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Cernescu2b 1,2 Politehnica'' University of Timisoara, Romania a dion@mec.upt.ro, b anghelcernescu@yahoo.com Keywords: crack length, fatigue crack rate, stress intensity factor range, overloads, crack growth retardation.
Applying fracture mechanics approach it was possible to correlate basic parameter for fatigue crack growth rate, da/dN, which represents the crack growth for one loading cycle, to the variation of stress intensity factor range, ΔK, in experiments with variable loading of constant amplitude, as presented in Fig. 2.
For the modelling and analysis of fatigue crack growth it's been used NASGRO code which calculates the fatigue crack growth rate based on a relation called "NASGRO equation" as: q C p th n K K K K K R f C dN da                                max1 1 1 1 (2) where: N - applied cycles number, a - crack lenght, R - stress ratio, ΔK - stress intensity factor range, C, n, p and q - material constant, f - function wich describes crack opening [2], ΔKth - threshold stress intensity factor range (Fig. 2), Kc - critical stress intensity factor.
According to NASGRO program data base mechanical properties of the alloy Al 2024-T3 are: - The yield strength: Rp0,2 = 365,4 MPa - The ultimate tensile strength: Rm = 455 MPa ΔKth dN da ΔK [MPa √m]   n KC dN da  K1C Region I Region II Region III [m/cycle] - Plain strain fracture toughness: KIc = 1042 MPa √mm Materials constant (C,n,p,q) for considered alloy, required in NASGRO equation, are selected based on curves da/dN = f(ΔK) (Fig. 4), given in references [6], [7], [8], [9] for different R.
Mirton, 2001 [2] ,,NASGRO - Fracture Mechanics and Fatigue Crack Growth Analysis Software'' - Reference Manual, Version 4.02, Sept. 2002 [3] Willenborg J., Engle R.M. and Wood H.A. - ,,A crack Growth Retardation Model Using an Effective Stress Concept'', AFFDL-TM-71-1-FBR, Wright Patterson Air Force Laboratory, ian. 1971 [4] Gallagher J.P., - ,,A Generalized Development of Yield Zone Models'', AFFDL-TM-74-28FBR, Wright Patterson Air Force Laboratory, ian. 1974 [5] Gallagher J.P., Hughes T.F. - ,,Influence of Yield Strength on Overload Affected Fatigue Crack Growth Behavior in 4340 Steel'', AFFDL-TM-74-27-FBR, Wright Patterson Air Force Laboratory, februarie 1974 [6] Frediani - ,, Experimental results forwarded to JSC by ESA'', University of PISA [7] Wanhill, R.

Research about Subsynchronous Oscillation caused by High-Voltage-Direct-Current Nan Zhou1,a，Guanrong Wang2,b 1,2North China Electric Power University 2 Beinong Road, Changping, Beijing 102206, P.R.China ahycp.zn@gmail.com bsinceilu@live.cn Keywords: HVDC, Subsynchronous oscillation, Unit interaction factor, Damping controller Abstract.
Research about subsynchronous oscillation problems caused by the DC transmission system involves mechanism, mathematical model and analysis method, control scheme, monitoring protection and a series of problems; we should not only consider the interaction between mechanical shaft system and power grid, but the interaction of AC-DC system, especially the DC control system and the mechanical interaction of the axis; layer upon layer associated interactions of center of the DC transmission system, AC power system, generator shaft mechanical characteristics of electromagnetic properties make it very complex.
However, research suggests that adoption of a more detailed and complex modulation function has little effect on the frequency of subsynchronous oscillation, but only affects the amplitude, so qualitative research can adopt ideal modulation function.
This method is referred to the Unit Interaction Factor (UIF) [7].
References [1] Zheng Xu, AC/DC power system dynamic behavior analysis [M], Beijing, mechanical industry publishing house, 2005 [2] Yixin Ni, Yanchun Wang, Shousun Chen, Baolin Zhang, Multimachine system caused by HVDC subsynchronous oscillation research. 1993, 13 (2): 64-71

This suggests that alloy design leading to a suitable distribution of second-phase particles can improve the properties and formability of wrought magnesium alloys.
Particular attention is paid to how this is affected by particle breakdown during deformation.
Vatne et al. [6] have proposed two factors to account for this phenomenon.
These factors play larger roles in cases where the PSN mechanism is not particularly efficient, e.g. in hot deformed alloys, where the dislocation densities are lower than in cold formed materials.
Hot compression tests suggest that high temperatures (above 300°C), strains (above 0.25) and strain rates (above 0.1/s) will lead to the presence of fine DRX grains in the deformed microstructure and therefore to improved mechanical properties and formability.

Modal participation factor is frequently used in selective modal analysis.
Since it was first proposed in 1980s, modal participation factor has become a useful tool in dynamical analysis of electric power system.
The core of the model is normal component of the force between pin and bearing because it involves shape, conditions, and material properties of the contacting bodies.
Some interesting properties of inflatable structures have been discovered through experiments and need to be explained theoretically.
Zhao, Dynamic behaviour analysis of planar mechanical systems with clearance in revolute joints using a new hybrid contact force model, International Journal of Mechanical Sciences. 54 (2012) 190-205

There are a large number of crop roots in the plow layer ,which was often affected by agricultural activities and natural factors.
The residual film also easy to block the crop seedling root growth, affecting crop seed germination and seedling growth, finally leading sprout deficiency.
Plastic film also impede the migration of soil capillary water, and has an adverse affect on soil bulk density, porosity and permeability, causing soil compaction and decline in soil fertility.
Since the accumulation of plastic film and the change of soil physical and chemical properties , root growth is retarded and crop growth was inhibited, eventually leading to production decline.
First author: Yu Fu (1989 - ) , male (Han), Shanxi, postgraduate, mainly engaged in mechanical design and manufacturing. fuyucau@126.com.

The mechanical and structural properties of the parts produced using this technique are found to be improved than those of their analogues manufactured using conventional manufacturing techniques [1-4].
Their mechanical and microstructural properties mainly affect the wide range of applications of AlSi10Mg manufactured using laser powder bed fusion techniques.
OVITO is used to visualize the MD profiles and other properties.
Sabat, Evaluation of structural and mechanical properties of high strength aluminum alloy components fabricated using laser powder bed fusion process, Journal of Laser Applications, 33 (2021), 032009
Ivanichkina, Computational study of the properties of silicon thin films on graphite.

It is deferent from plastic or wood in structure, surface property and agglutination value.
The high- frequency electric current is created by ultrasonic generator and changes into mechanical vibration by energy exchanger.
The mechanical vibration makes the welding head vibrating in 15000Hz or more.
[5]Gao Y, Chen F B, Zhao Y F: Research on Factors Affecting Quality of Ultrasonically Welded Plastic. submitted to Aerospace Materials & Technology(2006) [6]Zhou Y S, Yan Y C, Dong Z, Jiang S Q: The Welding Process and Quality in Ultrasonic Welding of Plastics Part I Analysis of Joint Melting State During Welding.

It has favourable properties such as natural whiteness, fine particle size, and non-abrasiveness and chemical stability.
The samples were sintered at the same sintering temperature of 900 °C to ensure uniform measurements taken to assess the properties.
Provis, J.L., et al., Correlating mechanical and thermal properties of sodium silicate-fly ash geopolymers.
Yan, Synthesis and mechanical properties of metakaolinite-based geopolymer.
Yeh, Sintering effects on the development of mechanical properties of fired clay ceramics.

Apart from affecting workers' lives, construction accidents directly impact project sustainability.
The damage affecting individuals can be described as a social impact, while the damage affecting finances can be described as an economic impact.
Social impact pertains to harm inflicted on individuals, whereas economic impact pertains to harm affecting the economy.
Waheed, Accidental safety factors and prevention techniques for high-rise building projects – A review, Ain Shams Eng.
Amin, Stakeholder’s perceptions on the significant factors affecting safety management implementation at construction sites, Malaysian Constr.

Unit tri-axis gear system structure The choice of the optimization objectives of the gear system in co-rotating twin screw extruder mainly is considered to two aspects: one is mechanical properties, that is all components have sufficient bending strength, surface stiffness and life for fulfilling the drive requirements, and the mechanical specifications of various parts in the gear system are well-distributed to ensure the performance; the other is economic indicator, that is minimizing gear volume and weight by reducing the distance between the centres of gear pairs in conditions of performing drive, and easy to be manufactured and utilized.
Optimization objective functions The parameters of the gear determine the mechanical properties and affect the geometric dimensioning.
The formula of contact strength safety coefficient is [10] (6) Where, is the contact fatigue limit of gear; , , , , , , , , , , K are the factors for contact fatigue strength according to the design standard; is the torque on the small gear; is the face width coefficient of the small gear; is the pitch circle diameter of the small gear.
Meanwhile, the formula of gear bend fatigue strength safety coefficients is [10] (8) Where, , , , , , , , , are the factors for bend fatigue strength according to the design standard; is the bending fatigue limit of gear root.
Mechanical property constraints Mechanical property constraints include the constraint of the contact fatigue strength and the constraint of the bending fatigue strength.