller Area Network-bus (CAN-bus) technology. At last, multi-condition tests are designed in this paper. The experiment results show that the maximum difference between the model calculated value and experiment is 4.77 ℃ in unsteady state, and 0.15 ℃ in steady state. Therefore, the multiwheel V-belt temperature field calculation model developed in this paper can realize the accurate calculation of the temperature field under steady state conditions. It has a very important guiding significance for reasonable selection of operating parameters and improvement of service lifetime of belt.

Influence of Al particle layer on damping behavior of Alp/7075Al composites fabricated by hot rolling

The Al particle reinforced 7075 Al matrix composites with the layered structure are prepared by hot rolling to improve the damping property of the alloy. Numerous interparticle interfaces are observed in the Al particle layer (reinforcement), and the traces of no interfacial reaction or elemental diffusion are found between the matrix and reinforcement layer. The tensile strength of the composite is 29% higher than that of the matrix. The internal friction values of the Alp/7075Al lamellar composite and the 7075 Al matrix are found to increase with the increase in temperature and strain, respectively. At 570 K, the internal friction values of the composites are found to be as high as 0.105, which is 337% higher than that of the matrix, and an internal friction peak (P2) appears in the composites due to the recrystallization of Al particles at high temperature. The comprehensive damping index of the composite is found to be about 2.9-fold of the 7075 Al matrix. The damping mechanism of the composite is mainly attributed to dislocation damping, grain boundary damping, and interface damping.

Structural Effects of Heat Treatment Holding-Time on Dynamic and Damping Behaviour of an Fe-28Mn-6Si-5Cr Shape Memory Alloy

The paper reports the structural effects of holding time period, during heat treatment, on the dynamic and damping behavior of a Fe-28Mn-6Si-5Cr (mass. %) shape memory alloy. After casting and hot rolling, solution treatment at 1050 oC was applied for five holding times, 2, 4, 6, 8 and 10 hours, followed by water quenching. The specimens were analyzed by scanning electron microscopy and X-ray diffraction which emphasized that only the 2-hours solution treated specimens contained ε-hexagonal close packed (hcp) martensite and experienced the highest internal friction value. These specimens were tested on a special device which transformed both tension and compression into tensile strain applied to the specimens and proved to be a promising solution for anti-seismic damper.