• Title, Summary, Keyword: Mechanical strength

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Study on Prediction of Mechanical Joining Strength of Blow Motor Case Joint (블로우 모터 케이스 이음부 기계적 결합 강도 예측에 관한 연구)

  • Kim, Gug-Yong;Kwon, Il-Keun;Park, Jun-Woo
    • Journal of the Korean Society of Industry Convergence
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    • v.20 no.1
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    • pp.81-87
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    • 2017
  • In order to reduce the weight of the blow motor case and to maintain the strength of the motor joint, the mechanical joining strength is to be predicted. The true stress - true strain curves for finite element analysis were obtained through tensile tests of HGI and DP 780 steel. The mechanical joining strength was predicted through an explicit finite element analysis and the accuracy of the predicted results was verified by actual sample test. The regression equation for predicting the mechanical joining strength to the thickness of the DP 780 steel was derived. The minimum thickness of DP 780(1.2mm), which is equivalent to the joining strength of HGI(2.6mm), was derived from the equation.

Mechanical strength of FBG sensor exposed to cyclic thermal load for structural health monitoring

  • Kim, Heonyoung;Kang, Donghoon;Kim, Dae-Hyun
    • Smart Structures and Systems
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    • v.19 no.3
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    • pp.335-340
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    • 2017
  • Fiber Bragg grating (FBG) sensors are applied to structural health monitoring (SHM) in many areas due to their unique advantages such as ease of multiplexing and capability of absolute measurement. However, they are exposed to cyclic thermal load, generally in the temperature range of $-20^{\circ}C$ to $60^{\circ}C$, in railways during a long-term SHM and the cyclic thermal load can affect the mechanical strength of FBGs. In this paper, the effects of both cyclic thermal load and the reflectivity of FBGs on the mechanical strength are investigated though tension tests of FBG specimens after they are aged in a thermal chamber with temperature changes in a range from $-20^{\circ}C$ to $60^{\circ}C$ for 300 cycles. Results from tension tests reveal that the mechanical strength of FBGs decreases about 8% as the thermal cycle increases to 100 cycles; the mechanical strength then remains steady until 300 cycles. Otherwise, the mechanical strength of FBGs with reflectivity of 6dB (70%) and 10dB (90%) exhibits degradation values of about 6% and 12%, respectively, compared to that with reflectivity of 3dB (50%) at 300 cycles. SEM photos of the Bragg grating parts also show defects that cause their strength degradation. Consequently, it should be considered that mechanical strength of FBGs can be degraded by both thermal cycles and the reflectivity if the FBGs are exposed to repetitive thermal load during a long-term SHM.

Strength Modeling of Mechanical Strength of Polyolefin Fiber Reinforced Cementitious Composites

  • Sakthievel, P.B.;Ravichandran, A.;Alagumurthi, N.
    • Journal of Construction Engineering and Project Management
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    • v.4 no.2
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    • pp.41-46
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    • 2014
  • RCC consumes large quantities of natural resources like gravel stone and steel, and there is a need to investigate on an innovative material that utilizes limited quantities of natural resources but should have good mechanical strength. This study deals with the experimental investigation of strength evaluation of cementitious composites reinforced with polyolefin fibers from 0% to 2.5% (with interval of 0.5%), namely Polyolefin Fiber Reinforced Cementitious Composites (PL-FRCC) and developing statistical regression models for compressive strength, splitting-tensile strength, flexural strength and impact strength of PL-FRCC. Paired t-tests (for each PL fiber percentage 0 to 2.5%) bring out that there is significant difference in compressive and splitting-tensile strength when curing periods (3, 7, 28 days) are varied. Also, a strong relationship exists between the compressive and flexural strength of PL-FRCC. The proposed mathematical models developed in this study will be helpful to ascertain the mechanical strength of FRCC, especially, when the fiber reinforcing index is varied.

Study on Manufacturing Characteristics of Carbonated lightweight Aggregate using Sewage Sludge (하수슬러지를 이용한 탄화경량골재의 제조 특성 연구)

  • Yoo, Yeong-Seok
    • Journal of Korean Society of Water and Wastewater
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    • v.27 no.6
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    • pp.743-750
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    • 2013
  • In this study, the carbonized aggregate of light weight and high mechanical strength using sewage sludge was evaluated with changing carbonation variables of temperature, detention time and feed condition. Porosity and mechanical strength was simultaneously increased according to increase of carbonization temperature unexpectedly. Carbonization detention time above 1 hour nearly affect on the porosity, but mainly on mechanical strength of the carbonized aggregate in case of clay addition. On $900^{\circ}C$, porosity and mechanical strength was increased rapidly, but above $1000^{\circ}C$, porosity began to decrease. Clay addition was very effective on increase of mechanical strength following much loss in porosity. The carbonized aggregate manufactured at $900^{\circ}C$ adding 30 % clay in sewage sludge was higher a little in porosity and 3 times in mechanical strength than those at $700^{\circ}C$ not adding clay. Consequently, in manufacturing the carbonized aggregate having simultaneously high porosity and mechanical strength, it is desirable to have operational condition of $900{\sim}1000^{\circ}C$ temperature and 1 hour time, and clay addition within 30 % for further higher mechanical strength.

A Study on the Optimum Joining Condition in a Mechanical Press Joint (기계적 프레스 접합의 최적접합조건에 관한 연구)

  • Lee, Yong-Bok;Kim, Tae-Yun;Jeong, Jin-Seong;Choe, Ji-Hun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.3
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    • pp.752-760
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    • 2000
  • Mechanical press joining has been used in sheet metal joining processes because of its simple process and possibility of joining dissimilar metals, such as steel and aluminum. The strength of mechanical press joining varies with joining conditions. The optimum joining conditions considering tensile-shear and peel-tension strength have to be established to assure the reliability in the joining strength. Therefore, optimization of joining conditions has been investigated for improving joining strength of sheet metal. It is possible to obtain optimum strength from improvement on the joining strength of peel-tension mechanical press joint under multiaxial stress states.

The Effect of Heat Treatment Hold Time for Mechanical Properties of Zinc-Magnesium Alloy (아연-마그네슘 합금의 열처리에 따른 기계적 특성 연구)

  • Hwang, Injoo
    • Journal of the Korean Society for Heat Treatment
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    • v.33 no.3
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    • pp.117-123
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    • 2020
  • Due to high corrosion resistance, Zinc has been widely used in the automobile, shipping or construction industries as a galvanizing material. Zinc is popular as a coating element, but its low mechanical strength impede the expansion of applications as a load-bearing structure. The mechanical strength of Zinc can be increased through zinc based alloy process, but the ductility is significantly reduced. In this study, the mechanical strength and ductility of Zinc-Magnesium alloys with respect to heat treatment hold time was investigated. In order to enhance the mechanical strength of Zinc, a Zinc-Magnesium alloy was fabricated by a melting process. The heat treatment process was performed to improve the ductility of Zinc-Magnesium alloy. The microstructure of the heat-treated alloy specimen was analyzed using SEM. The hardness and compressive strength of the specimen were measured by a micro-hardness tester and a nano-indenter, respectively.

Fire Resistance Studies on High Strength Steel Structures

  • Wang, Wei-Yong;Xia, Yue;Li, Guo-Qiang
    • International Journal of High-Rise Buildings
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    • v.7 no.4
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    • pp.287-298
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    • 2018
  • High strength steels have been widely applied in recent years due to high strength and good working performance. When subjected to fire conditions, the strength and elastic modulus of high strength steels deteriorate significantly and hence the load bearing capacity of structures reduces at elevated temperatures. The reduction factors of mechanical properties of high strength steels are quite different from mild steels. Therefore, the fire design methods deduced from mild steel structures are not applicable to high strength steel structures. In recent ten years, the first author of this paper has carried out a lot of fundamental research on fire behavior of high strength steels and structures. Summary of these research is presented in this paper, including mechanical properties of high strength steels at elevated temperature and after fire exposure, creep response of high strength steels at elevated temperature, residual stresses of welded high strength steel member after fire exposure, fire resistance of high strength steel columns, fire resistance of high strength steel beams, local buckling of high strength steel members, and residual strength of high strength steel columns after fire exposure. The results show that the mechanical properties of high strength steel in fire condition and the corresponding fire resistance of high strength steel structures are different from those of mild steel and structures, and the fire design methods recommended in current design codes are not applicable to high strength steel structures.

Enhancing mechanical and durability properties of geopolymer concrete with mineral admixture

  • Jindal, Bharat Bhushan;Singhal, Dhirendra;Sharma, Sanjay;Parveen, Parveen
    • Computers and Concrete
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    • v.21 no.3
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    • pp.345-353
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    • 2018
  • This paper approaches to improve the mechanical and durability properties of low calcium fly ash geopolymer concrete with the addition of Alccofine as a mineral admixture. The mechanical and durability performance of GPC was assessed by means of compressive strength, flexural strength, permeability, water absorption and permeable voids tests. The correlation between compressive strength and flexural strength, depth of water penetration and percentage permeable voids are also reported. Test results show that addition of Alccofine significantly improves the mechanical as well as permeation properties of low calcium fly ash geopolymer concrete. Very good correlations were noted between the depth of water penetration and compressive strength, percentage permeable voids and compressive strength as well as between compressive strength and flexural strength.

Mechanical Properties of Reinforced Concrete Slabs at Early Ages (초기재령 콘크리트 슬래브의 처짐 예측)

  • 신성우;유석형;오성진;황동규;박기홍
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.397-400
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    • 2002
  • The mechanical properties of concrete such as modulus of elasticity, bond strength and shear strength are proportional to square root of compressive strength. And compressive strength of concrete is developed rapidly at early ages. Thus the relationship between compressive strength and its mechanical properties should be verified because the mechanical properties of early age concrete and hardened concrete are different. In this study, to predict the concrete slab deflection at early ages, modulus of elasticity and effective moment of inertia(Ie) are observed and compared with experimental results.

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Thermal and Mechanical Properties of Waste Ground Nut-shell Reinforced Polyester Composites

  • Prabhakar, M.N.;Shah, Atta ur rehman;Song, Jung-Il
    • Composites Research
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    • v.28 no.3
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    • pp.118-123
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    • 2015
  • In the current study explain about the bio-based composites made by groundnut shell as reinforcement with polyester resin matrix. Groundnut shell is an abundantly available natural waste byproduct and poly ester resin is widely used to fabricate of composites for good balance of mechanical properties because it is relatively low price and ease of handling. Evaluate the mechanical properties of manufactured groundnut shell/polyester composites by varying the amounts (wt %) of groundnut shell. Particulate shell reinforced polyester composites incorporating varying amounts of groundnut shell (5, 10, 15 and 20%) were characterized for their tensile strength, flexural strength, and impact strength. The mechanical properties improved with increasing particle loading up to 15% and decreased thereafter. Increasing in strength with increased particle shell loading was attributed to increase in surface area which enhanced load transfer between the polyester matrix and ground shall particulates. Scanning electron microscopic studies have been carried out to study the morphology of the composite. Thermal studies and water absorption properties of the composites also studied in this paper.